K-band 0/180° balanced phase shifter with dc-offset cancellation

K-band 0°/180° phase shifter MMIC based on balanced structure which can be applied to BPSK or QPSK modulator with dc-offset cancellation is presented. The proposed balanced phase shifter consists of four Lange couplers, two quarter-wave transmission lines and four switches for open and short terminations. The proposed structure implemented in GaAs 0.15-μm low noise pHEMT process ensures stable 0/180° phase shift while common-mode signals due to the mismatch in reflections by open and short are fed to the isolation port. The proposed phase shifter is verified by the phase shift of 179 ± 1.5° with the insertion loss of 4.5 ± 0.8 dB from 17.5 to 22.5 GHz. The fabricated phase shifter size is 2.2 × 2.85 mm including test pads.