An Ultra-Compact Wideband Tunable Autotransformer-Based Electrical-Balanced Duplexer Achieving 30 dB Isolation Across the 46-70 GHz Frequency Range

Proposing an ultra-wideband and tunable passive auto-transformer (AT)-based electrically balanced duplexer (EBD) for in-band full-duplex (IBFD) and frequency-division duplex (FDD) radios at mm-Wave frequencies. Isolation between transmit (TX) and receive (RX) ports is improved with a simple feedforward balance network and an antenna tuning network. Parameters are calculated explicitly using closed-form expressions. A chip prototype, fabricated in TSMC 65 nm CMOS technology, occupies an ultra-compact die area of 0.02 mm2. It achieves 30 dB of TX-RX isolation over a 19 GHz bandwidth centered at 60 GHz, with a tuning range of 10 GHz. TX-antenna and antenna-RX insertion losses are 3.8 and 4 dB, respectively.