An advanced 2D mode theory of plane electromagnetic wave diffraction by a transmission dielectric grating (rectangular relief or planar sinusoidal one) is considered. On the bases of this theory, a new model of diffraction of a spatially inhomogeneous light field (a Gaussian beam) by a transmission grating with arbitrary thickness is developed. It provides the opportunity to compute the transverse spatial structure of radiation diffraction orders and to estimate character of their distortions in comparison with the initial Gaussian beam structure. It is shown that such distortions appear under abrupt variations of intensity of all orders and can be caused by transformation of a certain diffraction order from the radiation regime of propagation into the waveguide regime and inversely (Wood's anomalies), and also it can be induced by a set of additional reflections on the boundaries of a thick substrate.
In this paper, a patch antenna (PA) and its self-complementary structure, slot antenna (SA) are proposed and designed for directly matching the impedance of a rectifierat 2.45 GHz resonance frequency. The structures of these antennas comprise three sections, meandered-line, spiral, and a double-folded geometries, which make their geometrical parameters to be varied in easy manner according to design equations. In order to enhance both the desired level of a complex reflection coefficient of antenna at given resonance frequencies and the specified lower and higher frequencies constituting the impedance frequency bands, a new fitness function is presented. This fitness function is applied in designing broadband or multiband antennas having approximately perfect conjugate impedance matching with the impedance of a rectifier suitably used for RF Energy Harvesting (RF EH) application. An optimization design methodology based on two programs operating in synchronous manner, the particle swarm optimization (PSO) implemented in MATLAB simulation tool anda CST MWS Electromagnetic (EM) solver, is applied to the designed PA as an illustrative example. The simulation results reveal that our design methodology is helpful to obtain an optimized PA (OPA) having good impedance matching at the desired resonance frequency along with appropriate band. Measured result of the fabricated prototype is in good agreement with the simulated ones. Moreover, acceptable features such as small size, omnidirectional radiation, and broadband operation satisfy the (2.4-2.5 GHz) WLAN band, which strongly makesthe OPA a good candidate for RF EH applications.
This article proposes a new type of variable-leakage-flux flux-intensifying permanent magnet (VLF-FIPM) machine and performs optimization and multi-physical field analysis on it. By designing leakage flux bypass and various magnetic barriers, the proposed machine has the variable-leakage-flux characteristic and reverse saliency characteristic of Ld>Lq. Firstly, the evolution process from the conventional interior permanent magnet (IPM) machine to the proposed machine is explained. Secondly, the output torque, torque ripple, core loss and reverse saliency ratio of the proposed machine are optimized by multi-objective comprehensive optimization method. Then the electromagnetic performance of the optimal machine is compared with that of the initial machine and conventional IPM machine. Finally, the temperature field and stress field of the optimal machine in different states are analyzed in detail. Both theoretical results and simulation analysis verify the effectiveness of the proposed design idea and optimization of the VLF-FIPM machine.
In this work, we give a theoretical demonstration of the possibility to realize a photonic demultiplexer. The demultiplexer consists of Y-shaped waveguides with one input line and two output lines. We consider a demultiplexer composed of a segment and two asymmetric resonators, grafted at the same position in each channel. This system creates the resonance modes that have a maximum transmission rate and low Q quality factors. To improve these results, we take each output line consisting of a periodicity of segments and grafted at its extremities by a single resonator. Such a system creates passbands separated by band gaps. On the other hand, the presence of a resonator defect in the middle of each output line allows us to create defect modes inside the gaps. The results show that our proposed demultiplexer system manages to separate two incoming mixed signals of frequencies f1 = 204.75 MHz and f2 = 208.75 MHz and guide each one of them into two different channels.
The resonant frequency will be changed, and the load voltage will be unstable with misalignments and load variations in wireless power transfer (WPT) systems. In this paper, the expression for solving the resonant frequency is obtained. The calculation result shows that the resonant frequency is changed with the changes of misalignment and load. First, a new control method of frequency tracking with a Fuzzy proportional-integral (PI) compound controller is proposed, which can eliminate the overshoot of resonant frequency and improve the speed of frequency tracking. Second, a mixed-modulation method for adjusting frequency and voltage is further proposed, which is mainly composed of the selection algorithm of the duty cycle, the phase-shifting angle calculation, and the method of frequency tracking based on the Fuzzy PI compound controller. The appropriate duty cycle is obtained by the selection algorithm of the duty cycle to adjust the load voltage. The phase-shifting angles of different duty cycles are obtained by the phase-shifting angle calculation, which play a role in adjusting the resonant frequency by combining the Fuzzy PI compound controller. The proposed method can not only make the system keep a resonant state, but also make the output voltage across the load stable. A WPT system via magnetically coupled resonance is designed. Calculation and simulation results validating the superiority of the proposed method are given.
This paper proposes an orthogonal dual-feed microstrip patch antenna (MPA) that achieves multi-band resonance along with circular polarization at its primary band of 5G cellular communication. The proposed antenna is simpler than other designs to fulfill extreme data rates and minimum infrastructure requirements. This MPA is designed by taking most care for maintaining the isolation between ports with feasibility for physical fabrication. The HFSS based optimally designed proposed MPA resonates simultaneously at 3.48 GHz (3.3 GHz-3.7 GHz) band, 6.24 GHz (5.925 GHz-6.425 GHz) band, and 7.5 GHz (7.11 GHz-7.9 GHz) bands. The modes achieved for these three bands are TM01, TM11, and TM12 for 3.48 GHz, 6.24 GHz, and 7.5 GHz, respectively. The bandwidths achieved for the bands mentioned above are 160 MHz (4.57%), 330 MHz (5.27%), and 340 MHz (4.53%), respectively. The corresponding gains achieved are 9.8 dB, 5.06 dB, and 7.58 dB. The proposed MPA structure prototype is fabricated, and its performances are measured. The measured S11 for fabricated MPA is close to the resonating frequency found using HFSS simulation. The proposed MPA structure is also modeled and simulated in a MATLAB simulation environment. Performance parameters of the proposed MPA obtained in MATLAB and HFSS are compared and matched reasonably. The proposed MPA structure and its arrays are used for 5G cellular sites as a real-time application in a MATLAB simulation environment. Different test scenarios are created in MATLAB. SINR is visualized for the entire cellular area, and signal strengths are also fetched at the receiver sites.
This paper mainly deals with the channel diversity and the effect of spatial consistency parameters for different millimeter wave (mmWave) bands (28, 38 and 73 GHz) according to the channel parameters of the NYUSIM model. Statistical analyses are performed for various spatial consistency scenarios in an urban microcell (UMi) environment. Most of the recent analyses ignored the effect of adjusting the spatial consistency parameters on the 5G mmWave channel characteristics, including path loss (PL), received power, and path loss exponent (PLE). As a result, we have analyzed the effect of each parameter mentioned above for both directional power delay profile (DPDP) and omnidirectional power delay profile (OPDP). Numerical results illustrate how the characteristics of mmWave channels communication can be affected by changing the spatial consistency parameters.
This paper explores the effects of extended exposure to salt water fog on the microwave absorption properties of unidirectional carbon-fiber reinforced polymer (CFRP) circuit analog absorbers (CAA). Single-layer CFRP CAAs were fabricated using a wet-layup technique and were then subjected to a controlled salt water fog chamber following B117 standards. A total of ten samples using 305 g/m2 areal-weight unidirectional CFRP were fabricated. Three samples were withdrawn from the salt water environment at ten-day intervals and tested, with the final samples being withdrawn after 30 days. The mass of each sample was measured immediately after removal to measure mass-accumulation and after a five-day interval to measure mass-loss. A free-space microwave reflection measurement system was implemented to track and quantify changes to the absorption capabilities of the CAA. A physically-based electromagnetic model was developed to characterize the changes caused by salt water absorption, and good agreement was observed with measured data.
Various multiple-input multiple-output (MIMO) antenna systems for vehicles are presented in this paper usingtwo uniquely designed elements: low profile wideband Planar Inverted-F antenna (PIFA), and compact wideband monopole for automotive application in the sub-6 GHz 5G systems and Vehicle-to-Everything (V2X) communications that operate on the frequency range from 617 MHz to 6 GHz. This paper presents different MIMO configurations to be used in a low-profile housing or a shark fin style on the vehicle's roof. Each MIMO system achievesa satisfactory MIMO performance across the whole band withsuitable physical dimensions. The envelope correlation coefficient (ECC) and diversity gain (DG) are calculated using MATLAB in each MIMO configuration as they represent the two key factors in the MIMO performance. Simulation results are presented along with measured data on 1-meter rolled-edge ground plane (GND) and on vehicle's roof from properly cut metal sheet prototypes. The results are discussed in terms of VSWR, passive isolation between elements, combined radiation patterns, port-efficiencies, ECC and DG.
A simple, compact, contactless, and high sensitivity metamaterial-inspired sensorhas been developed to detect and classify precious transition metals in the S- and C-band regime, using reflection coefficients. A multi-band metamaterial, quadruple concentric circular split ring resonator, is specifically designed as a sensing enhancer, where the additional bands can effectively trigger the electromagnetic properties, as well as enhance the differentiation between the testing metal samples. The proposed sensor was tested on precious transition metals, silver, platinum and gold thin slabs of various thicknesses, from 0.5 μm to 3 mm. Five resonances were established in the frequency range of 2-8 GHz. Distinguishable frequency responses generated from different metal samples at those five resonances specify the capability of classifying the metal contents and thicknesses.