Wideband bandpass filter of folded substrate‐integrated waveguide integrating with stripline compact resonant cell

A wideband bandpass filter constructed into folded substrate‐integrated waveguide (FSIW) is proposed, incorporating with the stripline compact resonant cell (CRC). The folded SIW preserves nearly the same propagation characteristics with its counterpart substrate‐integrated waveguide (SIW); however, the width of FSIW is only half of SIW, providing a more compact platform for many novel circuits or subsystems. A prototype of this wideband bandpass filter was fabricated and measured. Good agreements are observed between the experimental results and the simulations. The results demonstrate a wide passband about 83.7% (from 3.3 to 8.05 GHz) at −10 dB return loss and the insertion loss in the entire passband is less than 0.26 dB.