资源卫星接收站高分辨率实时快视处理

本文较系统地阐述了资源卫星地面接收站对遥感图像的高分辨率实时快视处理方法。文中提出了主要针对接收美国Landsat卫星TM数据的实时快视系统方案,其具有1024×1024显示的高分辨率,兼顾了多功能、低成本、简易性和对不同类型遥感数据快视处理的兼容性等特征,为我国已建的和即将兴建的资源卫星接收站配置实时快视系统提供了一条有效途经。     

全球移动卫星系统投资风险分析

在人们普遍给予全球移动通信系统高技术高效益评价的同时，其高投入高成本所带来的高负险也是不容忽视的。根据市场竞争的观点它同样面临着行为内和行业外多种力量的竞争。特别是近年来地面无线通信的迅速发展对该产业的怅惘敢巨大冲击。     

Development of a prototype,experimental single-channel sequencing navstar gps receiver: Part I—Hardware implementation

Late in 1988 the Navstar GPS satellite navigation operational phase is planned to commence, offering world-wide, continuous and precise position-fixing and timing information to observers on land, sea, air and in space. This paper describes the development of a particular type of Navstar receiver—a single-channel, single-frequency, sequencing C/A code unit—and results of various tests carried out on the present phase-II satellite constellation. Part I of the paper deals essentially with the NAVSTAR satellite system and receiver hardware implementation, whereas Part II concentrates on receiver software and system performance.     

前馈电路的性能分析

本文运用Volterra级数分析了采用前馈技术,使微波功率放大器线性改善的程度。给出前馈电路实验结果。     

A statistical model of FM-TV spectra for satellite interference and distortion prediction

The requirement for a model of FM-TV spectra in the planning procedure of satellite communication systems is introduced. Based on long-term measurements of live TV channels, statistical properties of video spectra are examined and probability distributions for the luminance and chrominance components are proposed. The spectrum of the frequency-modulated signal is then derived, and signal distortion due to bandlimiting is calculated. Adjacent and cochannel interference effects are also investigated, with example cases illustrating influences of subcarrier loading and energy dispersion. The proposed model, which describes FM-TV spectra in terms of random variables, makes it possible to examine relative effects of system parameters, and will, therefore, be of benefit in the planning of new satellite services.     

Spectrum planning and performance evaluation between heterogeneous satellite networks

A new network has been recently proposed for the provision of fixed broadband services via high altitude platform stations (HAPS) in the 48/47 GHz band. One of the critical issues of this technology is spectrum sharing with the fixed satellite service. This paper examines the effect of Earth-to-stratosphere co-channel interference produced by ground stations of HAPS network to geostationary orbit (GEO) satellite receivers and proposes an interference-to-noise (I/N) calculation model for the evaluation of the current HAPS ground stations power characteristics set by ITU-R. Analytical and simulation results for archetypal systems in realistic scenarios indicate that efficient use of the spectrum shared between heterogeneous HAPS and Fixed Satellite Networks is feasible. Certain consideration is needed prior to the HAPS network development in suburban areas for latitudes from 55° to 65°, and in rural areas for latitudes from 60° to 75°.     

地球站天线极化夹角的调整

本文闸明了地球站天线产生极化夹角的原理;导出了计算极化夹角的公式;给出了全国各地具有代表性的一些地球站极化夹角值,供有关研制人员和操作人员调整地球站天线消除极化夹角影响之参考。     

Reliability analysis of an Attitude Determination and Control System (ADCS) through the RAMSAS method

Reliability analysis of modern large-scale systems is a challenging task which could benefit from the jointly exploitation of recent model-based approaches and simulation techniques to flexibly evaluate the system reliability performances and compare different design choices. In this context, RAMSAS, a model-based method which supports the reliability analysis of systems through simulation by combining the benefits of popular OMG modeling languages with wide adopted simulation and analysis environments, has been recently proposed. This paper shows the effectiveness of RAMSAS through a real case study concerning the reliability analysis of an Attitude Determination and Control System (ADCS) of a satellite.     

THe callingSM network: A global wireless communication system

There is a very large demand for basic telephone service in developing nations, and remote parts of industrialized nations, which cannot be met by conventional wireline and cellular systems. This is the world' largest unserved market. We describe a system which uses recent advances in active phased arrays, fast-packet switching technology, adaptive routeing, and light spacecraft technology, in part based on the work of the Jet Propulsion Laboratory and on recently-declassified work done on the Strategic Defense Initiative, to make it possible to address this market with a global telephone network based on a large low-Earth-orbit constellation of identical satellites. A telephone utility can use such a network to provide the same modern basic and enhanced telephone services offered by telephone utilities in the urban centres of fully-industrialized nations. Economies of scale permit capital and operating costs per subscriber low enough to provide a service to all subscribers, regardless of location, at prices comparable to the same services in urban areas of industrialized nations, while generating operating profits great enough to attract the capital needed for its construction. The bandwidth needed to support the capacity needed to gain these economies of scale requires that the system use K_a-band frequencies. This choice of frequencies places unusual constraints on the network design, and in particular forces the use of a large number of satellites. Global demand for basic and enhanced telephone service is great enough to support at least three networks of the size described herein. The volume of advanced components, and services such as launch services, required to construct and replace these networks is sufficient to propel certain industries to market leadership positions in the early 21st Century.     

馈源阵面排列对偏置多波束天线特性的影响

以３７单元馈源阵为例,就用于卫星移动通信系统中的偏置多波束天线进行分析探讨：在原有两种馈源阵阵面排列形式的基础上,又提出了第三种排列形式,即馈源阵的球面排列形式,并对这三种形式下偏置多波束天线的远场特征进行了计算比较,得出了一些有益的结论;另外,将馈源阵阵面适当地偏离焦点也可使多波束天线的远场特性得以改善。