Self-interference cancellation via beamforming in an integrated full duplex circulator-receiver phased array

Abstract

This paper describes how phased array beamforming can be exploited to achieve wideband self-interference cancellation (SIC). This SIC is gained with no additional power consumption while minimizing link budget (transmitter (TX) and receiver (RX) array gain) penalty by repurposing spatial degrees of freedom. Unlike prior works that rely only on digital transmit beamforming, this work takes advantage of analog/RF beamforming capability that can be easily embedded within an integrated circulator-receiver array. This enables (i) obtaining SIC through beamforming on both TX and RX sides, thus increasing the number of degrees of freedom (DoF) that can be used to obtain SIC and form the desired beams, while (ii) sharing the antenna array between TX and RX. A 750MHz 65nm CMOS scalable 4-element full-duplex circulator-receiver array is demonstrated in conjunction with a TX phased array implemented using discrete components. A tiled 8-element system shows (i) 50dB overall RF array SIC over 16.25MHz (WiFi-like) bandwidth (BW) with < 3.5/3dB degradation in TX and RX array gains, respectively, and (ii) 100dB overall array SIC including digital SIC, supporting +16.5dBm TX array power handling.