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

This paper presents the design and characterization of a 7 GHz 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 <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$3-4 \text{GHz}$</tex> DPA module with multi-chip configuration for 7 GHz, since the effect of bond wires and parasitic becomes more significant with higher frequency. Systematic numerical calculation based on the design method used in <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$3-4 \text{GHz}$</tex> DPA modules showed that, although the design space, in which proper Doherty operation can be realized, is substantially reduced in 7 GHz compared to 3.5 GHz case, some limited design space can be found even for 7 GHz with multi-chip configuration. By using this space, GaN DPA module prototype was designed and fabricated with effective area of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$76 \text{mm}^{2}$</tex>. Measurements showed that the DPA module achieved PAE of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$34.5-34.6 \%$</tex>, gain of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$24.2-24.7 \text{dB}$</tex> at average output power of 37.1-37.6 dBm for 6.8-7.1 GHz with ACLR less than −51.4 dBc under 20 MHz modulation signal with PAPR of 7.5 dB, after DPD. The similar results were also obtained under 100 MHz modulation signal. The fabricated DPA module has the highest efficiency and gain ever reported among GaN DPAs in <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$6-8 \text{GHz}$</tex> band with saturation output power over 40 dBm.