Electrical balance isolation for flexible duplexing in 5G mobile devices

Exploiting new technologies will be vital in meeting the demanding requirements of 5G radio access. Flexible duplexing architectures will be a key enabling technology in 5G handsets, virtualising the radio spectrum, reducing cost, and increasing link capacity through full duplex radio communication. The tunability, low cost and small form factor of Electrical Balance (EB) duplexing technology makes it an attractive choice for flexible duplexing in small form factor devices. Circuit simulations incorporating measured antenna data have been used to investigate the performance of a dual notch EB duplexer in a full duplex mode at 1900MHz. Results show that, in general, the isolation bandwidth of a dual notch EB duplexer increases with the notch separation frequency, and that at bandwidths below 75MHz, dual notch balancing achieves transmit to receive isolation within 3dB of optimal balancing. The simulated duplexer provides a 30dB isolation bandwidth of up to 200MHz. Therefore, in addition to providing tunable frequency division duplexing functionality, EB duplexing technology can also serve as a component of a broadband full duplex transceiver, thus providing a fully integrated flexible duplexing solution.