Substrate integrated waveguide bandpass filter with enhancement of out-band suppression using C-shaped symmetrical slots

摘要

A novel C-shaped symmetrical slot for the enhancement of the out-band suppression of the substrate integrated waveguide (SIW) filter is proposed. Three C-shaped symmetrical slots are inserted inter-between adjacent cavities to increase the insertion loss at the high-order mode. The comparison between the SIW filters with/without the proposed slots is presented. The second resonant mode of the SIW filter can be reduced by 7 dB loaded with the C-shaped symmetrical slots, while keeping the in-band insertion loss and return loss unchanged. The introduced four-order SIW bandpass filter with the C-shaped symmetrical slots, operating from 27.5 GHz to 31.25 GHz, are implemented by using the single-layer PCB process and printed on the substrate of Rogers 4003 with a thickness of 0.3mm. The measured results exhibit the good performance of out-bands suppression at 43 GHz.