An 8–28GHz Bidirectional Variable-Gain Phase Shifter for 6G FR3/ 5G n258 FR2 Featuring a Magnitude-Equalized Self-Similar 90° Coupler and a Simultaneously Phase-Temperature Compensated Attenuator

This work proposes a bidirectional vector modulator-based all-passive variable-gain phase shifter (VGPS) across 8–28 GHz for 6G FR3 and 5G n258 FR2. It achieves the full 360° phase shift (PS) range with a 5-bit resolution, and an 8-dB variable gain (VG) range with a 4-bit resolution. To cover this wide fractional bandwidth (FBW) with a reasonable chip size, a wideband self-similar transformer (TF)-based 90° coupler with magnitude equalization networks is proposed and utilized for the in-phase/quadrature (I/Q) generation network. Further, to achieve orthogonal and in-dB calibration-free gain control with temperature robustness, a simultaneously phase-temperature compensated switched-type attenuator is proposed and utilized for the VG units of the vector modulator-based VGPS. The design is implemented in GlobalFoundries 22nm CMOS FD-SOI with a core area of 0.43 mm². In the PS mode, the RMS phase and magnitude errors are lower than 3.7° and 0.74 dB across the entire band, while in the VG mode, the RMS errors are lower than 1.4° and 0.29 dB across the band.