A 28-47.5 GHz broadband power amplifier using improved MCR technique in 40-nm CMOS

Abstract

This paper presents a broadband power amplifier (PA) implemented in 40-nm CMOS process for low power application. The PA cascades two stages of common-source differential transistors and adopts symmetrical magnetically coupled resonators (MCRs) for impedance matching and single-ended differential conversion. Theoretical analysis elucidates the effect of the resonator Q on the frequency response of the transformer, thus giving the distribution of the poles and their precise locations, and revealing the quantitative relationship between bandwidth and gain ripple. A method for efficiently balancing gain ripple and bandwidth in k, Q space under low-power conditions when the intrinsic Q of the source impedance is high is described in detail. Measurement results demonstrate a 51.6% 3-dB bandwidth from 28 to 47.5 GHz. The PA achieve 10.7 dBm P${}_{\mathrm{sat}}$, 8.5 dBm OP${}_{\mathrm{1db}}$ and 23% peak PAE at 31 GHz.