Design of a W-band MMIC balanced BPSK modulator

A balanced BPSK modulator chip worked at W-band was designed in this paper. It has a broadband that can cover almost whole W-band. Due to the impact of the parasitics of the pHEMT devices, the dynamic range of the BPSK modulator is small. In order to extend the dynamic range of the BPSK modulator, we increase the characteristic impedance of the biphase modulator from 50 ohm to 70 ohm. The simulated results show that the balanced BPSK modulator has a large dynamic range from -8.5 dB to -44 dB, and achieves the 180° phase shift. The phase errors are less than ±2°. Both of the input and output return losses are lower than -14 dB. The chip has dimensions of 0.7 mm × 1.4 mm. It can be used as a part of vector modulator.