Bandpass SIW Filter with Six Cross-Coupled Resonators

In this paper, we consider the synthesis of a fourth-order bandpass filter with a central frequency of 12 GHz, made using SIW (Substrate Integrated Waveguide) technology. A negative cross-coupling structure between resonators is implemented in the filter using a coplanar waveguide. This allows you to form a pair of transmission zeros that improve out-of-band suppression characteristics. The position of the transmission zeros can be adjusted by changing the length of the coplanar waveguide, as it determines the negative coupling coefficient. Compared with conventional linear SIW filters, the proposed design has a sharper attenuation, as well as increased out-of-band suppression, which improves frequency selectivity. The article also discusses the implementation of two pairs of transmission zeros in a SIW filter with six resonant cavities. The presented filter topology has the advantages of miniaturization, high degree of integration, and increased frequency selectivity.