This study examines the efectiveness of a band-pass filter integrated with an antenna to reduce electromagnetic interference (EMI) in railway wireless systems. The proposed structure consists of a planar metamaterial screen mapped onto a rectangular dielectric surface, integrated at a short distance from a patch radiating element operating at 5.9 . This configuration preserves both the return loss and radiation pattern characteristics of the patch antenna. within the desired frequency band while efectively reflecting interference signals outside of the band. Additionally, it ofers the benefits of a compact, low-profile design. Our contribution consists of designing a bandpass filter operating at a frequency of 5.9 , dedicated to railway transportation, exhibiting high selectivity at low frequencies where multiple signals are utilized.We design a reflector based on FSS (Frequency Selective Surface) to enhance the antenna's gain. and have better directivity of the proposed antenna.
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ceur-ws.org times, and the presence of communication systems of any wavelength can interact with the train and cause issues. This is why there is a need for materials capable of blocking or filtering waves to prevent reactions with undesirable fields. Our contribution consists of designing a bandpass filter operating at a frequency of 5.9 , dedicated to railway transportation, exhibiting high selectivity at low frequencies where multiple signals are utilized. It will serve as electromagnetic shielding in the low-frequency range. This filter will be designed with miniature periodic cells of the ”Frequency Selective Surface” . It should not disturb (FSS) type placed above the antenna and very close to it (at a distance 1 = 2 the distribution of the electromagnetic field in the near field and far field, while maintaining the dual polarization of the antenna (TE and TM). Additionally, it should not be highly sensitive to the angle of the incident wave.
Frequency Selective Surfaces have been extensively researched and have received significant focus
in the development of antennas, radars, and electromagnetic compatibility within the microwave and
millimeter-wave frequency ranges for many years. They have been proposed for use as spatial filters
[
FSS structures are often periodic and flat.They may comprise metallic elements with various shapes or apertures carved into a metal plate arranged in a regular pattern within a two-dimensional array. The primary attribute of an FSS is its ability to be nearly transparent in a given frequency range and to efectively reflect electromagnetic fields (EM) outside of that interval, there by providing electromagnetic shielding and exhibiting filtering properties. The collective frequency behavior of the structure, including its transfer function, bandwidth, and polarization, is determined by the type and geometry of the elements, spacing between the elements, spatial periods, substrate parameters, and the presence or absence of cascading layers in an FSS.
A notable feature of FSS is that the size of the unit cells is less than half a wavelength.
Frequencyselective properties result from mutual interactions of the elements, requiring a large number of unit
cells to observe the desired frequency-selective behavior. On the other hand, for certain applications,
insensitivity to the angle of incidence of the exciting incident wave is required. Consequently, the screen
size must be small. To achieve a compromise, FSS with miniature elements have been proposed [
We present a configuration illustrated in Figures 1 and 2, featuring symmetry concerning the primary polarization axes and demonstrating identical equivalent circuitry for both horizontal and vertical polarization. This assembly can be conveniently produced by depositing components on opposing sides of a dielectric substrate. Our proposed design employs Rogers 5880 as the substrate, with dimensions ℎ = 0.254, , permittivity of 2.2, and a loss coeficient of 0.0009. On one side, a circular metal patch of radius is etched, while on the other side, a square metal frame with side length and a metal line width is present. The period of this square cell is .
Our aim is to reduce the dimensions of the cell while targeting a specific resonance frequency. We establish the condition < 2 , where denotes the wavelength, with the resonance frequency controlled by adjusting parameters and . The geometrical attributes of the depicted FSS cell in Figure 1 are fine-tuned to resonate at 5.9 GHz, with detailed values listed in Table 1.
Figures 3-6 present simulation outcomes of the S parameters for the proposed structure in Figures 1 and 2 under TE and TM modes across various angles of incidence . Notably, the FSS structure, resonating at 5.9 , demonstrates a −3 bandwidth spanning 0.77 in TE mode (equivalent to 13% of the bandwidth fraction) with an insertion loss of −0.20 at 5.9 for normal incidence and −0.33 for an incidence angle of 40∘. In TM mode, the insertion loss varies from −0.20 to −0.22 as the incidence angle escalates from 0∘ to 40∘. Remarkably, the filter response exhibits minimal sensitivity to both the incidence angle and the TE/TM polarization of the electromagnetic wave.
At 30 , the transmission coeficient 21 is −83 for the angle of incidence = 0 ∘. Consequently, at low frequencies, this cell can be considered as an electromagnetic shield (see Figures 7 and 8 ).
For designing the antenna, the 5.9 resonance frequency and the FR-4 substrate material are firstly selected. A lossy FR-4 substrate with dimensions ( × ) , relative permittivity of 4.3 and thikness of ℎ = 1.6 is used in the antenna design. For both the hexagonal patch and the ground plane (dimensions × ), this becomes the copper material with Thickness ℎ = 35 . Starting from a hexagonal patch constructed from a rectangular patch of dimensions × , we construct a hexagonal patch of side ℎ . A rectangular slot of dimensions × is optimized, in order to obtain the proposed antenna resonant at this frequency. Proposed antenna topology is shown in figures 9 and 10. Design parameters are optimized to give performances at 5.9 operating frequency and they are summarized in Table 2 in and 90∘. The maximum gain is 3
. The antenna radiates forward and backward.
In order to increase the gain of this antenna and direct its radiation forward, we propose the idea of placing a miniature metamaterial reflector behind the antenna and at a distance = 4 = 12.7 , to for ℎ = 0 ∘ achieve constructive interference with the primary source coming from this antenna. Figure 13 shows the shape of the proposed single-sided FSS-2 cell which plays the role of a reflector made up of 3 × 3 cells.
Figures 14 and 15 shows the 2D radiation pattern of the 3 × 3 FSS-2 reflector antenna at 5.9 with an increase in gain to reach 7 as well as the directivity.
We will investigate the impact of the periodic structure with a period shown in figures 1 and 2 on a closely located hexagonal antenna. Parameters such as 11, radiation pattern, and antenna gain, both individually and with the FSS, will be analyzed. Figure 16 depicts a 5 × 7 array of second-order FSS cells
in the (Oz) direction above a vertical hexagonal monopole antenna with in cascade to obtain a selective filter.
Reflector along the Oz axis. The same 5 × 7 array of second-order FSS cells is placed at a distance 2 = 4
Figure 17 illustrates the 11 parameter of the hexagonal antenna alone and in conjunction with a 5 × 7 array FSS cells. We note that the bandwidth of the antenna increases from 2.7 to 1.5 authorized by the filter of [5 − 6.5] 90∘, respectively. It can be observed that the FSS impact significantly the radiation of the antenna by increasing gain and directivity. The antenna thus becomes more directive. At this frequency, the maximum gain of the antenna increases to 8 with an eficiency greater than 90% on the operating band.
In railway settings, the powerful signals used in train communication systems, especially in the lower frequency range, can disrupt the functioning of wireless devices by causing electromagnetic interference (EMI). To mitigate this issue, incorporating a filter onto the antenna can be highly advantageous. This paper proposes a filter-antenna design, utilizing a resonant metamaterial screen positioned near the patch element to maintain antenna performance at the 5.9 operating frequency. Additionally, it ofers out-of-band rejection with a minimum attenuation of 40 from 30 to 1 . Both numerical simulations and experimental tests successfully validate these results, positioning the design as a promising solution for EMI reduction in wireless railway applications. Furthermore, its simple design and single-layer construction suggest it can be fabricated at a low cost.
The authors have not employed any Generative AI tools. for for
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