This work presents the design and analysis of a metal-insulator-metal (MIM)-based optical log spiral rectenna for efficient energy harvesting at 28.3 THz. To maximize the benefits of the enhanced ...field of the proposed nano-antenna in the rectification process, the proposed design considers the antenna arms (Au) as the electrodes of the rectifying diode and the insulator is placed between the electrode terminals for the compact design of the horizontal MIM rectenna. The rectifier insulator, Al
O
, was inserted at the hotspot located in the gap between the antennas. A detailed analysis of the effect of different symmetric and asymmetric MIM-configurations (Au-Al
O
-Ag, Au-Al
O
-Al, Au-Al
O
-Cr, Au-Al
O
-Cu, and Au-Al
O
-Ti) was conducted. The results of the study suggested that the asymmetric configuration of Au-Al
O
-Ag provides optimal results. The proposed design benefits from the captured E-field intensity, I-V, resistivity, and responsivity and results in a rectenna that performs efficiently.
Traditional waste management system operates based on daily schedule which is highly inefficient and costly. The existing recycle bin has also proved its ineffectiveness in the public as people do ...not recycle their waste properly. With the development of Internet of Things (IoT) and Artificial Intelligence (AI), the traditional waste management system can be replaced with smart sensors embedded into the system to perform real time monitoring and allow for better waste management. The aim of this research is to develop a smart waste management system using LoRa communication protocol and TensorFlow based deep learning model. LoRa sends the sensor data and Tensorflow performs real time object detection and classification. The bin consists of several compartments to segregate the waste including metal, plastic, paper, and general waste compartment which are controlled by the servo motors. Object detection and waste classification is done in TensorFlow framework with pre-trained object detection model. This object detection model is trained with images of waste to generate a frozen inference graph used for object detection which is done through a camera connected to the Raspberry Pi 3 Model B+ as the main processing unit. Ultrasonic sensor is embedded into each waste compartment to monitor the filling level of the waste. GPS module is integrated to monitor the location and real time of the bin. LoRa communication protocol is used to transmit data about the location, real time and filling level of the bin. RFID module is embedded for the purpose of waste management personnel identification.
The thermal performance enhancement of a vertical helical coil heat exchanger using distilled water-based copper oxide-graphene hybrid nanofluid has been analyzed experimentally. Accordingly, the ...focus of this study is the preparation of CuO-Gp (80-20%) hybrid nanoparticles-based suspensions with various mass fractions (0% ≤ wt ≤ 1%). The volume flow rate is ranged from 0.5 L·min−1 to 1.5 L·min−1 to keep the laminar flow regime (768 ≤ Re ≤ 1843) and the supplied hot fluid’s temperature was chosen to equal 50 °C. To ensure the dispersion and avoid agglomeration an ultrasound sonicator is used and the thermal conductivity is evaluated via KD2 Pro Thermal Properties Analyzer. It has been found that the increment in nanoparticles mass fraction enhances considerably the thermal conductivity and the thermal energy exchange rate. In fact, an enhancement of 23.65% in the heat transfer coefficient is obtained with wt = 0.2%, while it is as high as 79.68% for wt = 1%. Moreover, increasing Reynolds number results in a considerable augmentation of the heat transfer coefficient.
A 32-bit chipless RFID tag operating in the 4.5-10.9 GHz band is presented in this paper. The tag has a unique multiple-arc-type shape consisting of closely packed 0.2 mm wide arcs of different radii ...and lengths. The specific tag geometry provides multiple resonances in frequency domain of an RCS plot. A frequency domain coding technique has also been proposed to encode the tag's RCS signature into a 32-bit digital identification code. The tag has an overall dimension of 17.9 × 17.9 mm
, resulting in a high code density of 9.98 bits/cm
and spectral efficiency of 5 bits/GHz. The proposed tag is built on a low loss substrate bearing a very small footprint, thereby making it extremely suitable for large-scale product identification purposes in future chipless RFID tag systems.
This work presents a novel technique for designing chipless radio frequency identification (RFID) tags which, unlike the traditional tags with complex geometries, are both compact and printable. The ...tags themselves are alphabets, which offers the advantage of efficient visual recognition of the transmitted data in real-time via radio frequency (RF) waves. In this study, the alphabets (e.g., a, b and c) are realized by using copper etching on a thin dielectric substrate (TLX-8) backed by a ground plane. It is shown that the original signature of the frequency response of the backscattered radar cross-section (RCS) of the letter, displays dips that are unique to the individual letters. The tags have been simulated, fabricated and their monostatic cross-sections have been measured by using a dual-polarized Vivaldi antenna in the frequency band ranging from 6 to 13 GHz. The study also includes, for the first time, a detailed analysis of the impact of changing the shape of the tag owing to variation in the font type, size, spacing, and orientation. The proposed letters of the alphabet are easily printable on the tag and provide an efficient way to visually recognized them and, hence, to detect them in a robust way, even with a low coding density of 2.63 bit/cm2. The advantages of the proposed novel identification method, i.e., utilization of the both co- and cross-polar RCS characteristics for the printable clipless RFID tags are the enhancement of the coding density, security and better detection of the alphabet tags with different fonts by capturing the tag characteristics with better signal to noise ratio (SNR). Good agreement has been achieved between the measured and simulated results for both co- and cross-polarized cases.
•Three-layer metamaterial absorber with sandwiched metal-dielectric-metal structure.•Good impedance match with plasmonic resonance characteristics.•96.77% average absorption with a peak of 99.99% ...absorption for optical spectrum.•Useful for various optical wavelength applications.
Optical wavelengths considered as the key source of electromagnetic waves from the sun, and metamaterial absorber (MMA) enables various applications for this region like real invisible cloaks, color imaging, magnetic resonance imaging, light trapping, plasmonic sensor, light detector, and thermal imaging applications. Contemplated those applications, a new wide-angle, polarization-insensitive MMA is presented in this study. The absorber was formatted with three layers that consisted of a sandwiched metal-dielectric-metal structure. This formation of metamaterial absorber showed a good impedance match with plasmonic resonance characteristics. The structure was simulated using the FIT and validated with the FEM. A variety of parametric studies were performed with the design to gain best physical dimension. The mechanism of absorption also explained immensely by various significant analysis. The design had average 96.77% absorption from wavelengths of 389.34 nm to 697.19 nm and a near-perfect absorption of 99.99% at a wavelength of 545.73 nm for TEM mode. For an ultra-wide bandwidth of 102 nm, the design exhibited above 99% absorbance. The proposed is wide-angle independent up to 60° for both TE and TM mode, which is useful for solar energy harvesting, solar cell, and solar thermophotovoltaics (STPV). This MMA can be used for an optical sensor or as a light detector. Moreover, this proposed design can be employed in some applications mentioned above.
This study proposed, for the first time, a newly developed metal–insulator-insulator–metal (MIIM)-based log-spiral rectenna for energy harvesting applications. The designed resonant log-spiral ...antenna at 28.3 THz forwards the absorbed infrared (IR) electromagnetic (EM) radiations to the installed double insulator-based MIIM rectifying diode. The realized MIIM diode is formed by sandwiching the two insulators among the designed resonant antenna terminals (hot spot region). Antenna terminals are used as the electrodes of the rectifying diode. This novel approach ensures the maximum transfer of captured IR EM radiations by the antenna to the rectifying part with good impedance matching and thus increases the overall conversions efficiency. The study presents an in-depth analysis of the impact of the changing metal types (Au, Al, Ag, and Cu) and insulating materials (Al2O3, Cu2O, Ta2O5, TiO2, and ZnO with10 different formations) on the realized rectenna performance in terms of captured E-field enhancement, I/V, resistivity, and responsivity characteristics. It is found that the overall performance of the proposed double insulator-based rectenna system is better for the asymmetric configuration of Au- Al2O3- Cu2O –Cu and it exhibits 100% enhanced non-linearity as compared to MIM-based configuration.
In this paper, a polarization-independent perfect absorber with near-zero index metamaterial (NZIM) property is proposed. Conventional FR4 substrate without any lumped or substrate-embedded elements ...has been used with a unique patch of the swastika-shaped capacitive gap along with inductive tails at 90-degree rotational symmetry. The simulation results for both the unit cell and the array for co-polarized waves at normal and oblique incidences up to 90° has shown near unity absorptions at 4.238, 7.836, 10.482, 11.014 and 13.352 GHz along with near zero values of permittivity, permeability, and refractive index. The cross-polarization analysis has proved its perfect absorption capability. The absorber has shown 14 GHz of near-zero refractive index at the entire operating frequency range. The equivalent circuit analysis and measurement of both the array and the unit cell were in good agreement with simulation results, which proved it as a perfect NZIM absorber to enhance antenna gain and directivity and other sensing applications at C, X and Ku band.
A novel approach for infrared (IR) energy harvesting through the integration of a resonating metasurface with a metal-insulator-metal (MIM) nano-rectenna is presented. The absorption of IR radiation ...at 28.3 THz is significantly enhanced through the localization of surface plasmons with the integration of a periodic metasurface on the top of the log spiral MIM rectenna. Additionally, a ground plane is introduced on the backside of the structure to further enhance absorption characteristics. Extensive characterization analysis of the antenna's absorbed E-fields for incident 28.3 THz radiation is conducted with and without the integrated metasurface using full-wave numerical simulation. Also, the rectification properties (I/V, resistivity, and responsivity) are studied with variations in metal (Au, Al, Ag, and Cu) and five different insulators (Al2O3, Cu2O, Ta2O5, TiO2, and ZnO) types. The results demonstrate that the presence of the metasurface enhances the absorbed IR E-field by the rectenna to levels of 80–90%. Furthermore, exceptional harvesting performance, including E-field, current density, resistivity, and rectification efficiency (responsivity), is achieved with the asymmetric Au-ZnO-Cu and Au-ZnO-Ag MIM and metasurface rectenna structures. The proposed design strategies can lead to the development of highly efficient IR energy harvesters in the future.
This article presents printed log periodic antennas with metamaterials for use in microwave imaging. A single layer of epsilon negative (ENG) metamaterial (MTM) array (1 × 6) of the unit cell is on ...the radiating patch. Adding a single negative metamaterial structure enhances the properties of far-field antennas, such as radiation pattern and gain, both of which are vital for breast imaging. Two frequency bands exhibit negative permittivity: 3–3.3 GHz and 3.6–4.5 GHz. In the operating band, the proposed antennas have achieved a maximum gain of 5.5 dBi and impedance bandwidth of 3 GHz (2–5 GHz) with a reflection coefficient less than −10 dB. At the lowest operating frequency of 2 GHz, the electrical dimensions of this designed antenna are 0.34λ × 0.26λ × 0.01λ. All 16 transceiver antennas are arranged vertically in a circular pattern around the phantom, each acting as a transmitter and the rest as receivers. The system design is carried out with the electromagnetic simulators CST and HFSS. After receiving the extracted data, the data are postprocessed using the MATLAB software and the delay multiply and sum (DMAS) imaging algorithm. Based on the reconstructed image, it is evident that the MTM-loaded antenna-based imaging system can detect many undesired tumors inside the breast phantom.
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