A Millimeter-Wave Watt-Level Doherty Power Amplifier in Silicon

This article presents a millimeter-wave (mmWave) power-combined Doherty power amplifier (PA) topology. To reach watt-level output power and simultaneously enhance back-off efficiency, we propose a multifunctional PA network based on an extended rat-race coupler, which enables the following: 1) parallel Doherty load modulation; 2) multiway series power combining; and 3) differential to single-ended conversion. As proof of concept, a 38-GHz PA prototype is implemented in the GlobalFoundries 45-nm CMOS SOI process. It demonstrates 27.5-dBm saturated power (
$P_{\mathrm{ SAT}}$
), 26.9-dBm output 1-dB compression point (
$P_{1\,\text {dB}}$
), and 15.0% power-added efficiency (PAE) at 6-dB back-off. Among recently reported 30–50-GHz silicon-based high-power PAs with
$>$
23-dBm
$P_{\mathrm{ SAT}}$
, our design demonstrates the highest
$P_{1\,\text {dB}}$
and PAE at 6-dB back-off. Tested under 200-MSym/s 64-QAM modulation, the PA achieves 20.0-dBm average output power (
$P_{\mathrm{ avg}}$
) and 12.2% average efficiency (PAEavg).