Recent Developments and Future Trends in Phased Arrays Dr. Eli Brookner Raytheon Co., 528 Post Road, Sudbury, MA 01776 Tel: 978-440-4007; Fax: 978-440-3000; e-mail: [email protected]

Abstract: An update is here given of the amazing advances in phased arrays from small low cost arrays to large arrays. Now >500 A/C AESAs have been deployed with > 400,000 operational flight hours; >1.8 million T/Rs manufactured; over a million blind spot car radars manufactured; Patriot upgraded to 2012 state-of-the- art; 8 AN/TPY-2s delivered and 5 more to be built; JLENS, CJR, AN/SPY-3 and Dual Band Radar about to be deployed; DBF advancing with Australian S-band CEAFAR, which has A/D at each element, having undergone sea tests; AMDR and have undergone their initial development phase; GaN allowing 5x power for same footprint as GaAs; 3D integrated circuit digital chips in production - Moore's Law marches on; DARPA looking at developing a low cost 94 GHz array with a cost goal of $1/element; DARPA COSMOS program taking monolithic microwave integrated circuits (MMIC) to the next level allowing mixed signal integration. Figure 1 (Courtesy of Raytheon)

Keywords: Multi-mode, multi-function family of AESA radars deliver a , AESA, radar, active arrays, passive arrays, dramatic increase in warfighter capability -- including simultaneous air-to-air and air-to-ground operations, along with superior PATRIOT, JLENS, THAAD, AN/TPY-2, Cobra Judy Replacement, detection, targeting, tracking and self-protection features. CJR, AMDR, Space Fence Radar, Three-Dimensional Expeditionary Long Range Radar, 3DELRR, MPAR, NexGen, 1.3 PATRIOT UPGRADE: Dual Band Radar, SPY-3, graphene, metamaterials, The Patriot, Fig. 2a, has undergone a major upgrade. From the electromagnetic band-gap material, EBG, orbital angular tip of its nose cone to the base of its radar, designers have momentum, OAM, MEMS, FPGA, SAR, car radar, signal processing

1. PRODUCTION, UPGRADES, DEVELOPMENTS:

This paper is an update of [1-7].

1.1 T/R MODULE PRODUCTION:

Raytheon alone has produced more than 1.8 million AESA (active electronically scanned array) T/R modules to date.

1.2 AIRCRAFT AESAs USING MIMC:

Raytheon Company alone has delivered more than 500 tactical aircraft active electronically scanned array (AESA) radars for multiple platforms worldwide. These AESA include the APG- 79, APG-63(V)3 and APG-82(V)1 radars which have achieved more than 400,000 cumulative operational flight hours on F-15, F/A-18E/F and EA-18G aircraft; see Fig. 1. These Figure 2a

978-1-4673-1127-4/12/$31.00 ©2013 IEEE 43 circuits in the radar and command stations, shrinking and speeding up components. The missile’s mobile control room got a major makeover, with huge touch screens, faster computers and sleek black keyboards replacing banks of controls. In the factory brand-new machinery installed capable of installing 30,000 components an hour. In the radar, one assembly that took 435 circuit cards is now down to five. Sixteen power supplies were combined into one. Wiring that used to require 31 cables now takes 10. New advances have also made the Patriot easier to maintain. Antenna elements no longer have to be sent back to the factory for repair. They can be replaced right in the field.

1.4 AN/TPY-2: Figure 2b. (Photo Courtesy of Raytheon) Depending on the needs of the warfighter, the AN/TPY-2 radar (Fig. 3) can be deployed in two different modes. In forward- invested more than $400 million into Patriot in the last four years as part of a massive program aimed at making the Patriot air and missile defense system faster, smarter, tougher and more reliable. Miniature components (see Fig. 2b) have replaced racks of equipment. Touchscreens have replaced control panels. New machines in Raytheon’s Andover, Mass. factory are making parts lighter, stronger and longer-lasting. Engineers are now giving Patriot the ability to see further by connecting it to Raytheon’s system of radar-carrying airships, the Joint Land Attack Cruise Missile Defense Elevated Netted Sensor System, or JLENS. In April, a Patriot missile used information from a JLENS to smash a target out of the sky at a Figure 3 AN/TPY-2 (Photo Courtesy of Raytheon) test range in Utah. The Patriot also works in coordination with Based mode, the radar is positioned near hostile territory, and The Terminal High-Altitude Area Defense (THAAD) System as acquires ballistic missiles in the boost (ascent) phase of flight, part of a strong, coordinated two-tier defense system against shortly after they are launched. It then tracks and incoming theater ballistic missiles. The Patriot is the lower-tier discriminates the threat, and passes critical information and the THAAD the upper-tier. The X-band 25,000 element required by decision makers to the Command and Control AN/TPY-2 is the radar sensor for the THAAD system. Over Battle Management network. 200 Patriot systems have been deployed around the world. When the AN/TPY-2 radar is deployed in terminal mode, the With its new technology the new Patriot can take on any threat in radar’s job is to detect, acquire, track and discriminate ballistic missiles in the terminal (descent) phase of flight. The terminal- the world. It can counter emerging and evolving threats from mode AN/TPY-2 also leads the Terminal High Altitude Area SRBMs, as well as those from cruise missiles, drones, and fighter Defense ballistic missile defense system by guiding the THAAD and bomber aircraft. It has undergone more than 1,000 real- missile to intercept a threat. world flight tests, and more than 2,500 search and track tests. Eight AN/TPY-2s have been delivered to date and three more Patriot was state-of-the-art in 1982 when it was delivered into the are to be built for U.S. and two for overseas. U.S. Army inventory, and Patriot is state-of-the-art in 2012 when it was delivered to the UAE inventory. The U.S. government and other partners in the program have helped fund the 1.5 JLENS: modernization, but it was an order for new Patriot systems for the United Arab Emirates that gave designers the chance to Joint Land Attack Cruise Missile Defense Elevated Netted Sensor System (JLENS; Fig. 4) is an elevated, persistent reengineer Patriot from the ground up in late 2008. The first new GEM-T missile streaked into the sky at the White Sands Missile Range in New Mexico in August 2011, followed by a test firing of the first complete, new-production Patriot system in March 2012. The U.S. Army plans to field Patriot through 2048.

The system had already gone through several upgrades since its debut in the first Gulf War. But designers now gave the Patriot missile a faster, more accurate guidance system known as Guidance-Enhanced Missile – Tactical, or GEM-T. They rewired

44 Figure 4 Photo Courtesy of Raytheon over-the-horizon aerostat sensor system. It uses a powerful integrated radar system to detect, track and target a variety of threats. This capability better enables commanders to defend against threats including hostile cruise missiles; low-flying manned and unmanned aircraft; and moving surface vehicles such as boats, automobiles and trucks; and to provide ascent- phase detection of tactical ballistic missiles and large caliber rockets.

∙ A JLENS system, referred to as an orbit, consists of two tethered, 74-meter helium filled aerostats connected to mobile mooring stations and communications and processing groups. JLENS aerostats fly as high as 10,000 feet and can remain aloft and operational for up to 30 days.

∙ One aerostat carries surveillance radar with 360-degree Figure 5 Photo Courtesy of Raytheon surveillance capability; the other aerostat carries fire control radar.

∙ According to research conducted by the U.S. Army's JLENS Product office, the cost of operating large, fixed-wing surveillance aircraft is 5-7 times greater than the cost of operating JLENS.

∙ The JLENS surveillance radar can simultaneously track hundreds of threats; the fire control radar can simultaneously target dozens of threats. "JLENS' TBMD capability gives combatant commanders another tool they can use to help protect the U.S., deployed forces, our allies and friends from the growing ballistic missile threat," said Dean Barten, the U.S. Army's JLENS program manager. "JLENS' TBMD capability, when coupled with its ability to conduct 360-degree long-range surveillance capability and simultaneously detect and engage threats like swarming boats and anti-ship cruise missiles from up to 340 miles away, gives commanders a powerful proven capability."

As indicated above JLENS has been connected to Patriot to give it the ability to see further. JLENS demonstrated tactical ballistic missile defense (TBMD) Fig. 5b CJR Team celebrate a successful first live-launch. capability when it detected and tracked a total of four ballistic- missile surrogates on their ascent (boost) phase during tests at the White Sands Missile Range, N.M., Feb. 19, 2013. As a result enemy tactical ballistic missiles will soon be easier to detect and It surpassed expectations during its first tests against a live track. Along with other X-Band radars, JLENS can provide a rocket launch on March 19. From approximately 100 miles off robust early warning and tracking capability against ballistic the Florida coast, the powerful X- and S-band radars integrated missiles. This TBMD demonstration and JLENS' other recent successes prove that the system is ready to deploy for a onboard the USNS Howard O. Lorenzen (T-AGM 25) combatant commander operational evaluation. JLENS successfully acquired and tracked both stages of an Atlas V demonstrated its capability against cruise missiles when it rocket launched from Cape Canaveral and collected all enabled Patriot and Standard Missile-6 intercepts of cruise- associated data. Raytheon is the prime contractor for the CJR missile surrogates during separate tests. JLENS also completed mission equipment and principal on an industry team that two developmental tests and demonstrated its ability to stay aloft for long durations. The JLENS will be first deployed over includes Northrop Grumman Electronic Systems. The team has Washington, DC. been a model of collaboration, focused on the delivery of a high- performing shipboard radar capability that the U.S. Navy, the

U.S. Air Force and the nation can rely upon as a critical global 1.6 CJR: asset.

The Cobra Judy Replacement (CJR) system is complete and This live-launch exercise follows a series of achievements for this undergoing tests; see Figs. 5a and 5b. true dual-band, active phased-array radar suite. Since at-sea

45 testing began in July 2012, the program team has been incrementally testing and fine-tuning the radars against targets of increasing complexity. In late 2012, two critical firsts were achieved: the demonstration of full-power radiation capability of the high-sensitivity shipboard X- and S-band radars; and the successful dual-band acquisition and tracking of satellites under the control of the CJR common radar suite controller.

Integrated onboard this complex, mission-critical platform, the massive X- and S-band active phased-array antennas of CJR are each approximately four stories tall and weigh more than 500,000 pounds. Raytheon completed the shipboard installation of CJR mission equipment at Kiewit Offshore Services, Corpus Christi, Texas, in October 2011, ahead of plan. The mission of the CJR Figure 7 program is to provide the government with long-loiter ballistic missile data collection capability in support of international treaty verification. CJR replaces the original Cobra Judy, USNS Zumwalt Class Destroyer ships and has completed ground Observation Island, also developed by Raytheon and in service testing [8, 9]; see Fig. 7. The USA Dual Band Radar (DBR) is to since 1981. CJR is planned to enter service in January 2014; the be deployed on the CVN-78 Gerald R. Ford – Class aircraft U.S. Navy will take delivery of CJR and transfer to the U.S. Air carrier [8]; see Fig. 8. The DBR integrates S-band and X-band Force for operational ownership.

1.7 DUAL BAND RADAR, SPY-3, VSR, ZUMWALT:

The SPY-3 was installed and tested at sea on a decommissioned US Paul F. Foster (DD964) destroyer Self Defense Test Ship (SDTS) for sea tests [8]; see Fig. 6. The SPY-3, the first USA Navy active array radar, is now intended for the DDG-1000

Figure 8

Radar capabilities in a single system. It delivers true multi function performance, simultaneously supporting self- defense/anti-air warfare, situational awareness, land attack, naval gunfire support, surface search, navigation and air traffic control. The S-band Volume Search Radar (VSR) is used for air surveillance and air traffic control. The X-band SPY-3 is used for horizon search, periscope detection, navigation, fire control and target illumination. The DBR’s innovative software design allows automatic operation with minimal human intervention.

The Zumwalt is constructed of rugged, lightweight composites. Figure 6 Its angular deckhouse increases stealth by minimizing radar reflectance. The surfaces of the Zumwalt’s deckhouse

incorporate all radar apertures and communication antennas, eliminating high-profile masts and rotating antennas. The

46 Zumwalt Destroyer is often called an all-electric ship. The scalability and modularity will take advantage of SPY-1's efficient, quiet and economical design of the IPS generates all current physical space in the near term, while growing to meet the energy needed for propulsion, electronics, combat, capability needs in the future as threats evolve; see Fig. 10. The environmental and other ship systems. The tumblehome system reduces space weight, power and cooling demands (inward sloping) hull minimizes the Zumwalt-class destroyer’s radar cross section for enhanced stealth and survivability. Driven by a quiet and efficient all-electric propulsion system, the hull design optimizes speed, maneuverability and stability while minimizing engine noise and infrared signatures. The Wave Piercing Tumblehome Hull is the responsibility of Northrop Grumman. Construction of the 15,000-ton, 610-foot long ZUMWALT (DDG 1000) ship is about 80 percent complete in Bath, Maine, at the Bath Iron Works shipyard of General Dynamics. It is the biggest destroyer ever built — larger, even, than most cruisers.

1.8 OTHER PROGRAMS:

Lockheed Martin S-band EQ-36 mortar artillery radar has gone into production. The Northrop-Grumman GATOR S- band Marine air defense radar has been developed. Figure 10 2. NEW PHASED ARRAY PROGRAMS:

2.1 AMDR on the ship platform, preserving maximum ship service life and The USA is providing innovative, affordable and breakthrough allowing forward/backfit of AMDR on Arleigh Burke-class capabilities to the U.S. Navy's Arleigh Burke-class destroyers destroyers. (DDG 51) with the Air and Missile Defense Radar (AMDR). The program is currently in the technology demonstration 2.2 SPACE FENCE phase. It will provide unprecedented capabilities for the U.S. Navy. It consists of an S-band radar, an X-band radar, and a In Feb. 2011 Raytheon was awarded a $107 million U.S. Air Force contract to further the design of the Space Fence system. radar suite controller, and significantly increases detection Under this contract, Raytheon is to deliver a preliminary range and adds powerful discrimination accuracy; see Fig, 9. design and test a functional radar prototype to ensure cost and This capability is greater than the SPY-1D (V) generation schedule certainty and technical maturity of the final design in support of Milestone B. The upgraded Space Fence system will replace the U.S. Air Force's Space Surveillance System radar that has been operational since 1961. The upgraded Space Fence will consist of up to three S-band large phased array radars capable of detecting more and much smaller objects in low Earth orbit to provide greater accuracy and timeliness to meet space situational awareness requirements. It will track more than 150,000 pieces of unaccounted space debris that threaten manned space flight and the satellites we all rely on for many critical services, including accurate weather forecasts, navigation and financial transactions.

 A piece of debris as small as 1 centimeter can seriously damage – or even destroy – an operational satellite.

 Critical infrastructures such as power grids, banking Figure 9 operations and transportation systems are all dependent on the GPS satellite constellation. of radars presently deployed on surface combatants and will help naval forces to more quickly detect and respond to Contract also awarded to Lockheed Martin. airborne and ballistic missile threats. This allows the defended area surrounding naval battle groups to be expanded. 2.3 THREE-DIMENSIONAL EXPEDITIONARY LONG RANGE RADAR (3DELRR): The AMDR advantage is that it is the most scalable and technologically advanced radar system, meeting the Navy's “The Three-Dimensional Expeditionary Long-Range Radar future mission requirements across multiple ship platforms. In (3DELRR) is required to replace the AN/TPS-75 radar as the addition to providing whole life cost reductions, AMDR's principal USAF long-range, ground-based sensor for detecting,

47 identifying, tracking, and reporting aircraft and missiles in being developed with the help of MA/COM under contract from support of the Joint Forces Air Component Commander through MIT LL. When doing the en-route mission the antenna for each the Ground Theater Air Control System. The primary mission of face would be 8 m in diameter, have about 24,000 elements and the 3DELRR will be to provide long-range surveillance, control T/Rs, 1o beam, dual polarization, peak power of 8 W per of aircraft, and theater ballistic missile detection. The 3DELRR polarization, 8% duty cycle, operate at 2.7-2.9 GHz. The system will provide air controllers with a precise, real-time air picture of uses multiple beams for search to minimize occupancy. To keep sufficient quality to conduct close control of individual aircraft the grating lobes down overlapped subarrays are used with 2 under a wide range of environmental and operational conditions. panels forming one overlapped subarray [12]. The terminal In the case of theater missile defense operations, the new radar radars would use the same panels but have half the diameter. will have the capability to detect, track, and disseminate target MIT LL is planning to have a 10 panel array of 640 elements by information to respective command and control nodes such as the FY 2014 and a full scale terminal array of 5,632 elements by FY USAF Control and Reporting Center to disseminate for warning 2017. and engagement. Similarly, the joint targeting process will benefit from trajectory information provided by the 3DELRR, The weather requirements are the most difficult to meet [13, 14]. which will include launch and impact location. The 3DELRR will Specifically the requirement to measure HH/VV to within 0.1 db correct current radar system shortfalls by providing the for Z ≤ 1 db, where Z is what meterorologists like to use for capability to detect and report highly maneuverable, small radar weather backscatter instead of the backscatter coefficient ɳ in cross section targets as well as discriminate the type of a non- m2/m3 used by the radar community [15-17]. Z of 1 db cooperative aircraft. It will also mitigate most of the corresponds to a fog or cloud [16, 17]. To make this measurement sustainability and maintainability concerns which plague the with the present NEXRAD S-band dish system, H and V are current system.” [Quote from FOB.gov solicitation, Ref. 10.] Air transmitted simultaneously to generate a slant polarization and Force's awarded Aug. 2012 $35 million the H and V are received simultaneously [14]. This is called contract for 3DELRR Pre-Engineering, Manufacturing and simultaneous HV or SHV. To achieve the 0.1 db HH/VV requires Technology Development phase. Contracts also awarded to that the cross polarization be down like 45 db. This is a challenge Lockheed Martin and Sensors and Northrop Grumman. for a phased array when scanning out of the principal planes. The meteorologists have come up with clever ways to get around this problem. One is to split the transmitted pulse into two 2.4 FAA/NSWRC/NOAA MULTIFUNCTION PHASED ARRAY st RADAR (MPAR) NEXGEN: contiguous pulses with the 1 having one modulation and transmitted as H and the 2nd having an orthogonal modulation and transmitted as V [18]. Both H and V are then received NexGen involves the future replacement of the USA 554 ATC simultaneously. If the isolation after pulse compression between terminal and en-route radars and weather radars (TDWR and these orthogonal signals is 20 db, then the polarization isolation NEXRAD) radars with about 370 S-band active phased array requirement is relaxed to 25 db. We will call this Split-Pulse SHV radars wherein some of these radars, those located at large or SP-SHV. airports, would be doing all four radar functions of terminal and en-route ATC and TDWR and NEXRAD weather functions. Two A second solution is to alternately transmit on successive pulse types of phased arrays are candidates – a 4-faced phased array repetition intervals H and V and only receive H after and a cylindrical phased array. Both would be scalable with large transmitting H and V after transmitting V [14]. This called ones used for en-route and smaller ones used for terminal. MIT Alternate HV or AHV. Here one gets half the isolation on Lincoln Laboratory (LL) is funded to develop an active array for transmit and half on receive. So with 22.5 db polarization a 4-faced phased array that uses 8x8 element panels as buildings isolation one achieves a total of 45 db. Specifically when blocks; see Fig. 11 [11, 12]. They are projecting a cost of $25 per transmitting H a cross polarization of 22.5 db is in the cross T/R module and $100 per element for the rest of the array polarization channel of V and when reflected from a sphere this antenna for a total of $125 per element [11, 12]. The array is becomes in the receiver a cross polarizarion signal in the H channel which is another 22.5 db down or 45 db down.

A third alternative is to use an electric dipole and magnetic dipole lined up with each other at every element to generate the V and H polarizations [14]. Think of the electric dipole aligned vertically at the center of a sphere in the north-south direction of the sphere. Then its E fields will be parallel to the longitudinal lines on the sphere. If the magnetic dipole is parallel to the electric dipole then its E field will be parallel to the meridians of the sphere and hence always perpendicular to the electric dipole E field lines which are along the longitudinal lines. The magnetic dipole can be formed from a slot in a waveguide [14]. In contrast standardly the V and H fields could be formed by two crosses dipoles. Think of each of these two dipoles at the center of a sphere with one oriented vertically and the other horizontal. For the latter standard case think of each having its own north-south direction and its own set of longitudinal lines on the sphere. In this case each generates E fields parallel to their own longitudinal lines on the sphere. But these longitudinal lines are not Figure 11 One 8x8 panel perpendicular excepted along the principal planes of scan. Hence

48 the problem with achieving good isolation for scans out of the 3.3 VERY LOW COST ARRAYS: principal planes of such an array. The Valeo (formerly Valeo Raytheon) 24 GHz car blind spot A 4th alternative is to use a cylindrical array and commutate the phased array radar using 7 beams has and costing only $100’s active part of the cylinder so that the beam is always normal to has reached sales of over 1 million; see Fig. 13. the active part of the cylinder and thus always in the principal plane in which case the cross polarization signal is always zero, theoretically [14, 19].

3. LOW COST TECHNOLOGY:

3.1 DARPA $1/ELEMENT 94 GHZ ARRAY:

DARPA is funding a program for the development of a 94 GHz 0.3 m diameter, 28,000 element active array radar that could potentially cost $1/element; see Fig. 12 [20].

Figure 13

MIT in conjunction with Lincoln Lab engineers had a course for the building of an S-band SAR radar for $360. It used two coffee cans for the transmit and receive antennas. Fig. 14 shows the amazing image obtained by moving the radar along a hobby horse [21, 22]. They also have a course for building of an 8 element, 2.4 GHz phased array costing $950 [23]. It used L-Com Wi-Fi flat patch antennas. Figure 12

3.2 COTS:

Many are looking into the use of commercial-off-the shelf technology (COTS) components like COTS printed circuit boards (PCBs). Examples are the MIT LL MPAR array shown in Fig. 11 above. Other examples are in [24-26]. Wireless COTS components are also being used [27]. Plastic packaging is used in the MPAR array and in [27].

DARPA is planning to fund a program Arrays at Commercial Timescale (ACT) whose spirit is to apply more COTS to lower the cost of future array systems. ACTS has three enabling thrust areas: 1) realization of a common hardware module that can be broadly applied to many disparate array functions, 2) development of a reconfigurable electromagnetic interface capable of supporting a wide variety of parameters such as different polarizations, frequencies, bandwidths, etc. and 3) demonstration of a scalable infrastructure in which arrays on physically disconnected platforms can be coherently combined into a larger effective aperture through the use of precise timing Figure 14 and localization data.

49

4. DIGITAL BEAMFORMING:

DBF has been making major strides over recent years. The Australian S-band 6-faced ship board CEAFAR radar which has an A/D at the element level has been undergoing sea tests [1]. DBF is done at the subarray for the MIT LL MPAR mentioned above in Sec. 2.4. MIT LL and AFRL in Dayton, OH, have been jointly developing hardware for an A/D at every element for X- band [35]. It has an instantaneous bandwidth of 600 MHz and uses SiGe down converters and two IF frequencies: S- and L- band. DBF at the element and subarray level is being looked for the up to over 100,000 element radio telescope 500-1500 MHz Square Kilometer Phased Array [36]. It is being considered for future geodesic dome multibeam phased arrays to be used for satellite command and control [37]. FPGAs to be used for DBF at the subarray level.

Figure 15 5. TECHNOLOGY

5.1 GaN: 5.5 INTEL 3D TRANSISTORS:

GaN power amplifier (PA) chip can replace a GaAs PA chip Intel 3-D transistors in mass-production. 37% faster or half the providing 5x the power in the same footprint thus providing power consumption. With 2-D 4.87million transistors/mm2 now greater sensitivity and range for radar [28]. Raytheon is pursuing with 3-D → 8.75million/mm2 → 30million/mm2 by 2017 [30]. the use of GaN on several large programs that include GaN, such Moore’s Law marches forward. Because of this exponential as Space Fence and AMDR, and also the Air Force's Three growth in computer power R. Kurzweil predicts that by the year Dimensional Expeditionary Long Range Radar (3DELRR) 2045 we will have advanced to the point that we could live program. forever, we will reach ‘singularity’ as he calls it [44].

5.2 FPGAs: 5.6 EXTREME COMPUTING:

FPGAs are used extensively throughout radar systems. We have DARPA is funding a program aimed at lowering the power come a long way from when TRW introduced the first multipliers required in signal and data processing by 100 to 1000 by 2018. It on a chip which back in 1977 used 5 W to do a 16X16 multiply at is called the Ubiquitous High Performance Computing (UHPC) 4.3 MHz clock rate. Now one FPGA can have 4,000 18X18 program. Would enable 100 GFlops throughput rate in a future multipliers operating at a 600 MHz clock rate and require only 8 smart cell phone using only 2 W instead of the 600 W that would W [28a]. An improvement of 350,000 in 26 years. Incredible. be required with today’s technology.

5.3 MEMS [42]: 5.7 COOLING:

Now MEMS 4-bit phase shifter has 1.8 db loss at 21 GHz, 2.1 db Carbon nanotubes and diamonds being looked at for chip cooling at 30 GHz, 2.6 db at 35 GHz and can be switched 300 billion [32]. It has been found that some materials can be cooled from cycles without failure. Can be used to make a tunable front end 290 K to 40 K using a laser [43]. May be useful for ordinary filter at X-band that has a 0.5 GHz bandwidth and is tunable cooling of chips or cryogenic cooling for signal processing chips. from 9.5 to 11 GHz. Could be useful for DARPA Adaptive RF

Front End (ART) program. MEMS can also be used for 5.8 GRAPHENE: impedance matching high PA to yield high efficiency over wide band like 2-18 GHz. Has the potential for teraherz logic. Can be used as a switch by

redirecting the path of an electron beam [31]. Would allow 5.4 COSMOS, MIXED SEMICONDUCTOR INTEGRATION: complex logic. One graphene device would replace 8 transistors

for implementation of XOR. COSMOS is a DARPA funded program directed to move microwave integration to a higher level. It removes the need for 5.9 METAMATERIALS: bonded wires when integrating thin film networks (TFNs) with Si

CMOS and III-V devices on a silicon substrate (Si); see Fig. 15 Using metamaterials it is possible build a GPS antenna having a [29]. The TFNs contains typically passive circuits, R, L and C. wide scan angle, wide bandwridth, and dual polarized [32]. It can With COSMOS the passive circuits would be in the Si multilayer also be conformal. Two groups are working on a low cost interconnects top layer of Fig. 15. metamaterial electronically steered passive array for internet-on-

the-move [33]. One, Intellectual Ventures (IV), expects

50 production by 2014. The other group is the Un. Siena, Italy. approach to getting the √2 advantage has to be traded off against Using EBG-enhancement a wider scan angle was achieved for the the higher cost, prime power, weight and volume resulting from Purdue S-band Digital Array Radar (DAR); see Fig. 16 [34]. In a the throughput increase required when using MIMO. program for Army Research Lab, Adelphi, MD., Un. of Michigan used EBG in between the transmit and receive antennas 5.11 NEW POLARIZATION: separated by about 3 cm on a transponder operating at

We are all familiar with left and right circular, or H and V. Also

that by using both we can increase our data rate by a factor of

two because these polarizations are orthogonal. Well there are

apparently more than two such “polarizations” and they are all

orthogonal to each other. In fact there are an infinite number. Thus if we could transmit and receive on these other “polarizations” we could increase the amount of data we could transmit over our channels. In the process we would solve the crowding problem of our airways. These “polarizations” are actually other quantum states of the photons. They are called the orbital angular moments (OAM) of the photons. Recently Italian and Swedish physicists say they have demonstrated these OAMs at microwave frequencies, 2.4 GHz in an experiment in Venice, Italy [40]. Fig. 17 compares conventional polarization (linear and circular), also called spin angular momentum (SAM), with OAM. For the Venice experiment to generate OAM microwave signals a standard dish was cut and twisted as shown in the left side of Fig. 18. The receive antenna was a Yagi-Uda seen at the top of the right hand side of Fig. 18. For experiment the standard polarized signal was transmitted using an unaltered version of the cut and twisted parabolic dish. The concept of OAM wave has been around for a long time, since 1909 [41]. Although a dish was used to generate the OAM waves in the experiment, the authors say Figure 16 phased arrays should be used. It has to be said that the practicality of using OAM waves has been questioned by many experts in the field. This is a controversial area. For OAM the signal phase is not constant over the plane perpendicular to the direction of travel. One wonders how one can have a focused 2.72 GHz to realize an isolation of 42 dB, 24 dB above what beam then. One would suspect that it only works in the near would have been realized without the EBG. This is the isolation field. one would have realized for 1 m separation [38]. We live in exciting times.

5.10 MIMO:

Contrary to claims made Multiple Input and Multiple Output (MIMO) radars do not provide an order of magnitude better angle resolution, accuracy and identifiability over conventional radars. This claim for MIMO results from making the wrong comparison of a full/thin MIMO array to a full conventional array rather than to a conventional full/thin array. It is shown in Refs. 45 and 46 that conventional full/thin array radar can have the same angle accuracy, resolution and identifiability as a MIMO full/thin array. Moreover the conventional full/thin array example has a better search energy efficiency. A monostatic MIMO array radar does provide a better angle accuracy than its conventional monostatic equivalent, but it is only a factor of 1/√2 (29 percent) better and its resolution is the same. Alternately, a monostatic MIMO array radar can offer the advantage of the same accuracy as a conventional monostatic array radar with a smaller aperture size, one that is 1/√2= 0.707 smaller, or equivalently 29 percent smaller. This improved accuracy comes Figure 17 at a heavy computation cost. An alternate approach for achieving this factor of √2 advantage is to simply increase the radiated power of conventional radar by a factor of 2. This latter

51 [15] R. Doviak, R. J. and D. S. Zrnic, “Doppler Radar and Weather Observations”, 2nd Ed., Chap. 4, 1993, Academic Press. [16] Nathanson, F., “Radar Principles’, 2nd Ed., Chap. 6, McGraw-Hill. [17] Brookner, E., “Radar Technology”, p.38, Artech House, 1977. [18] D.S. Zrnic, R.J. Doviak, V.M. Melnikov, and I.R. Ivic, “Signal design to suppress coupling in the polarimetric phased array radar”, NOAA/National Severe Storms Laboratory, Feb 20, 2013 [19] Zhang, G., R. J. Doviak, D. S. Zrnic, R. Palmer, L. Lei, and Y. Al- Rashid, Polarimetric Phased Array Radar for Weather Measurement: A Planar or Cylindrical Configuration?”, J. Atmos. Oceanic Technol., 28, 63-73. [20] Wallace, H., mmW Multifunction Systems, 33rd IEEE Compound; see also H. Wallace, ARRAY-2013 Semiconductor Symp, 10-12-11, Hawaii [21] Charvat, G. L., J. H. Williams, Alan J. Fenn, S. Kogon, & J. S. Herd. Res.LL-003 Build a Small Radar System Capable of Sensing Range, Doppler, and Synthetic Aperture Radar Imaging, JAN. IAP 2011. MIT OpenCourseWare), http://ocw.mit.edu (Accessed 27 11). License: Creative Commons BY-NC-SA [22] Google G. L. Charvat Low Cost SAR [23] Google G. L. Charvat Low Cost Array

Figure 18 [24] Puzella, A. and R. Alm, “Air-Cooled, Active Transmit/Receive Panel Array”, IEEE RadarCon-2007, Boston, MA REFERENCES: [25] Puzella, A. and R. Alm, “Air-Cooled, Active Transmit Receive Panel Array”, IEEE RadarCon-2008, Rome, Italy. [1] Brookner, E., “Never Ending Saga of Phased Array Breakthroughs”, [26] Jacomb-Hood, A. et al, “Flex Tile for L-Band Phased Array”, IEEE International Symposium on Phased Array Systems and ARRAY-2010, Boston, MA, Oct. 2010M. “COTS Wireless for Low Cost Technology 2010 (ARRAY-2010), Boston, MA, Oct. I2-15, 2010 Phased Array”, ARRAY-2010, Boston, MA, Oct. 2010, [2] Brookner, E. “Phased Arrays and Radars – Past, Present and [28] Colin Whelan, Raytheon Technology Today, 2010 Future”, Microwave Journal, Jan. 2006, pp. 24-46 [28a] W. Kennedy, Raytheon. [3] Brookner, E. “Phased-Array Radars: Past, Astounding [29] Raytheon Technology Today, 2010, Issue 2. Breakthroughs and Future Trends”, Microwave Journal, Jan. 2008, Vol. 51, No. 1 [30] Technology Review, May/June 2012 [4] Brookner, E., “Astounding Breakthroughs in Phased-Arrays and [31] C. Sung & J. U. Lee, IEEE Spectrum, 2/2012, pp. 32- Radars”, IRSI-2007, Dec. 10-13, 2007 [32] Raytheon Technology Today, 2012, Issue 1 [5] Brookner, E., “Phased-Array and Radar Breakthroughs”, RadarCon- [33] K. M. Palmer, Metamaterial Breakthrough, IEEE Spectrum, 1/12, 2007, 4/17-20/2007, Boston, MA pp 13.14 [6] Brookner, E., “Phased-Array and Radar Astounding Breakthroughs – [34] C. Fulton,"Digital Array Radar, “PhD Thesis, Purdue Un., An Update”, RadarCon-2008, May 26-28, 2008, Rome, Italy 12/10; See Also Fulton, W. & Chappell, W., IEEE COMCAS 2008 [7] Brookner, E., “Active Electronically Scanned Arrays (AESAs) – [35] Longbrake, M., ET AL, DBF Rec. on Chip Module, ARRAY-2010 Recent Astounding Achievements, Breakthroughs and The Potential for [36] Zarb-Adami, K., et al, “DBF for Large Phased Array”, ARRAY- Low Cost”, RF Alliance Conf.: Enabling Multi-Antenna & Broadband 2010, Boston, MA, Oct. 2010 RF Systems, April 5-6, 2010, Purdue Univ., in association with NSWC, [37] Ahn, H. et al, “DBF for Conformal Phased Array”, ARRAY-2010, Crane, IN Boston, MA, Oct. 2010 [7a] P. Moran, NSSC Leading Edge, Vol. 7, No. 2; [38] Sarabandi & Y. J. Song, “Subwavelength Transponder USING [7b] Washburn, D. and W. Risas, CJR, Microwaves & RF, 11/2010, pp Metamaterial Isolator,” IEEE AP Trans., 7/11, pp 2183-2190 136, 138 [40] Tamburini, F.; Mari, E.; Sponselli, A.; Thidé, B.; Bianchini, A.; [8] Tolley, A. and J. E. Ball, “Dual-Band Radar Development,” NAVSEA Romanato, F. (2012). "Encoding many channels on the same frequency Leading Edge, Vol. 7, No. 2. through radio vorticity: First experimental test". New Journal of Physics [9] Knott, J., “Multifunction Electronic Warfare (MFEW) Technology 14 (3): 033001. doi: 10.1088/1367-2630/14/3/033001. Development Program”, NAVSEA Leading Edge, Vol. 7, No. 2. [41] Poynting, J. H., “Wave Motion of Revolving Shaft, and a Suggestion [10].https://www.fbo.gov/index?s=opportunity&mode=form&id=ea74bbe as the Angular Momentum in a Beam of Circularly Polarized light”, d32b3c26db0451fc047e69629&tab=core&_cview=1 Proc. Royal Soc. London. 6/24/1909 [11] J. Herd, et al, IEEE Radar 2010, Washington, DC [42] Raytheon Technology Today, 2011, issue 1. [12] Conway, D., J. Herd and K. Hondl, “Digital Beam Phased Array [43] J. Zang et al, “Breakthrough of Optical Cooling”, Laser Focus Radar for Aircraft and Weather”, EuRAD, 2012. World, June 2013, pp. 53-55. [13] NextGen Surveillance and Weather Radar Capability, MPAR [44] Time Magazine, Feb. 22, 2011. Notional, Functional Requirements Document Version 2.2, April 18, [45] E. Brookner, MIMO Radar: Demystified, Microwave Journal, Jan. 2013, FAA,http://www.ofcm.gov/wg-mpar/reference-nswrc.htm 2013. [14] D. S. Zrnic, V. M. Melnikov, and R. J. Doviak, “A draft report on [46] E. Brookner, “MIMO Radar Demystified and Where it Makes Sense Issues and challenges for polarimetric measurement of weather with an to Use”, IEEE International Symposium on Phased Array Systems and agile-beam phased array radar”, NOAA, 2013, http://www.ofcm.gov/wg- Technology, 2013, Boston, MA. mpar/reference-nswrc.htm.

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52 Dr. Eli Brookner Bio: BEE: The City College of the City of New York, ’53, MEE and DrSc: Columbia University ’55 and ’62. Dr. Eli Brookner at Raytheon Company since 1962, where he is a Principal Engineering Fellow. There worked on ASDE-X airport radar, ASTOR Air Surveillance Radar, RADARSAT II, Affordable Ground Based Radar (AGBR), major Space Based Radar programs, NAVSPASUR S-Band upgrade, , PAVE PAWS, Missile Site Radar (MSR), COBRA JUDY Replacement, THAAD, Brazilian SIVAM, SPY-3, Patriot, BMEWS, UEWR, Surveillance Radar Program (SRP), Pathfinder marine radar, Long Range Radar (upgrade for >70 ATC ARSRs), COBRA DANE Upgrade, AMDR, Space Fence, 3DELRR. Prior to Raytheon he worked on radar at Columbia University Electronics Research Lab. [now RRI], Nicolet and Rome AF Lab.

Received IEEE 2006 Dennis J. Picard Medal for Radar Technology & Application “For Pioneering Contributions to Phased Array Radar System Designs, to Radar Signal Processing Designs, and to Continuing Education Programs for Radar Engineers”; IEEE ’03 Warren White Award; Journal of the Franklin Institute Premium Award for best paper award for 1966; IEEE Wheeler Prize for Best Applications Paper for 1998. Fellow of IEEE, AIAA, MSS. Member of the National Academies Panel on Sensors and Electron Devices for Review of Army Research Laboratory Sensors and Electron Devices Directorate (SEDD)

Published four books: Tracking and Kalman Filtering Made Easy, John Wiley and Sons, Inc., 1998; Practical Phased Array Antenna Systems (1991), Aspects of Modern Radar (1988), and Radar Technology (1977), Artech House. Gives courses on Radar, Phased Arrays and Tracking around the world (25 countries). Over 10,000 attended these courses. Banquet/keynote speaker twelve times. >230 papers, talks and correspondences, >100 invited. Six papers reprinted in Books of Reprints (one in two books). Contributed chapters to three books. Nine patents.

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