Low-Complexity Control of an Electrical-Balance Duplexer

In-band full-duplexing (IBFD) ideally halves the spectral demand of a wireless communication node. A cost-efficient implementation is offered by the electrical-balance duplexer (EBD) architecture, where a tunable impedance is used to ensure Tx to Rx isolation in a hybrid coupler. Conventionally, however, the control of the balancing impedance requires a complex setup, including a controller with high computing power and reflection coefficient measurements. In this paper, an EBD architecture whose control is based on power detector measurements and which runs on a microcontroller with low computing power is proposed. Measured Tx-Rx isolation is demonstrated to be above 52 dB over a broad bandwidth from 2.1 GHz to 2.6 GHz. IBFD operation is emulated in the laboratory, demonstrating the capabilities of the proposed system.