An ultra compact and broadband 15-75GHz BPSK modulator using 0.13-μm CMOS process

In this paper, an ultra compact and broadband 15-75 GHz BPSK modulator using standard bulk 0.13-μm CMOS process is described. This modulator was constructed utilizing a new reflection-type topology, with the transmission lines implemented on the thick SiO₂ layer as the substrate to avoid the lossy silicon. The overall chip size, including baseband, LO, and RF probe pads, is only 0.5 × 0.35 mm². Compared with the previously reported GaAs modulators, this work demonstrates a more than 80% chip area reduction, and features an amplitude imbalance of within 0.5 dB with a phase imbalance of within 3° between 15 and 75 GHz. Regarding the modulation quality, the measured error vector magnitude (EVM) of the BPSK modulator at 40 GHz is within 3.5 and 7% for a data rate of 1 and 10 Mb/s, respectively. The LO-to-RF isolation is better than 40 dB among all the operation frequency. From continuous-wave (CW) spectrum characterization, the modulation bandwidth of the modulator is wider than 1 GHz.