Finite Frequency Selective Surfaces Research Articles

High Selectivity FSS With Three Independently Controllable Transmission Poles Using Matrix Synthesis

In this letter, a high selectivity frequency selective surface (FSS) with three independently controllable transmission poles (TPs) is proposed by using matrix synthesis. The response with three TPs and four transmission zeros is obtained by employing a triplet topology. The matrix synthesis method provides a theoretical analysis for coupling elements regarding to three independently controllable TPs. Also, the synthesized matrix gives a good prediction of flexile responses with allocated center frequency and bandwidth. To be verified, a finite FSS prototype with 15 × 15 unit cells is fabricated and tested. The measured results are mostly consistent with simulated and synthesized ones, manifesting merits of high selectivity, flexible design, and low profile.

3D conformal bandpass millimeter-wave frequency selective surface with improved fields of view

Conventional planar frequency selective surfaces (FSSs) are characterized in the far-field region and they are sensitive to the incidence angle of impinging waves. In this paper, a spherical dome FSS is presented, aiming to provide improved angular stable bandpass filtering performance as compared to its planar counterpart when the FSS is placed in the near-field region of an antenna source. A comparison between the conformal FSS and a finite planar FSS is presented through simulations at the frequency range between 26 to 40 GHz in order to demonstrate the advantages of utilizing the conformal FSS in the near-field. The conformal FSS is 3D printed and copper electroplated, which leads to a low-cost and lightweight bandpass filter array. Placing it in the near-field region of a primary antenna can be used as radomes to realize compact high-performance mm-wave systems. The comparison between simulated and measured conformal FSS results is in good agreement. The challenges that arise when designing, manufacturing, and measuring this type of structure are reported and guidelines to overcome these are presented.

Efficient numerical analysis of finite FSS with multilayered media by MLACA

In this study, an efficient numerical technique for transmission characteristic analysis of finite planar frequency selective surface (FSS) with multilayered media is presented by using the multilevel adaptive cross approximation (MLACA). The computational scheme is based on the mixed-potential electric field integral equation (MPIE) with multilayered media Green's functions (MLGFs). The three-level modified discrete complex images method (DCIM) is presented for the spatial-domain MLGFs without any quasi-static and surface-wave extraction. For electrically large-size FSS structures, the MLACA method is then employed to alleviate the high computational complexity and memory requirement of method of moments. Numerical results are presented to demonstrate the accuracy and efficiency of the proposed method.

Analysis of Finite Size Nonuniform Stable and Multiband FSS Using a Generalization of the WCIP Method

A generalization of the wave concept iterative procedure method is proposed and used in the analysis of finite size and nonuniform frequency selective surfaces (FSS). The nonuniformity of the FSS is obtained by mixing different shapes of elements in the finite size FSS structures consisting of circular patch elements with and without radial slits. The shapes of the radial slit elements are defined according to a fractal-like formation rule, where the circular patch without radial slits is the generator. Single or multiband frequency performances can be obtained, enabling the design of reconfigurable FSS. In addition, a high stability of the incidence angle of the plane wave is confirmed. A good consistency is observed among theoretical, simulation, and experimental results.

Reconfigurable and stable frequency selective surfaces on nonuniform and finite arrays

AbstractA reconfigurable frequency selective surface (FSS) is presented based on a nonuniform and finite array of square loop conducting patches printed on a dielectric substrate. The reconfigurability is performed changing the polarization of PIN diodes in the patch elements of the FSS array, from OFF to ON state and vice versa. Simulation is performed by the wave concept iterative procedure (WCIP) formulation and Ansoft HFSS package. Remarkably, a generalization of the WCIP method is proposed to solve scattering problems on FSS structures composed of nonuniform and finite arrays. Prototypes are fabricated for comparison purpose. Simulations and measurements show that the nonuniform and finite FSS has dual band behavior and stable frequency response for different angles of the incident plane wave. A very good agreement between HFSS simulation, WCIP formulation, and experimental results is verified.

Analysis of finite frequency selective surfaces backed by dielectric substrate using sub-entire-domain basis function method

Purpose – Analysis of the frequency selective surface (FSS) is of great significance. In the method of moments, when the electric size of the FSS increases, huge in-core memory and CPU time are required. The purpose of this paper is to efficiently analyze the finite FSS backed by dielectric substrate utilizing sub-entire-domain (SED) basis function method. Design/methodology/approach – Different types of SED basis functions are generated according to the locations of the cells in the entire structure, and a reduced system is constructed and solved. The couplings of all cells of the FSS are taken into account by using Green’s function and Galerkin’s test procedure. The spatial Green’s function is obtained with the discrete complex image method. The reflection and transmission coefficients of the FSS are calculated using the far field of the FSS and the metallic plate with the same size. Findings – Moderate problems of the finite FSS backed by dielectric substrate are solved with the SED basis function method. The original problem can be simplified to two smaller problems. It enables a significant reduction to the matrix size and storage, and efficient analysis of FSS can be performed. The band-stop type of FSS can be composed of periodic conductive patch cells on the dielectric substrate, and shows total reflection property at the resonant frequency. Originality/value – The SED basis function method is mostly used to analyze periodic PEC structures in free space. The layered medium Green’s function is successfully employed and several dielectric substrate backed finite FSSs are discussed in this paper. The calculation of reflection and transmission coefficients, which are more effective rather than far field scattering of the FSS, are described.

Numerical Diffraction of Array-Guided Surface Waves on Finite Frequency Selective Surfaces

In this paper, an adaptation of Hurst's method to take into account the presence of array guided surface waves in the calculation of the scattered field of finite frequency selective surfaces in free space is presented. Numerical approaches to determine the guided wave's wavenumber needed in this calculation, namely Prony's method and the discrete Fourier transform (DFT), are examined and compared. The results show that the scattered fields obtained with the proposed method, which is based on numerically extracted diffraction coefficients, are in very good agreement with those obtained with the method of moments.

Triple-Band Frequency-Selective Surfaces to Enhance Gain of X-Band Triangle Slot Antenna

A new modified microstrip triangle slot antenna is first investigated and designed at X-band. By adding two rectangular slits in the edge of the radiating aperture and adjusting the dimension of the feeding stub, a very good impedance matching within the X-band is obtained. Afterwards, by using microstrip transmission line (suspended line) and unit-cell box analyses, a new triple-band frequency selective surface (FSS) is designed that is compoed of three conductor-based split-ring resonators, connected together. The effect of the unit-cells periodicity in the finite FSS alone and the antenna with FSS behaviors is discussed. Moreover, the different distances between the antenna and FSS surfaces are experimentally analyzed. For this purpose, two foam-based holders along with a compound prototype of the antenna and FSS are manufactured. Return loss, radiation pattern, and gain of the antenna with an increment of about 2.5 dB without disturbing the matching and bandwidth are presented.

유한크기 FSS의 곡률효과에 따른 주파수 특성 해석

In this paper, we have analyzed the curvature effects of the finite FSS(frequency selective surface) using the 3-D method of moment using the BiCGSTab algorithm as an iterative method. To validate the analysis method in this paper, we compared the RCS(radar cross section) of PEC(perfect electric conductor) sphere with theoretical results and it shows well agreements. The tripole slot FSSs which have many application in military were selected for the investigation of curvature effect and RCS as a frequency characteristics were observed with the variation of the curvature rate. Simulation results shows that curvature effect can significant effect the passband frequency and bandwidth of FSS. We suggest that the curvature effect must be considered at the stage of design FSS application like FSS radome.

Multiresolution preconditioned multilevel UV method for analysis of planar layered finite frequency selective surface

In this article, the planar layered finite frequency selective surface (FSS) is analyzed by the mixed potential integral equation. The multiresolution (MR) preconditioned multilevel UV method is applied to accelerate the matrix-vector multiplication. The MR preconditioning technique is based on the construction of MR basis functions, which are constructed as linear combinations of Rao-Wilton-Glisson (RWG) basis functions. Therefore, the MR-preconditioner allows direct application to the multilevel UV method with RWG basis functions to speed up the convergence of the generalized minimal residual iterative solver. Numerical results demonstrate that the MR preconditioned multilevel UV method is efficient for the analysis of planar layered finite FSSs. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1530–1536, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25233

SIMULATION AND EXPERIMENTAL VERIFICATION OF W-BAND FINITE FREQUENCY SELECTIVE SURFACES ON INFINITE BACKGROUND WITH 3D FULL WAVE SOLVER NSPWMLFMA

We present the design, processing and testing of a W-band finite by infinite and a finite by finite Grounded Frequency Selective Surfaces (FSSs) on infinite background. The 3D full wave solver Nondirective Stable Plane Wave Multilevel Fast Multipole Algorithm (NSPWMLFMA) is used to simulate the FSSs. As NSPWMLFMA solver improves the complexity matrix-vector product in an iterative solver from O(N(2)) to O(N log N) which enables the solver to simulate finite arrays with faster execution time and manageable memory requirements. The simulation results were verified by comparing them with the experimental results. The comparisons demonstrate the accuracy of the NSPWMLFMA solver. We fabricated the corresponding FSS arrays on quartz substrate with photolithographic etching techniques and characterized the vector S-parameters with a free space Millimeter Wave Vector Network Analyzer (MVNA).

A Novel Dual-Band Spiral Antenna for a Satellite and Terrestrial Communication System

In this letter, a new dual-band planar spiral antenna is proposed. This antenna is realized by incorporating a finite frequency-selective surface (FSS) into a planar spiral antenna as its ground plane. Because of the added FSS, a broadband spiral antenna can be transformed into a dual-band antenna. Especially, the main-beam directions associated with these two bands can be widely separated more than 60deg. Therefore, the antenna can be simultaneously applied to satellite and ground-based communications. A prototype of this FSS-added spiral antenna was created and examined. The simulated and measured results obtained demonstrate its promising performance.

A comparison between two hybrid techniques for the scattering from finite frequency‐selective surfaces

AbstractThe scattering from finite frequency selective surfaces (FSSs) characterized by planar interfaces is analyzed, resorting to two PO‐based hybrid techniques. The hybrid techniques, validated with a full‐wave numerical technique, are easy to implement, fast, and already quite accurate for medium‐size FSSs. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 31: 248–252, 2001.

Scattering from surface waves on finite FSS

This paper discusses the presence of surface waves on periodic structures in general and on frequency selective surfaces (FSS) in particular. While certain types of surface waves can exist on infinite as well as finite periodic structures, this investigation centers around the types that can exist only on finite FSS. Radiation caused by these surface waves may lead to a significant scattering increase in the backscatter as well as the bistatic directions. Thus, this paper is of both theoretical and practical interest.

Rigorous analysis of frequency selective surfaces of finite extent using a hybrid finite difference time domain–boundary integral equation technique

A hybrid finite difference time domain–boundary integral equation approach is used to model frequency selective surfaces of finite extent. Using the finite difference time domain technique, a system matrix is constructed for a box enclosing all relevant features within a unit cell. The open character of the finite frequency selective surface is modeled by coupling a boundary integral equation formulation to the system matrix found with the finite difference time domain approach. A number of relevant examples are studied, and a comparison is made between our new technique and the more classical finite difference time domain technique or the hybrid finite element–boundary integral equation method.

Spatial Decomposition and Reduced Current Fidelity for the Analysis of Tm Scattering From Large 2d oBjects

An investigation of the spatial decomposition technique (SDT) for the analysis of electrically large objects is presented. We apply SDT to two-dimensional perfectly conducting cylinders under TM excitation. Some of the convergence issues of the SDT as well as its application to finite arrays (finite frequency selective surfaces) are discussed. We also present a new method to obtain a reduction in the operation count of SDT, which is referred to as "reduced current fidelity (RCF)." With RCF the coupling between distant SDT subobjects is determined by use of a coarse grid on which currents are obtained from those on a dense grid. An averaging of the currents on distant objects reduces the operation count involved in determining the coupling to other subobjects. It is shown that for electrically large structures, RCF can provide significant reduction in operation count and good accuracy in the resulting structure currents.

Ray tracing analysis of the transmission performance of curved FSS

Finite frequency selective surfaces (FSS) embedded in a curved dielectric are analysed using the ray-tracing technique. The FSS is treated as an infinitesimally thin interface with known complex reflection and transmission coefficients subjected to multiple interactions with rays internally reflected within the dielectric. Results for flat surfaces agree well with those computed using a full modal analysis. The transmission properties of such arrays are studied as the curvature is steadily increased for the case of paraboloids illuminated by plane waves, and also when enclosing a finite aperture-type antenna. The results obtained are validated by measurement.

Improved numerical diffraction coefficients with application to frequency-selective surfaces

A method for numerically determining diffraction coefficients for arbitrary scattering centers is described. In this method finite bodies possessing scattering centers of the type of interest are first analyzed via the moment method. The various contributions to the total scattered fields are then isolated by solving low-order simultaneous equations obtained by writing expressions for the fields in terms of unknown diffraction coefficients. The method yields numerical diffraction coefficients in angular sectors where previous methods fail (e.g., near grazing angles), and can be applied in the context of measured as well as simulated scattering data. Finite frequency-selective surfaces are shown to be amenable to analysis with ray-optics techniques, and several two-dimensional examples are given with comparisons to far- and near-field moment method results. >

Numerical analysis of finite frequency selective surfaces with rectangular patches of various aspect ratios

The finite frequency selective surface studied consists of a two-dimensional array, finite in one dimension and infinite in the other, of perfectly electrically conducting plates in free space. The analysis uses a Green's function formulation in the spectral domain, and the resulting equation is solved using the method of moments. Techniques are demonstrated for increasing the speed of the numerical computation so that the problem can be solved on a VAX 11-780 in a reasonable amount of time. Two types of basis functions, one subsectional and the other complete domain, are used to represent the currents on the patches. Both yield similar results and both are suitable for use in this problem. Techniques are demonstrated for approximating the tails of the infinite integrations which allow a more accurate solution than truncation. Results for scattered power density and patch currents illustrate the edge effect and incident angle dependencies. Results showing 3 dB bandwidth, resonance peak versus frequency, and scattered power versus frequency are plotted for patches with aspect ratios varying from 0.1 to 1. >

Finite and Infinite Frequency Selective Surfaces: Experiments and Models

The scattered fields from several finite frequency selective surfaces (FSS's) are presented along with frequency response data for an FSS which is large enough to be considered infinite. Measurement techniques for both the infinite and finite FSS are discussed and the experimental results are compared with numerical data generated using both a moment method for the infinite FSS and the array factor for the finite case.