共查询到20条相似文献,搜索用时 609 毫秒
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射电望远镜一般要在宽频段内进行连续观测, 但传统相控阵天线设计方法难以兼顾宽频带和大角度扫描特性. 紧耦合天线的设计方法为宽带大角度扫描天线提供了新的设计思路, 基于此设计了一款宽带双极化 Vivaldi相控阵馈源. 首先结合Wheeler提出的连续电流片概念及等效电路对紧耦合原理进行理论分析, 然后针对Vivaldi天线分析了阵元间的强耦合能够有效拓展天线的工作带宽. 在此基础上设计了一款宽带Vivaldi相控阵馈源. 馈源阵列由8×9 Vivaldi天线阵元组成, 该阵列的工作带宽为2-8GHz, 并且能够在E面和H面均实现±$45^\circ$的扫描特性. 最后对该馈源阵列进行了样机加工和测试, 测试结果与仿真结果具有较好的一致性. 相似文献
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馈源是射电望远镜天线系统的一个重要组成部分,其性能将直接影响整个天线系统的电性能。针对射电望远镜天线系统中典型的圆锥喇叭馈源,通过三维电磁仿真软件(CST STUDIO SUITE12.0)进行建模,分析了不同圆锥度、椭圆度及不圆度对圆锥喇叭馈源远场方向性的影响。结果表明:口径面的椭圆度在一定范围内变化时,对圆锥喇叭馈源方向性的影响较小。且其回波损耗小于-15dB;圆柱波导段的圆锥度大于1:20时,圆锥喇叭的效率会受到一定的影响:不圆度的影响则较大。文中得到的结构因素对圆锥喇叭馈源电性能影响的研究结果.对射电望远镜天线系统中圆锥喇叭馈源的设计和制造具有一定的参考作用。 相似文献
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《天文研究与技术》2017,(2)
随着射电天文研究的不断深入,科学家对望远镜分辨率和灵敏度的要求也不断提高,同时要求望远镜具有更宽的观测波段。单口径望远镜低频波段用主焦点接收,馈源尺寸可以更紧凑。为了不影响双反射面天线次焦点的馈电功能,主焦点馈源的放置及换馈方案必须高效合理。以建于新疆奇台的110 m口径全可动射电望远镜为研究对象,以意大利SRT 64 m和德国Effelsberg 100 m射电望远镜为参考,对两种方案应用于奇台110 m射电望远镜的可行性进行分析,并提出一种利用线性模组进行主焦馈源快速切换的新型方案。进行了直线模组机构的建模和仿真,并对口径面信号遮挡进行了分析,结果表明,此方案能有效满足望远镜的工作需求。 相似文献
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《天文学报》2016,(1)
大型射电望远镜在观测过程中,随着俯仰角度的变化,副面支撑、背架、主反射面等都有不同程度的变形,这将导致天线效率在高低俯仰角上明显下降,天马65 m射电望远镜副面系统的安装可以用来补偿副面支撑和主面的重力变形,在不同的俯仰角度上,副面位姿的调整可以提高天线的效率和指向性能.通过在X波段和Ku波段研究副面位姿变化对天线效率的影响,用射电法建立了随俯仰角度变化的副面位姿随动调整模型和指向补偿模型.此外还测试了副面随动与固定对天线效率的影响,结果表明副面随动模型可以有效改善65 m望远镜在高低俯仰角上的效率,使得在整个俯仰角范围内,X波段的接受效率均达到60%以上. 相似文献
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把抛物面天线的偏焦理论应用于FASTL波段多波束馈源系统的设计,分析了馈源喇叭横向偏焦距离与相应波束偏离角之间的关系,结合多波束射电望远镜扫描方式的要求,给出了FASTL波段多波束馈源的工作带宽、多波束馈源中相邻喇叭的间距以及喇叭口径大小的限制,并对正六边形阵列中处于不同位置的喇叭对应的波束的主瓣情况作了详细计算和分析。由此说明了FASTL波段多波束馈源采用19波束的可行性。另一方面,根据得到的工作频率带宽和喇叭口径大小的情况,对OMT和喇叭类型的选择进行了探讨。本文给出了FASTL波段多波束系统的大概轮廓,为进一步精确设计指明了方向。 相似文献
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V. Batllo 《Celestial Mechanics and Dynamical Astronomy》1998,71(3):191-201
The objective of this paper is to develop a simple model of an encounter between a comet and a planet, with a subsequent capture
or an escape, and to study the potential consequences. The hypothetical scenario is as follows: a comet with a conic orbit
meets close to one of its vertices (located near the ecliptic plane), a jovian planet, and transforms its orbit. There are
two hypotheses which are made for the shock: this vertex becomes one of the final vertices and the orbital plane of the comet
is unchanged during the encounter as it was the case for Brooks 2 in 1886.
In this model, it was able to find an equation which was then used to obtain the pre‐ and post‐encounter orbits elements and
the kind of orbit (ellipse, hyperbola, parabola) with respect to the initial inclination. The numerical experiments with the
observed comets often provide pre‐encounter orbits with an aphelion point located near another jovian planet farther from
the Sun, and so on with sometimes several planets, or with an aphelion point located beyond the Pluto orbit.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
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We formulate the problem of an infinitesimal particle moving in the space under the influence of the gravitational force induced
by a homogeneous annulus disk fixed on a plane. We compute using different coordinates and in terms of an elliptic integral
the potential associated to this problem. Also we study the symmetries of the associated potential. After that, we look at
the dynamics in some particular cases, namely: in the line perpendicular to the plane that contains the annulus disk and passes
through the center of the ring and on the plane that contains the massive annulus.
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Results of evolutionary calculations for a close binary system with a central helium burning He-star filling its Roche lobe and an accreting white dwarf are presented. Values for the mass of the components and the degree of central helium exhaustion before the filling of the Roche lobe are varied. It is shown that in such a system the mass accretion rate will remain for a long time (2–4) Ö 10–8
yr–1 ifq<1 (q=M
He,2/M
CO,1). The obtained results are discussed in connection with pre-supernova I phenomenon. 相似文献
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Tapan K. Chatterjee 《Astrophysics and Space Science》1981,76(2):491-502
The tidal force effects of a spherical galaxy passing head-on through a disk galaxy have been studied at various regions of the disk galaxy and for various orientations of the disk galaxy with respect to the direction of relative motion of the two galaxies. The density distribution of the disk galaxy is taken to be, (r)=ce–4r/R
, where c is the central density andR is the radius of the disk. The density distribution of the spherical galaxy is taken to be that of a oolytrope of indexn=4. It is found that as a result of the collision, through the central parts and the outer parts of the disk galaxy remain intact, the region in between these two regions disrupts. Thus a ring galaxy with a nucleus embedded in the ring-i.e., a ring galaxy of the RN-type, is formed. 相似文献
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E. H. Nikogossian 《Astrophysics》2000,43(1):32-39
The hierarchical structure of the clusters of galaxies A 999, A 1016, and A 1142, which are part of one supercluster, is investigated.
The HTree method is used to determine that A 999 and A 1016 are a single, dynamically bound system consisting of two “cores”
and a common field of galaxies. The composition of the “cores” includes almost all the E and S0 galaxies, the luminosity function
of which is very nearly Gaussian. It is also established that the cluster A 1142 has a nonuniform structure, both in density
distribution and in radial velocity distribution. The location of the maxima in density and in the radial velocity distribution
correlates with the galaxies that are sources of radio and x-ray emission.
Translated from Astrofizika, Vol. 43, No. 1, pp. 45-54, January–March, 2000. 相似文献
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H. Zirin 《Solar physics》1976,50(2):399-404
A large surge was observed on September 17, 1971, part of which, after travelling 200 000 km through the corona, returned to the surface to form a filament. The filament lasted about 30 min, then rose up and returned to the source of the surge. We interpret this as the filling of a semi-stable magnetic trap.The energetics of radio, X-ray, and surge expulsion are estimated. The radio spectrum and flux correspond to a thermal source of area 4 (arcmin)2, T 190 000 K, N
e
2
V 7 × 1048, which is optically deep at 8800 MHz.The soft X-ray source has T 12 × 106 K, N
e
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V 3 × 1048; and if an equal mass is expelled in the surge, the kinetic energy of the surge is similar to the thermal energy of the X-ray source. 相似文献
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