This paper presents a design methodology for frequency selective surfaces (FSSs) using metallic patches with dissimilar Sierpinski fractal elements. The transmission properties of the spatial filters are investigated for FSS structures composed of two alternately integrated dissimilar Sierpinski fractal elements, corresponding to fractal levels
A periodic surface is basically a set of identical elements arranged twodimensionally composing an infinite array [
Regarding the geometry of the conducting patch element, a FSS array can present many different shapes ranging from Euclidean to fractal geometries. The use of fractal patch geometries as conducting elements on a FSS periodic design has provided superior performance, for some applications, compared to those using typical patch geometries, such as rectangular, square, circular, dipole, crossdipole, and square loop [
In order to develop high performance spatial filters, some authors have investigated different types of periodic structures, such as reconfigurable FSSs [
Cascading two singleband FSS screens, using conventional patches, it is possible to obtain a dualband frequency response. In [
In this paper we present a fractal design methodology that aims to achieve simple, compact, and multiband FSS frequency responses using dissimilar Sierpinski fractal metallic patch elements on a singlelayer substrate. The Sierpinski fractal metallic patch element shapes of levels
Illustration of Sierpinski patch elements of fractal levels: (a)
The proposed FSSs with dissimilar Sierpinski metallic patches are composed of two different fractal level elements arranged alternately on the same surface, along
Illustrations of the proposed FSS geometries composed of dissimilar Sierpinski patch elements corresponding to the integration of (a)
The FSS simulations were performed using Ansoft Designer commercial software. Two FSS prototypes were selected for fabrication and experimental characterization. The FSS prototypes were measured using a vector network analyzer from Agilent Technologies (model N5230A) and two experimental setups: (i) with elliptical monopole microstrip antennas [
In this work new FSS geometries are proposed based on the alternately integration, along the structure horizontal,
The main goal of this work is to enhance the multiband response and compactness of the proposed FSS geometries with dissimilar Sierpinski fractal elements with respect to those of FSS geometries with identical Sierpinski fractal elements [
Thereafter, two FSS prototypes were fabricated for experimental characterization and comparison purpose. Figure
Photographs of two FSS prototypes composed of dissimilar Sierpinski patch elements with (a)
Photographs of the experimental setups: (a) setup #1 with elliptical monopoles and (b) setup #2 with horn antennas.
The transmission coefficient simulated results for the FSSs presented in Figures
Simulated transmission coefficient results versus frequency obtained for the proposed spatial filters with two dissimilar Sierpinski fractal patch elements and for the FSS geometries with identical fractal level: (a)
In Figure
In Figure
In Figure
Table
Simulated FSS resonant frequencies and bandwidths.
Fractal level  FSS simulated results (GHz)  








 

9.2  1.36  —  —  —  —  —  — 

6.1  0.8  —  —  —  —  —  — 

4.6  0.49  10.9  1.28  —  —  —  — 

5.8  0.27  8.3  0.7  —  —  —  — 

4.5  0.2  8.1  0.37  10.4  0.92  —  — 

4.5  0.19  5.8  0.43  10  0.38  11.4  0.08 
Figure
Simulated and measured transmission coefficient results versus frequency for the fabricated FSS prototypes integrating dissimilar Sierpinski fractal patch elements of levels: (a)
The experimental characterization of the proposed FSSs was performed using a vector network analyzer, two UWB elliptical monopole microstrip antennas, for the frequency range from 2 to 6 GHz (setup #1), and two commercial horn antennas, for the frequency range from 7 to 12 GHz (setup #2). Measured and simulated results are in good agreement, with a maximum resonant frequency deviation of 4.8%. Simulations were performed using Ansoft Designer.
In this work, simple, compact, and multiband frequency selective surface (FSS) structures were obtained by integrating dissimilar Sierpinski fractal patch elements. The proposed FSS geometries enabled the development of multiband bandstop filters due to the integration of dissimilar fractal patch elements on a singlelayer substrate and the FSS element size reduction, provided by the fractal motifs. In addition, the use of dissimilar Sierpinski fractal geometries to design FSS elements also provided resonant frequency and bandwidth adjustments. Furthermore, the FSS design methodology, using alternately dissimilar fractal elements, was validated by means of a good agreement between simulated and measured results. The proposed FSS geometries may be used in many engineering applications, being attractive devices due to low cost, easy manufacturing, and ease integration with other microwave circuits. Currently, multiband FSSs have been proposed to be applied in modern civil construction designs to optimize indoor propagation environments.
The authors declare that there is no conflict of interests regarding the publication of this paper.
This work was supported by CNPq under covenant 573939/20080 (INCTCSF) and contract 307554/20120, Federal Institute of Education, Science and Technology of Paraíba (IFPB), and Federal University of Rio Grande do Norte (UFRN).