Realization of fractal resonator cells developed on substrate-integrated waveguide for S-band filter applications

A compact bandpass filter based on a substrate-integrated waveguide with multiple fractal open complementary split-ring resonators is proposed herein. The proposed fractal configuration is achieved through the introduction of defected fractal cells on the conducting surface. The working principle of the proposed filter is based on evanescent-mode propagation. The fractal configuration acts as electric dipoles and generates a passband region. The bandwidth of the S-band filter is enhanced through the use of multiple fractal cells, achieving optimized performance. The SIW-based hybrid fractal is analyzed for two configurations, i.e., with and without a gap, with S₂₁ of −1.8 dB, S₁₁ of −24.75 dB, and 2–4.4 GHz for the design with the gap, and S₂₁ of −1.5 dB, S₁₁ of −31.2 dB, and 2.1–3.6 GHz without gap. The S-band filter is designed, and a prototype is measured; the simulation and measurement results are compared and found to align well.