An Ultraminiaturized Frequency Selective Surface With Angular and Polarization Stability

In this paper, the Minkowski fractal is used to design the geometry of a frequency selective surface (FSS) unit cell, which resembles the shapes found in nature. The proposed FSS unit cell has both angular and polarization stabilities of incident wave. For the miniaturization of FSS and decrease of resonance frequency, interdigital capacitances (IDCs) are devised in the FSS structure, which do not eliminate angular and polarization stabilities. The dimensions of the unit cell are 5 mm × 5 mm and miniaturized 0.095λ0×0.095λ0. The resonance frequency is specified as 5.75 GHz with 155 MHz bandwidth. An equivalent circuit is derived for the unit cell to evaluate its frequency responses. The effects of variations of the geometrical dimensions of the FSS unit cell on its performance are studied. A prototype model of proposed FSS is fabricated and measured. The performance of its full-wave computer simulation results and measured data are compared and are shown to be in good agreement.

In this paper, a new geometrical shape of the bandpass modified circular ring frequency selective surface (FSS) structure with significant electrical response such as angular stability up to $$50^{\circ }$$50? of the angle-of-incidence (AOI) for both the perpendicular (TE) and parallel (TM) polarized waves has been discussed. The geometrical parameters of the proposed bandpass FSS is obtained by the transformation of bandpass single square loop FSS structure parameters. To achieve the frequency response of the proposed bandpass structure, commercially available 3D electromagnetic simulators such as CST Microwave Studio and Ansoft HFSS are used. The proposed bandpass FSS structure provides significant angular (i.e., up to $$50^{\circ })$$50?) and polarization (i.e., perpendicular and parallel) stability as compared to that of various other reported literatures. In addition to this, one of the important characteristics of the resonant structure is the quality factor (Q-factor), which has also been discussed for the proposed bandpass FSS structure at different AOI.

Thicknesses of window glasses, radomes, plastic cases of wireless systems are comparable with the wavelength in the millimeter-wave band. The reflections from the dielectric plate surfaces are canceled out of phase when the thickness is identical to a half of the wavelength. However, they are not canceled at any other frequencies except integer multiple of a half wavelength. Therefore, return loss is a serious problem in the millimeter-wave band. A frequency selective surface (FSS) loaded to the dielectric plate controls reflection amplitude and phase, thus, return loss is canceled for various dielectric thickness and frequency. A complex scattering matrix (S-matrix) of FSS is represented by only reflection amplitude |S 11 | from the condition of zero thickness of FSS expressed by shunt suceptance. The total reflection is calculated by converting S-matrices of FSS and a dielectric plate to a transfer matrices (T-matrix) and synthesizing them. We propose to find the required characteristics of FSS from the desired characteristic of whole structure. Broadband characteristic was designed by inserting FSS at the center of the dielectric plate.

Frequency Selective Surface (FSS) is a specialized structure used in the field of electromagnetic waves and radio frequency (RF) engineering. It is designed to exhibit selective transmission or reflection properties based on the frequency of the incident electromagnetic waves. This article describes the design, construction, and analysis of a textile-based band-stop frequency selective surface for use in the highly EM-polluted GSM, Wi-Fi, LTE, and WiMAX bands. A full-wave EM solver called CST Microwave Studio was used to develop and simulate the unit cell of the proposed FSS at the relevant frequency. In this study, embroidered and screen-printed textile based FSSs were designed. According to the results of this study, it was demonstrated that both embroidery and screen printing FSSs exhibit resonance at a frequency of 3.5 GHz. The screen printing method yielded the best results in terms of resonance frequency sensitivity, while the embroidery method showed a resonance frequency shift. It was observed that the stitch directions and density are important parameters in the embroidery method. Gaps between the embroidery paths in the production of embroidered FSSs resulted in differences from simulations due to the disruption of the structural integrity of the unit cell. Consequently, textile-based FSSs offer advantages over traditional FSSs. This study highlights the potential of textile FSSs as an effective means of reducing electromagnetic pollution, and suggests that further improvements in the design and production processes of textile FSSs can be made.

Fractal geometries have been extensively implemented in the design of multiband antenna and frequency selective surface (FSS). For example, convoluted and Hilbert patch elements were first proposed to reduce the unit cell size of FSS (Parker and El Sheikh, IEE Proc.-H, 138, 19–22, 1991.) A fractal FSS with self-similar Sierpinski dipole array was shown to have two stop bands (J. Romeu and Y. Rahmat-Samii, IEEE Trans., AP-48, 1097–1104, 2000). However, its resonant frequencies are rather sensitive to incident angles and polarizations. Minkowski patch FSS and Sierpinski carpet fractals have been shown to provide two or three stop bands with dual polarization capability (J.P. Gianvittorio, et. al., IEEE Trans., AP-51, 3088–3096, 2003.) Recently miniature band-pass FSS with fractal antenna-filter-antenna arrays was designed and demonstrated with good frequency selectivity (S. Zheng, et. al., IEEE AWPL, 11, 240–243, 2012.) A dual band fractal FSS with a 3:1 reflection to pass band ratio and significantly improved resonant frequency stability was proposed by the author (T.K. Wu, Microwave Optical Tech. Letters, 54, 833–835, 2012).

This work reveals the Design and development of Dual wide band frequency selective surfaces (FSS). Dual-band FSS based on single and multi layers with or without or extra discrete components has been discussed and analyzed. Dual wide band-pass FSSs has been designed and developed by using two metallic layers for the wide targeted pass band frequency bands range of 3.53-5.3 GHz and 3.53-4.21 GHz. In the initial step of Development ultra thin double layer slotted FSS has been used. These generate resonance at 4.0 GHz and 4.8 GHz. Furthermore Hilbert shaped slotted resonator increase pass band width enhancement. Lastly the opposite alignment of similar FSS metallic plate to form the proposed dual layer FSS which exhibit the bandwidth enhancement of the frequency bands.

In this article, a novel and compact Frequency Selective Surface (FSS) with dual-band pass characteristics is proposed. The proposed design of the FSS unit cell is composed of two concentric rings with slotted stubs connected to the outer side of each. The proposed FSS structure provides a dual band-pass characteristic with operating frequencies of 7.5 GHz and 9.8 GHz having a bandwidth of 1.4 GHz for both bands. Both operating bands can be controlled independently by varying the design parameters of the structure. The structure is insensitive to oblique incidence angles up to 60 degree. Further, the geometry is low profile and angular stability and polarization are stable. The proposed design finds very promising applications in C and X bands.

In this paper, a dual-band Frequency Selective Surface (FSS) absorber is presented for Wireless Local Area Network (WLAN) security. The FSS absorber is designed for two frequencies of interest, i.e., 2.45 GHz (lower band) and 5.25 GHz (upper band), respectively. FSS design consists of two layers; first layer consists of conducting square-loop elements while second layer consists of resistive square-loop elements, placed in-front of a conducting FSS layer. The proposed FSS design provides good frequency stability for oblique incidences for perpendicular (TE) and parallel (TM) polarizations. It provides better absorption rate for 2.45 GHz and 5.25 GHz frequency bands and allow the transmission of other microwave frequencies. Also, the proposed FSS design reduces multipath fading of additional WLAN signals which occurred due to the placement of conducting FSS layer. Presented results demonstrate that the proposed FSS design has a stable frequency response for the desired frequency bands for TE and TM polarizations with good absorption rate when the incident wave angle varied from 0<SUP>0</SUP> to 45<SUP>0</SUP>.

Single-layer dual-band frequency selective surface for coverage-enhancing applications in millimeter-wave 5G

Purpose The purpose of this paper is to present the results of a particle swarm optimization (PSO) method applied in the design of a square-loop frequency selective surface (FSS) via the equivalent circuit model (ECM), considering the dielectric effective permittivity as a variable in the optimization problem. Design/methodology/approach In the optimization process considered, besides the FSS square loop geometric parameters, the thickness and relative permittivity of dielectric material used as support are included as variables in the search space, using for this a model of dielectric effective permittivity introduced by the authors in a previous work. Findings Square loops were designed and the obtained results were compared with designs reported in literature for applications in wireless local area network and long-term evolution 4G systems. The low computational cost is remarkable as well as the acceptable accuracy obtained with the proposed approach. The PSO method results were implemented with the ECM and compared with those obtained via Ansys – high frequency structure simulator commercial software simulations. Originality/value The lack of a model of dielectric effective permittivity for the ECM causes a restricted search space in the stochastic FSS design process limited to only geometric parameters, as it is reported in the available literature. The proposed approach simplifies and makes more flexible the design process, and allows guiding the FSS design to unit cell surface and/or dielectric thickness of small dimensions.

The requirements of frequency-selective surface (FSS) between high transparency in pass band and high reflectance in stop band are contradictory, when they have loaded medium on one side and receive a large range of illumination. In order to solve the contradiction, this paper employs a discrete particle swarm optimization approach (hereafter referred to as a DPSO). In order to seek a balanced FSS with high transparency in pass band and high reflectance in stop band, the periodic intervals and geometrical dimensions of FSS-structures are optimized and designed by using the DPSO method. Simulation and test results indicate that the FSS of super dense Y loop elements in a half-loaded medium structure is presented in this paper: the transparency in pass band and stop band are 80% and 30% respectively. The DPSO method will offer an excellent FSS for the radome which receives a large range of illumination, and on the other hand, it provides a theoretical guidance for the requirements of FSS between high transparency in pass band and high reflectance in stop band.

ABSTRACTIn this paper, the idea of cross‐coupling is applied to realize zero‐controllable high‐selectivity band‐pass frequency selective surface(FSS). The element consists of two resonant layers at the top and bottom and a coupling layer in the middle. Cross‐coupling is introduced into the structure, which makes it have electric coupling, magnetic coupling and direct path. Two transmission zeros(TZs) are generated on both sides of the passband, thus realizing the filtering characteristics of fast roll‐off. The mechanism of TZs generation is studied by using an equivalent circuit odd‐even mode analytical method. Due to its centrosymmetric structure, the FSS has good angular stability and polarization stability. FSS samples with operating frequency at 19.25 GHz, low stop band at 18.2 GHz, and high stop band at 20.8 GHz were fabricated and tested experimentally. The FSS maintains stable performance at an incidence Angle of 75°. The measurement results are in good agreement with the full‐wave and circuit simulation results, verifying the design of FSS.

A novel method of designing the frequency selective surface (FSS) based on spoof surface plasmon polariton (SSPP) modes is proposed and demonstrated. The high-efficiency transmission and a stopband with a steep falling edge can be mediated by the SSPP modes below and above the cutoff frequency, respectively. So the prolific filtering performances can be customized by integrating with the traditional FSSs. As examples, the two kinds of FSSs were designed and demonstrated by simulations and experiments. A bandstop FSS with the suppression level more than 28 dB is first realized in the frequency region of 9.0–14.7 GHz with the steep rising and falling edges. Then, a dual bandpass FSS is designed by sandwiching the SSPP structure array between the two layers of traditional FSSs. It is indicated that the designed FSS shows two passbands in the frequency ranges of 4.2–4.3 GHz and 8.7–10.3 GHz, and the insert loss is less than 0.5 dB.

This work presents an electromagnetic optimization technique that blending full-wave method, artificial neural network, and population-based search algorithms for optimal design of frequency selective surfaces (FSSs) with fractal motifs. We consider a simple application of this technique in a single-layer FSS with Sierpinski island fractal patch elements. The optimization technique replaces the computational intensive full-wave method of moments simulations by a fast and accurate multilayer perceptrons neural network model of FSS spatial filter, which is used to compute the cost (or fitness) function in the search algorithms iterations. In the FSS optimization with specific resonant frequency and bandwidth, we use: bees algorithm, continuous genetic algorithm, and particle swarm optimization. A FSS prototype is built and measured for a first level of Sierpinski island fractal. The accuracy of the proposed optimization technique is verified through the excellent agreement (0.9%) obtained by means of comparisons between theoretical and experimental results. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:827–831, 2014

A novel frequency selective surfaces (FSS) based on Y-loop fractal element is investigated using finite difference frequency domain (FDFD) method and verified with experiment in this paper. Numerical and experiment results show that the Y-loop fractal FSS has the advantages of low insertion loss in pass-band, good frequency selectivity and stability of bandwidth etc. Its performance is very stable at various incident angles and different polarization state. Besides, because over 90% of the surface covered with metal, the Y-loop fractal FSS obtains very high IR reflectivity, so the proposed FSS can also be used in MMW/IR compound system as dichroic beam combiner.