A Compact Waveguide Bandpass Filter Using Hybrid Combination of CSRR and Koch Fractal

This paper presents a compact, wideband, waveguide bandpass filter using a hybrid combination of complementary split ring resonators (CSRRs) and Koch fractal. Three identical planar structures, printed with CSRRs and Koch fractal, have been placed in the transverse plane of a standard WR-90 waveguide at a quarter wavelength distance to form the filter. The proposed filter has been simulated using Ansoft HFSS (version 14) and the obtained frequency response has been compared with the frequency response of its lumped element equivalent circuit. The filter was also fabricated and its frequency response has been measured. The measured result shows a 3-dB fractional bandwidth of 12.66% at resonant frequency 9.95 GHz. The total length of the fabricated filter is 20.33 mm. Detailed design procedure has been presented along with necessary diagrams. A table has been provided to compare the performance of the proposed filter with those already available in the literatures. The table shows that the proposed filter is compact, has higher bandwidth and better frequency response compared to the rests.