Design and Analysis of SIW Iris Bandpass Filters for Ku-Band Applications

Three- and four-pole Ku-band SIW iris bandpass filters are designed, analyzed, and demonstrated with fabricated prototypes. Good agreement between the simulated and measured results is observed. The filters achieve fractional bandwidths of 6.5% and 3.8% at mid-band frequencies of 16.83 GHz and 16.73 GHz, respectively. The mid-band insertion is less than 2 dB (0.9 dB and 1.9 dB) for both filters. The filters offer wide band rejection, and the selectivity of the four-pole filter is 30% higher than the three-pole filter. The optimal design of the main SIW structure, along with the tapered microstrip-SIW transition, ensures that the pass-band return loss of the filters remains well within limits. The filters are compact and exhibit linear transmission phase and nominal group delays (1.01 ns and 2.44 ns), which have great significance in radar transceivers and satellite communication applications.