摘要:

Asymptotic expansions are constructed for the fields both near the edge and far from the edge of a right angle conducting wedge. These expansions are needed for an accurate numerical solution of the problem to be carried out. Furthermore, previous results, such as a constant nonzero value of the axial electric field at the edge and linear-logarithmic behavior of the tangential surface magnetic field at the edge, are shown to be consistent with the rigorous expansions. Continuation of the expansions when the wedge angle is a rational multiple of pi is shown to involve logarithmic terms. Simpler expansions, when a complex rotation of the radial coordinate is performed, are also given.

ISSN:0920-5071    

DOI:10.1163/156939395X00325

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The mean polarimetric behavior of the sea surface, on a time-averaged measurement, can be described by its averaged Mueller matrix. A method for the calculation of this matrix has already been proposed: it consists of an extension of the small perturbations technique to the vectorial case, from a two-scale sea surface model. In this article a backscattering model is shown, which is representative of a single instantaneous measurement instead of a time-average of measurements. For this purpose, the polarimetric response is characterized by the sea surface "polarization fork," described by the five Euler parameters. A minimal polarimetric descriptor is defined, the Euler vector, characterizing a "frozen" sea state, and whose components are the averaged values of the Euler parameters. The main interest of such a polarimetric signature of the sea surface is that the component of this new descriptor can be linked with the observation parameters (incidence of the illumination, azimuthal direction of the observation with respect to the wind direction, speed of the wind), in other words with the physical characteristics of the ocean surface.

ISSN:0920-5071    

DOI:10.1163/156939395X00334

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The picture of the electromagnetic field evolution along coupled waveguides in terms of the modes of the isolated primary waveguides and of supermodes of the overall coupler, is critically refined. A transformation matrix method, applied to a supermode set, enables us to express the electromagnetic field in a directional coupler by means of the modes of the isolated waveguides. A vectorial space is associated with the set of solutions of the Maxwell equations, where the orthogonal basis is given by normalized supermodes and another space in which the normalized vector basis is given by the normalized modes. Among the representations of two-coordinate systems, there is an angular rotation that does not maintain the orthogonality of the basis. Therefore, there are two characteristic rotation angles that allow a complete description of the light power exchange between the two guides and of the mode orthogonality. Many examples are included. Finally, a brief extension to N -coupled waveguides is reported.

ISSN:0920-5071    

DOI:10.1163/156939395X00343

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

An algorithm for the determination of the radiation pattern of a radiating source from phaseless measurements over two planes is developed in detail. A rather extensive assessment of its performances with respect to positioning errors and noise uncertainties is included. Moreover, comparisons with experimental data for a low sidelobe antenna demonstrate the wide applicability of the proposed technique, which is now mature for use both at frequencies where phase information cannot be reliably detected and at lower frequencies. The full exploitation of this new concept in near field techniques will allow a drastic reduction of the cost of the whole facility, since many specification parameters can be relaxed without affecting the precision of the measurement set-up.

ISSN:0920-5071    

DOI:10.1163/156939395X00352

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

ISSN:0920-5071    

DOI:10.1163/156939395X00361

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

ISSN:0920-5071    

DOI:10.1163/156939395X00370

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

ISSN:0920-5071    

DOI:10.1163/156939395X00389

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor