Bandwidth of Transmission-Line Resistance Compression Networks for Microwave Outphasing Transmitters

This work investigates the suitability of transmission-line resistance compression networks (TLRCNs) for energy recovery applications in wideband microwave outphasing transmitters. In order to successfully recover microwave power without introducing distortion in the outphasing transmitter, the energy recovery network must remain both efficient and impedance-matched at its input port over variations in both power and frequency. In this work, we analyze the ability of the TLRCN to compress variations in its loading impedances when its driving frequency deviates from the nominal center frequency. Measurements of a four-way TLRCN network terminated with resonant class-E rectifiers demonstrate a peak RF-to-dc conversion efficiency of 75% with a return loss of better than 14 dB over a 10-dB range of input powers and 100 MHz bandwidth around 2.45 GHz.