Genetically engineered multiband high‐impedance frequency selective surfaces

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.

The uniplanar compact, affordable, and unique slot‐based multiband frequency selective surface (FSS) of periodic cell size 0.14λc × 0.14λc (λc is wavelength at the initial stopband resonance) is presented in this article. The quadband FSS is analyzed using full‐wave simulation, circuit simulation (ECM), and experimental measurement where good agreement is attained. The FSS offers polarization independence with steady responses for all angular variations in the TE plane and up to 45° in the TM plane. The FSS offers dual stopbands at 2.75–4.15 and 9.45–12.48 GHz and dual passbands at 0.001–0.8 and 4.74–5.6 GHz that includes spectrum coverage of GSM, LTE, WLAN, ISM, WiMAX, and most part of X‐band communication.

This paper has developed a multiband single-layer frequency selective surface (FSS) designed by using the optimization technique (micro-genetic algorithm). The characteristics of the designed FSS are superior to those of the Fractal FSS in the close dual-band separation and to those of the convoluted double square loop FSS in the bandwidth. We design the FSS for transmitting L and S bands and reflecting Ku and Ka bands. The agreement between the calculated and measured transmission responses for the designed FSS proves the validity of the present method.

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 this letter, the combination of a multilayered dielectric structure, a capacitive frequency selective surface (FSS) and a perfectly electric conducting (PEC) ground plane is proposed for realizing high-impedance surfaces. These surfaces behave like an artificial magnetic conductor (AMC) in a specific frequency range; the inclusion of the dielectric layers allows us to enhance the angular properties of the AMC as well as the frequency bandwidth of the device. In order to obtain the proper values of the design parameters, a genetic algorithm (GA) is employed that makes use of an electromagnetic solver based on the method of moments (MoM) to evaluate the scattering properties of the structure. A key step in the design procedure is the inclusion in the fitness function of the electromagnetic response of the high-impedance surface with respect to the illumination angle. The synthesized structure shows the desired frequency performance and reveals robust as concerns the stability of the solution with respect to a wide interval of illumination angles.

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.

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.

A technique is proposed for the design of multiband frequency selective surfaces (FSSs) that is based on the use of fractal screen elements. The authors demonstrate the design methodology by exploiting the self-similarity of the crossbar fractal to implement a tri-band FSS. Another benefit of this design approach, in addition to its multiband performance, is that the frequency response of both the TE and TM modes are exactly the same, owing to the symmetry in the tree-like fractal structure of the screen elements. Dielectric loading effects have been considered for practical implementation of designs with coverage exceeding two bands. Finally, it is noted that the locations of the individual bands can be controlled by the scaling or similarity factor used in the construction of the fractal screen elements.

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.

Purpose Planar periodic metallic arrays behave as artificial magnetic conductor (AMC) surfaces when placed on a grounded dielectric substrate, and they introduce a zero-degree reflection phase shift to incident waves. The antenna designers have new challenges while designing the AMC structure. The steps followed in designing the structure are as follows: 1) Designing the antenna, aimed to operate at millimetric wave frequencies, (2) Designing the AMC at desired frequencies, (3) Integrating the antenna design and AMC to resonate at millimetric wave frequencies and (4) Validate the output parameters of the antenna to be suitable for Internet of Things (IoT) applications. Design/methodology/approach The antenna is integrated with artificial material known as high impedance surface (HIS) for performance enhancement. A miniaturized, multiband, enhanced gain, AMC-integrated CPW-fed antenna is proposed and aimed to operate at millimetric wave frequencies, which is most suitable for IoT applications. The developed antenna operates at an extremely high range (30–300 GHz), i.e. from 40 to 60 GHz with the return loss values at lesser than −20 dB, and gain is greater than 10. The antenna is developed and simulated by using HFSS software. Findings An extensive research study has been carried out to develop a low profile, high gain and optimized antenna. The first two steps are separately designing the antenna and the AMC unit cell at the desired frequencies. The third step is finding the antenna or AMC radiating parts responsible for each resonant frequency by analysing the surface current distribution. CPW fed along with AMC integration has made the antenna feasible to achieve the extremely high frequency (EHF) range, i.e. 40–60 GHz, which is highly adoptable in IoT applications. Originality/value The result represented that the developed antenna is resonating at EHF rank with high gain and good imped matching when it is being compared with the previous models and has only CPW fed without having AMC structure integration. It is evident that the antenna which has only CPW fed has resonated at lower frequency than EHF range and justified output characteristics. But when it is embedded with the AMC structure, it resonates at the EHF range, which makes the antenna highly suitable for IoT applications, with more accuracy and high data rate possibility.

This work studies the integration of a semicircular shaped array antenna into an Artificial Magnetic Conductor (AMC) which resonate at the desired operating frequency of 9.41 GHz. The proposed AMC performs as a high impedance surface with a high permeability (approximately 7.08) at 9.41 GHz, with a perfect magnetic conductor characteristic. As result, the AMC is able to be stacked adjacent to the semicircular shaped. The simulation results show that the AMC has successfully enhanced the gain and efficiency of the antenna to 9.55 dB and 97% respectively compared to 8.44 dB and 96% without AMC. Besides that, a slight bandwidth improvement, from 395 MHz to 398 MHz can be observed with the AMC. Both simulated and measured results show a good agreement in term of reflection coefficients and radiation patterns.

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.

This paper focuses on different High Impedance Surface (HIS) geometries, also known as artificial magnetic conductors (AMC), to compare their performances in terms of frequency bandwidth and size. The main objective is to maximize the HIS bandwidth to perform an antenna association. Most of well known HIS cells are introduced and compared to new cells' geometries able to perform HIS properties in a wider frequency range. For each cell geometry, we have compared the HIS bandwidth (i.e. the frequency band where the reflexion coefficient phase is between -90° and 90°) and the cell size (with the aim of reduce their dimensions). This paper shows that cells geometries based on spirals allow to increase the HIS performances and bringing to light several optimization parameters increasing HIS bandwidth.

In this letter, the bandwidth of high-impedance surfaces (HISs) is discussed by an equivalent circuit approach. Even if these surfaces have been employed for almost 10 years, it is sometimes unclear how to choose the shape of the frequency selective surface (FSS) on the top of the grounded slab in order to achieve the largest possible bandwidth. Here, we will show that the conventional approach describing the HIS as a parallel connection between the inductance given by the grounded dielectric substrate and the capacitance of the FSS may induce inaccurate results in the determination of the operating bandwidth of the structure. Indeed, in order to derive a more complete model and to provide a more accurate estimate of the operating bandwidth, it is also necessary to introduce the series inductance of the FSS.We will present the explicit expression for defining the bandwidth of a HIS, and we will show that the reduction of the FSS inductance results in the best choice for achieving wide operating bandwidth in correspondence with a given frequency.