Implications of Using kW-level GaN Transistors in Radar and Avionic Systems

This paper examines the effect of using normal Class A/B bias for kW-level GaN and LDMOS transistors used in radar and avionic systems. It is shown that Class A/B bias results in an overall efficiency which is typically 5-10% less than the efficiency during the pulse as well as generating significant shot noise in the off period which can cause receiver de-sensitization. A novel automatic gate pulsing and sequencing circuit is described which overcomes both of the above problems. Rise/fall time and latency measurements are presented for this circuit. It is shown that the output noise in the off period is reduced by over 30 dB.