Single Cavity SIW Band-Pass Filter Using CSRR for WiFi 6E Applications

This study presents the design of a compact substrate integrated waveguide (SIW) band-pass filter specifically designed for WiFi 6E applications at 6.5 GHz. The novelty of the proposed design lies in the combined use of centrally positioned perturbation vias and two symmetrically etched complementary split-ring resonators (CSRRs) within a single SIW cavity. The perturbation vias generate controlled dual-mode excitation and introduce a transmission zero, while the CSRR loading provides strong electric resonance, enabling significant bandwidth reduction and miniaturization. Together these mechanisms achieve a narrow fractional bandwidth of 3.53%, a 23.52% size reduction, and a remarkably enhanced unloaded quality factor of 380 representing an improvement of nearly 294% over the conventional SIW filter while maintaining a low insertion loss of approximately −0.56 dB.