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.     

太阳射电望远镜自动观测控制平台的研究与设计

为了实现观测者足不出户的坐在计算机面前就可以完成使用射电望远镜观测天体的任务,在实验室射电频谱仪的基础上,提出了一种太阳射电望远镜自动观测控制平台的整体解决方案。以VC++6.0设计上位机界面,以MSP430F169单片机为下位机,上位机控制下位机使其控制实验室电机方位和俯仰的转动,真正实现对望远镜的自动控制。实验结果表明,该系统工作稳定,可以达到设计的目的。     

The wind-induced vibration control of feed supporting system for large spherical radio telescope using electrorheological damper

Considering the wind-induced vibration of the feed supporting system with cables for the optomechatronics design project of next generation large spherical radio telescopes, a prototype of adaptive electrorheological (ER) damper is designed to realize additional damping control of this vibration. The model of wind is first developed to implement this design and simulations. The model of the designed ER adaptive damper is described in detail, and the strategy of additional damping control using the controllable field-dependent damping force of the ER damper to counteract the wind force is proposed. The numerical simulation results have shown the validity of the designed adaptive ER damper to suppress the wind-induced vibration of the feed supporting system, and the additional damping vibration amplitude can be suppressed to one-half of the original amplitude without ER damper.     

Analysis of active surface reflector antenna for a large millimeterwave radio telescope

The authors analyze the effects of imperfect segment alignment on the aperture efficiency of a large millimeter telescope. A 50 meter diameter instrument of this type specified to operate to wavelengths as short as 1 mm is being designed with an actively controlled main surface. By simulating the performance of the control system, they generate samples of tilt and piston errors for the segments from which the antenna radiation patterns and aperture efficiencies are calculated. They make a comparison of these results with models of antenna tolerance theory developed by Ruze (1966), which relate the aperture efficiency to the RMS phase error. They find that Ruze's formulas have a different range of validity when the aperture RMS phase error, rather than the RMS surface error, is used as a parameter. When appreciable tilt errors are present in large segmented antennas, the aperture RMS phase error tends to a constant value, independent of the aperture illumination and of the shape of the segments. They conclude that the antenna RMS surface error is a better tracer of the aperture efficiency than is the aperture RMS phase error when Ruze's formula is used. They find that this well-known expression stands as a lower limit to the performance of large segmented reflector antennas     

Upgrade of a large millimeter-wavelength radio telescope forimproved performance at 115 GHz

A 20.1-m-diameter radome enclosed radio telescope, built by Electronic Space Systems Corporation (ESSCO) at the Onsala Space Observatory (OSO) near Gothenberg, Sweden, in 1975, was upgraded by ESSCO in 1992 for improved operation at 115 GHz, increasing the system aperture efficiency from 20% to 40% at this higher frequency. Electrical gain measurements confirm geometric optics predictions of efficiency and improved antenna patterns. The upgrade included replacement of the two inner reflector panel rows with 31-μm panels, stiffening the reflector backstructure based on finite-element structural analysis for a measured rms gravity deformation of 59 μm in the 25° to 70° elevation range, and optical alignment of the reflector surface to 58 μm rms accuracy. This alignment accuracy of approximately 1/345000 of the reflector diameter was accomplished with an electronic angle-measuring theodolite and digital radial strap gauges. Data were downloaded in real time to an on-line portable computer performing surface metrology calculations. Graphical data are presented that compare computer predictions of reflector backstructure gravity deformations to optical measurements, which proved crucial in achieving the stringent alignment accuracies. Measured antenna efficiency data before and after the upgrade are included     

Sidelobe levels of a large radio telescope employing a combination of physical and resistive tapering

The main beam, sidelobe levels, and effective collecting area of a proposed radio telescope array, operating at 12 MHz, are considered. The telescope consists of two large rectangular arrays containing several thousand half-wave dipoles arranged horizontally in a tee shape above a ground plane. A narrow beam is formed by cross-correlating the outputs of the individual arms of the tee. The possibility of sidelobe reduction using a form of physical tapering consisting of reducing the width of each rectangular arm at appropriate intervals along the array is assessed, by comparing the performance achieved with this type of taper to that obtainable with the more common resistive taper. It is concluded that when the effects of random errors in element excitation are considered the performance of the physically tapered and resistively tapered arrays compares favorably.     

Measuring the gravitational astigmatism of a radio telescope

Most conventional radio telescopes will show a strong astigmatism when tilted, resulting in surface degradation, which can be corrected with a mechanically deformable subreflector. Astigmatism means different focal lengths (Delta F) in two perpendicular planes. A most direct way of measuring the astigmatism is to measureDelta Fwith an elongated rotatable feed, illuminating only a central strip of the telescope. Equations are given for the relations betweenDelta F, rim deviationA, and rms surface deviationDelta z, and for the dependence of these quantities on elevation angle. This method was applied to the 140-ft. telescope. Between zenith and horizon, the measured range isDelta F = (51 pm 2)mm, yielding an astigmatic rim deviation ofA = 8.7mm, and an astigmatic rms surface deviation ofDelta z = 2.87mm. The latter agrees with astronomical efficiency measurements, showing that the total gravitational deformation is mainly of a simple astigmatic shape, to be corrected by relatively simple means.     

带金属盒的月球射电仪天线特性研究

选择RWG和Costa基函数用矩量法分析了线面结合的天线问题,计算了月球射电仪典型天线的输入阻抗和方向图.给出了单极和双极天线的典型结果,得到了金属盒大小对结果的影响关系.对于双极天线还对比了中馈和边馈两种方式的结果.在计算中,使用了9点高斯积分法处理奇异积分,得到了较好的效果.     

软件无线电调制解调通用平台的设计与实现

软件无线电被认为是继模拟通信到数字通信、固定通信到移动通信之后无线通信领域的第三次突破。文章在研究软件无线电的基本结构的基础上从信号空间映射的角度对通信信号的调制解调进行了深入的研究，将已调信号表示为N维正交基函数的展开式，根据调制方式确定调制信号到N维信号空间的映射从而完成调制过程；同时引入空间距离的概念，根据调制映射关系，建立起多对一的最优信号检测理论。并且使用MATLAB编制了基于软件无线电结构的通信信号调制解调通用平台软件，实现了对各种调制解调模式的兼容。     

The designing, manufacturing, and testing of a dual-band feed system for the Parkes radio telescope

This paper presents the designing, manufacturing, and testing of a dual-band feed system for the Parkes radio telescope (Australia). The feed system consists of a coaxial horn and associated feed components to operate in the 648-712 MHz and 2.6-3.6 GHz frequency bands. The manufacturing of such a feed system was challenging, and we present the innovative solutions that were devised to fabricate the different parts of the feed system. Preliminary measurements indicate that the overall system, feed and reflector, is working to operational expectations, and valuable scientific results have already been obtained using the simultaneous dual-frequency capability.     

Replacing a technology: The large space telescope and CCDs

The Hubble Space Telescope is due to be launched in 1986. It is certainly the chief space astronomy initiative of the 1980s, perhaps of the late twentieth century. It is to carry six scientific instruments, and in this paper we investigate the debate on the choice of detectors for what was seen as the chief instrument during the project definition phase, the so-called wide-field camera. In the end CCDs were selected, despite the fact that this decision had to be made a mere seven years after the concept on which they are based was published. We argue that this rapid development of CCDs as astronomical detectors was due to a strong mix of "market pull" and "invention push" together with the very active interest of one group within the astronomical community, planetary scientists.     

基于精细分析的辐射源识别软件系统设计及实现

提出了一种基于脉内细微特征分析的辐射源识别系统设计方案,并进行了工程实现。试验结果表明,该系统可以获得高精度的脉内、脉间特征参数和良好的辐射源识别结果。     

基于数字平台罗经的舰载雷达大惯量伺服系统设计

介绍了一种在低数据率的数字平台罗经接口下某舰载雷达伺服系统对大惯量稳定平台进行稳定跟踪的设计方法。该伺服系统采用全数字的伺服控制模块作为其位置环的控制核心,利用伺服电机驱动器实现伺服电机速度电流双闭环,组成了一个有良好位置控制性能的数字伺服系统。     

Delay analysis and dynamic tuning of an acknowledged mode radio link control protocol

In this paper, in-sequence delivery delay of an acknowledged mode radio link control (AM-RLC) protocol in wideband code division multiple access (W-CDMA) networks is studied. Two special protocol phenomena, duplicated retransmission, and delayed acknowledgment, are reported. A two-step dependent Markov chain is adopted to model the AM-RLC protocol. The in-sequence delivery is evaluated by means of an analysis through tracking the transmission status of a specific packet data unit (PDU) and its blocking PDUs. Analysis results indicate that in-sequence delivery delay is approximately linear with frame error rate. Analysis results also exhibit that in-sequence delivery delay is highly related to status report interval. Based on this observation, a dynamic AM-RLC scheme is proposed. The proposed AM-RLC scheme dynamically changes status report interval according to channel status. Extensive simulations are carried out to verify the effectiveness of the proposed scheme. It is found that the proposed scheme can reduce status report without penalty to in-sequence delivery delay.     

Optics characterization of a 900-GHz HEB receiver for the ASTE telescope: design,measurement and tolerance analysis

The optics of a 900-GHz HEB receiver for the ASTE telescope have been analyzed by quasi-optical analysis and Physical Optics simulations in combination with beam pattern measurements. The disagreement between simulations and measurements has motivated an extensive campaign of Monte Carlo analyses to find out the cause of such a difference in results. Monte Carlo analyses have considered fabrication and assembly tolerances in all components in the RF chain, as well as some non-expected fabrication errors. This strategy has allowed determining the defective component. In short, the use of all available analyses techniques together with measurements has allowed singling out an underperforming element in an astronomical receiver. The change of this component will improve the optical efficiency and ease astronomical observations. These ideas can be of interest for any quasi-optical receiver at THz frequencies.     

65m射电望远镜面板精密成形原理与应用

针对上海天文台65 m射电望远镜主动反射面面板的工作特点及大面积、高精度面板的制造难题,提出基于“包络模具、蒙皮开缝、应力释放、真空负压”原理的面板精密成形技术.利用非线性有限元方法对成形过程进行数值模拟;分析得到型面曲率、蒙皮相对开缝长度及背筋高度等参数对成形精度的影响规律;优化了面板结构和成形工艺参数.最终研制的面板精度优于100μm,该技术已成功应用于上海65 m射电望远镜,可以为其他反射面天线的研制提供参考.     

广播电视监测信息管理平台的建设

在今天,广播电视应用越来越广泛,由此其监测也显得尤为重要,广播电视监测信息管理平台的建设,作为一个综合的、开放的信息共享、服务平台,可以便捷有效地对广播电视运行的各个环节包括播出、传播、用户等进行监测,以保证广播电视顺利、安全的播出。本文分析了广播电视监测网的主要作用,并就其建设整体架构、技术要求进行了较为全面的探究,以期完善监测系统。     

一种多功能SFP光模块监测平台的设计与实现

设计并实现了-种SFP光模块实时监测平台,该平台可实时监测SFP光模块的温度、电压、激光器偏置电流以及发射和接收光功率等参量.该平台的应用简化了系统维护工作,提高了系统的可靠性.     

大型望远镜环境温湿度监测系统设计

环境温湿度对大型望远镜的成像质量有非常大的影响。主要论述了大型望远镜温湿度监测系统的设计与实现,该系统采用SI7006-20A作为温湿度传感器,以STM32F103单片机作为处理器,通过CAN总线与上位机组网,实现环境温湿度的测量与显示。系统设计完成后,进行试验验证,结果表明,该系统能够对环境温湿度进行准确监测,可以为主动光学系统中的温湿度补偿与控制提供依据。