A Compact Ka-Band Variable Gain Phase Shifter With Bi-Directional Phase Inverting Amplifier

This brief presents a compact Ka-band bi-directional variable gain phase shifter (BVGPS) using 28-nm CMOS technology. The BVGPS consists of a phase inverting bi-directional variable gain amplifier (PI-BVGA) and 3-bit switched-delay type phase shifter (STPS). The proposed PI-BVGA is implemented with a current cancelling topology for a low phase variation over a gain control range. The PI-BVGA can operate bi-directionally and provide 180° phase shift. Therefore, comparing the conventional BVGPS, this BVGPS achieves a high gain with the compact size since 180° phase shifter and single-pole double-throw (SPDT) switches are eliminated. The average rms phase error over the 16 dB gain control is 1.1° and measured rms phase and gain errors of 16 different phase states are 8.3° and 0.74 dB, respectively, at the center frequency. The maximum gain of the BVGPS is $0.7{\pm }1$ .3 dB in the 16 different phase states with a power consumption of 40 mW. The BVGPS occupies 0.21 mm2, excluding the pads.