Rand Muaffaq Hadi

DOI: https://doi.org/10.5281/zenodo.23420953

In this paper, a half-mode evanescent substrate integrated waveguide (SIW) bandpass filter is proposed. The proposed filter operates below the cutoff frequency of the conventional SIW by adopting the metamaterial technique. The operating frequency of the full-mode substrate integrated waveguide (FM-SIW) is 2.2 GHz, while the cutoff frequency of the conventional SIW structure is 5.2 GHz. Fractal slots are cut from the broad wall of the SIW. First-, second-, and third-order bandpass filters are designed, simulated, fabricated, and experimentally validated using a vector network analyzer. The metamaterial technique achieves a miniaturization of about 60% relative to the conventional SIW structure, and the responses are compared with those of its FM-SIW counterpart, with no obvious difference observed. The half-mode SIW (HM-SIW) technique is then used to achieve further miniaturization of about 50% relative to the original FM-SIW structure. The measured one-stage filter covers the 2.4 GHz ISM band with an insertion loss of about 1.2 dB and a return loss of about 40 dB, and cascading additional unit cells is shown to sharpen the filter’s selectivity while preserving close agreement between simulation and measurement. Finally, the simulation and measurement results agree well with other work in the literature.

bandpass filter, fractal slot, half-mode substrate integrated waveguide (HM-SIW), metamaterial, substrate integrated waveguide (SIW)

This work demonstrated a compact bandpass filter built on a half-mode substrate integrated waveguide loaded with metamaterial fractal slots. The slots allow the guide to pass a band well below its natural 5.2 GHz cutoff, and halving the structure reduces its footprint by a further 50% without degrading the response. Extracted permittivity and permeability confirm the metamaterial behavior, with forward- and backward-wave regions appearing next to each other. Prototypes of one, two, and three cascaded stages were built on FR4 and measured; their responses match the simulations closely, and adding stages steepens the band edges while leaving the center frequency and losses nearly unchanged. Combining a small size, a simple single-layer PCB process, and low loss, the proposed filters are well suited to compact wireless front ends.

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Rand Muaffaq Hadi (2026). Miniaturized Bandpass Filter Using the Metamaterial Half-Mode Technique for Substrate Integrated Waveguide. International Journal of Computer Science Engineering Techniques, 10(5), 281–286. ISSN: 2455-135X. DOI: https://doi.org/10.5281/zenodo.23420953