Dual-Band Filter Inspired by ENZ Waveguide

This letter presents a novel design of the third-order dual-band filter operating in the frequency band 10-15 GHz. The filter consists of two rectangular cavities filled with foam dielectric and connected by an ultrathin waveguide channel, which mimics the epsilon-near-zero metamaterial. Each resonator is designed to support two propagating modes-one per each passband. By changing the filter dimensions for which we have derived analytical expressions, it is possible to change the center frequency of both passbands, their fractional bandwidths, and the position of the transmission zero between passbands.