Coupling-Matrix Design of Dual/Triple-Band Uni-Planar Filters

Dual-band and triple-band filters in uniplanar technology are designed using cross-coupled networks represented by coupling matrices. The multiband response is created by placing transmission zeros within the bandwidth of a wideband filter. Realizable planar topologies can be imposed and associated coupling coefficients enforced during optimization. The design method is demonstrated using three different planar resonator configurations: hairpin, open-loop and quasi-dual-mode resonators. Designs are verified by commercially available software packages and, in principle, by measurements