Full-Duplex RF Front Ends : From Antennas and Circulators to Leakage Cancellation

With the increasing demands of wireless communication and sensing such as mobile cellular networks and the Internet of Things, radio spectrum is becoming a scarcer resource more than ever. The electromagnetic waves emitted from a radio transmitter typically occupy a certain information channel that is divided into either time [e.g., time division duplex (TDD)] or frequency [e.g. frequency division duplex (FDD)], and, within this channel, all of the receivers or sensors colocated with the transmitter are normally paralyzed.