Mode Extension of Load-Modulated Balanced Amplifier with Enhanced Efficiency

In this paper, a mode-extended non-Zo pseudo-Doherty load modulated balanced amplifier (N-PD-LMBA) by utilizing a non-Zo termination is presented for enhanced load modulation of the balanced amplifier (BA) and efficiency profile. The proposed N-PD-LMBA can adaptively switch to hybrid asymmetric LMBA (HA-LMBA) mode at medium-power level for increased efficiency and to PD-LMBA mode at saturation for enhanced power. For illustration, the proposed LMBA, with a 12 dB OBO range and 40% bandwidth (1.6 - 2.4 GHz), was designed and implemented using GaN transistors. Measurement results show that the prototype exhibits a drain efficiency (DE) of 58.2-70% at saturation, 46.6-59% at 6dB-OBO and 48-63% at 12dB-OBO, with an output power of 42.8-44.1 dBm.