共查询到20条相似文献,搜索用时 46 毫秒
1.
This paper presents an analytical solution for the radiation field of an axially slotted, infinite, circular cylinder which is covered with a uniform layer of an anisotropic plasma sheath. Numerical results are obtained and radiation patterns plotted for various degrees of plasma anisotropy. It is shown that the radiation pattern undergoes rapid changes for certain ranges of plasma parameters and forms well-defined, directive beams for other ranges. Curves showing the effect of the thickness of the plasma sheath on the radiation characteristics are also given. 相似文献
2.
Serebryannikov A.E. Nosich A.I. 《Antennas and Propagation, IEEE Transactions on》2005,53(4):1426-1434
A generalized model is developed to study the TE-polarized plane wave scattering by coated and uncoated slotted circular cylinders of nonzero thickness and by a filled and not filled circular cylinders with sectorial cuttings. The mathematical treatment is based on the coupled integral equations (IEs) with respect to the tangential electric field at the slot/cutting apertures. The Galerkin method with weighted Gegenbauer polynomials as basis functions is used to convert IEs to a set of linear algebraic equations. Numerical simulations of the radar cross section (RCS) are carried out in the case of single slot/cutting in order to reveal the effect of thickness. Potentials of three approximations to the field in the slot/cutting domain are studied. Their use enables one to substantially accelerate the RCS calculations. 相似文献
3.
TM scattering from a hollow, slotted, circular cylinder with thickness is investigated. The mode-matching technique (MMT) is used to express the scattered and guided fields in the angular spectral domain in terms of the radial waveguide mode. The boundary conditions are enforced on the conducting surface and the slot to obtain simultaneous equations. The simultaneous equations are solved to represent the fields in an analytic series form. The computed results are in very good agreement with other data. The numerical computations are performed to illustrate scattering behavior in terms of cylindrical geometry, incident angle, and frequency 相似文献
4.
The shrouding of an elementary cylinder antenna by a concentric perfectly conducting axially slotted shell is considered. The problem is reduced to a Fredholm integral equation of the first kind, which is solved for the case of a narrow shell slot. The solution indicates that the slotted shell inhibits the antenna radiation only for certain parameter combinations; for most others, the radiation remains the same, and for some it is enhanced. 相似文献
5.
The equatorial radiation pattern of a parallel-plate TEM mode axial slot on an infinite cylinder of elliptical cross section is computed using wedge-diffraction and creeping-wave theory. The wedge-diffracted fields are obtained by the diffraction interaction from a set of infinite wedges approximating the parallel-plate-cylinder geometry. Surface-wave propagation on curved bodies commonly used in scattering is employed for the creeping-wave contribution. The total field in the lit region is approximated using superposition of wedge-diffracted and creeping-wave fields and in the shadow region solely by creeping-wave fields. The computed patterns are compared with experimental results since boundary-value solutions are not readily available. Good agreement between theory and experiment is indicated. 相似文献
6.
Scattering from dielectric-coated impedance elliptic cylinder 总被引:2,自引:0,他引:2
The scattering properties of an impedance elliptic cylinder coated with a homogeneous material are investigated analytically. The method of separation of variables together with the impedance boundary condition (IBC) are used to determine the field distributions in each region for both the TM and TE excitations. The technique can be easily extended to handle any number of layers. The behavior of the scattered field in the far zone is illustrated with numerical results for different core and coating material types, axial ratio, and electrical sizes 相似文献
7.
Backscattering by loaded and unloaded dihedral corners 总被引:5,自引:0,他引:5
Corona P. Ferrara G. Gennarelli C. 《Antennas and Propagation, IEEE Transactions on》1987,35(10):1148-1153
An accurate mathematical model for the backscattering from a loaded dihedral corner has been developed. Such a model employs a generalization of physical optics (PO) to loaded surfaces which takes into account the lighting of each face by the rays diffracted by the edge of the other one. The inclusion of the currents due to such diffracted fields in the PO current distribution has been found relevant in order to improve the accuracy of the solution. Moreover the solution is uniform with respect to the loading impedance; as it coincides with the previously obtained solution for the perfectly conducting case, when the loading impedance approaches zero. 相似文献
8.
The wedge-diffraction theory in combination with the creeping wave theory is used to compute the radiation pattern of an axial slot on a circular conducting cylinder. The slot is excited by a parallel-plate waveguide operating in the TEM-mode. The total field in the "lit" region is obtained by the superposition of the wedge-diffracted and creeping wave fields. The total field in the "shadow" region is obtained solely from the creeping wave contribution. 相似文献
9.
A theoretical study is made for obtaining the pulse radiated from an impedance loaded dipole. Numerical results are presented for an antenna that is slowly charged and suddenly shorted at the terminals. The impedance loadings are chosen as those on an existing antenna located at Sandia Laboratory, Albuquerque, N. Mex. 相似文献
10.
Measured center element gain patterns, voltage standing-wave ratio (VSWR), and mutual coupling for passively terminated arrays of horizontally polarized loop-fed slotted cylinder antennas over a ground plane are given. A seven-element hexagonal array is investigated in detail. The element gain pattern is shown to have a null at broadside with omnidirectional coverage along a constant cone angle from broadside. Maximum gain occurs close to50deg from broadside which provides for wide-angle phased array scanning capability. The antennas are also configured in a linear array geometry, to investigate mutual coupling effects on the element gain pattern as the number of elements is varied. The element gain pattern is shown to converge for a relatively few number of elements and there is no indication of undesired blind spots. 相似文献
11.
T. C. TONG 《International Journal of Electronics》2013,100(6):767-772
The two-dimensional problems of an E-polarized wave incident on a slightly rough perfectly conducting cylinder and also a cylinder with an impedance boundary condition are considered. Numerical results for a. rectangular cylinder are presented to illustrate the similarities between thesis two cases. 相似文献
12.
Near-field analysis and coupling of a perfectly conducting slotted elliptic cylinder excited by an electric line source placed inside or outside the cylinder is considered. The solution can be easily extended to account for a z-polarized incident plane wave excitation. The separation of variables technique is used to express external and internal fields in terms of Mathieu and modified Mathieu functions with unknown expansion coefficients. The problem is then reduced to an integral equation in terms of the aperture field. The solution of the integral equation is carried out by expressing the aperture field in terms of a Fourier series expansion with unknown coefficients. Then Galerkin's technique is introduced to solve for the unknown aperture field coefficients. Results for the penetrated and near fields are given in terms of different parameters such as location and type of the excitation, aperture width, cylindrical axial ratio, and the loading of the cylinder 相似文献
13.
14.
Yi-Jun He Quanrang Yang 《Electromagnetic Compatibility, IEEE Transactions on》1994,36(2):147-149
The scattering of an electromagnetic missile (EMM) with energy decreasing as r-4 from a perfectly conducting irregular surface is analyzed. The mean scattered power is derived. It is shown that the rate of the average energy decay for the backscattering field far from the irregular surface is proportional to r-4, which is the same as that for plate scattering 相似文献
15.
A novel type of pyramidal absorber is presented. This absorber utilises a combination of impedance loading and an exponential stepped permittivity profile. The new design offers significant improvement in the absorber's low frequency performance when compared with existing pyramidal absorbers. Optimisation of the design parameters has been carried out to maximise the absorber's bandwidth at -40 dB reflectivity. 相似文献
16.
The scattering of an electromagnetic plane wave from a cylinder with circular cross-section loaded periodically with groups of metallic annular rings along the longitudinal axes is analysed. The incident plane wave is arbitrarily polarised and impinges on the cylinder at an oblique incidence 相似文献
17.
Swift C. Gooderum P. Castellow S. Jr. 《Antennas and Propagation, IEEE Transactions on》1969,17(5):598-605
A discharge tube and facility for measuring the equatorial patterns of an axial slot antenna on a plasma covered cylinder are described. A Langmuir probe survey of the tube is made to determine axial, radial, and azimuthal variations of electron density. Experimental patterns made at various concentrations of electron density are obtained which closely resemble theoretical patterns fornu/omega cong 0.16 . Absorption and dipole resonance predicted to occur at (omega_{p}/omega)^{2} simeq 1 and 1.8, respectively, are experimentally observed. 相似文献
18.
The evaluation of the transverse electric (TE) surface field on an impedance boundary circular cylinder, excited by a magnetic current on the same surface is discussed. The source is of infinite axial extent. The integral which describes the field due to a single surface ray is evaluated numerically and asymptotically. The results compare well with each other as well as with the eigenfunction solution. The surface ray field has a uniform representation in the sense that it remains valid in the immediate vicinity of the infinitesimal source as well as in the deep shadow region. A comparison is made with a flat impedance plane to indicate the influence of curvature on the surface field. 相似文献
19.
Strips made of a resistive sheet material have lower backscattering cross sections than the corresponding perfectly conducting strips, and this is true in particular when the illumination is edge-on with the electric vector parallel to the edge. Attention is focused on this case. Using the moment method applied to an appropriate integral equation, data are obtained for the surface field and backscattered far field of a resistive strip for a variety of strip widthsw and uniform resistancesR . The front- and rear-edge contributions to the far field are then extracted. It is shown that for strips whose width is greater than about a half-wavelength the former is the same as for a half-plane having the same resistance, whereas the latter is proportional to the square of the current at that point on the half-plane corresponding to the rear edge of the strip. The implications of these results on the selection of a strip resistance for low backscattering are discussed. 相似文献
20.
Chang-Won Lee Joong-Pyo Kim 《Antennas and Propagation, IEEE Transactions on》2003,51(6):1321-1330
The radiation characteristics of a corrugation loaded dielectric coated conducting cylinder are investigated theoretically for the infinite periodic and finite structures. For the infinite periodic structure, the mode matching method is applied. The integral equation is derived for the finite structure by use of the Fourier transform and mode expansion. The influences of the corrugation width, corrugation depth, dielectric thickness, cylinder radius, and finite corrugation number on the radiation characteristics (leakage constant, phase constant, and radiation pattern) are investigated. The results of the finite periodic corrugations are compared with those of the infinite extent structure and good agreement is found. To reduce the high side lobe of the uniform periodic structure, nonuniform quasiperiodic corrugation arrays are considered. The surface wave radiated by the structure having end-fire radiation pattern is also investigated. 相似文献