Tx/Rx isolation enhancement based on a novel Balanced Duplexer architecture

Duplexers are essential circuit elements in virtually all Frequency Division Duplex (FDD) communication systems. Duplexers provide filtering functions for transmission and reception bands; moreover they provide isolation. In this work we present a novel duplexer architecture that provides increased isolation without increasing the constituting filters order. Among the advantages of this novel technique is the reduction of filter complexity, a 3-dB reduction in filter power handling capacity and improved isolation bandwidth. Two duplexers have been designed, fabricated and characterized. A UMTS duplexer was designed fabricated on RO5870 substrate. Another duplexer in 5.1 GHz-5.8 GHz band was designed and fabricated on Alumina substrate. The results obtained by measurements validated the utility of the architecture in enhancing the Transmitter-Receiver isolation by 15 dB-20 dB over nearly the full band of the filters in both designs.