A Dual-band Dielectric Waveguide Filter with independently-controllable frequencies and bandwidths

In this article, a dual-mode dielectric waveguide resonator (DWR) is proposed. A dual-band bandpass filter (BPF) is fabricated using this DWR. The two passbands are constructed by a pair of higher-order modes. These higher-order modes are the TM210 mode and the TMizo mode, which are all from the rectangular dielectric waveguide resonator. Therefore, by changing the width of the resonator cw and the length of the resonator cl, the resonant frequencies of the TM210 mode and the TMizo mode are able to be changed independently. The center frequencies of the filter can be adjusted freely. To excite and extract the modes, metallized blind holes can be set where their electric-fields are the strongest. In this way, the two modes do not affect each other. The coupling structures for different modes are realized by connecting corresponding metallized blind holes. By changing the depth of metallized blind holes at different positions on the resonator, therefore, the coupling coefficients of the two passbands are able to be under control freely so as to adjust the bandwidths of the two passbands independently. At last, the designed BPF's frequencies and bandwidths are able to be controlled freely.