Compact dual-mode dual-band microstrip bandpass filter

A new type dual-mode dual-band bandpass filter is proposed in this letter. This filter has two merits. First, the size of this dual-mode microstrip filter is smaller than the conventional dual-mode filters. The proposed structure of the filter is able to achieve 60% size reduction comparing to the traditional structure. In the second, there are a pair of transmission zeros closely to every pass band. Therefore, the selectivity of the filter can be improved. The transmit performance of this filter is simulated by a high frequency full-wave simulator (Ansoft HFSS). It is shown that this structure can generate two operating modes, i.e., the even mode and the odd mode. Finally an experimental filter was fabricated and measured to demonstrate the design. The measured results agree well with the simulated one.