Electrical Balance Duplexer Adaptation in Indoor Mobile Scenarios

A key issue impacting the transmit to receive (TX-RX) isolation in electrical balance duplexers is dynamic matching of the antenna impedance by the balancing network. Circuit simulations including embedded antenna measurements have been used to investigate the variation in TX-RX isolation due to device motion, and to study the effect of the operational environment, device speed, and the duplexer adaptation characteristics on the TX-RX isolation. Results show that the increased speed and increased reflection scenarios necessitate increased duplexer adaptation rates in order to maintain TX-RX isolation close to its maximised value. However, despite interaction with the environment, in this operating scenario the simulated duplexer maintained >45dB of TX-RX isolation with no balancing network adaptation, and >52dB with a balancing network adaptation interval of 10ms.