A Wideband Variable Gain Power Amplifier With Phase Compensation and PAE Enhancement Techniques in 65 nm CMOS Technology

In this paper, a wideband variable gain power amplifier(VGPA) based on a 65 nm CMOS process in the Ka-band is proposed. The VGPA is constituted by a two-stage structure, a current steering structure, and a cascode structure. Adaptive bias technology is developed in amplifiers to improve power efficiency. By changing the control voltage of the current steering structure and the gate voltage of the bias circuit towards opposite trends, the phase variation caused by them can cancel each other and reduce the phase variation. For the output matching network of VGPA, a coupler balun is used to improve the bandwidth. A prototype is implemented and post-simulated upon 65 nm CMOS technology. The post-layout simulation exhibits a 3-dB bandwidth of 11 GHz ranging from 23.5 GHz to 34.5 GHz. The peak gain of the VGPA is 26.8 dB at 25 GHz. With the supply voltage of 2.4 V, the VGPA realizes a saturated output power (Psat) of 19.5 dBm, an output 1 dB compression power (OP1dB) of 16 dBm, and a peak power-added efficiency (PAE) of 31.5% at 28 GHz. The circuit shows a gain control range of 10 dB and a root-mean-square phase error of 0.4 degrees in 24.5 similar to 32.5 GHz.