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

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.