A 24-GHz fully integrated isolator with high isolation in standard RF 180-nm CMOS technology

A novel 24-GHz MMIC isolator is developed in TSMC 0.18-µm CMOS. A new topology using the nonreciprocal common-source amplifier and the directional coupler is proposed to realize an isolator without ferrite. This isolator achieves 36-dB isolation with 1.8-dB insertion loss. The dc power consumption is only 3.6 mW. The performance of this isolator is comparable to those of the ferrite isolators except for the bandwidth. To the author's knowledge, this isolator is the first MMIC isolator in CMOS technology.