An Ultra-Compact Wideband Tunable Autotransformer-Based Electrical-Balanced Duplexer with 46-70GHz 30dB Isolation Bandwidth

An ultra-wideband and tunable passive auto-transformer (AT) based electrically balanced duplexer (EBD) for an in-band full-duplex (IBFD) and frequency-division duplex (FDD) radios at mm-Wave frequencies is proposed. The isolation between the transmit (TX) and receive (RX) ports is enhanced by a simple feedforward balance network and an antenna tuning network, which parameters are calculated explicitly based on closed-form expressions. A chip prototype, fabricated in TSMC 65nm CMOS technology and occupying an ultra-compact die area of 0.02mm2, demonstrates 30dB of TX-RX isolation over the bandwidth of 19GHz around the center frequency of 60GHz along with 10GHz of tuning range. TX-antenna and antenna-RX insertion losses are 3.8 and 4dB, respectively.