Measuring system efficiency in multi-mode PA modules for mobile phones

A multi-mode GSM/EDGE/UMTS power amplifier (PA) module, comprising a highly-efficient CMOS hybrid power-supply modulator combined with a BiCMOS power amplifier, is used to quantify the relative efficiency enhancements that can be achieved by three different supply-tracking regimes: polar modulation, envelope tracking and average envelope tracking. The power efficiency of the PA module is measured for the given standards over a 20 dB range of output power levels. A demonstrated improvement in PA efficiency was observed with all supply tracking regimes, the highest with polar modulation, where PA efficiency > 60% is achieved. However, after taking into account power dissipated in the supply modulator, the envelope tracking technique was found to offer the best PA module efficiency, improving the nominal fixed supply efficiency by up to 25% for the EDGE standard.