A 7GHz High Efficiency GaN Doherty Power Amplifier Module for 5G Massive MIMO Base-Stations

This paper presents the design and characterization of a 7GHz high efficiency Gallium Nitride (GaN) Doherty Power Amplifier (DPA) module for 5G massive MIMO base-stations. It is challenging to adopt the design method used in 3–4GHz DPA module with multi-chip configuration for 7GHz, since the effect of bond wires and parasitic becomes more significant with higher frequency. Systematic numerical calculation based on the design method used in 3–4GHz DPA modules showed that, although the design space, in which proper Doherty operation can be realized, is substantially reduced in 7GHz compared to 3.5GHz case, some limited design space can be found even for 7GHz with multi-chip configuration. By using this space, GaN DPA module prototype was designed and fabricated with effective area of 76mm². Measurements showed that the DPA module achieved PAE of 34.5–34.6%, gain of 24.2–24.7dB at average output power of 37.1–37.6dBm for 6.8–7.1GHz with ACLR less than -51.4dBc under 20MHz modulation signal with PAPR of 7.5dB, after DPD. The similar results were also obtained under 100MHz modulation signal. The fabricated DPA module has the highest efficiency and gain ever reported among GaN DPAs in 6–8GHz band with saturation output power over 40dBm.