Carbon fiber wound hydrogen tanks are widely used in the field of new energy, but their complex multilayer structure makes it difficult to conduct nondestructive testing/structural health monitoring (NDT/SHM). In this paper, electromagnetic tomography (EMT) is used for noncontact in situ defect detection on a carbon fiber wound hydrogen tank. According to its structural characteristics, an open U-shaped sensor array that fits the curvature of the tank body is designed. To improve the quality of reconstructed images, an iterative image reconstruction algorithm based on a composite sensitivity matrix (CSM) is proposed. To verify the performance of the method, the method in this paper is compared with linear back projection (LBP), the Landweber iterative algorithm and the Tikhonov regularization algorithm, and the image quality is evaluated by comparing the image relative error and correlation coefficient. Both simulated and experimental results show that the method proposed in this paper is more accurate in defect localization and higher in quality than traditional image reconstruction algorithms.
A novel approach is presented to achieve improved sensing performance using a one-dimensional (1D) hyperbolic graded photonic crystal (PC). The graded structure achieves refractive index modulation that varies hyperbolically with layer depth, due to its graded index geometry. Porous materials are employed to facilitate analyte infiltration. The reflectivity and sensing performance of the proposed graded and non-graded geometry is evaluated using the transfer matrix method (TMM). The Sensing capability of the graded structure is evaluated analytically by infusing different analytes within the cavity, considering various cavity widths and incidence angles. At a 40-degree angle of incidence, the analytical results demonstrate that the suggested graded structure exhibits a maximum sensitivity of 469 nm/RIU, along with a detection limit and FOM of 9.1×10-3 and 125 RIU-1, respectively. The detailed electric field confinement of the graded geometry is also carried out at the interface. The proposed structure outperforms conventional non-graded structures with a 114% higher sensitivity. The bio-photonic design can easily be implemented and provides high performance compared to previous works that employ exponentially graded structures. The suggested biosensor can detect even minor fluctuations in the refractive index of blood serum samples with different cholesterol concentrations.
In this paper, we propose a noninvasive blood glucose monitoring system that can be easily integrated into smartwatches. This system makes use of dielectric properties of blood-flow in human blood vessels as well as frequency dependency of blood glucose. To prove the proposed design principle, authors have verified the system working with vector network analyser and a directional coupler. The entire system design is explained in this paper. At the time of final system integration, the vector network analyser and directional coupler can be replaced with other on-chip sensors. Authors have also compared the obtained results with finger pricking based blood-glucose measurement. The results agree and have been tabulated. Clarke error grid was also used to evaluate proposed system accuracy.
Terahertz era is becoming a more prominent and expanding platform for a variety of applications. In this paper, we propose a triband absorber with a hexagon-shaped radiating patch for THz applications. The proposed structure has three layers: a hexagonal patch made of graphene as a radiating patch, a silicon layer as a dielectric substrate, and a bottom conductive layer made of gold to prevent EM wave transmission. The proposed structure operates at three resonant frequencies 0.38 THz, 1.23 THz, and 1.77 THz respectively. We may accomplish maximum absorption level (above 90%) and maximum absorption bandwidth by setting relevant chemical potential and relaxation times to 0.2 ev and 0.2 ps respectively. The proposed structure contains a lossy silicon substrate, which has a dielectric constant of 11.9 and a loss tangent of 2.5e-004. The proposed structure reveals a larger absorption [above 90%] for the operating frequencies, and the effect on absorbance for different modes is illustrated.
Solid State Transformers (SSTs) are emerging as the major component of smart grid system. High Frequency Transformer (HFT) is the key element of SST. The optimum design of SST is a critical task due to the complex design of magnetic, electric and dielectric circuits of high frequency transformer and due to the design of power electronic circuits used at either sides of HFT. The most significant among above is the design of magnetic circuit and the possibility of using different magnetic materials for high frequency application. This paper discusses the performance analysis of HFT for different magnetic materials used for core construction. The magnetic materials considered in this analysis are amorphous, nanocrystalline and si-steel. Optimum HFT design is selected from a set of designs using an iterative algorithm, considering each core material separately. Validation of the design is done in Finite Element Method (FEM) analysis software. The design of a high frequency transformer, which is integrated in 1000 kVA 11 kV/415 V SST, is investigated both analytically and numerically, with optimum designs developed using three core materials.
In this work we show a novel method based on a local two-port interferometer to distinguish the topological charge of radio-vortices at 30 GHz by using a small portion of the entire wavefront only. The experimental investigation of the amplitude and phase properties of the interference pattern with a pure Gaussian beam (l = 0) and a l = 1 radio vortex is carried out, and results are compared with the theory based on Laguerre-Gauss modes. Experiments were performed both with the interferometer and with single antenna to highlight the effective benefits of the interferometric approach, sensitive to the azimuthal phase of the vortex field. Method is also extendable at higher topological charges for applications to high-density millimetric communications.
Prediction in the transition region between lit and shadowed regions is important for maintaining stable mobile communication for the beyond 5th generation. In this paper, as the difference between the reflection and diffraction from a dielectric circular cylinder and an absorber screen, respectively, a novel additional term is derived by a uniform theory of diffraction (UTD) in the lit side of the transition region. The proposed model is validated by the UTD and exact solutions of a dielectric circular cylinder. Through the proposal, we can separate the contribution of the shadowed Fresnel zone (FZ) number and boundary conditions (i.e., the surface impedance and the polarization) to the total field. The frequency characteristics of the shadowed FZ and boundary conditions are theoretically analyzed. The analyzed results show that the contributions of the boundary conditions are weaker than the shadowed FZ in the lit region at a high frequency.
Planar and conformal log periodic dipole array (LPDA) antennas are proposed in this paper with circular patch and hexagonal patch top loadings for multiband applications. Due to these top loadings, the size of the antennas is reduced, and the total dimensions of the two antennas are 44 mm x 40 mm. These antennas are fabricated on polyimide material with a dielectric constant of 3.3 and thickness of 0.1 mm. These two antennas resonate at 3.5 GHz, 5.7 GHz, 7.5 GHz and 9.3 GHz frequencies in both planar and conformal modes. The antenna characteristics of the proposed antenna models such as reflection coefficient, VSWR, radiation pattern, and gain are analyzed, and the measured results are in good agreement with simulation ones.
In this study, a compact, reconfigurable, and high-efficiency Long Range (LoRa) patch antenna, which is novel, is presented for Internet of Things (IoT) applications. The antenna is designed to operate at the three major frequencies used for LoRa communication, namely 915 MHz, 868 MHz, and 433 MHz, which are widely employed for global LoRa connectivity. The compact size and impedance matching of the antenna are achieved through the use of meandered radiating patches, a partial ground plane, and a ground plane stub. The antenna is prototyped on a commercially available and cost-effective FR-4 material and measures 80 mm x 50 mm x 1.6 mm (0.12λ x 0.07λ at the lowest resonant frequency), which is smaller than the size of a standard credit card. The antenna utilizes three RF PIN diodes (SW1, SW2, and SW3) for frequency reconfiguration, which are characterized by low insertion loss and fast switching time. The RLC equivalent circuit of the antenna was validated through simulations and measurements, yielding the peak gain and radiation efficiency of 2.1 dBi and >90%, respectively. These results prove that the antenna is a promising solution for LoRa IoT applications in terms of size, cost, and performance, filling a gap in the existing literature of LoRa MPAs that are typically large, non-reconfigurable, low-gain, and single-band.
In this paper, a 24-element microstrip antenna array with three-dimensional near-field pattern shaping capability for microwave hyperthermia is presented. The antenna array operating at 2.45 GHz is designed based on the weighted constrained method of the maximum power transmission efficiency (WCMMPTE). By setting proper constraints for the electric field distribution of several selected points within the target area, the three-dimensional (3D) shape of the electric field can be characterized, meanwhile ensuring that the power is maximally concentrated in this area. Moreover, the shape, size, and spatial location of the three-dimensional area are all adjustable according to the selection of those specific points, making the array quickly adaptable for different actual requirements. The electric field distribution of the preset 3D shape can be focused at center or off-center with optimized excitations fed into the array. The measured electric field distribution shows that the transmitting array antenna is able to achieve a preset 3D shape of the electric field distribution as well as a preset offset position in the desired direction, agreeing very well with the simulations.
An elliptical shape multi-band microstrip patch antenna with narrow semicircle cuts and bulges on two horizontal ends is proposed for Global Positioning System (GPS), Indian Regional Navigation Satellite System (IRNSS), Sub-6 GHz 5G and Wireless Local-Area Network (WLAN) wireless communication applications. The proposed antenna operates at 1.56 GHz, 2.49 GHz, 3.5 GHz, and 5.24 GHz for desired applications, respectively. The proposed antenna, fed by coaxial feeding mounted on Rogers AD255C substrate, has optimized physical dimensions of 80×80×3.175 mm3. The semicircle cuts and bulges on horizontal ends on the elliptical element contribute to exciting higher-order modes and affect the current distribution at the resonant frequencies resulting in producing multi-band operations. The antenna is fabricated and tested. The measured return loss characteristic (S11) below -10 dB is -14.58 dB, -18.80 dB, -22.25 dB, & -27.03 dB, with the radiation efficiency of 58.7%, 94.8%, 93.2%, & 84.9% and peak gain of 3.49 dBi, 6.49 dBi, 4.93 dBi & 4.36 dBi for desired application band, respectively. The proposed antenna also offers impedance bandwidths of 40 MHz (1.55-1.59 GHz), 90 MHz (2.43-2.52 GHz), 100 MHz (3.44-3.54 GHz) & 90 MHz (5.23-5.32 GHz) at resonant frequencies and relatively stable radiation patterns. Simulated and measured results for the proposed antenna exhibit good agreement. The proposed multi-band antenna offers a simple design and improved performance.
The paper addresses a bioinspired printed antenna in the shape of a `Lotus' which is further loaded with a new type of Frequency Selective Surface (FSS) structure with unit cell dimension as 0.16λ0×0.16λ0×0.033λ0, where λ0 is the lowest operating wavelength. The two dissimilar layers of FSS, which are separated by an air gap of about 3.2 mm, have been placed below the antenna. The combined structure operates over 3.8 GHz to 14.4 GHz (116.5% measured) with peak realized gain of 7.5 dBi. The introduction of the FSS layer provides gain enhancement of about 5.9 dBi. The standalone FSS geometry provides a wide transmission bandwidth from 5.5 to 12.5 GHz along with good angular stability of about 50º. The Gielissuper formula has been used to develop the petal of the lotus shaped antenna. The time domain analysis of the lotus shaped antenna has also been provided. The proposed structure can be used as an electromagnetic sensor for wide band applications over C, X and partially Ku bands.
In the dynamic wireless charging system of electric vehicles, the misalignment between transmitting and receiving coils will cause drastic changes in the coupling coefficient, which will lead to system instability. A dynamic and static wireless power transfer system superimposed dislocation coil (SDC) structure is proposed in this paper. This structure ensures a constant coupling coefficient between the transmitting and receiving coils of the dynamic and static wireless power transfer system for electric vehicles. Firstly, the variation law of the coupling coefficient of the SDC structure is analyzed. Secondly, a quasi-constant coupling coefficient optimization method is proposed based on the SDC structure to obtain the coil parameters that meet the requirements. Finally, according to the optimization results, an experimental platform for wireless power transfer based on the SDC structure is built. The experimental results show that the maximum fluctuation rate of the inter-coil coupling coefficient is only 3.12% when the misalignment between the transmitting coil and the receiving coil is within half of the outer length of the transmitting coil. Thus, the correctness and effectiveness of the proposed structure and method are verified.
A high-sensitivity photonic crystal fiber (PCF) Temperature sensor based on surface plasmon resonance (SPR) with a high figure of merit (FOM) is proposed. Compared with most optical fiber inner air holes coated with metal or placed with metal nanowires, owing to the plasma material directly contacting the analyte, the annular channel outside the cladding is convenient for analyte detection, and the sensor is easier to manufacture. The temperature-sensitive liquid is a mixed solution of ethanol and chloroform with a volume ratio of 1:1. The results indicate that the highest sensitivity of this sensor can reach 15.4 nm/˚C, and the maximum FOM is 0.2829/˚C between -10˚C and 60˚C. Furthermore, the influence of photonic crystal fiber air hole size, gold film thickness, and other parameters on the performance of the sensor is analyzed.
A polarization reconfigurable dielectric resonator Antenna (DRA) is proposed for X-band applications. The antenna provides circularly polarized (CP) or linearly polarized (LP) radiations at the same frequency band. Altering the states of two PIN diode switches offers a choice of one of three polarization options: (i) LP radiation; (ii) left-hand CP (LHCP) radiation; (iii) right-hand CP (RHCP) radiation. The simulations and measurements are in close agreement, indicating that the LHCP and RHCP radiations have reconfigurable polarization traits with a 21.3% impedance bandwidth ranging from 9.6 to 11.9 GHz and a 3.4% for the LP radiation that extends from 10.2 to 10.5 GHz. There is simultaneously a maximum gain of 6.9 dBic with a circa 4% axial ratio (AR) bandwidth for the LHCP and RHCP radiations.