90° hybrid-coupler based phase-interpolation phase-shifter for phased-array applications at W-band and beyond

This paper presents a 90° hybrid-coupler based passive phase interpolator that is utilized to design a W-band 5-bit phase shifter in 0.13 μm SiGe BiCMOS process. In the proposed phase shifter, amplitude weighting is made first by VGAs. Then, a 90°-hybrid performs I/Q phase splitting and phase interpolation to synthesize all four quadrant phases. In this way, the accuracy of the phase synthesis is less vulnerable to an amplifier loading effect. Further, by cascading all building blocks with a low matched impedance the phase shifter will be less sensitive to parasitic capacitance, suitable for mm-Wave applications. The phase shifter is optimized for a transmitter application and the measured peak-to-peak gain variation for all 5-bit phase states is 4.8-9.7 dB at 94 GHz. The measured rms gain error is <; 1.6 dB over 93-108 GHz. The measured RMS phase error is <; 1.5° at 94 GHz. The input and output P-1dB is -13 dBm and -4.7 dBm, respectively, at 94 GHz. The chip consumes 37 mW from 2.2 V supply voltage. The chip size is 1.87×0.75 mm2.