有源天线联试中的几点实用经验与分析

有源天线顾名思义,不仅仅包含传统意义上的无源部件,更多地是向系统级别迈进,这就要求天线设计研制人员需要掌握更多的＂有源＂部件方面的知识。文章给出了某有源天线联试过程中所积累的一些经验,并对其进行了分析,为更多从事有源天线设计的技术人员提供参考。     

关于纤维增强复合材料力学性能可设计性的分析

纤维增强复合材料是一种多相结构材料，主要由增强纤维和树脂基体材料组成。其性能可设计性是指可按照设计要求进行选择不同的增强材料和树脂基体材料以及它们的含量和各种铺层形式，可组成具有不同性能的各种复合材料。这给复合材料可设计性提供更大的自由度。该文结合工程应用需要，主要对其力学性能可设计性进行了分析研究。     

卫星间光通讯系统中比特率等主要参量对最大通讯距离的影响

文中讨论了在保证卫星间光通讯系统的通讯质量前提下，系统的各个主要参量之间的相互制约关系，最大通讯距离受各参量影响的情况。通过分析各个参量对通讯距离影响的大小，找出了增大通讯距离的较好途径。     

从具有非线性特征的衰减“拍”波形确定阻尼率的方法

本文提出一个从具有非线性特征的衰减“拍”波形确定阻尼率的方法——二次包络法。第一次包络是对衰减“拍”波形实施希尔伯特(Hilbert)变换得到的,第二次包络是以第一次包络曲线的峰谷值为基准,分段用线性插值形成的变系数指数曲线。根据第二次包络的两条曲线,用对数减量确定随响应振幅而变的阻尼率。本文以分离贮箱中液体晃动阻尼的确定为例验证了方法,结果表明精度达到了工程应用的程度。除对液体晃动的阻尼测定之外,本方法还适用于密模态高粘弹性结构的模态阻尼测定。     

航空电子设备安装支架的刚度与频率优化设计

航空电子设备用于飞行中的数据采集,通常使用安装支架固定于机头雷达罩,研究安装支架的刚度和一阶频率性能,避免设备支架在飞行过程中出现塑性变形和共振现象,对提高飞行稳定性具有重要的工程意义。在惯性载荷下对安装支架进行静强度和模态分析,采用一种灵敏度分析方法确定安装支架的设计变量,以结构总质量最小为优化目标,在保证安装支架的刚度和一阶模态性能的前提下对支架各个构件的厚度进行优化设计,并对优化后的安装支架结构进行振动试验。结果表明：优化后的安装支架结构刚度基本保持不变,一阶频率提高了18.09%,质量减少了19.33%,改进设计满足设备安装要求。     

航天器多普勒测速平均误差的分析与修正

对航天器多普勒测速平均误差进行了分析,详细推导了圆轨道和椭圆轨道时该误差的计算公式,计算了不同采样周期和轨道高度时的误差大小。经过分析指出,该项误差对于高轨航天器影响较小,对于低轨航天器可以通过缩短采样周期或利用3个点或多个点的连续测量数据进行修正。     

基于视图的试验通信需求分析方法研究

针对试验通信系统规划中的需求分析工程化问题,按照体系结构方法的要求,提出了一种基于视图的信息需求获取及分析处理方法;该方法能够在一定程度上简化和规范化需求获取,并通过一系列分析步骤实现从试验要素和任务向试验信息流的转化。     

Proposal of new models of the bottom-side B0 and B1 parameters for IRI

The time series of hourly electron density profiles N(h) obtained from 27 ionosonde stations distributed world-wide have been used to obtain N(h) average profiles on a monthly basis and to extract the expected bottom-side parameters that define the IRI profile under quiet conditions. The time series embrace the time interval from 1998 to 2006, which practically contains the entire solar cycle 23. The Spherical Harmonic Analysis (SHA) has been used as an analytical technique for modeling globally the B0 and B1 parameters as general functions on a spherical surface. Due to the irregular longitudinal distribution of the stations over the globe, it has been assumed that the ionosphere remains approximately constant in form for a given day under quiet conditions for a particular coordinate system. Since the Earth rotates under a Sun-fixed system, the time differences have been considered to be equivalent to longitude differences. The time dependence has been represented by a two-degree Fourier expansion to model the annual and semiannual variations and the year-by-year analyses of the B0 and B1 have furnished nine sets of spherical harmonic coefficients for each parameter. The spatial–temporal yearly coefficients have been further expressed as linear functions of Rz12 to model the solar cycle dependence. The resultant analytical model provides a tool to predict B0 and B1 at any location distributed among the used range of latitudes (70°N–50°S) and at any time that improves the fit to the observed data with respect to IRI prediction.     

Contributions of the French Institut Géographique National (IGN) to the International DORIS Service

DORIS is one of the four geodetic space techniques participating to the Global Geodetic Observing System (GGOS). Since the early development of this system, the Institut Géographique National played a specific and active role. Within, the International DORIS Service (IDS), IGN is in a particular position. While it is responsible for the installation and the maintenance of the DORIS ground tracking stations, it also handles one of the two IDS data center delivering DORIS data and products and has been an IDS Analysis Center for years, providing all possible IDS products, in particular the latest ignwd08 time series in preparation of ITRF2008. This paper explains the different aspects of the IGN contribution to IDS from an historical point of view, presents current activities and scientific results and provides a perspective for future activities. Recent DORIS results show a 10 mm precision or better when more than four DORIS satellites are available. Comparisons between recent DORIS solutions (ign07d02 and ign09d02) and past ITRF realizations show that errors are shared between the DORIS and the ITRF realizations. Some problems related to DORIS data processing are also discussed and possible ways to solve them in the future are discussed. In particular, we can now reject the tropospheric origin of the problem detected in the Envisat data after the software upload of October 12, 2004. A few applications in geodesy (terrestrial reference frame, Earth’s polar motion) and geophysics are also discussed as a natural extension of these service-type activities.     

重排算法在多目标雷达信号分辨中的应用

本文使用１５年前由柯德锐等人首次在谱图中使用,并经弗朗克斯等人改进并推广的重排算法,对多目标雷达信号进行架次识别,此重排算法简单且极易实施,在重排后失支双线性时,却保持了其他许多可取特性,并换回了Ｃｈｉｒｐ信号和冲击信号的准确定位,针对编队多目标雷达信号的线性调频特点,利用此重排算法在权衡能量聚集性和消重排振荡的同时,实现了对编队多目标雷达信号的分辨。