Novel Impedance Flattening Network for Wideband GaN Doherty Power Amplifier at 3.4-3.8 GHz

This work reports a novel impedance flattening network for wideband Doherty power amplifier (PA) targeting 4G and beyond base-stations. Conventional Doherty PA performance is limited in terms of operational bandwidth due to frequency dependent load modulation network involved. Our proposed impedance flattening network mitigates this constraint by introducing frequency lessdependent impedance characteristic at back-off power level. To demonstrate the proposed technique, a wideband Doherty PA is designed using commercially available GaN-HEMT device at 3.4-3.8 GHz. The PA design achieves 58-68% peak drain efficiency over 400 MHz bandwidth while maintaining more than 45% drain efficiency at 7-dB output power backoff. Furthermore, it delivers 42.5-dBm of saturated output power, 14.5 dB of power gain and 0.5 dB of average gain fluctuation across 3.4-3.8 GHz bands.