SIW Bandpass Filter With Wide Stopband Using Harmonic Interleaving and Orthogonal Transmission Techniques

In this article, a wide stopband substrate integrated waveguide (SIW) bandpass filter (BPF) centered at 36.48 GHz with a 3-dB fabrication bandwidth (FBW) of 1.78% is presented and developed based on the orthogonal transmission techniques. Fourth-order Chebyshev filtering response with two transmission zeros (TZs) located at 35 and 41 GHz can be obtained by the exploitation of alternating electromagnetic (EM) coupling topology including negative excitation and planar coupling structure. Combining with the harmonic interleaving between resonant cavities with slot lines etched on the ground plane, the simulated out-of-band suppression is better than 20 dB with frequencies up to more than 8f_{0} , and the measured stopband is extended to 110 GHz due to the limitation of test condition. Good agreements between simulations and measurements can be observed.