A 28–40 GHz 6-Bit Variable Gain Phase Shifter with <0.4°/<0.31 dB PS RMS Phase/Gain Errors and 31.5-dB Gain Tuning Range

This paper presents a 28-40 GHz 6-bit variable gain phase shifter (VGPS) with 31.5-dB tuning range and low RMS phase/gain errors in 65-nm CMOS for millimeter-wave (mm-Wave) applications. A novel VGPS architecture based on switchless cascode variable gain amplifiers (VGAs) and a gain/quadrant-control IQ generator is proposed. To minimize device parasitics and input/output (I/O) impedance variations across different phase states, a switchless cascode VGA structure is employed to weight the I and Q signals, achieving low RMS phase/gain errors with 5 mW power consumption. In addition, cascode current-canceling (CCC) VGAs are integrated and co-designed with IQ generator, providing a 31.5-dB gain tuning range and wideband balanced IQ signals. Fabricated in 65-nm CMOS process, the proposed VGPS occupies a core chip area of 0.57 mm². Measurements show the VGPS achieves 6-bit phase control with -0.3 dB peak gain, <0.4° RMS phase error, and <0.31 dB RMS gain error across 28-40 GHz. It also provides 6-bit 31.5 dB gain control with <0.35 dB RMS gain error across 28-40 GHz. Furthermore, the measured average input 1-dB gain compression point (IP1dB) is >-1.1 dBm.