A 4-GHz phase shifter MMIC in 0.18-μm CMOS

This letter presents a tunable phase shifter implemented in a 0.18-μm CMOS process for monolithic microwave integrated circuit (MMIC) applications. By employing active inductors in the synthetic transmission line architecture, the phase shifter exhibits a wide phase control range, low insertion loss, and miniaturized chip area. Characterized by the S-parameter measurement, the fabricated circuit demonstrates an insertion loss less than 1.1 dB within the 360° phase shift while maintaining a return loss better than 10 dB from 3.5 to 4.5 GHz. Due to the absence of distributed elements and spiral inductors, the area of the phase shifter core is 400 × 200 μm ². To the authors' best knowledge, this is the smallest chip size ever reported for an analog phase shifter at this frequency band.