摘要:

The circular polarization covariance matrix is a convenient method for expressing partially polarized response data with respect to a circularly polarized basis. However, little concerning either the properties of the circular polarization covariance matrix or methods for transforming data expressed in this format has been previously reported in the literature. Here we show (1) how to recover both the diagonal and off-diagonal elements of the circular polarization covariance matrix from response data stored in either Stokes matrix or linear polarization covariance matrix format, (2) how the contribution of physical scattering mechanisms such as odd-bounce, even-bounce, and diffuse or volume scattering are expressed in circular polarization covariance matrix format, and (3) the form of the response after rotation of the target about the radar line-of-sight. Next, we derive the constraints on the matrix elements (and thereby determine the dimensionality of the response) when a target exhibits reflection, rotation, azimuthal, or centrical symmetry. Because the circular polarimetric rotation operator has a particularly simple form, referring the polarization covariance matrix to a circularly polarized basis rather than a linearly polarized basis simplifies the formulation considerably. In many applications, circular polarimetric features are synthesized from data collected using a linear polarization diversity radar. We show that residual amplitude and phase imbalance between channels under a linear polarized basis transforms to cross-talk under the circularly polarized basis.

ISSN:0920-5071    

DOI:10.1163/156939397X00936

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The phase-space beam summation is a general analytical framework for local analysis and modeling of radiation from extended source distributions. In this formulation the field is expressed as a superposition of beam propagators that emanate from all points in the source domain and in all directions. The theory is presented here for both time-harmonic and time-dependent fields: in the later case, the propagators are pulsed-beams (PB). The phase-space spectrum of beam propagators is matched locally to the source distribution via local spectral transforms: a local Fourier transform for time-harmonic fields and a "local Radon transform" for time-dependent fields. These transforms extract the local radiation properties of the source distributions and thus provide a priori localized field representations. Some of these basic concepts have been introduced previously for two-dimensional configurations. The present paper extends the theory to three dimensions, derives the operative expressions for the transforms and discusses additional phenomena due to the three dimensionality. Special emphasis is placed on numerical implementation and on choosing a numerically converging space-time window. It is found that the twice differentiated Gaussian-δ window is both properly converging and provides a convenient propagator that can readily be tracked in complicated inhomogeneous medium.

ISSN:0920-5071    

DOI:10.1163/156939397X00945

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

In this paper we generalize the local spectral expansion method (previously developed for perfectly conducting rough surfaces) to the scattering from dielectric-dielectric interfaces rough in one dimension. The method for perfectly conducting surfaces is recovered from the present formulation in the limit when one of the dielectric constants increases to infinity. We obtain the first order approximation using the tangent plane approximation. It is shown analytically that the present approximation reduces to first order perturbation theory in the appropriate limit. On the other hand, since the only approximation in our formulation is the tangent plane approximation, the present results are expected a priori to coincide with the Kirchhoff approximation when this is accurate. A numerical comparison for Gaussian random rough surfaces with other first order theories is presented.

ISSN:0920-5071    

DOI:10.1163/156939397X00954

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Anopen boundary is an unclosed surface element such as a disk, a hollow pipe of finite length, a hemisphere, and a sum of such surface elements. In this paper, on the basis of the author's rigorous mathematical theory, general algorithms to solve electromagnetic scattering by a metallic open boundary, and also by a non-metallic open boundary, are given, which enable us to solve various important problems in the study of high frequency devices such as antenna, leaky waveguide, grating, etc.

ISSN:0920-5071    

DOI:10.1163/156939397X00963

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Datato corroborate the analysis presented in a companion paper for an axially-directed antenna exciting a conducting tube are presented. We present a detailed description of the design and construction of the apparatus and of the measurements performed to obtain data. Comparisons of measured and computed driving-point admittance, normalized charge and current on the tube wall, and normalized current and charge on the antenna are presented. It is found that the results from theory and experiment are in excellent agreement.

ISSN:0920-5071    

DOI:10.1163/156939397X00972

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

A planar antenna comprised of parallel feed waveguide circuit and sub-arrays of four aperture elements have been proposed. First, we describe a fundamental concept of planar antenna employing parallel feed waveguide. Next, a parallel feed circuit using rectangular waveguide, a subarray with four aperture elements, new T-junction which is made by casting in one body and L-bend is designed, and characteristics of the planar antenna is investigated experimentally. The antenna, proposed here, has the feature of a good aperture efficiency, broadband, high heat-resistance and small size. The aperture efficiency is over 90% in frequency ratio bandwidth of 5.8% and is over 80% in frequency ratio bandwidth of 11.0%.

ISSN:0920-5071    

DOI:10.1163/156939397X00981

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor