Dual-Band Dielectric Resonator Filters Employing TE01δ Mode and Degenerate HEH11 Modes

This article presents a novel dual-band bandpass filter based on cylinder dielectric resonators, where the dielectric mode TE _01δ is exploited to generate the first passband, and the two degenerate modes HEH ₁₁ are used to generate the second passband. In order to achieve the needed couplings between the input/output port and the TE _01δ /HEH ₁₁ modes, a probe with both a straight and a curved section is designed. The needed inner couplings between modes of contiguous cavities are instead obtained by using inductive irises and capacitive probes. A systematic design procedure is provided for achieving the center frequencies and bandwidths with large design freedoms. To validate the methods, a dual-band filter working at 2.249 GHz and 2.607 GHz with bandwidths of 32 MHz, is designed and fabricated. The Filter shows low insertion loss, high rejection and compact dimensions. Measured results demonstrate the feasibility of the proposed approach.