An Angularly Stable and Polarization Insensitive Miniaturized Frequency Surface for WiMAX Applications

In the paper, a tri-band angularly stable frequency selective surface (FSS) with controllable resonances for electromagnetic shielding is proposed. Different from traditional single-layer structure, the FSS proposed is based on cascaded structure that creates three adjustable blocking bands around frequency 5.93 GHz, 7.33 GHz and 9.17 GHz, respectively. The designed FSS has a low profile with thickness of λ0/100, where the λ0 represents wavelength of the first band-stop resonance frequency. Besides, the proposed FSS exhibits stable frequency response up to 70° with respect to different polarizations. Therefore, this FSS is flexible and can be used in electromagnetic shielding field where needs conformal screen. To investigate and understand the operating mechanism better, a equivalent circuit model (ECM) is deduced and given in the Section 2, the calculated results match the full-wave EM simulation results perfectly. Finally, a prototype of this FSS is fabricated and measured, the measurement results are in accordance with the simulation results.

This paper presents a novel ultrathin frequency selective surface (FSS) bandpass filter with an extraordinary wideband tailored for operating within the S-C bands. The filter structure entails a double-layer FSS structure with mutually perpendicular unit cells etched on the top and bottom sides of a 0.003λL thick FR4 dielectric substrate, where λL is the free space wavelength at the lowest operating frequency. Thus, both TE and TM polarizations can be covered, ensuring the polarization insensitivity of the structure. The two FSS layers are loaded with resistors to implement the harmonic suppression principle. The overall periodicity is extremely compact, measuring 0.16λL × 0.16λL. An equivalent circuit analysis was conducted to comprehensively evaluate the structure and provide design guidelines. Numerical simulations and experimental measurements demonstrated that the proposed filter achieved a −3 dB transmission band spanning from 2 to 6.76 GHz (fractional bandwidth equal to 108.7%) under normal incidence. Moreover, aside from excellent wideband performance, the filter showcased a flat bandpass and stable responses up to 40° of incidence angle. These remarkable capabilities position the proposed filter as a valuable asset in advancing the development of radomes and applications relevant to electromagnetic interference (EMI) shielding, promising significant contributions to the field.

A wide stop-band angular stable frequency selective surface (FSS) is presented. This FSS consist of two spiral structures separated by a substrate in the middle. It exhibits a wide stop-band of 20 GHz in the frequency range of V-band. Furthermore it produces a stable angular response upto 80 degree for both TE and TM incidence modes. Since it provides a wide stop-band and good angular stability, it is suitable for millimeter-wave shielding applications.

An optically transparent and angularly stable frequency selective surface (FSS) with a broad stopband is introduced for addressing millimeter wave (mmW) electromagnetic interference. The unique FSS unit cell pattern incorporates a cross patch with Y‐shaped branches, effectively broadening the bandwidth and enhancing the angular stability. Utilizing transparent conductive indium tin oxide deposited on both sides of a glass substrate enables the FSS to reflect and absorb electromagnetic waves. Consequently, the proposed FSS exhibits an exceptionally wide stopband ranging from 18.7 to 40.2 GHz, featuring an insertion loss of 14 dB and maintaining stable angular response up to 60° for both transverse electric and transverse magnetic polarizations. Moreover, an equivalent circuit model is developed to characterize the stopband behavior of the FSS. Finally, measurements conducted on a physical prototype of the proposed FSS validate its effectiveness, showing good agreement with the simulation results.

A compact bandstop frequency selective surface (FSS) using fractal structure is proposed. This flexuous design elongates the cell perimeter of the ring‐shaped FSS, which means the cell size gets smaller at the same resonance frequency. Furthermore, the unit cells adopt regular hexagon and the array employs equilateral triangle form. Because of its symmetric configuration, good frequency stability has been achieved for both horizontal and vertical polarizations at different oblique angles. For the stable bandstop character, this FSS can be used for protecting the staff of S‐band radars against electromagnetic radiation, while the 900/1800/1900 MHz mobile bands and the 5.2/5.8 GHz wireless local area network signals are not affected. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2541–2544, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24676

This paper presents a novel ultraminiaturized frequency selective surface (FSS) for L-band electromagnetic shielding applications. A basic square loop incorporated with folded arms in the top layer constructs the single-layer FSS design. Band-stop characteristics for the entire L-band operating frequency ranging from 1 GHz to 2 GHz are offered by the proposed design. An ultraminiaturized profile of 0.028λο × 0.028λο is achieved by the designed FSS, where λο corresponds to the lowest operating frequency, achieving at least 32.1% miniaturization when compared to the state-of-the-art FSS designs in the literature. Polarization insensitivity with a peak shielding effectiveness of 45.4 dB is manifested by the rotational symmetry of the proposed design. The proposed FSS exhibits excellent angular stability performance up to 80° with a frequency deviation of less than 1%. The equivalent circuit model helps to understand the working principle of the proposed FSS. The experimental results of the designed FSS prototype agree well with the simulation results. Hence, the proposed spatial filter is a suitable candidate for enhancing security in wireless communication at the carrier frequencies of GPS systems.

A frequency selective surface (FSS) based electromagnetic shielding structure with vent holes is proposed for 5G electromagnetic (EM) shielding. The proposed FSS structure is developed for the demanding requirements of EM shielding at 28 GHz without worsening the ventilation. Through a number of simulations using full-wave analysis, the optimized FSS achieves a bandwidth of more than 2 GHz with 30 dB shielding effectiveness. Moreover, the proposed FSS-based shielding structure has the advantage of response stability to the incident angle from 0° up to 60° for both TE and TM polarization. Results show that there is a good agreement between the measurement and the simulation.

Purpose A novel low profile frequency selective surface (FSS) with a band-stop response at 10 GHz is demonstrated. The purpose of this designed FSS structure is to reject the X-band (8-12 GHz) for the application of shielding. The proposed FSS structure having the unit cell dimension of 8 × 8 mm2, the miniaturization of the FSS unit cell in terms of λ0 is 0.266 λ0 × 0.266 λ0, where λ0 is free space wavelength. The designed FSS provides 4 GHz bandwidth with insertion loss of 15 dB. The transverse electric (TE) and transverse magnetic (TM) modes of the proposed design are same because of polarization independent characteristics and hold the angularly stable frequency response for both TE and TM mode polarization. Both the simulation and measurement results are in good agreement to each other. Design/methodology/approach The proposed FSS design contains square-shaped PEC material, which is placed on the substrate and the shape of the circle and rectangle is etched over the PEC material. The PEC material of the patch dimension is 0.0175 mm. The substrate used for the proposed design is FR4 lossy with the thickness of 0.8 mm and permittivity εr = 4.3 having a loss tangent of 0.02. Findings To find a new design and miniaturized FSS structure is discussed. Originality/value 100%

In this letter, we present a new frequency selective surface (FSS) for shielding 2.4–2.5 and 4.98–5.825 GHz wireless local area network (WLAN) bands. This FSS structure is based on the traditional Sierpinski octagon and we improve it. Compared with the traditional structure, the improved one has a smaller element size and better angular stability. The design is realized on float glass with a relative permittivity () of 8, and the unit cell size is 0.1152λ0 × 0.1152λ0 (λ0 is the free space wavelength at the first resonant frequency). Wide rejection bandwidths (−10 dB) of 910 and 1630 MHz are obtained at 2.4–2.5 and 4.98–5.825 GHz, respectively. The surface current distribution and the equivalent circuit model are illustrated to explain the resonance behavior of the proposed FSS. Furthermore, this FSS exhibits stable frequency response to incident angles of 0°–80° under transverse electric and transverse magnetic polarizations. Finally, this FSS structure was fabricated and measured. The measured results demonstrate that this FSS structure has good performance in WLAN applications.

This work presents a miniaturized angularly stable frequency selective surface (FSS) on a single layer substrate. Unit cell comprises of convoluted circular rings connected cross dipole and linear arrow headed dipole printed on both sides of the substrate. A closely spaced dual stop band resonances are obtained at 10 and 14.3 GHz with frequency ratio of 1.43. FSS shows a − 10 dB stopband bandwidth (BW) from 7.32 to 11.05 GHz (40.61%) and 12.68 to 15.97 GHz (22.97%) with >30 dB stop band rejection at center frequencies. FSS poses the features of stable performance under change in polarization and angularly stable response up to 60° incident angle. Later the proposed FSS is printed on grounded thick dielectric substrate and it shows broadband reflection type co to cross polarization conversion from 7.2 to 17.32 GHz (82.54%) with polarization conversion ratio >80% and oblique angle stability up to 35°. To the best of authors' knowledge, this is the first time in literature a single unit cell geometry with two different properties, spatial filtering on transmission and polarization conversion on reflection have been designed and analyzed in details. A finite array with size 25 × 25 of the proposed FSS is fabricated and the measured filter response shows a good agreement with simulated performance at normal and oblique incidences. The proposed FSS is used as a reflector of a dual band monopole antenna and the simulation results shows gain improvement of 5.51 and 3.8 dB at the two stopband frequencies.

Abstract-A polarization insensitive triple band-pass frequency selective surface (FSS) is proposed. The three passband of the FSS exhibits bandwidth of 35.37%, 11.86 %, 19.28 % centered at 2.68 GHz, 6.88 GHz and 10.51 GHz, respectively. The structure is designed on one side of a single-layer FR4 substrate. The insertion loss in the three bands is better than -2 dB up to an oblique incidence angle of 60 °, confirming the angular stability of the proposed FSS. The measurement carried out on the 27 x 27 array of fabricated prototype of the bandpass FSS validates the result obtained in simulation.

This article presents an ultraminiaturized frequency selective surface (FSS) for shielding 2.4 GHz and 5.8 GHz (ISM) signals. The unit cell size is 0.056λ × 0.056λ (λ is the free space wavelength at the first resonant frequency). It has smaller cell size and good transparency compared to previous ISM band studies, and transparency at 54%. The proposed FSS design consists of a wall structure and a compound square loop with 2.4 GHz and 5.8 GHz resonance frequencies for ISM band coverage. This FSS structure was fabricated on float glass with a dielectric constant of 8 by a photolithographic process. The fabricated FSS structure has excellent angular stability and polarization stability, which is further verified by experimentation. An easy optimization method is proposed to tune the independent resonant frequencies by optimizing the geometries individually. This FSS is interpreted by filtering through surface induced currents and equivalent circuit models. A prototype of the proposed FSS is fabricated and measured. The simulation results are in good agreement with the measured results. The proposed FSS has polarization insensitivity and 80∘ angle stability and is suitable for solving the EMI problem in ISM band.

A novel broadband bandpass frequency-selective surface (FSS) designed for fifth generation (5G) EMI shielding is proposed in this paper. This new design employs the vertical vias into the 2-D periodic arrays, and such a single 2.5-D periodic layer of via-based structure is demonstrated to produce a highly stable angular response up to 60° for both TE and TM polarizations. By cascading two layers of such 2.5-D periodic arrays, the proposed FSS is able to obtain a broad passband as well as the wide out-of-band rejection. Moreover, it has a quite sharp band edge between the passband and the specified stopband. A corresponding equivalent circuit model (ECM) is further developed for better analysis of the operating principle. Finally, a prototype working at the center frequency of around 28 GHz is fabricated and measured. The main novelty of this paper is introducing the 2.5-D concept into designing a wideband FSS, and further reduce the unit size as well as improve the angular stability. Favorable agreement is achieved among the 3-D full-wave simulation, ECM and measurement. All these results demonstrate that the proposed FSS is a good candidate for 5G EMI shielding.

In this research article, the superformula is used to design the geometry of a frequency selective surface (FSS) unit cell, which resembles the shapes found in nature. The designed shape of unit cell is like petals, which may take different form by varying the values of six parameters. 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 deteriorate angular and polarization stabilities. The dimensions of the unit cell are 10 mm × 10 mm and the resonance frequency is specified as 3.5 GHz. An equivalent circuit is derived for the unit cell to evaluate its frequency responses. Its performance as the transmission coefficient is obtained by the equivalent circuit and full-wave simulation. 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 equivalent circuit, full-wave computer simulation results and measured data are compared and are shown to be in good agreement.

This paper presents the design, construction and testing of grounded Frequency Selective Surface (FSS) array as millimeter wave beam splitter. The phase dependence on slot length of grounded FSS demonstrates that the reflection phase of coherent mm-wave can be altered by using FSS array with different slot lengths. A beam splitter was designed with slot FSS array where the slot length is the main design pa rameter used to optimize the ph ase properties of the array. We simulated the FSSs with commercial CST Microwave studio software, fabricated them with etching technique and characterized with a free space MVNA an d BWO with motorized detector setup. Keywords: Frequency Selective Surface, Phase delay, Beam Splitter, Random Phase pattern, Speckle contrast, Stick FSS array, Millimeter Wave technology, Coherent sources. 1. INTRODUCTION Active free-space millimeter wave (mm-wave ) systems have gained more and more attraction during the last few years due to their indoor security application [1]. There are no incoherent mm-wave sources, and coherent illumination leads to speckle due to interference phenomena [2]. Random phase mm-wave illumination patterns can reduce speckle. One of the ways to produce random phase pattern is to introduce diffe rent phase delays (i.e. time delay) in the constant phase coherent mm-wave. Our investigations demonstrate that grounded Frequency Selective Surface (FSS) can be used to design such a system to get incoherent reflection from a coherent source. To explain the random phase distribution system we made a deterministic function realization to go inside the design. The beam splitter as the deterministic function splits the reflected beam into two directions which actually helps to prove the phase delay behavior of composite FSS array. One of the motivations of this work is to overcome the limitations of commercial simulation software to simulate non-uniform infinite FSS array. The simulation of an infinite array composed of finite stick arrays is not possible with commercial software. In that case individual FSS can be si mulated and to characterize the compose array some well known function can be realized. We presented the FSS array structure which splits the coherent beam in two directions. By realizing such structure actually we in vestigated how well the phase mixing process can be achieved from such a composite array compose of finite FSS arrays. Th is paper also considers the building block of a simpler and more versatile architecture where the reflection phase varies with the slot lengths of FSS cells. Rectangular slots were etched in Aluminum on top of grounded Roge r 4003C substrate to fabricate such FSS array. Using ground plane to the back side of FSS and also by choosing the proper slot dimensions and unit cell dimensions such structure can be designed for full W-band (75-110 GHz) application[3,4]. The resonant frequency and the phase of such slotted FSSs can be controlled by using different slot lengths [4, 5]. This property of the grounded FSS is important to design a beam splitter to split the coherent of mm-wave beam. So it is a novel idea to use FSS cells with different slot lengths to control the individual phase element of a beam splitter array. The beam splitter array is an antenna array which receives coherent plane wave and reflects after phase splitting as the array introduces different phase delay in the reflected wave in a controlled way. To design such a beam splitter array differen t phase delay elements are needed. In this paper the delay elements are replaced with FSS cells of different slot lengths. Micro-strip patch with variable stub length or patch with variable size as the individual delay element for such array has unacceptably high loss due to feed network. They are not suitable for free space app lications and require tight fabrication tolerances to achieve desired phase values (i.e. phase delays), as the patch size versus phase curves are extremely non –linear [6, 7]. By using thick substrate the phase slope of such design can be reduced but the quality factor (Q) and the total phase range decreases with the increasing of thickness. As explained in [8] the dual resonant response of a two