A novel approach for integrating high-Q band-pass filters into microwave integrated circuit assemblies

A novel method of electromagnetically coupling an air-dielectric stripline interdigital or combline bandpass filter to a planar microwave circuit has been demonstrated. The filter structure can be soldered or epoxy-attached to the surface of the printed circuit board, resulting in a low-cost, high-performance assembly. By eliminating connectors, reducing wall thicknesses, and, in some cases, printing some resonators, a reduced-size filter suitable for mounting with automatic equipment is produced. Good electrical performance was demonstrated on a single design iteration after some minor or predictable modifications to the coupling gap between the coplanar-waveguide line and the first resonator of the filter. The experimental work was carried out on low-dielectric-constant material, but the concept should work also on higher-dielectric-constant materials such as alumina.<>