X-band bandpass filter structure for passive radar using SIW technology

This paper proposes an X-band bandpass filter structure for the Kolchuga passive radar system as an alternative to the Interdigital structure. The proposed structure uses substrate-integrated waveguide (SIW) technology with series-connected resonant frames arranged in a folded form. With the improved structure, the designed filter ensures the insertion loss, reflection coefficient in the pass band, and attenuation slope in the stop band requirements in the X-band for the Kolchuga radar while optimizing the size. Compared with the SIW bandpass filter using the conventional straight IRIS structure, the proposed filter structure reduces the size but achieves equivalent scattering parameters. The simulation results demonstrate the effectiveness of the proposed filter structure in meeting the required criteria and optimizing the size.