In this paper, the left-handed metamaterial which acts as a lens is employed to improve the performance of a microstrip patch antenna. The left-handed metamaterial used in this work is a three-dimensional periodic structure which consists of circular split ring resonators and thin wires. The metamaterials three dimensional periodic structure shows angular independency characteristics in wide range angles, so it acts as a metamaterial lens. However, the MTM structure infinite periodicity truncation has no impacts on the MTM lens scattering, effective parameters and homogeneity. The left-handed metamaterial is placed in front of the microstrip patch antenna and due to the negative refractive index property of the left-handed metamaterial; the radiated electromagnetic beam size decreases which results in a highly focused beam. The proposed antenna has been designed and simulated using CST microwave studio, and the metamaterial effective parameters are extracted from the S parameters by using Nicolson-Ross-Weir algorithm and by selecting the appropriate ambiguity branch parameter. Furthermore, the angular independency of the metamaterial lens has been verified by rotating the metamaterial structure with respect to the excitation probe of the transverse electromagnetic waves and extracting the S-parameters and the effective parameters for each rotation angle. A parametric analysis has been performed to study the effects of the patch antenna and left-handed metamaterial lens separation and the size of the three dimensional left-handed metamaterial structure on the radiating properties and the impedance matching of the proposed antenna. For the experimental verification, the proposed antenna operating at 10 GHz is fabricated; the return loss, radiation pattern and gain for the proposed antenna with and without metamaterial are measured. Furthermore, the results show that the antenna gain is improved by 4.6 dB which validates the concept of beam focusing using negative refractive index metamaterial structure, while the return loss and bandwidth are slightly reduced. The simulation and experiment investigated the idea of the beam focusing using negative refractive index metamaterial lens in microwave regime.
We apply the Gabor frame as a projection method to numerically solve a 2D transverse electric-polarized domain-integral equation for a homogeneous medium. Since the Gabor frame is spatially as well as spectrally very well convergent, it is convenient to use for solving a domain integral equation. The mixed spatial and spectral nature of the Gabor frame creates a natural and fast way to Fourier transform a function. In the spectral domain we employ a coordinate scaling to smoothen the branchcut found in the Green function. We have developed algorithms to perform multiplication and convolution efficiently, scaling as O(NlogN) on the number of Gabor coefficients, yielding an overall algorithm that also scales as O(NlogN).
Electromagnetic field modal expansion is traditionally an effective technique for solving Maxwell's Equations for numerous high-frequency engineering problems. In this paper, an alternative form of electromagnetic field representation is described. It is based on the Riemann-Silberstein vectors, which are a linear combination of the electric and magnetic field vectors. Utilizing such combination in homogeneous space, Maxwell's Equations are converted into a system of two independent equations. Under these circumstances, each vector describes the total electromagnetic field of an ideal circular polarization. Electromagnetic fields are simply expressed in the form of the Riemann-Silberstein vectors using the helical coordinate system and special functions, which form a set of generalized spherical harmonics. The new representation of vector spherical harmonics differs in simplicity and symmetry while having a more physically apparent expression. The amount of computational work is reduced due to the initial independence of the Riemann-Silberstein vectors. The purpose of this paper is to show the efficiency of a new approach that is based on Riemann-Silberstein vector field representation and spherical wave expansion.
Making use of mode matching method, a theoretical analysis of a metamaterial layer is presented. The unit cell of the structure is modeled by a TEM waveguide, and the metamaterial element is supposed as a discontinuity in the waveguide. Analyzing the structure using this model, mathematical relations between s-parameters of a metasurface are extracted. It is evident that the variation of each s-parameter is limited to an arc of circle on Smith chart. The key factors determining the location of each circle on plane are specified. Moreover, a discussion on the role of metasurface element in the determination of s-parameters of the structure is given. The variations of scattering transfer parameters on the plane are determined, too. The steps needed to derive these relations are described. Using these relations, simple and straightforward formulas are devised which can be used to predict the response of the metasurface. Finally, some metasurfaces will be analyzed by full-wave method. The new relations are well-agreed with simulation results.
Alternating current interference from power transmission lines on nearby metallic pipelines has been a topic of research in the past years. Of particular interest is the induced voltage on metallic pipelines due to the time varying electromagnetic fields coupling from the transmission lines. Several related studies dealing with this problem have been published. Nevertheless, the issue of current phase shift variation and its effect on the voltage induced on metallic pipelines has not been fully covered yet. In view of this, we present the computation of the induced open circuit voltage on a buried metallic pipeline running in parallel with the power transmission lines in three Rand Water sites, South Africa. The computation was performed using Carson's relations and power system concepts of mutual impedances between two circuits. The variation in current phase shift was considered for six different phase conductor arrangements. The overall simulation results yield useful information. The computations show that the induced open circuit voltage changes significantly with different phase arrangements and with variations in the current phase shift between the two circuits. In this work, the characteristic nature of the variation in the induced open circuit voltage for the six phase arrangements and phase shifts are examined in more detail. We concluded that in placing buried pipelines in the vicinity of AC double-circuits power lines, it is essential to consider the phase arrangement of the line and current phase shift between the two circuits. These, together with other line parameters, are vital in evaluating the induced voltage with the pipe position before installation and for the design of effective AC mitigation techniques.
Nowadays inductive powering has become a widely spread technique in existing and emerging implanted medical devices (IMD). The geometry of coils couple plays a key role in the design, optimization and evaluation of a biomedical inductive powering unit (IPU). We have proposed a relatively fast method for an execution of these procedures, which is based on a mutual induction calculation using GPU parallel computing. Generally, our approach is to calculate mutual inductance as a function of uncontrolled (axial distance, lateral distance, inclination) and controlled (coils radii, turns numbers, distance between turns) geometric parameters of a coil couple. Calculated geometric functions in its turn are used in the design and optimization procedure to evaluate an IPU performance (e.g., load power). Achieved time gain of the GPU calculations in comparison with the host CPU computing is up to 80 for sequential summation and up to 8 for parallel computing. Also, it is shown that precision of our method is comparable to the precision of existing electromagnetic field solvers, and at the same time, computation time is substantially less (time gain is about 7...8 for 2D case and about 100 and higher for 3D case). Additionally, we have verified our method experimentally and shown that results of the calculations are accurate enough to predict real IPU performance. Finally, we have given an example of an IPU design optimization using geometric functions calculated with the help of the proposed method.
This paper deals with the comparison of two actuators with different frameworks, for a direct drive active stick application. Each actuator will be compared with three different sets of specifications which impose many constraints as: high torque, small volume, low temperature, etc. The high required torque per unit of mass and the small volume allowed involve the use of synchronous Halbach permanent magnet (PM) topologies which have the best torque performances. In this article, an analysis and a comparison of two optimized actuators designed with a Halbach configuration are done. It is a linear actuator and a double airgap rotating actuator. The electromagnetic torque is calculated by the Laplace force for which the flux density generated by the Halbach PM configuration is defined by a Laplace equation and a Poisson equation. An analytical optimization under a set of nonlinear constraints will be realized with the analytical expressions of the torque we got previously. In order to validate the analytical model, finite-element analysis (FEA) simulations will be performed on the optimized structure. Finally, two actuators will be compared in order to give the best compromises for the stick application for each set of specifications.
Interior bearingless permanent magnet synchronous motors (IBPMSMs) are a new type of machines having two sets of windings in the stator, offering no lubrication and no mechanical friction, high efficiency, robust rotor construction, hybrid torque production nature and flux-weakening capability. In this paper, the suspension force modeling and the static electromagnetic characteristics of an IBPMSM are studied. The suspension force model of the IBPMSM is established and investigated based on the Maxwell tensor method. And then the static electromagnetic characteristics, including permanent magnet (PM) flux linkage, EMF, inductances, electromagnetic torque and suspension force, are discussed with the finite element analysis (FEA) method. The electromagnetic characteristics of the IBPMSM are very helpful for the design and optimization of the motor. The effectiveness of the proposed suspension force mathematical model is verified by comparing the theoretical results with FEA-based predictions. The work in this paper lays an important foundation for the optimization design and control strategies of the IBPMSM.
This paper presents the design and analysis of guided wave notch filters using the Lagrangian formulation for metamaterials. It is shown that the application of the Lagrangian is a convenient and effective way to select an appropriate filtering structure and determine the necessary configuration for desired filter performance. A WR-187 waveguide horn antenna is investigated with notch filters composed of broadside coupled and gap coupled split ring resonators. It is shown that broadside coupling offers significant tunability in a compact size. The filter exhibits an operational bandwidth from approximately 3.9-5.7 GHz with 40-150 MHz of instantaneous bandwidth. The fabrication of the horn antenna and split ring resonators is presented along with simulated and measured data that confirms the approach.
In the general framework of intelligent transportation, the increasing use of information communication technology in full or hybrid electric vehicles requires careful assessment of electromagnetic compatibility, with specific reference to the conducted emissions (CE) generated by the inverter in a broad frequency range (10 kHz-100 MHz). To this aim, this work reports a modelling approach for the prediction of CE in electric powertrains, which is based on circuit representation of each single subsystem, that is, the battery, the inverter, the three-phase synchronous motor, and the power buses composed of shielded cables. The proposed models are able to represent both low-frequency functional aspects and high-frequency parasitic effects of paramount importance for CE analysis, and can be implemented into a Simulation-Programme-with-Integrated-Circuit-Emphasis (SPICE) solver. The proposed modelling approach is exploited to simulate virtual CE measurements according to international standard CISPR 25, and to investigate the impact of setup features, including grounding connections of shields, the propagation of CE in electrically long power buses, the operating point (power, torque, speed) of the motor-drive system.