In this article a microstrip diplexer is proposed which has good performance on the UMTS upload and download bands, as shown by simulation results and actual measurements. The diplexer is based on a two-pole resonator named H-type resonator, and makes strong use of cross-coupling to pass energy between ports. The fractional bandwidth for both bands is about 3%. The diplexer has an insertion loss of less than 1dB and provides more than 20dB of isolation. A lumped element model for the diplexer is also derived, and its response is shown to be in good agreement to the microstrip diplexer.
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