共查询到20条相似文献,搜索用时 15 毫秒
1.
Yi Li 《电子科学学刊(英文版)》1987,4(1):11-19
Based on the work developed by R. Mittra and others (1979), this paper carries on the Jacobi-Bessel series method to compute
far-field patterns of a paraboloid reflector antenna with elliptical aperture by means of recursion of the series coefficients
p
B
m
n
about indicesp andm respectively and enhances the computational efficiency to a great extent. 相似文献
2.
Although many reflector antennas possess circular projected apertures, there are recent satellite and ground antenna applications for which it is desirable to employ reflectors with elliptical apertures. Here a modification of the Jacobi-Bessel expansion is presented for the diffraction analysis of reflectors with elliptical apertures. A comparative study is also performed between this modified Jacobi-Bessel algorithm and the one which uses the Jacobi-Bessel expansion over a circumscribing circular region. Numerical results are presented for offset reflectors with elliptical and circular apertures and the improved convergence properties of the modified algorithm are highlighted. 相似文献
3.
提出了一种新型的多层介质结构的反射面天线,反射平面上所需要的相位补偿通过选择合适的介质厚度来实现,使用几个多层圆形介质即可满足条件。与传统的高增益天线相比,该结构设计简单,加工方便。验证了几种不同层数的结构和一个等口径的抛物面反射面天线。加工并测试了一个采用Vivaldi做馈源的4层结构的反射面天线。仿真和测试结果均表明该天线具有良好性能。 相似文献
4.
Resistive sheets with electrically adjustable conductivity are used to modify scattering from portions of a reflector surface in order to adaptively place nulls in the far-field patterns of two- and three-dimensional reflector antennas 相似文献
5.
A technique, whereby the radiation patterns of large size reflector antennas can be approximated by computers using a moment method without excessive computer time or memory, is described. Computational time increases only linearly with antenna size. There is no limit on the minimum reflector size (a single wire reflector can be analyzed). An example is discussed showing the radiation patterns of a truncated parabolic reflector excited by feeds displaced from the parabola focus. 相似文献
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7.
The letter describes the application of fast integration techniques, based on the FFT algorithm, to the evaluation of the far-field radiation integral for aperture plane, surface electric current and surface magnetic current theory. Results are presented comparing patterns derived by these three theoretical approaches. 相似文献
8.
Rahmat-Samii Y. Cramer P. Jr. Woo K. Lee S. 《Antennas and Propagation, IEEE Transactions on》1981,29(6):961-963
The radiation pattern of a feed element is approximately described by a simple function(cos theta)^{q} . For a given element spacing of the feed array, we give simple formulas for estimating the practical value ofq when the element is an open-ended rectangular waveguide, an open-ended circular waveguide, a pyramidal horn, or a cigar antenna. 相似文献
9.
Cherrette A.R. Acosta R.J. Lam P.T. Lee S.-W. 《Antennas and Propagation, IEEE Transactions on》1989,37(8):966-978
Various aspects of reflector surface distortion compensation are explored by first assuming the reflector distortion is given and then designing the compensating feed array. The sensitivity of boresight directivity to changing surface distortion parameters for fixed feed-array geometries is examined. It is found that feed array compensation is feasible only for distortions with low spatial frequency content, such as those distortions induced by thermal and gravitational effects. The optimum directivity methods for determining element excitation is found to yield slightly better values of directivity than those for the conjugate field matching (CMF) technique. However, the CFM technique has, in general, much lower sidelobe levels and lends itself to simple realization in hardware. In view of these results, distortion compensation using an array feed is concluded to be a reasonable approach to improving antenna performance for large, space-based reflector antennas that are not easily accessible for tuning and have time-dependent surface distortions 相似文献
10.
A bicollimated Gregorian reflector is structurally similar to a classical confocal Gregorian reflector, but its surfaces are shaped to have better scan capability. A geometrical optics procedure is used in designing the reflector surfaces. A three-dimensional ray tracing procedure is used in analyzing the aperture phase errors as the beam is scanned to different angles. The results show that the bicollimated configuration has about 45 percent greater angular scanning range than the equivalent confocal Gregorian reflector antenna. 相似文献
11.
A bifocal dual reflector antenna is similar to and has better scan capability than a classical Cassegrain reflector antenna. The method used in determining the reflector surfaces is a modification of a design method for the dielectric bifocal lens. Computed radiation characteristics of the bifocal reflector system are compared with those of a classical Cassegrain reflector system. The results confirm that the bifocal reflector has superior scanning performance. 相似文献
12.
应用时域有限差分一时域等效边缘电流(FDTD-TDEEC)混合法计算脉冲辐照情况下大口径抛物面天线的远区辐射场,先使用FDTD方法计算抛物面天线馈源的近场,再根据基尔霍夫面积分表达式(KSIR),求出表面上任意点的场对抛物面天线口径边缘上场的贡献,并将此贡献看作是入射脉冲,使用TD-EEC方法计算抛物面天线的远区辐射场.给出馈源为偶板子的算例,所得计算结果与EEC方法的结果符合较好.数值计算表明,抛物面口径边缘的绕射对抛物面方向图的副瓣有一定影响.该方法具有通用性,可有效分析其它类型馈源的各种电大尺寸的单反射面天线的远区辐射场,包括馈源偏焦的情况. 相似文献
13.
A simple and successful design for a variable beamwidth corner reflector antenna is presented. The gain and the -3 dB beamwidth of the antenna are predicted using the finite difference time domain (FDTD) method. The predicted results are compared with measured data and good agreement is reported 相似文献
14.
概述太赫兹技术及太赫兹天线的发展状况,重点介绍太赫兹赋形面天线技术在太赫兹准光系统、太赫兹通信系统、太赫兹成像系统等领域的应用。赋形面技术主要基于能量守恒定律和等光程原理将出射的波束转换成要求的场分布。赋形反射面能够实现标准反射面不能实现的功能。因此赋形面技术将大大拓展现有的反射面天线在太赫兹波段的应用场景,并能提高太赫兹系统的幅度和相位特性。 相似文献
15.
Johansson F.S. Josefsson L.G. Lorentzon T. 《Antennas and Propagation, IEEE Transactions on》1989,37(8):984-989
Theoretical and experimental results are presented for a frequency-scanned antenna composed of a line source and a frequency-scanned reflection grating that is shaped to a cylindrical reflector. The principle considering is to select the grating geometry such that the first higher-order diffracted wave propagates and serves as the frequency-scanned beam. An analytical solution for the cylindrical reflector geometry that gives a line focus is given. The grating structure considered consists of an array of dipoles placed over a ground plane. The design of the dipole grating for optimum blazing (i.e., for optimal power conversion from the incident wave to the diffracted wave) is discussed. For the theoretical analysis Floquet's theorem and the method of moments are used 相似文献
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17.
The Physical Optics radiation integral expressed is implemented in terms of a summation of Fourier transforms in MathCAD. The Jacobi-Bessel series has been used to evaluate the Fourier transforms. The mathematical formulation given provides a fast and accurate approach for the prediction of the far-field radiation pattern of offset-reflector antennas. The accurate and rapid numerical evaluation of the expressions obtained is demonstrated through the design of a multi-feed offset reflector. Furthermore, the formulation can be slightly modified and implemented in MathCAD for axially symmetric reflectors and other types of aperture antennas, as well. 相似文献
18.
A study of a UWB array antenna is presented, which is composed of leaf-shaped bowtie radiating elements printed on a dielectric substrate. With the use of a flat reflector, the presented antenna has unidirectional radiation characteristics and higher directivity in comparison with omnidirectional UWB antennas. In the maximum radiation direction of the proposed antenna, the actual gain of 10.3-13.3 dBi is achieved over the frequency range of 4.1-10.0 GHz (-3 dB gain bandwidth of 91%). 相似文献
19.
A design method for an offset-fed, dual reflector antenna (Cassegrain type or Gregorian type) system with an axisymmetric main reflector is presented. Geometrical optics (GO) and the geometrical theory of diffraction (GTD) are used to find the surface-current density on the main reflector. A modified Jacobi-Bessel series (JBS) method is used to find the far-field pattern for the physical optics (PO) integral. In the defocused mode of operation, a new technique is developed to find the reflection point on the subreflector corresponding to the defocused feed and a general field point on the main reflector. Two sample systems are designed. 相似文献
20.
The computer analysis of dual-offset reflector antennas fed by a circular corrugated horn, using an accurate feed model, is described. Near-field, thermal-paint, and carbon-fiber-reinforced plastic (CFRP)-structure effects are included in order to simulate a realistic design scenario and predict their impact on the radiation characteristics. The theoretical results have been verified by experiment for a near-field illuminated offset Gregory antenna 相似文献