Dynamic Performance of Electrical Balance Duplexing in a Vehicular Scenario

Electrical Balance Duplexers (EBDs) can achieve high transmit-to-receive (Tx-Rx) isolation, but can be affected by interaction between the antenna and environment. Circuit simulations incorporating measured time-variant antenna impedance data have been used to quantify performance variation and determine circuit adaptation requirements for EBDs operating in vehicular scenarios at 875 MHz and 1900 MHz. Results show that the interaction between the antennas and the external environment is limited and vehicle motion does not necessitate high speed EBD adaptation, however the impedance of dashboard mounted antennas can vary due to interaction with the windscreen wipers, causing substantial variation in the Tx-Rx isolation and requiring EBD re-balancing intervals of 5 ms or less to maintain performance.