Compact microstrip balanced-to-balanced diplexer using stub-loaded dual-mode resonators

抄録

A new microstrip balanced-to-balanced diplexer based on stub-loaded dual-mode resonators is presented in this letter. The proposed balanced diplexer primarily consists of two balanced bandpass filter channels, and both channels can be independently designed, thus bringing great flexibility in the diplexer design. Besides, due to the direct connection of two dual-mode balanced filters, no additional matching net-works are demanded at the common input port, leading to a significant size reduction. A bandpass coupled line structure is introducing as output feeding line which generates transmission zero on lower side of passband. For demonstration, a prototype balanced diplexer operating at 2.20 and 2.63 GHz is implemented and measured with 3-dB fractional bandwidths of 7.3% and 6.8%. Both simulated and experimental results are provided in satisfactory agreement.