CMOS Vector Modulator-Based Phase Shifter for Millimeter-Wave Transmitter

Abstract

A D-band phase shifter for CMOS transmitters in a millimeter-wave imaging system is proposed based on vector modulator configuration. Depending on the phase control biasing, the output impedance variation of phase shifters at the millimeter-wave transmitter can interfere with optimizing the operation of power amplifiers with a fixed input impedance. The proposed phase shifter incorporates an output-matching circuit with transformers to minimize output impedance variations. Differential I and Q channels are coupled in each transformer and combined at the power combiner. This configuration can minimize the impedance variation at the output port and increase the saturated output power of the proposed phase shifter. The proposed phase shifter, implemented on 0.184 mm2 using a 65-nm CMOS process, exhibits a maximum gain of −11 dB, a phase shift of over 180°, and an input-referred P1dB of 7 dBm in the frequency bandwidth of 115–135 GHz. The total current consumption is a maximum of 36 mA at a supply voltage of 1.2 V.

Keywords

• cmos
• millimeter-wave
• output impedance variation
• phase shifter
• vector modulator