A Wideband W-band 6-bit Active Phase Shifter in 28-nm RF CMOS

A wideband W-band 6-bit vector-sum based active phase shifter which was implemented using a 28-nm RF CMOS process is presented. The proposed phase shifter consists of a differential I/Q generator and a vector-summing amplifier with differential input and output buffers to use virtual grounds at high frequencies. The I/Q generator was designed with a differential hybrid coupler structure, and the mismatch in its differential input should be small to obtain accurate I/Q signals. To reduce the differential mismatch at the I/Q generator input, source cross-coupling capacitors are introduced at the common-gate stage of the cascode input buffer. The measured results indicate a root mean square (RMS) gain error of 0.69-0.98 dB and RMS phase error of 6.8-9.3 degrees over a wide frequency range of 76 GHz to 104 GHz. The average peak gain of all 64 states is 3.5 dB at 82 GHz. The fabricated phase shifter has a chip area of 0.32 mm
²
with power consumption of 26 mW.