This paper presents a new compact load network for Doherty power amplifiers (DPAs) with only two matching networks, such as an output matching network of the carrier amplifier, and the post-matching network (PMN), even in the presence of parasitic circuits of the packaged transistor. The load network of the carrier amplifier can be configured using a simple L-section matching structure for the complex load impedance. No matching network is required between the peaking amplifier and the current combining junction. As a result, the proposed load network can have a very compact structure with only a short transmission line, and a shunt element for the carrier amplifier, in addition to the PMN. To verify the proposed circuit, a DPA based on two packaged GaN-HEMTs was designed and implemented to have a peak output power of more than 43 dBm for the 3.5-4.0 GHz band. By the measurement results using a 5G NR signal with a peak-to-average power ratio (PAPR) of 7.9 dB and a signal bandwidth of 100 MHz, a power gain of more than 10.5 dB, and a drain efficiency (DE) of 49.5-55.4% at an average power of 36.5 dBm in the frequency band was exhibited. After applying digital pre-distortion (DPD), an adjacent channel leakage power ratio (ACLR) of -51.0 dBc was achieved.
