3D-printed flat lens for microwave applications

This paper presents the design of a 3D-printed flat graded-index lens based on ray optics. The lens is comprised of several concentric dielectric rings with bespoke relative permittivities for transforming spherical waves into plane waves. 3D-printing was used to fabricate this lens with graded and tailored dielectric properties in a single process. The 3D-printed flat lens is low-cost and light-weight, but provides broadband and high gain performance. Measurement results show that the realised gain of the lens is 8 to 10 dB over the frequency band ranging from 12 to 18 GHz

3D-printed flat lens for microwave applications

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4G antennas for wireless eyewear devices and related SAR

This article was published in Comptes Rendus Physique [© Elsevier France] and the definitive version is available at: http://dx.doi.org/10.1016/j.crhy.2015.10.009In this paper, we first present a feasibility study to design 4G antennas (700–960 MHz and 1.7–2.7 GHz) for eyewear devices. Those eyewear devices should be connected to the last generation cellular networks, Wireless Local Area Networks or wireless hotspots. Three coupling element type antennas with their matching networks are evaluated in terms of reflection coefficient and total radiation efficiency when the eyewear is placed on the user's head. We also present Specific Absorption Rate (SAR) simulations when the eyewear is positioned over a homogeneous SAM phantom and over a heterogeneous VH (Visible Human) phantom: the SAR levels are compared to international limit values. In a second step, we present experimental results obtained with 3D printed eyewear and coupling elements etched on a classical PCB substrate where the matching circuits are optimized close to the feeding point of the coupling element. Simulated and measured values are in very good agreement: 7 to 16% and 9 to 35% total efficiency are respectively obtained for the low- and high-frequency bands. However, simulated SAR values are somewhat higher than authorized levels with preoccupant high electromagnetic field distribution close to the eye of the user

Thermal Spray Coatings for Electromagnetic Wave Absorption and Interference Shielding: A Review and Future Challenges

This review paper aims to consolidate scattered literature on thermally sprayed coatings with non-ionising electromagnetic (EM) wave absorption and shielding over specific wavelengths potentially useful in diverse applications (e.g., microwave to millimeter wave, solar selective, photocatalytic, interference shielding, thermal barrier-heat/emissivity). Materials EM properties such as electric permittivity, magnetic permeability, electrical conductivity, and dielectric loss are critical due to which a material can respond to absorbed, reflected, transmitted, or may excite surface electromagnetic waves at frequencies typical of electromagnetic radiations. Thermal spraying is a standard industrial practice used for depositing coatings where the sprayed layer is formed by successive impact of fully or partially molten droplets/particles of a material (used in the form of powder or wire) exposed to high or moderate temperatures and velocities. However, as an emerging novel application of an existing thermal spray techniques, some special considerations are warranted for targeted development involving relevant characterisation. Key potential research areas of development relating to material selection and coating fabrication strategies and their impact on existing practices in the field are identified. The study shows a research gap in the feedstock materials design and doping (including hollow and yolk-shelled structure types) and their complex selection covered by thermally sprayed coatings that can be critical to advancing applications exploiting their electromagnetic properties

Thermal Spray Coatings for Electromagnetic Wave Absorption and Interference Shielding: A Review and Future Challenges

This review paper aims to consolidate scattered literature on thermally sprayed coatings with non-ionising electromagnetic (EM) wave absorption and shielding over specific wavelengths potentially useful in diverse applications (e.g., microwave to millimeter wave, solar selective, photocatalytic, interference shielding, thermal barrier-heat/emissivity). Materials EM properties such as electric permittivity, magnetic permeability, electrical conductivity, and dielectric loss are critical due to which a material can respond to absorbed, reflected, transmitted, or may excite surface electromagnetic waves at frequencies typical of electromagnetic radiations. Thermal spraying is a standard industrial practice used for depositing coatings where the sprayed layer is formed by successive impact of fully or partially molten droplets/particles of a material (used in the form of powder or wire) exposed to high or moderate temperatures and velocities. However, as an emerging novel application of an existing thermal spray techniques, some special considerations are warranted for targeted development involving relevant characterisation. Key potential research areas of development relating to material selection and coating fabrication strategies and their impact on existing practices in the field are identified. The study shows a research gap in the feedstock materials design and doping (including hollow and yolk-shelled structure types) and their complex selection covered by thermally sprayed coatings that can be critical to advancing applications exploiting their electromagnetic properties

Microstrip Patch Antennas with Anisotropic and Diamagnetic Synthetic Heterogeneous Substrates - Data Set

Figure showing frequency response for patch on heterogeneous material with metallic inclusions in different orientations

Microstrip Patch Antennas with Anisotropic and Diamagnetic Synthetic Heterogeneous Substrates - Data Set

Figure showing frequency response for patch on heterogeneous material with metallic inclusions in different orientations

Design of Novel Fully Metallic mm-wave Reflectarray Antenna

The design of a novel fully metallic reflectarray antenna at millimetre-wave frequencies is presented. The reflectarray consists of 3-D metallic unit cells resembling four layers of thick metallic patches connected by metallic vias. Full phase control and low losses are achieved by generating numerous unit cells with different combinations of the patches' size. Simulations have been carried out using CST Microwave Studio and TICRA QUPES to evaluate the response of the unit cells and the proposed reflectarray. The unconventional multilayer design suggested can be implemented by exploiting recently emerged additive manufacturing techniques. In terms of the reflectarray performance, the operating frequency is centered at 30GHz whilst the directivity is approximately 28dBi

3D-Printed Lens Antenna

In this work, we present a flat lens design using the Dial-A-Dielectric (DaD) approach to realize permittivities that are not available off-The-shelf. To show the efficacy of this design, we present comparison results with legacy design. We compare results of a flat lens using commercial off-The-shelf (COTS) materials combined with 3-D fabrication material. In contrast with the Transformation Optics approach, the present design does not employ metamaterials (MTMs) that can be narrowband and lossy

3D-Printed Planar Graded Index Lenses

The authors introduce two flat graded-index (GRIN) lens designs in this study. First of these is a thick lens, which was designed and fabricated by using the three-dimensional (3D)-printing technique. Second, a thin dial-a-dielectric (DaD) lens, which uses state-of-the-art artificially engineered dielectric materials for design and for which they present only the simulated results, with plans to fabricate it in the future. Both designs overcome the difficulties faced in finding desired commercial off-the-shelf materials, either for 3D-printing or for fabricating conventional GRIN lenses. The lenses comprise of several concentric dielectric rings with bespoke relative permittivities for transforming spherical waves into plane waves and vice versa. The 3D-printed thick flat lens is low-cost and light-weight, but provides broadband and high gain performance. Measurement results show that the realised gain of the thick lens is 9-11 dB over the frequency band of 12-18 GHz. The designed DaD lens has the desirable characteristics of low loss, low reflection and broadband properties