摘要:

Different methods for controlling the coupling between a two-conductor microstrip transmission line are investigated in this paper. The transmission line consists of two thin perfectly conducting strips with a rectangular notch between the strips, two layers of dielectric substrate, and a dielectric overlay. The formulation and solution technique are based on the equivalence principle, a free space Green's function, and the method of moments. It has been found that the coupling between the conducting lines can be reduced significantly if dielectric material between the lines is removed. Further reduction in coupling is observed when the relative permittivity of the upper substrate layer is made smaller than that of the lower substrate. Coupling can be maximized if the notch is filled with dielectric material having large relative permittivity compared to that of the substrates. If the strips are covered with a dielectric overlay (or superstrate), the coupling will be substantially increased. Moreover, with the right combination of dielectric material layers and the right geometry, it is possible to equalize the even- and odd-mode phase velocities while having some control over the coupling capacitance.

ISSN:0920-5071    

DOI:10.1163/156939393X00877

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

An accurate numerical solution for the electromagnetic scattering from an infinite strip grating is presented, where the strips are loaded with a symmetrical pair of dielectric slabs. The direction of propagation and the polarization of the incident plane wave are arbitrary. The boundary value problem is reduced to a solution of singular integral equations, which are discretized by an application of the moment method. Numerical computations are performed mainly for the purpose of designing polarization diplexers. Dependence of diplexing characteristics on grating parameters is examined in detail. Appearance of cross-polarized field at skew incidence is referred.

ISSN:0920-5071    

DOI:10.1163/156939393X00886

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Microwave diversity imaging has the potential to become a very useful tool for understanding and analyzing electromagnetic scattering from complex objects. In order for this potential to reach fruition, however, a number of aspects must be dealt with thoroughly: e.g., (1) the method for retrieving the image from scattering measurements must be appropriate for the type of object under investigation; (2) the selection of imaging technique must be made, where possible, so as to obtain direct relationships between image intensity (or texture) and scattering mechanisms of interest; and (3) the effects of measurement parameters, such as imaging aperture and frequency, and processing effects, such as gating and windowing, must be well understood. This paper addresses (2) experimentally, with a basis in image retrieval under the physical optics (PO) approximation. It is shown, via images of single cylinders and simple arrangements of cylinders, that multistatic imaging can lead to better understanding of electromagnetic wave-object interaction than is possible using conventional monostatic and bistatic imaging techniques.

ISSN:0920-5071    

DOI:10.1163/156939393X00895

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

An efficient asymptotic closed-form dyadic Green's function for the grounded double-layered anisotropic uniaxial geometry is developed. The large parameter of this asymptotic development is directly proportional to the lateral separation between the source and observation points. However the asymptotic solution remains accurate even for very small (a few tenths of a wavelength) lateral separation of the source and field points. Thus, the use of the asymptotic approximation of the Green's function can lead to a very efficient moment method (MM) solution for the current on the scatterer within the anisotropic unaxial substrates. Moreover, the asymptotic closed form dyadic Green's function has been cast in such a form that the physical behavior of the electromagnetic fields due to anisotropy of the medium reveals itself through a simple mathematical parameters. Thus, the physical understanding of the interaction of the spatially confined source with a grounded anisotropic (uniaxial) double-layered slab is greatly enhanced through the newly developed asymptotic closed form representation for the dyadic Green's function.

ISSN:0920-5071    

DOI:10.1163/156939393X00903

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

In this paper, a method is given for calculating the phase constant of waveguide structures used in integrated optics. As a basis, the Rayleigh-Schrödinger perturbation approach of first and second order is applied. Due to the knowledge of the limiting behavior of the phase constant at high frequencies, an appropriate functional approximation is derived and combined with the mode-matching procedure to reduce the numerical effort. Results are obtained for the HE00mode and EH00mode. A comparison with more accurate numerical techniques, as the method of lines for instance, shows a good correspondence.

ISSN:0920-5071    

DOI:10.1163/156939393X00912

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

In this paper we use range profiles as the feature vectors for data representation, and use the matching score method and the neural network approach to automatically identify aerospace objects. The backpropagation model is employed in the neural network approach to train a neural network. Recognition performances with different training methods are compared and discussed. Experimental results show that the neural network approach has a little greater capability in identifying similar feature vectors and has stronger immunity to Gaussian noises than the matching score method does in certain cases. However, the latter method is range-shift invariant while the former method may fail to recognize a shifted feature vector. We propose a centroid-aligned method to overcome the range shift problem. Simulated results show that this method is simple and effective.

ISSN:0920-5071    

DOI:10.1163/156939393X00921

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

ISSN:0920-5071    

DOI:10.1163/156939393X00930

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

ISSN:0920-5071    

DOI:10.1163/156939393X00949

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor