Bandpass characteristics of substrate integrated waveguide loaded with Hilbert curve fractal slot

This paper presents an investigation on the design of miniaturized substrate integrated waveguide unit cell loaded with Hilbert curve fractal slots. It has been found that the proposed structures exhibits a passband which is well below the cut off frequency of the substrate integrated waveguide and hence, can be used in the design of miniaturized filter. Different orientations of the Hilbert curve are investigated and an optimum orientation which gives the best passband response is found. A simple two stage filter based on that particular orientation of Hilbert slot is also presented in the paper.