Inline Pseudoelliptic ${\rm TE}_{01\delta }$ -Mode Dielectric Resonator Filters Using Multiple Evanescent Modes to Selectively Bypass Orthogonal Resonators

A new class of dielectric resonator filters with in-line structure and pseudoelliptic response is presented in this paper. The basic idea consists of using TE_01δ single-mode resonators cascaded along an evanescent mode waveguide and oriented along orthogonal directions. By exploiting multiple evanescent modes, which can alternatively excite or bypass a resonator depending on its orientation, cross-coupling between nonadjacent dielectric pucks can be established and controlled. Various configurations, such as triplets, quadruplets, and quintuplets, can be obtained by properly orienting the various pucks and by exploiting a prescribed set of evanescent modes. In contrast with conventional techniques, pseudoelliptic filters can be implemented without using cumbersome cross-coupled architectures or reduced spurious performance multimode resonators. The experimental results of two sixth-order filters with two arbitrarily located transmission zeros, and a fifth-order filter with three transmission zeros validate the proposed filter class.