Full Duplex Circulator-Receiver Phased Array Employing Self-Interference Cancellation via Beamforming

In this paper, we show how phased-array beamforming can be synergistically combined with full-duplex (FD) to achieve wideband RF self-interference (SI) suppression with minimal link budget (transmitter (TX) and receiver (RX) array gain) penalty and with no additional power consumption. An N-path-filter-based circulator-receiver FD front-end enables phased-array beamforming at baseband with minimal overhead by virtue of its multi-phase outputs. A 65nm CMOS scalable 4-element full-duplex circulator-receiver array is demonstrated that repurposes spatial beamforming degrees of freedom (DoFs) to achieve SI suppression, enabling (i) 50dB overall RF array self-interference cancellation (SIC) over 16.25MHz (WiFi-like) bandwidth (BW) with less than 3.5/3dB degradation in TX and RX array gains, respectively, across 8 elements, and (ii) 100dB overall array SIC suppression including digital SIC at + 16.5dBm TX array power handling.