Abstract- A tri-band, compact, flexible, and wearable antenna is simulated, numerically analyzed, and fabricated for on-body wireless body area network (WBAN) communication applications. The flexible design of the antenna is capable of operating at three different frequencies 2.45 GHz for the Industrial Scientific Medical band (ISM), 3.5 GHz for WiMAX, and 5.2 GHz for Wireless Local Area Network. The overall design dimensions are 2618×0.543mm3; the proposed antenna design is a combination of inverted C-shaped patches, a defective ground plane, and a microstrip feed line. The antenna layout is developed in CST Microwave Studio and then fabricated on polymer-based substrate Roger 5880. The antenna's maximum gain, 2.34 dBi, is attained at 5.2 GHz, while its minimum gain, 1.2 dBi, is seen at 2.45 GHz. When the antenna is working at 2.45 GHz, the maximum radiation efficiency is around 79.25 %. Additionally, bending analysis of design is numerically evaluated along x- and y-axes at three distinct radii of 20, 40, and 60 mm, respectively. The antenna is also tested on a human phantom model to predict on-body exploration of the specific absorption rate (SAR). All experimental and simulation results regarding this antenna are suitable for body-worn emerging applications.
Most real-life practical applications continuously use color filters, such as holography, sensing, multicolor displays, imaging, and information encoding, etc. Conventional dye-based transparent color filters face performance degradation due to environmental threats and ultraviolet radiation. The fabrication of nanostructures, meta-devices, and absorbers is getting fast due to well-established and enhanced nanotechnology fabrication techniques. This technological advancement leads toward metamaterial-based polarization-insensitive and sensitive light filtration, which has gained incredible popularity due to its increasing color filtering applications. Here we proposed a chromium (Cr) nano-cylinders-based metabsorber for color filtering in the visible spectrum. The proposed metabsorber comprises nine cylindrical bars with a transparent silicon wafer as a substrate and 50 nm thick chromium metal as a ground plane. The total size of the metabsorber is 200 × 200 nm2, whereas each cylindrical bar is 40 nm and 60 nm in diameter and height, respectively. Under simulation analysis, the proposed metabsorber depicts almost unity absorption in the visible spectrum for incident electromagnetic waves. In addition, metabsorber have passive-tunability features; specifically, it's absorption varies as the thickness of the substrate changes. Moreover, the metabsorber maintained its high absorption characteristics under large oblique incident angles (≤ 60o). Hence, relaxed angle tolerance, polarization-insensitivity, and passive-tunability features make the proposed metabsorber an excellent candidate for color filtering in miniaturized imaging/display devices.
KEYWORDS: Near field, Holography, Holograms, Near field optics, Refractive index, Optical design, Gallium, Optical components, Wave propagation, Radio propagation
Multi-functional metasurfaces have gained broad attention recently, as they bring great possibilities for high-dense multi-functional meta-devices, such as projecting holograms and displaying continuous gray-scale images simultaneously. However, currently reported metasurfaces to perform these operations separately. Furthermore, their complex multilayer and super-cell design strategies complicate both design and fabrication processes. This applies a limit on miniaturized, low-cost, integrated multi-functional meta-optics. Here we report a novel single-unit cell-based design strategy to demonstrate a tri-functional metasurface. By merging the spin-decoupling strategy with Mull’s law amplitude manipulation, a three-in-one metasurface is designed to project two independent holographic images in the far field and one continuous gray-scale image in the near-field of the metasurface. Specifically, far-field holographic images are projected on orthogonal helicities of white CP light, whereas a near-field image is decoded by creating an orthogonally linearly polarized light path. Furthermore, we optimized a novel gallium phosphide (GaP) material to verify the proposed design strategy for a tri-channel metasurface. The proposed metasurface has high transmission efficiency in the visible regime and verified our design strategy without adding extra complexities to conventional nano-pillar geometry. Therefore, our metasurface opens new avenues in multi-functional meta-device designing and has promising applications in anti-counterfeiting, optical storage, image displays, etc.
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