Dual-Band Bandpass Filter Based on Dual-Ridged Dual-Mode Dielectric Waveguide Resonator

This study presents a novel dual-ridged dual-mode dielectric waveguide resonator (DWR) for dual-band bandpass filter (BPF) designs. It employs the fundamental mode quasi-TM₁₁₀ and the second resonant mode quasi-TM₁₂₀. Two parallel ridges are placed on the top and bottom surfaces of the DWR at the maximum electric-field areas of the quasi-TM₁₂₀ mode to control and reduce its resonant frequency. A metallized nonthrough hole at the DWR’s center controls and decreases the quasi-TM₁₁₀ mode’s resonant frequency. Therefore, a very compact volume is achieved for the dual-mode DWR. For verification, a fourth-order dual-band BPF is designed, fabricated, and measured by using the proposed resonator. The measured results highlight its key benefits: miniaturized volume, lightweight, low insertion loss, and flexible control over the center frequencies and bandwidths of both passbands.