共查询到20条相似文献,搜索用时 22 毫秒
1.
This paper considers the improvement of the feeding structure of the reflector impulse radiating antenna (IRA). Full-wave analysis and measured results of the orthogonal cross-coplanar plate reflector IRA shows that the aperture fields are not uniform. The arm angle is varied as an optimization factor and it is shown that the arm angle of 70/spl deg/ has the maximum radiation efficiency. The termination load and the arm tapering effects are studied using simulation and measurement results. Furthermore, the effect of radius of circle of symmetry is studied and it is shown that a greater circle provides higher gain. A combination of transverse electromagnetic (TEM) horn antenna and the conical coplanar TEM transmission line is investigated to avoid tiny structure at the focal point and make the connection between the coaxial cable and the feeding arms more convenient. It is shown that a small triangle does not degrade the antenna performance but helps to excite the antenna by a coaxial cable. Finally a combination of the Vivaldi antenna and the coplanar transmission line is introduced to improve the antenna performance. The simulation results for the new antenna show that the antenna efficiency is improved to 45% at the frequency band between 2 GHz to 6 GHz in comparison to the 20.9% for the traditional design and 29.7% for the tapered design. The calculated far-field results of all these antennas are used to radiate a 0.5 ns impulse. The radiated impulse from the Vivaldi fed reflector IRA is 3.55, 2.41, and 2.12 dB higher than the same radiated impulses from the reflector IRA fed by a 45/spl deg/ traditional feeding arms, 70/spl deg/ traditional feeding arms, and 70/spl deg/ tapered feeding arms, respectively. 相似文献
2.
《Antennas and Propagation Magazine, IEEE》2004,46(5):81-87
This work proposes a method for feeding a balanced IRA with an unbalanced transmission line. This method is based on the current distribution on the surface of the antenna. The method of moments (MoM) simulations show that for the IRAs, there are some areas with low current density in comparison to the current density of the feeding points, almost over the entire frequency range. The coaxial cable is attached to the antenna's body all the way from the feeding point to an area of low current density, and extends out of the antenna structure at that point. This tremendously reduces the current density on the body of the coaxial cable. As a result, the current balance between two parts of the antenna is not disturbed. This method is applied to the TEM horn antenna, the reflector IRA, and the Vivaldi antenna. The TEM horn antenna was simulated using the HEMI software, and was fed by an unbalanced coaxial cable, both directly at the feeding point and using this method. This method was also applied to the reflector impulse-radiating antenna. Also, the Vivaldi antenna was fed both by considering the low-current density area and direct feeding. The E-plane far-field pattern of the new feeding method had good agreement with the result generated by the HEMI software for the balanced-fed antenna. 相似文献
3.
Legg T.H. Avery L.W. Matthews H.E. Vallee J.P. 《Antennas and Propagation, IEEE Transactions on》2004,52(1):20-25
Holographic measurements of deformations in a large antenna reflector are described. The deformations were brought about by changing elevation angle and gravitational loading. A phase-switching arrangement was used, which allowed a single, already installed and operating receiver to be shared by both the main antenna signal and a reference signal. Natural H/sub 2/O masers in our galaxy were used as signal sources, and a reference antenna was attached rigidly to the antenna under test so as to move with it. Observing techniques are described that accommodate changes in source elevation angles and antenna feed position while acquiring a data set. 相似文献
4.
Tyo J.S. Farr E.G. Schoenberg J.S.H. Bowen L.H. Altgilbers L.L. 《Antennas and Propagation, IEEE Transactions on》2004,52(7):1767-1776
The prompt off-boresight radiation from an arbitrary reflector impulse radiating antenna (IRA) is considered in both the time and frequency domains using a time-domain physical optics formalism. The theory is used to compare the performance between reflector IRAs with common transverse electromagnetic feed configurations that have been designed to maximize the boresight fields. It is found that moving the feed arms of reflector IRAs toward the vertical helps to reduce sidelobe levels, as reflector IRAs with their feed arms oriented at 60/spl deg/ from the horizontal have sidelobes that are 4-5 dB lower in the H plane and 1-2 dB lower in the E plane than more traditional reflector IRAs with feed arms oriented at 45/spl deg/. The lower sidelobes are accompanied by a higher peak gain, albeit with a wider beamwidth. There are corresponding significant differences in the time domain waveforms that result. The theory is verified by comparison with experimental data from a half IRA with feed arms at 45/spl deg/. The peak fields, pulse widths, and overall waveform shapes agree well between theory and experiment, though there are temporal asymmetries in the measured data that are not predicted by the theory. 相似文献
5.
Impulse radiating antennas (IRAs) are an emerging class of antenna that are designed to radiate extremely short electromagnetic pulses with multiple decades of instantaneous bandwidth. The most common IRAs are made with a transverse electromagnetic (TEM) transmission line feeding a paraboloidal reflector. The IRA is usually constructed so that the electrical feed point of the TEM transmission line coincides with the focal point of the paraboloid. The paraboloidal reflector converts the spherical wave emanating from the feed point into a plane wave (i.e., a spherical wave centered at -/spl infin/). In many practical cases, the feed point and focal points are not exactly aligned, producing some defocus of the reflector. In this paper, we model the case of hyperbolic defocus because of its analytic form and compare this model with experimental measurements. A hyperboloidal reflector fed from one focus converts the expanding spherical wave into a second expanding wave which appears to emanate from the second focal point of the hyperboloid (which is behind the reflector). Hyperboloidal defocus is roughly equivalent to moving the electrical feed closer to the reflector than the optical focal point. Previous theoretical results from in-focus IRAs predicted that the E- and H-plane temporal responses should be symmetric with respect to the temporal center of the response. The results shown here demonstrate that the defocusing causes these responses to become asymmetric. The new results are in better agreement with experimental measurements of IRAs and provide a physical explanation for experimental results that differ from the original theory. 相似文献
6.
The uniform geometrical theory of diffraction (UGTD) has been applied successfully to analyze the near-field patterns of a prime-focus paraboloid. In order to establish the validity of the analysis, near-field amplitude and phase patterns have been computed over the principal planes at several observation distances for a typical prime-focus paraboloid. These calculations compare very favorably with the corresponding results obtained numerically with the aid of Silver's near-field aperture integration formula. 相似文献
7.
8.
A focused aperture antenna has been realised using a (Cassegrain) convex subreflector with a spherical main reflector. The design was based on geometrical optics, and good agreement was obtained between the measured and calculated field in the focal region. 相似文献
9.
The directive gain of a parabolic reflector antenna is maximized by optimizing the feed aperture distribution. The feed aperture distribution is specified by a set ofN basis functions weighted by coefficients to be determined. This approach is different from the conventional method where, given a particular feed, the directive gain is maximized by subjecting the reflector aperture parameters to optimization. 相似文献
10.
The reflection coefficient at the feed of a paraboloidal reflector antenna covered with a paraboloidal radome is evaluated by means of the power-coupling theorem. An asymptotic value of the subsequent expression leads to a simple physical interpretation of the result. A comparison between theoretical and experimental results shows that there is a satisfactory measure of agreement between the two. 相似文献
11.
Andrieu J. Nouvet S. Bertrand V. Beillard B. Jecko B. 《Antennas and Propagation, IEEE Transactions on》2005,53(4):1254-1261
A new ultrawide-band (UWB) antenna named the "scissors antenna" has been designed specially for transient ultrawide-band applications. The scissors antenna, which is composed of conducting wires, radiates ultrashort pulses with very low dispersion. The radiation of this antenna has been characterized by a transient measurement method suitable for characterizing UWB antennas with very low dispersion. After a presentation of the scissors antenna, this measurement method is described. The last part of the paper presents a comparison between the radiation characteristics of the scissors antenna obtained by the transient measurements and those obtained by the classical harmonic measurements. 相似文献
12.
Einarsson O. Sleator F. Uslenghi P. 《Antennas and Propagation, IEEE Transactions on》1975,23(1):28-36
The synthesis of a prescribed far-field pattern by means of a radiating slot in a perfectly conducting infinite circular cylinder is considered. The narrow circumferential slot and the infinite axial slot are studied in detail. In either case, the problem is to find the distribution of the electromagnetic field in the aperture that yields a radiation pattern that is the best mean-square approximation to a given pattern, under certain constraints. Various quality factors for cylindrical modes are discussed, and a detailed comparison with the synthesis problem for a planar aperture is performed. It turns out that Rhodes' synthesis method has no equivalent in the cylindrical case, and that the best admissible mean-square approximation to a given pattern may be a very poor approximation in amplitude. However, an iteration scheme is developed in which the phase approximation is sacrificed for the sake of substantially improving the amplitude approximation. Numerical results based on such a scheme are displayed, for prescribed omnidirectional and sectoral patterns. 相似文献
13.
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
14.
Directivity optimization of a reflector antenna with cluster feeds: A closed-form solution 总被引:1,自引:0,他引:1
Lam P. Shung-Wu Lee Chang D. Lang K. 《Antennas and Propagation, IEEE Transactions on》1985,33(11):1163-1174
The directivity of a reflector antenna deteriorates as the feed moves away from the focal point for beam scanning. This deterioration can be substantially reduced if a cluster feed instead of a single feed is used to control a beam. A closed-form solution is presented for the cluster excitation to achieve the optimum directivity. For an offset108 lambda parabolic reflector scanning 10 beamwidths, the optimum-directivity achieved by a 19-element (seven-element) cluster is 12 dB (8 dB) higher than that of a single element. Comparison of the optimum-directivity design and the popular conjugate field matching design is made. When the cluster spacingd is greater than1 lambda , it is found that the optimum directivity is higher than that of conjugate field matching (CFM) scheme by an insignificant amount, although the excitations of two designs can be quite different. Ford < 0.5 lambda , the optimum design may exhibit the supergain phenomenon, namely, extremely high directivities achieved by an oscillatory cluster excitation. 相似文献
15.
Christodoulou C. Botula A. Kauffman J. 《Antennas and Propagation, IEEE Transactions on》1985,33(10):1101-1108
Large reflector antennas, from cost and weight considerations, appear to be the best configurations for achieving the very large apertures needed for antennas mounted on orbiting spacecraft. Radiation pattern calculations for such antennas are, in general, quite costly both in terms of computer time and the considerable memory required to perform the large surface integrations. The method presented here treats the large aperture as a set of small subapertures for which the radiation fields are computed separately, stored and then added with due regard to phase to yield the radiation pattern of the large reflector. Numerical methods developed to provide the illumination of each subaperture to avoid overlap of the aperture fields of adjacent subapertures and to simplify the surface integrations are discussed. The algorithm is straightforward and has considerable intuitive appeal. The methods of geometrical optics (GO) are used to calculate the aperture plane tangential field components; and electric vector potential is then used to compute the antenna radiation fields. The algorithm includes a set of options for different reflector surfaces. If high accuracy of the far sidelobe levels is required, a subroutine accounting for edge diffraction should be added to the algorithm given here. Calculations made with this algorithm are compared with calculations made by other methods and with measured patterns. 相似文献
16.
为解决大口径太赫兹反射面天线工程实现的难题,提出了一套口径2.5 m的星载太赫兹天线系统。该天线由大口径反射面天线和准光学馈电网络组成,可以接收183 GHz微波电磁信号。详细介绍了天线系统电性能仿真分析与大口径反射器的结构方案,对加工完成的大口径太赫兹天线系统进行了电性能测试,实测天线主波束效率达到90.2%,能够满足静止轨道卫星载荷的应用需求。 相似文献
17.
A. V. Kalinin V. P. Mal’tsev K. S. Shcheglov 《Journal of Communications Technology and Electronics》2007,52(5):510-526
The experimental characteristics of a 25-m reflector antenna used as part of a radiointerferometer with a base of 100 m are presented. The radiointerferometer operates in the 10-cm wave band on the basis of signals from natural extraterrestrial radio sources and artificial satellites. Measurement techniques and corresponding hardware are developed and investigated. 相似文献
18.
S. E. Bankov G. G. Grachev M. D. Duplenkova E. V. Frolova 《Journal of Communications Technology and Electronics》2014,59(6):504-522
A multibeam integrated reflector antenna operating in the millimeter wave band is considered. The antenna consists of a radiating array, a planar mirror, and a multichannel feed. The results of simulation of a radiating array of slots in a metal screen are presented. The array is manufactured on the basis of a medium with forced refraction, including a double-slot array, which can radiate along the normal to the array plane. Operation of the array in the multibeam mode is analyzed. It is shown that application of a medium with forced refraction increases the array aperture efficiency in this mode. The results of the design of a planar two-layer mirror are presented and the mirror’s quality indices are estimated. A multichannel radiator designed as an array of planar H-plane horns is studied. The results of simulation of such a radiator with the help of an approximate technique and numerical solution of an electromagnetic problem are considered. The design of the multibeam antenna and its experimental characteristics are presented. 相似文献
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20.
The principle and performance of Synthetic Impulse and Antenna Radar(SIAR) are analyzed with the concept of 3D matched filtering. The discussion here is concentrated on the characteristics of SIAR in the case of three dimensions. The results obtained are helpful for designing this new style radar. 相似文献