A Variable-Power Supply-Modulated Class-E GaN Power Amplifier With 81 % Efficiency Over 10 dB Back-Off for VHF Pulsed Radar Applications

This paper presents a drain-modulated class-E GaN PA that exhibits over 81 % drain efficiency over 10 dB output power back-off. The PA employs a square-wave CW drive based on digital ICs and the drain is modulated between 4 and 28 V to produce variable output powers with high efficiency. The PA capacitors and inductors are manually tuned to achieve high back-off efficiency over the bandwidth. The PA achieves an output power of 51 W at 28 V and drain efficiency stays above 81 % for drain voltages above 8 V. Drain modulator losses are minimal with a maximum drop of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$0.3-0.7 ~\mathrm{W}$</tex> in power and less than about 2 percentage points in efficiency, thanks to the use of an integrated GaN-on-Si half-bridge with only <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$5-\mathrm{m} \Omega$</tex> onresistance and 2-ns switching speed. These findings make the design a suitable and desirable choice for variable-power pulsed radar applications in the VHF band.