Electrical Balance Duplexer as In-Band Full-Duplex Antenna Interface with Fast Orthogonal Searching Methodology

An innovative architecture for a reconfigurable electrical balance duplexer (EBD) as an in-band full-duplex (IBFD) antenna interface with fast orthogonal searching methodology is proposed and examined. The proposed balancing procedure can be performed with linear time- and space-complexity by tuning the reflection coefficient at the balancing port along two orthogonal directions on the Smith chart independently. This methodology significantly reduces the searching time for the optimum impedance. The proposed EBD can support an impedance mismatch up to voltage standing wave ratio (VSWR) of 2. Measured maximum Tx-Rx isolation is better than 58 dB from 2 GHz to 2.8 GHz. 40-dB isolation bandwidth of over 130 MHz is achieved, which covers the 2.4 GHz ISM band. The proposed concept is independent of the types of hybrid couplers of the EBD as well as the technology.