A Monoblock Dual-Mode Dielectric Waveguide Filter With Symmetric Transmission Zeros

In this paper, a monoblock dielectric waveguide filter (DWF) with symmetric transmission zeros (TZs) based on degenerate dual-mode resonators is presented. The dual-mode dielectric waveguide resonator (DMDWR) based on the TM120 and TM210 mode consists of two pairs of blind holes located on the upper surface of the DMDWR. Resonance behaviors of the dual-mode dielectric resonator and coupling mechanisms of the proposed DMDWR are investigated. The cascaded quadruplet (CQ) topology is obtained by cascading two DMDWRs. By utilizing the frequency-variant coupling principle to realize the negative coupling of the CQ topology, and finally a 4-pole filter with two TZs on both sides of its passband is designed. The simulated results are in good agreement with the ideal synthesis results, which verifies the design concept of the DMDWR filter.