Substrate‐Integrated Waveguide Filters Based on Self‐Packaged Frequency‐Dependent Coupling Structure

ABSTRACT Highly selective substrate‐integrated waveguide (SIW) bandpass filters based on a novel self‐packaged frequency‐dependent coupling (SPFDC) structure is presented in this letter, which is composed of a coupling window and an embedded stripline with a metallized blind hole. The proposed SPFDC exhibits controllable slopes of the coupling coefficients, positions of the transmission zeros and coupling strength. To demonstrate the proposed SPFDC, an inline fourth‐order SIW filter based on three SPFDCs and a cross‐coupling quadruplet SIW filter based on one SPFDC have been designed, fabricated and measured. Highly selective responses with three finite transmission zeros are realized.