大型可展开空间天线结构技术的新进展

本文简单介绍了近年来大型可展开空间天线结构技术的进展情况,包括径向肋/环向绳索天线结构技术、混合型充气/机械展开天线结构技术、充气天线结构技术、天线表面主动控制技术、大型和超大型空间天线在轨装配技术等。     

天线测量的数据处理及实时测量的前景

本文详细介绍了处理天线检测数据的两种最常用的方法及其特点的对比。描述了天线实时测量及数据处理的精密自动化测量模式及传感器与计算机之间的两种数据通信方式,展示了天线实时测量的前景。     

测量天线的参数

当在开阔场或电波暗室中测量辐射发射或辐射抗扰度时,需要使用测量天线.在电磁兼容测量的其他方面,如开阔场或电波暗室性能检测、屏蔽效能测量以及对大型电磁骚扰源的现场测量等,也都需要使用测量天线.对天线参数与特性的理解深度直接影响着对测量方法的正确设计以及测量结果的正确理解.本文向读者重点介绍测量天线的一些最重要的参数,阐明容易混淆的概念.本文不涉及各种不同类型测量天线的特点与性能,也不涉及天线参数的校准.     

机动雷达大型天线自动对接技术的研究

机动雷达大型天线阵面常采用多块天线子阵面吊装拼接的架设方式,架设时受架设效率低、吊装操作存在不确定因素等的制约,使得大型雷达的机动性较差。通过对大型天线阵面自动对接技术的研究,将目前已有的室内大型零部件自动对接技术应用到大型天线装配技术中,以实现机动雷达大型天线的快速装配。主要论述了机动雷达大型天线自动对接的工程原理和所需攻克的关键技术,其中包括数字化自动测量技术、天线位姿自动调节技术和伺服控制技术等;并对其主要功能的实现方法进行了研究。     

雷达天线的近场测量

一、引言高性能的雷达天线迫切要求发展高性能的天线测量技术。比主波束峰值低50dB的旁瓣电平和比毫弧度更高的指向精度正成为各种类型雷达天线的共同要求。普通的远场测量场常常不能适应上述天线的精确测量需要。木文主要叙述用近场测量技术对雷达天线方向图和增益的测量。新的测量技术不仅能测量天线的方向图和增益,而且能提高天线的测量精度和测量能力,降低测量费用,以及对天线作出诊断。表1列出了目前使用的雷达天线测量技术。     

大型双曲率雷达天线检测方法研究

针对某大型双曲率预警雷达天线(4m×8m)提出了比较完整的测量与调整方案。天线三维坐标测量采用了多台电子经纬仪构成的前方交会测量系统,通过最优设站技术,使坐标测量的精度达到±0.1 mm左右,实现了精密、高效的数据采集。在数据处理方面,创造性地提出了修正公共点坐标转换法,使设计坐标系的复现更准确合理;提出了双曲率雷达天线设计坐标的曲线插值方法,实践表明缩短了计算时间;独立研究出了该天线法向偏差的严密计算方法,实现了用法向偏差来评定天线的表面精度。探讨了雷达天线的安装调整方案,提出了系统制造误差的补偿方法和天线主面的调整方法,提出了馈源安装调整方法。通过该文的实践,提高了对大型双曲率天线检测的认知水平。     

几何绕射理论在天线测量中的应用

远场测量是大型天线常用的测量方法，但在用远场测量技术对天线的辐射特性进行测量时，地面反射波的干扰很大，影响测试数据的准确属于 ，本文提出了一种用来消除地面反射波的新方法－金属挡屏几何绕射法。     

电调天线工程应用

随着社会信息化的发展,人们对网络服务质量的要求越来越高,为了满足人们对网络的需求,需根据区域的通信量实时调节天线覆盖区域,以实现更有效的网络覆盖率.但传统的天线因受多种因素的影响无法提供实时的网络整网优化,因此,可远程实时操控的电调天线成为大势所趋.主要从电调天线的优点、电调天线的组网方案、电调天线的工程应用及电调天线的可靠性问题4方面介绍电调天线.     

大型相控阵天线唯幅度测量快速标校法

针对目前大型相控阵天线校准时效不佳问题,研究了一种唯幅度测量快速标校方法。对于N元相控阵天线,该方法将阵面分为N种不同组合,通过测量每种组合在不同相态和开关态下的总辐射场幅度,由测量值解算出各个天线单元幅相值。该标校方法仅需幅度测量,并且所需的测量次数只有(3N+1)次,因此,设备可大大提高大型相控阵天线的校准速度以及简化校准设备;另外,在求解天线单元幅相值过程中,该标校方法可避免方程二义性问题,从而简化计算过程。768元相控阵天线仿真实例验证了该标校方法的正确性。     

测量飞行体上天线方向图的新方法

本文主要研究大型飞行体上天线方向图的测量,解决了如下三个问题:(1)模型测量中电导率不能随缩比而变化,本文给出了由此引起之测量误差的数量范围。(2)提出了“局部编尺”法这种实际测量方法,通过选择合适尺寸的局部飞行体,以保证测试误差在允许的范围之内。(3)提出了“测量计算”法,即把天线装在很小的矩形板上测出实验数据,通过分析找出理想方向图,再用几何绕射理论就可算出实际飞行体上的实际方向图,这种方法可作为天线测量的一个重要方向。如灵活使用这两种方法来测大型飞行体上任意位置处平装或接近平装的线极化天线的两个主平面天线方向图,其误差小于0.5分贝,其经济效益是非常高的。     

Upgrading the Haystack radio telescope for operation at 115 GHz

The Haystack 37-m radio telescope has been upgraded for operation at frequencies up to 115 GHz. A unique deformable subreflector with active actuator control has been developed to correct for gravitational distortion effects including astigmatism and deflections associated with the particular reflector surface. Active thermal compensation of the surface has also been implemented to conduct for both thermal lag effects and circularly symmetric gravitational deviations. Holographic mapping of the antenna surface deviations was achieved using 12-GHz geostationary satellite transmissions, which required the use of special techniques to correct for diffraction and multiple reflection effects involving the space-frame radome that covers the antenna. Realignment of the antenna surface utilized a finite-element structural model to translate surface deviations to motions of the unusual adjustment mechanisms on the antenna. The currently measured rms surface deviation (Dec. 23, 1992) is 210 μm. The telescope has been equipped with a two-channel cryogenically cooled 3-mm SIS receiver, covering the range from 84 to 115 GHz. A new flexible digital spectrometer has been constructed for spectral line astronomy. Configurations can range from a widest bandwidth coverage of 160 MHz at 512 lags to 0.66 MHz at 4096 lags. Examples are given of surface holographic maps and radio measurements of aperture efficiency, pointing, and other performance parameters     

射电望远镜天线的指向精度测量系统设计

指向精度是衡量大口径射电望远镜天线电轴指向准确度的重要指标,如何准确地测量出天线的指向精度对使用者而言尤为重要。针对射电天文望远镜的工作特点,提出了采用射电星作为发射源进行天线指向精度测量的方法,以方位轴为例介绍了测量基本原理,根据测量需要对系统软硬件进行了设计,对实际测量和处理过程进行了描述,给出了测量结果和分析。结果表明该方法可以快捷、准确地测出天线在全天区的指向精度。     

Interferometric measurement at 1415 MHz of radiation pattern of paraboloidal antenna at Dwingeloo radio observatory

The complete radiation pattern of a 25-m diameter radio telescope has been measured at 21-cm wavelength to a level of 60 dB below the main beam response. Strong cosmic radio sources with known flux density were used as a signal source. The measurement employed an interferometer consisting of the radio telescope and a 7.5-m diameter reference antenna. By changing the orientation of the telescope, while keeping the reference antenna pointed at the source, the output voltage of the interferometer varies proportional to the field strength pattern of the telescope. This method provides a large improvement in sensitivity over a total power measurement. The paper discusses the theoretical basis of the technique. It describes the layout of the interferometer, the electronic equipment, and the methods of observation and reduction of the data. Some 19 000 points in the pattern were measured. The pattern is displayed by contour plots of equal level. The derived main characteristics of the telescope [1968 AD] at 1415 MHz are as follow: gain49.0 pm 0.2dB, absorption area282 pm 8m², aperture efficiency 0.56, half-power beamwidth0.57 times 0.62deg. The accuracy and detail allow astronomers to reliably correct radio astronomical observations for the effect of radiation in the sidelobes, spillover region, and feed support scatter lobes. Theoretical calculations of pattern parameters may be checked quantitatively.     

Telescope surface measurement with two feeds

A method is suggested where a reference feed is fixed at the telescope focus, and a second feed has a lateral offset and scans the focal plane. The telescope tracks a celestial radio source, and the receiver measures the phase difference at the two feeds and their (voltage) amplitude ratio. A set of coordinate transformations is applied, after which the surface deviationssigmafrom a paraboloid can be obtained by a Fourier transform. The measuring error is discussed, and the best wavelength is found to be between 14 and 21 rmssigma.     

RATAN-600: the World's biggest reflector at the `cross roads'

The RATAN-600 new-technology telescope, which supplies about one-quarter of the observational material in Russia in the field of radio astronomy and more than 80% in the central, centimeter-decimeter range, is described. The RATAN-600 is the first multi-element-reflector radio telescope without any structure linking the surface elements. The functions normally performed by such structure are executed by the Earth's surface. It is also the first radio telescope with a controlled-shape surface. In observations at different elevations above the horizon, the shape of its surface varies, remaining in the family of second-order surfaces. The RATAN-600 is also the first aperture-synthesis reflector-type telescope. The location of the radio telescope, its design, its modes of operation, and its future prospects are discussed     

On refocusing a radio telescope to image sources in the near fieldof the antenna array

A theoretical model is developed for describing the operation of a radio telescope using techniques from optical coherence theory. This model is then used to develop a more systematic approach to the problem of refocusing a radio telescope to image sources which are within the near-field of the antenna array when the antenna array is in the far field of the source distribution. This is done by refocusing the telescope onto the sources in analogy to a photographic camera. Two methods for refocusing the telescope are described which would require no modification to most existing telescopes. In the first method, refocusing is accomplished either electronically by curving the antenna array into a portion of a hemisphere with a center at the source, or, alternatively by processing the correlation function data obtained from the antennas in a somewhat modified manner     

The 100-meter radio telescope at Effelsberg

The 100-m fully steerable radio telescope of the Max-Planck-Institut für Radioastronomie (MPIfR) has now been in service for over a year. The telescope was designed to allow observations in the decimeter and centimeter wavelength regions, with the vastly improved resolution given by the 100-m diameter. During construction of the telescope measurements were made at a wavelength of 75 cm. Since the completion of the adjustments, tests and observations were made at 11-cm and 2.8-cm wavelengths. In particular, at the 2.8-cm wavelength, tests have fully confirmed the design goals. In fact, we hope to extend the operational range of the telescope at least to the wavelength of 1.2 cm. A number of problems, new in this field, had to be solved in the construction of an instrument of this size and precision. Measuring methods are described which allowed adjustment of the surface to ±1 mm. A computer-controlled servo loop allows setting of the telescope to 5". Experience of operation under various conditions is described.     

A new design project of the line feed structure for large spherical radio telescope and its nonlinear dynamic analysis

A new design of the line feed structure for a large spherical radio telescope (LSRT) is presented in this paper. Integrated mechanical, electronic, optic and automatic control technologies are employed to make considerable improvement upon the Arecibo spherical radio telescope in Puerto Rico, U.S.A. Nonlinear dynamic analysis of the suspended cable system was carried out with some sensible results that could be useful to the real engineering of LSRT.     

The mechanical design and kinematics accuracy analysis of a fine tuning stable platform for the large spherical radio telescope

A large Stewart platform for fine tuning of the feed source tracing is presented in this paper. The model of kinematics control is developed with coordinate transformation, and a quasi-static load analysis is made by virtual work principle with Jacobian matrix because the tracing speed is slow. The kinematics accuracy model is derived by position vector analysis, and the kinematics accuracy results are provided. It has shown that the designed Stewart platform can satisfy the requirement of feed source trajectory control of large spherical radio telescope.