A Compact, High Tuning Accuracy and Enhanced Linearity 37-43 GHz Digitally-Controlled Vector Sum Phase Shifter

Abstract

This paper presents a compact digitally controlled vector sum phase shifter (DC-VSPS) capable of precise gain and phase control across a wide bandwidth. The DC-VSPS utilizes a pair of differential variable gain amplifiers (VGAs) designed to optimize gain and phase tuning accuracy. Moreover, it incorporates differential transformers-based output combiner and input quadrature hybrid, enhancing integration, bandwidth, and matching performance. A 6-bit DC-VSPS prototype was successfully designed and fabricated using the 45 nm silicon-on-insulator (SOI) CMOS technology, occupying a minimal core area of $0.084 \mathrm{~mm}^{2}$. Experimental results demonstrate an excellent tuning range of 360° for phase control with a resolution of 6 bits and 14 dB for gain control with 1 dB resolution. Furthermore, comprehensive measurements indicate excellent performance over the frequency range of 35-43 GHz, with total root-mean-square (RMS) phase error, total RMS gain error, and group delay variation all within 1.5°, 0.24 dB, and ±12 picoseconds, respectively. The prototype also exhibits input-referred 1dB gain compression power levels exceeding 4 dBm and input-output return losses better than 9 dB across the entire bandwidth.