Simple and efficient design of reconfigurable FSS with triangular patch elements

In this paper, a dual-band Frequency Selective Surface (FSS) absorber is presented for Wireless Local Area Network (WLAN) security. The FSS absorber is designed for two frequencies of interest, i.e., 2.45 GHz (lower band) and 5.25 GHz (upper band), respectively. FSS design consists of two layers; first layer consists of conducting square-loop elements while second layer consists of resistive square-loop elements, placed in-front of a conducting FSS layer. The proposed FSS design provides good frequency stability for oblique incidences for perpendicular (TE) and parallel (TM) polarizations. It provides better absorption rate for 2.45 GHz and 5.25 GHz frequency bands and allow the transmission of other microwave frequencies. Also, the proposed FSS design reduces multipath fading of additional WLAN signals which occurred due to the placement of conducting FSS layer. Presented results demonstrate that the proposed FSS design has a stable frequency response for the desired frequency bands for TE and TM polarizations with good absorption rate when the incident wave angle varied from 0<SUP>0</SUP> to 45<SUP>0</SUP>.

In order to make the dual-band frequency-selective surface (FSS) used in the engineering conditions of thick substrate, wide band spacing and large incident angle, an FSS structure with dual-band at Ku-band and Ka-band is presented. The stable filtering condition of the FSS is analyzed by using the grating lobe diagram, and the transmission of the FSS with combination or fractal elements is calculated using the vector modal matching method. The design method of the dual-band FSS with thick substrate is obtained by analyzing the resonance mode of the element and the transmission of the FSS. By using those methods, an FSS with combination elements of the square and Y loops is designed. The simulated and tested results show that the dual-bands of the structure at Ku-band and Ka-band are stable and the transmissions of the two pass-bands are larger than 75% when the incident angle is varied from normal to 45. This paper provides some theoretical and experimental references for the design of the dual-band FSS with thick substrate, wide band spacing and large incident angle.

A novel 3D Frequency Selective Surface (FSS) with horn shaped resonators is proposed which exhibits a very wide stop band. This new horn shaped resonator is a modification from a 3D FSS consisting of square cylinder unit elements. This feature introduces frequency-selective surfaces with the added advantage of lowering the sensitivity of the FSS frequency response with respect to the incidence angle. Simulation results prove that the FSS can realize broad selectivity of waves with the bandwidth more than 57%. The wideband transmission behavior is stable under oblique TM incidence angles from 0 to 80 degrees. The influence of various key parameters on 3D Horn Shape FSS characteristics has been investigated using the CST simulation software tool. By understanding the effect of each parameter, a comprehensive study for a better design of 3D Horn Shape FSS with wideband response is presented.

This thesis presents the development and the additive manufacturing of smart antennas and frequency selective surfaces (FSS) for microwave, millimetre wave, and low-Terahertz applications. Numerous fabrications techniques such as etching, low-cost inkjet-printing, Fused Filament Fabrication (FFF) and Aerosol Jet Printing are employed to fabricate the antennas and FSS. Firstly, frequency reconfigurable antennas with close-coupled biasing technique are developed using double-sided etching on a thin mylar substrate for smart current and voltage sensing applications. The frequency tunable antenna also acts as a novel current sensing antenna in a smart sensing system that can sense the alternating current passing through a wire. The design is followed by introducing a low-cost inkjet-printed industry ready solution for frequency reconfigurable antennas where a single antenna aperture solution is utilised to demonstrate frequency reconfigurability in both switching and tuning configurations. Development of Frequency Selective Surfaces using low-cost printing machine is demonstrated in which FSS structures are inkjet-printed as wallpaper posters for Radio Frequency (RF) shielding and signal enhancements for 4G and 5G applications. A novel approach for fully 3D printing an FSS structure is also demonstrated using a low-cost open-source printer, which was modified to print the filament and the conductive inks simultaneously. Widespread investigation of industry-grade Aerosol Jet printing is utilised for additive manufacturing of bandstop and bandpass FSS designs for RF shielding and signal filtering. The bandstop designs are developed for microwave and millimetre-wave applications. The bandpass slot FSS designs are developed for millimetre wave and low-Terahertz applications for futuristic Beyond 5G and 6G systems.

In this paper, a new geometrical shape of the bandpass modified circular ring frequency selective surface (FSS) structure with significant electrical response such as angular stability up to $$50^{\circ }$$50? of the angle-of-incidence (AOI) for both the perpendicular (TE) and parallel (TM) polarized waves has been discussed. The geometrical parameters of the proposed bandpass FSS is obtained by the transformation of bandpass single square loop FSS structure parameters. To achieve the frequency response of the proposed bandpass structure, commercially available 3D electromagnetic simulators such as CST Microwave Studio and Ansoft HFSS are used. The proposed bandpass FSS structure provides significant angular (i.e., up to $$50^{\circ })$$50?) and polarization (i.e., perpendicular and parallel) stability as compared to that of various other reported literatures. In addition to this, one of the important characteristics of the resonant structure is the quality factor (Q-factor), which has also been discussed for the proposed bandpass FSS structure at different AOI.

This paper describes an antenna design for wideband high directivity operation using an aperture coupled patch antenna as the feeding source and an FSS (frequency selective surface) based structure as the superstrate for high directivity. The new antenna device combines the wideband characteristic of the aperture coupled antenna and the desirable characteristics of the FSS structure as a superstrate for high performance operation. A coplanar waveguide (CPW) feed design is used to obtain wideband performance for the feeding antenna. Both single layer and double layer based FSS designs are studied for improvement of directivity. The performance is further enhanced by using an air gap between the patch on a thin film substrate and the CPW and aperture structures on an FR4 substrate and also between the layers of a double layer FSS design. The air gaps can be produced using micromachined PMMA rims for low cost construction. An impedance bandwidth in excess of 50% has been obtained for a centre frequency of 10 GHz. The antenna device exhibits a directivity of about 13.6 dBi. A 1-dBi ripple radiation bandwidth as high as ∼42% has been achieved.

In this paper, the Minkowski fractal is used to design the geometry of a frequency selective surface (FSS) unit cell, which resembles the shapes found in nature. The proposed FSS unit cell has both angular and polarization stabilities of incident wave. For the miniaturization of FSS and decrease of resonance frequency, interdigital capacitances (IDCs) are devised in the FSS structure, which do not eliminate angular and polarization stabilities. The dimensions of the unit cell are 5 mm × 5 mm and miniaturized 0.095λ0×0.095λ0. The resonance frequency is specified as 5.75 GHz with 155 MHz bandwidth. An equivalent circuit is derived for the unit cell to evaluate its frequency responses. The effects of variations of the geometrical dimensions of the FSS unit cell on its performance are studied. A prototype model of proposed FSS is fabricated and measured. The performance of its full-wave computer simulation results and measured data are compared and are shown to be in good agreement.

Thicknesses of window glasses, radomes, plastic cases of wireless systems are comparable with the wavelength in the millimeter-wave band. The reflections from the dielectric plate surfaces are canceled out of phase when the thickness is identical to a half of the wavelength. However, they are not canceled at any other frequencies except integer multiple of a half wavelength. Therefore, return loss is a serious problem in the millimeter-wave band. A frequency selective surface (FSS) loaded to the dielectric plate controls reflection amplitude and phase, thus, return loss is canceled for various dielectric thickness and frequency. A complex scattering matrix (S-matrix) of FSS is represented by only reflection amplitude |S 11 | from the condition of zero thickness of FSS expressed by shunt suceptance. The total reflection is calculated by converting S-matrices of FSS and a dielectric plate to a transfer matrices (T-matrix) and synthesizing them. We propose to find the required characteristics of FSS from the desired characteristic of whole structure. Broadband characteristic was designed by inserting FSS at the center of the dielectric plate.

This work reveals the Design and development of Dual wide band frequency selective surfaces (FSS). Dual-band FSS based on single and multi layers with or without or extra discrete components has been discussed and analyzed. Dual wide band-pass FSSs has been designed and developed by using two metallic layers for the wide targeted pass band frequency bands range of 3.53-5.3 GHz and 3.53-4.21 GHz. In the initial step of Development ultra thin double layer slotted FSS has been used. These generate resonance at 4.0 GHz and 4.8 GHz. Furthermore Hilbert shaped slotted resonator increase pass band width enhancement. Lastly the opposite alignment of similar FSS metallic plate to form the proposed dual layer FSS which exhibit the bandwidth enhancement of the frequency bands.

Fractal geometries have been extensively implemented in the design of multiband antenna and frequency selective surface (FSS). For example, convoluted and Hilbert patch elements were first proposed to reduce the unit cell size of FSS (Parker and El Sheikh, IEE Proc.-H, 138, 19–22, 1991.) A fractal FSS with self-similar Sierpinski dipole array was shown to have two stop bands (J. Romeu and Y. Rahmat-Samii, IEEE Trans., AP-48, 1097–1104, 2000). However, its resonant frequencies are rather sensitive to incident angles and polarizations. Minkowski patch FSS and Sierpinski carpet fractals have been shown to provide two or three stop bands with dual polarization capability (J.P. Gianvittorio, et. al., IEEE Trans., AP-51, 3088–3096, 2003.) Recently miniature band-pass FSS with fractal antenna-filter-antenna arrays was designed and demonstrated with good frequency selectivity (S. Zheng, et. al., IEEE AWPL, 11, 240–243, 2012.) A dual band fractal FSS with a 3:1 reflection to pass band ratio and significantly improved resonant frequency stability was proposed by the author (T.K. Wu, Microwave Optical Tech. Letters, 54, 833–835, 2012).

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.

A novel frequency selective surfaces (FSS) based on Y-loop fractal element is investigated using finite difference frequency domain (FDFD) method and verified with experiment in this paper. Numerical and experiment results show that the Y-loop fractal FSS has the advantages of low insertion loss in pass-band, good frequency selectivity and stability of bandwidth etc. Its performance is very stable at various incident angles and different polarization state. Besides, because over 90% of the surface covered with metal, the Y-loop fractal FSS obtains very high IR reflectivity, so the proposed FSS can also be used in MMW/IR compound system as dichroic beam combiner.

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.

This letter presents the design and testing of a novel triple-layer frequency selective surface (FSS) with ultraminiaturization for electromagnetic shielding applications. The proposed unit cell is constructed using meandered lines running along the three layers and they are interconnected using metalized vias to increase the electrical length of FSS. The FSS is designed to offer band stop resonance at L-band frequency with a foot-print of 0.022 λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">o</sub> × 0.022 λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">o</sub> with a thickness of 0.006 λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">o</sub> and it provides at least 38% of miniaturization in comparison with similar literature. To validate the transmission performance, a prototype FSS with a periodicity of 6 mm is fabricated. The FSS consists of 2500 elements arranged in a 50 × 50 square lattice. The transmission performance of the proposed FSS is verified using simulation and experiment. The proposed FSS has rotational symmetry and hence it is polarization insensitive. Furthermore, the FSS offers excellent angular stability up to the maximum incidence angle of 60° under both transverse electric and transverse magnetic modes of operation. The proposed FSS can be used for shielding applications in global positioning systems tracking and aircraft surveillance systems.

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.