Integrated Wideband Self-Interference Cancellation in the RF Domain for FDD and Full-Duplex Wireless Jin Zhou, Student Member , IEEE, Tsung-Hao Chuang, Student Member , IEEE, Tolga Dinc, Student Member , IEEE

Abstract

A fully integrated technique for wideband cancella- tion of transmitter (TX) self-interference (SI) in the RF domain is proposed for multiband frequency-division duplexing (FDD) and full-duplex (FD) wireless applications. Integrated wideband SI cancellation (SIC) in the RF domain is accomplished through: 1) a bank of tunable, reconfigurable second-order high-Q RF bandpass filters in the canceller that emulate the antenna inter- face’s isolation (essentially frequency-domain equalization in the RF domain) and 2) a linear N -path G m-C filter implementa- tion with embedded variable attenuation and phase shifting. A 0.8–1.4 GHz receiver (RX) with the proposed wideband SIC cir- cuits is implemented in a 65 nm CMOS process. In measurement, >20 MHz 20 dB cancellation bandwidth (BW) is achieved across frequency-selective antenna interfaces: 1) a custom-designed LTE- like 0.780/0.895 GHz duplexer with TX/RX isolation peak magni- tude of 30 dB, peak group delay of 11 ns, and 7 dB magnitude variation across the TX band for FDD and 2) a 1.4 GHz antenna pair for FD wireless with TX/RX isolation peak magnitude of 32 dB, peak group delay of 9 ns, and 3 dB magnitude variation over 1.36–1.38 GHz. For FDD, SIC enhances the effective out- of-band (OOB) IIP3 and IIP2 to +25–27 dBm and +90 dBm, respectively (enhancements of 8–10 and 29 dB, respectively). For FD, SIC eliminates RX gain compression for as high as −8 dBm of peak in-band (IB) SI, and enhances effective IB IIP3 and IIP2 by 22 and 58 dB.