28.5 Non-Magnetic 60GHz SOI CMOS Circulator Based on Loss/Dispersion-Engineered Switched Bandpass Filters

There has been significant recent research on non-magnetic non-reciprocal components at RF and mm-waves, such as circulators and isolators, based on spatio-temporal modulation [1-3]. Circulators enable simultaneous transmit and receive (STAR) on a shared antenna for applications such as full-duplex wireless communication and FMCW radar. While there has been exciting initial progress, existing architectures do not scale well to mm-waves, whether they are based on switch-based conductivity modulation [1, 2]or varactor-based permittivity modulation [3]. Loss levels increase due to losses in the switches or varactors, isolation is degraded due to reflections produced by parasitics, and power consumption is high due to the relatively high modulation frequencies required. In this work, we present a non-magnetic CMOS 60GHz circulator based on spatiotemporal conductivity modulation (STCM) across a loss/dispersion-engineered bandpass filter. This new architecture improves the insertion loss, isolation, power consumption, and spurious response compared to prior art. The 60GHz circulator achieves 3.6dB/3.1dB insertion loss for TX-to-ANT/ANT-to-RX paths, respectively, TX-to-RX isolation $> 40$dB over 1.3GHz, 3.2dB of ANT-to-RX NF, $> +19.5$dBm TX-to-ANT/ANT-to-RX IP1dBS and spurious tones lower than -30dBc at both ANT and RX ports at a power consumption of 41mW from 1.2V.