A 28-GHz Full Duplex Front-End and Canceller Using Two Cross-Polarized 64-Element Phased Arrays

This paper presents studies on the self-interference level of a 28-GHz full-duplex phased-array system. The full-duplex system consists of two 64-element phased-arrays and a 28-GHz canceller. The phased-arrays are designed with 2×2 beamformer chips, and the arrays are used as a transmitter and a receiver with a cross-polarization set-up. The 28-GHz canceller is also based on the same 2×2 beamformer chip with multiple-delay taps. The full duplex front-end with a canceller results in 57-dB isolation between the transmitting and receiving arrays at 28.5-29.5 GHz without saturating any LNAs. The system requires only 16-dB additional digital cancellation to bring the self-interference down to the receiver noise floor of 1-GHz bandwidth while the transmit EIRP is maintained at 41 dBm.