An 8-28 GHz 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. 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.