A NOVEL DUPLEXER FOR UMTS APPLICATIONS BASED ON A CROSS-COUPLED FILTER

摘要

A novel duplexer design based on cross-coupled resonators is presented which has the advantages of small size and reasonably sharp cutoff frequency. A duplexer for the UMTS upload and download bands is fabricated and the measured response is shown to be in close agreement to full-wave simulations. The fractional bandwidth for both bands is about 3%. The duplexer has an insertion loss of less than 1 dB and provides more than 20 dB of isolation. Lumped-element models for both the resonator and duplexer are derived and their responses are also shown to be very close to the simulated results, which make them potentially very useful since it can simplify the design of systems using the duplexer.