Prototype Of Frequency Selective Surface Research Articles

An Improved Multifunctional Active Frequency Selective Surface

An improved dual-polarized multifunctional active frequency selective surface (MAFSS) with parallel-feed configuration is proposed in this paper. The designed structure is composed of two metallic layers separated by a thin dielectric layer. Three independent and controllable functions of electromagnetic switching, polarization selection, and frequency tuning are integrated together into the proposed structure via introducing PIN diodes and varactor diodes. To reduce the negative effects of extra feed lines, frequency selective surface (FSS) elements themselves play a significant role in connecting the active components and allowing the direct currents to flow through. A special biasing configuration is designed to provide parallel bias voltages for the two different types of active devices. Finally, an FSS prototype is fabricated and measured, and the measurement results as well as the simulation results both demonstrate great performance of the MAFSS structure. In addition, the proposed structure also performs well under circumstances of oblique incidence and different polarizations.

Polarization independent dual-bandpass frequency selective surface for Wi-Max applications

In this article, the performance of polarization independent dual-bandpass frequency selective surface (FSS) is investigated. The proposed design of FSS unit cell comprises of metallic structure is based on customized plus shape within plus ring inside a square ring and etched on one side of FR4 substrate. The geometrical dimensions of unit cell are optimized in such a way that the structure possesses the dual-bandpass characteristic for Wi-Max applications. The aspect dimensions of unit cell are 0.16 λ × 0.16 λ × 0.013 λ with respect to first resonant frequency. The FSS provide stable response for different angle of incidence in transverse electric and transverse magnetic polarization. An equivalent circuit model of FSS is established and its results are verified by Advanced Design System tool. A prototype of FSS is designed, fabricated and measured. Good agreement between simulated and measured results verifies the dual-bandpass FSS.

A Low-Profile Broadband Bandpass Frequency Selective Surface With Two Rapid Band Edges for 5G Near-Field Applications

A low-profile broadband bandpass frequency selective surface (FSS) with two rapid band edges is proposed in this paper for 5G near-field applications. The overall structure consists of three metallic layers, separated by two thin substrates with a thickness of 0.07λ. In addition, some centro-symmetric miniaturized slots are introduced in the middle metallic layer to further improve its stability and reduce its physical dimensions. A corresponding equivalent circuit model (ECM) is also proposed to better analyze the principles of the proposed FSS. Finally, an FSS prototype working at the center frequency of 27.5 GHz with a relative -3 dB bandwidth of 20.5% is fabricated and measured. More than 25 dB shielding effectiveness can be obtained out of the passband for a bandwidth of 1.46 GHz in this experiment. Both 3-D full-wave simulations and ECM results are in good agreement with the experimental results, having a maximum deviation of only 2.257% in the transmission zeros and poles. These results demonstrate that the proposed FSS is a good candidate for 5G near-field EMI shielding.

An Angularly Stable Dual-Band FSS With Closely Spaced Resonances Using Miniaturized Unit Cell

A novel miniaturized-element dual-band frequency selective surface (FSS) with closely spaced resonance is presented in this letter. The proposed FSS comprises of meander lines printed on a single-layer dielectric substrate to provide dual stopband characteristic. Compared to previously published spatial filters, the proposed FSS has better miniaturization characteristic having the unit-cell size of $0.065\lambda _{0} \times 0.065\lambda _{0}$ , where $\lambda _{0}$ corresponds to free space wavelength of the lower resonance frequency. In addition, the operating bands are closely located exhibiting the frequency ratio as low as 1.29. The surface current distribution and the equivalent circuit model are illustrated to explain the resonance behavior of the designed FSS. Furthermore, the proposed structure is polarization-independent and angularly stable for both TE and TM polarizations. A prototype of the dual-band FSS is fabricated and measured, which validates the simulated responses under normal and oblique incidence.

Tunable square slot FSS EC modelling and optimisation

An equivalent circuit model for tunable square slot frequency selective surfaces (FSS) is proposed. Tuning is achieved with the inclusion of a discrete capacitance element, at key points within the FSS unit cell. The equivalent circuit model takes into account the FSS physical attributes. The performance of the proposed equivalent circuit model was evaluated against results obtained from appropriate electromagnetic simulations. Results demonstrate the validity of the proposed equivalent circuit model, in which good estimations of the frequency response of FSS structures were obtained. A RMSE value of 190 MHz was extracted from the complete parametric simulation set. The model was further validated against measurements performed on a tunable active FSS prototype inside an anechoic chamber. Tuning of the FSS was achieved by means of bias voltage to modify the varicaps capacitance value. A relatively good agreement was verified between equivalent circuit model, electromagnetic simulations and measurements. Finally, this work is sought to be a useful contribution to the literature on this topic, by improving on the elementary models of such FSS structures and be useful as a good and fast first approach to determine approximate FSS unit cell dimensions.

A Miniaturized Triband Frequency Selective Surface Based on Convoluted Design

A novel miniaturized tri-band frequency selective surface (FSS) based on convoluted design has been proposed in this letter. The proposed FSS is a low-profile structure, and it is composed of two periodic metallic arrays separated by a thin dielectric substrate. The top metallic array is composed of four branched spiral triangles connected in the center, and the bottom one is consisting of gridded tortuous cross-dipole. The proposed FSS can provide three passbands operating at 3.28, 4.2, and 5.4 GHz, respectively. The unit cell is only 0.066 λ 0 × 0.066 λ 0 in size, where λ 0 is the wavelength of the first resonant frequency in free space. In addition, the proposed FSS provides a stable performance under oblique incidence for both TE and TM polarizations. For verification, an FSS prototype has been fabricated and measured. Good agreements between the simulated and the measured results can be observed.

Square Loop and Slot Frequency Selective Surfaces Study for Equivalent Circuit Model Optimization

This paper presents a parametric study of square loop and square slot frequency selective surfaces (FSSs) aimed at their equivalent circuit (EC) model optimization. Consideration was given to their physical attributes, i.e., the unit cell dimensions and spacing, substrate thickness and dielectric properties, for several frequencies and plane wave incident angles. Correlation analysis and evaluation of the influence of physical related input parameters on the FSS performance are presented. Subsequent optimization factor for the square loop classical EC model is analyzed, and a novel EC model formulation for the square slot FSS is proposed. The performance of the proposed EC model was assessed against results obtained from appropriate electromagnetic (EM) simulations, based on a root-mean-square error (RMSE) criteria. Results demonstrate the validity of the optimized EC model, in which good estimations of the frequency response of FSS structures were obtained. Significant reduction of the resonant frequency offsets, in the order of 650 (from 910 to 260) and 460 (770 to 310) MHz, was obtained for square loops and square slots, respectively. The models were further validated against measurements performed on two physical FSS prototypes inside an anechoic chamber at 2.4 GHz. Relatively good agreement was obtained between measurements of real FSS prototypes and results obtained with the EC model. Finally, this work is sought to provide the necessary refinement of elementary models for further studies with more complex and novel FSS structures.

A Novel 2.5-Dimensional Ultraminiaturized-Element Frequency Selective Surface

This paper proposes fabricating a new 2.5-dimensional ultraminiaturized element on a cost-effective printed circuit board to build a frequency selective surface (FSS). The proposed element consists of two main parts: a planar tapered meandering line (PTML) and a vertical via-based meandering line (VVML). Compared with previous published two-dimensional miniaturized elements, the proposed element is smaller (only 3.3% of the free space wavelength at the resonant frequency) and exhibits high resonant stability at various polarizations and incidence angles (only 0.4% deviation at the resonant frequency when the incident angle is as great as 75°). In particular, the introduction of VVML in the element substantially improves the FSS performance. A third-order equivalent circuit model was established to model the FSS performance precisely. This model can be reduced to a simpler first-order model, thus enabling the resonant frequency of the FSS to be predicted quickly. A prototype of the ultraminiaturized-element FSS was created and examined. The results of the proposed models, full-wave simulation, and measurement exhibited satisfactory consistency.

Optimal design of frequency selective surfaces with fractal motifs

An alternative electromagnetic (EM) optimisation technique for the optimal design of frequency selective surfaces (FSSs) with fractal motifs is described. Based on computational intelligence tools, the proposed technique overcomes the high computational cost associated with FSS parametric full-wave analysis. In an application example, a fast and accurate multilayer perceptrons model of a FSS band-stop spatial filter with a Vicsek fractal motif is developed. This neural network model is used for repetitive cost function computations in population-based search algorithm simulations. A bees algorithm, continuous genetic algorithm and particle swarm optimisation are used for FSS optimisation with specific resonant frequency and bandwidth. The performance of these algorithms is compared in terms of numerical convergence. Consistent results are presented for a second-pass of designed FSS prototype with Vicsek fractal elements.

Optimization of FSS with Sierpinski island fractal elements using population-based search algorithms and MLP neural network

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

An iterative full‐wave method for designing bandstop frequency selective surfaces on textile substrates

ABSTRACTThis work presents an investigation of frequency selective surfaces (FSSs), with cross dipole, square loop, and triangular patch elements printed on textile substrates which exhibit some advantages over typical dielectric substrates used in FSS structures, such as high flexibility, low weight, low cost, and ease fabrication. Among these advantages, flexibility is certainly the most important one, allowing the FSS geometry to be used in many microwave circuit applications. Simulated results are obtained using both an implementation of the wave concept iterative procedure and Ansoft Designer commercial software for comparison purpose. Furthermore, textile FSS prototypes are built and measured to validate the simulated results. Good agreement is reported between simulated and measured results. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:383–388, 2014

Multiband Frequency Selective Surfaces with Simple Modification of a Rectangular Patch Element

ABSTRACTA simple modification in a rectangular patch element is exploited to design frequency selective surfaces (FSS) for multiband bandstop filter operation. The use of the modified rectangular patch elements enables the adjustment of FSS parameters (resonant frequency and −10‐dB bandwidth) according to the length and position of the slot but without modifying their original size. Transmission properties of proposed FSS are characterized by means of simulations and measurements. Four FSS prototypes were fabricated and measured. The obtained results show an interesting multiband behavior. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:2943–2946, 2013

Dual‐band bandstop frequency selective surfaces with gosper prefractal elements

AbstractSelf‐similarity property of Gosper island prefractals is exploited to design frequency selective surfaces (FSSs) for dual‐band bandstop filter operation. The use of Gosper prefractal patch elements enables the adjustment of FSS parameters (resonant frequency and −10 dB bandwidth) according to the number of fractal iterations but without modifying their original size. Transmission properties of proposed FSSs are characterized by means of simulations and measurements. Four FSS prototypes were fabricated and measured. The obtained results show an interesting dual‐band behavior. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:771–775, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26663

A Generalized Synthesis Procedure for Low-Profile, Frequency Selective Surfaces With Odd-Order Bandpass Responses

We present a generalized synthesis procedure for designing low-profile frequency selective surfaces (FSS) with bandpass responses of odd-order (N = 3,5,7,...). The FSSs designed using this technique use a combination of resonant and non-resonant sub-wavelength constituting unit cells with unit cell dimensions and periodicities in the order of 0.15 λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> , where λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> is the free space wavelength. The main advantage of using this technique, compared to traditional FSS design techniques, is that it allows for the design of low-profile and ultrathin FSSs that can provide sharp frequency selectivity. An Nth order FSS designed using this technique typically has an electrical thickness in the order of ~ (N - 1) λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> /50 which is significantly smaller than the overall thickness of a traditionally designed Nth order FSS (~ (N - 1) λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> /4). The proposed synthesis procedure is validated for two FSS prototypes having third- and fifth-order bandpass responses. Principles of operation, detailed synthesis procedure, and implementation guidelines for this type of FSS are presented and discussed in this communication.

A New Technique for Design of Low-Profile, Second-Order, Bandpass Frequency Selective Surfaces

In this study, a new method for designing low profile frequency selective surfaces (FSS) with second-order bandpass responses is presented. The FSSs designed using this technique utilize non-resonant subwavelength constituting unit cells with unit cell dimensions and periodicities in the order of 0.15lambda <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> . It is demonstrated that using the proposed technique, second-order FSSs with an overall thickness of lambda <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> /30 can be designed. This is considerably smaller than the thickness of second-order FSSs designed using traditional techniques and could be particularly useful at lower frequencies with long wavelengths. To facilitate the design of this structure, an equivalent circuit based synthesis method is also presented in this paper. Two bandpass FSS prototypes operating at X-band are designed, fabricated, and tested. A free space measurement setup is used to thoroughly characterize the frequency responses of these prototypes for both the TE and TM polarizations and various angles of incidence. The frequency responses of these structures are shown to have a relatively low sensitivity to the angle of incidence. Principles of operation, detailed design and synthesis procedure, and measurement results of two fabricated prototypes are presented and discussed in this paper.

A Novel Miniaturized-Element Frequency Selective Surface Having a Stable Resonance

In this letter, we propose a miniaturized periodic element for constructing a band-pass frequency selective surface (FSS) that demonstrates an excellent resonance stability performance with respect to different polarizations and incidence angles. In contrast to traditional periodic elements with sizes comparable to a half of the wavelength at the resonant frequency, the size of the proposed element is reduced highly to only a tenth-wavelength. We created and examined a prototype of the miniaturized-element FSS. Both the simulated and measured results obtained demonstrate the claimed performance.