Microstrip Bandpass Filters with a Maximum Number of Attenuation Poles

In this paper a novel configuration of microwave planar filters, with multiple cross-couplings and with a number of attenuation poles equal to the order of the filter, is investigated. The location of the poles on the frequency axis can be controlled, allowing the design of band-pass filters with improved selectivity with respect to the adjacent channels. A microstrip bandpass filter with the novel configuration was designed, verified by em-field simulation, fabricated and tested. The response of the designed filter are in good agreement with the specification, confirming the possibilities of realizing microwave band-pass filters of a relatively low order with moderate losses and with improved selectivity performances.