Multiband Filters with Positive or Negative Dispersive Cross-Couplings

In this paper, the design of a sixth-order dualband bandpass filter with dispersive cross-couplings for improved selectivity is presented. The dispersive coupling element can provide a positive or negative value, depending on its shape, for generating an additional transmission zero in the upper or lower stopband. The dispersive elements with positive and negative values are presented and the proposed approach is verified by the design and the fabrication of a prototype of the multiband filter in the X band. Index Terms- Filter synthesis, microwave filter, dispersive coupling, multiband filter