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 <0.4°/<0.31dB PS RMS phase error and 31.5-dB tuning range in 65-nm CMOS . 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 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. 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.