Spatio-temporal variability of the wet component of the troposphere – Application to satellite altimetry

Due to the presence of water vapour and cloud liquid water in the atmosphere, the wet component of the troposphere is responsible for a delay in the propagation of the altimeter signals, the Wet Path Delay (WPD). The high space–time variability of the water vapour distribution makes the modelling of WPD difficult, its effect still being one of the main error sources in satellite altimetry applications, e.g. in the estimation of Mean Sea Level (MSL). The understanding and the quantification of the WPD variability on various spatial and temporal scales are the main purposes of this study, in view to improve the MSL error budget. The dominant timescales of WPD variability and its correlation with Sea Level Anomaly (SLA) are examined. In these analyses, the atmospheric reanalysis ERA-Interim model from the European Centre for Medium-Range Weather Forecasts (ECMWF) is used to derive a global dataset of daily grids of WPD, spanning a 28-year period from January 1988 to December 2015. The Seasonal-Trend decomposition procedure based on Loess (STL) is used to extract precise WPD annual and interannual signals. Linear trends have been derived from the interannual time series and the contribution of each STL component was mapped globally, allowing the understanding of the WPD variability in spatial terms. The correlation between SLA and WPD is mapped and decomposed into seasons using monthly mean grids, for a period of 21-years, from January 1993 to December 2013.Aiming at inspecting the sensitivity of the results to the used data set, the WPD temporal analysis is extended to the data set provided by the Special Sensor Microwave Imager (SSM/I) and SSM/I Sounder (SSM/IS) Sensors. The WPD from SSM/I(S) is compared against those from the ERA-Interim and from the National Centers for Environmental Prediction (NCEP).Results show that climate phenomena, especially the El Niño Southern Oscillation (ENSO) are the cause for this high variability, since they affect the water vapour and temperature. The observed trends from ERA-Interim, computed globally and over ocean regions only, allow concluding that WPD is increasing with time by approximately 0.1?mm per year, and the maximum trends are observed for the Pacific North and Indian Oceans. High correlation between WPD and SLA is found over the western tropical Pacific.The comparison between WPD from SSM/I(S) and from ERA-Interim and NCEP, allows concluding that the trends computed using only the SSM/I(S) measurement points are substantially larger.     

飞行器用透波材料及天线罩技术研究进展

介绍了国内外飞行器用透波材料及天线罩的发展现状及应用需求,分析了在不同飞行马赫数、飞行时间、频带、功能等特殊环境下材料的性能,在此基础上提出了飞行器透波材料及天线罩的发展方向。     

微波双通带滤波器多项式综合技术

文章提出了一种新的微波双通带滤波器多项式综合技术,这种方法将频率转换与优化方法结合,与频率转换方法相比较,文章中提出的新方法不仅能够有效地综合出具有等波纹响应特性的对称双通带滤波器的s参数多项式,而且对于两个不对称度很高的双通带也同样有效。文章最后给出了相应的设计实例,验证了该方法对所有双通带多项式综合的有效性。     

基于遗传粒子群算法的模拟电路测试点选择

针对模拟电路测试点选择的特点,提出利用遗传粒子群算法与整数编码故障字典相结合的方法进行测试点选择。首先根据各测试点的数据建立整数编码故障字典,然后利用遗传粒子群算法选取最优测试点。将该方法应用于实际模拟滤波器的测试点选择,结果表明：利用该方法很容易求出模拟电路的全局最优测试点。     

星载合成孔径雷达的原理,组成和性能

对星载合成孔径雷达的工作原理及其特点、信号特征和分辩率，着重从物理要领上进行阐述。以加拿大Ｒａｄａｒｓａｔ为例，介绍了星载ＳＡＲ的组成原理，概述了各个子系统的功能，并生载合成孔径雷达的性能参数分成空间性能参数；辐射性能参数和技术性能参数三个方面进行了较详细的分析和介绍。     

固体火箭发动机喷焰微波衰减的研究

综述了国内外固体火箭发动机喷焰微波衰减的有关研究工作,包括喷焰微波衰减特性分析,固体推进剂组分对微波衰减的影响,微波衰减的抑制方法和喷焰微波衰减的计量技术.     

全红外光激发里德堡原子微波电场测量

基于高激发里德堡原子的微波电场测量技术与传统金属天线相比有诸多优越性,是未来微波电场高精度测量的重要方案之一。采用全红外光激发里德堡原子的方案不再依赖复杂而昂贵的短波长激光器,大大减小了激光器系统的体积与能耗。在三红外光级联激发里德堡铷原子的过程中,发现了中间态对应的双光梯形电磁诱导透明光学参数对三光激发里德堡态电磁诱导吸收峰信噪比具有重要影响,因此采用光失谐方法能很好地优化三光EIA光谱。利用微波场下的Autler-Townes分裂效应和标准天线方法对微波喇叭天线发射的微波电场实现精确的校准,并以此为基础通过超外差接收技术成功探测到本地场与信号场所形成的拍频信号,得到了拍频光电信号与信号场强度之间的线性关系。最终通过实验噪声基底的噪声功率谱得到三红外光里德堡铷原子微波测量的极限灵敏度为37.5(5.5) nV·■。采用三束红外光激发的方法为研制小型里德堡原子微波电场探测仪器奠定了物理基础。     

DFH-2A国内通信卫星天线系统

叙述了为国内电信服务的机械消旋卫星天线系统.该天线系统包括三部分:全向遥测遥控天线组件,定向通信天线和三信道无接触旋转关节.遥测遥控天线为双圆盘天线,辐射全向性方向图,圆极化.通信天线是收发共用单喇叭馈源偏置椭圆抛物面天线,辐射一个5°×8°的椭圆波束,恰好覆盖中国本土.三信道无接触旋转关节是一个同心三同轴线结构,形成三路传输信道.各同轴线旋转连接处有扼流槽.各信道的插入损耗为0.6～0.8dB,信道之间隔离优于50dB.     

微波与等离子体之间的相互作用

根据微波和等离子的基本理论以及它们之间相互作用的原理,建立了由微波能、谐振腔内电场、工质流场、等离子体平衡场等组成的轴对称偏微分方程组。通过对模型的计算,获得了放电管内等离子体区的形状、电场、电子浓度和温度场,以及气体温度场。     

大分子视黄基席夫碱盐微波吸收剂的制备

合成了一种大分子视黄基席夫碱盐微波吸收剂,通过元素分析,红外光谱（IR）,电子自旋共振波谱（ESR）等一系列测试手段对这种微波吸收剂的结构进行了鉴定,并对其介电常数,磁导率及密度进行了测试,对电磁参数的测试结果表明,该络合物具有较好的吸波性能。