摘要:

A path-integral solution is used to describe the statistical moments of wave propagating in an intermittent random medium. The theory provides a general framework, examines the effect of intermittency due to the practically Gaussian large-scale variabilities, and develops the formulation necessary for remote sensing applications. We speculated that Gaussian large-scale variability can be attributed to the terrain, canopy, swell waves, albedo distribution, cloud obscuration or gravity wave modulation. The paper concludes that although the Gaussian large-scale is the asymptotic limit for all processes at ranges that are relatively short or long compared with the large scale of the variability, higher cumulants are required to bound the result for a strong large-scale fluctuations.

ISSN:0920-5071    

DOI:10.1163/156939397X00729

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

In radar detection, the presence of clutter is an undesirable but unavoidable fact. Furthermore, clutter is highly destructive to the detection of slow-fluctuating targets, since Doppler filtering can not be adapted when clutter and targets are moving at approximately the same speed. Besides, to face improvements of countermeasure means (absorbent materials, structure geometry, etc.), the setting up of high performance detection schemes is mandatory. Radar polarimetry indicates to provide the long sought-for solution to these problems. The goal of this research is to estimate the contribution of polarimetry to radar detection by evaluating several novel polarimetric detection algorithms and by comparing them to existing coherent single channel-only approaches.

ISSN:0920-5071    

DOI:10.1163/156939397X00738

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

A rigorous full-wave analysis is employed to analyze a shielded microstrip T-junction. A method of moments technique is employed on the T-junction apertures of microstrip lines. A multi-step Green's function approach is employed to determine the integral equations related to aperture fields. In this context the Green's function of the T-junction enclosed inside a shielded microstrip is determined by applying semi-analytic techniques. The scattering parameters of the T-junction are computed for various cases and are presented for a wide range of frequencies. The importance of shielding box modes is investigated.

ISSN:0920-5071    

DOI:10.1163/156939397X00747

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

A dual series solution to the problem of Gaussian beam scattering from a semicircular channel in a conducting plane is presented. The problem is solved by the boundary value method together with the Kozaki's Gaussian beam approximate expression. Some numerical results are shown. Differences between Gaussian beam and plane wave scattering behaviors are discussed.

ISSN:0920-5071    

DOI:10.1163/156939397X00756

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

A noise Sinclair matrix statistical model of the Anechoïc Chamber measurement channel is first developed in the frequency domain, then in the time domain and finally in the holographic radar images domain. Building these models allows one to analyse the sensitivity of a common target classification tool, the Huynen parameters, for any target and then to construct a prediction model of the Huynen parameters sensitivity based on the measure of a single target Sinclair matrix [S].

ISSN:0920-5071    

DOI:10.1163/156939397X00765

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

A new description for multiscale surface roughness containing all frequencies above a minimum value has been developed. Analytic equations for autocorrelation functions are given to surfaces with Gaussian, exponential, isotropic exponential and transformed exponential multiscale surface correlations. A method for applying these autocorrelation functions to surfaces rough only in separate frequency bands is also presented. The obtained multiscale exponential autocorrelation function fits well to measured 1 m-50 m long profiles of Baltic sea ice. The surface description is also combined with the Integral Equation Method for calculating the surface backscattering coefficient and applied to Baltic sea ice. However, the validity of approximating the local incidence angles with the radar incidence angle, typically used in IEM calculations, was seriously limited by the small permittivity of ice. Reliable estimation of the field coefficients requires further investigation.

ISSN:0920-5071    

DOI:10.1163/156939397X00774

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The effectiveness of some iterative approaches to the computation of the electromagnetic scattering by nonlinear isotropic dielectric cylinders of arbitrary cross-sections is investigated in this paper. These approaches have been developed within the distorted-wave Born approximation, the classic first-order Born approximation, and the Rytov approximation. They are based on an integral equation formulation that defines an equivalent problem in which the interactions between harmonics are taken into account by coupling terms that can be made explicit, as the nonlinearity has been defined. In the case of Kerr-like nonlinearities and under the hypothesis of time-periodic transverse-magnetic incident fields, the effectiveness of these approaches is evaluated by means of several numerical simulations, concerning cylinders of different cross-sections. The results are compared with those obtained by applying an exact numerical methodology based on an optimization procedure.

ISSN:0920-5071    

DOI:10.1163/156939397X00783

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Site diversity is considered to be an effective technique to overcome severe rain attenuation in satellite communication links. In the present paper, a modification of an existing method to predict the improvement in using dual/triple site diversity techniques is proposed. The modified method assumes a more complicated but realistic model for the description of the rain height. The present results are compared with a representative set of available experimental data taken from operated links. The difference between the existing predictive results and the deduced ones after use of the modified procedure, for various geographic latitudes and climatic zones, is also examined.

ISSN:0920-5071    

DOI:10.1163/156939397X00792

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

An inverse problem for a stratified slab of a general bianisotropic medium is considered in the frequency domain. Considering obliquely impinging plane waves, imbedding equations and Green's functions equations for the reflection and transmission coefficient matrices and the internal fields are derived through the concept of wave-splitting. Two different optimization approaches, based on the imbedding method and the Green's functions method respectively, are applied to reconstruct the constitutive parameters as functions of the position using band-limited reflection and/or transmission data from different angles of illumination. Exact and explicit expressions for the gradients are derived, which result in a one order faster computation compared with numerical perturbations of the objective functionals. The reconstruction algorithm (based upon a conjugate gradient method) is tested with both clean and noisy data.

ISSN:0920-5071    

DOI:10.1163/156939397X00800

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Guided and leaky mode propagation in three-layered and five-layered c-rotated anisotropic waveguides is examined. The considered dielectric tensor configurations are the polar, longitudinal and equatorial ones. The modal characteristics of titanium diffused lithium niobate (Ti:LiNbO3) and proton exchanged lithium niobate (H:LiNbO3) waveguides are compared. The experimental results for a three layered Y-cut Ti:LiNbO3waveguide agree very well with the calculated ones.

ISSN:0920-5071    

DOI:10.1163/156939397X00819

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor