Broadband Doherty Power Amplifier Using Out-Phased Current Combining Method and Asymmetric Cells

In this paper, we propose a broadband structure for a Doherty power amplifier (DPA) with an extended output power backoff (OBO) of 8 dB by using an out-phased current combining (OCC) method and an asymmetric architecture. To determine the matching conditions of the proposed DPA, the output matching network (OMN) is analyzed using transmission lines. Previous studies have employed additional circuits for broadband DPA design; in contrast, this paper presents the use of a compact but optimal OMN structure that provides a broad bandwidth. This structure is selected following the conversion of the transmission line-based OMN into lumped element-based OMN, incorporating the parasitic components of the transistor. The fabricated DPA with the proposed broadband OMN exhibits a drain efficiency (DE) of 55.1~65.9 % at the output power of 42.0~43.4 dBm across the 3.0~4.2 GHz band. For the OBO of 8 dB, power gain of 6.6~10.8 dB and DE of 43.1~53.7 % are achieved by using a continuous wave (CW) signal. Additionally, by using a 5G New Radio (NR) signal (100 MHz bandwidth and 7.8 dB PAPR), the amplifier archives a DE of 45~55 % at 34.0~35.4 dBm output power, with an adjacent channel leakage power ratio (ACLR) ranging from −34.3 to −23.2 dBc.