Improvement of power amplifier efficiency by reactive Chireix combining, power back-off and differential phase adjustment

An interesting effect of output power back-off (OPBO) efficiency improvement is presented which is present if 2 power amplifiers (PA) utilizing a reactive output Chireix coupling are combined with input power back-off and differential phase adjustment for maximum efficiency peaking. The capability of significant efficiency improvement at power backoff is demonstrated and validated by means of simulations and measurements. The new design method delivers a power added efficiency (PAE) of 48% at 6dB OPBO and 35% at 10dB OPBO for a 25.7W Si-LDMOS PA at 2.14 GHz for a WCDMA basestation application