摘要:

In this work the problem of the Uyadic Green's Functions ( DGF ) is investigated so, that a more rigorous foundation of their theory and a clarification of the origin and meaninq of their symmetrical properties is obtained. The adjoint problem is formulated, the UGFs for all possible cases of boundary conditions for the Vector Helmholtz equation are defined and their symmetrical properties, as well as the assumptions under which these ones hold, proved. The analysis begins with the examination of the basic problem of the DGF for a finite homoqeneous space, which results to a more general statement of the Love equivalence theorem and the investigation of the possibilities on the choice among more DGFs for the solution of a problems: it passes to the problem of two spaces in contact (two layered medium), where the coupling relation between the two DGFs is determined and oroved to be arbitrary in the general case; and, finally, it is generalised for the case of a medium with arbitrary number of layers.

ISSN:0272-6343    

DOI:10.1080/02726348708908171

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Generally, the response of a second-order system to an impulse excitation can be expressed in terms of a series of exponentially damped sinusoids. This technique is called the singularity expansion method (SEM). Knowing the SEM parameters, it is possible to characterize the system response and to search for conditions required to maximize a particular attribute of the response signal. Thus the goal of this study is to present techniques whereby the SEM parameters can be extracted from measured data, and in particular, data with a low s1gnal-to-noise ratio. A nonlinear digital filter technique that uses a circular serial correlation test is shown to provide a preprocessing technique which allows the classic Prony method to be applied to the data. The technique also estimates the noise level and accomodates the presence of non-stationary noise Results are presented for typical noisy data, as well as for analytical data with added white-Gaussian noise.

ISSN:0272-6343    

DOI:10.1080/02726348708908172

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

A curved structure consisting of an imperfectly conducting circular cylinder coated by any number of coaxial thin anisotropic layers separated by isotroplc regions of different materials is considered. Each thin anisotroplc layer is represented by a sheet with an anisotropic Jump Impedance. Thus, the structure is a generalization to the anisotropic case of Jaumann absorbers on curved surfaces. For a normally incident and obliquely polarized plane wave, the scattered field is determined via a chain-matrix algorithm. An optimization procedure is developed to minimize the radar cross section over an assigned frequency band by varying the geometric and electromagnetic parameters of the structure. Numerical results based on this design procedure are presented and discussed.

ISSN:0272-6343    

DOI:10.1080/02726348708908173

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

The arm-cap Junction of a biconical antenna supports a ring charge, the value of which is calculable in an electromagnetically exact way. The field intensity Just off its surface Is singular but integrable. Charge values are calculated Using conservation of charge and Causa' law. Observations Include that, in differential dipole radiators, most of the dipolar current oscillates between the driving source and the ring charge. Radiated power is roportional to the square of the small cap current.

ISSN:0272-6343    

DOI:10.1080/02726348708908174

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

This paper discusses the effect of radiation losses in the responses of parallel-line mm-wave open microstrip filters. The analysis presented is based on a method that accounts for the presence of the substrate and the associated surface wave propagation. This analysis is very accurate for a wide frequency range, starting from a few GHz up to millimeter and submillimeter waves, where existing techniques fail to apply. The computer codes generated by this work can be effectively used in conjunction with available design packages to evaluate unwanted radiation losses and possibly eliminate them by slightly modifying the geometry of the filters. Comparison of theoretical results from the presented analytical method with experimental data shows excellent agreement.

ISSN:0272-6343    

DOI:10.1080/02726348708908175

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

A method of improving the accuracy of traditional methods (Guru and Chen [6], Hagmann and Gandhi [7]—[8], Hagmann and Levin [9], and Livesay and Chen [13] of solving integral equations has been obtained. We now have exact formulas for the accuracy of protective approximation methods (Gohberg and Feldman [5], Neittaanmaki and Saranen [20]) for solving integral equations. For a class of approximation schemes for estimating the solution of integral equations of electromagnetic scattering, we can develop a systematic procedure for reducing the original infinite rank integral equation to an exact finite rank integral equation capable of being completely analyzed by digital computer. In this paper the method is illustrated for the popular pulse basis function method(Guru and Chen [6], Hagmann and Gandhi [7]—[8], Hagmann and Levin [9], and Livesay and Chen [13]).

ISSN:0272-6343    

DOI:10.1080/02726348708908176

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

The scattering of electromagnetic waves off a dielectric wedge is approached using an integral equation formulation. This formulation seeks to express the interfacial field as a combination of the geometric optics field and a diffraction field made up of a number of Bessel functions. Both null field and interfacial integral equations are used to overspecify the problem and thus, seek a least squares approximation to the interfacial field on the wedge interface. The optimum number of Bessel functions used to specify the diffraction field is sought through a minimization of additional interfacial fields of equations. The unboundedness of the wedge interface problem makes it particularly difficult; the use of global basis functions embodying limiting forms of quasi-analytic formulations appears to be an efficacious approach to computing the scattered field. The methodology is quite general, lending itself to the analysis of a wedge with any dielectric constant, having any arbitrary angle.

ISSN:0272-6343    

DOI:10.1080/02726348708908177

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

A spectral formulation for the analysis of arrays of thin conductors arranged in a skew three-dimensional lattice and lying in one of the lattice planes is presented. Two cases are considered, i.e. homogeneous and plane stratified dielectric medium. In the first case, the Fourier transformation is three-dimensional; in the second one, the spectral approach is Limited to the plane of stratification and the transmission line technique is used for the analysis in the longitudinal direction. The eigenmodes of the structure (Bloch waves) are studied in detail and some significant examples of dispersion curves are presented. The concepts of passband and stopband of Bloch waves arc exploited to define a synthesis procedure for high performance multiple grid frequency selective surfaces, which are considered as three-dimensional periodic structures truncated in the direction of a lattice basis vector.

ISSN:0272-6343    

DOI:10.1080/02726348708908178

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor