A Low-Loss X-Band Bandpass Substrate Integrated Waveguide Filter using Complementary Split-Ring Resonators

The paper presents a design of an X-Band substrate integrated waveguide (SIW) band-pass filter based on the complementary split-ring resonators (CSRRs). The evanescent mode operation below the waveguide cut-off frequency is employed to design the filter. The structure of the CSRR and the number of CSRR resonators are well-designed to obtain the superior performance of the filter. A special face-to-face CSRR structure is utilized to obtain the low insertion loss and high out-of-band rejection. The filter is designed and tested in the CST Microwave Studio simulator. The simulated results show that the proposed filter can achieve 1.64 GHz bandwidth from (9.22-10.86) GHz which is equivalent to a fractional bandwidth of 16.4. The insertion loss of the filter is smaller than 1 dB in a range of 1.1 GHz. At the center frequency of 10 GHz, the return loss is 44.7 dB, and the insertion loss is 0.7 dB. The stopband rejection from 12-20 GHz is greater than 17.5 dB. The filter is designed on a single-layer Rogers RO4003C substrate. This promising performance ensures a variety of applications for the designed filter such as modern wireless communications or radar. © 2023 IEEE.