Miniaturized Dual-Band Differential Filter Using Dual-Mode Dielectric Resonator

In this letter, a dual-mode dielectric resonator (DR) which is directly mounted on the bottom of metal cavity is investigated and utilized to design differential bandpass filter (BPF) with dual-band response. The bottom metal plate acts as an electric wall for a pair of dominant modes, resulting in a half-size reduction of the DR. According to the electric-field distributions of dominant modes and Ampere’s right-hand screw rule, the proposed dual-mode DR that owns two orthogonal half-TE
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dominant modes can be still differentially excited conveniently and applied to construct dual-band differential-mode (DM) frequency response in the design of differential BPF. Meanwhile, the common-mode response can be suppressed to a great extent in a wide frequency range. A transmission zero between the two DM passbands can be generated to improve the band-to-band isolation. Finally, a differential DR BPF with dual-band response is given to verify the proposed idea.