摘要:

In this paper the elliptic-hyperbolical waveguide is analyzed with the method of the separation of variables. A suitable set of eigenfunctions is defined and the TE and TM solutions for an elliptic sectoral guide and for the ridged elliptical guide are presented. Contour plots of the electric field distribution for the first fundamental modes in an elliptic sectoral guide are shown and the dispersion characteristics of the double ridge elliptical guide are analyzed as functions of the geometry of the guide.

ISSN:0920-5071    

DOI:10.1163/156939300X00248

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

In this paper we describe some recent mathematical results concerning Pocklington's integro-differential equation for the current induced on a straight, thin wire by an incident harmonic electromagnetic field. These results show that this equation is well-posed in suitable function spaces and describe the continuity and smoothness properties of the solution compared with the incident field. We also describe some new rigorous convergence results for a simple Galerkin type numerical solution method for the equation.

ISSN:0920-5071    

DOI:10.1163/156939300X00257

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

This paper presents an efficient method to solve the problem of radiation from conformal aperture and microstrip antennas mounted on arbitrarily-shaped conducting bodies. The method, based on the surface equivalence and reciprocity principles, uses a combination of the Finite Difference Time Domain (FDTD) and Method of Moments (MoM) techniques to substantially improve the computational efficiency of the radiation pattern calculation. When the geometry and location of the radiating element are modified, only a small portion of the overall analysis requires re-simulation. This leads to a significant improvement in computational efficiency over presently-used techniques, and can substantially improve design efficiency when included in an optimization loop. The technique is first validated by solving two canonical problems, namely a thin slot which is oriented either axially or azimuthally on an infinitely long, perfectly conducting cylinder. These patterns are then compared to those produced by the same slots mounted on finite length cylinders. Finally, patterns are computed for a cavity-backed elliptical patch antenna mounted on an infinite-length PEC cylinder and compared to patterns computed by an alternate method.

ISSN:0920-5071    

DOI:10.1163/156939300X00266

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

In the radar ranging, the echo delay depends on the movements of the target and the transceiver during wave propagation. Thus, the exact formula for determining the radar echo time is implicit. In this investigation, the forward and the backward propagation times are expressed in terms of the separation distance of the target and the transceiver at the instant of wave emission. Thereby, an explicit second-order formula for the radar echo time is derived, which is helpful in high-precision radar, such as the interplanetary radar.

ISSN:0920-5071    

DOI:10.1163/156939300X00275

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

This work presents an application of the FD-TD method in simulating electromagnetic fields and analyzing a planar microstrip filter. The frequency dependent characteristics of the microstrip filter are derived from the full-wave analysis in the time domain. The motivation of this paper is to establish the validity of the FD-TD method in modeling circuit components for MMIC CAD applications. The numerical results are compared to these existing predicted results as well as measurement data. A very good agreement is thus obtained from the comparison. It is, however, realized that with the implementation of the recent Berenger's Perfectly Matched Layer (PML) as an excellent absorbing wall, the computational speed for a given accuracy is much faster than the previous calculation in the filter analysis.

ISSN:0920-5071    

DOI:10.1163/156939300X00284

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

This article presents a numerical technique based on the modal-expansion method for modeling a multi-sleeve monopole antenna fed through an infinite ground-plane by a coaxial transmission line. The modal-expansion analysis is facilitated by introducing a perfectly conducting boundary at a variable height over the ground-plane of the monopole. The resulting structure is then divided into a number of regions and the electromagnetic field components in each region are expanded into the summation of its modal functions. The current distribution over the monopole and sleeve surfaces as well as the antenna's input impedance are computed by finding the expansion coefficients through matching the tangential field components across the regional interfaces. Numerical results for the surface current distribution and input impedance are presented and discussed with emphasis laid on single- and double-sleeve monopole antennas.

ISSN:0920-5071    

DOI:10.1163/156939300X00293

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

This paper presents an efficient analysis of a microstrip antenna in multilayered media using the method of moments (MoM). The general forms of spectral-domain Green's functions for multilayered media are converted into the spatial-domain Green's functions using the discrete complex image method (DCIM). With the spatial-domain Green's functions, the mixed potential integral equation (MPIE) is discretized in spatial domain, and the resultant system of equations is then solved using the biconjugate gradient (BCG) method. As applications, resonant frequencies of microstrip antennas in multilayered media are analysed. The numerical results show that the present method is an efficient and accurate scheme for analysing microstrip antennas in multilayered media.

ISSN:0920-5071    

DOI:10.1163/156939300X00301

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

To understand the mechanisms of decorrelation in interferometric SAR (InSAR) images of bare soil, a model has been developed. Under the Kirchhoff and stationary phase approximations, coherence can be related to the statistical variations of dielectric constant and roughness parameters of surfaces. With the help of an empirical model for the dependence of dielectric constant on soil moisture, coherence due to the inhomogeneity of soil moisture is numerically demonstrated. It has been shown that the decorrelation of the radar signal from rough soil is mainly due to the moisture variability within the resolution cell. The effect of roughness on decorrelation is complex. The effect is negligible compared to that of the dielectric variability for homogeneous resolution cells (no dielectric variability within a resolution cell). However, the coherence depends strongly on the roughness parameters for resolution cells with large moisture variability. It is concluded that the loss of coherence induced by variability of dielectric constant can be related to the relative variation of moisture expressed by the ratio of standard deviation and mean value, and that large relative variations of moisture could lead to much decorrelation. If the moisture variability is small the coherence will be very high even if the values of mean moisture of the two SAR observations are different, which means that coherence can be high in spite of much backscatter differences.

ISSN:0920-5071    

DOI:10.1163/156939300X00310

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

An effective wavelet based multigrid preconditioned conjugate gradient method is developed to solve electromagnetic large matrix problem for millimeter wave scattering application. By using wavelet transformation we restrict the large matrix equation to a relative smaller matrix and which can be solved rapidly. The solution is prolonged as the new improvement for the conjugate gradient (CG) method. Numerical result shows that our developed wavelet based multigrid preconditioned CG method can reach large improvement of computational complexity. Due to the automaticity of wavelet transformation, this method is potential to be a block box solver without physical background.

ISSN:0920-5071    

DOI:10.1163/156939300X00329

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Non-contact moisture content measurement of corrugated board on-line, possess significant production advantages which ratify superior productivity and quality control in the corrugated board manufacturing processes. This paper discusses the specific theoretical and practical aspects of microwave moisture content measurements and gives some experimental data obtained from moisture content measurements of typical cardboard materials used in the corrugated board industrial production processes. Regulating the pre-prescribed level of the moisture content during manufacturing is an imperative parameter for drying. The method proposed utilises part of microwave heating energy to control moisture content of the process. The correlation equation between absorbed power and moisture content was determined, in order to program the controlling hardware feeding the drying power.

ISSN:0920-5071    

DOI:10.1163/156939300X00338

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor