A Wideband 120-GHz Variable Gain Amplifier With Multistage Phase Compensation

Abstract

This article presents a wideband 120-GHz variablegain amplifier (VGA) with a multistage phase compensation technique. The proposed multistage VGA consists of two different current-steering VGAs: one with a series inductor to improve gain performance and another with a shunt inductor to compensate for phase variation. To verify the proposed design, a 120-GHz VGA was fabricated utilizing a 40-nm CMOS technology with a compact size of 0.62 mm x 0.38 mm, including pads. Under 2-bit control bias conditions, the proposed VGA provides controlled gains of 0, 2.9, 5.4, and 8.3 dB at a frequency of 120 GHz. In the maximum gain state, the VGA exhibits a peak gain of 12.3 dB while maintaining a 37-GHz bandwidth. Based on complementary phase compensation, the VGA achieves a maximum phase error of 5 degrees within a gain control range of 8.3 dB and an in-band phase variation of 8.5 degrees for a wide frequency range of 100-133 GHz. Under these conditions, the total power consumption is 31.2 mW at a supply voltage of 1.25 V.