A novel dual-band forward/inverse Doherty power amplifier

In this paper, a dual-band forward/inverse Doherty power amplifier (F/I-DPA) based on hybrid load modulation network is proposed. The amplifier replaces the lambda/4 transmission line in a conventional Doherty power amplifier (DPA) with a coupler-based load modulation network (LMN) that incorporates a post matching network (PMN) for load modulation at the isolated ports. The LMN can realize both conventional DPA and inverse DPA load modulation methods in the operating band. In order to verify this theory, a prototype with 6 dB output power back-off (OBO) at 3.3-3.6 GHz and 4.8-5.0 GHz was designed. The measured results indicate that the output power of the F/I-DPA is 42-42.8 dBm and 41.4-43.4 dBm, and its saturation efficiencies are 68.1%-74.2% and 61%-72.6%, respectively. The corresponding 6-dB OBO efficiencies is 37.4%-54.5% and 38%-49.3%, respectively. The dual-frequency forward/inverse DPA proposed in this work uses a coupler-based load modulation network instead of a lambda/4 transmission line. This modulation network can modulate the load impedance from high impedance to low impedance and also from low impedance to high impedance. The impedance design space and bandwidth are expanded. image