Exhaustive Design and Realization for In-Line Topology Quasi-TEM Mode Dielectric Waveguide Filter With Dispersive Couplings

In this brief, the exhaustive design method for in-line quasi-TEM mode dielectric waveguide filter (DWF) with dispersive coupling is presented. Using the dispersive coupling structure, controllable finite position transmission zeros (TZs) can be implemented without cross-coupling which is commonly used in the quasi-TEM mode DWF, and the coupling coefficient which the filters need can be provided at the center frequency at the same time. The dispersive coupling matrix (CM) including CM M0 at the center frequency and dispersive slope matrix Md are derived from the synthesized traditional CM, and the procedures of parameter extraction in the DWF are also demonstrated in detail. Three 4-2 filters with different TZs and an 8-4 filter are designed to illustrate the feasibility of the fashion. Eventually, an in-line topology quasi-TEM DWF with dispersive couplings is fabricated, post-processed, and measured.