Simple method for a K‐band SIW filter with dual‐mode quasi‐elliptic function response

A simple method for a K‐band substrate integrated waveguide (SIW) filter with dual‐mode response quasi‐elliptic function response is designed, fabricated, and measured around 20 GHz. By using an orthogonal input and output (I/O) feed‐line and adjusting a perturbation, the proposed filter with two transmission‐zeros are so close to the passband that the selectivity and out‐of‐band rejection of the filter are significantly increased. The designed filter demonstrates the superior passband characteristics with a measured central frequency fo = 20 GHz, the insertion loss S21 = −2.9 dB, the return loss S11 = −23.5 dB. Experimental results of the fabricated filter measured by network analyzer are well agreed with the simulation results.