Bandstop Frequency Selective Surface Research Articles

A Dual-Band Tunable Frequency Selective Surface With Independent Wideband Tuning

In this letter, a dual-band tunable bandstop frequency selective surface (FSS), which is capable of exhibiting independent tuning for the top and bottom layers, has been presented. The proposed design comprises periodic patterns of cross diagonals printed on the opposite sides of a thin substrate, where the varactor diodes are mounted symmetrically. Both the layers use novel biasing circuitries to independently regulate their corresponding responses, thereby resulting in two tunable stopbands. Each of these two stopbands has wide bandwidths (having fractional bandwidths of 110.71%) as well as offers large tuning ranges of 128.21% (with respect to their center frequencies). Furthermore, the geometry is low profile, polarization insensitive, and angularly stable. A prototype has been fabricated, and the varactors have been modulated through parallel biasing. The experimental results show a reasonable agreement with the theoretical responses, thus confirming the proposed concept.

Integrated Frequency Selective Surface and Antenna Printed on a Transparent Substrate

This letter presents an integrated design of a frequency modulation (FM) radio antenna and a band-stop frequency selective surface (FSS) printed on a thin and transparent glass substrate. The glass is enclosed by a rectangular aluminum frame. Such a structure can be readily applied to the windows of a car or building. The FSS is implemented with an array of cross dipoles printed using silver compound, which is able to prevent the penetration of incident 2.4 GHz signal. On the other hand, the FM antenna is also implemented on the same surface as the FSS. By joining 19 cross elements with conductive strips, the FM antenna forms a T-shaped monopole within the frame. The antenna is then fed by a 50 Ω coaxial probe and its 6 dB return loss bandwidth covers the entire FM radio channels from 87.5 to 108 MHz. The ingenious integration of the FM antenna and FSS is potentially very useful in applications that require both shielding and wireless communications, while maintaining the optical transparency at the same time.

Design of 3-D FSS with high selectivity based on ELC resonators and spoof-SPPs

The paper proposes a simple band stop frequency selective surface (FSS) design method based on spoof surface plasmon polaritons (spoof-SPPs). The novel FSS design is obtained by combing three-dimension (3-D) FSS and ultra-thin periodic corrugated metallic strip which supports spoof-SPPs. By placing electric-LC (ELC) resonators on the FSS surface at the bottom centre of the corrugated strip, the tight coupling occurs and we show that the SPP modes are rejected near the resonance frequencies of ELC resonators. The steep roll-off at both sides of the stopband can be demonstrated by the ELC resonators, which can find potential applications in wideband antenna radome. In addition, the 3-D FSS shows relatively stable performance with different oblique incidence angles.

Near-Field Shielding Analysis of Single-Sided Flexible Metasurface Stopband TE: Comparative Approach

Near-field (NF) studies comprising four common 10 GHz stopband frequency selective surfaces (FSSs) of single-sided, single-layer metasurfaces are conducted. The studies are to determine the NF efficiency of the metasurfaces for electromagnetic shielding applications. First, the FSSs' shielding performance in both far-field (FF) and NF zones is considered using the finite element method (FEM) based on the cell shielding effectiveness (SE). Analytical derivations of the FF- and NF-SE are presented, incorporating the equivalent circuit model and infinitesimal electric/magnetic source model, respectively. A nonlinear regression learning approach is utilized to predict an acceptable NF model. In the comparison study, the edge diffraction effects due to the finite structures are taken into consideration for 1-D and 2-D diffractions. The NF-SE performance of conformal structures is analyzed based on the radii of curvature. When the structure is bent, the movement of the desired transmission zero in the NF region intensely degrades the NF-SE, which may lead to a highly unstable shielding performance. Moreover, data sets are extracted for efficient usage of the structures under test by introducing two useful reconfigurable parameters, distance and radius. For verification, the FEM results are compared with the method of moment (MOM) results. The developed scenarios create a reliable criterion for further advancements of the flexible shielding surfaces from the NF point of view.

A low RCS wideband high gain CP slot antenna loaded with frequency selective surface

ABSTRACTIn this paper, a compact wideband circularly polarized slot antenna consisting of two L-shaped resonators is proposed. The slot antenna is loaded with a band-stop frequency selective surface (FSS) reflector to improve the gain of the antenna and to reduce the profile of the antenna. The radiation and scattering characteristics of FSS loaded slot antenna are compared with the metallic reflector loaded slot antenna, and the proposed antenna shows improved impedance bandwidth of 1.75–2.65 GHz. The measured results show that the peak gain of the slot antenna with FSS is enhanced by 4 dB. The proposed antenna with FSS also exhibits 3-dB ARBW of 2.2–2.65 GHz, and the scattering performance shows an average RCS reduction of 7.34 dB is achieved by slot antenna with FSS as compared to slot antenna with metallic reflector with peak RCS reduction of 24 dB at 1.2 GHz.

Design of a novel miniaturized bandstop frequency selective surface exhibiting polarization insensitivity and enhanced oblique stability

In this article, a miniaturized 2.5-dimensional frequency selective surface (FSS) bandstop filter operating at 2.4 GHz is presented. The proposed FSS contains meander lines as well as metallic patches on top and bottom layer of FR-4 substrate, and vertical vias are employed to connect the top and the bottom layers. The proposed configuration significantly reduced the size of unit cell to 0.040λ0 × 0.040λ0 (where λ0 is the free space wavelength) at the desired frequency of 2.4 GHz. Additionally, this element arrangement assists in achieving fractional bandwidth of 140%. The measured −10 dB bandwidth is from 1 to 4.5 GHz. The proposed FSS is polarization insensitive and highly angularly stable (up to 75°). The equivalent circuit model (ECM) of this FSS and related surface current distribution are also provided to understand its working mechanism. The design performance validation has been carried out through the construction and testing of a functional prototype. The full wave simulation, the ECM, and the measured results depict a promising agreement.

Frequency Selective Surface Coded Retroreflectors for Chipless Indoor Localization Tag Landmarks

This letter presents the integration of frequency selective surfaces (FSSs) with retroreflectors for the realization of chipless wireless indoor localization tag landmarks. As an example, the high radar cross section (RCS) of a trihedral corner reflector is signed with an FSS-based stopband filter, so that the backscattered power from several corner reflectors can be distinguished by a mobile reader according to the frequency response of the FSS. Measurement results with a 3 × 3 × 3 cm3 trihedral corner reflector and a stopband FSS in a Rogers RT/Duroid 5880 high-frequency laminate at 90 GHz shows an RCS above $-$ 25 dBsqm for 90° coverage in the TM plane. Due to the high RCS, measurements at distances up to 4 m with a standard 25 dBi gain horn antenna and a vector network analyzer as a reader are shown. These preliminary results show the potential of the concept for applications such as indoor localization with sub-mm accuracy, where high bandwidths, but only a low number of bits, are needed for the identification of the tag landmarks.

A Single-Layer Frequency Selective Surface With Dual Wideband Band-Stop Response

In this letter, we present a single-layer dual wideband band-stop frequency selective surface with stopbands arising from tightly coupled resonant multipole elements. The surface geometry consists of interdigitated double hexapoles with intermediate tripoles which enable both bands to exhibit wide bandwidths simultaneously. The fields are confined to independent resonance paths, providing a dual-band geometry that can be easily modified to change a resonance frequency by adjusting the corresponding arm length. Prototypes are fabricated using paper and polymer substrates and their transmission spectra are measured in an anechoic chamber. Feature sizes are limited to 0.5 mm for high repeatability using commercial screen printing processes. Measurements show that the polyethylene prototype provides 20 dB signal attenuation over a 540 MHz band at 2.14 GHz and a 500 MHz band at 5.13 GHz.

Synthesis of Ultraminiaturized Frequency-Selective Surfaces Utilizing 2.5-D Tapered Meandering Lines

An ultraminiaturized bandstop frequency-selective surface (FSS) utilizing two-dimensional (2-D) tapered meandering lines (TML) along with vertical vias is proposed. Full-wave simulations, equivalent circuit modeling, and analytical results are presented for the designed FSS. A prototype 2.5-D TML-FSS is fabricated, and its performance is measured in an anechoic chamber for various incident angles in both the transverse-electric (TE) and transverse-magnetic (TM) polarizations. Measured results are in agreement with the simulated ones, indicating the authenticity of the design process. Unit cell size of the proposed FSS is only $\text{2.9}\%$ of the free-space wavelength at resonant frequency and has a fractional bandwidth of $\text{20.9}\%$ . Furthermore, the proposed design is modified to convoluted 2.5-D TML-FSS and interdigitated 2.5-D TML-FSS to give different unit cell sizes in terms of wavelength with different fractional bandwidths.

Electrically tunable miniaturized band-stop frequency selective surface on engineered substrate with embedded permalloy patterns

This paper presents a miniaturized and electrically tunable band-stop frequency selective surface (FSS) with magneto-dielectric engineered substrate which has high and electrically tunable effective permeability. The perspective magneto-dielectric substrate is implemented with multiple layers of 100 nm thick patterned Permalloy (Py) thin film embedded in Roger RT/Duriod 5880 substrate, and each Py thin film layer consists of an array of 15μm×20μm Py patterns with 10 μm gaps among them to suppress the magnetic loss. The tunability of effective permeability for the proposed substrate is achieved by the static magnetic field produced from the applied DC current through the patterned gold bias lines beneath Py patterns. The engineered substrate has been implemented and studied, results show that the substrate embedded with a single layer of patterned Py has an equivalent permeability of 1.14 with tunability of 3.3%, and the substrate embedded with ten layers of patterned Py has an increased equivalent permeability of 2.398 and tunability of 15.8%. A magnetic FSS is designed on the implemented engineered substrate to demonstrate the efficacy of miniaturization and tunability. Compared to non-magnetic FSS on normal dielectric substrate, the size of the designed FSS has been reduced by 16.02%, and the operating frequency of the proposed FSS is continuously tunable from 2.450GHz to 2.672GHz with DC current.

Single-layer polarization-insensitive frequency selective surface for beam reconfigurability of monopole antennas

ABSTRACTIn this paper, a miniaturized single band-stop frequency selective surface (FSS) with higher order of angular stability and polarization insensitivity is utilized to reconfigure the radiation patterns of a monopole antenna, forming end-fire-like radiation patterns at 5.2 GHz. A mathematical analysis based on pattern multiplication is presented to suggest the arrangement of the FSS to achieve the end-fire-like radiation patterns from the monopole antenna. According to this analysis, the monopole radiator needs to be shielded from three sides, two parallel vertical sides and the top of the antenna. The FSS shows great angular stability with the incidence angle ranging from 0° to 80° for both TE and TM polarizations, resulting in stable end-fire-like radiation patterns when it is used with the monopole antenna. The monopole antenna along with the FSSs were fabricated and tested successfully, thus verifying the functionality of the FSSs in shaping the beam of the antenna.

Polarization independent bandstop frequency selective surface for X-band application

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%

A Novel Miniaturized Polarization Independent Band-Stop Frequency Selective Surface

A novel miniaturized frequency selective surface (FSS) with a band-stop response at 1.6 GHz is presented in this letter. The designed FSS comprises convoluted elements connected via plated-through holes, which increases the overall electrical length. The proposed FSS unit cell provides the miniaturization of 0.034 λ0 × 0.034 λ0, where λ0 is the free space wavelength corresponding to the resonant frequency. The drafted FSS is polarization independent and angularly stable for both TE and TM polarizations. A prototype of the FSS is fabricated and its simulated results are validated with measurements.

Design of Compact Polarization Insensitive Triple Bandstop Frequency Selective Surface with High Stability under Oblique Incidence

Design of Compact Polarization Insensitive Triple Bandstop Frequency Selective Surface with High Stability under Oblique Incidence

Study of 5.8 GHz Band-Stop Frequency Selective Surface (FSS)

This paper presents the study of 5.8 GHz frequency selective surface (FSS) acts as a band stop to eliminate unwanted radiation signal at 5.8GHz. The FSS was designed using computer simulation technology (CST) Microwave Studio software. The paper shows the comparison of square loop, octagon loop and hexagon loop of Band stop FSS (BSFSS) performance at 5.8 GHz. Besides, the BSFSS design using four different type of dielectric substrate such as FR-4, TLY-5, Roger RT5870 and Roger RT5880 were compared. The results obviously show that the Rogers RY5880 has the attenuation -44.72 dB. The fabricated FSS were measured by using free space technique with two horn antennas connected to performance network analyzer (PNA). The measured and simulated results were compared. The results show that the square loop FSS structure have the better attenuation -26.76 dB (simulated) and -38.34 dB (measured) at 5.8 GHz.

Polarization-Insensitive and Angularly Stable Compact Ultrawide Stop-Band Frequency Selective Surface

In this letter, a compact ultrawide stop-band frequency selective surface (FSS) with polarization-insensitive and higher level of angular stability property is presented. It consists of a very simple modified square-ring unit cell that exhibits excellent wideband rejection over the entire ultrawideband (UWB) 2.72–13 GHz range. For TE incident wave, the λ0 × 0.066 λ0 × 0.013 λ0 ) compared to the earlier reported UWB FSSs is printed on a single-layer single-sided FR4 substrate. The design is flexible enough to tune the desired resonant frequency and the operating band by changing the length and width of the resonators. The design concept has been validated through proper measurement. This FSS can be used as a good reflector to enhance the gain of UWB antennas.

Flexible Serpentinelike Frequency Selective Surface for Conformal Applications With Stable Frequency Response

In this letter, a flexible stopband frequency selective surface (FSS) with serpentine stripe unit cell is presented. Compared with the FSS with straight stripe and zigzag stripe unit cell, the proposed FSS on planar thin polyimide (PI) substrate shows very small offset of resonant frequency with electromagnetic waves having incident angles from 0 $^\circ$ to 60 $^\circ$ , according to the simulation results. The stable transmission performance of flexible FSS with serpentine stripe unit cell on PI substrate is further demonstrated by the computational and experimental results. When the FSS with serpentine stripe unit cell is bent with bending angles from $ \pi /3$ to $ \pi$ , the offset of resonant frequency is negligible, whereas the resonant frequency of FSS with straight stripe and zigzag stripe unit cell shifts about 15.4% and 5.8% when bending angle is $ \pi$ , respectively.

Double Layer Frequency Selective Surface for Ultra Wide Band Applications with Angular Stability and Polarization Independence

In this paper, a double layer stopband Frequency Selective Surface (FSS) for Ultra-Wide Band (UWB) applications is presented. The proposed FSS consists of two cascaded conventional FSS, one with double square loops and other with square loops. The − 10dB frequency band from 3.00 GHz to 11.64 GHz is achieved, with a fractional bandwidth of 149 %. Effects of angular stability and polarization independence over the frequency response are investigated and conclusions are presented. In order to show transmission performance, the FSS was simulated by ANSYS HFSS. The FSS shows angular stability and polarization independence in entire UWB band (3.10 – 10.60 GHz). A prototype was built and measurements were performed. A good agreement between simulated and measured results was observed.

Dual‐band, dual‐polarized, and compact frequency selective surface

In this article, a compact, dual-band, dual-polarized band pass single-layered frequency selective surface (FSS) structure with stable performance in wide incident angles is designed and fabricated. This structure is designed with a new proposed approach which is the combination of miniaturized-element band stop FSS and high pass grid FSS. For this purpose, a new compact band stop structure is introduced and miniaturized by adding vertical metalized holes (vias) in the substrate as additional capacitive. A WLAN band stop FSS is designed also as an example of the proposed miniaturized-element. Then, this band stop FSS is combined with a simple high pass grid structure to design the proposed band pass FSS. The circuit models of these FSSs are also extracted to achieve better description of the structures and combination idea. The dimensions of the final designed compact band pass FSS structure is 0.048λ × 0.048λ where λ is the free space wavelength of the first resonance frequency. The fabrication results of this FSS which works at WLAN bands are in good agreement with the simulation ones which prove the design approach.

Novel Angular and Polarization Independent Band-Stop Frequency Selective Surface for Ultra-Wide Band Applications

Novel Angular and Polarization Independent Band-Stop Frequency Selective Surface for Ultra-Wide Band Applications