Transmission Improvement of UMTS and Wi-Fi Signals Through Energy Saving Glass Using FSS

The transmission of infrared (IR) and visible frequencies through modern energy-saving glass, due to etching of bandpass frequency-selective surfaces (FSSs), is analysed. Energy-saving glass panels employ a very thin layer of metallic oxide on one side of the ordinary glass. Due to the presence of this layer, IR waves are attenuated whereas visible wavelengths can pass through, providing good see-through effect. However, one drawback with such energy-saving glass panels is that they also attenuate useful radio frequency (RF)/ microwave (MW) signals such as those used for mobile (e.g. global system for mobile communication (GSM)), global positioning system (GPS) and personal communication systems, due to the resistance of metallic oxide coating. To overcome this problem, an aperture-type bandpass FSS may be etched in the glass coating to selectively improve the transmission of useful signals. However, such an FSS also leads to an increase in overall IR transmission through energy-saving glass which is unwanted. In this study the authors analyse the effect of etching an FSS on the transmission of RF/MW, IR and light waves, for two types of commercial energy-saving glass panels. For example, an FSS with 8 mm aperture designed to improve MW transmission by 20 dB (from about -30 to -10 dB) at 1.3 GHz causes an increase in overall IR transmission from 23.8% to 33.8% (10%), which may be acceptable. An FSS with a narrower (4 mm) aperture improves MW transmission by 16 dB with 6.2% increase in IR transmission. Theoretical and measured results are presented

3-D Metamaterials: Trends on Applied Designs, Computational Methods and Fabrication Techniques

This work was funded in part by the Predoctoral Grant FPU18/01965 and in part by the financial support of BBVA Foundation through a project belonging to the 2021 Leonardo Grants for Researchers and Cultural Creators, BBVA Foundation. The BBVA Foundation accepts no responsibility for the opinions, statements, and contents included in the project and/or the results thereof, which are entirely the responsibility of the authors.Metamaterials are artificially engineered devices that go beyond the properties of conventional materials in nature. Metamaterials allow for the creation of negative refractive indexes; light trapping with epsilon-near-zero compounds; bandgap selection; superconductivity phenomena; non-Hermitian responses; and more generally, manipulation of the propagation of electromagnetic and acoustic waves. In the past, low computational resources and the lack of proper manufacturing techniques have limited attention towards 1-D and 2-D metamaterials. However, the true potential of metamaterials is ultimately reached in 3-D configurations, when the degrees of freedom associated with the propagating direction are fully exploited in design. This is expected to lead to a new era in the field of metamaterials, from which future high-speed and low-latency communication networks can benefit. Here, a comprehensive overview of the past, present, and future trends related to 3-D metamaterial devices is presented, focusing on efficient computational methods, innovative designs, and functional manufacturing techniques.Predoctoral Grant FPU18/01965BBVA Foundatio

3D FSS with multiple transmission zeros and pseudo elliptic response

The three-dimensional frequency selective surface (3D FSS) with band reject multiple transmission zeros and pseudo-elliptic response is designed from two-dimensional (2D) periodic array of shielded micro strip lines to realize wide out-of–band radio wave rejection. The 3D FSS array consists of multimode cavities whose coupling with air can be controlled to obtain a desired frequency range. The proposed FSS with shorting via to ground exhibits pseudo-elliptic band-reject response in the frequency range from 6GHz to 14GHz. As the plane wave of linear polarization incidents perpendicularly to the shielded micro strip line with perfect electric conductor (PEC) and perfect magnetic conductor (PMC) boundary walls, two quasi-TEM modes are obtained known as air mode and substrate mode. The first 3D FSS design is a combination of two or more resonators. Furthermore, second 3D FSS design with three shorting vias result more elliptic band reject frequency response and a pass band transmission pole. All in phase resonators of design give transmission poles and out of phase combination of resonators give transmission zeros respectively. The proposed 3D FSS is designed and simulated using Ansys HFSS software. These designs exhibit an improved performance for many practical applications such as antenna sub-reflector, and spatial filters

A review of manufacturing materials and production methods for frequency-selective structures [wireless corner]

This article presents a review of frequency-selective structure (FSS) manufacturing materials and production methods ranging from the common printed circuit board (PCB)-based designs to textile, ink, metal, or fluid prototypes. Our work gathers some of the most relevant solutions published by the scientific community and considers several examples depicted for each case. Additionally, the main physical parameters that may have a significant impact on FSS performance have been identified, e.g., electrical conductivity of the FSS conductive element and the relative permittivity and thickness of the FSS dielectric material. Finally, a comparative analysis of the materials and techniques is presented, which highlights the benefits and limitations of each solution.Fundação para a Ciência e a Tecnologia | Ref. POCI-01- 0247-FEDER- 017867Ministerio de Economía y Competitividad | Ref. TEC2014-55735-C03-

Design and realization for radar cross section reduction of patch antennas using shorted stubs metamaterial absorbers

This thesis is devoted to analyzing of the Radar Cross Section (RCS) of rectangular patch antenna using Metamaterial Absorber (MMA) and the analysis of its reducing techniques. The addressed theme has a great complexity and it covers various areas that include designing and optimization of target geometrical model of rectangular patch antenna structures and making it compatible with respect to metamaterial geometry. Analyses have been made to optimize and validate the structure performances that include numerical methods for electromagnetic field computation, MMA behavior, characterization, extraction of parameters, antenna radiation performance analyses, simulation, fabrication, testing, and optimization with back validating the designs. The MMA structure finds its applications in antenna designing for the reduction of Monostatic and Bistatic RCS in stealth platform for lower detectable objects. However, there is still more emphasis needed to devote for in-band frequency response for low RCS of the antenna. Therefore, making these assumptions, we have been proposing novel designs of single-band, dual-band, and triple-band MMA structures. These structures provide significant scattering characteristics and offering flexibility to the designer to control and tune the resonant frequency, based on the specific applications as compared to that of the other MMAs in the microwave regime of the Electromagnetic (EM) spectrum. To explore the research scope, a three dimensional Frequency Selective Surface (FSS) structure has been analyzed and its simulation responses with respect to parametric analyses have been made. The research investigation further extended to Electronic Band Gap (EBG) Structure and Defected Ground Structure (DGS). A hybrid structure of patch antenna is proposed and designed for an inset feed rectangular microstrip patch antenna operating at 2.45 GHz in the Industrial, Scientific, and Medical (ISM) band. This hybrid structure claims the size reduction, bandwidth, and gains enhancement. The main focus of this research work is limited to determine the potential and practical feasibility of MMA’s to enhance the stealth performance of rectangular patch antennas. For this purpose, Monostatic and Bistatic RCS simulation and measurements are carried out in an anechoic chamber and practical methods for Radar Cross Section reduction are discussed and analyzed

Inverse Design of Three-Dimensional Frequency Selective Structures and Metamaterials using Multi-Objective Lazy Ant Colony Optimization

With the rise of big data and the “internet of things,” wireless signals permeate today’s environment more than ever before. As the demand for information and security continues to expand, the need for filtering a crowded signal space will become increasingly important. Although existing devices can achieve this with additional components, such as in-line filters and low noise amplifiers, these approaches introduce additional bulk, cost and complexity. An alternative, low-cost solution to filtering these signals can be achieved through the use of Frequency Selective Surfaces (FSSs), which are commonly used in antennas, polarizers, radomes, and intelligent architecture. FSSs typically consist of a doubly-periodic array of unit cells, which acts as a spatial electromagnetic filter that selectively rejects or transmits electromagnetic waves, based on the unit cell’s geometry and material properties. Unlike traditional analog filters, spatial filters must also account for the polarization and incidence angle of signals; thus, an ideal FSS maintains a given frequency response for all polarizations and incidence angles. Traditional FSS designs have ranged from planar structures with canonical shapes to miniaturized and multi-layer designs using fractals and other space-filling geometries. More recently, FSS research has expanded into three-dimensional (3D) designs, which have demonstrated enhanced fields of view over traditional planar and multi-layer designs. To date, nearly all FSSs still suffer from significant shifts in resonant frequencies or onset of grating lobes at incidence angles beyond 60 degrees in one or more polarizations. Additionally, while recent advances in additive manufacturing techniques have made fully 3D FSS designs increasingly popular, design tools to exploit these fabrication methods to develop FSSs with ultra-wide Fields of View (FOV) do not currently exist. In this dissertation, a Multi-Objective Lazy Ant Colony Optimization (MOLACO) scheme will be introduced and applied to the problem of 3D FSS design for extreme FOVs. The versatility of this algorithm will further be demonstrated through application to the design of meander line antennas, optical antennas, and phase-gradient metasurfaces

A Case Study for Improving Performance of Frequency Selective Surface through Union of Sub-Sets and Particle Swarm Optimization

Frequency Selective Surfaces (FSSs) consist of a repetition of a given pattern in a periodic way; typically, a dielectric substrate supports this arrangement giving rise to a two-dimensional array. Although relatively simple in structure, designing an FSS that exhibits large bandwidth and stable response to oblique incidence is not straightforward and requires special attention and significant computational effort. To address this problem, this study presents a methodology whereby an initial configuration of the FSS pattern is subjected to an optimization method for sizing the geometrical parameters. Consequently, the initial unit cell is first broken down into subsections, specifically as a “union of subsets”, then particle swarm optimization is used to achieve optimal design parameters that further improves the overall FSS performances. To validate the proposed method, an X-band FSS is proposed and optimized in a commercial simulation environment (Microwave Studio, Dassault Systèmes)

A High Selectivity, Miniaturized, Low Profile Dual-Band Bandpass FSS with a Controllable Transmission Zero

A novel, highly selective, low profile dual-band, and bandpass miniaturized-element frequency selective surface is proposed to realize stable angular responses and a controllable transmission zero. This FSS is a three-layer structure consisting of three metal layers that are separated from each other by two dielectric substrates. The equivalent circuit model of the FSS and its operating principle are presented and analyzed based on the microwave filter theory. The prototype of this FSS is simulated, fabricated, and measured, and its theoretical analysis, simulation, and measurement results show a good agreement. This FSS has achieved an excellent angular stability and wide out-of-band rejection performance in the scope of incidence angle of 80 degrees. Compared with the other multilayered FSSs and 3D FSSs proposed in previous works, it possesses a lower profile as well as a smaller size. A transmission zero is produced by etching slots on the edges of the middle metal layer to achieve superior frequency selectivity. By properly choosing the size and direction of the slots, the transmission zero and the polarization selectivity are able to be changed, respectively