Design Of Frequency Selective Surface Research Articles

Design of wideband bandpass frequency selective surface based on the patch resonators and substrate integrated waveguide cavities

Design of wideband bandpass frequency selective surface based on the patch resonators and <b>substrate integrated waveguide</b> cavities

Design, simulation and manufacture of a flexible frequency selective surface based on aramid/carbon fiber woven fabric

Frequency selective surfaces (FSSs) are significant for the efficient and accurate transmission of microwave signals due to its ability to selectively shield electromagnetic (EM) waves of different frequencies. In some special scenarios, mechanical properties are vitally required. Herein, a flexible frequency selective fabric (FSF) is proposed. Different from traditional FSSs or reported FSFs, aramid/carbon fiber woven fabric serve as the flexible substrate in which carbon fiber provides functionality instead of metallic materials, and patches made of carbon fiber prepreg are periodically applied for property reinforcement. Equivalent circuit model is used to guide the basic determination of patch’s geometry, and it is further optimized via full-wave simulation software HFSS. A simulation model that reasonably reflect the correlation between structure and frequency-selection characteristic is provided, and structural factors affecting the characteristic are analyzed and discussed. Further, an FSF sample is prepared and its frequency response is measured. Measurement revealed the FSF selectively shields EM waves in the frequency range of 8.9 GHz to 11.4 GHz, and is of the bandpass-bandstop-bandpass characteristic. Benefit from EM property and flexibility, the proposed FSF has advantages in applications pursue lightweight, high strength, and require excellent EM functionality, such as aerospace and structure-EM function integrated products.

A novel ultra-miniaturized 2.5-D frequency selective surface temperature sensor with linear frequency–temperature behavior

This paper presents the design and proposal of a new ultra-miniaturized Frequency Selective Surface (FSS) sensor configuration for applications in temperature sensing systems. A 2.5-D (2.5 Dimensions) FSS is proposed with elements inspired by convoluted metal lines with metal vias inserted and printed on an FR4 dielectric substrate. The vias contribute to the capacitive and inductive effects in the structure, providing ultraminiaturization of the unit cell dimensions. The size of the unit cells of the proposed FSS is equal to 4.42 % of the wavelength in free space for the frequency of 2.21 GHz (resonance frequencies). The principle of operation of the FSS is evaluated using the equivalent circuit model proposed in this work. A new application for ultra-miniaturized FSS based on convoluted geometries as non-contact temperature sensors is analyzed in this work. According to the literature, the electrical permittivity of the dielectric material used as the FSS substrate changes as the temperature of the environment in which the circuit is inserted changes, thus altering its frequency response. Numerical analyses were carried out and found that the FSS has an almost linear relationship between the resonance frequency and the electrical permittivity. The numerical results simulated for the prototype were obtained using the ANSYS HFSS software and the equivalent circuit model. The prototype sensor was built and the transmission coefficient and resonance frequency were experimentally characterized. The proposed sensor was experimentally analyzed from a temperature of 20° to 120°C and showed a sensitivity of 0.640 MHz/°C. The values obtained in the experiments were compared and discussed with the results of the simulations, which showed good agreement.

Second order frequency selective surface design multi-functional at two bands

This paper proposes an active frequency selective surface which furnishes three bands of higher order filtering characteristics. It controls multi-functional features, at two bands (centered at 2 GHz and 4 GHz), namely electromagnetic response and polarization of plane wave. Nine discrete filtering outputs are independently controlled through switching in bias supply to four PIN diodes embedded in two layers of AFSS unit cell. Two multifunctional bands hold stability upto 45° angles under all polarizations of wave. Passive band at around 5.9 GHz contributed by all the independent binary combinations exhibits stability upto 45° angles of TE wave only. The equivalent circuit method is used to explain and verify the designed structure. Finally, the AFSS structure is fabricated and reliability of the simulation results is verified through experiments.

Design of single layer bowtie wide band-stop frequency selective surface with angular stability for C-band applications

This paper presents the design and analysis of a single-layer wide band-stop frequency selective surface (FSS) tailored for C-band applications. The proposed FSS design employs a modified bow-tie unit cell structure that enhances band stop characteristics, resulting in improved performance compared to traditional FSS geometry. The design process involves numerical simulations and optimization techniques to achieve the desired frequency response. A modified bowtie element with FR4 substrate comprises the proposed FSS which exhibits a resonant frequency of 6.0 GHz with a wide bandwidth of 4.84–6.96 GHz (35.93 %) and act as a band stop filter. The FSS is analyzed in terms of its transmission coefficients, providing insight into its filtering properties. In addition, parametric studies of the unit cells are done. Furthermore, the angular stability of the proposed FSS is simulated with incident waves at various angles between 0° to 60° for both TE and TM modes. The proposed FSS presents C-band applications of WLAN, ISM/WiMAX, satellite communications, radar systems, shielding and communication devices, also enhancing filtering capabilities and system performance. The simulation results are well correlated with measurement results.

Ultra Miniaturization and Transparency Frequency Selective Surface for Dual Band ISM Shielding

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 Low-profile Dual-band Frequency Selective Surface with High Selectivity at its Higher Passband

In order to meet the requirements for multiband communication, a dual-band passband frequency selective surface (FSS) with low-profile and high selectivity at its higher passband is proposed in this paper. The proposed FSS is a three-layer structure. An arc-cross patch (ACP) and four quarter-circular patches (QCP) are introduced on the outer layers to produce two transmission nulls of the higher passband, which result in high selectivity of higher passband. The inductively complementary structure on the middle layer is introduced to manipulate the coupling between layers which contribute to the low-profile and angular stability. The segmental study method is used to establish the equivalent circuit model (ECM) and analyze its mechanism. The proposed dual-band FSS, whose high selectivity was verified by experiment, is low-profile and shows good polarization insensitivity and angular stability. A feasible FSS design solution is provided for dual-band communication.

Dynamic frequency switching of a bandstop reconfigurable frequency selective surface with PIN diodes for C/X and Ku-band shielding applications

This paper presents a reconfigurable bandstop frequency selective surface (R-FSS) design capable of switching across C, X and Ku-bands. The electronic switching mechanism is achieved in real-time through PIN diodes. The combination of rectangular loops is selected as unit-cell and PIN diodes are strategically placed to dynamically adjust the bandstop region. The device operates in three distinct modes corresponding to the activation status of the PIN-diodes. For TE polarization, Mode 1 encompasses the Ku-bandstop (12.64–14.75 GHz), Mode 2 corresponds to the C/X-bandstop (6.62–11.28 GHz), and Mode 3 involves the X-bandstop (9.82–11.63 GHz), whereas X-bandstop characteristic is observed for TM polarization (9.054–––11.29 GHz). In TE polarization, each configuration is defined by specific equivalent circuit models, featuring an inductance in parallel with series L-C resonant circuit, an L-C resonant circuit in parallel with the inductance, and two L-C resonant circuits in parallel, respectively. Additionally, for TM polarization, the configuration incorporates two parallel L-C resonant circuits. A prototype of the proposed R-FSS is fabricated and measured. The results demonstrated effective switching operation across the C, X and Ku-band stopbands, depending on the biasing of the PIN diodes. The experimental outcomes are consistent with the simulation results, affirming the compatibility and functionality of the proposed R-FSS design.

Low‐profile frequency selective surface with quasi‐elliptical bandpass response using antenna‐filter‐antenna approach

AbstractAn antenna‐filter‐antenna (AFA) based frequency selective surface (FSS) with excellent spatial filtering performance is proposed. This FSS design incorporates two back‐to‐back microstrip patch antennas, which not only ensures a high roll‐off rate at the passband edge and excellent flatness within the passband, but also achieves an ultra‐low profile. Significantly, the upper and lower band edges demonstrate a substantial drop from −3 to −10 dB within the 0.006 and 0.02 GHz ranges, respectively, resulting in a sharp roll‐off skirt. Furthermore, the frequency of radiation null can be controlled by manipulating the length of the quarter‐wavelength open‐ended stub, thereby possessing exceptional out‐of‐band suppression. A prototype of the proposed FSS with low profile is fabricated and measured. The simulations and measurements of the AFA‐based FSS show that a quasi‐elliptical bandpass filtering response with superior performance is achieved.

Design and analysis of a complementary structure-based high selectivity tri-band frequency selective surface

This work presents a novel tri-band bandpass frequency selective surface (FSS) that achieves high-order filtering responses in different frequency bands by means of a complementary structure. The proposed FSS is composed of three metal periodic arrays, which are separated by multilayer dielectric substrates. The gridded-double convoluted loop (G-DCL) structure, which is the middle layer structure, is a hybrid resonator that generates different resonant frequencies. The top and bottom layer structures are designed as complementary structures to the middle layer. To accurately describe the frequency responses, an equivalent circuit model (ECM) has been constructed over the entire band from 0 to 16 GHz. The results of the simulation indicate that the developed FSS can generate three pass-bands operating at 3.79 GHz, 8.34 GHz, and 12.52 GHz, respectively, and − 3 dB fractional bandwidths are 52.8%, 13.7%, and 19.7%. The transmission responses at the edges of each passband show a quick roll-off from the passband to the stopband, and there is significant out-of-band suppression between adjacent passbands. Moreover, the FSS maintains excellent angular and polarization stability within a 50° range. For verification, the tri-band FSS has been fabricated and tested. The experimental results match the simulation results, validating the accuracy of the FSS design.

Flexible Polycarbonate and Copoly(Imide-Carbonate)s-Based Frequency Selective Surface for Electromagnetic Shielding Application

Optically transparent polycarbonates (PCs) and Copoly(Imide-Carbonate)s (Co-PICs) were synthesized by the melt polycondenzation method. Rigid (imide) and flexible (-O- and –C(CH3)2−) moieties were incorporated in the structure of bisimide diol comonomer using 4-aminophenol and 4,4′-(4,4′-isopropylidenediphenoxy) bis(phthalic anhydride). The structural properties of synthesized comonomers and polymers were confirmed by 1H, 13C-NMR and FT-IR spectra. Thermal properties of polycarbonates and copolycarbonates were examined using DSC and TG analysis. Thermal properties (glass transition Tg and thermal decomposition (Td) temperature) of copolymers were enhanced without sacrificing properties of BPA-based PC (high transparency, ductility, and processability) by the incorporation of active functional bisimide diol comonomer (5–10 mole %) in the polycarbonate backbone. Different sets of PCs and Co-PICs thin film substrates were prepared by the solvent casting method and used to design frequency selective surface. The proposed flexible FSS offers shielding of 20 dB at 8.8 GHz. In addition, the FSS offers polarization independent operation with its symmetrical unit cell geometry.

Wideband dual‐polarized rasorber design with genetic algorithm synthesis

AbstractIn this letter, an 11 GHz centered wideband absorptive frequency selective surface (FSS) design is presented. The absorptive FSS is dual polarized, and it has wide transmission band and a wide absorption band at the lower frequency side of the transmission band. An octagon shape with parallel microstrips toward center connected with lumped element resistors at the edges is proposed for the resistive layer unit element. Also, a multilayer octagon patch and aperture resonator are proposed for the wideband bandpass layer. As an alternative design method, the unit element of resistive layer of absorptive FSS is synthesized by a genetic algorithm code successfully. Genetic algorithm synthesis provides straightforward synthesis process compared to conventional method. Designed absorptive FSS is manufactured and frequency response is measured with WR‐90 waveguide setup. The measurement result of 1 dB transmission bandwidth is between 9.43 and 12.50 GHz with a minimum insertion loss of 0.65 dB.

Design and analysis of frequency selective surface embedded broadband high gain miniaturized antenna

SummaryIncorporating the better impedance matching capability of planar curved radiating patch, a miniaturized broadband planar antenna has been designed, analyzed, and integrated with frequency selective surface (FSS) to accomplish higher gain for various short‐range and long‐range modern wireless communication applications. Physical and electrical volume of the presented antenna is 25 × 20 × 1.6 and 0.25 × 0.20 × 0.016, respectively. The proposed radiating patch is constructed from a conventional rectangular patch by transforming the upper side of the patch into a semi‐circular shape and the lower side of the patch into a staircase‐like shape. Measured outcomes of the designed antenna show a very large operating bandwidth of 19.8 GHz (3–22.8 GHz) with a fractional bandwidth (FBW) of 153.5% and bandwidth dimension ratio (BDR) of 3070. An equivalent circuit model (ECM) of the proposed antenna is developed using an advanced design system (ADS) circuit simulator. The frequency responses of the ECM are compared with the simulation done by CST Microwave Studio Suite software and measurement results, which show good agreement. An FSS structure with stop band from 2–28 GHz is positioned beneath the proposed antenna at optimal position (27 mm below the antenna) to enhance the gain up to 8.9 dBi. The presented antenna and FSS are fabricated on FR4 substrate and experimentally verified using standard microwave measurement setup.

Triple band frequency selective surface design for 5G mm‐wave communication with artificial neural networks

AbstractHigh‐performance frequency selective surfaces (FSSs) have gained attention for their spatial filtering characteristics in 5G communication systems. In this work, we propose an efficient and accurate design methodology for the FSS. Three different artificial neural network methods (ANN) are employed, and their performances are compared for analysis and synthesis purposes. Results show that GRNN has the highest performance for both training and test phase of ANN based FSS analysis and synthesis. A novel, compact, low‐profile triple band FSS unit cell is introduced, and the working mechanism is described. By applying ANN based design procedure, the unit cell dimensions to resonate at the 5G mm‐wave frequency band is extracted. A unit cell with the extracted physical dimensions is simulated with a full‐wave analysis tool. The simulation results show that the FSS has the filtering feature at the predetermined mm‐wave frequencies of the 5G communication. The prototype of the FSS is fabricated, as well. The simulations are verified experimentally with measurement results. The results show that proposed ANN based analysis and synthesis method can be an effective tool for the design of FSS band‐pass filter for 5G applications.

A Novel Ultra-Miniaturized Angularly Stable Frequency Selective Surface for L-Band Shielding Applications

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.

Comparative analysis of X‐band FSS fabricated by inkjet printing and conventional etching technique

AbstractAn investigation of a single‐layer band‐stop frequency selective surface (FSS) is designed and analyzed for X‐band application. The proposed FSS design primarily involves a cross‐shaped conductive patch with four square slots on each corner, and it is fabricated on the 3D‐printed polylactic acid (PLA) substrate. The design is resonating at 12 GHz with an insertion loss greater than 60 dB. The 10 dB bandwidth of the designed structure is 8.3% with respect to the resonant frequency. The results show that the design has polarization‐independent and angle‐insensitive transmission characteristics for incidence angles up to 60°. The simulation is carried out using CST Microwave Studio Suite, and the results are obtained. The physical mechanism of the designed structure is evaluated using the surface current distribution. The designed FSS is fabricated using two techniques, namely inkjet printing and conventional etching. Finally, the measurements of the fabricated structure are done using a vector network analyzer setup.

Ultra-wideband thin frequency-selective surface absorber against sheet resistance fluctuation

The design of thin frequency selective surface (FSS) absorber based on resistive film that meets the requirements of broadband, polarization independence, incident angle stability, and strong absorption is a challenging task. Fabrication tolerance of resistive film can result in fluctuations in sheet resistance, which negatively affects the absorber performance. To tackle these problems, this work firstly investigates how sheet resistance fluctuations affect the absorbing performance of resistive film FSS absorber. The analysis of simulated surface current density distribution and impedance reveals that the diversity of current paths provides an effective way to mitigate the influence of sheet resistance fluctuation. This is achieved by enabling flexible variation of surface current in response to sheet resistance fluctuations. Consequently, the variation of input impedance of the FSS absorber due to the fluctuation of sheet resistance is suppressed within a small range. Then, a method of extending bandwidth is proposed by employing the complementary variation of FSS impedance with frequency at different layers. By combining this approach with a miniaturization design, a thin and light FSS absorber is developed that exhibits ultra-wide bandwidth, polarization independence and angle stability while mitigating the effects of sheet resistance perturbation. The proposed FSS absorber achieves a 90% absorption bandwidth from 1.50 GHz to 20.50 GHz, covering Ku, X, C, S bands and part of the L and K bands, with a relative bandwidth reaching 173%. The absorber has a thickness of 0.093&lt;i&gt;λ&lt;/i&gt;&lt;sub&gt;L&lt;/sub&gt; for both transverse electric (TE) polarization and transverse magnetic (TM) polarization, yielding a figure of merit (FoM, the ratio of the theoretical minimum thickness to the actual thickness) of 0.95, indicating that the thickness is close to the theoretical limit. The absorber maintains over 90% absorption rate for TM polarization at an incidence angle of up to 70°, and 80% absorption for TE polarization at 45°. Furthermore, the 90% absorbance bandwidth of the absorber remains at 167.0% when the sheet resistance of any FSS layer fluctuates within a range from 12 to 30 Ω/sq. A prototype of the proposed FSS absorber is fabricated and measured, and the experimental results are in good agreement with the simulation results, thus validating the effectiveness of the proposed method.

Wideband and wide-angle microwave absorber via an integrated frequency selective surface and lattice structure design

Wideband and wide-angle microwave absorber via an integrated frequency selective surface and lattice structure design

Notice of Retraction: Carbon-Reinforced Flexible Band-Stop Frequency Selective Surface Design

Notice of Retraction: Carbon-Reinforced Flexible Band-Stop Frequency Selective Surface Design

Design of Wideband Two-Sided Bandpass Frequency Selective Surface for X, Ka, and Ku Band Application

A novel wideband bandpass frequency-selective surface functioning at X, Ku, and Ka bands is proposed in this article. The designed FSS has a metallic square loop and a circular ring, and they are printed on both sides of the FR4 substrate. The proposed design FR4-based single-layer FSS is operating from 11.075 GHz to 22.075 GHz with a fractional bandwidth of 66.36%. The parameters of the square loop and circular ring regulate the characteristics of the passband. The optimum dimension of these parameters is obtained with parametric analysis. The proposed structure is measured and fabricated. However, the measured results strongly agree with the simulated results, which authenticate the proposed design performance.