Design Of Frequency Selective Surface Research Articles

Double-layer structure combined with FSS design for the improvement of microwave absorption of BaTiO3 particles and graphene nanoplatelets filled epoxy coating

Graphene nanoplatelets (GNPs) and BaTiO3 particles filled epoxy coating with wide microwave absorption bandwidth were designed and investigated in the frequency range of 2–18 GHz. The microstructures of these coatings exhibit a uniform dispersion of GNs and BaTiO3 particles in the matrix. The double-layer structure and frequency selective surfaces (FSS) design were used to improve their microwave absorption of such coatings. A bandwidth of reflection loss (RL) ≤ −8 dB with 13.9 GHz (from 4.1 to 18 GHz) can be obtained for the double-layer coating combination of FSS structure. The microwave absorption of such double-layer absorber with FSS structure also depended on the incidence angles and polarization model, and higher RL performance is maintained under wide oblique incidence for both TE and TM polarization.

Design and Optimization of 3-D Frequency-Selective Surfaces Based on a Multiobjective Lazy Ant Colony Optimization Algorithm

Frequency-selective surfaces (FSSs) have many applications in spatial filtering of electromagnetic waves and are commonly used in antennas, polarizers, radomes, and intelligent architecture. Conventional FSS designs have ranged from canonical shapes and fractal patterns on planar surfaces to miniaturized and multilayer designs, with stable filtering responses up to 50°. Much less work has been done on 3-D FSS designs, which include multiresonant structures or cavities that offer improved angular stability, with fields of view up to 60°. Recent advances in additive manufacturing techniques have made fully 3-D FSS designs increasingly popular; however, powerful design tools to exploit such fabrication methods are currently unavailable. In this paper, multiobjective lazy ant colony optimization (MOLACO), an adaptive combinatorial optimization algorithm based on ant colony optimization, is introduced and applied to the problem of polarization and angle independent 3-D FSS design. It will be shown that the MOLACO algorithm generates several innovative and unintuitive unit cell geometries with a single-zero, single-pole response, less than 1% shift from center frequencies and −10 dB rejection and 3 dB transmission bandwidths between 6%–12% for angles of incidence up to 80° in TE and TM polarizations. Comparisons are made between designs generated by MOLACO and existing FSS designs.

Design and fabrication of a reconfigurable frequency selective surface using fluidic channels

Design and fabrication of a reconfigurable frequency selective surface using fluidic channels

Design and Analysis of Frequency Selective Surface at Ka/K/Ku Band

Design and Analysis of Frequency Selective Surface at Ka/K/Ku Band

All-dielectric metamaterial frequency selective surface

Frequency selective surface (FSS) has been extensively studied due to its potential applications in radomes, antenna reflectors, high-impedance surfaces and absorbers. Recently, a new principle of designing FSS has been proposed and mainly studied in two levels. In the level of materials, dielectric materials instead of metallic patterns are capable of achieving more functional performance in FSS design. Moreover, FSSs made of dielectric materials can be used in different extreme environments, depending on their electrical, thermal or mechanical properties. In the level of design principle, the theory of metamaterial can be used to design FSS in a convenient and concise way. In this review paper, we provide a brief summary about the recent progress in all-dielectric metamaterial frequency selective surface (ADM-FSS). The basic principle of designing ADM-FSS is summarized. As significant tools, Mie theory and dielectric resonator (DR) theory are given which illustrate clearly how they are used in the FSS design. Then, several design cases including dielectric particle-based ADM-FSS and dielectric network-based ADM-FSS are introduced and reviewed. After a discussion of these two types of ADM-FSSs, we reviewed the existing fabrication techniques that are used in building the experiment samples. Finally, issues and challenges regarding the rapid fabrication techniques and further development aspects are discussed.

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.

Active absorptive frequency selective surface

A novel design of absorptive frequency selective surface (AFSS) with tunable absorptive/switchable transmissive property is presented. The AFSS is comprised of a resistive surface and a metallic bandpass FSS on which PIN diodes are mounted. By changing the working state of the PIN diode, a tunable absorption performance at 3.5–11.2 GHz is achieved with a switchable transmission at the frequency of 0.83 GHz. A prototype of the proposed structure is fabricated and measured under the normal incidence.

Transmission performance analysis of circular polarisation frequency selective surface and fast accurate optimisation based on equivalent circuit

In this study, a promising application of frequency selective surface (FSS) operating in circular polarisation is analysed and designed. Both magnitude and phase consistencies between transverse electric (TE) and transverse magnetic (TM) waves are emphasised, especially transmission phase agreement. Equivalent circuit model (ECM) provides a deep physical insight into phase discrepancy between TE and TM waves. The effects of geometrical parameters of FSS on magnitude and phase consistencies are also investigated by ECM. Additionally, an optimisation process is utilised to obtain desired frequency responses for multi-layer FSS design. This process involves iterative correction and update of coarse circuit model on the basis of a few accurate full wave simulations. Moreover, a dual-layer square slot FSS is efficiently designed using this optimisation method. Finally, a prototype of the optimised dual-layer square slot FSS is fabricated and tested to validate the simulated results.

A compact band‐stop frequency selective surface for dual band Wi‐Fi applications

AbstractThis article presents a compact frequency selective surface (FSS) design which is capable of rejecting both bands of Wi‐Fi. The proposed design is evolved from a patch‐slot topology and it is investigated that the patch‐slot architecture is unstable for oblique incident waves, therefore, a number of geometrical modifications have been proposed to ensure the band stability at different incident angles. The slot geometry is modified by inductive loading and extending the slot length. The modified unit element of FSS is 0.38 λ0 at higher frequency band. Fabricated prototypes have been measured for their transmission response at incident angles upto 30° and good agreement has been observed between simulated and measured results. The proposed FSS is suitable for shielding applications and for limiting the coverage area of wireless access‐point.

A Triple Band Frequency Selective Surface Design for GSM Systems by Utilizing a Novel Synthetic Resonator

In this communication, a novel triple band frequency selective surface (FSS) designed for Global System for Mobile Communications (GSMs) frequency bands is presented. Unit cell of the proposed FSS consists of one rectangular-shaped resonator designed for 942 MHz and one synthetic resonator designed for both of 1842 and 2142 MHz frequencies. A novel technique is introduced to design a synthetic resonator in which two loop-shaped resonators intersect to each other resulting a unique resonator operating at two frequencies. The proposed design has the advantages of separating two very closely spaced frequency bands as in GSM systems with a narrow notch between the two frequencies of 1842 and 2142 MHz. Furthermore, a very low-frequency response sensitivity to the oblique incidence angles is achieved by using a miniaturized single synthetic resonator for the two frequencies in a single layer. Good agreement is observed between the measured and simulated results. A minimum of 20-dB attenuation for the transmission coefficient is achieved in all downlink frequency ranges of GSM system with a good stability against the oblique angle of incidence for both transverse-electric and transverse-magnetic polarizations.

A Novel Simple Convoluted Geometry to Design Frequency Selective Surfaces for Applications at ISM and UNII Bands

In this paper, we use a novel convoluted geometry to design a dual-band Frequency Selective Surface (FSS) with angular stability and independent polarization operation. The geometry allows the design of a dual-band FSS to block ISM and UNII radio bands. We performed a parametric study with the commercial software ANSYS HFSS. A prototype of the designed FSS was built and its transmission characteristics were measured and compared with simulated results. We observed good agreement between numerical and experimental results. The FSS realized a dual-band response at the required bands and it had angular stability and polarization independence.

Design of FSS radome using binary particle swarm algorithm combined with pixel-overlap technique

An optimization method for designing frequency selective surface (FSS) radome using binary particle swarm optimization (BPSO) algorithm combined with pixel-overlap technique is proposed, in this paper. The proposed method takes the connectivity condition of adjacent conductors within FSS element into consideration. With the help of pixel-overlap technique, lattice points in FSS element are avoided by overlapping adjacent conductors, which improves the manufacturability of the FSS layers. Also, structure parameters of the FSS radome can be obtained according to the desired frequency selective property using the BPSO algorithm. To verify the validity of the proposed method, a sandwich-structured FSS radome is designed, fabricated, and measured. Good agreements between the simulation and measurement results can be observed, which demonstrate that the proposed method can be applied to design FSS radome.

Comparative Study of Sub-THz FSS Filters Fabricated by Inkjet Printing, Microprecision Material Printing, and Photolithography

This paper reports a comparative study of sub-THz frequency-selective surface (FSS) filter performance in relation to its method of fabrication. Three techniques are considered: conventional inkjet printing, microprecision inkjet printing, and photolithography. The complete design process is presented highlighting steps from substrate selection through to electromagnetic modeling and finally broadband THz filter characterization. Electromagnetic modeling is performed using the CST full-wave frequency-domain solver. Experimental characterization of substrate material, ink, and final FSS designs is done both by THz time-domain spectrometry and quasi-optically at WR-10 and WR-3 waveguide bands using PNA-X vector network analyzer. The center frequencies for bandpass FSS filters are 100 and 300 GHz, which enables prospective utilization in a quasi-optical multiplier system.

Design and Modelling of the Cylindrical Conformal FSS with Mechanical Bending Cover Method

Traditional Design of frequency selective surfaces (FSSs) often involves the patterning of planar arrays of 2D structures that act as stop or pass band filters for electromagnetic waves. Using the mechanical bending cover method, cylindrical conformal FSS is constructed and then simulated by the discrete FITD model. The results show that the center frequency offsets to the low frequency with the decrease of curvature, but the in-band flatness decreases and the out-band appears severe concussion. The Wood's anomaly exists at high frequency where the transmission will be decreased. Moreover, compared with cylindrical metal plate, the cylindrical conformal FSS behaves good at the RCS reduction performance of single and double stations within the 5 20GHz bands with the incident angles between -150 -50 and 50 150.

3-D Mechanically Tunable Square Slot FSS

We introduce an innovative 3-D mechanically tunable frequency selective surface (FSS), which is inspired by the classical flat square slot FSS. The proposal improves the performance of classical 2-D FSS designs, and it also represents a novel method of achieving mechanical frequency tuning, despite other 3-D designs that consist of a collection of stacked 3-D layers exist. In our proposal, the rotation of an inner element provides tuning capability to the squared cell structure, consisting of metallic grids with a movable inner element. An aluminum prototype was built, which can be tuned from 2.4 to 4 GHz, and also compared its measured performance and numerical simulations. Some characteristics of the proposed structure are the rejection level at main polarization, up to 20 dB, and the maximum frequency sweep of approximately 50% of the fundamental frequency. The prototype showed a stable frequency response for angles of incidence up to 45°. Since results are in good agreement with simulations, we provide parametric equations to design 3-D structures at desired frequencies.

An FSS Structure With Geometrically Separable Meander-Line Inductors and Parallel-Plate Capacitors

A frequency selective surface (FSS) structure with geometrically separable meander-line inductors (MLIs) and parallel-plate capacitors (PPCs) is proposed. For this FSS structure, the filtering responses for different polarizations and resonance frequencies are realized through separate subcells. For example, to achieve a single-band bandpass performance, two subcells, acting as parallel LC resonators for transverse-electric and transverse-magnetic polarizations, respectively, are implemented by MLIs and PPCs. Because the MLIs and PPCs provide increased equivalent inductance and capacitance, respectively, this FSS provides a miniaturized unit cell size of $\lambda _{0}/20 (\lambda _{0}$ refers to the resonance wavelength), and its −3 dB bandwidth can be designed by independently adjusting the equivalent inductance and capacitance. A design example shows the easy control of −3 dB bandwidth ranging from 13.6% to 49% with respect to the center frequency. Furthermore, because of the separable subcells, the FSS performances for different polarizations are independently controllable, and it can be readily extended to achieve dual-band bandpass performance with a band ratio ranging from 1.35 to 3.8. In addition, to model the FSS frequency performance precisely, equivalent circuits and closed forms are developed, which serve as a substitute for commercial software for efficient FSS design. Finally, some prototypes are fabricated and measured. All the measured results show that the proposed FSS designs exhibit stable performance under different polarizations and incidence angles (up to 60°), and they exhibit good consistency with those from the full-wave simulations.

Design of a Compact Passband Frequency Selective Surface with Stable Resonance

We propose a compact planar passband frequency selective surface (FSS) operating at the resonance frequency of 3.81 GHz. The proposed FSS is composed of single layer of the Archimedean spiral type with the interdigital capacitance between the corners of metallic patches printed on one side of the substrate. Compared to the operating wavelength, the size of the proposed single layer FSS is 0.066λ0 (λ0 is the free space wavelength at 3.81 GHz). The performance such as transmission and reflection coefficient of the proposed FSS demonstrates excellent resonance stability for different polarization and different incident angles. Finally, the optimized simulated results are validated with measured results by a fabricated prototype of 31×31 array elements on 170×170 mm2 substrate area.

Design of Active Frequency Selective Surface with Curved Composite Structures and Tunable Frequency Response

We present an active frequency selective surface (AFSS) consisting of a curved composite structure that provides structural stability and robustness. The proposed structure can operate on either the C-band (OFF state) or X-band (ON state) by controlling the PIN diode located between the cross-shaped loop and the inductive stub on the surface. Moreover, it minimizes parasitic couplings through grid-type on/off bias circuits and via holes. Thus, the AFSS guarantees isolation from the unit cell, which is a downside of a previous control technique called reconfigurable frequency selective surface. We analyzed the impact of composite structures and the three-dimensional shape on the AFSS transmission with a foam-core sandwich structure, which is light and mechanically strong, by considering conditions of a real application environment.

Easily Optimizable Dual-Band Frequency-Selective Surface Design

Mutual interference between indoor adjacent wireless networks is becoming an important issue as it reduces the communication speed significantly. Isolating the wireless networks by using frequency-selective surfaces (FSSs) can be an efficient solution for such interference problems. As a solution proposal, a new periodic element geometry design, which stops incoming 2.4 and 5.8 GHz industrial, scientific, and medical radio (ISM) signals, is presented in this work. Mutual effect between each resonator (2.4 and 5.8 GHz) mostly leads to the optimization stage's being inadequate or time consuming at multiband FSS designs. Therefore, a new simple design technique is presented to be able to optimize each resonance frequency independent from the other. Besides, as an important feature, this technique also allows adjusting the frequency interval between the stopbands. Analysis of the proposed surfaces is executed with Ansoft HFSS v.15 software.

Design and Analysis of Ultrathin Polarization Rotating Frequency Selective Surface Using V-Shaped Slots

A novel polarization rotator design is demonstrated theoretically as well as experimentally based on frequency-selective surface (FSS). The polarization rotator selectively allows the linearly polarized incident wave to pass through the structure and rotates it by $\text{90}^\circ$ in a given frequency band. The periodic element of the FSS design consists of orthogonally oriented V-shaped slots on two metal sheets with the dielectric substrate separating the sheets. The proposed structure exhibits a relative bandwidth of $\text{8}\%$ (9.76–10.57 GHz) with a maximum insertion loss of 0.5 dB. Copolarized reflection coefficient is less than −10 dB in the same frequency band. The novelties of the structure lie in its reduced thickness ( $\text{0.053}\lambda _o$ ) as well as compact design ( $\text{0.28}\lambda _o$ ) as compared to the existing polarization rotators. A prototype has also been fabricated, and good agreement between the simulated and experimental results is observed.