Patch Frequency Selective Surface Research Articles

Tri-Band, Stable and Compact Patch Frequency Selective Surface Optimized via Hybrid Bioinspired Computing for Applications at 2.4, 3.5 and 5.8 GHz

This work addresses the synthesis of a multi-band frequency selective surface (FSS) through bioinspired computing and a general regression neural network (GRNN). This hybrid computational method, which utilizes the multi-objective cuckoo search algorithm combined to a GRNN, determine the best physical dimensions of the FSS in order to achieve a multi-band filtering at the 2.4, 3.5 and 5.8 GHz spectrums. Therefore, the results are to be applied to aid the propagation of Wi-Fi, WLAN, WiMAX and future sub-6 GHz 5G systems. The resonant frequencies were measured and a -10 dB cutoff value has been considered for the transmission coefficient. The triple rectangular loop conductor geometry of the device is printed upon a glass epoxy (FR-4) substrate. Measurements were made for different wave incidence angles, from 0° up to 45°, to demonstrate how signal incidence would affect the device’s functioning. The agreement between simulated and measured data display satisfactory results.

Analysis, Design, and Implementation of a New Extremely Ultrathin 2-D-Isotropic Flexible Energy Harvester Using Symmetric Patch FSS

Electromagnetic (EM) energy exists far and wide in the environment and can be harnessed and transferred to the desired load(s). The researchers mostly designed and implemented the planar metasurface energy harvester (MEH) offering a restricted look-angle. In this article, we propose an extremely ultrathin 2-D-isotropic flexible MEH using multipolarized patch frequency selective surface. This MEH, which has a curved shape, enjoys a relatively constant performance over a huge range of oblique incident waves. The final structure can be prepared by a small slice of a cylinder. A classic model inspired from the dipole antenna concept is used for impedance matching. Theoretical analyses, design, and fabrication of the structure are presented using a deep subwavelength PCB substrate having a thickness of $\sim 0.004~\lambda _{0}$ . EM energy harvesting is analyzed with an equivalent circuit model. The experimental results are acceptably in agreement with the simulation results. The design can be scaled to different RF bands; however, to provide the required energy for Internet-of-Things (IoT) instruments, we have used WiFi as a crowded frequency band. The simulation efficiency of the flat style extremely ultrathin MEH (EMEH) for normal incidence (at 5.81 GHz) and 60° oblique angle incidence with transverse magnetic (TM) and transverse electric (TE) polarizations are 87.35%, 93.26%, and 64.42%, respectively. In addition, half power bandwidth (HPBW) for these situations is 6.97%, 8.86%, and 5.61%, respectively.

Comment on “Circular-to-linear polarization converter based on composite via-coupled patch frequency selective surfaces”

Comment on “Circular-to-linear polarization converter based on composite via-coupled patch frequency selective surfaces”

Design of Ultrawide Bandwidth Electromagnetic Wave Absorbers with Square Patch Frequency Selective Surfaces with Different Geometries

A reliable and efficient numerical method is presented for the design of broadband absorbers, fabricated by layering two square patch-frequency selective surfaces (SP-FSS) with different geometries on a grounded dielectric substrate. The circuit parameters of the inductance and capacitance of the SP-FSS were retrieved using the strip wire conductor model. Due to the high capacitance and low inductance of the SPFSS, a nearly constant resonance frequency (<i>f</i><sub>0</sub> = 37 GHz) is observed, irrespective of patch size at a given unit cell periodicity of 7.5 mm. For the SP-FSS, the circuit is capacitive below <i>f</i><sub>0</sub> and inductive above <i>f</i><sub>0</sub>. For a grounded substrate with a quarter wavelength thickness, however, the input impedance is inductive below <i>f</i><sub>0</sub>, resulting in impedance matching over a wide frequency range, with the controlled FSS resistance matched to the free-space impedance. The double-layer absorber was designed by optimizing the surface resistance and layer thickness of two SP-FSSs with different geometries, and demonstrated a 10 dB absorption bandwidth of 6.1−41.4 GHz with a total thickness of 5 mm, which is equal to the theoretical limit. A test sample was prepared by screen printing method, and the free space measurement demonstrated a wide-bandwidth absorption result (4.7−40.0 GHz for −10 dB reflection loss) with a small total thickness (5.4 mm). The simulation and experimental results strongly validated the SP-FSS for the design of wide bandwidth electromagnetic wave absorbers.

Reflection and transmission characteristics of frequency selective surface embedded within a thick plasma layer

In this paper, the reflection and transmission characteristics of frequency selective surface (FSS) embedded within a thick plasma is studied. The plasma layer is lossy and dispersive medium and the embedding of the FSS will change the electromagnetic wave propagation very much. The reflection and transmission coefficients of a square patch FSS layer embedding in plasma is calculated utilizing finite-difference time-domain (FDTD) method. Auxiliary differential equation (ADE) is utilized to simulate the dispersion of the plasma. The influence of the plasma and slab's parameter to the reflection and transmission coefficients is investigated. Various parameters of collision frequency, plasma frequency and thickness of plasma are involved to study the influence of these factors. The reflection and transmission coefficient values of different parameters are plotted to compare their effects. The results show that collision frequency reduces the reflection and transmission coefficient. Plasma frequency changes the FSS from low pass filter to band pass filter. Thick plasma slab makes the transmission coefficient oscillate as the variation of incident frequency.

Novel synthesis formulas to design square patch frequency selective surface absorber based on equivalent circuit model

A new procedure is presented to design electromagnetic absorbers based on resistive square patch frequency selective surface (FSS) over grounded dielectric. The periodicity (p) and the distance between two adjacent squares in the lattice (w) are two unknowns to be solved, given the thickness and permittivity of the substrate, surface impedance of the square patches and the desired reflectivity in some specified frequency. Equivalent circuit model and transmission line method are employed here. Previously reported analysis formulas to calculate the square patch FSS admittance are exploited and novel synthesis formulas are extracted based of them. The final synthesis equations to calculate p and w are presented in term of polynomials. Usually an absorber is supposed to have a maximum reflectivity r in a frequency band [f1, f2]. The (p, w) pairs for reflectivity less than r in f1, define an area in p-w plane. The intersection of the so-called area with the similar one defined by f2 specifies all possible (p, w) pairs. Finally the results are tested and verified by the commercial full wave simulator Ansys-HFSS as well as some experimental design. There is a good agreement between the expected results with the full wave analysis and practical test.

Circular-to-linear polarization converter based on composite via-coupled patch frequency selective surfaces

In this paper, we present a design of circular-to-linear polarization converter operating in C-band based on a composite frequency selective surface which consists of two types of via-coupled patch modules. The building unit cell is built with four modules, and each one is a truncated patch pair printed on the double-layer substrate and vertically connected by a metal via-hole. A perforated common ground plane is sandwiched between the double layers to support transverse electric and magnetic mode coupling between the front and back patches. The front diagonally truncated patch array responds to the incident right-handed circularly polarized wave, and it is identically converted into general right- and left-handed elliptically or circularly polarized waves with same phase shifts, amplitudes and axial ratio, thus a resultant linear polarized wave is generated in forward transmission mode.

A WIDEBAND FREQUENCY SELECTIVE SURFACE REFLECTOR FOR 4G/X-BAND/KU-BAND

A Frequency Selective Surface (FSS) reflector with wideband response for 4G/X-band/Ku-band is proposed. The wideband FSS reflector consists of cascaded dual-layer patch FSS which is etched on separ ...

Design and fabrication of a fabric for electromagnetic filtering application (experimental and modeling analysis)

In this paper, a fabric with frequency selective surface (FSS) characteristics was developed for shielding of GSM-1800 frequency band global system for mobile communications (GSM). For modeling, two types of patch FSS models were developed through numerically solving the Maxwell’s equations using the Finite Integral Technique (FIT) method. In experiments an FSS fabric was developed by the embroidery method and a setup was prepared for evaluation of the shielding properties of the FSS fabric. Comparison of the results in 1805–1880 MHz frequency band showed a good agreement between resonance frequency responses of the model II and embroidery FSS fabric. The resonant frequency of the fabric was found to be less than that of the model I. However, the transmission and reflection coefficients of models I, II were same to each other. Results showed that in different incident angles, the frequency responses of the models I and II were not the same. However, the FSS fabric and model II were insensitive to such variations at 1805 MHz. Based on the numerical solution and the experimental results, this type of low-loss FSS fabric structure showed desired electromagnetic wave blocking properties in the desired bandwidth of 1805–1880 MHz.

Resonant characteristics of aperture type FSS and its application in directivity improvement of microstrip antenna

In this paper, we propose an aperture type frequency selective surface (FSS) by employing an array of 12×12 unit cell elements and its resonant characteristics is analyzed. A resonant cavity antenna is then formed by the ground plane substrate and the FSS superstrate. The high reflective behavior of the proposed FSS at an offset of the resonance is then utilized for improving the performance of this cavity antenna. The impedance bandwidth and directivity are improved up to 0.66GHz and 8.95dBi, simultaneously at an optimum gap of 17.6mm between the antenna substrate and FSS superstrate. For validation purpose, prototypes of both patch antenna and FSS, are fabricated and characterized. A fairly good agreement is achieved between the measured and simulated results.

Equivalent Circuit Model for the Frequency-Selective Surface Embedded in a Layer With Constant Conductivity

In this paper, an equivalent circuit model for a frequency-selective surface (FSS) embedded in a layer with constant conductivity is proposed and investigated. Because the medium surrounding the FSS is lossy, the equivalent model consists of not only inductance and capacitance elements but also resistive elements. The reflection response of a square patch FSS embedded in the conductive slab is simulated in a wideband of frequency. Then, all circuit elements are extracted by genetic algorithm optimization, when the reflection coefficient achieved from the equivalent circuit model is the same as the one obtained by numerical simulation. It is also found that the behavior of the model is consistent with that of the simulated one with a good accuracy. Values of the model elements are plotted by the variation of the conductivity and permittivity of layer, and the effects of these parameters are studied on the values of circuit elements. Moreover, it is shown that the obtained model can be applied to determine the model of FSS used in practical absorbers.

Equivalent Circuit Model for Frequency-Selective Surfaces Embedded Within a Thick Plasma Layer

In this paper, an equivalent circuit model for a frequency-selective surface (FSS) embedded in a thick plasma layer is introduced. The plasma layer is a lossy and dispersive medium, and therefore, the equivalent model is not purely imaginary and consists of resistive elements as well as inductance and capacitance elements. First, a square patch FSS is simulated in a wide frequency range from 1 to 25 GHz by a full-wave electromagnetic software, and then all the circuit elements are calculated by genetic algorithm optimization to achieve reflection coefficient similar to the one obtained by simulation. It is shown that this model can mimic the simulated behavior with good approximation. Then values of different elements of the model through practical variations of cold plasma parameters are plotted, and the effects of electron density and collision frequency are investigated on circuit elements.

Dual‐polarized multiband frequency selective surface with miniaturized hilbert element

AbstractA novel Hilbert frequency selective surface (FSS) is proposed and experimental studied. By etching the FSS elements as two iteration Hilbert curve and arraying the Hilbert FSS elements symmetrically, it is experimentally found that the proposed FSS is dual‐polarized, and several stopbands are exhibited within the operating frequency band. It is also observed that the proposed Hilbert FSS element achieved a size reduction of 93.6% when compared to the conventional square patch FSS resonated at the similar frequency. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1221–1223, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27570

The Design and Performance of a Novel Square-Loop Patch Frequency Selective Surface

A novel stop-band Frequency selective surface (FSS) is presented. By adding four narrow branches to conventional square-loop FSS, the proposed FSS can achieve a good frequency stability for different oblique angles and a high frequency selective ability. An equivalent circuit model is used to simply analyze its transmission property. The good agreement between simulated and measured results shows the validation of our design.

A novel investigation on size reduction of a frequency selective surface

AbstractThe study presents theoretical and experimental investigation of a novel, reduced size Microstrip Frequency Selective Surface. The novel design is achieved by cutting some rectangular slots at four sides of a square patch. Compared with conventional square patch Frequency Selective Surface (FSS), this slotted square patch Microstrip FSS can achieve reduction in patch area of 36%. The structure acts like a band pass filter with a resonant frequency 8 GHz. Both theoretical and experimental investigations are done. Theoretical investigation is done by IE3D software. Experimental investigation is performed using standard microwave test bench. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2820–2821, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22833

Frequency selective volumes for optical spatial filters

A new model is proposed for modeling metallic losses at optical frequencies and is used in the analysis of frequency selective surfaces (FSSs) and volumes (FSVs). Conventional methods for simulating metallic losses are also outlined and a comparison with those models is given for a patch FSS. Measured data for a slot-ring FSS are also given for model validation.

Spectral-domain analysis of circular patch frequency selective surfaces

A computationally efficient method is presented for analyzing the scattering from frequency selective surfaces (FSS) comprised of circular metal patches. The formulation is carried out in the spectral domain where the convolution form of the integral equation for the induced current reduces to an algebraic one and the spectral-Galerkin technique is used to solve the resulting equation. Entire-domain basis functions that satisfy the edge condition are introduced to expand the unknown induced current on the metal patches. Calculated results using this procedure show good agreement with data reported by other authors.