Now: Phased-array Radars: Past, Astounding Breakthroughs and Future Trends (January 2008) | January 17, 2008

Phased-array radars have seen ever increasingly wider use around the world over the last five decades. In recent years, they have seen breakthroughs that led to capabilities not possible in the past. This is exemplified by the development of GaAs integrated microwave circuits called monolithic microwave integrated circuits (MMIC) that make it possible to build active electronically scanned arrays (AESA) that have lighter weight, smaller volume, higher reliability and lower cost. These developments have reached the point where it is now possible to build a low-cost 35 GHz phased array for a missile seeker costing $30/element (total cost of array including all electronics divided by the number of elements). This is made possible because integration allows the whole T/R module to be put on a single chip. For some applications, it will soon be possible to put multiple receivers or transmitters on a single chip. The advances provided by Moore’s Law have now made it feasible to do digital beam forming with all its numerous advantages. This article describes these advances and also covers the potential for GaN and SiC chips that have the capability of higher peak power by a factor of ten than GaAs chips, arrays with instantaneous bandwidths of up to 33:1, SiGe low-cost T/R modules and low-cost MEMS arrays. A real radar application for multiple-input multiple-output (MIMO) has been demonstrated by MIT’s Lincoln Laboratory, which allows the coherent combining of two radars to achieve a 9 dB increase in sensitivity. MIMO also makes possible the optimum removal of clutter in over the horizon (OTH) and airborne radars by permitting adaptive control of the transmit antenna pattern in the receiver.

From: Vol. 51 | No. 1 | January 2008 | Page 30

by Eli Brookner

Over the last five decades since the formation of the Microwave Journal, phased-array radars have seen remarkable advances and wide proliferation around the world. This is exemplified in Figures 1, 2 and 3, which give just a few examples of the phased arrays deployed over the last 50 years and under development in recent years. Back in 1957 there were just a few array radars. John Allen’s article, “Array Radars: A Survey of Their Potential and Their Limitations,”²⁴ first published in Microwave Journal in May of 1962, only showed the experimental L-band electronically steerable array radar (ESAR) that was the predecessor of the FPS-85.

Fig. 1 Example tube (T) and solid-state (SS) passive phased arrays having large productions.¹

In recent years there have been many important breakthroughs in phased-array technology that bode well for the future of phased-array radars.^1,29–36 This article covers some of the past developments and the exciting recent new breakthroughs. The past and recent breakthroughs covered are listed in Table 1.

GaAs MMIC T/R Modules

Defense companies have successfully applied MMICs to AESA radars over the last decade.¹ The MMIC APG-79 AESA radar on the F/A-18 E/F allows simultaneous air-to-air and air-to-ground modes (see Figure 2b).²⁵ This means the aircraft can defend itself while at the same time deliver weapons to the target. This is achieved with only a small increase in the cost of the radar over the older mechanically scanned system.^(ibid)

Fig. 2 Example solid-state discrete (D) and MMIC (M) active arrays.

AESA has permitted the Wedgetail AESA L-band arrays to be placed on the top of a Boeing 737-300 for the Royal Australian Air Force without the need of a rotodome, such as used on E-3 Sentry airborne warning and control system (AWACS) aircraft (see Figure 2b). Wedgetail provides 360° coverage; the two back-to-back dorsal arrays provide ±60° coverage broadside while the antenna above them provides endfire coverage of ±30°.

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