Size Reduction for Yagi-Uda Antennas by means of Reactively Loaded Reflectors and Directors
Graz University of Technology, Austria
Yagi-Uda antennas are widely used antenna systems in wireless communication applications. Especially due to their ability to enable high antenna gain while maintaining relatively low production costs, these antenna systems are very attractive. Due to the fact that the antenna characteristics like e.g. the forward directivity or the antenna impedance are very sensitive to variations of the geometry parameters of the antenna, numerical optimization techniques are typically utilized to find the optimal geometrical parameters. Depending on the number of directors such antenna systems can be relatively large. To reduce the size of the whole antenna structure a reactive loading of the reflector and the directors by means of lumped circuit elements is proposed. The optimized determination of the lumped element parameters is carried out together with the geometrical antenna parameters in a multi-objective sense. The optimization relies on the differential evolution strategy. To compute the forward problems within the optimization process the mutual impedance method is applied.
GPR Antenna Design Framework Validation
1Federal University of Santa Catarina, Brasil; 2Federal Institute of Santa Catarina, Brazil; 3Federal University of Minas Gerais, Brazil; 4University of Akron, EUA
An antenna can be considered as a two-port transducer system characterized by a transfer function that can be frequency-dependent and may have a non-linear phase response. The performance of this complex device is critical for time or frequency-domain ground penetrating radar (GPR) systems. We recently published a framework for GPR antenna design and optimization, outlining the fundamental GPR system theory in order to discuss procedures for improving antennas to GPR. This paper shows some applications in order to validate the proposed framework.
Phase Shifter Circuit Composed of Blanch Line and Rat-race Coupler for Orbital Angular Momentum Wave
Tokyo Metropolitan Industrial Technology Research Institute, Japan
This paper presents a phase shifter circuit generating electromagnetic wave having an orbital angular momentum (OAM). A generation of the OAM wave needs a lot of phase shifters in order to feed many antennas with signal shifting phase from 0 to 2lp. The presented feeding circuits generate 0, 90, 180 and 270ﾟ phase shift signals and create the OAM waves by combining phase shift signals. In this research, phase shifter composed of a Rat-race coupler and two Branch line couplers is presented. The presented circuits successfully shift phase from 0ﾟ to 90, 180, and 270ﾟ and combine phase shift signal in order to generate electromagnetic waves with OAM states l=0, ±1, ±2. The generated OAM signals were found to have an orthogonality of 12 dB.
Research on Resonant Method for Increasing Coil Space of Electromagnetic Logging tools
1Institute of Electrical Engineering, Chinese Academy of Science, Beijing 100190, China; 2University of Chinese Academy of Sciences, Beijing 100049, China
Long coil space electromagnetic logging is urgently needed for petroleum exploration. The receiving voltage decreases sharply with the increase of coil space becomes the bottleneck problem. In this paper, a new coil resonant method for increasing the coil space is proposed. The integral solution of magnetic field generated by coil in horizontal anisotropic formation is deduced, and based on this the resonant coupling equations are established. The receiving voltage increases obviously with the coil resonant method and the amplitude ratio which is used for formation resistivity inversion keeps unchanged. The increment of the coil space is positively correlated with the voltage magnification factor due to different coil resonant matching. A prototype was built to demonstrate the effectiveness of the method. The coil space increases from 1.6m to 3.5m when the voltage magnification equals to 10 with the parameters given in this paper, which is consistent with the theoretical results.
Scattered Field Formulation of FDTD Method Combining with Time-Domain EFIE and MFIE Based on Surface Equivalent Theorem
Muroran Institute of Technology, Japan
This paper proposes a scattered field formulation of the FDTD method combining with a time-domain electric field integral equation (EFIE) and magnetic field integral equations (MFIE) based on a surface equivalence theorem. The scattered field formulation enables us to effectively reduce computation cost for the case that the scatterers are located at a far distance from field sources of electromagnetic wave since we need to calculate the scattered field component only in the region around the scatterers. Then it is required for the use of the scattered field formulation that the incident field component produced by the field source has to be given by an analytical form. In this work, the scattered field formulation of the FDTD method is applied to the case that the field source contains conductors such as a dipole antenna, horn antenna, in which it is necessary to numerically calculate the electromagnetic fields from the field sources, combining with the EFIE and MFIE on a virtual surface which encloses the field sources.
Marching On–In–Time Unstructured–PEEC for Conductive, Dielectric, and Magnetic Media
1Università degli Studi di Padova, Dipartimento di Ingegneria Industriale, Padova, Italy; 2Univ. Grenoble Alpes, CNRS, Grenoble INP, G2Elab, 38000 Grenoble, France
The Marching On–In–Time Partial Element Equivalent Circuit method is presented for the study of time–domain electromagnetic problems. The method allows the transient analysis of electrically large electromagnetic devices consisting of conductive, dielectric, and magnetic media coupled with external lumped circuits. The method is also suitable for inhomogeneous and anisotropic materials.
Multi-Point Fast Matrix Generation Technique for Planar Circuits Simulation with The Method of Moments
The calculation of the interaction integrals between basis and test functions during the matrix filling step in the Method of Moment, is a time consuming task for electrically small to medium planar structures like antennas despite the fact that approximate analytical expressions exist. The contribution of this paper is to present an improved multi-point fast matrix generation technique for more accurate approximation in comparison with the single point fast matrix generation technique and less computation time in comparison with the analytical technique
Analysis of Multiple Screen Diffraction at Microwave Frequencies
1Federal University of São João del-Rei (UFSJ), Brazil; 2Federal University of Minas Gerais (UFMG), Brazil; 3Federal Center of Technological Education of Minas Gerais
This paper presents preliminary results about multiple screen diffraction loss obtained using two numerical simulation techniques: a Finite-Difference Frequency-Domain (FDFD) and a Time-Domain (FDTD) based method. The numerical simulation is compared with a measurement campaign performed at microwave frequencies. The main contribution is the characterization of diffraction effects in the frequency band from 1 to 8.5 GHz, which has the potential to be used in future wireless mobile communications.
A Rigorous Path Integral Scheme for the Two-Dimensional Nonstandard Finite-Difference Time-Domain Method
1Asahikawa-shi, Japan; 2Niigata Institute of Technology, Japan; 3Aristotle University of Thessaloniki, Greece
The nonstandard finite-difference time-domain (NS-FDTD) method discretizes the continuous space into aggregated orthogonal cells; therefore, its geometric fidelity and overall accuracy inevitably deteriorate for objects with non-orthogonal shapes. To overcome this issue, an efficient contour-path scheme, stemming from the concept of its FDTD counterpart, is introduced for the NS-FDTD technique in two dimensions. The novel path integral model comprises two different integration paths on a square grid for each node, while the algorithm is further optimized through its numerical dispersion equation. It is computationally proven that the featured scheme is very precise, namely at the level of the NS-FDTD method, thus expanding its applicability to structures with highly-curved surfaces and demanding fine details.
Bloch Analysis for the Study of Degenerate Band Edge Modes in Periodic Substrate-Integrated Waveguides
1Laboratoire d'Electronique et Électromagnétisme (L2E), Paris, France; 2Dept. of EECS, University of California-Irvine, Irvine, CA 92697, USA
An analysis of degenerate band edge modes in substrate-integrated waveguides is performed by means of a Bloch analysis of a 4-port unit cells, based on a suitably defined transmission matrix. A degenerate band edge is a novel dispersion condition which provides a strong dispersive behavior and nearly flat dispersion diagram near the band edge. The resonance supported by degenerate band edge modes has a giant field enhancement near the band edge and has several possible applications (amplifiers, oscillators, sensors, etc). A design of the unit cell of a periodic substrate-integrated waveguide supporting a degenerate band edge condition is given and the resonance in the truncated resonator is discussed.
Antenna Array Pattern Synthesis Using a Novel Iterative Method
1Budapest University of Technology and Economics, Hungary; 2Czech Technical University in Prague, Czech Republic
In this paper, we investigate a novel iterative antenna array synthesis method. After defining the synthesis algorithm, we prove that the the discrepancy between the target and the synthesized pattern in a certain norm converges to the theoretical lower bound. Some numerical examples are shown to illustrate the convergence properties of the proposed method. Possible applications of the method include circularly polarized patterns, since it can handle the rotation as well as translation of the antenna elements.
Solving Nonlinear Eigenvalue Problems for Waveguide-Coupled Cavities Using an Integral Solver with Subspace Projection
TU Berlin, Germany
The standard curl-curl eigenvalue problem in discrete electromagnetic formulations becomes non-linear, if the system matrix contains additional expressions which depend on frequency, i.e. the searched eigenvalue. This is the case, e.g., for models based on the Finite Integration Technique (FIT) and special radiating boundary conditions for waveguide-coupled cavities.
Such non-linear eigenvalue problems are a special challenge to modern solvers. In this paper, an improvement of a nonlinear eigenvalue solver based on Beyn's contour integration technique is presented. Since the main computational effort arises from the solution of a number of large linear systems along the integration contour, a method using reduced order modeling is presented. The validation example is the calculation of a number of eigenfrequencies in a rectangular waveguide filter.
Comparison of Finite Element Formulations for the Modelling of High-Frequency Effects in Electromagnetic Coils
1University of Liège, Belgium; 2University of Artois, France
The accurate prediction of coupled inductive and capacitive effects in electromagnetic coils is becoming of crucial importance in several industrial applications, either due to the increase of operating frequency or to the increase of voltage levels. In this paper we review and compare 2D and 3D finite element formulations of electromagnetic coils able to predict both inductive and capacitive effects, in order to design approximate 2D models whose computational complexity is compatible with current industrial design practice.
Application of Metamaterials Based on Transmission Line Parameters in Wireless Power Transfer
Pontifical Catholic University of Minas Gerais, Brazil
Metamaterials are normally associated with resonant structures composed by metallic rings or others geometries. These structures operate around a resonance frequency where the surrounding medium presents negative values of permittivity and permeability. However, there is another metamaterial approach based on transmission line parameters that does not depend on resonances to present negative parameters values, which makes possible to have a larger bandwidth, less ohmic losses and more flexibility during the project phase. Some applications, like wireless power transfer, can benefit from these characteristics. Using some consolidated references about the theme, we present this metamaterial approach and its application like lens to improve wireless power transfer.
An implicit hybridizable discontinuous Galerkin time-domain method to solve the S-parameters in the waveguide port
School of Electronic Science and Engineering, University of Electronic Science and Technology of China, Chengdu
It is important about energy coupling for the waveguide port. In order to compute its transmission characteristics, an implicit hybridizable discontinuous Galerkin time-domain (imHDGTD) method is proposed to solve the S-parameters. Compared with classical discontinuous Galerkin time domain (DGTD) method, the imHDGTD method has a fewer number of degrees of freedom (DOFs). By using the matrix solving technology, the imHDGTD method can accelerate the iterative solutions of the global linear system when using the implicit time scheme. Since the waveguide excitation source takes the field disappearance in the computational region as the sign of iteration termination, the imHDGTD method can effectively shorten the computational time. What’s more, in order to reduce the numerical reflection caused by space truncation, the waveguide port is truncated with the perfectly matched layer (PML) in the imHDGTD method. Some tests show the S-parameters of the imHDGTD method are consistent with the results of DGTD. When the mode is made up with locally refined meshes, the time step can be increased by using the imHDGTD method.