Microwave GaAs power FETs

Power levels in excess of 2 W a t X-band, 1/2 W a t Ku-band and 1/5 W a t 22 GHz have been reported. Additionally, various research efforts currently under way have goals of 5 W, 1 W and 1/2 W a t these frequencies, respectively. These goals are entirely realistic and will offer the circuit designer a low voltage, 3-terminal source o f microwave power from a relatively simple solid-state device. Although one of.the chief pacing items in this area is the ability to handle ever-increasing power levels, the GaAs FET has a number of other very desirable system incentives. Typical power added efficiencies of 30% at X-band down to 9% a t 22 GHz have been demonstrated. The FET exhibits fairly linear operation t o within 1 dB of i ts saturation level, with two-signal carrierlintermodulation ratios of 20 to 30 dB. They also offer low AM/PM conversion and ease of temperature stabilization. Finally, the old gremlin, narrow bandwidth, associated with many other solid state power devices, is absent. Octave bandwidth performance has been readily demonstrated at moderately high power levels.