Technology Today Volumn 3 Issue 1 - Raytheon

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PHASED ARRAY SYSTEMS Continued from page 19 interconnected using high-speed wire interconnection techniques. The ATF Radar has approximately 2000 T/R modules per array, and approximately 20 systems are now in operation. The radar system provides long range, multi-target, all weather, stealth, vehicle detection and multi-missile engagement capabilities. Legacy E-Systems engaged in the development of phased array antennas in the 1970s with the development of the AN/SYR-1 Telemetry Downlink program. The resulting system and it’s phased array antennas were an integral part of the TERRIER and TARTAR missile programs that remained active until the DD-993 class HRL RF Technology HRL Laboratories, LLC, in Malibu, California is a shared R&D center for LLC Members Raytheon, Boeing and General Motors. The LLC Members pool their resources to explore and develop new technologies in the pre-competitive stage and directly fund specific development activities of their own at HRL. In this arrangement, the investment by each company gains a leverage of approximately 5-6 times the companies’ annual expenditure. HRL Laboratories includes four labs: Information Sciences, Sensors & Materials, Communications & Photonics, and Microelectronics, with approximately 200 researchers encompassing a variety of technical disciplines. The Microelectronics activity provides a broad spectrum of RF technologies to Raytheon, supplemented by expertise from Sensors & Materials, Communications & Photonics and Information Sciences. Mixed Signal integrated circuits is the largest technical area in Microelectronics that is focused on Raytheon’s needs. HRL has a unique concentration of world-class expertise in the design and fabrication of continuous time, tunable delta-sigma (∆Σ) analog-to-digital converters (A/Ds), spanning not only R&D for future products but also supplying mil-standard components for today’s needs. These unique A/Ds are capable of real-time reconfiguration from narrow-band to wide-band operation for direct sampling at frequencies from 60 MHz to above 1 GHz. Other activities in this area are focused on the development of compact, low-power direct digital synthesizers for potential application to multi-function phased-array systems. HRL is an experienced source for the development and delivery of microwave technology from the earliest days of GaAs MES- FET technology through today’s rapid advances in GaN microwave technology. State-of-the-art GaN devices, both power amplifiers and low noise amplifiers, are being developed at HRL from X-band through Ka-band with state-of-the-art power densities and noise figures being demonstrated. HRL’s highly regarded InP HEMT MMIC technology has been moving toward higher frequencies (e.g., W- through D-band) where new applications are beginning to emerge to take advantage of these capabilities. In the rapidly evolving areas of antennas and RF front-ends, HRL is investigating approaches to antennas utilizing frequencyselective surfaces with novel microelectronic devices that lend themselves to simplified (and thus potentially low cost) electronic steered arrays. Complementing this is HRL’s development of miniature tunable filters having dimensions and tunability consistent with multi-function phased array elements. HRL has developed significant technologies in RF and analog signal transmission and processing by optical and photonic methods and optoelectronics components. In a related activity, this capability has been used to examine the enhancement of A/D converter performance through a combination of photonics and electronics. Longer-term approaches to miniature, integrated RF subsystems are being investigated through various techniques for heterogeneous integration. Through these techniques, technologies could be chosen for their optimized characteristics and then ultimately integrated into miniature subsystem components. 20 ships were retired. Beginning in the 1980s, E-Systems, in conjunction with The Johns Hopkins University/Applied Physics Lab (JHU/APL) and the Navy, initiated development of the Cooperative Engagement Capability (CEC) program. To achieve the objectives of the program, high-power phased arrays were required in order to meet the dynamic directional beam communications needed between network participants, while overcoming significant levels of jamming and atmospheric fading. Given the technology constraints of the period, a circular passive phased array antenna driven by a large, dual tube, Traveling-Wave Tube Amplifier (TWTA) was used to create the required ERP. Beam steering was accomplished by commutating columns of radiating elements around the array for coarse beam steering, and then fine-steering the beam in azimuth and elevation using Pin-diode, switched line lengths to control phase on each transmitting element. In the mid-1990s, technology had progressed to the point that 13-watt GaAs T/R modules could be reliably manufactured, and a circular active, aperture antenna was built. This iteration incorporated the phase shifters and receive LNAs within the T/R module, with each T/R module switched between one of four elements to allow commutation around the array. Subsequent to this antenna iteration, a four-face planar antenna is being developed. It incorporates 2-watt GaAs transmit modules at each radiating element of the transmit array, with
separate receive elements, employing GaAs LNAs on each element. Each GaAs transmit or receive module includes a phase shifter, which allows individual elements to be controlled separately. The key building block and the real work horse of the AESA, is the T/R Module (a simplified version is illustrated in Figure 1). Raytheon’s (Legacy Texas Instruments’ Defense) module factory is now the world’s premier producer of solid-state gallium arsenide (GaAs) T/R Modules for the US defense industry. Modules represent from 30–50 percent of total AESA cost. As such, T/R modules are many times the greatest single cost element of a radar or communications system. Within the T/R module, GaAs MMICs represent the largest cost element, followed by manufacturing assembly, touch and support labor. From 1982–1986, Legacy TI won and executed an Air Force Manufacturing Technology program to automate T/R Module manufacturing in order to meet the cost and performance challenges at frequencies higher than the UHF range. There are many factors that require much tighter control of assembly process parameters and packaging demands. Among these are: the low fracture toughness of GaAs, the presence of air bridges, and thinner die (.05 mm vs .38 mm) — compared to conventional low–frequency, Si dies, and the high frequency and high packaging density requirements inherent in microwave, and millimeter wave products. Control of these factors requires precise and repeatable placement and interconnection of components. In addition, the high thermal dissipation requirements for most T/R applications require void-free solder and epoxy attachment. For cost effective, high volume manufacturing purposes, such rigid requirements can be met only through automation. Raytheon’s T/R module manufacturing technology currently consists of fully automated work cells, using a common carrier with multiple modules. The common carrier format permits modules to be processed similar to silicon or GaAs wafers, with the modules — or equivalent die — being processed in an array format throughout the assembly and test phase. Module or subassembly architectures, using upright and/or flip chip components, can be processed through any work cell. Integrated capacity, cost and scheduling tools allow changing requirements to be quickly assessed and optimized. Automatic part pedigree using bar code scanners allows lot traceability for all components within a module down to the individual die level. In order to achieve performance and cost goals, this method of traceability allows statistical analysis, correlation and optimization of test requirements from the device to system level. As a result of these improvements, T/R module manufacturing cost has decreased by an order of magnitude from the early 90s with tens of thousands of modules now being processed monthly. In addition, some future systems are projected to have their module or T/R element cost reduced by over two orders of magnitude, to less than $50 per T/R channel. Legacy Hughes Aircraft developed the first fielded active array in a fighter aircraft in the Late 1980s. These arrays used fullyactive TR modules, operating at X Band frequencies. Nineteen units were installed and fielded in F-15 fighters. Since Fighter aircraft are limited in weight, power and cooling, many technological advances in these areas needed to be made. Hughes developed highly efficient, lightweight power supplies, X-band GaAs-based MMICs with a high level of integration through advanced packaging and liquid flow using heatsink techniques. These arrays are corporate fed with integrated monopulse networks. In the areas of surveillance and reconnaissance, passive arrays were employed to perform Synthetic Aperturemapping Radar, (SAR), terrain guidance and targeting on high flying U-2s and the B-2 Stealth bomber. This technology incorporated Figure 2. Corporate and Space Feed Systems The Patriot Space Fed Phased Array F-15 Corporate Fed Array ferrite-based phase shifters for beam scanning. From Passive to Active, a Sensor Revolution The advent of phased arrays began more than 30 years ago, but it was in the early 1990s that AESAs began to thrive and mature. The earliest implementation of phased array antennas was focused on radar applications. These initial phased arrays utilized high-power tubes that would generate the required electromagnetic energy needed to feed the phased array, so that the array could provide enough Effective Radiated Power (ERP) to detect the target at the necessary selected range. Two popular feed approaches were used for these passive, phased arrays: corporate and space fed (see Figure 2). The space-fed arrays typically used a cluster of feed horns to illuminate the rear elements of the array. The Patriot Array is an example of a space-fed architecture. Each rear element is connected to the front element via a transmission line and phase shifter. Corporate-fed phased arrays, still currently popular with AESAs, used a transmission line media, such as waveguide or stripline, Continued on page 22 21
Page 1 and 2: technology today HIGHLIGHTING RAYTH
Page 3 and 4: TECHNOLOGY TODAY technology today i
Page 5 and 6: (less than 20 KHz) to visible light
Page 7 and 8: Radars aboard the F-15, F-14, F/A-1
Page 9 and 10: and target discrimination, which ar
Page 11 and 12: ELECTRONIC WARFARE and Signal Intel
Page 13 and 14: RF Communications Radios, Data Link
Page 15 and 16: emote battlefield sensors to sense
Page 17 and 18: Leadership Perspective Dr. PETER PA
Page 19: Pioneering Phased Array Systems & T
Page 23 and 24: AESAs use the brick package. Brick
Page 25 and 26: Capability Maturity Model Integrati
Page 27 and 28: Figure 2. The deployment infrastruc
Page 29 and 30: New Global Headquarters Showcases T
Page 31 and 32: DAVID K. BARTON ROBERT E. MILLETT C

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