Proposed Frequency Selective Surface Structure Research Articles

A Quad-Band Highly Selective Frequency Selective Surface with Ultra-Wideband Rejection.

In this paper, a highly selective quad-band frequency selective surface (FSS) with ultra-wideband rejection is presented. The proposed FSS structure was developed by cascading five metallic layers by three thin dielectric substrates. The five metallic layers are composed of two bent slot layers, two metallic square rings, and a metal patch. The dimensions of the unit cell are 0.13λ0× 0.13λ0× 0.18λ0 (λ0 is the free-space wavelength at the first operating frequency). The proposed structure achieves four transmission bands and has two wide stop-bands located at 1 to 5.5 GHz and 14 to 40 GHz, with a suppressed transmission coefficient below -20 dB. In order to verify the simulation results, an FSS prototype was fabricated and measured. It can be observed that the measured results are in favorable agreement with the simulation results. Its multiple narrow passbands and highly selective and ultra-wideband rejection properties ensure that our design can play a significant role in narrowband antennas, spatial filters, and many other fields.

A Proposed Frequency Selective Surface (FSS) using Bio-Inspired Element for Wi-Fi 6E Applications

Recently bio-inspired elements with shapes or geometries found in nature have received special attention, both for applications in antennas and in electromagnetic filters, the unit cell of the proposed FSS consists of a modification in a bio-inspired shaped element. A single and multilayered band-stop Frequency Selective Surface (FSS), with polarization independence, is proposed to be used in frequency applications at 6.0 GHz (Wi-Fi 6E). In the industry, Wi-Fi 6E is the name that identifies those Wi-Fi devices that operate in the 6.0 GHz band, designed to improve efficiency and more capacity than previous standards. Band-stop frequency responses for the single and multilayer structures are presented. The simulated frequency responses show bandwidth values for inhibit transmission about of 1.75 GHz and 3.15 GHz, respectively for single and multilayer structures. Furthermore, good agreement between simulated and measured results is shown for the single bio-inspired FSS. The proposed FSS structure presents features that allow its use as an electromagnetic filter or its integration with microstrip antennas developed for applications in the same standard.

A triple‐band frequency selective surface for 5G millimeter‐wave communications

AbstractIn this letter, a new triple‐band millimeter‐wave frequency selective surface (FSS) is presented. The proposed FSS structure consists of three slot‐based resonance mechanisms on the single layer of Rogers Diclad880 dielectric. It shows a high compactness with a unit cell surface area of 5.4 × 5.4 mm2. The proposed FSS exhibits a triple‐band bandpass filter characteristics for the allocated 5G millimeter‐wave frequency regions with sufficient bandwidths corresponding to 23.5–24.6, 27–28.5, and 37.5–41 GHz, respectively. Simulation outcomes reveal that the FSS poses polarization insensitive behavior, and maintains high transmission skill for a wide range of incident angles up to 40°. A 40 × 40 FSS panel is fabricated, and the experimental verification is carried out. The outcomes prove that the proposed FSS is suitable for multiband 5G millimeter‐wave filtering applications.

Bandwidth and Gain Enhancement of a CPW Antenna Using Frequency Selective Surface for UWB Applications

In this article, a single-layer frequency selective surface (FSS)-loaded compact coplanar waveguide (CPW)-fed antenna is proposed for very high-gain and ultra-wideband applications. At the initial stage, a geometrically simple ultra-wideband (UWB) antenna is designed which contains CPW feed lines and a multi-stub-loaded hexagonal patch. The various stubs are inserted to improve the bandwidth of the radiator. The antenna operates at 5-17 GHz and offers 6.5 dBi peak gain. Subsequently, the proposed FSS structure is designed and loaded beneath the proposed UWB antenna to improve bandwidth and enhance gain. The antenna loaded with FSS operates at an ultra-wideband of 3-18 GHz and offers a peak gain of 10.5 dBi. The FSS layer contains 5 × 5 unit cells with a total dimension of 50 mm × 50 mm. The gap between the FSS layer and UWB antenna is 9 mm, which is fixed to obtain maximum gain. The proposed UWB antenna and its results are compared with the fabricated prototype to verify the results. Moreover, the performance parameters such as bandwidth, gain, operational frequency, and the number of FSS layers used in the proposed antenna are compared with existing literature to show the significance of the proposed work. Overall, the proposed antenna is easy to fabricate and has a low profile and simple geometry with a compact size while offering a very wide bandwidth and high gain. Due to all of its performance properties, the proposed antenna system is a strong candidate for upcoming wideband and high-gain applications.

An FSS structure with a band‐stop performance for UWB applications

AbstractIn this paper, a frequency selective surface (FSS) structure with a band‐stop performance for ultra‐wideband (UWB) applications is introduced. The unit cell of the FSS structure consists of a combination of a square loop, a ring loop, and a cross dipole with four gaps. The unit cell has 0.115λg × 0.115λg size where λg is the wavelength in the substrate corresponding to the minimum frequency (2.79 GHz) of the operating band. The bandwidth of the FSS design is from 2.79 to 10.81 GHz frequencies (at normal incidence and |S21| < −3 dB criterion) which covers all UWB bands. The introduced FSS structure has angular stability up to 80° incident angles both TM and TE polarizations due to the small size of the unit cell. The highest resonance frequency deviation is 0.08% at 80° and this value is quite low. The proposed FSS structure was fabricated and the results obtained through simulations were supported by the measurement results.

Design of miniaturize flexible wideband frequency selective surface for electromagnetic shielding application

In this paper, a flexible, ultra-thin, miniaturized broadband frequency selective surface (FSS) is demonstrated for wideband electromagnetic shielding application. The unit cell of the proposed FSS structure consists of cross dipoles loaded with the metallic circular strip. The proposed miniaturized FSS structure has an extremely low profile with a thickness of and a unit cell size of . This FSS structure provides wideband shielding of more than 20 dB from 1.1 to 2.6 GHz frequency region. Besides this wide stopband, the FSS structure acts as a transparent window in the frequency band which can be used for the 5G communication purpose. Moreover, by comprehending the interaction between the incident electromagnetic wave and unit cell, a conceptual equivalent circuit model is developed that helps to interpret the mechanism of the miniaturization as well as the broadband response of FSS structure. We also compared the proposed FSS with other recently reported structures and observed more than 55% improvement in size reduction with several other miniaturized flexible FSS structure. Furthermore, this FSS structure exhibits 20 dB attenuation over a wide frequency region with a fractional bandwidth of 111%. Moreover, excellent resonant stability is achieved in regards to different polarization and incident angle up to .

A Wideband High-Gain Microstrip Array Antenna Integrated with Frequency-Selective Surface for Sub-6 GHz 5G Applications.

This paper presents a wideband and high-gain rectangular microstrip array antenna with a new frequency-selective surface (FSS) designed as a reflector for the sub-6 5G applications. The proposed antenna is designed to meet the US Federal Communications Commission (FCC) standard for 5G in the mid-band (3.5–5 GHz) applications. The designed antenna configuration consists of 1 × 4 rectangular microstrip array antenna with an FSS reflector to produce a semi-stable high radiation gain. The modeled FSS delivered a wide stopband transmission coefficient from 3.3 to 5.6 GHz and promised a linearly declining phase over the mid-band frequencies. An equivalent circuit (EC) model is additionally performed to verify the transmission coefficient of the proposed FSS structure for wideband signal propagation. A low-cost FR-4 substrate material was used to fabricate the antenna prototype. The proposed wideband array antenna with an FSS reflector attained a bandwidth of 2.3 GHz within the operating frequency range of 3.5–5.8 GHz, with a fractional bandwidth of 51.12%. A high gain of 12.4 dBi was obtained at 4.1 GHz with an improvement of 4.4 dBi compared to the antenna alone. The gain variation was only 1.0 dBi during the entire mid-band. The total dimension of the fabricated antenna prototype is 10.32 λo × 4.25 λo ×1.295 λo at a resonance frequency of 4.5 GHz. These results make the presented antenna appropriate for 5G sub-6 GHz applications.

A Hybrid 2-D–3-D Miniaturized Multiorder Wide Bandpass FSS

In this letter, a hybrid multiorder wide bandpass frequency selective surface (FSS) with high selectivity and low insertion loss is achieved by combining the two-dimensional (2-D) FSS structure and the 3-D vertical structure. The 3-D periodic vertical printed circuit board pieces (PVPCB) are used as the dielectric layer in the unit cell to achieve a proper band flatness without introducing great insertion loss. The multiorder response of the proposed FSS is achieved using a series of 3-D PVPCB instead of stacking the 2-D FSS layers. The proposed FSS unit cell is constructed by combining the full-wave and equivalent circuit simulations, since the physical structures have a good one-to-one correspondence with the circuit elements. The module design method is used to accelerate the design procedure, and the simulation result proves the effectiveness of this design method. Finally, the prototype is fabricated and measured to prove the effectiveness of the proposed FSS. The measured relative bandwidth and rectangle coefficient achieved is 130.4% and 0.76, respectively. The measured maximum insertion loss over the whole passband is 0.7 dB. Because of its strong capability of out-of-band rejection, the proposed FSS structure is a good candidate to enhance high-frequency electromagnetic pulse protection of wideband radar systems.

A simple frequency selective surface structure for performance improvement of ultra‐wideband antenna in frequency and time domains

This article demonstrates a new type of annular ring shaped cylindrical dielectric resonator (ARCDR) loaded printed ultra-wideband (UWB) antenna which is further loaded with a new type of two-layer UWB frequency selective surface (FSS) structure. The proposed FSS helps to improve the peak gain of the standalone hybrid antenna significantly (about 4.45 dB). The proposed FSS loaded hybrid antenna provides measured impedance bandwidth (IBW) and measured peak gain about 115.5% (S11 ≤ −10 dB, 3.75 to 14 GHz) and 10.3 dBi respectively. The top layer of FSS structure employs a square loop configuration integrated with “+” sign, staged in 45° angle. Bottom layer of FSS consists of a square loop. The standalone proposed FSS structure also provides large transmission (S21 ≤ −10 dB, 108%, measured) bandwidth (BW) from 3.5 to 11 .75 GHz. The behavior of the proposed UWB antenna geometry has been studied in both frequency and time domains. The newly proposed FSS structure and integrated antenna have been fabricated and there is a close agreement between the simulated and the measured performances.

Design and Analysis of Frequency Selective Surface for Ism and Lower Ultra-Wideband Antenna

A Compact, dual-layer Frequency Selective Surface (FSS) is presented for electromagnetic shielding applications. The square loop FSS is modified to provide band rejection characteristics for ISM band and lower Ultra-Wide Band (UWB) covering from 2.2 GHz to 7.1 GHz with the bandwidth of (S21 < -20dB) 4.9 GHz. The novel design exhibits symmetric property due to which it achieves polarization-insensitive stable band rejection of the desired frequency band for various angles of incidences up to 60°. The proposed FSS structure has compact dimensions of 0.170λ x 0.170λ x 0.0117λ. The design was fabricated on either side of the substrate made of FR-4 with a dielectric constant of 4.4 and loss tangent of 0.02. The measured results are well per the simulation results. The proposed FSS in this paper has various applications, including the aerospace industry, hospitals, random, and in the scope of electromagnetic filters, etc.

Angle and polarization-independent miniaturized UWB FSS design

AbstractA single-layer ultra-wideband (UWB) stop-band frequency selective surface (FSS) has several advantages in wireless systems, including a simple design, low debugging complexity, and an appropriate thickness. This study proposes a miniaturized UWB stop-band FSS design. The proposed FSS structure consists of a square-loop and metalized vias that are arranged on a single layer substrate; it has an excellent angle and polarization-independent characteristics. At an incident angle of 60°, the polarization response frequencies of the transverse electric and magnetic modes only shifted by 0.003 f0 and 0.007 f0, respectively. The equivalent circuit models of the square-loop and metallized vias structure are analysed and the accuracy of the calculation is evaluated by comparing the electromagnetic simulation. The 20 × 20 array constitutes an FSS reflector with a unit size of 4.2 mm × 4.2 mm (less than one-twentieth of the wavelength of 3 GHz), which realizes an UWB quasi-constant gain enhancement (in-band flatness is &lt;0.5 dB). Finally, the simulation results were verified through sample processing and measurement; consistent results were obtained. The FSS miniaturization design method proposed in this study could be applied to the design of passband FSS (complementary structure), antennas and filters, among other applications.

Design and analysis of ultrathin X‐band frequency selective surface structure for gain enhancement of hybrid antenna

A wideband ultrathin frequency selective surface (FSS) structure is designed and developed for the complete X-band. The design employs a metallic tetra-arrow (two bidirectional arrows placed diagonally) and a circular split structure (metallic) in the top side and bottom side of RT duroid 5880LZ low-loss substrate respectively. The proposed design has novel contribution in terms of significant reduction in electrical thickness (0.007λ0 which is corresponding to lowest operating frequency, 8.3 GHz) and wider transmission (S21) bandwidth (measured: S21 ≤ − 10 dB, 8.15-13.2 GHz, 47.3%), covering entire X-band due to cumulative loading of surface mount chip resistors in the top layer. The principle of operation of the proposed FSS further can be justified with its equivalent transmission line circuit model, which is based on microwave filter (band-stop and band-pass) topology for anticipating the desired characteristics. The FSS structure is further integrated with dielectric resonator (DR)-slot hybrid antenna for enhancing the gain (measured: peak gain of 4.5 dBi without FSS and 7.8 dBi with FSS) of the antenna. The proposed FSS structure is fabricated and measured performance has very similar responses as simulated ones.

Tripole type wideband bandpass frequency selective surface for X‐band applications

The study presents a novel single dielectric layer wideband bandpass frequency selective surface (FSS) topology. The structure is designed using a kind of the tripole type FSS which has been analysed for its behaviour. Next, the operating bandwidth has been increased by using the meander lines in the middle of the unit-cell. The proposed FSS structure covers the X-band (45.03% fractional bandwidth) of the electromagnetic (EM) spectrum with a −3 dB transmission bandwidth. Its −1 dB bandwidth extends from 7.93 to 11.93 GHz. The wide operating bandwidth with a single dielectric layered structure makes it suitable for the hybrid radome applications. For the normally incident EM wave, adjacent to the lower and upper cut-off frequencies, the structure offers better than 18 dB attenuation which increases the out of the band rejection. Finally, the proposed structure is fabricated and experimentally verified for the dual polarisation and angle stability up to 45°. Eventually, to prove the novelty in terms of the operating bandwidth and the fabrication simplicity, an exhaustive state-of-the-art comparison is also presented.

Popup Tunable Frequency Selective Surfaces for Strain Sensing

A 3-D popup frequency selective surface (FSS) is presented that can be tuned by the amount of strain due to mechanical loading in its elastomeric substrate. The proposed FSS structure comprises periodic 2-D crossed dipoles attached to the substrate at selective bonding sites. Strain release in the substrate induces compressive stress in the attached FSS, converting it to a 3-D periodic pattern. With the out-of-plane displacement, the interaction with the incident field and mutual interactions between the elements are altered, resulting in a resonant frequency shift and a more stable response regarding the incident angles from 0° to 45°. A design of popup FSS structure is introduced for strain sensing applications. The potential sensor can measure up to 50% strain in the substrate by frequency down-shift from 3.1 to 2.4 GHz. Multiphysics finite element method modeling of the mechanical and RF simulation was in good correlation with the experimental data and demonstrates the potential of these structures as sensors.

A Flower Shaped Frequency Selective Surface for WLAN Screening Applications

This communication presents a single flower shaped resonator frequency selective surface (FSS) unit cell with stable oblique angles of incidence for both horizontal and vertical polarizations. The proposed FSS structure which can impede the frequencies from 3GHz to 6GHz at 3dB insertion loss is presented. The proposed FSS comprise an improved decagon to form a flower-shaped structure that exhibits single narrow stop band characteristics. The flower shaped FSS acts like a band-stop filter with center frequency of 4.8 GHz and notch band frequency ranging from 4.2GHz to 5.3GHz at 10dB insertion loss and 320MHz bandwidth at 20dB insertion loss. The designed FSS can use for shielding of public safety WLAN frequency. We present the equivalent circuit model and the surface current distribution to illustrate the resonance characteristics of the miniaturized FSS. To validate the design and simulation results, the proposed FSS is fabricated and tested in a semi-anechoic chamber

Convoluted FSS Structure For Shielding Application In X-Band Frequency Response

A compact single-layer frequency-selective surface (FSS) covering X-band frequency range for shielding application is presented in this study. The proposed FSS structure, constructed with a convoluted element printed on both sides of FR4 material, exhibits band-stop response covering a frequency spectrum of 8–12 GHz at 10 dB level of insertion loss. The designed FSS provides polarization-independent performance and good angular stability. The simulated result and the measured results seem to be in a good agreement.

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%

Mutual Coupling Reduction for Ultra-Dense Multi-Band Plasmonic Nano-Antenna Arrays Using Graphene-Based Frequency Selective Surface

Terahertz (THz) band provides huge bandwidth but the molecular absorptions in these frequencies cause high path losses in long-distance communications. Recently, multi-band ultra-massive MIMO (UM-MIMO) systems based on graphene-based plasmonic nano-antennas have been proposed to overcome the distance problem. In the UM MIMO systems, the mutual coupling effect is a challenging problem because of the ultra-dense integration of the multi-band nano-antenna arrays. In this paper, a graphene-based frequency selective surface (FSS) is proposed to reduce the coupling effects in dense plasmonic nano-antenna arrays for multi-band UM MIMO systems. The performance of the proposed structure is evaluated by full-wave simulation for different cases. The results show that the FSS structure has a wide stopband (-15 dB bandwidth, approximately 43%-50%) from 1.1 to 1.7 THz. By inserting the FSS structure between nano-antennas, a high isolation coefficient of -25 dB with a 15 dB fall and an envelope correlation coefficient of less than 0.01 are achieved. The field distributions and the radiation patterns are also presented to confirm that the proposed FSS structure improves the performance of the array with negligible influence on the antenna itself. Moreover, the receiving mode simulation of the array is performed with the FSS structure. It is also asymptotically shown that the mutual coupling experienced by the nano-antenna with the FSS structure is negligible even in the presence of a very large number of closely integrated elements. Finally, the technological issues are discussed for practical implementations.

High efficient linear polariser using FSS structure

A linear polarisation converter surface with broadband and high-efficiency properties is proposed. The proposed frequency selective surface (FSS) polariser consists of two-corner-cut diagonal rectangular printed on a substrate backed by a pinwheel loop shape ground. The combination of two-corner-cut diagonal rectangular patch and pinwheel loop shape ground contributes to bandwidth expansion. Numerical results indicate that the FSS structure is capable of converting x or y polarised incident wave to the relevant cross-polarised wave in a wide frequency range from 7.5 to 24.5 GHz with a fractional bandwidth of 106% for -10 dB r xy reflection amplitude. In addition, the r yy and r xy reflection coefficients of the proposed unit-cell present slight variation for different incident angles up to 40°, which verifies the applicability of the proposed FSS structure in a practical environment. For experimental validation, a prototype of the FSS structure is fabricated and reflection parameters of the proposed structure are measured which agree well with corresponding simulations. Due to the minimal dependency on the angle of incidence and non-uniform ground plane the proposed polarisation converter unit-cell can be a possible choice for secure building applications.

Frequency-Selective Surface to Determine Permittivity of Industrial Oil and Effect of Nanoparticle Addition in X-Band

A frequency-selective surface (FSS) structure is proposed for characterization of the permittivity of industrial oil using a transmission/reflection (TR) measurement scheme␣in the X-band. Moreover, a parameter study is presented to distinguish the dielectric constant and loss characteristics of test materials. To model the loss empirically, we used CuO nanoparticles artificially mixed with an industrial oil. In this study, the resonant frequency of the FSS is the basic parameter used to determine the material characteristics, including resonance properties such as the magnitude of transmission (S 21), bandwidth, and frequency shift. The results reveal that the proposed FSS structure and setup can act well as a sensor for characterization of the dielectric properties of industrial oil.