Ultra-wideband Frequency Selective Surface Research Articles

Design of highly selective ultrawideband FSS based on deep learning for EMI shielding in 5G bands

Abstract In this paper, a frequency selective surface (FSS) for n41, n78, n257, n258, n260, and n261 bands electromagnetic interference (EMI) shielding is proposed using a deep learning method. The size of the FSS unit cell is 4.8 mm (0.071 λ 0 ), where λ 0 is the wavelength corresponding to the cutoff frequency of the −10 dB stopband where the n41 and n78 bands are located. This FSS exhibits three key characteristics. Firstly, it possesses ultrawideband capability, with a stopband frequency range of 23.922–40.023 GHz and a relative bandwidth reaching 50.4%. Secondly, it effectively shields against electromagnetic radiation in multiple 5 G bands, including n41, n78, n257, n258, n260, and n261. Thirdly, it demonstrates high selectivity, with a very narrow transition band of only 0.405 GHz between the passband and the stopband. To validate the designed FSS, a prototype of this structure was first fabricated for experimentation. The experimental results show that the measured S21 is highly consistent with the simulated S21. Secondly, the unit cell array of FSS is placed above the monopole antenna for co-simulation. It can be observed that after placing the FSS, the intensity of electromagnetic radiation propagating in space is significantly reduced by up to more than 90%. Therefore, the proposed FSS can be effectively applied for EMI shielding in 5 G bands.

Performance enhancement of Vivaldi-shaped planar UWB antenna using a single-layer FSS reflector

This work proposes the design of a frequency-selective surface (FSS)-based planar monopole antenna for ultra-wideband (UWB) communication applications. The UWB response is observed by integrating a Vivaldi-shaped slot and by introducing a stepped-like pattern on the bottom edges of the radiating patch, while the back side is composed of a partial ground plane. This configuration results in a broad impedance bandwidth spanning from 3.11 to 20 GHz. For radiation performance enhancement of the proposed antenna, a single-layer UWB FSS reflector is placed beneath the antenna element at an optimized distance. The proposed FSS reflector employs a 3 × 3 array of fractal structure with a unit cell size of 12.25 × 12.25 mm2. The designed FSS reflector exhibits a linear phase response over a frequency range of 3.28 to 14 GHz, with a stop-band transmission coefficient less than -10 dB. The incorporation of the FSS reflector results in an increased gain, elevating it from 1 to 4 dBi at low-band frequencies, while at mid-band frequencies, the gain is increased from 1 to 6 dBi. The structural configuration of the proposed antenna yields directional far-field patterns, making it well-suited for UWB radar applications.

An Ultrawideband Frequency Selective Surface Absorber With High Polarization-Independent Angular Stability

An ultrawideband frequency selective surface (FSS) absorber with high angular stability and polarization independency applied in a microwave band is proposed. The absorber is composed of three identical Teflon layers and dual FSS layers with distinct patterns. The miniaturized FSSs with unique patterns demonstrate advantages of facile manipulation of the impedance and multiple resonances in an ultrawide frequency range. The use of identical dielectric substrate greatly reduces the complexity in the absorber design, compared with the conventional way that requires variable dielectric constants for a multilayer structure. Experimental results reveal that more than 90% absorption rate in the frequency range of 2.79–20.62 GHz for normal incidence is achieved. The absorption rate can still retain more than 80% in the range of 4.41–20.93 GHz for both TE and TM polarizations with an incidence of 60°.

Norman window slot antenna with sectoral feed backed by linear phase reflector for ultra wideband applications

An ultra wideband (UWB) slot antenna is proposed, developed, and experimentally validated in this article. The Norman window-shaped UWB slot antenna demonstrates stable radiation characteristics in both directions—zenith (θ = 0°) and nadir (θ = 180°) over the entire UWB frequency range (3.1–10.6 GHz) as observed in both simulations and experiments. A linear phase reflecting UWB frequency selective surface (FSS) is proposed by printing two orthogonal layers of pair of double rectangular loops on the same side of dielectric substrate as a merged frequency selective surface (MFSS). The UWB MFSS is then loaded with the slot antenna and the impact of MFSS on the impedance and radiation characteristics in different configurations of antenna and MFSS together is studied. One configuration with optimum solution is developed for experimental validations followed by the analysis of its radiation characteristics. The proposed antenna demonstrates a directional radiation pattern due to suppression of back lobe radiation when integrated with the UWB MFSS. The proposed antenna demonstrates maximum gain of 7.86 dB with a gain enhancement of 3.6 dB in boresight (θ = 0°) direction when MFSS is applied as a reflector to opposite side of the antenna slot.

A new compact ultra-wideband frequency selective surface with angular stability and polarization independence for antenna radiation enhancement in microwave imaging application

A new compact, rudimental, uni layered frequency selective surface (FSS) is proposed to work in the commercial ultra-wideband (UWB) spectrum with its application in enhancing broadside radiation of an UWB antenna. The overall unit cell dimension (length × width × thickness) of the proposed UWB FSS is 0.15λL × 0.15λL × 0.016λL only where λL represents the wavelength corresponding to lowest band edge in the 3.04 to 10.88 GHz (∼112.6 %) spectrum with transmission coefficient less than −10 dB. Moreover, the proposed FSS provides certain degree of angular stability of 45° in both TE and TM planes of polarization. The proposed FSS is well suited for antenna gain augmentation as it offers linearly decreasing reflection phase profile. A compact ultra-wideband U-shaped CPW fed antenna with the dimension of 32 × 26 × 0.8 mm3 is designed that covers a bandwidth from 2.7 to 12.76 GHz (130 %). The proposed FSS is integrated with the U-shaped antenna to exhibit an improved and steady gain profile of 5.1–6.8dBi in the 2.82–12.92 GHz (128.34 %) impedance band. Maximum gain augmentation of 3.62 dBi is achieved at 9.5 GHz along with steady gain profile in the entire operating band of “antenna-FSS”, linear S21 response and flat group delay variations which implies the applicability of proposed antenna-FSS in various UWB communication purposes that comprise impulse radar, through wall imaging, microwave imaging, short range indoor communication etc. The applicability of UWB ‘antenna-FSS’ is established by ground coupling microwave imaging test in proximity of soil test bed where the fundamental characteristics of ‘antenna-FSS’ is found to be unaltered.

An Ultrawideband Three-Dimensional Bandpass Frequency Selective Surface

A new ultrawideband frequency selective surface(FSS) is proposed, which exhibits six resonances to achieve a flat passband. It consists of a three-dimensional (3-D) configuration. However, unlike many other 3-D FSSs, the proposed structure can be assembled through simple steps involving single-layer printed circuit board (PCB) fabrication only. Its unit-cell consists of a wire-loop conducting pattern, printed on a dielectric substrate. The pattern excites four resonances while two resonances are contributed by the dielectric. These six resonances are properly tuned and coupled to form an ultrawide frequency band from 7.53 to 29.45 GHz. It translates to a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$-$</tex-math></inline-formula> 3 dB bandwidth of 119 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\%$</tex-math></inline-formula> . Our design guidelines and discussions are validated through both simulation and measurement results.

Ultra-wideband Frequency Selective Surface for Communication Applications

A low-profile ultra-wideband (UWB) band-stop frequency selective surface (FSS) is designed for S-, C-, X- and Ku-bands communication applications. The FSS is constructed by using square and circular loop elements printed on the top and bottom sides of the RO3210 substrate. The FSS has been designed to reduce the electromagnetic interference (EMI) as well as to mitigate the harmful effects of electromagnetic radiation on the human body caused by different radio devices. The dimension and size of the UWB FSS have been reduced to 0.12 λ × 0.12 λ and 90%, respectively, as compared to the reported literature. The other advantages of the proposed FSS are that it is low profile, it has a simplified geometry and it ensures better angular and polarization stability of up to 85°. The –10 and –20 dB bandwidths of the proposed FSS are 146% (2.0–13.0 GHz) and 80% (4.87–11.42 GHz), respectively. Theoretical results have been obtained using ANSYS HFSS and verified through measured results.

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.

An ultra-wideband frequency selective surface with high stability for electromagnetic stealth

Aiming at the problems of low-frequency coverage, angle and polarization instability of ultra-wideband (UWB) frequency selective surface (FSS) in practical application, this paper introduces the additional circular parasitic patches and two-stage rectangular bent grids to enhance coupling, miniaturize geometry size, broaden bandwidth and suppress the drift of resonance frequencies based on the construction of a FSS unit cell by using a basic circular patch and a Jerusalem cross grid. The simulated and measured results show that the bandwidth of the FSS is 13.47 GHz, and its fractional bandwidth is 140.53%, which fully covers the UWB band (3.1–10.6 GHz). The UWB FSS has the flat transmission passband, and high transmission characteristics, and maintains stable performance at large incident angles and different polarization modes. The size of the UWB FSS unit cell is 0.25 λc × 0.25 λc × 0.12 λc. Therefore, the UWB FSS can be applied to electromagnetic stealth and the related fields of UWB communications.

Design and Analysis of Single Sided Modified Square Loop UWB Frequency Selective Surface

In this article, a compact frequency selective surface (FSS) is implemented using a modified metallic square loop structure for ultrawide band (UWB) stop behavior. The proposed structure exhibits wideband rejection over the entire UWB, ranging from 3.1 to 10.8 GHz. The proposed structure manifests polarization independent characteristics and provides a stable frequency response for normal and oblique angles under both transverse electric (TE) and transverse magnetic (TM) incident polarization. The angular stability for various polarization angles is also obtained. This structure provides a −10dB wide impedance bandwidth of 110.79%. The maximum relative deviation in between transmission zero frequency and angularly incident frequency is 5.9% and 6.2% at 80˚ TE and TM polarized wave, respectively, with attenuation more than 45 dB. The unit cell of the proposed FSS is imprinted on single-layer FR4 substrate of the dimensions 6 × 6 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , which is 0.062× 0.062 λ, where <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">λ</i> is the wavelength of lower cut-off frequency and is by far the smallest design for the desired UWB rejection FSS.

Gain Augmentation of a Triple Notched Ultra-wideband Antenna using Compact Uniplanar Frequency Selective Surface for Ground Penetrating Radar

A simple structured, compact ultra-wideband (UWB) circular disk monopole antenna of dimension 35 × 30 × 0.8 mm3 that offers wide bandwidth from 2.64 to 9.36 GHz with sharp triple notch bands at 3.28–3.84, 5.08–5.44, and 5.62–6.06 GHz is integrated to the single-layer UWB frequency selective surface (FSS) that has unit cell dimension of 0.1136λL × 0.1136λL only where λL signifies the lower band-edge of UWB. Sharp triple notches are employed by embedding split-ring slot on circular patch and implanting dual circular split-ring resonator pairs at the backside of feed. Addition of FSS layer does not affect the antenna impedance band and offers significant antenna gain improvement by 2–4 dBi in the pass bandwidth with maximum gain of 8 dBi at 8.5 GHz. The antenna also provides high average radiation efficiency of 80%, improved radiation in the broadside direction and consistent group delay response in its pass band when integrated to the FSS layer. Working capability of proposed antenna-FSS structure is evaluated in proximity of soil test bed by keeping thin aluminum sheet at different buried levels. Adequate VSWR profile, linear transfer function response, and consistent group delay response in pass band ensure the eligibility of proposed antenna to work for ground penetrating radar.

Evolution of Low-Profile Ultra-Wideband Frequency Selective Surface with a Stable Response and Sharp Roll-Off at Lower Band for C, X and Ku Band Applications

Evolution of Low-Profile Ultra-Wideband Frequency Selective Surface with a Stable Response and Sharp Roll-Off at Lower Band for C, X and Ku Band Applications

Compact Ultra-Wide Band Frequency Selective Surface With High Selectivity

In this communication, an ultra-wide band frequency selective surface (FSS) with excellent transmission performance in the desired passband and reflection performance in the out-of-band is proposed. In order to simultaneously achieve a wide bandwidth, as well as the better band-stop characteristic, a cascaded hybrid resonant element is employed to construct the FSS, which is composed of resonant circular rings and inductive meandering grid arranged on different layers. In addition, a fifth-order equivalent circuit model (ECM) is established over the entire band from 0.1 to 8 GHz, which can accurately describe the frequency responses. Finally, a prototype of the proposed design is fabricated and measured. The results show that a wide −3 dB bandwidth of 154.4% from 0.5 to 3.88 GHz is achieved. The −10 dB stopband is from 4.04 to 7.68 GHz and a sharp transition within 160 MHz from passband to stopband is obtained. The dimensions of the element are as compact as $0.0263\lambda \times 0.0263\lambda $ at the starting frequency of the passband. All the results demonstrate the ultra-wide bandwidth advantage and excellent out-of-band reflection, steep roll-off, and miniaturization performances.

A Single Layer UWB Frequency Selective Surface for Shielding Application

This article proposes a low profile and miniaturized ultra-wideband frequency selective surface (UWB FSS) structure which provides wide bandwidth for shielding applications. A single layer FSS constructed with a simple square loop and cross dipole structure provides bandstop filter response covering high frequencies from 4.85 GHz to 17.23 GHz at 10 dB insertion loss, with a bandwidth of 12.38 GHz and a fractional bandwidth exceeding 112%. The proposed FSS structure also provides excellent polarization independent behavior for angles of incidence up to 30°. A prototype of the proposed FSS is fabricated and the measurement result is compared with the simulation results, and both are in good agreement.

Design and Synthesis of an Ultra Wide Band FSS for mm-Wave Application via General Regression Neural Network and Multiobjective Bat Algorithm

In this work is presented a hybrid bioinspired optimization technique that associates a General Regression Neural Network (GRNN) with the Multiobjective Bat Algorithm (MOBA), for the design and synthesis of the Frequency Selective Surfaces (FSS), aiming its application in data communication systems by diffusion of millimeter waves, specifically, in the IEEE 802.15.3c standard. The designed device consists of planar arrangements of metallizations (patches), diamond-shaped, arranged over a RO4003 substrate. The FSS proposed in this study presents an operation with ultra-wide band characteristics, its patch designed to cover the range of 40.0 GHz at 70.0 GHz, i.e., 30.0 GHz bandwidth and 60.0 GHz resonance. The upper and lower cutoff frequencies, referring to the transmission coefficient’s scattering matrix (dB), were obtained at the cutoff threshold at -10dB, to control the bandwidth of the device.

Ultra Wideband Coplanar Waveguide Antenna with an Improved Gain using a Frequency Selective Surfaces (FSS)

In this article, an ultra-wideband FSS reflector has been proposed to enhance the gain of a CPW antenna for UWB applications. A CPW fed antenna having dimensions of 38mm×38mm×1.605mm and FSS unit cell having dimensions 14mm × 14mm × 1.605 mm are presented in the paper. A rectangular slot and stubs are interleaved at the outer edges of the patch for achieving desired characteristics of an ultra-wideband for the frequency range of 3.39 GHz to 12.9 GHz. Simulation results carried out using the CST microwave 2016 version in the time domain are presented for the proposed antenna. An FSS unit cell designed and simulated using periodic boundary conditions and floquet ports is presented. The combined setup of an array of FSS reflector behind the antenna has been simulated in the time domain. This set up shows an improved performance in terms of antenna’s gain. A maximum and minimum gain of 8.14 dB and 4.98 dB has been observed with the presence of FSS reflector behind the coplanar waveguide antenna. A significant improvement of 2.9 dB has been observed over the entire band of antenna’s operation

Perforated Medium Applied in Frequency Selective Surfaces and Curved Antenna Radome

A perforated medium (PM) combined with an ultra-wideband frequency selective surface (FSS) is proposed for the antenna radome design, which provides more flexibility in the radome materials selection and processing. The dielectric constant performance of the PM can be improved by perforating air holes through the medium, thus the restrictions of the FSS medium material parameters can be released. A multiscale homogenization method is utilized to calculate the dielectric constant of this PM, and the transmission coefficients of the planar FSS structure at different incidence angles are computed. The PM FSS is then applied in the curved antenna radome. The physical optic method serves to analyze the transmission performance of the curved antenna radome. In order to reduce the computational difficulties and meet the requirements of physical optic computing, the transmission coefficients are obtained as a function of the frequency by the vector fitting method, and the incidence angle dependence is deduced by B spline interpolation. The simulated and experimental radiation patterns with and without the radome are compared and the results show good agreement.

Low-Pass FSS for 50–230 GHz Quasi-Optical Demultiplexing for the MetOp Second-Generation Microwave Sounder Instrument

This paper reports the design, manufacture, and characterization of a new frequency selective surface (FSS) structure which meets the demanding requirements for transmission of 50.2–57.7 GHz radiation simultaneously for TE and TM polarizations at 45° incidence, and reflection of signals in four discrete higher frequency bands centered at 89, 165.5, 183.3, and 229 GHz. The FSS is required for a quasi-optical network, which was developed during the preparatory breadboarding of the microwave sounder instrument. The 100 mm diameter ultrawideband FSS must exhibit ≤0.25 dB loss for all signals in the above bands, and has to satisfy the requirements of the space environment. The FSS is formed by a periodic metal film array sandwiched between two 0.83 mm thick, optically flat, fused quartz substrates. It has 19 000 unit cells composed of two compact resonant slot elements, a meandering elliptical annulus and a folded dipole. Spectral transmission and reflection measurements in the 50–230 GHz frequency range yielded results that are in excellent agreement with numerical predictions.

Paper] Low Profile UWB Frequency Selective Surface based Antenna

In this paper, we present the design of a new ultra-wideband (UWB) frequency selective surface (FSS) based antenna, by using a wide stop-band FSS as a backing reflector for an UWB monopole antenna. A new single layer FSS, with UWB stop-band response and a reflection phase varies linearly with frequency, is firstly designed and thereafter, it is integrated with an UWB electric monopole. The studies of the behavior of the proposed antenna reveal that a unidirectional radiation with a quasi-constant gain of an average of 9dBi and a compact profile of λ/10 are achieved. The features of the proposed UWB FSS and its based antenna make them good candidates for integration with low profile broadband printed circuits and UWB applications.

Polarization-independent single-layer ultra-wideband frequency-selective surface

An ultra-wideband (UWB) frequency-selective surface (FSS) exhibiting band rejection characteristic is presented in this paper. The proposed unit cell has the size of 14 × 14 mm2 which is approximately 0.18 × 0.18 λo, where λo corresponds to free space wavelength at the lower cut-off frequency. The proposed UWB FSS consists of a single-layer substrate and provides 20 dB attenuation level for a wide bandwidth of 7.53 GHz at the normal incidence. The proposed FSS is polarization independent and also provides angular-independent operation for the EM wave incidences of 15°, 30° and 45° with 11.5 dB attenuation over a wide range from 4 to 14 GHz.