Bright band height assignment with precipitation radar data based on multi-resolution analysis (MRA) of wavelet analysis

A method for reconstruction of cross-section of rainfall situations with precipitation radar data based on wavelet analysis of multi-resolution analysis (MRA) which allows extract a peak of the radar reflectivity is proposed in order to detect bright band height. It is found that the bright band height can be estimated by using the MRA with the basis of Daubechies wavelet family. It is also found that the boundaries in rainfall structure can be clearly extracted with MRA.     

Ka波段卫星ATM系统差错控制编码方案

Ka波段通信是当前卫星通信发展的热点 ,卫星异步传递模式 (ATM)技术代表了宽带数字卫星通信网络的研究方向 ,文章研究了适合Ka波段卫星ATM系统的差错控制编码方案。首先分析了卫星信道的特点以及对ATM信元传输所带来的影响 ,并给出了突发误码与信元丢失率 (CLR)关系的仿真曲线 ,然后讨论了六种具有代表性的卫星ATM差错控制编码方案。针对Ka波段宽带卫星通信的特点对六种方案进行了分析比较 ,其中的CASI/ALA以及RM Turbo方案为两种较好的选择。     

未来全球宽带无线通信系统构想

由于不断增长的宽带多媒体业务和移动性的需求,TCP／IP与卫星技术相互结合,逐渐成为构成下一代全球移动互联网系统的基础结构之一。文章从IP网及无线网的发展,详细介绍了各自的技术特点和发展趋势,在此基础上提出了全球宽带无线通信网互联互通模型。这对未来卫星通信的发展具有重要意义。     

一种星载高相位中心稳定度双频GPS天线

介绍一种用于星载的变形十字交叉振子圆极化天线,通过对普通十字交叉振子天线进行改进,展宽了天线的工作带宽,使该天线能同时工作在GPS的L1和L2两个频率上。该天线结构简单,除了支撑材料外,整个天线由金属构成,易于满足星载的环境要求。该天线具有很高的相位中心稳定度,在要求的波束范围内天线的相位中心稳定度小于2mm,达到了国外同类产品的水平。仿真及实测结果表明,设计实用、可行。文中还研究了天线相位中心的测试方法和数据处理方法,并应用到实际测试中。     

紧缩场超高频（UHF）天线测试方法的研究

针对CCR120／100紧缩场超高频（UHF）天线测试的问题，根据紧缩场的现有条件，给出了利用紧缩场进行UHF天线辐射特性测试的方法，以及进一步提高测试精度的方法，以满足卫星UHF频段天线辐射特性测试的需求。     

运载火箭测控系统技术与发展

针对中国新一代运载火箭发射轨道多样、外部环境日益复杂、上行控制和空间环境安全要求逐步提高等发展特点,以及高码率、高覆盖、高精度的测控需求,研究了天基测控、多音组合编码安控、高效遥测和测控数传一体化等几种运载火箭测控新技术的应用前景;从工程的角度,提出了中国运载火箭测控系统发展思路和天地一体化的测控体系结构;并就测控系统资源配置与使用模式、新型测控体制和测控手段、遥测和安控频段等重点发展方向简述了作者的观点。     

ALCATEL DVOR4000边带相位调整方法改进

对ALCATELDVOR4000型全向信标的边带相位调整方法进行了分析、推理，并结合实践提出了较好的调整方案。     

用输入数据符号加权减小MSK信号的带外功率

由于最小频移键控信号具有较为理想的功率谱特性，近年来已得到广泛关注，但在某些场拾它的带外能量泄漏不能满足实际需要。在此情况下可以对输入数据符号进行加权处理，从而得到一类ＭＳＫ信号这类ＭＳＫ信号仍为等幅波，相位仍保持连续。本文给出了这类信号功率谱的计算公式以及加权函数和功率谱的关系，并给出实例。     

Correlation of GPS signal fades due to ionospheric scintillation for aviation applications

Deep and frequent Global Positioning System (GPS) signal fading due to strong ionospheric scintillation is a major concern for GPS-guided aviation in equatorial areas during high solar activity. A GPS aviation receiver may lose carrier tracking lock under deep fading, and a lost channel cannot be used for position calculation until lock is reestablished. Hence, frequent loss of lock due to frequent fading can significantly reduce the availability of GPS aviation. However, the geometric diversity of the satellites can mitigate scintillation impact on GPS aviation depending on the correlation level of deep fades between satellites. This paper proposes a metric to measure the correlation level of two fading channels from the perspective of GPS aviation. Using this metric, the satellite-to-satellite correlation is studied based on real scintillation data. The low satellite-to-satellite correlation shown in this paper envisions notable availability benefit from the geometric diversity of satellites under strong scintillation. In addition, this paper proposes a way to generate correlated fading processes with arbitrary correlation coefficients. Using this correlated fading process model, the availability of Localizer Performance with Vertical guidance (LPV)-200 under severe scintillation scenarios is analyzed. The result emphasizes the importance of a fast reacquisition capability of an aviation receiver after a brief outage, which is not currently mandated by the aviation receiver performance standards.     

广域网接入技术及其应用

介绍接入网的概念和广域网接入技术的发展及现状，着重分析了常用接入技术的基本原理、特点及其应用。