Miniaturized Single‐Layer Quasielliptic Response HMSIW Filter With Four Transmission Poles

This study presents a miniaturized filter based on half‐mode substrate‐integrated waveguide (HMSIW) resonant cavities, a bent‐line resonator, and a composite right/left‐handed (CRLH) resonator. The filter employs two HMSIW resonant cavities, which effectively reduce its size and prevent the propagation of higher‐order modes TE 120 and TE 220 within the resonant cavities. The bent‐line resonator and CRLH resonator are etched between the two HMSIW cavities, forming four transmission poles in the passband. By utilizing the opposite phase transmission characteristics of the bent‐line resonator and the CRLH resonator, finite transmission zeros (FTZs) can be generated on both sides of the filter’s passband, resulting in a high‐frequency selective quasielliptic filter response. The filter was fabricated and measured, and the simulation and measurement results are in good agreement. Compared with other SIW filters, the proposed filter features a compact size, improved selectivity, and the ability to suppress higher‐order modes, making it valuable for certain applications.