Analysis and Design of a CMOS Bidirectional Passive Vector-Modulated Phase Shifter.

This paper presents a passive vector-modulated phase shifter (VMPS). The passive X-type attenuator consisting of digitally controlled transistor-array units is employed to perform the phase-invertible gain tuning, and thus enables phase shift in all four quadrants. The Wilkinson-like power combiner is utilized to sum up the quadrature signals and avoid impedance mismatches. Analysis proves that the proposed passive VMPS can provide consistent phase-shift performance for bidirectional operation. The proof-of-concept VMPS is implemented in 40-nm CMOS technology and occupies a core chip area of 0.15 mm2. Measured results prove that it can provide consistent bidirectional 6-bit phase-shift operation, with accurate phase tuning (i.e., RMS phase error <24°) and low gain error (i.e., ±0.6 dB) over the whole 70–90 GHz band. [ABSTRACT FROM AUTHOR]