Optimal Supply Voltage for PA Output Power Correction under Load Varying Scenarios

Power Amplifiers (PAs) are usually designed for fixed load terminations, which implies that their performance can be severely degraded for varying load operation. This paper presents a load dependent supply voltage (VDD) adaptation that can be used to correct PAs’ output power in these non-optimal scenarios. The calculated VDD values are verified in simulation and laboratory measurements for a 3.55 GHz PA based on a Cree CGH40010F Gallium Nitride (GaN) device. To dynamically vary the VDD, a GaN buck converter, based on the commercial EPC 9067 Demo Board, was used. In addition, to preserve the compression level, the excitation amplitude is accordingly adjusted. The measured output power of the PA was corrected from 37.0 dBm to 39.9 dBm - a 2.9 dB improvement for the worst case loads inside a 2.1 Voltage Standing Wave Ratio (VSWR) circle.