A 35 dBm PSAT and 41% PAE GaAs Power Amplifier With Series Distributed-Balun

This brief presents a high-power Sub-6 GHz two-way differential power amplifier (PA) with a series distributed-balun output network in $0.5{\mu }\text{m}$ GaAs pHEMT process. The proposed series distributed-balun output network consists of two coupled-line-based distributed-baluns connected in series to achieve low-loss matching and power combining. The general three-port distributed-balun unit and its extended two-way series distributed-balun have been theoretically analyzed in detail. In addition, the multi-layer transformer structure is introduced to enhance the coupling factor of the inter-stage matching network. The measurement results of this three-stage PA demonstrate a peak gain of 32.6dB, with 3-dB bandwidth (BW−3dB) of 4.2-6 GHz. The saturated output power (Psat) is 34–35 dBm covers 4.8-6 GHz, and the peak power-added efficiency (PAE) is 41%. The measured root mean square error vector magnitude (EVMrms) with 160MHz of 64-QAM/256-QAM is 2.4%/1.93% with 28.7/26.5 dBm average output power (Pave) and −36.8/−38.7 dBc adjacent channel leakage ratio (ACLR) without digital pre-distortion (DPD).