3.5-GHz ultra-compact GaN class-E integrated Doherty MMIC PA for 5G massive-MIMO base station applications

Abstract

This paper presents a high gain ultra-compact Doherty PA design approach based on 28 V two-stage GaN MMICs. A 20 W asymmetric and 26 W symmetric Doherty amplifier operating in the 3.4–3.6 GHz band were designed into a small footprint 7×7 mm2 QFN plastic package for 5G massive MIMO base station applications. The use of package-integrated low-loss passive devices to realize the class-E like inverted Doherty combiner resulted in excellent final stage drain efficiencies of 60 % at 8 dB output power back-off and 65 % in saturation, to the best of the authors' knowledge the highest reported final stage drain efficiency for GaN MMIC based integrated Doherty PAs in the 3.5 GHz band. The full asymmetric PA board yields a measured line-up efficiency of 43 % with an associated gain of 26 dB at 35 dBm average power of a 20 MHz LTE signal, corresponding to 8 dB output power back-off.