Reconfigurable high efficiency power amplifier with tunable coupling coefficient based transformer for 5G applications

A frequency reconfigurable high efficiency power amplifier (PA) is presented for 5G applications using on-chip switchable matching networks. To cope with increased gate-drain capacitance (Cgd) in deep submicron CMOS PA design at mm-Wave frequencies, a tunable coupling-coefficient based transformer is proposed. This technique dramatically improves the neutralization of Cgd in a common-source PA while maximizing output power and efficiency. To reconfigure the PA between 24 GHz and 28 GHz, a low-loss reconfigurable matching topology is adopted using a switched substrate-shield inductor. Using the proposed techniques, a single-stage reconfigurable class-AB PA is demonstrated in 65 nm CMOS, achieving 42.6% maximum power added efficiency (PAEmax), 14.7 dBm maximum output power (Po, max) at 24 GHz and 40.1% PAEmax, 14.4 dBm Po, max at 28 GHz. The PA occupies a core area of 0.11 mm2 only.