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1.
Kumar S.J. Chakraborty A. Das B.N. 《Antennas and Propagation, IEEE Transactions on》1991,39(6):851-854
A method of scanning a one-dimensional shaped pattern generated by a tilted circular planar array of nonisotropic elements is presented. A method of synthesis of phase function for a desired cosecant pattern and specified amplitude distribution for excitation of the elements of the array is presented. The phase distribution required in the perpendicular direction for retaining the beam shape in the scanned plane is determined. Computed results on the phase distribution and radiation pattern are presented. The appropriate correction is applied to get a better agreement between the realized and desired patterns in this scanned position of the beam 相似文献
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The generation of shaped beams from circular aperture is reported by Chakraborty et al. However there is no data available on the shaped beams from circular arrays. As the circular arrays exist in practice, they are designed to produce shaped beams. A new amplitude distribution is proposed and the concept of energy relations and stationary phase are used to design the optimized phase distribution. Introducing the phase function so obtained the patterns are realized and compared with those of specified. The cosecant beams are generated from small and large circular arrays. 相似文献
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椭圆对称奇异空心光束通过硬边光阑的传输特性 总被引:1,自引:4,他引:1
通过将圆孔光阑函数展开为有限复高斯函数和的方法,利用惠更斯-菲涅耳衍射积分推导出了椭圆对称奇异空心光束通过具有圆孔光阑的近轴ABCD光学系统的传输近似解析公式,并对椭圆对称奇异空心光束在自由空间中通过不同孔径下的硬边光阑的传输特性进行了数值模拟研究。结果表明:自由空间中的近轴光学系统无论在近场还是远场,椭圆对称奇异空心光束的衍射光强分布都与光阑大小有很大的关系。该研究方法对椭圆对称奇异空心光束通过具有圆孔光阑的传输和变换的研究非常有益。 相似文献
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Wright D.B. Lee R. Dudley D.G. Casey K.F. 《Electromagnetic Compatibility, IEEE Transactions on》1992,34(2):133-136
The problem of a wire penetrating a circular aperture in an infinite conducting screen and entering a circular cylindrical cavity is considered. An approximate method is developed for evaluating the fields outside the cavity for observation points located far from the aperture. Results are presented in the frequency domain which compare this far-field approximation to the method of moments solution. The presence of interior resonance features in the exterior fields is discussed 相似文献
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The diffraction of a normally incident plane electromagnetic wave with wave numberk by a circular aperture of radiusa in a unidirectionally conducting plane screen of zero thickness and infinite extent is considered. In the limit of largeka , the ratio of the transmission cross section to the geometrical optics valuepi a^{2} , is found up to the order(ka)^{-3/2} . 相似文献
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The problem of determining the current excited on a circular loop which is placed opposite a small circular aperture in a conducting screen, on which an electromagnetic plane wave is incident, is considered. It is shown that this geometry is unusual in that the resulting integrodifferential equation can be reduced to an explicit expression for the current. The total rate of electromagnetic energy flow in the radiation zone is also calculated, as is the angular dependence of the energy flux. Sample results are presented which demonstrate the resonant behavior of the system when the wavelength of the incident wave is equal to the loop circumference. 相似文献
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Le-Wei Li Mook-Seng Leong Pang-Shyan Kooi Tat-Soon Yeo You-Lin Qiu 《Antennas and Propagation, IEEE Transactions on》1998,46(5):664-671
This paper presents a full-wave analysis of the radiation characteristics of an aperture antenna that is flush-mounted on a ground plane and fed by a circular waveguide supporting the dominant TE11 mode. The antenna is covered by a dielectric hemispherical chiral radome. Huygen's equivalence principle and the image theory are utilized to simplify the problem. The magnetic dyadic Green's function for the three-layered geometry is formulated and applied to analyze the radiated electromagnetic fields outside the chiral radome. Both the exact and approximate expressions of electric fields valid for the Fresnel and Fraunhofer zones are obtained using the spherical vector wave functions and their approximations in the far zone. Various chiral materials are assumed and computations of antenna parameters are carried out. The effects of the dielectric chiral radome on the radiation power patterns, sidelobe levels, and 3-dB beamwidths are also discussed numerically 相似文献
10.
《Electronics letters》1969,5(20):494-495
Radiation patterns containing multiple beams may be generated by manipulating merely the phase on an aperture, leaving the amplitude distribution undisturbed. The relative phases between the various beams may be adjusted for a best approximation. 相似文献
11.
Tables of the gain-area product of a circular aperture are given and explained. Particular attention is given to the realization of maximum gain over a given area with no constraints on aperture size, but with a simple in-phase aperture distribution; and with a given aperture size, using the same class of illumination function 相似文献
12.
We investigate circular sector and annular sector dielectric resonator antenna (DRA) geometries. The advantage these geometries offer, compared to conventional circular cylindrical DRAs are significant reductions in volume, making them potential candidates for use in compact applications such as mobile communication handsets. Approximate theory, simulation, and experimental results are provided to support the findings. In particular, a sector DRA is demonstrated to have 75% less volume than a conventional cylindrical DRA, with the same resonant frequency. The DRA volume minimization for compact antenna design is also discussed and a design is proposed and tested for a mobile telephone handset suitable for the DCS1800 system 相似文献
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The three-dimensional diffraction of a scalar plane wave through a circular aperture in an infinite plane screen is analyzed and numerically computed for the case of normal incidence. A modified Babinet's principle is formulated, and this is used to find the diffraction of sound by an acoustically soft circular disk. The spheroidal wave functions are described and applied to the diffraction theory. Numerical values of the rigorous diffraction functions are computed, and these are compared to the approximation obtained by the Huygen-Kirchhoff formulation. 相似文献
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The electromagnetic scattering behavior of a perfectly conducting, infinitesimally thin, spherical shell with a circular aperture is studied. A time-harmonic plane wave is symmetrically incident upon the aperture. The problem is formulated in terms of theE -field integral equation. This produces two coupled integral equations for the tangential components of the currents on the scatterer surface. The equations are cast into matrix form by application of the method of moments, and expressions for the matrix elements are derived. Calculated values of the surface currents and radar cross sections, not previously available in the open literature, are presented and discussed for several cases of interest. 相似文献
16.
The Hankel transform is applied to express the scattered potential in the spectral domain and the boundary conditions are enforced to obtain simultaneous equations for the transmitted potential inside the thick conducting plane. The simultaneous equations are solved to represent the transmitted and scattered potentials in series forms. Numerical computations are performed to illustrate the behavior of polarizability in terms of the aperture size. The numerical comparisons to other available data show excellent agreement. The presented series solution is fast convergent so that it is very efficient for numerical computation 相似文献
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Analytical bounds on the characteristics of beams generated by an arbitrary pulse-driven array are derived and supported with numerical calculations. These bounds extend the meaning of near-field distances or diffraction lengths to the situation where the array driving functions can be broad-bandwidth signals. Particular attention is given to transmitting and receiving array systems which consist of elements that are not large in comparison to the shortest wavelength of significance contained in the signals driving them. Their output signals constitute higher-order beams whose coherence properties are degraded more slowly by diffraction than lower-order beams. It is shown that for certain measures of performance involving these beam characteristics, a localized wave pulse-driven array can outperform similar continuous-wave-driven arrays. An array with independent addressable elements is required to realize these localized wave effects. The enhanced localization effects are intimately coupled to the proper spatial distribution of broad-bandwidth signals driving the array 相似文献
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圆孔衍射成像的光子学诠释 总被引:1,自引:0,他引:1
用量子力学中关于光的粒子性观点,采用概率波对圆孔衍射成像过程进行了讨论。所得到的结论与采用光的波动性观点的惠更斯一菲涅耳原理及Fourier变换方法相同。通过分析,使我们进一步加深了对光的粒子性层面的认识。 相似文献