Generalized RCS and Near-Field Electromagnetical Scattering Modeling
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A definition of generalized radar scatter section(RCS) which was independent of antenna was presented based on the superposition principle of electromagnetic field in this paper.Besides the vertical and horizontal polarization,the symmetric polarization was supposed to be a third near-field polarization scattering characteristic,and more near-field polarized RCS of metal slab were calculated.According to the generalized RCS definition,a more efficient method that was decompose-compose method was given out,for which the incident field was decomposed into inhomogeneous spherical wave which radiated by electric or magnetic dipole antenna,all of the dipole antenna's scattering were composed as the final received field.The near field of a metal slab was computed by antenna pattern approximation and the decompose-compose method.The results proved the necessity of decompose-compose method in near-field case.Keywords:
Radar cross-section
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A method for computing the resonant region scattering by slender axisymmetric objects with arbitrary surface impedance is outlined. This method employs matching of the electric and magnetic fields on axis. Results obtained by this method have been used to generate contour maps of radar cross section (RCS) as a function of frequency and aspect. Maps for three conducting cones and a cone-spheroid covering the diameter-to-wavelength range of 0.05 to 0.70 are shown. The relationship of the high and low frequency asymptotic behavior to the mapped results is discussed. Computed and measured RCS patterns are compared.
Radar cross-section
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In this paper, a calculation method of the jet engine inlet on radar cross section (RCS) is introduced by means of mode superposition on the basis of the traditional waveguide mode theory. The key of this method is to separate a complex terminal into some simple terminals, and to calculate separately the waveguide mode reflectance and polarization scattering matrix of each simple terminal. Then, RCS of a complex inlet can be calculated by the mode superposition of reflectance and polarization scattering matrixes. The advantage of the method is that a complex mode can be easily piled up by many simple modes and various inlet modes can be superposed conveniently.
Radar cross-section
Mode (computer interface)
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In order to study the near-field target characteristic of the radio fuse, an accurate near-field echo characteristics modeling algorithm based on Physical optics (PO) and physical theory of diffraction (PTD) and shooting and bouncing rays (SBR) methods is proposed to calculate the echo characteristics of fuse, including echo power and echo signal and RCS. This method fully considers the characteristics of near-field, such as the influence of antenna pattern, spherical wave irradiation, distance, polarization and so on. The main research work in this paper involves the followings: (1) Firstly, the expression of near-field irradiation field is presented as spherical wave propagation mode, which takes into count the influence of the near-field distance and spherical wave irradiation. (2) Establishing the system coordinate of antenna and the system coordinate of antenna local polarization, and then define the directivity function of near-field antenna to characterize the antenna pattern, local irradiation and near-field polarization conversion characteristics. (3) Introducing near-field polarization scattering matrix to unify the scattering characteristic components of different scattering mechanisms, and then calculate the echo characteristic of radio fuse by integrating those of the geometrical elements which are illuminated by antenna beam during missile target encounter. In addition, the proposed theoretical model in this paper is calibrated by actually-measured data. And the emulation results are with a good agreement with measured results. Finally, we consider a simplified missile model, and compute its echo characteristics under different antenna pattern and different distance and different polarization. The results show that scattering peaks correspond to the points of the wings of the missile. In addition, the results change obviously when using different antenna pattern. At the same time, the results are different under the different distance. Numerical results prove the proposed method high efficiency and preciseness. It would be especially valuable in engineering application.
Physical optics
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Radar cross-section
Physical optics
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An analysis of the effects of the antenna radiation pattern on estimates of the differential scattering coefficient (/spl sigmasup 0/) of rough surfaces is performed. Kirchhoff's approximation is used to describe rough surface scattering. A comparison between normalized /spl sigmasup 0/ derived in the cases of plane wave illumination (pencil beam antenna) and spherical wave illumination (generalized Gaussian beam antenna) is made. Sensitivity of the differential scattering coefficient with regards to the antenna radiation pattern is studied.< >
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Shooting and Bouncing Ray Method (SBR) combined with the Physical Diffraction Theory (PTD) was adopted to calculate the near-fields composite scattering between target and sea surface. The radiation field of the horn antenna was simulated and used as the incident wave. The influence of the distance between composite model and antenna, wind speed as well as the antenna beam on the near-field scattering characteristic was studied from near-field RCS. The calculated results show that the characteristics of the near field are more complex, the incident wave cannot be regarded as plane wave and the effects of the antenna pattern on near-field scattering cannot be ignored.
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Near-field scattering measurements research has become popular in recent period. Time domain planar near field scattering measurements can obtain the wideband scattering data in one measurement. This paper concerns simulation of time domain near field scattering measurements. This time domain measuring method is based on plane wave spectrum formulas. The near-field scattering measurement data are transformed to far-field scattering data such as Radar Cross Section (RCS). The formulas of this method, derivation of the formulas, the simulation method, the simulation results and analysis will be presented in this paper.
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The method of moments in conjunction with the method of relative phase is used to determine the radar cross section (RCS) response from a collection of planar wire-type elements which may conform to a cylindrical surface. The method of moments is used to define the scattering matrices of each wire-type element which completely describes the object in 4 pi -space within a given bandwidth. The individual element responses are then combined using the relative phase differences, with the assumption that the phase-center is at the center of the wire object. Correlation is good between relative phase approximation predictions, moment-method predictions, and RCS measurements for element-to-element spacings greater than one wavelength. Two cases were investigated between 6-18 GHz for vertical polarization: (1) a loosely spaced arrangement of 4 star elements of the same size; and (2) a closely spaced arrangement of 17 star elements of different sizes.< >
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Radar cross-section
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Center (category theory)
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We quantify the discrepancy between radar cross section (RCS) of long cylindrical scatterers and RCS of infinite structure with the same cross-section. The scatterers are made of perfect electric conductor and are excited so that vector of electric field is perpendicular to the cylinder axis. We use method of moments (MoM) for numerical analysis. The results show that if the cylinder is longer than 10 wavelengths, the 3-D RCS can be predicted with mean squared discrepancy less than 1 dB using 2-D analysis.
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Time domain planar near field scattering measurements can obtain wideband scattering data in one measurement. Time domain measuring method is based on plane wave spectrum formulas. This paper concerns simulation of time domain planar near field scattering measurements in time domain. The near-field scattering measurement data are transformed to far-field scattering data such as Radar Cross Section (RCS). The formulas of this method, derivation of the formulas, the simulation method, correction factor in time domain transformation, the simulation results and analysis are presented in this paper.
Radar cross-section
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