Thread: AESA Technology - Next Generation Radar

Phased Arrays and Radars – Past, Present and Future
Summarization of the recent developments and future trends in passive, active, bipolar and monolithic microwave integrated circuitry phased arrays for ground, ship, air and space applications
From: Vol. 49 No. 1 | January 2006 |
by Eli Brookner

This is a survey article summarizing the recent developments and future trends in passive, active, bipolar and monolithic microwave integrated circuitry (MMIC) phased arrays for ground, ship, air and space applications. Covered is the DD(X) ship radar suite; THAAD (formerly GBR); European COBRA; Israel BMD radar antennas; Dutch shipboard APAR; airborne US F-22, JSF and F-18 radars, European AMSAR, Swedish AESA, Japan FSX and Israel Phalcon; Iridium (66 satellites in orbit for a total of 198 antennas) and Globalstar MMIC space-borne active array systems (these last two are for communications, but the technology is the same as used by radar systems. In fact, the IRIDIUM T/R module technology derives from technology developed for a space-based radar); Thales (formerly Thomson-CSF) 4" MMIC wafer, 94 GHz seeker antenna; digital beamforming; ferroelectric row-column scanning; optical electronic scanning for communications and radar; the MMIC C- to Ku-band advanced shared aperture program (ASAP) and AMRFS antenna systems for shared use for communications, radar, electronics countermeasures (ECM) and electronic support measures (ESM); and the continuous transverse stub (CTS) voltage-variable dielectric (VVD) antenna.

Accomplishments Over the Last Two and a Half Decades

Fig. 2 Examples of passive phased arrays from around the world.

Phased arrays have come a long way in the last three decades. This is illustrated by the many tube passive arrays and solid-state active arrays, which use discrete and MMIC technologies that have been deployed or are under development.1–24,82–84,86

- Figures 1 and 2 show passive phased arrays, the first generation of phased arrays.

- Figure 3 shows Rotman lens arrays.

- Figure 4 shows active solid-state ( wiki entry - Transistor vs vacuum tube) arrays using discrete components ( wiki entry - Discrete components) , the second generation.

- Figures 5 and 6 are for phased arrays using microwave analog integrated circuits (wiki entry - MMIC), the third generation.

The numbers manufactured are shown in parentheses in the figures. Note that in some cases, very large numbers have been produced, even for MMIC active phased arrays (see Table 1). Also, one sees that phased arrays are being developed around the world. Included are the new L-band GEC-Marconi S185OM (SMARTELLO), which will provide very long range search for the SAMPSON radar on the Royal Navy Type 45 anti-air warfare (AAW) destroyer and the new AMS L-band RAT 31DL.86 The SMARTELLO uses the SMART-L antenna and elements of the Martello. The Iridium satellite system has been deployed; it consists of a constellation of 66 satellites. It was a great technological success but unfortunately not a financial one.14 It is still in operation, however. In fact, three replacement satellites were launched in 2002. Figure 7 shows additional phased arrays that have recently come under development, for which the technology is not specified. Included are the US Army’s joint land attack cruise missile defense elevated netted sensors system (JLENS), consisting of a long range 3-D surveillance radar and a high frequency precision tracking and illumination radar deployed in an aerostat; the medium extended air defense system (MEADS) UHF surveillance radar; the US Army’s multi-mission radar (MMR); UK/US airborne stand-off radar (ASTOR), the UK equivalent of the US joint STARS (JSTARS), and the US Marine Corps affordable ground-based radar (AGBR) and multiple role radar system (MRRS). Figures 8 and 9 give the state-of-the-art of GaAs MMIC power amplifiers and of GaAs and InP low noise amplifiers (LNA).85 The People’s Republic of China has come a long way in a very short time in the development of phased arrays — passive, active, over-the-horizon, dual-band, wide-band, ultra-low sidelobe, synthetic-aperture, adaptive, digital-beamforming, super-resolution and phase only null steering.76 The question addressed now is what does the future hold?

Fig. 3 Examples of ROTMAN lens arrays.

Development of MMIC Active Phased Arrays

With the recent awards of production and development contracts for MMIC active phased array contracts, such as for three THAAD EDM (engineering development model) radars, COBRA radars, SAMPSON radars, sea-based test XBR radars, forward-based BMDs radars, MEADS radars, air traffic navigation, integration and coordination system (ATNAVICS) radars, four-faced active phased-array radar (APAR) system, the new B-2 radar, multi-platform radar technology insertion program (MP-RTIP) on E-10A (upgrade of the Joint STARS), MP-RTP on Global Hawk, F-15C (AN/APG-63(V), 25 already in service), F-16, F/A-18, F/A-22 and F-35 joint strike fighter (JSF) airborne radars, the planned development contracts for the new US DD(X) ship and SPY-3/VSR radar suite, the future looks very good for MMIC radars.79,80,83 The new X-band SPY-3 under development for the DD(X) ship, the US Navy’s first active radar, is planned to be used for the detection, tracking and illumination of low flying, anti-ship, cruise missiles and is expected to consist of a three-faced radar.83 When not supporting engagement operations, it will perform horizon search, surface search and periscope detection.83 The cooperative engagement capability (CEC) is a Navy ship and communications array antenna. Figures 10 and 11 show space-based radar and digital beamforming phased-array systems that have been deployed or are under development.

Research and Development Work for Future Phased-Array Systems

Clutter Rejection for an Airborne System (STAP and DPCA)

To cope with ground clutter and sidelobe jamming for airborne radar, extensive work is ongoing toward the development of an airborne phased array using space-time adaptive processing (STAP).25,26 STAP is a general form of displaced phase center antenna (DPCA) processing. STAP had been demonstrated several years ago on a modified E2-C system by NRL.27,28 More recently, a flight demonstration STAP provided 52 to 69 dB of sidelobe clutter cancellation relative to the main beam clutter.29 This system used an array mounted on the side of an aircraft. The antenna had 11 degrees of freedom in azimuth and two in elevation, for a total of 22. Before STAP, the antenna RMS sidelobe level was -30 dBi; with STAP, it was –45 dBi.

Fig. 5 Examples of ground and shipboard MMIC active arrays deployed and under development.

C- to Ku-band Multi-user Advanced Shared Aperture Program (ASAP) MMIC Array and Dual-band AMRFS and RECAP Arrays

The COBRA DANE radar system has a 16 percent bandwidth and the Rotman lens multi-beam array systems have a 2.5 to 1 frequency bandwidth. Technology had been carried out to develop an active MMIC phase-phase steered array that has a greater than 2 to 1 frequency bandwidth and at the same time is shared by multiple users. Specifically, the Naval Air Weapons Center (NAWC) and Texas Instruments (TI, now part of Raytheon) were developing a broadband array having continuous coverage from C- through Ku-band that would share the functions of radar, passive electronic support measures (ESM), active electronic counter measures (ECM) and communications.30 To achieve this wide bandwidth, a flared notch-radiating element was used. Cross notches were used so that horizontal, vertical or circular polarization could be obtained. They built a solid-state T/R module that provides coverage over this wide band from C- to Ku-band continuously. The module had a power output of 2 to 4 W per element, a noise figure between 6.5 and 9 dB, and power efficiency between 5.5 and 10 percent, over the band. A 10 by 10-element array, having eight active T/R modules, was built for test purposes. A typical full-up array would be approximately 29" wide by 13" high. With this type of array, it would be ultimately possible to use simultaneously part of the array as radar, part of the array for ESM, part for ECM and part for communications. The parts used for each function would change dynamically, depending on the need. Also, these parts could be non-overlapping or overlapping, depending on the needs. Although the ASAP funding has ended, the shared aperture technology is now being pushed forward by the US Office of Naval Research (ONR) advanced multifunction radar frequency system (AMRFS) program71,78 and the DARPA reconfigurable aperture program [RECAP] program. DERA of the UK had been developing a dual frequency array which would enable a single radar to use L-band for search and X-band for track, so as to avoid the use of a single compromise frequency for search and track.52 Consideration is being given to the use of waveguide L-band radiating elements and dipole X-band elements.

Fig. 6 Examples of airborne MMIC active arrays deployed and under development.

Digital Beamforming and Its Potential

Table 2 lists where digital beamforming (DBF) has been operationally used, some developmental systems that have been built, and its significant advantages. The first operational radars to use digital beamforming are the over-the-horizon (OTH) radars, specifically the GE OTH-B and Raytheon relocatable OTH radar (ROTHR). The ROTHR receive antenna is approximately 8500 feet long. More recently, Signaal used digital beamforming for their deployed 3-D stacked beam SMART-L and SMART-S shipboard systems. Each row is down converted and pulse compressed with SAW lines and then analog-to-digital (A/D) converted with 12-bit, 20 MHz Analog Devices A/Ds. The signal is then modulated onto an optical signal and passed down through a fiber optic rotary joint to a digital beamformer where 14 beams are formed.31

A number of experimental DBF systems have been developed. One is the Rome Laboratory (Hanscom AFB, MA), 32 column linear array at C-band that can form 32 independent beams and uses a novel self-calibration system.32 Rome Laboratories has also developed a fast digital beamformer that utilizes a systolic processor architecture77 based on the quadratic residue number system (QRNS).32 MICOM (US Army) built a 64-element feed that used DBF for a space-fed lens.33 The experimental British MESAR S-band system does digital beamforming at the sub-array level.34 This experimental system has 16 sub-arrays and a total of 918 waveguide-radiating elements and 156 T/R solid-state modules. Roke Manor Research Ltd. of Britain has built an experimental 13-element array using digital beamforming on transmit as well as on receive.35 This experimental system uses the Plessey SP2002 chip running at a 400 MHz rate as a digital waveform generator at every element. Doing digital beamforming on transmit allows one to put nulls in the direction of an ARM threat or where there is high clutter.

Fig. 7 Other phased-array systems under development.

The National Defense Research Establishment of Sweden has built an experimental S-band antenna operating between 2.8 and 3.3 GHz, which does digital beamforming using a sampling rate of 25.8 MHz on a 19.35 MHz IF signal.23 The advantage of using IF frequency sampling rather than base band sampling is that one does not have to worry about the imbalance between the two I and Q channels, or the DC offset. They demonstrated that, by using digital beamforming, they could compensate for amplitude and phase variations that occur from element to element, across angle and across the frequency band. Via a calibration, they were able to reduce an element-to-element gain variation over angle, due to mutual coupling, from ±1 dB to approximately ±0.1 dB. Using equalization, they were also able to reduce a ±0.5 dB variation in the gain over the 5 MHz bandwidth to less than ±0.05 dB. With this calibration and equalization, they were able to demonstrate peak sidelobes 47 dB down, over a 5 MHz bandwidth. A 50 dB Chebyshev weighting was used. The RMS of the error sidelobes was down 65 dB from the peak near boresight.63 They demonstrated that the calibration was maintained fairly well over a period of two weeks. This work demonstrates the potential advantage offered by digital beamforming with respect to obtaining ultra-low antenna sidelobes. These results were not achieved in real time in the field, although that is ultimately the goal.

MIT Lincoln Laboratory developed the technology for an all-digital radar receiver for airborne surveillance array radar like that of the UHF E-2C.43 They are A/D sampling directly at UHF (~430 MHz) using a Rockwell 8-bit, 3 Gbps A/D running at room temperature. Three stages of down conversion are done digitally and because the A/D quantization noise is filtered, the effective number of bits of the A/D is increased. For example, if the signal bandwidth is only 5 MHz, the increase in signal-to-noise ratio is 3 GHz/2 (5 MHz) = 25 dB, so the increase in the number of effective bits is 25 dB divided by 6 dB/bit or 4.2 bits to yield 12 bits total. The whole digital receiver is on an 8" by 8" card that uses three 0.6 mm chips. In the future these three chips could be replaced by a single 0.35 mm CMOS chip.

Fig. 8 State-of-the-art of GaAs MMIC PAs.

The Naval Research Laboratory (NRL), MIT Lincoln Laboratory and NSWC are jointly developing an L-band active array which has an A/D converter at every element.64,65,81 Using digital beamforming, NRL demonstrated the ability to obtain a constrained beamwidth with frequency, while at the same time achieving low sidelobes over specified angles and frequency bands.66

MIT Lincoln Laboratory had been developing a high performance, low power signal processor to do digital beamforming and signal processing for a notional X-band Discoverer II space-based radar.67,68 This notional version of the system did ground moving target indication (GMTI) and synthetic aperture radar (SAR) mapping. Its antenna consisted of 12 sub-arrays and 4 SLCs. The signal bandwidth was assumed to be 180 MHz. For this system, it is necessary to do the signal processing on-board and in real time, because telemetering the signal down would require too high a data rate –35 Gbps, if a 12-bit A/D is assumed — well beyond the present state-of-the-art. The on-board signal processor must do digital beamforming, pulse compression, Doppler processing, STAP and SLC. To do this on-board and in real time requires a signal processor capable of 1100 GOPS (1.1 TERAOP). Lincoln Laboratory has shown that it is feasible to do the processing on board using a systolic array type architecture having a volume less than one seventh of a cubic foot, and weighing less than 13 kg with a power consumption less than 55 W. With the digital processing field being moved forward rapidly by the commercial world, by the year 2016 it is expected that one 9U 16" by 14.5" board would provide a throughput of 600 GFLOPS (floating OPS). It would consist of 64 chips, each providing 10 GFLOPS use a 0.07 mm technology and have a 1.25 GHz clock. Texas Instruments (TI) road map, for its TMS320 digital signal processor (DSP), indicates that by the year 2010 they expect to be able to do 3 trillion, 8-bit OPS (3 trillion instructions per second or 3 TIPS), on a single TMS320 chip.69 With 32-bit fixed-point operations, this chip would do 0.75 TIPS. Assuming 10 percent efficiency, 15 chips would do the notional Discover II processing. Such processing capability could help make the experimental Swedish ultra-low sidelobe antenna and airborne STAP array feasible.

First Generation "phased arrays" dubbed "PESA" - passive



Third Generation "Phassed Arrays" - (active). (Current)

...continued

Row-column Steered Arrays

The Naval Research Laboratory (NRL) had been developing two row-column array steering techniques, which have the potential for low cost two-dimensional steered arrays.36,37 The first technique, the one closest to possible deployment, involves using two arrays back-to-back. The first array steers the beam in azimuth, the second in elevation. The first array consists of columns of slotted waveguides, with each column having at its input one ferrite phase shifter to provide azimuth scanning. The second array is a RADANT lens array, consisting of parallel horizontal conducting plates between which are connected many diodes. The velocity of propagation of the electromagnetic signal passing through a pair of parallel plates of the array depends on the number of diodes that are on or off in the direction of propagation. By appropriately varying this number, as one goes from one pair of plates to the next in the vertical direction, one creates a gradient on the signal leaving the lens in the vertical direction so as to steer the beam in elevation. The estimated production cost of the hybrid row-column steered array is $3 million. It is possible to use two RADANT lenses to provide two-dimensional electronic scanning, one RADANT lens providing elevation scan while the second provides azimuth scan.38 Thales has developed such a RADANT antenna for the Dassault Aviation RAFALE multi-role combat aircraft.38

The second NRL row-column steered array involves using two ferroelectric lenses.37 The first lens consists of columns of ferroelectric material placed between conducting plates. A DC voltage is applied across each pair of plates. The dielectric constant of the ferroelectric material depends on the DC voltage applied between the plates. As a result the phase of the electromagnetic signal passing through a ferroelectric column will depend on this DC voltage. Consequently, by applying an appropriate DC voltage across the ferroelectric columns, one can create a phase gradient in the horizontal direction for the signal leaving the first lens and thus scan the beam in azimuth. A second such lens, rotated 90°, would steer the beam in elevation. Considerable work is still necessary before a practical ferroelectric phased array is produced. This work has been shifted from NRL to industry.

Fig. 10 Space-based phased-array systems.

The Raytheon Co. is developing a row-column steered array that employs phase shifters for steering in the H plane (see Figure 12) and a voltage variable dielectric (VVD) ceramic material used for a continuous transverse stub (CTS) antenna architecture for steering in the E plane.41 Changing the voltage across the VVD changes its dielectric constant and, in turn, the velocity of propagation along the VVD. It provides for a lightweight, low cost, small thickness antenna. They are looking to apply this technology to aircraft radar antennas and commercial antennas. Engineers and scientists have been talking about achieving electronic scanning of lasers since the 1960s. Some thought this was a pipe dream, but these doubters have since been proven wrong. Raytheon40,57 has demonstrated an electronically steered phased array for laser and optical beams. This array, which is carried around in a briefcase, represents a major breakthrough in the scanning of laser and optical beams. The scanning is achieved using a row-column scanning architecture similar to that of the ferroelectric scanner previously described, with liquid crystal used instead of the ferroelectric material. In production, the cost per phase shifter for an optical phased array is estimated to be pennies.40,57

Novel Electronically Steerable Plasma Mirror

NRL had been pursuing the development of a novel electronically steerable plasma mirror in order to provide electronic beam steering.39 Here, a plasma sheet is rotated to steer the beam in azimuth and is electronically tilted to steer the beam in elevation. Switching to different initiation points in the cathode rotates the plasma mirror. Tilting the magnetic field around the plasma tilts the plasma mirror. This is done using coils placed around the plasma. These coils are placed so as not to block the microwave signal. A 50 by 60 cm plasma mirror has been generated, for which the measured antenna patterns had sidelobes approximately 20 dB down.39

Fig. 11 Phased arrays that use digital beamforming.

95 GHz Reflect-array Using 4" MMIC Wafers

Colin38 described a very aggressive effort wherein an MMIC was taken to the point of wafer integration — 4" wafers. Specifically, Thales has built an experimental missile seeker antenna, which uses two 4" wafers.38 One wafer has the dipole elements and one bit PIN diode phase shifters printed on it. The second 4" wafer contains the driving circuits that are linked to the first through bumps. The antenna has 3000 elements. The beam width is 2° and can be steered ±45°. They have reported having obtained low sidelobes.38

Micro-electro-mechanical System (MEMS) Components

The MEMS integrated circuit mechanical switch holds the promise for a 4-bit X-band phase shifter having low loss (1.5 dB), low power consumption (1 mW) and low cost ($10 per phase shifter).70 If such a phase shifter bears fruit, it would be possible to revert back for some applications to the passive phase-phase scanned array architecture having one power amplifier feeding many low cost phase shifters. Instead of a tube, the power amplifier could be a solid-state amplifier. This could reduce the number of T/R modules needed and hence the cost of a phase-phase scanned array by a considerable amount. The MEMS technology is being funded by DARPA.70 They are looking at using MEMS in their RECAP program to obtain reconfigurable ultra-wideband antennas for multi-user applications as done with the ASAP program described above.74,75

Low Cost Phase Array for the Automobile

One tends to think of phased arrays as expensive. A low cost 77 GHz phased array has been developed for automotive intelligent cruise control radar, whose total consumer cost needs to be less than $300.72,73 Two antennas, one for transmit and one for receive, and their beamformer networks are photo-etched on a single sheet of copper clad dielectric. The antennas consist of series fed columns of patch radiators, while the beam-formers are Rotman lens, one for each array. The beams are scanned in azimuth by switching between input ports of the Rotman lens.

Conclusion

Based on the above accomplishments, ongoing developments, research and large numbers of programs that are looking to effectively use phased arrays, it is apparent that the future for phased arrays is very promising and should lead to exciting developments. Phased arrays have come a long way and can be expected to make major strides in the future. For further reading on recent developments in phased arrays around the world, the reader is referred to References 1 to 14, 40, 46, 62, 82 and 83.

Acknowledgment

The author would like to thank Doug Venture of the Raytheon Co. for his help.

More on the development of phased array over the years - http://www.ll.mit.edu/news/journal/p...hasedarray.pdf

Abstract

The Development of Phased-Array Radar Technology - Alan J. Fenn, Donald H. Temme, William P. Delaney, and William E. Courtneys Lincoln Laboratory has been involved in the development of phased-array radar technology since the late 1950s. Radar research activities have included theoretical analysis, application studies, hardware design, device fabrication, and system testing. Early phased-array research was centered on improving the national capability in phased-array radars. The Laboratory has developed several test-bed phased arrays, which have been used to demonstrate and evaluate components, beamforming techniques, calibration, and testing methodologies. The Laboratory has also contributed significantly in the area of phased-array antenna radiating elements, phase-shifter technology, solid-stateransmit-and-receive modules, and monolithic microwave integrated circuit (MMIC) technology. A number of developmental phased-array radar systems have resulted from this research, as discussed in other articles in this issue. A wide variety of processing techniques and system components have also been developed. This article provides an overview of more than forty years of this phased-array radar research activity.

Excerpts

- The Beginning

Lincoln Laboratory started working on phased-array radar development projects around 1958 in the Spe- cial Radars group of the Radio Physics division. The initial application was satellite surveillance, and the level of national interest in this work was very high after the Soviet Union’s launch of the first artificial earth satellite—Sputnik I—in 1957.
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- U.S. Air Force, foresaw that the United States would soon need the capability to detect all satellites passing over its territory. One approach to solving this surveillance problem was to build a large planar array of some five thousand UHF elements - however the nation at the time was not yet equipped with the capability to produce reliable low-cost components that would allow engineers to implement a radar with five thousand individual transmitters and receivers. The country, however, did have some big UHF
klystrons in the Millstone Hill radar transmitter (2.5-MW peak power, 100-kW average power), and klystrons such as these could be incorporated into a phased-array radar of sorts. Thus began a search of a variety of hybrid mechanically scanned and electronically scanned antenna- array configurations that would use a few of these big klystrons. Figure 1 is a drawing of the favored hybrid concept, which featured a cylindrical receiver reflector 140 ft high by 620 ft long [2].


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Thus in 1959 the Laboratory launched a broad attack on new developments in theory and hardware, and through the ensuing five years the phased-array
effort functioned very much as an intellectual open house to share insights with other researchers and as a clearinghouse to help industry try out its ideas. The Laboratory developments were chronicled in a series of yearly reports entitled “Phased-Array Radar Studies,” which were best-sellers in the array community
[3–6].


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Retrospective on the Early Years

There were several enduring values to the phased-array work in these early years. First, the Laboratory quickly became “wet all over” in this new technology of phased arrays. The work covered a broad front, including theory, hardware, experimental arrays, and systems analysis on military problems requiring phased arrays. Second, the focus on driving for the practical, low-cost, highly reliable components that would make phased arrays a viable future option helped set the appropriate tone for the national research agenda in phased arrays of that era.* Third, the Lincoln Laboratory group under the leadership of John Allen was very much an open house and a forum for industry, academic, and government workers of that day. In this fashion, the work performed at the Laboratory had an amplified impact that went well beyond the efforts of the ten or so researchers in the Laboratory phased-array radar group.
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The Ensuing Years

In subsequent years, Lincoln Laboratory made significant contributions to phased-array technology, including array-element design, phase shifters, solidstate transmit-and-receive modules, gallium-arsenide monolithic microwave integrated circuits, and array calibration and testing.

* In 1970 Lincoln Laboratory cosponsored a phased-array
symposium [11] in New York City, which brought together
many contributors to the field of phased-array technology.
The symposium covered all the major aspects of phased-array
theory, design, and manufacturing, including array-element
design, feed networks and beam-steering methods,
phase-shifter technology, solid state technology, and arraytesting
techniques. Carl Blake and Bliss L. Diamond of the
Laboratory were prominent in the organization of this significant
phased-array meeting, which assessed the state of the
art and provided a comprehensive, up-to-date source of information
on phased-array antennas.


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System aspects of the Lincoln Laboratory–designed space-based radar are described in the previously mentioned article by Muehe and Labitt in this issue. The Laboratory’s low-altitude space-based-radar concept favored monopole-type radiators that had minimum radiation in the subsatellite (nadir) direction, to reduce radar clutter and jamming. Fenn investigated this problem both theoretically and experimentally for vertically polarized monopoles [20] and for horizontally polarized loops [21]. Figure 8 shows an L-band space-based-radar phased-array antenna test bed with 96 active monopole radiating elements (resembling a bed of nails). This displacedphase- center array achieved a measured clutter



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The first fielded phased-array radar, called ESAR (Electronically Scanned Array Radar), was built by Bendix and completed in 1960 [39]. ESAR had IF analog phase shifters and an IF beamformer. This beamforming technique was bulky and required good temperature control. One of the Laboratory’s early initiatives in phased-array beam steering was the development of digital IF beam-steering techniques that emphasized smaller size and simplicity in control. This approach utilized diode-controlled digital phase shifters that switched in and out fractional wavelengths of transmission line arranged in a binary cascade and placed in each antenna channel to properly phase the elements of the radiating array.
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These phase shifters, an example of which is shownin Figure 10, were tested in an experimental linear array. They tended to have high loss (several dB) at microwave frequencies, which is certainly a drawback. Concurrently, new RF positive-intrinsic-negative (PIN) diodes used in microwave switching studies led to simpler lower-loss phase shifters. A. Uhlir of Bell Telephone Laboratories had shown theoretically how the PIN diode would be ideal for microwave switches, with a low impedance when DC-forward-biased and a high impedance when DC-reverse-biased [38]. The DC-injected carriers in a PIN diode have long lifetimes compared to an RF period, but not for an IF period. Thus, for RF frequencies, the PIN diode does not rectify but has a low impedance when flooded with DC-injected carriers and a high impedance (becoming a small capacitor) without injected carriers. Temme at Lincoln Laboratory used these PIN diodes to construct the first-ever digital-diode L-band low-loss phase shifter [5], which is shown in Figure 11. Low-loss diode phase shifters were implemented in several fielded phased-array radars used in missile detection, such as HAPDAR (Hard Point Demonstration Array Radar), AN/FPS-85, MSR (Missile Site Radar), Cobra Dane, and the S-band Cobra Judy
[4, 39–41].



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The L-band HAPDAR phased-array radar [41] was built by Sperry and was completed in 1965. The UHF AN/FPS-85 [43] phased-array radar was built by Bendix and was completed in 1968. The S-band MSR was built by Raytheon and was completed in 1969. The L-band Cobra Dane phased-array radar, located in Shemya, Alaska, for observation of Soviet missile tests, was built by Raytheon and was completed in 1976. The article in this issue entitled “Wideband Radar for Ballistic Missile Defense and Range-Doppler Imaging of Satellites,” by William W. Camp et al., describes the Cobra Dane radar in more detail. Four UHF Position and Velocity Extraction (PAVE) Phased Array Warning System (PAWS) [44] phased-array radars (all solid state) were built by Raytheon, and are still used for missile warning and space surveillance.

Phase shifter

A lower-cost ferrite material—lithium ferrite—developed by the Laboratory with the assistance of Ampex Corporation had less temperature sensitivity to the magnetization that directly controls the phase shift. The use of this material also permitted the extension of ferrite-phase-shifter operation to millimeter- wavelength frequencies [50]. A flux-drive technique, also developed by the Laboratory, enabled phase setting of phase shifters with low temperature sensitivity and five-bit accuracy without the penalty of complexity in the phase shifter and driver [51]. These ferrite-phase-shifter techniques were used in the S-band Aegis phased-array radar developed for the U.S. Navy by RCA in 1974, the C-band Patriot radar developed for the U.S. Army by Raytheon in 1975, and the X-band Joint Surveillance Target Attack Radar System (Joint STARS) developed for the U.S. Air Force by Grumman in 1988 [52]. Two prototypes of Joint STARS flew forty-nine missions in Operation Desert Storm in 1991; a Joint STARS radar surveillance image is shown in Figure 11 in the article by Muehe and Labitt in this issue


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Solid State Transmit/Receive Modules

From 1982 to 1990, Lincoln Laboratory led a joint U.S. Air Force/U.S. Navy space-based-radar trans-mit/receive-module development program. The goals of this program were to utilize monolithic microwave integrated circuits (MMIC) and gallium-arsenide digital circuitry to produce low-weight, mall-size, highly radiation resistant, highly efficient, and affordable modules that were capable of controlling signal phase accurately over the anticipated temperature range, with adequate RF-power generation, low DCpower consumption, and low-noise operation. Figure 13 illustrates the configuration of the L-band transmit/receive module. Both General Electric and Raytheon produced several versions of transmit/receive modules for this program; Figure 14 shows a General Electric module.

Lightweight L-band transmit/receive module technology developed for space-based radar applications was utilized in the Iridium commercial satellite communications system, which used phased-array antennas [53]. Gallium-arsenide MMIC transmit/receive- module technology is used in the Theater High- Altitude Area Defense (THAAD) X-band phased-array radar system [54] built by Raytheon Corporation.


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Evolution of phased array as we know it today (Solid State (Semiconductor/Integrated Circut) elements)


The Evolution of Solid State Active Elements for Phased-Array Antennas

The possibility of creating an all-solid-state realization of the phased-array concept arose in the late 1960s, notably through an initiative by Mel Vosburg of the Institute for Defense Analyses, a study and analysis center sponsored by the Department of Defense (DoD). Vosburg and Carl Blake of Lincoln Laboratory worked together in this venture. Blake had succeeded John Allen as leader of the Array Radars group in which the seminal work on phased-array theory and development had taken place during the previous decade, as described earlier in this article. With support from the U.S. Army’s ballistic-missiledefense program at the Ballistic Missile Defense Advanced Technology Center (BMDATC) of Huntsville, Alabama, development of components with this phased-array objective was initiated at Lincoln Laboratory in the 1970s. The initial focus was on arrays in
the L-band frequency range. While the earlier generation of phased arrays had been based on phasers (variable phase shifters) in conductive-tube waveguides and centralized high-power vacuum tubes, developers envisioned that array designs incorporating solid state integrated circuits would open the array concept to a wide range of important applications, which would benefit from the major advantages of these circuits, especially compact size, low weight, low cost, and high reliability.

In the 1960s the technology required for monolithic circuits had not yet sufficiently matured. The limited quality of early materials and the limitations of processing technology at the time led to poor production yields and inadequate performance of monolithic components. Hence the research effort was initially based on hybrid designs combining integrated circuits with more conventional components. Hybrid circuits were composed of discrete packaged transistors, diode phase-shifting circuits and switches, and passive components, all attached to a common ceramic substrate and connected to intervening planar circuits by means of wire bonds. Early development programs based on the hybrid-design concept, in the
late 1960s and early 1970s, were performed primarily in industrial laboratories, including those at Texas Instruments, Raytheon, RCA, Westinghouse, General Electric, and Hughes. In particular, T. Hyltin of Texas Instruments, with the support of R. Albert and W. Edwards at Wright-Patterson Air Force Base in Ohio, initiated the Molecular Electronics for Radar Applications (MERA) program to build a solid state airborne radar. In the late 1960s, under Blake’s impetus, Lincoln Laboratory established a microwave integrated-circuit facility to develop and refine the technology of preparing substrates and applying circuits and devices, mainly in the hybrid mode, to the required specifications for microwave use. Planar circuits were fabricated, on steadily improving ceramic substrate materials— principally aluminum oxide—with the most refined photolithography materials and techniques then available. With these improvements, and with U.S. Army sponsorship of a program called CAMEL by the U.S. Army’s Fort Monmouth, New Jersey, laboratory, researchers began developing a 100-element L-band (1.0 to 2.0 GHz) test array [55]. A second-generation development was the Advanced Fielded Array Radar (AFAR) at RCA in Moorestown, New Jersey, with modules produced by Westinghouse. Although AFAR was not carried to completion, the effort was valuable in demonstrating the promises and the limits of hybrid technology.


---------------------------------------------------------------------------------------------------------

...continued

GAaS MMIC Chips - Evolution of A(Active)ESA applications as we know today.

Gallium-Arsenide Monolithic Integrated Circuits The all-solid-state UHF ground-based radar called PAVE PAWS was built with hybrid technology, and it performed successfully. The designs of other military defense radars, such as the Reliable Advanced Solid State Radar (RASSR) and the Solid State Phased Array (SSPA) [56] sponsored by the U.S. Air Force, were based on similar solid-state hybrid technology. Eventually, however, researchers realized that a largescale, solid-state phased-array radar made with hybrid circuits would require a very large number of discrete components and associated wire bonds, which would lead to excessive cost and inferior reliability compared to the promise of monolithic technology. Consequently, the phased-array research effort shifted toward the development and deployment of fully integrated circuits composed of devices created on a common semiconductor substrate [57]. The substrate material recognized as most promising was gallium arsenide, principally for its characteristically high carrier mobility, and thus its suitability for high-frequency systems, specifically in the microwave (1 to 30 GHz) and millimeter-wave (30 to 300GHz) frequency ranges. The highest available frequencies, and accordingly the shortest wavelengths, are essential to form narrow beams for high resolution in target tracking, while lower frequencies, with better prospects to fulfill the requirement of high transmitter power, are favored for the associated functions of surveillance and search. In 1968, in an important development, E.W. Mehal and R.W. Wacker [58] and G.D. Vendelin et al. [59], all working at Texas Instruments, reported an early success in development of devices and circuits on gallium arsenide for microwave and millimeter-wave frequencies. Another significant advance in those years was a monolithic low-noise field-effect transistor (FET) microwave amplifier on gallium arsenide, reported by W. Bächtold et al. at the IBM laboratory in Zurich [60]. In Lincoln Laboratory, Blake and Roger W. Sudbury collaborated to advance support for the MMIC phased array. The Laboratory organized its effort for these projects by establishing a mutually complementary relationship between the Microelectronics group in the Solid State Research division, which contributed the development and refinement of materials along with device fabrication and testing, and the Experimental Systems group, which contributed the circuit designs for phased-array technology.

Success in these pioneering efforts depended on the solution of numerous interrelated problems. The potential advantages of higher microwave or millimeter-wave frequencies, suitable for the narrow-beam, high-resolution tracking function of radars, imposed stringent requirements on the quality of gallium-arsenide materials for monolithic wafers, as well as rigorous demands on the optics, metallurgy, and chemistry of the photolithography process. The semi-insulating gallium-arsenide substrate on
whose surface the epitaxial device layers are fabricated is advantageous for its electrically inert character, permitting low insertion loss and also low coupling loss between the closely spaced circuit components. This key dielectric property was confirmed in detailed measurements of complex permittivity of gallium arsenide in the range of 2.5 to 36.0 GHz by William E.
Courtney at Lincoln Laboratory [61]. These measurements showed that, when well processed, the material is in fact free of the frequency-dependent loss characteristics that some researchers had feared. As device and circuit quality improved, still higher performance of the substrate was required for electrical isolation of the devices, envisioned as densely positioned
on the semiconductor wafer, against interaction with each other. An early success in this effort, demonstrated at Lincoln Laboratory [62], was the process of passivation by means of proton bombardment, to create crystalline defects and thereby impart near-intrinsic-semiconductor properties.

Later, a simpler and less costly isolating technique, which was widely adopted, involved heavy doping of the intervening areas of the substrate to reduce carrier lifetime. The early efforts in device development at Texas Instruments led to both hybrid and monolithic circuits, including balanced mixers, Gunn-diode oscillators, and frequency multipliers for receiver applications at millimeter-wave frequencies. Following these basic advances, various research groups produced planar devices showing dramatically improved performance. Such advances at the Laboratory and in industry led to a surge of development, especially of gallium-arsenide metal-semiconductor field-effect transistors (MESFET), both in discrete form and as active devices on monolithic chips. The completely monolithic microwave amplifier chip with galliumarsenide MESFETs and matching circuits was first reported by R.S. Pengelly and J.A. Turner at Plessey Co. Ltd. in 1976 [63]; this achievement led to a rapid increase in the involvement of all the leading microwave research laboratories in further development of monolithic circuits. A presentation by Courtney et al. in 1980 [64] characterized the problems and potential of a monolithic receiver, which is central to the concept of a solid-state phased array.

The Laboratory took on an advisory role for government agencies that were supporting the new generation of phased-array design. At the same time the Laboratory continued to conduct its own research directed toward (1) the development of technology applicable to the transmit/receive module for array antennas in military systems, as well as (2) the enhancement of its own capability for innovation and consultation. There was interest in Lincoln Laboratory’s proposals for research in solid-state-circuit technology from the Very High-Speed Integrated Circuits (VHSIC) program under Sonny Maynard of the DoD. In the 1980s, major support for the development of monolithic microwave technology came through the efforts of Elliot Cohen, a DoD associate of Maynard’s and a major advocate, with Blake, of investigation into practical uses of gallium arsenide for microwave integrated circuits. Cohen sponsored the Microwave and Millimeter Wave Monolithic Integrated Circuits (MIMIC) program [65] within the Defense Advanced Research Projects Agency (DARPA).

The program was based on the concept of an “active element” phased array; i.e., an array with integrated-circuit phasers and transmit/receive capability as an integral part of each antenna element, locked to a central phase and amplitude standard. The MIMIC program maintained the impetus of the earlier developments and encouraged the microwave industry to construct the large gallium-arsenide processing facilities that exist today for the fabrication of phased-array and telecommunication modules. The MIMIC program’s objectives included development of volume production technology to produce large-diameter, high-quality substrates suitable for commercial production of MESFETs optimized for high power or for low noise; development of computer-computer- aided device and circuit design programs (a powerful discipline then still in its infancy); and proof of feasibility to show that monolithic circuits can findapplications in circuits that are suitable and affordable for wide use in military systems.

By 1990, active solid state devices at microwave frequencies were becoming ubiquitous; MMICs were routinely developed for commercial applications such as automobile instrumentation and civilian communications, and active transmit/receive modules were being utilized for large phased arrays. Gallium-arsenide MMIC transmit/receive-module technology is used in the X-band (8.0 to 12.0 GHz) theater-missile- defense phased-array radar system [54] built by Raytheon Corporation. The decade of the 1990s saw widespread application of gallium-arsenide monolithic integrated circuits in many fields, including radar, the Global Positioning System (GPS), direct-satellite- broadcast receivers, and commercial wireless telephony.


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As you can see phased array concept dates back to WW2 while utilizing mutiple emitters to create a "array" to achieve a desired antenna radiation patterns (phased). Which is the concept - multiple elements to create a certain radiation pattern. Phased Array.

However, after the event of Sputnik I in 1957, the concept of Electronically Steered Array (ESA) was born with the need to detect all satellites passing over its territory. Actually, it was a hybird between both electronic-scan/mechanical-scan. Image below (Figure 1).

Nonetheless in 1958 a huge effort was made with the first fielded phased-array radar being, ESAR (Electronically Scanned Array Radar), was built by Bendix and completed in 1960 [39].

(The L-band HAPDAR phased-array radar [41] was built by Sperry and was completed in 1965. The UHF AN/FPS-85 [43] phased-array radar was built by Bendix and was completed in 1968. The S-band MSR was built by Raytheon and was completed in 1969. The L-band Cobra Dane phased-array radar, located in Shemya, Alaska, for observation of Soviet missile tests, was built by Raytheon and was completed in 1976.)

- Figure 1 is a drawing of the favored hybrid concept, which featured a cylindrical receiver reflector 140 ft high by 620 ft long [2]. Three rotating vertical linear arrays formed multiple receive beams in elevation angle, which were mechanically scanned across the cylindrical reflector. The klystron transmitters were coupled to three horizontal linear arrays that did not use the reflector, nor did they electronically scan.

First Electronically Steerable Array Radar

1958 - Electronically Steerable Array Radar (ESAR) RADC developed the AN/FPS-46 Electronically Steerable Array Radar (ESAR). This was the first full-size pencil-beam phased-array radar system. (Prototype for the AN/APS-85)

- http://www.rl.af.mil/History/1950s/1958.html

1960 - Electronically Steerable Array Radar In November, the Electronically Steerable Array Radar (ESAR) was powered up for the first time. This radar was capable of positioning a beam in space by electronic means, eliminating the need for mechanical antenna rotation. ESAR subsequently proved useful in the development of Cobra Dane.

-http://www.rl.af.mil/History/1960s/1960.html

First Electronically Steerable Array Radar (ESAR) Installations (AN/FPS-85- http://www.globalsecurity.org/space/.../an-fps-85.htm)

These were PESA systems similar to those found in current systems such as Patriots/Aegis Burkes/JSTARS/B-1/B-2/SU Flanker/S-300PMU. (Due to 1970-80 componets they were significantly larger)



1968 - AN/APS-85 (ESAR)

Air Force Rome Air Development Center [RADC] was tasked with engineering responsibility for the development of a spacetrack radar (AN/FPS-85) and sponsored a developmental contract with the Bendix Corporation. As the initial operational application of the phased-array concept, in which a beam from several transmitters was transmitted without the movement or rotation of conventional radar, the AN/FPS-85 would be the first phased-array radar developed to track objects in space.

The Aerospace Defense Command's 14th Aerospace Force assumed operational control of the AN/FPS-85 Space Track Radar -- previously designated the Electronically Steerable Array Radar (ESAR) -- at Eglin AFB in late December 1968. This was the first phased-array radar system especially designed to detect and track objects in space. The physical structure of the system was 13 stories high, and the radar contained 5,134 transmitters and 4,660 receivers and utilized three computers.

The AN/FPS-85 covers 120 degrees in azimuth and in excess of 22,000 nautical miles in range. The transmitter array contains 5,928 transmitter antennas in a 78 x 76 square array and 5,184 transmitter modules installed in a 72 x 72 square array. The receiver array contains 19,500 receiver antennas and 4,660 receiver modules.

The AN/FPS-85 building is composed of the receiver side which is 192 feet long, 143 feet deep, and 143 feet high. The transmitter side is 126 feet long, 95 feet deep, and 95 feet high. Total floor space is 250,000 square feet, with 1,250 tons of structural steel, 1,400 cubic yards of concrete, and a total of 2,500,000 cubic feet in the building.

The AN/FPS-85 played an active role in America's space program. From 1971 to 1984, the site was home of the Alternate Space Surveillance Center. It provided computational support to the Space Surveillance Center at Cheyenne Mountain AS, CO. If the need arose, the squadron operating the AN/FPS-85could assume command and control for worldwide space track sensors. When that squadron integrated US Air Force Space Command in the early 1980's, the AN/FPS85 became the proving ground for the Air Force's phased array radars. The new technology was used in new radars specifically designed and located for early warning of SLBM attacks. These PAVE Phased Array Warning System radars assumed early warning responsibilities away from the Eglin Space Track Radar.

In 1987, the site returned to its original mission space surveillance. The site underwent a major transition, allowing Defense Department civilians to staff the majority of support and maintenance functions, while military people staffed the command section, orderly room and operations functions.





1965 - Hard Point Demonstration Array Radar (HAPDAR)



This photo shows both the construction of the HAPDAR Phased Array Radar and the Zeus Acquisition Radar (ZAR) receiver antenna (large white dome in background). The HAPDAR was installed in the building after the Zeus program closed. The photo was taken 21 April 1965.

1969 - First MSR Prototype At Kwajalein Missile Range

The first prototype MSR became operational at Meck Island at Kwajalein in September 1968 to support missile testing of the Spartan and Sprint missiles. This particular MSR was different to the operational versions in that it only two radar faces rather than four. One faced north-west while the other faced north-east.

- http://www.paineless.id.au/missiles/Radars.html



1972 - Missile Site Radar (MSR) / Missile Site Control Building (MSCB) (Element of "Safeguard" - 1969 limited ballistic missile defense system which also used nuclear tipped missiles)

Nekoma, North Dakota - The 80 foot high truncated pyramid "turret" of the MSR gave the radar its ability to see in all directions and is the only visible part of the MSCB. The MSCB underground areas held additional radar equipment and the data processing and command/control systems. The adjacent underground power plant provided the generating capacity to operate the MSR's battle management systems.

Like the PAR and RSL's, the three foot thick reinforced concrete walls of the MSCB were hardened against nuclear blast effects and shielded to neutralize the electro-magnetic pulse (EMP) produced by nuclear detonations. All critical equipment was shock mounted so that operations could continue while "buttoned up" during a nuclear attack. Each of the four phased array antennas was 13 feet in diameter and contained more than 5,000 antenna elements.Raytheon was primary contractor for the MSR radar system.

- http://srmsc.org/msr2000.html
- http://www.army.mil/cmh/books/DAHSUM/1970/chIV.htm.






1972 - Perimeter Acquisition RADAR (PAR)

The 120 foot high PAR building sits on a plain just east of the Pembina Escarpment near the hamlet of Concrete, N.D. For a time, it was the second tallest building in North Dakota. The sloping face of its immense phased array antenna pointed north to detect nuclear warheads fired by the Soviet Union or China as they passed over the north pole.

Built with 17 million pounds of steel reinforcing rods and 58,000 cubic yards of concrete, the PAR was hardened against nuclear blast effects and shielded from the effects of elctro-magnetic pulse (EMP) produced by nuclear detonations. An underground power plant located immediately west of the PAR allowed it to operate autonomously while "buttoned up" during nuclear attack. The PAR site also contained administration and housing areas.

Following deactivation of the Safeguard system in 1976, the PAR was transferred to the U.S. Air Force, which currently operates the radar as part of its space track and early warning system also known as the AN/FPQ-16 . General Electric was primary contractor for the PAR radar system.

- http://srmsc.org/par2000.html
- http://www.fas.org/spp/military/program/track/par.htm





1977- Cobra Dane (Raytheon)

The Cobra Dane radar is deployed at Eareckson Air Station in Shemya, Alaska, located on the western end of the Aleutian chain. Its close proximity to Russia allows Cobra Dane collect data on Russian intercontinental ballistic missiles (ICBMs) and submarine launched ballistic missiles (SLBMs) which are frequently fired to the Kura testing range on the Kamchatka peninsula.(1)

First deployed in 1977, the Cobra Dane is an AN/FPS-108 radar that operates in the 1215-1400 MHz band using a 29m phased array antenna. During the Cold War, its primary mission was to track Soviet ballistic missile warheads aimed at the North Pacific. At present, it is used to track and collect data on Russian ICBMs and SLBMs test launches directed toward the Kamchatka impact area and the North Pacific, although it is also capable of tracking targets in space at 40,000 km. In addition, the Cobra Dane radar is used to verify, safeguard, and monitor the reductions of nuclear arms under the Strategic Arms Reduction Treaty (START).(2)

(U) Cobra Dane is an Early Warning Radar (EWR) designed to acquire precise radar metric and signature data on developing foreign ballistic missile systems for weapons system characterization. COBRA DANE was developed in the mid 1970s and became operational in 1977.

(U) COBRA DANE generates approximately 15.4 MW of peak RF power (0.92 MW average) from 96 Traveling Wave Tube (TWT) amplifiers arranged in 12 groups of 8. This power is radiated through 15,360 active array elements, which together with 19,408 inactive elements comprise the 94.5 ft diameter array face.

(U) The system, designated AN/FPS-108, has a phased array L-Band antenna containing 15,360 radiating elements occupying 95% of the roughly 100 by 100 foot area of one face of the building housing the system. The antenna is oriented toward the west, monitoring the northern Pacific missile test areas.

- http://www.missilethreat.com/systems...ane_radar.html
- http://www.fas.org/spp/military/prog...s/cobrajud.htm
- http://www.raytheon.com/products/cobra_dane/

First All SOLID-STATE AESA Installations and Systems (Active Electronically Steerable Array Radar)

(The difference between AESA and PESA)

Note - These early systems differ from current Ground Based AESA and Airborne systems in that they used 1980's vintage solid-state discrete componets as opposed to the current GaAs MMIC (Integrated Circuts) applications.


1978 - Pave Paws/Cobra Judy Development

PAVE PAWS In January, the first 300 production models of the RADC-developed solid-state transmit/receive modules for the PAVE PAWS radar system were built.

COBRA JUDY RADC assisted the Electronic Systems Division System Program Office develop the final procurement package for COBRA JUDY, a phased array radar system to be installed on the USS Observation Island. COBRA JUDY would become operational in 1981.

- http://www.rl.af.mil/History/1970s/1978.html





1980 - AN/FPS-115 PAVE PAWS Radar

Construction of the PAVE PAWS site at Beale AFB, CA was completed in October 1979. PAVE PAWS reached initial operating capability 4 April 1980 at Otis AFB in Massachusetts, and 15 August at Beale AFB, CA. Beale AFB and Cape Cod AFS are the only two operating PAVE PAWS sites in the United States. There is a decommissioned PAVE PAWS radar site at Robins AFB, GA. This site was closed as a cost-saving measure at the end of the Cold War. There was a PAVE PAWS EWR at Eldorado AFS, Texas. This radar was dismantled and moved to Clear AFS, Alaska and is scheduled to be operational in 2001. Clear AFS, Alaska, is a Ballistic Missile Early Warning System site that is scheduled to become a PAVE PAWS site in early 2001.

The mission of the PAVE PAWS radar installations involves two activities. The first activity, surveillance, is to detect and determine attack characteristics of Intercontinental Ballistic Missiles and Sea Launched Ballistic Missiles that might penetrate the PAVE PAWS field of view. Once detected, the launched object is continuously tracked and its trajectory estimated. Any object that separates from a booster is also tracked as it approaches. The second activity, tracking, supports the USSPACECOM Space Surveillance Network, which involves the surveillance and tracking of earth satellites and identification of other space objects.

To detect objects, the radar devotes approximately half of its capabilities to generate what is called a surveillance fence. This refers to scanning at elevations between 3 and 10 degrees above horizontal over 240 degrees (the azimuth) of a 360 degree circle with the radar at the center. In the surveillance mode, the position of the beam changes within this surveillance space according to a programmed pattern, moving from one position to another within tens of microseconds. In the surveillance mode, both faces of the radar are simultaneously active. Under normal circumstances, 11 percent of the radar resource is devoted to surveillance activities. The radar is also capable of performing enhanced search where the duty cycle is increased to 18 percent with no tracking being performed.

To track objects, the radar can allocate the remainder of its capabilities to focus on particular objects or a small cluster of objects. Normally, this would take up about 7 percent of the available radar resource, for a combined surveillance and tracking duty cycle of 18 percent. This means that on average the radar is transmitting pulses only 18 percent of the time. The maximum possible use of the radar resource for combined surveillance and tracking activities is 25 percent and is the operating condition that produces the maximum possible power density.

The phased array radar incorporates nearly 3,600 small, active antenna elements coordinated by two computers. One computer is on-line at all times and the second computer will automatically take control if the first fails. The computers feed energy to the antenna units in precise, controlled patterns, allowing the radar to detect objects at very high speeds since there are no mechanical parts to limit the speed of the radar sweep. The PAVE PAWS radar can electronically change its point of focus in milliseconds, while conventional dish-shaped radar may take up to a minute to mechanically swing from one area to another.

Each of the PAVE PAWS radars is housed in a 32-meter (105-foot) high building with three sides. Two flat arrays each containing approximately 1,800 individual active radiating antenna elements transmit and receive RF signals generated by the radar. The equipment that generates the RF signals and then analyzes the reflected signals is housed inside the radar building. The two array faces are 31 meters (102 feet) wide and are tilted back 20 degrees to allow for an elevation deflection from three to 85 degrees above the horizon. The lower limit provides receiver isolation from signals returned from ground clutter and for environmental microwave radiation hazard protection of the local area.

The active portion of the array resides in a circle 22.1 meters (72.5 feet) wide in the center of the array. Each radiating element is connected to a solid-state transmit/receive module that provides 325 watts of power and a low-noise receiver to amplify the returning radar signals. The RF signals transmitted from each array face form one narrow main beam with a width of 2.2 degrees.

The radar beam consists of a series of electromagnetic pulses, the characteristics of which (pulse length, frequency) would vary depending on mission requirements. The beam is directed at elevations between 3 and 85 degrees from horizontal, covering an azimuth of 120 degrees per face, for total coverage of 240 degrees, and reach outward for approximately 3,000 nautical miles. At this extreme range, it can detect an object the size of a small automobile. Smaller objects can be detected at closer range. Software programming and redundant automatic interlocks combine to provide a triple-redundant system, which means that a simultaneous failure of three systems would be required to direct the beam outside the designated elevation and azimuth ranges.

- http://www.globalsecurity.org/space/...s/pavepaws.htm
- http://www.pavepaws.org/






1981 - Cobra Judy AN/SPQ-11

(U) The COBRA JUDY System is a deployed and operational data collection sensor that consists of an S-band phased array and an X-band dish radar. The radars are permanently mounted aboard a U.S. Navy Ship, the USNS Observation Island. The system's primary mission is to collect precise data against strategic ballistic missiles to verify several United States arms control treaties. A secondary mission is to collect data for United States missile development and theater missile defense systems testing. The system is capable of worldwide deployment.

(U) The S-band phased array consists of 12,288 active independent antenna elements. The S-band radar has a 45-degree maximum instantaneous field of view. The phased array is mounted in one face of a nearly cubical (30-foot) rotating turret that houses the transmitter, microwave circuits, and the inertial navigation unit. The S-band transmitter is composed of 16 broadband Traveling Wave Tube (TWT) power amplifiers.

(U) Data collected by COBRA JUDY is required by Congress for arms control verification. COBRA JUDY is the only radar sensor capable of collecting the metric and signature data needed for strategic missile treaty verification, as well as strategic and theater missile defense development efforts. As such, it's requirements are critical for the foreseeable future, even beyond the FYDP.

- http://www.fas.org/spp/military/prog...s/cobrajud.htm
- http://www.fas.org/irp/program/collect/cobra_judy.htm

First MMIC Applications?

1985 - Monolithic Microwave Integrated Circuit RADC demonstrated the use of monolithic microwave integrated circuit (MMIC) technology for a phased array antenna with application to MILSTAR airborne terminals. (http://www.rl.af.mil/History/1980s/1985.html)


First MMIC Airborne Radar Application (1996) - AN/APG-77 (F-22) and FSX program (Japanese F-2) followed by AN/APG-62(v2) (F-15 Eagle).

- http://www.acq.osd.mil/dsb/reports/riskofftwentytwo.pdf




FX-X Program (US-Japanese) - Taken from the GAO report of 1995 (http://www.globalsecurity.org/milita...o/gao95145.htm)

-

QUESTIONS ABOUT FS-X RADAR
REMAIN FOLLOWING 1992
SYMPOSIUM
--------------------------------------------------------

Chapter 4:1.4
Following two DOD technology visits to Japan, Commerce and DOD
sponsored a symposium on the FS-X active phased array fire control
radar in June 1992. Mitsubishi Electric Corporation (MELCO), which
is developing the radar, provided a technical overview to over 150
U.S. industry and government attendees in Washington, D.C. Reviews
of the symposium varied. U.S. government and some industry
officials said that Japanese willingness to participate in the
symposium was unprecedented and provided a possible model for future
technology exchanges. Other radar industry officials, on the other
hand, said MELCO provided very limited information about the FS-X
radar. Consequently, they were unable to adequately evaluate
Japanese radar technology.

There has been little follow-up to the symposium by either Commerce
or MELCO, although some U.S. firms have been expecting such efforts.
MELCO officials told us they had contacted several U.S. companies
about commercial applications for FS-X radar technology. When we
contacted some of these companies, however, officials said that MELCO
has been reluctant to discuss its radar technology. This is partly
because Japanese companies are generally prohibited from exporting
goods for military use. MELCO officials said this prohibition
interferes with efforts to export its modules that MELCO believes
have both commercial and military applications. Japan's Ministry of
International Trade and Industry has told MELCO it must demonstrate a
commercial application of the modules before receiving approval to
export them.

Interest in the FS-X radar among the U.S. radar companies we
contacted is mixed. Some U.S. radar industry officials told us they
would like to visit MELCO's FS-X facilities in Japan to learn more
about their radar modules.3 U.S. companies produce similar modules
and believe they could benefit from knowledge of Japanese production
methods. However, some of these companies believe U.S. radar
technology itself is more advanced and therefore they cannot learn
much from Japan. Radar experts are also uncertain about the
potential market for this technology especially since current module
costs preclude widespread commercial applications. Commerce
officials told us that a government-sponsored radar industry visit to
Japan would help resolve these questions. Such a visit occurred in
November 1994 and involved more than a dozen U.S. companies,
according to a Commerce official.

In the spring of 1994, DOD completed testing of five radar modules
the United States purchased from Japan. Appendix II describes the
U.S. testing program and module costs.

UNITED STATES IS EVALUATING
JAPANESE RADAR MODULES ALTHOUGH
POTENTIAL USES ARE UNCERTAIN
================================================== ======== Appendix II
The United States has obtained more information on the Japanese
active phased array fire control radar than any other non-derived
FS-X technology. In August 1992, DOD purchased five Japanese FS-X
radar transmit/receive modules, supporting connectors, and technical
data for testing purposes. DOD paid the then current Japan Defense
Agency/Mitsubishi Electric Corporation prototype module contract
price of $4,800 per unit and about $70,000 for technical data and
additional items required to test the modules.

Mitsubishi Electric officials reported in November 1993 that they had
reduced module unit costs to about $3,300. Mitsubishi Electric
officials would like to reduce module costs even further by
increasing the module production run to at least 20,000 units
annually. Mitsubishi Electric's cost goal is about $1,400 per unit
for the FS-X program, assuming production of 120,000 units (or enough
for about 130 aircraft). Mitsubishi Electric officials noted that
they do not expect to reach the $1,400 per module goal until 2 years
into full-rate FS-X production.

Mitsubishi Electric officials said they will pursue commercial
applications for FS-X transmit/receive modules that could reduce
module costs during FS-X production. Mitsubishi Electric officials
noted, however, that commercial applications are not practical at
this time because of the modules' high cost. Commercial applications
could include air traffic control antennas, satellite and mobile
communications, and anticollision automobile radars.

In August 1993, U.S. engineers at the Wright Laboratory Solid State
Electronics Directorate began testing the five radar modules DOD
purchased from Japan. By February 1994, the United States had
finished a complete set of verification tests for module performance.
The tests indicated that the modules perform according to
specifications and will meet Japanese FS-X radar requirements. A
U.S. engineer involved in the testing said that the performance of
Japanese modules was very good and in one area are on a par with the
best U.S. modules.

In May 1994, a U.S. radar module testing team visited Japan to
compare and verify U.S. and Japanese test results. U.S. engineers
may conduct additional tests to assess the performance of FS-X radar
modules relative to U.S. modules planned for use on the F-22
aircraft.\1 DOD was preparing a report summarizing the results of the
radar testing at the time of our review.
--------------------
1 Japan has also tested a complete FS-X radar array on the ground
and in flight aboard a specially modified Japanese C-1 electronics
testbed aircraft. Japan had not shared its radar array testing data
with the United States as of March 1994, according to a radar expert,
nor would Japanese officials permit us to observe ground-based radar
array testing during our November 1993 trip to Japan.

To fully understand the history of phased arrays it's helpful to review what lead to the development of such systems and the manner that they were then implemented.

After WW2 with the deployment of nuclear weapons and development of ICBM's in the late 1950's the need arose for a comprehensive Early Warning System that would detect and track ballistic missiles launched towards the United States. However, before the threat of ICBM's, efforts were geared towards the detection of a possible Soviet bomber attack arising from the North Artic.

Thus, as a response to the Soviet threat, activation of Air Defense Command took place March 1946 tasked with Air Defense of the Continental United States. With the threat of Soviet bombers becomming ever more clear, the USAF came up with a system in 1947 known as "the Radar fence" that would be comprised of between 350-500 radar stations and 18 control centers and was projected to cost $600 million. Since the plan clearly exceeded current budgets, a plan known as "Permanent Network" would arise, which consisted of 85 radar stations and 11 control centers, in the United States and Alaska. The cost was estimated to be about $116 million, spread over the period 1949-50. It would become operational in April 1953.

However, the USAF ended up building temporary radar networks that was known as LASHUP, using obsolescent equipment (WW2), that were set up at 44 sites in the US in 1949 and early 1950 to protect potential targets in the industrial northeast and Great Lakes areas, Washington and California. These stations received updated search radars in 1950, and during 1951 and 1952 a further 85 stations were added (Grant 1957). The Ground Observer Corps was formed in 1950 to provide visual identification of aircraft spotted by the radars. By 1957 the Corps has 350,000 volunteers in the US and 80,000 in Canada (Air Force 1957). Type of Radar below.

LASHUP

With the Soviet Union posing a potential threat, in 1946 Douglas Aircraft Company's Research and Development (RAND) Project (later to become known as the RAND Corporation) was asked by the Army Air Forces to appraise the air defense problem. While the RAND Project conducted its study, the Army Air Forces directed the ADC to draft a proposal to employ existing equipment. In October and November 1946, Lt. Gen. Stratemeyer submitted two proposals. The October proposal was a short-term plan that concentrated air defense forces in the northeast and northwest. The November proposal was a longer-term plan, calling for the use of twenty-four radars to be installed by 1949 to guard the approaches to five strategic areas that encompassed the northeast, the Chicago-Detroit area, and the three west coast cities of Seattle, San Francisco, and Leangles.

However, in testimony before the House Appropriations Committee on March 6,1947, General Spaatz suggested that the best defensive strategy was to attack the enemy bombers at their home airfields. With a defense reorganization pending that promised the creation of an independent United States Air Force, Spaatz advised the ADC commander, Lt. Gen. Stratemeyer, not to press demands. Still, planning continued and in April 1947, ADC proposed a network of 114 radars. 12

On March 27, 1948, General Spaatz, concerned about the vulnerability of the Atomic Energy Commission plant at Hanford, Washington, ordered the recently placed ADC radars at Arlington, Spokane, Neah Bay, and Hanford, Washington, and at Portland, Oregon, to begin operating on a 24 hour-a-day basis. Due to insufficient personnel and materiel resources, round-the-clock operations in the northwest proved beyond ADCs capability. Despite these problems, ADC was ordered to take AN/CPS-5 and AN/TPS-1B/1D radar sets out of storage for operation in the northeast and in Albuquerque, New Mexico. By August, radars had been placed at Twin Lights and Palermo in New Jersey, and at Montauk, New York. In September 1948, the Air Force ordered thirteen additional World War II radars to be placed in operation over an area stretching from Maine to Michigan. Along with the previously sited radars, these sets became incorporated into what became known as the Lashup system. Lashup was an appropriate name for the sys-tem as World War II vintage radar antennas were literally lashed to the top of wooden platforms. In addition to the temporary antenna towers, Quonset huts and short-term wooden structures were built to house the equipment and radar operators. 15

Still, LASHUP only represented a temporary short-term limited coverage network, while the need for a national early warning network still exsisted. The first such network would be comprised of the Permanent Network, Pinetree Line *1 (1954), Mid-Canada Line (McGill Fence), Distant Early Warning Line (DEW Line) which would make up SAGE - the Semi Automatic Ground Environment.

The first proposal proposed in 1947, dubbed Project SUPREMACY, would consist of a radar fence of 374 radar stations and 14 control centers to be built throughout the continental United States and an additional 37 stations and 4 control centers to be placed in Alaska. With immediate funding, the system would be operational by mid-1953. Under this scheme, the radar stations would report intruding aircraft to the regional control center that in turn alerted interceptor aircraft. Once the interceptor aircraft were airborne, the radar stations would assume control and vector the interceptors against the attackers. However, due to the costly deployment, Project SUPREMACY ultimately was never implemented.

It wasn't until Soviet detonation of an atomic bomb, that public support grew rampant in Air Defese. Money was made available in the FY 1950 budget to start air defense construction. In addition, Congress granted the Air Force authority to transfer money from other projects to expedite building the permanent network.

Early National Warning Network

First Permanent Network

On December 2, 1949, the Air Force directed the Army Corps of Engineers to proceed with construction of the first twenty-four radar sites on Saville's seventy-five-site list. Areas covered by these sites included northeastern, midwestern, and western metropolitan regions, and Atomic Energy Commission sites in Washington and New Mexico.

Many of these locations already had temporary radars operating as part of the Lashup system. By mid-1950, forty-four Lashup installations already were operating around the strategically important areas. Once the permanent network stations became operational, the Lashup stations would be retired. 19

Also in 1950, other steps were taken to improve the nation's air warning capabilities. The Ground Observer Corps (GOC) was reestablished. In addition, Canada and the United States agreed to extend the American radar network into Canada. Tb complete this effort, the United States cooperated in constructing, equipping, and operating some of these stations on the northern side of the U.S.-Canadian border as well as those on the southern side. This string of stations straddling the border became known as the "Pinetree Line." 20

By the late 1950s, deployment of the short-range AN/FPS-14 radar resolved the problem of detecting low-flying planes. Dozens of AN/FPS-14s and the follow-on modelAN/FPS-18s were deployed at sites between the long-range permanent and mobile radar stations. As a result of this technological improvement, the GOC was deactivated on January 31, 1959.

Building the Network

On June 25, 1950, North Korea launched an invasion of South Korea, drawing the United States into a war that would last for three years. Believing that the North Korean attack could represent the first phase of a Soviet-inspired general war, the Joint Chiefs of Staff ordered Air Force air defense forces to a special alert status. In the process of placing forces on heightened alert, the Air Force uncovered major weaknesses in the coordination of defensive units to defend the nation's airspace. As a result, an air defense command and control structure began to develop and Air Defense Identification Zones(ADIZ) were staked out along the nation's frontiers. With the establishment of ADIZ, unidentified aircraft approaching North American airspace would be interrogated by

radio. If the radio interrogation failed to identify the aircraft, the Air Force launched interceptor aircraft to identify the intruder visually. In addition, the Air Force received Army cooperation. The commander of the Army's Antiaircraft Artillery Command allowed the Air Force to take operational control of the gun batteries as part of a coordinated defense in the event of attack. 21

On July 11, 1950, the Secretary of the Air Force requested approval from the Secretary of Defense to expedite construction of the second segment of twenty-eight stations for the permanent network. Most of these stations provided additional coverage to eastern, mid-western, and western regions of the country. Receiving the Defense Secretary's approval on July 21, the Air Force directed the Corps of Engineers to proceed with construction.


The remaining twenty-three permanent network sites were approved for construction later in 1950. Located primarily in Minnesota, North Dakota, and Montana, these sites formed the American component of the Pinetree Line. In September 1950, Congress pro-vided a supplemental appropriation of $40 million to fund construction and equip the sites with the newest radars. 22

Before a closed session of the House Armed Services Committee on July 27, 1950,Continental Air Command Vice Commander General Charles T. Myers pledged that the seventy-five stations would be finished by July 1, 1951. This promise proved impossible to keep. Lack of coordination between various Air Force commands and the Army Corps of Engineers, funding problems, manpower shortages, building material and spare part shortages, as well as a strike at General Electric's radar fabrication plant all slowed progress. By the end of December 1950, the completion date for the permanent network had been set back six months. 23

As construction of the permanent network proceeded, Congressional concerns about air defense prompted a reorganization of the Air Force. On January 1, 1951, the Air Force reestablished ADC as a major command to be headquartered at Ent Air Force Base (AFB) in Colorado.


The remaining twenty-three permanent network sites were approved for construction later in 1950. Located primarily in Minnesota, North Dakota, and Montana, these sites formed the American component of the Pinetree Line. In September 1950, Congress pro-vided a supplemental appropriation of $40 million to fund construction and equip the sites with the newest radars. 22

Before a closed session of the House Armed Services Committee on July 27, 1950,Continental Air Command Vice Commander General Charles T. Myers pledged that the seventy-five stations would be finished by July 1, 1951. This promise proved impossible to keep. Lack of coordination between various Air Force commands and the Army Corps of Engineers, funding problems, manpower shortages, building material and spare part shortages, as well as a strike at General Electric's radar fabrication plant all slowed progress. By the end of December 1950, the completion date for the permanent network had been set back six months. 23

As construction of the permanent network proceeded, Congressional concerns about air defense prompted a reorganization of the Air Force. On January 1, 1951, the Air Force reestablished ADC as a major command to be headquartered at Ent Air Force Base (AFB) in Colorado.

The Debate

Even with a fully capable radar system serving as the foundation of an air defense infrastructure, the Air Force claimed the United States could stop only thirty percent of an attack, at best. However, in 1950, Dr. George E. Valley, Jr., an MIT physics professor and member of the U.S. Air Force Scientific Advisory board, led a committee that more realistically concluded that the air defense system could stop only about ten percent of an attack. The Valley Committee recommended solutions that included establishing an air defense laboratory at MIT. This laboratory would employ new technologies to improve this percentage rate. The Air Force expressed interest in establishing such a laboratory. However, resistance existed at MIT by faculty who objected to the university's continuing support of military research and development. MIT President James R. Killian convened a study group, named "Project CHARLES," to examine the laboratory proposal. In addition to agreeing that MIT should host an air defense laboratory, Project CHARLES concluded that technology existed that was capable of surmounting the air defense problem. By establishing a laboratory dedicated to air defense, MIT took on a project with a bud-get twice that of its undergraduate teaching program. The air defense laboratory at MIT eventually became known as the Lincoln Laboratory. 27

In partnership with the Air Force, Cambridge Research Laboratory, and IBM, the Lincoln Laboratory immediately began work to modify a Whirlwind computer that was being developed for the Navy's use in performing air defense command and control functions. What emerged was the AN/FSQ-7, otherwise known as Whirlwind II. In 1951, Whirlwind II was first tested by placing the computer at a control center in Cam-bridge to receive data from a long-range and several short-range radars set up on Cape Cod. Tests proved promising, but years of development still lay ahead. The key breakthrough was the development of magnetic-core memory that vastly improved the computer's reliability. When the previous electrostatic-storage-tube memory was replaced by magnetic-core memory, operating speed doubled and input speed quadrupled. More significantly, maintenance time for the core memory dropped from four hours per day to two hours per week. 28

On April 16, 1952, after receiving reports from Alaska and Maine of unidentified incoming aircraft, ADC Headquarters issued an air defense readiness alert that caused hundreds of pilots to scramble to their planes and gun crews to man their antiaircraft guns. The threat was later determined to be false. Air defense planners were forced to acknowledge limited capability to evaluate threats and respond. Telephone and teletype communications were too slow to keep an air defense commander cognizant of an evolving air battle. In the wake of the false alert, defense planners decided to reevaluate the emerging air defense system. 29

Throughout late 1952, Air Force officials and scientists vigorously debated the DEW Line proposal. Opponents feared that the United States would build a Maginot Line at the expense of SAC. The debate was internal. Neither Congress nor the American people were aware of the proposals being discussed. At the end of 1952, President Truman stepped in and signed the National Security Council (NSC) directive 139. NSC 139 directed the construction of the DEW Line. After reevaluating Soviet atomic bomb and bomber production rates, NSC 139 preparers identified 1955 as a period of maximum danger. Facing this imminent Soviet threat, defense planners considered an effective airdefense warning system to be essential. 31

However, newly elected President Dwight D. Eisenhower desired a reduction in defense spending and a change of priorities. The new administration no longer considered 1955 to be a period of maximum danger. Air defense again was scrutinized by a committee headed by Bell Telephone Laboratories president Mervin J. Kelly. While the Kelly Committee reviewed Summer Study Group recommendations, the American people became aware of the debate through congressional testimony and press coverage. On March 6, 1953, Air Force Chief of Staff General Hoyt S. Vandenberg testified before Congress against funding for defensive systems at the expense of improving American air offensive capabilities. Newspaper columnists Joseph and Stewart Alsop strongly disagreed. In their New York Herald Tribune columns, the Alsop brothers published accounts of the Summer Study Group recommendations and the subsequent deliberations portraying the Air Force, and specifically SAC, as villains suppressing technological advances. In May 1953, the Kelly Committee issued a report that seemed to vindicate both sides; both sides interpreted the report in their favor.

Not pleased with the Kelly Committee findings, Defense Secretary Charles E. Wilson appointed retired Army Lieutenant General Harold R. Bull to lead another committee. In July 1953, the Bull Committee submitted a report that supported many of the Air Force planning efforts. The report recommended construction of a sensor line across mid-Canada as a top priority. Second priority would go to building the DEW Line (if experimental tests in Alaska proved it workable); deploying an automated command and control system; building an unmanned network of short-range, low-altitude, gap-filler radars to replace the Ground Observer Corps; and implementing an improved aircraft identification system. Due to questioning by the Joint Chiefs regarding the priorities of the Bull Report, the National Security Council postponed consideration of the findings until September 1, 1953. In the wake of the Soviet explosion of a hydrogen bomb in August 1953, the National Security Council approved an amended version of the Bull report. The approval document, NSC 159/4, proved significant; the Air Force received support to proceed with the development of an air defense structure. 32

The emphasis on defense approved in NSC 159/4 seemed to contrast with the policy promulgated in late 1953 in NSC 162, a policy that became known as the "New Look." The New Look had an emphasis on massive retaliation. Yet, the two policies were complementary. Eisenhower recognized that if America was to deter war through massive retaliation, it needed air defenses to ensure the survival of its retaliation force. Thus strong air defense contributed to the credibility of the American strategy. 34

Planning went ahead for a future defensive structure. However, execution of current plans lagged due to construction and equipment procurement problems. As of late 1953, not one mobile radar station was operational and sites were still being surveyed for the second phase of mobile radars. 35

Improving Command and Control

The permanent network depended on each radar site to perform GCI functions or pass information to a nearby GCI center. For example, information gathered by North Truro Air Force Station on Cape Cod was transmitted via three dedicated land lines to the GCI center at Otis AFB, Massachusetts, and then on to the ADC Headquarters at Ent AFB, Colorado.

The facility at Otis AFB was a regional information clearinghouse that integrated the data from North Truro and other regional radar stations, Navy picket ships, and the volunteer GOC. The clearinghouse operation was labor intensive. The data had to be manually copied onto Plexiglas plotting boards. The ground controllers used this data to direct defensive fighters to their targets. It was a slow and cumbersome process, fraught with difficulties. Engagement information was passed on to command headquarters by telephone and teletype.

At Ent AFB, the information received from the regional clearinghouse was then passed on to enlisted airmen standing on scaffolds behind the world's largest Plexiglas board. Using grease pencils, these airmen etched the progress of enemy bombers onto the back of the Plexiglas board so that air defense commanders could evaluate and respond. This arrangement impeded rapid response to the air battle. 36

At the Lincoln Laboratory development continued on an automated command and control system centered around the 250-ton Whirlwind II (AN/FSQ-7) computer. Containing some 49,000 vacuum tubes, the Whirlwind II became a central component of the SAGE system. SAGE, a system of analog computer-equipped direction centers, processed information from ground radars, picket ships, early-warning aircraft, and ground observers onto a generated radarscope to create a composite picture of the emerging air battle. Gone were the Plexiglas boards and teletype reports. Having an instantaneous view of the air picture over North America, defense commanders would be able to quickly evaluate the threats and effectively deploy interceptors and missiles to meet the threat.

By 1954, with several more radars in the northeast providing data, the Cambridge control center (a prototype SAGE center) gained experience in directing F-86D interceptors against B-47 bombers performing mock raids. Still much development, research, and testing lay ahead. Bringing together long-range radar, communications, microwave electronics, and digital computer technologies required the largest research and development effort since the Manhattan Project. During its first ten years, the government spent $8billion to develop and deploy SAGE. By 1958, Lincoln Laboratory had a professional staff of 720 with an annual budget of $22.5 million, to conduct SAGE-related work. The con-tract with IBM to build sixty production models of the Whirlwind II at $30 million each provided about half of the corporation's revenues for the 1950s and exposed the corporation to technologies that it would use in the 1960s to dominate the computer industry. In the meantime, scientists and electronic engineers in the defense industry strove to install better radars and make these radars invulnerable to electronic countermeasures (ECM),commonly called jamming. 37

Improving the Radar Network

In addition to SAGE center development, Progress continued on mobile and other radar network installations. On December 6, 1954, Site M-129 at MacDill AFB, Florida, became the first mobile radar site to achieve operational status.

By the end of 1955, thirteen Phase I mobile (M-site) and one Phase II second mobile (SM-site) stations were operational. They joined seventy-five stations of the per7nanentnetwork. Along with these stations, other radar lines were constructed in Canada. The Pinetree Line, operational in 1954, straddled the United States/Canadian border and

consisted of over thirty stations. The United States paid two-thirds of the costs and pro-vided most of the manpower. North of the Pinetree Line was the Mid-Canada Line, built by the Canadian government. The Mid-Canada Line consisted of an unmanned microwave fence designed to detect flyovers.

The DEW Line began with an experimental station at Barter Island, Alaska, in early1953. During the summer, work began on an eighteen-site test line across northern Alaska and northwestern Canada. By 1954, successful tests at these stations spurred extending the line across the Canadian arctic. By the end of 1957, fifty-seven stations were completed in a very costly and challenging construction effort. 38

As the radar network expanded to the top of the North American continent, defensive planners expressed concern that the radars in operation would not be capable of detecting new high-altitude aircraft. The ANIFPS-3, a radar designed and built after World War II, could detect targets only up to 55,000 feet. In the early 1950s, technicians combined a device featuring a klystron tube with the radar to improve height-detection capability. With this device, called the GPA-27, the redesignated AN/FPS-3Aradar could detect targets at 65,000 feet. Beginning in 1956, GPA-27 kits were installed at AN/FPS-3 sites. In addition to the older radars retrofitted with the GPA-27, new sets received the device as integral equipment. Designated as the AN/FPS-20, these new radars began to perform air search duties in 1957 and continued in service through the end of the Cold War. 39

Another post-World War Il radar, the AN/CPS-6, also faced obsolescence. Rather than invest much money to slightly improve the sets' performance, the Air Force decided to replace them with the AN/FPS-7 that was being developed for the Navy by General Electric (GE). The AN/FPS-7 held promise for detecting targets up to 100,000 feet. In 1955, ADC received authorization to acquire thirty-three of these sets. Development problems delayed deployment. The first set began operating at Highlands, New Jersey, in 1959. 40

In 1955, an inter-service study group named "Project LAMPLIGHT" reported that ECM could easily blind the current radar system. The study's conclusions were confirmed a year later when SAC bombers with ECM equipment blinded the ADC radar network during a mock attack. The Air Research and Development Command accepted the LAMPLIGHT Report and began developing a frequency-diversity (FD) radar. By giving the radar operator the ability to change the frequency of the radio wave emitted from the radar antenna, scientists and electrical engineers believed they could counter enemy testing lay jamming attempts. As with SAGE, years of research, development, and ahead. 41

Gap-filler radar deployment peaked in December 1960 at 131 sites throughout the continental United States. Because the introduction of gap-filler radars alleviated the need for civilians to scan the skies for enemy bombers, the ADC disestablished the Ground Observer Corps on January 31, 1959. 42

By 1959, the three-tiered radar defense fence and the US Conus "Perm Network" were operational and would make up the National Early Warning Radar network centered around Continental Air Defense Command (CONAD) and the SAGE Command-and-Control networks. Later named NORAD in 1957.


The Semi Automatic Ground Environment (SAGE) Network, comprised of 22 Sector Direction Centers and 3 Combat Centers with each site revolving around two AN/FSQ-7 with 55,000 vacuum tubes, about 1/2 acre (2,000 m&#178 of floor space, weighed 275 tons and used up to three megawatts of power, which make up the largest computers ever built.

SAGE sites were connected to a number of tracking stations which sent in sighting reports over a teletype system connected over ordinary telephone lines. Reports were typed in by operators in a specific format, which the SAGE computers then collected and displayed on a CRT as icons. Operators at the center could select any of the "targets" on the display with a light gun, and then display additional information about the contact reported by the tracking stations. Up to 150 operators could be supported from each center.

When a target turned out to be interesting, SAGE also helped the operator to select a proper response. Reports similar to those from the radar sites kept the SAGE system up to date with information on the availability and status of various weapons and aircraft, including all airfields, BOMARC and Nike Hercules anti-aircraft missile sites. When the operator chose one of these to intercept the target, orders would automatically be sent via teletype to local controllers who would take over from there. Additional messages would also be sent to higher headquarters, as well as other SAGE centers.

A massive building program started along with continued work on the computer systems and communications, with the first groundbreaking at McChord AFB in 1957. The buildings were huge above-ground concrete bricks that were often placed near cities without the residents being aware of what they were.

The total engineering effort for SAGE was immense. Total project cost remains unknown, but estimates place it between 8 and 12 billion 1964 dollars, more than the Manhattan Project that developed the nuclear bomb SAGE defended against.

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With the development of SAGE and the deployment of Early Warning System focused was now turned on fielding a antiaircraft missile to intercept Soviet Bombers which would later be known of Nike family of missiles and be operational by 1958.

Nike Ajax

Operation

The Nike Ajax contractor, Western Electric’s Bell Telephone Laboratories, teamed with numerous subcontractors to produce 350 missile batteries for domestic and overseas deployment. The primary subcontractor, Douglas Aircraft, built 13,714 missiles at its Santa Monica plant and at the Army Ordnance Missile Plant located at Charlotte, North Carolina.


Deployment

By 1958, the Army deployed nearly 200 Nike Ajax batteries around the nation’s cities and vital military installations. Soon thereafter, the Army began gradually deactivating the Nike Ajax batteries and replacing them with the longer-range nuclear-capable Nike Hercules. The Army Air Defense Command (ARADCOM) deactivated the last Nike Ajax batteries guarding the Norfolk, Virginia, area in late 1963.

The first Nike Ajax unit deployed to an above-ground site at Fort Meade, Maryland, in March 1954, and on May 30, 1954, became fully operational on an around-the-clock combat ready status. This is the basis for the Army's celebrating May 30 as the Nike Ajax birthday. (The name was changed to Nike Ajax by DA Cir 700-22 dated 15 Nov 1956). Over the next 4 years, nearly 200 batteries were constructed around the majority of America’s major northern tier and coastal cities. In June 1958, a process of conversion to the longer range Nike Hercules missile began. Subsequently, the Nike Ajax batteries were either modified to accept the new missile or deactivated. In November 1963, Site N-63 guarding Norfolk, Virginia, was the last Nike Ajax battery to be deactivated. However, the Nike Ajax missile continued service overseas with the U.S. Army and with the military forces of America’s allies for many more years.

The Nike Ajax system was designed to supplement and then replace gun batteries deployed around the nation’s major urban areas and vital military installations. ARAACOM’s original basing strategy projected a central missile assembly point from which missiles would be taken out to prepared above-ground launch racks ringing the defended area. However, ARAACOM discarded this semimobile concept because the system needed to be ready for instantaneous action to fend off a "surprise attack." Instead, a fixed-site scheme was devised.

Due to geographical factors, the placement of Nike Ajax batteries differed at each location. In Chicago, for example, the broad expanse of Lake Michigan forced ARAACOM to erect batteries along the lakefront near the heart of the city. In planning Chicago and other area defenses, ARAACOM planners carefully examined all possible enemy aircraft approaches to ensure no gaps were left open. Initially, the planners chose fixed sites well away from the defended area and the Corps of Engineers Real Estate Offices began seeking tracts of land in rural areas. However, in late 1952, the planners determined that close-in perimeter sites would provide enhanced firepower Staggering sites between outskirt and close-in locations gave defenders a greater defense-in-depth capability. The Corps of Engineers Real Estate Offices recognized that projected acreage requirements of 119 acres per site would not be feasible in some of the urban areas selected for missile deployment. To solve this problem, design architect Leon Chatelain, Jr., devised an underground magazine configuration that cut the land requirement down to 40 acres.

Each Nike missile battery was divided into three principle areas: the administrative area, integrated fire control area (IFC), and the launch area. The administrative area was usually collocated within the IFC or launch areas. The IFC and launch areas were separated by at least 1,000 yards, often over a mile, but were within visual sight of each other. The administrative area included barracks, a mess hall, and a recreation/administration supply building. These buildings were typically one-story cinder block structures with flat roofs. The area also contained a large motor maintenance building with wash and grease racks and a fuel tank with a gasoline pump. The IEC hosted the three acquisition and tracking radars as well as the battery control trailer, radar control trailer, maintenance and spares trailer, power plant, and electric cabling system.

Nike Hercules (SAM-N-25) (MIM-14/14A/14B)

As the Nike Ajax system underwent testing during the early 1950s, the Army became concerned that the missile was incapable of stopping a massed Soviet air attack. To enhance the missile’s capabilities, the Army explored the feasibility of equipping Ajax with a nuclear warhead, but when that proved impractical, in July 1953 the service authorized development of a second generation surface-to-air missile, the Nike Hercules. As with Nike Ajax, Western Electric was the primary contractor with Bell Telephone Laboratories providing the guidance systems and Douglas Aircraft serving as the major subcontractor for the airframe.

In 1958, 5 years after the Army received approval to design and build the system. Nike Hercules stood ready to deploy from converted Nike Ajax batteries located in the New York, Philadelphia, and Chicago defense areas. However, as Nike Hercules batteries became operational, the bitter feud between the Army and Air Force over control of the nation’s air defense missile force flared anew. The Air Force opposed Nike Hercules, claiming that the Army missile duplicated the capabilities of the soon-to-be-deployed BOMARC. Eventually, both of the competing missiles systems were deployed, but the Nike Hercules would be fielded in far greater numbers over the next 6 years.

In August, the Chief of Ordnance approved an engineering study to investigate the latter option with the objective of fielding a weapon quickly at minimum cost. As a result of this study, in December the Deputy Chief of Plans and Research approved plans for the follow-on project. Two months later, in February 1953, the Army asked BTL to develop detailed proposals for a Nike "B" or Hercules. A month later, Bell and Douglas Aircraft Company representatives outlined three ground guidance systems for missile designs varying in range from 25 to 50 miles. Longer range missiles would require major revisions to facilities currently being constructed for the Nike Ajax. Soon thereafter, Nike "B" received approval from the Joint Chiefs of Staff with a 1A priority. On July 16, 1953, the Secretary of the Army formally established the Nike "B" program with the objective of obtaining a weapon that could intercept aircraft flying at 1.000 miles per hour, at an altitude of 60,000 feet, and a horizontal range of 50,000 yards.

Western Electric, BTL, and Douglas began the research and development phase and by 1955 began conducting test firings at White Sands Proving Ground, New Mexico. To build the new missile, the Nike Hercules design team simply took the components of the Ajax missile and multiplied by four. Four solid booster rockets were strapped together to push the missile into flight. Once the booster rockets fell away, four liquid-propellant driven engines would carry the warhead to the target. Unfortunately, this design, dependent on multiple systems, hindered reliability. Of the first 20 flights, 12 had to be terminated due to malfunctions. On September 30, 1955, tragedy struck at White Sands when a liquid-fueled engine undergoing static testing exploded with such force that the protective bunker sustained damage. This explosion killed one worker and injured five others. This incident convinced designers to consider a solid propellant engine for the sustainer missile. October 31, 1956, marked the first successful Nike Hercules intercept of a drone aircraft. On March 13, 1957, the first flight test using the new solid propellant sustainer engine was conducted at White Sands. During the following summer, a test called Operation Snodgrass conducted at Eglin Air Force Base, Florida, demonstrated the ability of the missile to single out a target within a formation of aircraft. By this time, the first of several Nike Ajax sites had been converted to accept the new missile.

Meanwhile, work was well under way to improve acquisition and tracking radar capabilities that would further exploit the capabilities of the Nike Hercules. The Army pushed ahead with development of a system dubbed the "Improved Hercules" that incorporated three significant improvements. First, the Improved Hercules sites were to receive the HIPAR L-band acquisition radar to detect high-speed, non-ballistic targets. The other two improvements included improving the existing Target Tracking Radar and adding a Target Ranging Radar operating on a wide-ranging frequency band designed to foil attempts at electronic counter-measures.

The potential of the Improved Hercules was demonstrated on June 3. 1960, when a Nike Hercules missile scored a direct hit on a Corporal missile in the sky over White Sands. Beginning in June 1961, Army Air Defense Command (ARADCOM) began phasing in Improved Hercules to selected batteries.

Deployment

During the course of the Cold War, the Army deployed 145 Nike Hercules batteries. Of that number, 35 were built exclusively for the new missile and 110 were converted Nike Ajax installations. With the exception of batteries in Alaska and Florida that stayed active until the late 1970s, by 1975 all Nike Hercules sites had been deactivated.

Nike Hercules was designed to use existing Nike Ajax facilities. With the greater range of the Nike Hercules allowing for wider area coverage, several Nike Ajax batteries could be permanently deactivated. In retrospect, air defense planners lamented the backfitting of Nike Hercules missiles into existing sites close to areas that were vulnerable to the new threat of Soviet ICBMs. In addition, sites located further away from target areas were desirable due to the nuclear warheads carried by the missile.

In the late 1950s early 1960s, surface-to-air missile batteries were placed for the first time around such cities as St. Louis and Kansas City and around several Strategic Air Command (SAC) bomber bases. Unlike the older sites, these batteries were placed in locations that optimized the missiles’ range and minimized the warhead damage. Nike Hercules batteries at SAC bases and in Hawaii were installed in an outdoor configuration. In Alaska, a unique above-ground shelter configuration was provided for batteries guarding Anchorage and Fairbanks. Local Corps of Engineer Districts supervised the conversion of Nike Ajax batteries and the construction of new Nike Hercules batteries.

Nike Hercules first entered service on June 30, 1958, at batteries located near New York. Philadelphia, and Chicago. The missiles remained deployed around strategically important areas within the continental United States until 1974. The Alaskan sites were deactivated in 1978 and Florida sites stood down during the following year. Although the missile left the U.S. inventory, other nations maintained the missiles in their inventories into the early 1990s and sent their soldiers to the United States to conduct live-fire exercises at Fort Bliss, Texas.

Converted sites received new radars and underwent modifications so the new missiles could be serviced and stored. Because of the larger size of the Nike Hercules, an underground magazine’s capacity was reduced to eight missiles. Thus, storage racks, launcher rails, and elevators underwent modification to accept the larger missiles. Two additional features that readily distinguished newly converted sites were the double fence and the kennels housing dogs that patrolled the perimeter between the two fences. New sites, located away from populated areas did not have to be confined in acreage. Consequently, these batteries were all above ground with missile storage and maintenance facilities located behind earthen berms. Not all sites received the complete Improved Hercules package. HIPAR radars were denied to some sites due to geographical constraints and/or to avoid duplication of radars located at adjacent sites.

Continental air defense planners envisioned that the air battle over the United States would be fought by both AirForce and Army elements. The first step was early warning. Ground-, sea- and air-based radars would see blips on their radar screens, warning them of attack. These sentries would radio or telephone this information to control centers, which in turn would relay the warning down to interceptor squadrons and antiaircraft defenses. The fighter interceptors would engage the penetrators as far from their intended targets as possible. Those enemy bombers that got through would be engaged by antiaircraft batteries that were deployed around likely, high-value targets.


However, the threat would now shift from intercepting Soviet Bombers to detecting/tracking/intercepting ICBM's and once capable systems such as National Early Warning Radars in the United States and Canada, SAGE Command-and-Control, and Nike battiers would largely become obsolete only after a few years. Thus, the development of phased array for space detection/tracking entered high gear aswell as National ABM efforts such as SafeGuard.

1960

The next decade would represent a major change from the threat of Soviet Bombers (See Bomber Gap) towards the threat of ICBM's (See Missile Gap) starting with the launch of Sputnik 1. The World's first intercontinental ballistic missile (ICBM) was operational by 1959 near Northern Russia. With a total of six launch sites. However, due to costly operation and cryogenic fuel system, it took around 20 hours piror to launch, which made it extremely vulnerable from a first strike consisting of American bombers. Aslo, due to the enormosity of these launch complexes, they were well known from American U2 flights.

Nonetheless, without the means to defend against such an attack, Americans could only hope that the threat of massive retaliation would deter the Soviet Union from launching such a strike. Early warning would be critical to prepare the nation for the initial blow and allow SAC bombers to get off the ground.

Thus, the evolution of Aerospace Defense would occur with massive projects in Early Warning Radar which would be located in Alaska, Greenland, and UK as well as development of large phased arrays which would provide early warning necessary to deter a possible Soviet attack. Once such networks were in place attention would then be shifted towards ABM systems, with the development of MSR/PAR by Raytheon dubbed "Safeguard" (Which used nuclear-tipped Nike missiles to destroy ICBM's). However, a national effort comprised of MSR/PAR and Nuclear-tipped Nike missles never evolved.

R-7 Semyorka

Thus, Ballistic Missile Early Warning System (BMEWS) evolved and was designed in the late 1950's and became operational in early 1960 at Thule, Greenland and finally Clear, Alaska, and North Yorksihre, England.

Early Warning comprised of the following by 1980. (1) BMEWS 1960, (2) ESAR Eglin AFB 1968 (1st Large Scale Array), (3) ASR/PAR for SafeGuard 1972, (4) Cobra Dane (Alaska), Pave Paws 1980 (Active Array Elements).

Ballistic Missile Early Warning System (BMEWS) System

(U) The three BMEWS radars are located at Thule Air Force Base (AFB), Greenland; Clear Air Station, Alaska; and Royal Air Force (RAF) Air Base, Fylingdales, UK.

(U) BMEWS radars operate in the UHF (420-450 MHz) frequency range. The radar missions are performed automatically under control of the mission software, which directs radar operation to detect, acquire and track missile and satellite objects of interest. The systems also processes the tracked data to classify unknown objects.


Thulse Airbase (Site I)

Thule Air Base is located 700 miles north of the Arctic Circle.

The unit is responsible for providing tactical warning and attack assessment of a ballistic missile attack against the continental United States and southern Canada. Located at the most northern US base, it would also provide attack assessment and detection in the event of a sea launched ballistic missile attack.

Clear Force Alaska (Site II)

Clear Air Force Station, Alaska (BMEWS Site II) is 40 miles north of Mount McKinley and 80 miles south of Fairbanks. It manages and operates three AN/FPS-50 detection radars (DR) that cover 120 degrees in azimuth and approximately 3000 nautical miles in range. It also supports a AN/FPS-92 tracking radar (TR).

The unit is responsible for providing tactical warning and attack assessment of a ballistic missile attack against the continental United States and southern Canada. Warning data from the unit is forwarded to the North American Aerospace Defense Command inside Cheyenne Mountain Air Force Base, Co. The squadron is also responsible for a portion of the Air Force Space Command Space Surveillance Program and assists in tracking more than 7,000 Space objects currently in Earth's orbit. Prime power at Clear Air Force station is obtained from the station's coal fired power plant, which is capable of producing 22.5 megawatts of power.

Clear AFS's detection radars (DRs) consist of transmitters, reflectors, receivers, and the Detection Radar Data Take Of f (DRDTO). The transmitters supply two 4 megawatt beams (upper and lower) of RF energy to each of the DR reflectors. The reflectors are positioned to reflect the lower beams at 3.5 degrees elevation and the upper beams at 7.0 degrees elevation. The reflectors receive target returns, which are routed to the receiver channel for amplification. The signals are then routed to the DRDTO, which performs analog to digital conversion. The signals are next processed by the mission computers and sent to forward users. The Clear AN/FPS-92 tracking radar utilizes multiple transmitters to supply 8 megawatts of RF energy to an 84 foot diameter parabolic dish antenna. Target returns are processed in much the same way as those of the detection radar.

Flylingdales (Site III)

Operational functions peculiar to this mission include:

1. Detection and reporting, as either correlated or unknown objects, of all objects passing within normal coverage.
2. Tracking of all space objects at a nominal range, selected satellites at extended ranges (low signal-to-noise (S/N) track), and special satellites to synchronous altitude and geosynchronous altitude.
3. Space Object Identification (SOI) employing Automatic Pattern Recognition and high data rate collection with selective transmission of data to the SOI center.
4. interface with Naval Space Surveillance (NAVSPASUR) for hand-off and tracking of unknown objects approaching from the north.
5. Tracking of all domestic missile and satellite launches within coverage

Fylingdales (Note "Golf" Ball radars built 1963 with the pyramid (Solid State Array) being built in 1990')

- http://www.bwcinet.com/thule/index.html
- http://www.bwcinet.com/thule/2thule.htm
- http://www.airpower.maxwell.af.mil/a...oct/meyer.html
- http://cndyorks.gn.apc.org/fdales/fdinfo.htm
- http://www.geocities.com/nategal/