Four-way lossless outphasing and power combining with hybrid microstrip/discrete combiner for microwave power amplification

This work demonstrates a four-way outphasing and power combining system for microwave power amplification using a novel power combining network. The ideally lossles combining network is implemented using a combination of microstrip transmission-line sections with discrete shunt elements. We present the derivation of the power combining network topology as well as practical implementation details. The new power combining network is demonstrated in a 50-W, 2.14-GHz power amplifier system using load modulation of switching GaN PAs through outphasing for output power control. The system has a peak CW drain efficiency of 59.5% and drain efficiency above 45% over a 8.17-dB outphasing output power range. In modulated tests with a signal bandwidth of 3.84 MHz, the system demonstrates 52% average drain efficiency for a 3.9-dB peak to average power ratio (PAPR) signal, and 38% drain efficiency for a W-CDMA signal with 9.6 PAPR.