1,721,269 research outputs found
HIGH-FREQUENCY ANALYSIS OF EM SCATTERING FROM A CONDUCTING SPHERE COATED WITH A COMPOSITE-MATERIAL
No full textThe asymptotic high-frequency solution for the scattered field produced by a plane wave incident on a perfectly conducting sphere coated with a thin composite material is considered. In the shadow region, the high-frequency scattered field is entirely associated with the usual creeping-wave diffraction. In the lit region, the scattered field can be expressed as a sum of geometrical optics (GO) and creeping-wave diffraction terms. The field in the caustic regions where the ray solution fails is excluded in this study. The appropriate formula for each term is derived and the result is presented in a form suitable for computation. Numerical results of the bistatic scattering patterns of the coated sphere show excellent agreement with the rigorous eigenfunction solutions.X116sciescopu
RCS PREDICTION ACCELERATION AND REDUCTION OF TABLE SIZE FOR THE ANGULAR DIVISION ALGORITHM
No full textThe method of shooting and bouncing rays has been successfully used to predict the radar cross section (RCS) of electrically large and complex target models. However, this method has a demerit that its prediction time is very long when targets are electrically large and complex. Therefore, we propose the hybrid angular division algorithm (HADA) that accelerates prediction of RCS for electrically large and complex target models. This method improves the angular division algorithm (ADA), by incorporating a more efficient way of dealing with patches on planes that meet at angles between (90 - alpha)degrees and (90 + alpha)degrees, where a is the so-called 'critical angle'. A critical angle delimits a range of angles in which the effects of double reflections between patches are dominant. We perform ADA for a patch-pair which satisfies the condition of critical angles. We used the proposed algorithm to calculate the RCS of a model battleship; compared to ADA, HADA reduces prediction time by >= 30% without loss of accuracy.X1111sciescopu
One-dimensional scattering centre extraction for efficient radar target classification
No full textA technique is presented to extract one-dimensional scattering centres of a complex radar target. To maintain super-resolvability, estimation accuracy and robust detection of scattering centres, the model-based technique, and the FFT-based technique, are combined in an efficient manner to take advantages of both techniques. The performance of the proposed algorithm is examined through Monte-Carlo simulations and classification experiments. It is shown that the proposed technique can be employed in the feature extraction stage for efficient radar target classification.X1122sciescopu
Two-dimensional scattering center extraction based on multiple elastic modules network
No full textThe concept of scattering centers on a target is commonly used for radar signature modeling and data compression, as well as target recognition. In particular, two-dimensional (2-D) scattering centers are useful features in automatic target recognition, which uses a synthetic aperture radar system, because they are directly related to physical scattering mechanisms and also have small dimensionality. In this paper, we propose a new technique for estimating 2-D scattering centers using radar data in the frequency-aspect domain. The technique first estimates one-dimensional scattering centers at several aspects, and the multiple elastic modules network optimization is exploited to find 2-D locations and amplitudes of the target's scattering centers. Experimental results illustrate that the proposed method is efficient not only for estimating 2-D scattering centers on the target but also in computation.X118sciescopu
Improvement of natural frequency extraction in frequency domain
No full textNatural Frequency extraction in the frequency domain using measured frequency responses is an ill-conditioned problem. A method is proposed to improve the accuracy of the previously extracted :natural frequencies. It is shown from results that the method cin improve the accuracy of the natural frequencies extracted from synthetic and measured frequency response samples.X11sciescopu
Generalized early-time/late-time evolutionary programming-based clean
No full textA novel method, which is called generalized early-time/late-time evolutionary programming (EP)-based CLEAN algorithm, is proposed for simultaneous extraction of the scattering centers and natural resonance frequencies of a radar target. This algorithm uses a duality between the temporal late-time response and spectral early-time response. (c) 2007 Wiley Periodicals, Inc.X110sciescopu
Radar target recognition based on late time representation: Closed-form expression for criterion
No full textIn the previous paper, we have defined the normalized estimation error and presented the radar target recognition scheme in frequency domain. A time-domain version of the previous paper is considered and a closed-form expression for the defined normalized estimation error in terms of Z-plane natural frequencies and transient response is derived. Evaluation of the closed-form expression of the normalized estimation error is shown in the numerical results, where it is shown that the performance of the radar target recognition scheme improves with an increase of the number of the natural frequencies and with an increase of signal-to-noise ratio. Furthermore, the mean and the variance of the square of the numerator of the normalized estimation error are obtained, and the validity of the statistics is shown using the numerical results.X118sciescopu
An asymptotic solution of EM backscattering from a conducting sphere coated with a composite material
No full textAn asymptotic high frequency solution. for the electromagnetic (EM) backscattered field produced by a plane wave incident on a perfectly conducting sphere coated with A thin composite material is derived in this paper. For the formulation of the incident and the reflected field the, characteristics of the wave transformation and the line integral via the stationary phase method were applied, respectively, and the obtained results are cast in the ordinary ray formats of a geometrical optics field. Based on the Watson transform technique, the diffracted field is also formulated from the residue series solution of the problem and presented in a form suitable for the numerical calculation. The numerical results obtained from the derived asymptotic solution show excellent agreement with those from the rigorous eigenfunction solution.X113sciescopu
Design of wave absorber for small conducting sphere
No full textAn electromagnetic wave absorber for a small sized conducting sphere is designed by applying the Newton-Raphson method to the eigenfunction series solution for a coated conducting sphere. The parameters for the perfect absorbing condition are the constitutive parameters and the thickness of coating for a given radius of conducting sphere. The wave absorber designed by this method exhibits a superior absorption performance to that designed using flat plate absorber theory.X112sciescopu
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