Design Of Frequency Selective Surface Research Articles

Second Order Frequency Selective Surface Design Multi-functional at Two Bands

Abstract 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.

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<i>λ</i><sub>L</sub> 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.

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.

Dual‐band sub‐6‐GHz frequency filtering with optically transparent single‐layer dual‐polarized smart surface

AbstractOptically transparent dual‐band frequency‐selective surfaces (FSSs) are promising candidates to address the specific design challenges of the Internet of Things. This paper demonstrates their potential by discussing different configurations of the two single‐layer FSS designs on an innovative optically transparent polyvinyl chloride surface material. First, FSS cells consist of two cross dipoles placed forming angles of , where each rotated dipole structure parallel to the other. Then, in the second design, each one of the two cells is mirrored to enable polarization control for each band. As a proof‐of‐concept, five prototypes of each design having a unit cell size of are fabricated through a combination of cost‐effective printing and shearing. The manufactured prototypes yield more than 93% transparency and robust dual‐band performance. Moreover, more than 20 and 40 dB isolation for lower‐ and upper‐frequency bands are achieved from the fabricated prototypes. High‐transparency, cost‐effectiveness, and robust high performance in terms of suppression make both structures suitable for sub‐6‐GHz fifth generation applications.

Angular Stability Enhancement Using Phase Compensation Method for Frequency Selective Surface Design

This study introduces a novel phase compensation-based, asymmetric frequency selective surface (FSS). Aimed at enhancing angular stability, the phase compensation method utilizes the reflected phase gradient changes generated by two FSSs at large grazing angles. The ultimate improvement in angular stability comes from unit amalgamation to achieve phase complementarity, effectively dealing with the phase shift of incident waves caused by large grazing angles. Based on this principle, the asymmetric FSS structure is built with 3 components: a Minkowski fractal cell, a bent-line square-loop cell, and a thin square-loop parasitic cell. Simulation results show the structure demonstrates a 0 relative shift of resonant frequency within an incidence range of 0-80° under transverse electric (TE) polarization. However, it exhibits a maximum relative shift of 5.12% in resonant frequency at an 80° incidence under transverse magnetic (TM) polarization. Compared with E 1 and E 2 units, this structure significantly reduces frequency deviation—by 100% at 80° incidence under TE polarization and by 80.12% and 83.26% compared with E 1 and E 2 units under TM polarization. Finally, the proposed FSS model was fabricated and processed, with measured data basically aligning with the simulated results.

COMPARATIVE ANALYSIS OF EMBROIDERY AND SCREEN-PRINTING TECHNIQUES FOR TEXTILE-BASED FREQUENCY SELECTIVE SURFACES

Frequency Selective Surface (FSS) is a specialized structure used in the field of electromagnetic waves and radio frequency (RF) engineering. It is designed to exhibit selective transmission or reflection properties based on the frequency of the incident electromagnetic waves. This article describes the design, construction, and analysis of a textile-based band-stop frequency selective surface for use in the highly EM-polluted GSM, Wi-Fi, LTE, and WiMAX bands. A full-wave EM solver called CST Microwave Studio was used to develop and simulate the unit cell of the proposed FSS at the relevant frequency. In this study, embroidered and screen-printed textile based FSSs were designed. According to the results of this study, it was demonstrated that both embroidery and screen printing FSSs exhibit resonance at a frequency of 3.5 GHz. The screen printing method yielded the best results in terms of resonance frequency sensitivity, while the embroidery method showed a resonance frequency shift. It was observed that the stitch directions and density are important parameters in the embroidery method. Gaps between the embroidery paths in the production of embroidered FSSs resulted in differences from simulations due to the disruption of the structural integrity of the unit cell. Consequently, textile-based FSSs offer advantages over traditional FSSs. This study highlights the potential of textile FSSs as an effective means of reducing electromagnetic pollution, and suggests that further improvements in the design and production processes of textile FSSs can be made.

Design of a single layer single band 5G FSS as shielding materials

This paper deals with a novel Frequency Selective Surface (FSS) Electromagnetic shield that operates in the low 5G vertical applications. This FSS is designed for the purpose of serving as an electromagnetic shield to eliminate EMI. The FSS designed operates at a frequency of 5GHz with a bandwidth of 1.45GHz providing a shielding of more than 40dB. The proposed FSS uses a polyester sheet as substrate and uses silver for the metallization of the FSS. Since the proposed FSS is symmetric, it behaves similarly when a Transverse Electric (TE) or a Transverse Magnetic (TM) wave is incident. The structure was designed and simulated using CST software. The results show that this FSS blocks electromagnetic radiation at lower frequencies as intended.

Design of Wideband Frequency Selective Surface Based on the Combination of the Equivalent Circuit Model and Deep Learning

In this letter, a design method for frequency selective surface (FSS) based on the equivalent circuit model (ECM) and deep learning is proposed. In the proposed method, the ECM depicting the target transmission characteristic is first established. Then, with the aid of the established ECM, the target transmission characteristic is converted into the desired transmission curve and the initial topology of the FSS structure is determined. The cascade network is adopted to realize the rapid inverse design of the FSS structure. Benefiting from the established ECM, the high quality of the training data and proper description of the design target can be ensured in deep learning. For verification, an ultra-wideband FSS structure with a passband ranging from 3.1 to 12.05GHz and a stopband ranging from 12.85 to 20GHz is designed. Both simulated and experimental results show that the designed FSS provides an ultra-wide passband with flat-top and fast roll-off characteristics, covering 98.9% target passband and 95.3% target stopband.

A Switchable A-T-A Rasorber With Polarization Selectivity and High Roll-Off Characteristics

Switchable rasorber has attracted a great deal of interest in recent years due to its in-band shielding ability. In this work, a methodology for designing a switchable rasorber with high roll-off and polarization selection characteristics is proposed. The device can be switched between rasorber, polarization selection and absorber modes, and composes of two resistive layers (a passive and an active resistive layer) and a frequency selective surface (FSS). Transmission zeros (TZs) are introduced in the FSS design to improve the roll-off characteristic of its transmission band. The PIN diodes on the active resistive layer and FSS can be independently controlled in the orthogonal polarizations to realize the polarization selectivity. The simulation results indicate that the device exhibits a 27.5% fractional transmission bandwidth (3.42 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\sim$</tex-math></inline-formula> 4.51 GHz) under rasorber mode. In addition, the fractional absorption bandwidth is as large as 142.9% (1 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\sim$</tex-math></inline-formula> 6 GHz) under absorber mode. A prototype is fabricated and measured to validate the proposed design methodology. This work is promising for designing metamaterials (MMs) with excellent flexibility and high performance.

Novel Dual Band Frequency Selective Surface and its Applications on the Gain Improvements of Compact UWB Monopole Antenna

In this work, a highly directional ultra-wideband (UWB) microstrip patch antenna as a single-element is suggested. The proposed antenna’s gain is enhanced with a novel dual-band frequency selective surface (FSS) placed beneath it. The FSS design has a hexagonal structure with meander line inductances and a capacitance-like structure connecting all of the corners to the middle. There is no metallic layer on the other side of the substrate, which shows transmission zeros at 4.95 GHz and 12.7 GHz, and a modified U-shaped monopole antenna is developed. First, the performance characteristics of the antenna and FSS are analyzed from the simulation results, and they are validated experimentally after fabrication, followed by measurement. The compact configuration comprises an antenna loaded with the proposed FSS results S11 less than -10 dB from 3.15 GHz to 22.65 GHz, covering the UWB band together with the X, Ku-band with a bandwidth of 19.5 GHz (151.16% FBW). The antenna’s overall physical dimensions would be 38.8 mm×38.8 mm×25.2 mm (0.407λo×0.407λo×0.265λo), with λo denoting the lowest frequency’s free-space wavelength. The FSS loading results in a 9.9 dBi maximum gain at 10 GHz. The antenna’s small size increases bandwidth, and its high peak gain makes it ideal for use in real-time applications.

Miniaturized frequency‐selective surface with reduced number of metallic vias for electromagnetic shielding

SummaryA miniaturized frequency‐selective surface (FSS) for radio frequency (RF) filtering applications is reported in this paper. The proposed FSS is designed to operate with band stop property at 1.57 GHz. The FSS element is developed using highly convoluted lines running on either side of the substrate interconnected using via lines. This specific arrangement increases the electrical length of the resonator without increasing the physical size. Furthermore, the stability towards polarization variation and independence to different angles of incidence are other major concerns in the design of FSS. The FSS unit cell has rotational symmetry thereby providing polarization‐independent operation. The angular independence is tested for various incidence angles, and the results are presented. The performance of the FSS is validated in real time, and the results are presented. The maximum realized transmission loss is 27 dB at 1.57 GHz, and the attenuation bandwidth with reference 10 dB shielding level is estimated to be 400 MHz centered around 1.57 GHz. The convolution technique along with shorting vias has offered this extreme miniaturization ranging from 7% to 95.7% with reference to most of the FSS reported for L‐band services such as radio, telecommunications, military, and aircraft surveillance.