A Millimeter-Wave Three-Way Doherty Power Amplifier for 5G NR OFDM

This article presents a millimeter-wave (mmWave) three-way Doherty output network and its silicon implementation at 38 GHz for 5G new radio (NR) orthogonal frequency-division multiplexing (OFDM). The proposed network synthesis methodology can realize impedance levels that are close to the ideal three-way Doherty operation, reduce the impedance transformation ratio at back-off, and directly absorb the device’s parasitic capacitance. Its design procedure and tradeoffs are discussed in detail. A 38-GHz power amplifier (PA) prototype is implemented in the GlobalFoundries 45-nm CMOS SOI process, achieving 13.7%/11.0% power-added efficiency (PAE) at the 9.5-/11.5-dB back-off, which is among the highest compared with recently reported silicon PAs operating at 35 GHz and above. Tested under 1- and 2-component carrier (CC) 5G NR FR2 64-QAM OFDM signals in the Band n260, the PA demonstrates state-of-the-art average output power (11.3 dBm) and average efficiency (14.7%) with −25-dB error vector magnitude (EVM). The design robustness and reliability are further demonstrated through the testing of multiple samples and PA lifetime.