星载雷达高度计信号处理

本文研究了星载雷达高度计全去倾斜模型下的次最佳最大似然估值(Suboptimal Maximum Likelihood Estimation,SMLE)算法和实现途径。重点讨论了回波起伏和接收机噪声对高度和斜率两个参数估值精度的影响,得出了一些简单明了的结论。仿真结果验证了这些结论的正确性。     

由多台全站仪组成的馈源舱位姿动态测量系统

介绍了大射电望远镜 FAST光机电一体化的创新设计。给出了通过测量馈源舱不共线三点的空间坐标来解算舱体位置和姿态的方法。提出以先进的高精度动态跟踪测量仪器徕卡 TCA2 0 0 3全站仪为基本测量单元 ,组合六台TCA2 0 0 3为一套馈源舱位姿动态测量系统。由于系统的测量精度可达到 1mm,因此不仅为馈源舱的闭环控制提供了检测手段 ,而且可应用 Stewart平台精调系统所提供的舱体位姿信息进行逆运动学模型计算。     

A dual-frequency GNSS sensor for space applications

High-performance laboratory breadboards of a dual-frequency global navigation satellite system (GNSS) receiver have been developed at the Institute of Satellite Navigation at the University of Leeds (ISN) for a number of years under a European Space Agency (ESA) programme. The main objective of these breadboards is to serve as development tools for receiver signal-processing research in view of scientific applications of GNSSs. Some of these applications will be realized by means of receivers embarked on satellites in low earth orbit (LEO) as part of on-going and future ESA programmes and will include precise orbit determination, radio occultation measurements and measurements of the parameters characterizing GNSS signals reflected at the sea surface. The principal application for which the signal-processing developments described in this paper have been targeted is radio occultation. During an occultation event the GNSS signal encounters a challenging environment. Substantial Doppler dynamics occur during a measurement, due to the effect of sharp gradients of the refraction index. Signal attenuation and deep fading caused by multipath propagation are also encountered. The areas of concern are the acquisition and tracking of signals in high dynamics and at low carrier-to-noise ratios (C/N₀), and also the performance of tracking the GPS P code without full knowledge of the spreading code, as dual-frequency atmospheric measurements are crucial to this application. © 1998 John Wiley & Sons, Ltd.     

Dynamical properties of rainfall for performance assessment of earth/space communication links at Ku and Ka bands

Knowledge about the dynamic characteristics of rainfall rate and rainfading is of vital importance both for studies on the physical interpretation and modelling of the phenomena and for ancillary studies to counteract rain-induced effects by incorporating some changes in communication system parameters. This paper presents the dynamical characteristics of rainfall observed over Guwahati, India. Using a statistical procedure, an empirical model which predicts characteristic features of rainfading at the Ku and Ka bands is described. The fade inter-event gap statistics as a function of attenuation are discussed for widespread rain and thunderstorms separately. The observed and predicted results are compared with observations made by other investigators. As future communication systems using the Ku and Ka bands are being planned in India and other parts of Southeast Asia (e.g. Measat-I, Thaicom3, AsiaSat3), the results of this study may be used to predict rainfading properties. This study is the first of its kind over India. © 1998 John Wiley & Sons, Ltd.     

并行多信道软件无线电接收机仿真

讨论了软件无线电接收机的基本理论:信道划分和解调算法。在此基础上研究了下变频技术和低通滤波技术在并行多信道接收机中的应用,提出了采用软件无线电中的FM和AM解调方式解调信号,并完成了软件无线电接受机的系统仿真。     

一种跳频图案同步方法

针对战术跳频电台通信同步问题,在分析若干跳频同步方法的基础上提出了一种组合同步方法,并将收发双方维护的同步头频率组从一维扩展至二维,增强了同步头频率的抗干扰性.性能分析表明,此方法同步时间短、同步概率高,适用于战术跳频电台.     

DAB与DRM数字广播关键技术与发展综述

介绍了数字广播DAB和DRM系统,探讨了广播由模拟向数字发展的缘由及技术要点。对于两种数字广播系统DAB和DRM,依次就其国内外发展动态、与传统广播相比较的各自改进的优点、关键技术等进行比较分析。重点深入介绍DAB与DRM系统各自发射接收原理,为技术需求做准备,并讨论数字广播发展前景及推广的实际意义。     

DRM接收芯片信道译码器的ASIC设计

将MSD技术成功地应用于DRM接收芯片信道译码器的ASIC设计中,作为一次近百万门级的集成电路设计实践,该成果具有良好的可配置和可重用性,设计的信道译码器在0.18μm工艺下时钟约束可达50MHz,占用面积2282707.5μm2,相当于377303数目的与非门。     

无线EH认知物联网网络资源分配研究

由于5G技术的快速发展,基于能量采集的认知物联网(Internet of things,IOT)具有很大的应用前景.针对无线物联网网络中存在的"doubly-near-far"问题,考虑在认知物联网网络中将能量采集与信息接收站分开管理,提出了一个基于能量采集的异构认知物联网网络模型,实现用户能效的最大化.此外,该模型不...     

射频磁控溅射制备纳米TiO2薄膜的光电化学行为

在室温下采用射频磁控溅射法制备了纳米晶粒的TiO2薄膜,用循环伏安法研究了ITO/TiO2薄膜电极的光电化学行为,并测量了相应TiO2薄膜的亲水性与光催化能力.结果表明,在室温下制备的TiO2薄膜为无定形结构,当退火温度超过400 ℃时转化为锐钛矿结构.在400 ℃下退火的TiO2薄膜具有良好的亲水性和光催化能力. TiO2薄膜电极用254 nm的紫外光照射一定时间后会产生新的氧化峰,且随着光照时间的增加,峰电流也增加.初步认为用紫外光照射一定时间后, TiO2薄膜的循环伏安图的氧化峰属于光生的Ti3＋,而光致亲水性可能与Ti3＋的生成有关.