Electrical-Balance Techniques for Tunable, Fully Integrated RF Front-Ends

Electrical-balance duplexers (EBDs) are frequency-flexible, highly linear and high-power compatible signal cancellers that can be implemented in CMOS technology. Such a canceller is a great candidate for implementation of a tunable front-end module (FEM), where it can provide TX-to-RX isolation for many bands. In addition, as the cancellation is achieved simultaneously with the signal transfer to/from the antenna, the EBD can provide an important role to enable in-band full-duplex (IBFD) for future wireless standards. IBFD can provide increased throughput and network capacity, amongst other benefits, something that a FEM only based on filters cannot do. In this talk, design challenges of such duplexers are discussed, highlighting several electrical-balance design examples including several duplexers, as well as two alternative electrical-balance topologies that show the flexibility of the concept: a filter and a phase shifter. The state-of-the-art and remaining design challenges are also discussed.