Design of Broadband Doherty Power Amplifier Based on Single Loop Load Modulation Network

This paper proposes a Doherty power amplifier (DPA) architecture with potential for wideband and high efficiency, denoted as single-loop load matching network DPA (SL-LMN). The conventional single combination node network is replaced by an SL-LMN, which adds a new current combination node. This architecture can bring new circuit design freedom, which expands the operating bandwidth of the load modulation network. Using the same prototype topology, the working mechanism of SL-LMN DPA is further illustrated based on three sets of comparative designs. To prove this theory, a broadband asymmetric DPA (ADPA) functioning over 1.9-2.9 GHz is developed and fabricated using two asymmetric GaN transistors. Under continuous wave excitation, the observed data indicates that the drain efficiency of this ADPA is 42.1%-68.9% at saturation and 45.5%-58.5% at 8 dB back-off, respectively. The ADPA has a maximum output power and saturated gain of 44-46 dBm and 6.8-10.9 dB, respectively.