Payload power amplifier with average power tracking in Ka-band satellite downlink

In this paper, a K-band power tracking high power amplifier (HPA) module using a digital potentiometer integrated feedback is proposed. The supply modulator consists of a pulse width modulation (PWM) controller, DC-DC converter and a digital potentiometer integrated feedback loop, and provides dynamic supply voltages to HPA for the optimal efficiency. The digital potentiometer is operated as a voltage-controlled resistor whose resistance is automatically adjusted by a sampled RF input to HPA and consequently changes the feedback voltage that determines a supply voltage. Also, the designed module package using zig based on aluminum for minimizing self-resonance, zig loss characteristic is optimized. The designed HPA module is verified by a PAE better than 17% maintained over 31 dBm output power at 20 GHz at which Ka-band satellite downlink is allocated.