Fishbone substrate integrated waveguide structures

In this paper, a new substrate integrated waveguide (SIW) structure is introduced. This structure uses some oblique slots on the top surface of the conventional SIW structure. These slots reduce the cut off frequency without affecting the width of the SIW structure. The results show that these slots are non-radiative. A prototype of the proposed structure which is named Fishbone SIW structure, is simulated, fabricated and measured. The measured results show that the proposed structure achieves an insertion loss of 0.7 ± 0.5 dB, return loss of better than 10 dB from 3.2 to 5.4 GHz and size reduction of about 40 % . To further size reduction, the half mode of the Fishbone SIW structure which is named HM-Fishbone SIW structure is designed and fabricated. This structure achieves a return loss of better than 10 dB from 3 to 5.5 GHz and an insertion loss of 0.8 ± 0.6 dB. The measured results of the proposed structures are in good agreement with the simulated ones. The results show the ability of the Fishbone SIW and HM-Fishbone SIW structures in term of size reduction.