18-08-2012, 04:51 PM
FREQUENCY SELECTIVE SURFACES WITH FRACTAL FOUR LEGGED ELEMENTS
[attachment=32125]
Abstract
—Frequency selective surfaces (FSSs) with fractal four
legged aperture elements are studied. Three different order fractal
elements are discussed for comparison. The results show that by using
this novel kind of elements, multiband FSSs with miniaturized elements
can be achieved. The ratio of the first resonant wavelength to the
periodicity can be up to 10.36. Four passbands for normal incidence or
two stable passbands for different incident angle and polarizations can
be obtained. The FSS is analyzed by the spectral domain approach.
INTRODUCTION
Frequency selective surfaces, which are used widely as microwave
absorbers [1] and filters [2], have been extensively investigated over the
years [3–8]. In many communication situations, multiband FSSs are
required. Several techniques for multiband FSSs have been presented
in the previous papers: layered FSS [3], perturbation of a single-layered
FSS [4], and the use of multiresonant elements such as Sierpinski dipole
elements [5], double square loop elements [3] and fractal cross dipole
elements [14]. In practice, The FSS with multiresonant elements has
the advantages of a lighter structure, a simplified design and ease to
fabricate.
In the conical radome applications, curved FSSs with large
curvature are required. In this context, FSSs with miniaturized
elements are preferred, since small unit cells are distorted less and in
turn less distortion of the transmission response. In the metamaterial
applications, such as artificial magnetic conductor, miniaturized
element is also required to facilitate flexible spatial filtering for an
arbitrary wavefront. In [9], the fractal Hilbert curves are used to reduce
the element size. In [10], the improved Gangbuster elements are used.
Zhang, Yin, and Ma
In this paper, FSSs with fractal dipole aperture elements are
presented. Three different order fractal elements are discussed. The
results show that both multiband and miniaturized elements can be
effected by using higher order fractal elements.
FRACTALS AND THEIR APPLICATIONS
Fractals are geometrical shapes that are self similar, and can generate
almost any complex structure in nature, through iterating of certain
simple geometries. By using fractal shapes, an arbitrarily long curve
confined in a given volume can be obtained. This property has been
shown effective in reducing the spacing between resonant elements in an
FSS [9] and in reducing the volume occupied by small antennas [11].
And by exploiting the self-similarity property of fractals, multiband
and wideband behaviors can be achieved in both FSS [6, 14] and
antenna [12, 13] applications.
ANALYSIS OF FSSS USING SPECTRAL DOMAIN
APPROACH
Spectral domain approach has been successful in analyzing frequency
selective surfaces [2]. First, the Green’s function of the multilayered
media is calculated in the spectral domain, by using the transmission
line theory.
[attachment=32125]
Abstract
—Frequency selective surfaces (FSSs) with fractal four
legged aperture elements are studied. Three different order fractal
elements are discussed for comparison. The results show that by using
this novel kind of elements, multiband FSSs with miniaturized elements
can be achieved. The ratio of the first resonant wavelength to the
periodicity can be up to 10.36. Four passbands for normal incidence or
two stable passbands for different incident angle and polarizations can
be obtained. The FSS is analyzed by the spectral domain approach.
INTRODUCTION
Frequency selective surfaces, which are used widely as microwave
absorbers [1] and filters [2], have been extensively investigated over the
years [3–8]. In many communication situations, multiband FSSs are
required. Several techniques for multiband FSSs have been presented
in the previous papers: layered FSS [3], perturbation of a single-layered
FSS [4], and the use of multiresonant elements such as Sierpinski dipole
elements [5], double square loop elements [3] and fractal cross dipole
elements [14]. In practice, The FSS with multiresonant elements has
the advantages of a lighter structure, a simplified design and ease to
fabricate.
In the conical radome applications, curved FSSs with large
curvature are required. In this context, FSSs with miniaturized
elements are preferred, since small unit cells are distorted less and in
turn less distortion of the transmission response. In the metamaterial
applications, such as artificial magnetic conductor, miniaturized
element is also required to facilitate flexible spatial filtering for an
arbitrary wavefront. In [9], the fractal Hilbert curves are used to reduce
the element size. In [10], the improved Gangbuster elements are used.
Zhang, Yin, and Ma
In this paper, FSSs with fractal dipole aperture elements are
presented. Three different order fractal elements are discussed. The
results show that both multiband and miniaturized elements can be
effected by using higher order fractal elements.
FRACTALS AND THEIR APPLICATIONS
Fractals are geometrical shapes that are self similar, and can generate
almost any complex structure in nature, through iterating of certain
simple geometries. By using fractal shapes, an arbitrarily long curve
confined in a given volume can be obtained. This property has been
shown effective in reducing the spacing between resonant elements in an
FSS [9] and in reducing the volume occupied by small antennas [11].
And by exploiting the self-similarity property of fractals, multiband
and wideband behaviors can be achieved in both FSS [6, 14] and
antenna [12, 13] applications.
ANALYSIS OF FSSS USING SPECTRAL DOMAIN
APPROACH
Spectral domain approach has been successful in analyzing frequency
selective surfaces [2]. First, the Green’s function of the multilayered
media is calculated in the spectral domain, by using the transmission
line theory.