Wideband Input Impedance-Invariant Active Phase Shifter Using Miller Capacitor Cancellation for 5G Communication

Abstract

A wideband input impedance-invariant active phase shifter for millimeter-wave 5G communication is proposed and implemented in a 28-nm CMOS process. It consists of an IQ generator, a Gilbert cell-based vector summer, and a digital-to-analog converter (DAC). Input impedance variations of the vector summer according to the states of the phase shifter, which give rise to IQ mismatches, are substantially suppressed in a wide bandwidth. This is effectively achieved by introducing cross-coupled neutralization capacitors to cancel out the Miller capacitors ( $C_{\text {gd}}$ ) of the input transistors of the vector summing circuit. The implemented phase shifter shows a maximum gain of 0.613 dB at 24.9 GHz and 3-dB bandwidths of 21.7–28.6 GHz (27.4%). The root mean square (rms) phase and gain errors are measured to be less than 1.5° and 0.25 dB, respectively, for 6-bit 360° phase and 4-bit 10-dB gain controls. The core area and power consumption are $0.47~\text {mm}^{2}$ and 14.4 mW, respectively.