卫星通信

with the development of satellite navigation communication,antenna is a very important unit,performance of the satellite navigation communication system is affected by it partly.a new type of bifilar helix for satellite navigation communication system is introduced,and the traving-wave bifilar helix is analyzed briefly.meanwhile,the design and the test results are given.the results show that the antenna possesses excellent circular hemispherical beam with wide angle circular polarization and better impedance match,and has a compact structure and high integration.it can be applied in caps systems successful.

小 摘要：随着卫星导航通信技术的迅速发展，天线作为卫星导航通信系统中的重要部分，在一定程度上决定着卫星导航通信系统的性能。介绍一种用于卫星导航通信系统的双臂螺旋天线，讲述爬行波式螺旋天线的设计过程，并给出最终测试结果。结果表明，该天线具有优良的圆对称半球波束，良好的广角圆极化特性和优良的阻抗匹配特性，其结构简单、紧凑，为通信入站回传提供了一种优良的选择。

Under the leadership of the National Headquarters for Earthquake Disaster Mitigation, as of 8:00 on May 19th, the telecommunications sector has sent out 26,000 people for repairing, dispatched 391 emergency telecoms vehicles, 979 satellite telephones, 7422 power generators, over 2000 sets of emergency communications equipment and equipment for repairing, 1000 cells specifically for the satellite telephones and 150 sets of field power supply equipment.

在国务院抗震救灾指挥部的统一指挥下，截至5月19日8时，通信行业已出动抢修人员2.6万人、调动391台应急通信车、979部卫星电话、7422台发电油机、2000多套其它应急通信和抢修设备，1000块卫星电话专用电池，150套野外电源装备，累计调用卫星转发器资源496 MHz，发送应急提示和抢险指导等方面的短信9亿条。

The communication systems wildly used nationally and internationally, such as audio frequency wire communication, carrier-current communication, micro-wave communication, optic-fiber communication, expanding frequency communication and satellite relay communication, are investigated in detail. The different communication systems used in Changsha County electric power systems are analysed in detail.

对目前国内外使用较多的一些通信方式如音频线通信、载波通信、微波通信、光纤通信、扩频通信、卫星帧中继通信等进行了较为深入的分析和研究；对目前长沙电力局正在使用的变电站与调度端的通信方式——进行性价比方面的分析比较，综合以上，得出了最为合适的变电站到调度端的通信方式。

The data acquisition of the valve chamber equipment is implemented and the mobile satellite communication technique is used to transfer data between the valve chambers and the remote control center in the system.

本文研究的天然气管线阀室设备远程监控系统，实现了阀室现场的数据采集，并采用移动卫星通信技术将现场数据传输到远程监控中心，中心端可对阀室设备进行远程操作和调度监测，为阀室设备提供了实时可靠的远程监控手段。

Firstly, the characteristics of satellite networks are analyzed and on the basis of the analysis, two SPN models for a single-layered LEO satellite network under half duplex mode and a double-layered satellite network under full duplex mode are constructed respectively.

首先分析了卫星网络的特点，并在此基础上建立了半双工通信模式下LEO单层卫星网络的SPN模型、全双工通信模式下LEO/MEO双层卫星网络的SPN模型。

The idea was two decades ahead of its time, and helped to attach his name to the geostationary orbit above the equator.

他的想法先于卫星通信时代20年，赤道上的地球同步卫星轨道因此以他的名字命名。

Like all JTRS Operational Requirement Document waveforms in the 2 MHz to 2 GHz frequency range, the UHF SATCOM and HF waveforms can run in any of the GMR system's four reprogrammable Universal Transceivers.

同所有联合战术无线电波形需求在2MHz到2GHz之间一样，超高频卫星通信和高频波形能够在任何车载地基移动无线电系统的四重编程通用收发器中运行。

In satellite communications the received signals are amplified and retransmitted at a different frequency.

在卫星通信中，把接收到的信号加以放大，然后以另一频率重新发送出去。参阅responder。

The performance analysis and simulation of coding schemes based on the modeling Ka-band fixed satellite channel have been presented.

在建立了Ka频段固定卫星通信信道模型的基础上，对几种编码方式的性能进行了分析与仿真。

A model of Ka-band fixed satellite communication channel and a corresponded simulation system with the Turbo coding scheme are created.

最后，利用Ka固定卫星通信信道模型对该Turbo码方案性能进行了仿真。

It has been put forward that there exists single Ball point and double Ball points on the symmetrical connecting-rod curves of equilateral mechanisms.

从鲍尔点的形成原理出发，分析对称连杆曲线上鲍尔点的产生条件，提出等边机构的对称连杆曲线上有单鲍尔点和双鲍尔点。

The factory affiliated to the Group primarily manufactures multiple-purpose pincers, baking kits, knives, scissors, kitchenware, gardening tools and beauty care kits as well as other hardware tools, the annual production value of which reaches US$ 30 million dollars.

集团所属工厂主要生产多用钳、烤具、刀具、剪刀、厨具、花园工具、美容套等五金产品，年生产总值3000万美元，产品价廉物美、选料上乘、质量保证，深受国内外客户的青睐