A 20-31 GHz High Image Rejection Ratio Subharmonic Mixer

A broadband monolithic image rejection subharmonic mixer using a standard 0.18 μm CMOS technology is proposed. This circuit is composed of a band-pass filter with an intermediate frequency (IF) extraction function that can simplify the block diagram of the image rejection mixer. The entire passive circuit is constructed using a broadside coupling structure to achieve a high level of integration. Based on measured results, the proposed mixer exhibits conversion loss of 15.5-18.5 dB at a local oscillator (LO) power of 13 dBm, whereas the 3 dB bandwidth ranges from 20 to 31 GHz (43.1%) with a miniature chip dimension of 0.77×0.81 mm. The LO-to-radio frequency (RF), 2LO-to-RF, and RF-to-IF isolation levels are higher than 22.5, 42.9, and 34.5 dB, respectively. The best image rejection ratio of 29 dBc with 20° phase compensation at 24.5 GHz can be achieved.