A filter comprising a plurality of zig-zag hairpin-comb resonators that
are separated by one or more coupling gaps is provided. The zig-zag
hairpin-comb resonators may be fabricated using HTS or non-HTS planar
structures, such as microstrip, stripline and suspended stripline. Each
of the zig-zag hairpin-comb resonators comprises a pair of neighboring
legs. The neighboring legs of adjacent resonators straddle a respective
coupling gap. Each of the neighboring legs is formed with zig-zag
sections. In this manner, the filters provide unusual compactness, as
well as minimizing coupling between the resonators.