Antennas for Full-Duplex Communication: State of the Art and Way Forward

In contrast to the established belief that simultaneous transmission and reception (STAR) is not possible i.e., wireless communication can only operate in half-duplex (HD) mode, full-duplex communication has emerged by providing double the spectral efficiency by operating in STAR mode compared to its HD counterpart. The fundamental limitation of the STAR operation is the presence of self-interference (SI) between the transmitter and receiver module which degrades the entire communication. In general, SI can occur at three essential stages of a communication system: antenna/RF, analog, and digital. As a result, techniques for SI cancellation (SIC) can be categorized into three parts: antenna/RF domain SIC, analog domain SIC, and digital domain SIC. Considering antennas as the very end/beginning element of the Tx/Rx module, the emphasis is given to the antenna design aspect useful for FD communication having reduced antenna domain SIC. In this chapter, we have covered various state-of-the-art FD antenna designs and novel SIC techniques. These include a layered multi-radiator FD antenna configuration with SIC that uses a near-field decoupling mechanism and defected ground structure, a planar shared-radiator FD antenna configuration with SIC that employs a field confinement technique, and a planar shared-radiator FD antenna configuration with SIC that utilizes vias and stub-loaded resonators.