A Novel Dual-Band Controllable Bandpass Filter Based on Fan-Shaped Substrate Integrated Waveguide

A compact dual-band bandpass filter with controllable center frequencies based on the 90° fan-shaped substrate integrated waveguide resonator (FSSIWR) is first proposed in this letter. Dual-band response is achieved by the fundamental mode (TM
₁₀₁
mode) and high mode (TM
₂₀₁
mode) of the FSSIWR, respectively. In this design, two pairs of the posts are loaded at the 45° direction of FSSIWRs, which produce perturbation to adjust the center frequency of the first passband. In order to control the second-passband center frequency, the complementary split-ring resonators (CSRRs) are etched on the surface of the resonator. The etched CSRRs can not only adjust the second-passband center frequency by changing the locations of the CSSRs but also produce a transmission zero (TZ) in the upper stopband of the second-passband. In addition, other five TZs are obtained by introducing source-load coupling, which highly improve the frequency selectivity. Finally, the proposed filter is fabricated and measured. The measured results agree well with the simulated ones.