85–110-GHz CMOS Magnetic-Free Nonreciprocal Components for Full-Duplex Transceivers

Two CMOS nonreciprocal components: 1) an isolator and 2) a circulator are demonstrated at 100-GHz band for full-duplex transceivers for ultra-high-data-rate wireless communication. The proposed nonreciprocal structures are based on a time-domain modulation by signals at around one-sixth of the RF frequencies and spatial duplexing throughout their RF signal paths, demonstrating over 45-dB isolation in a bandwidth of 1.5 GHz over the tuning range of 85-110 GHz. In the presented isolator, two capacitive mixers together with a biasing network form a resonant type of wideband matching for lower loss. An improved delta topology is proposed for the circulator design which reduces the schematic complexity and chip area overhead. Implemented in a 65-nm CMOS with a chip area of 0.13 mm
²
and 0.21 mm
²
, respectively, both the isolator and the circulator achieve over 45-dB isolation and >10 dB return losses throughout the entire bandwidth. A maximum of 4.5- and 5.6-dB insertion losses (ILs) are achieved by the isolator and circulator, respectively.