A Wideband Highly Integrated and Widely Tunable Transceiver for In-Band Full-Duplex Communication

A fully integrated wideband active duplexing transceiver with baseband noise-cancelling duplexing LNAs is presented. The circuit allows in-band full duplex operation with concurrent reception and transmission in the same band or closely-spaced channels. A passive mixer-first architecture is applied here, sharing a single passive mixer to perform simultaneous up-conversion and down-conversion. The bi-directional transparency of the passive mixer allows the duplexing function to be implemented at baseband instead of RF front end. Under the same condition as required for noise cancellation, the baseband duplexing LNAs buffer the transmitter input signals to the mixer while canceling those signals in receive path. Measurements from the transceiver implemented in 65 nm CMOS show a frequency tuning range of 0.1–1.5 GHz withS₁₁ < -20 dB, NF as low as 5.5 dB and transmitted power up to-7.1 dBm. A 30 dB linear isolation between receive and transmit is generally maintained across both LO frequency and in-band transmit/receive frequency separation. Significant suppression of transmit-induced noise and nonlinear intermodulation between received and transmitted signals are also achieved.