Envelope Tracking GaAs HBT PA performance characterization under high load mismatch conditions

Handset RF power amplifiers modules (PAM) are often operated into mismatched antenna loads due to reflections from nearby objects. We present experimental results comparing the performance of a GaAs HBT PAM operating in fixed supply and Envelope Tracking (ET) modes under high load mismatch conditions. For a load mismatch voltage standing wave ratio (VSWR) of 3:1 at the PAM output plane, the maximum adjacent channel power ratio (ACPR) compliant output power was >;2dB greater in ET mode than in fixed supply mode for a given DC input power, across all load phase angles. Furthermore, the PAM error vector magnitude (EVM) was found to be substantially independent of load mismatch and output power when operated in ET mode. The measured EVM in ET mode was less than 1.8% across all load phase angles for 3:1 VSWR over an output RF power range of 15 to 28dBm.