S-band Power Amplifier Design Based on Pseudo-Doherty Load Modulation Structure

This paper presents a technique for achieving continuous load modulation ratio using a Pseudo-Doherty load modulation balanced amplifier. Differing from the conventional Doherty amplifier, the impedance and phase of the Pseudo-Doherty amplifier do not need to be adjusted by impedance inverter and phase offset line, and the load and phase of the peaking amplifier are modulated by using the control signals output from the main amplifier, which lifts the bandwidth limitation of the conventional Doherty and extends the bandwidth. The structure of connecting two parallel peak amplifier transistors through a quadrature coupler realizes wider dynamic range and higher back-off efficiency. A Pseudo-Doherty load-modulated balanced amplifier operating at 2.1-2.7 GHz is designed, and the test results show that the power amplifier output power is greater than 43.5 dBm, the small-signal gain is greater than 10 dB, the saturated power gain is greater than 8 dB, the saturated drain efficiency is higher than 64%, the power back-off 6 dB efficiency is 46-56%, and the power back-off 10 dB efficiency is 45-55%.