Analysis of FSS Structures with Personalized and Optimized Fractal Geometries for Microwave Filtering Applications
FSS, frequency selective surfaces, antennas, fractals, fractal de Hilbert, planar technology
The development of new fractal-based structures applied to planar technology has motivated a large number of researchers worldwide, very interested in designing devices and circuits with greater stability, better transmission or rejection, compactness, bandwidth and multiband, for example. Particularly, traditional fractals have been widely used in the development of microwave integrated circuits and antennas because they have made it possible to improve their frequency responses. However, in order to extract more advantages from the potential of these geometries, they must be changed according to the desired applications. In addition, due to external interference, spatial filters, such as frequency selective surfaces (FSS), have become increasingly popular with the large growth in the use of wireless technologies, as they appear as an excellent solution for filtering predetermined frequencies. Therefore, the use of traditional or new fractals in these structures always brings specific contributions in improving their frequency responses. The main objective of this work is to improve the current FSS technology using well-known but much modified fractal geometries, with personalized relationship of fractal formation and with additional changes, in order to better use their potentialities. Thus, using some different configurations of the same architecture, based on the Hilbert fractal, one can configure the FSS structure to obtain greater bandwidth, multiband operations, good angular stability and compactness, for example. In addition, these fractal-based structures exhibit characteristics to be investigated in relation to the reduction of the patch element dimensions of the periodic array and to the modification of the antenna resonance frequency. Preliminary results using FSS as ground plane in rectangular patch antennas with inset-feed suggest the possibility of significantly decreasing the frequency of antenna operation, in addition to the appearance of multiband as if the patch were fractal.