Contracts for research into next-generation semiconductor materials that will form the core of improved radar and space communications systems have been awarded by the US Defense Advanced Research Projects Agency (DARPA).
The work, under Phase 2 of the Wide Band Gap Semiconductors for Radio Frequency Applications initiative, is focused on the use of gallium nitride (GaN), a compound that has promising properties for making miniaturised, high-power semiconductors, amplifiers and wireless transmitters.
Advantages of GaN devices include high power output with small physical volume, and high efficiency in power amplifiers at ultra-high power and microwave frequencies. Because it can go beyond the theoretical power and frequency limits of gallium arsenide (GaAs) and indium phosphate-based semiconductors, the use of GaN would enable radar makers to develop more powerful and efficient air defence and surveillance radars, as well as electronic-warfare jammers, smart weapons, missile transmitters, EHF satellite communications and direct broadcast satellites.
Current air defence and surveillance radars are generally limited by GaAs technology to a maximum power of up to 100W across a narrow frequency band up to 1GHz. Using GaN, this class of radar could be extended massively to cover a frequency range beyond 10GHz.
For jammers and some EW and satcom applications, the same technology could extend operations into the 40GHz-plus range at maximum powers of up to 10W and 2W, respectively.
DARPA says cost is the main problem – GaN technology requires a special process to grow a crystal or wafer on which transistors and integrated circuits can be built up. But once the process is implemented on a large scale, industry believes the cost will fall.
Awards have been made to Lockheed Martin, Northrop Grumman and Raytheon covering GaN development for wideband, millimetre-wave (MMW) and X-band technology, respectively.
GUY NORRIS/LOS ANGELES
Source: Flight International