8-pole Cul-de-Sac Dual-layer Microstrip Bandpass Filter

This paper presents an 8-pole microstrip bandpass filter. A cul-de-sac coupling arrangement is employed in the design. The microstrip filter is achieved using a dual-layer structure with aperture couplings between the layers. The filter employed only one cross-coupling between resonators but exhibits 3 finite real frequency transmission zeros. A circuit model and its microstrip layout will be presented together with its circuit model and electromagnetic simulated results. A fabricate filter and its measured results will also be presented in this paper.