共查询到20条相似文献,搜索用时 31 毫秒
1.
Beggs J.H. Luebbers R.J. Ruth B.G. 《Antennas and Propagation, IEEE Transactions on》1993,41(9):1324-1327
The finite difference time domain (FDTD) technique is a popular method for analyzing electromagnetic scattering, radiation, and penetration problems. Several authors have recently applied the FDTD method to antenna radiation problems. To date, the antenna structures considered have been wire and conical monopole antennas, rectangular waveguides, pyramidal horn antennas, and microstrip antennas. Results from these analysis have been in the form of normalized field patterns and no results showing absolute gain have been presented. The article demonstrates the first staircased application of the FDTD method to the analysis of radiation from circular waveguides and other shaped-end radiators. Results of absolute gain versus angle are shown for a straight-cut circular waveguide and for two different shaped-end radiators. All FDTD analyses are full three-dimensional computations and are compared in each case with measured data 相似文献
2.
Wei Shao Bing-Zhong Wang Huilai Liu 《Journal of Infrared, Millimeter and Terahertz Waves》2006,27(9):1217-1225
In this paper, the application of the order-marching time-domain (OMTD) method to the solution of the cutoff frequencies of TE and TM modes in millimeter-wave waveguides is described. Starting from Maxwell’s two-dimensional (2-D) differential equations for TE or TM case, the OMTD method uses the orthonormality of weighted Laguerre polynomials and Galerkin’s testing procedure to eliminate the temporal variables and results in an order-marching scheme. To verify it’s accuracy and efficiency, the numerical results for millimeter-wave guided systems are compared with those of finite-difference time-domain (FDTD) method and analytical solutions. The OMTD method improves computational efficiency notably, especially for fine grid division problems restricted by stability constraints in the FDTD method. 相似文献
3.
Jaime Pitarch José M Catalá-Civera Felipe L Pe?aranda-Foix Beatriz García-Ba?os 《The Journal of microwave power and electromagnetic energy》2007,41(4):46-61
Waveguide structures are very popular in the microwave power industry due to their power handling capabilities. Modal expansion of the waveguide fields and application of the circuit theory allow for the division of a complex device into several simpler sections which can be analyzed separately with the best suited method. The modal techniques can be divided into two groups--those which analyze junctions or discontinuities and those which examine propagation characteristics. In this paper, a review of modal techniques for high power applications is given. Modal expansion of the fields in the waveguides is then performed and applied to modeling of k-furcated waveguides. The modal analysis based on the Coupled Mode Method is described for the waveguides partially filled with isotropic materials. A hybrid modal analysis coupled with Finite Element Method suitable for more complex waveguide structures is also described. Computational results obtained for some real-life microwave devices are presented. Excellent agreement was found when comparing the results with those generated with a commercial FDTD simulator demonstrates the validity and reliability of the proposed method. 相似文献
4.
A finite-difference-time-domain (FDTD) algorithm for the efficient full-wave analysis of a comprehensive class of millimeter-wave and optical waveguide structures is described. The algorithm is based on a two-dimensional graded mesh combined with adequately formulated absorbing boundary conditions. This allows the inclusion of nearly arbitrarily shaped, fully or partially lateral open or shielded guiding structures with or without layers of finite metallization thickness. Moreover, lossy dielectrics and/or lossy conductors are included in the theory. The algorithm leads to a significant reduction in CPU time and storage requirements as compared with the conventional three-dimensional eigenvalue FDTD mesh formulation. Dispersion characteristic examples are calculated for structures suitable for usual integrated circuits, such as insulated image guides, ridge guides, dielectric waveguides, trapped image guides, coplanar-lines and microstrip lines. The theory is verified by comparison with results obtained by other methods 相似文献
5.
A hybrid implicit-explicit finite-difference time-domain (FDTD) method for solving the wave equation in nonlinear optical waveguiding structures is proposed. The new scheme combines the computational simplicity of the explicit scheme in linear medium regions with the superior stability property of the partially implicit scheme in regions of nonlinear materials, thus eliminating potential problems of instability associated with nonlinearity. Simulation results for Kerr-type nonlinear slab waveguides and corrugated waveguides are presented and compared with those obtained using the conventional noniterative FDTD scheme 相似文献
6.
A class of microwave circuits described by a two-dimensional vector wave equation is defined. It is proposed to refer to them as vector two-dimensional or 2-DV circuits to distinguish them from circuits described by a two-dimensional scalar wave equation (typically referred to as 2-D circuits). It is shown that the 2-DV class contains some planar circuits filled with anisotropic media, two-dimensional waveguide discontinuities, and circular waveguide discontinuities. Calculation of dispersion characteristics of inhomogeneously filled hollow waveguides is an eigenvalue problem belonging to the 2-DV class. Application to the finite-difference-time-domain (FDTD) method to the analysis of 2-DV circuits is described. Examples show the efficiency of the method for several types of circuit 相似文献
7.
The finite-difference time-domain (FDTD) method is used for the analysis of magnetoplasma rectangular channel waveguides. Single and parallel-coupled waveguides are considered. The effect of varying the amplitude and the orientation of the bias magnetic field B0 on the dispersion characteristics of the first modes is examined. However, the FDTD formulation, does not excite evanescent modes for a sufficiently long time interval, particularly when in the presence of the propagating or dynamic modes. As a result, the nonreciprocal properties of these structures, primarily associated with the evanescent modes, could not be investigated 相似文献
8.
Two-dimensional (2-D) TEM horns are modeled using the finite-difference time-domain (FDTD) method. The boundary walls are perfect electric conductors and one wall, which does not align with the Cartesian grid, is approximated using a staircased representation. By carefully comparing the FDTD results to those of the analytic solution, one can make conclusions about the coarseness with which a boundary can be represented. It is found that staircasing errors are small when the staircase diagonal (the hypotenuse of the right triangle created by the stairstep) is smaller than half a wavelength at the highest significant frequency in the excitation. This rule-of-thumb is put forward as a necessary condition for the discretization of general problems. Results are also provided for some simple FDTD schemes that are designed to reduce staircasing errors. By using large aspect-ratio cells, a grid can be constructed that satisfies the rule-of-thumb given above. While this approach eliminates general staircasing errors, some errors persist owing to the presence of step discontinuities immediately adjacent to the horn feed. These errors can be further reduced by using a cell-splitting approach. It is shown that the contour path FDTD technique can be used to eliminate nearly all staircasing errors, while some additional improvement is shown to be provided by using a stabilized contour path FDTD approach. Finally, a recently proposed conformal technique that permits simple implementation is shown to provide results comparable with those of the stabilized contour path approach 相似文献
9.
This paper provides an accurate, versatile, and computationally efficient method for the analysis of slot-coupled transitions from microstrip-to-microstrip, and microstrip-to-rectangular and parallel-plate waveguides. The accuracy of this method is ensured by satisfying all the boundary conditions through a mixed electric-magnetic current integral equation formulation, combined with the moment method. Computational efficiency is achieved by limiting the discretization to only the strips and apertures and by using the accurate and rapidly convergent complex images. To verify the accuracy of this method, the transitions are analyzed using the finite-difference time-domain (FDTD) method. Experimental results are also obtained for some structures. Close agreement is found between the complex image results, the FDTD results, and experiment over a wide frequency range 相似文献
10.
It is well-known that the finite-difference time-domain (FDTD) method is subject to significant errors due to the staircasing of surfaces that are not precisely aligned with major grid planes. Dey and Mittra introduced a locally conformal method (D-FDTD) that has shown substantial gains in the accuracy of modeling arbitrary surfaces in the FDTD grid. A mesh generator for this purpose was reported by Yu and Mittra. In this paper, we present the formulation and validation of an alternative CAD-based mesh generator for D-FDTD that has improved capabilities for arbitrary three-dimensional (3-D) perfect electric conductor (PEC) geometries. This mesh generator is capable of importing AutoCad and ProE files of 3-D PEC scatterers and resonators. It can reduce the required FDTD grid resolution by up to 4:1 in each Cartesian direction in 3-D relative to conventional staircased FDTD models when modeling cavity resonances of complex PEC structures such as twisted waveguides. 相似文献
11.
A low crosstalk and wideband photonic crystal (PC) waveguide intersection design based on two orthogonal hybrid waveguides in a crossbar configuration is proposed. The finite-difference time-domain (FDTD) and coupled-mode theory (CMT) methods are used to simulate the hybrid waveguides of square lattice. The bandwidth (BW) and crosstalk of the intersection are investigated for various radii of the coupled cavities. It is shown that simultaneous crossing of the lightwave signals through the intersection with negligible interference is possible. The transmission of a 200-fs pulse at 1550 nm is simulated by using the FDTD method, and the transmitted pulse shows negligible crosstalk and very little distortion. 相似文献
12.
We investigate the performance and guiding properties of waveguides fabricated in a finite two-dimensional (2-D) photonic bandgap (PBG) structure. Confinement in the direction perpendicular to the plane of periodicity is achieved by fabricating the 2-D PBG structure in a high dielectric layer enclosed by two lower dielectric layers. Simulations using the finite-difference time-domain (FDTD) method are performed to investigate the energy transport in such waveguides. Good qualitative agreement is found with the experimental observations 相似文献
13.
本文提出了一种适合于求解各类复杂圆波导结构TE0和TM0模式的截止频率和色散曲线的FDTD分析方法,并可在一维空间中加以处理,大大提高了计算效率和减少了存贮量。本文对圆波导中TE0和TM0模式的截止频率和色散曲线进行了计算和分析,同时分析了网络剖分对计算结果精度的影响,并与已知的理论结果进行了比较,证实了这一方法的可靠性。作为实例,计算和分析了表面波圆波导结构的色散曲线,所得结果与实验结果和其它数 相似文献
14.
This paper presents a method that improves by orders of magnitude the accuracy of the finite-difference time-domain (FDTD)-calculated eigenfrequencies of photonic crystals. The method utilizes a variational expression for the eigenfrequencies of periodic structures. Applications to perfect crystals, waveguides, and resonant cavities are demonstrated. The paper confirms that the method can reduce the computational time by more than 90% while obtaining accuracy in frequency comparable to that obtained solely by the conventional FDTD method. 相似文献
15.
Pereda J.A. Vielva L.A. Solano M.A. Vegas A. Prieto A. 《Microwave Theory and Techniques》1995,43(2):350-357
The finite-difference time-domain (FDTD) method is extended to include magnetized ferrites. The treatment of the ferrite material is based on the equation of motion of the magnetization vector. Magnetic losses are also included in the equation of motion by means of Gilbert's approximation of the phenomenological Landau-Lifschitz damping term. The discretization scheme is based on central finite-differences and linear interpolation. This scheme allows the fully explicit nature of the FDTD method to be maintained. This extension of the FDTD method to magnetized ferrites is applied to the full-wave analysis of ferrite-loaded waveguides. The dispersion curves are calculated by using a recently proposed 2D-FDTD formulation for dispersion analysis which has been adapted to the present problem. The results for both the phase and attenuation constants of various transversely and longitudinally magnetized ferrite-loaded waveguides are compared with the exact values and with those obtained by means of Schelkunoff's method 相似文献
16.
A cylindrical mode-matching approach has been used to analyse dielectric-loaded waveguides and horns. The method is capable of analysing structures with many annular regions of different dielectrics. The technique has been validated by comparing with experimental results. 相似文献
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The multiresolution time-domain (MRTD) algorithm is applied to the problem of general two-dimensional electromagnetic scattering. A Haar wavelet expansion is utilized. A parallel between Haar MRTD and the classic Yee finite-difference time-domain (FDTD) algorithm is discussed, and results of simulations on canonical targets are shown for comparison. We focus on the incident-field implementation, which, in our case, consists of a pulsed plane wave. Also, we consider scattering in a half-space environment, with application to subsurface sensing. The results illustrate the advantage of the Haar MRTD method as compared with the classic FDTD, which consists of reduced memory and execution time requirements, without sacrificing accuracy 相似文献
20.
A direct three-dimensional finite-difference time-domain (FDTD) method is applied to the full-wave analysis of various microstrip structures. The method is shown to be an efficient tool for modeling complicated microstrip circuit components and microstrip antennas. From the time-domain results the input impedance of a line-fed rectangular patch antenna and the frequency-dependent scattering parameters of a low-pass filter and a branch-line coupler are calculated. These circuits were fabricated and the measurements made on them are compared with the FDTD results and shown to be in good agreement 相似文献