精品外文翻译基于m序列的扩频通信系统的仿真设计外文翻译.docx

1、精品外文翻译基于m序列的扩频通信系统的仿真设计外文翻译中文字数7504字 届毕业设计外文翻译毕业设计题目:基于m序列的扩频通信系统的仿真设计 外文翻译题目:Spread Spectrum Techniques 专业: 班级: 姓名: 学号: 指导教师: Spread Spectrum Techniques By WikipediaAbstract:Spread-spectrum techniques are methods by which a signal (e.g. an electrical, electromagnetic, or acoustic signal ) generated

2、 in a particular bandwidth is deliberately spread in the frequency domain, resulting in a signal with a wider bandwidth. These techniques are used for a variety of reasons, including the establishment of secure communications, increasing resistance to natural interference and jamming, to prevent det

3、ection, and to limit power flux density (e.g. in satellite downlinks).History Frequency hopping:The concept of frequency hopping was first alluded to in the 1903 U.S. Patent 723,188 and U.S. Patent 725,605 filed by Nikola Tesla in July 1900. Tesla came up with the idea after demonstrating the worlds

4、 first radio-controlled submersible boat in 1898, when it became apparent the wireless signals controlling the boat needed to be secure from being disturbed, intercepted, or interfered with in any way. His patents covered two fundamentally different techniques for achieving immunity to interference,

5、 both of which functioned by altering the carrier frequency or other exclusive characteristic. The first had a transmitter that worked simultaneously at two or more separate frequencies and a receiver in which each of the individual transmitted frequencies had to be tuned in, in order for the contro

6、l circuitry to respond. The second technique used a variable-frequency transmitter controlled by an encoding wheel that altered the transmitted frequency in a predetermined manner. These patents describe the basic principles of frequency hopping and frequency-division multiplexing, and also the elec

7、tronic AND-gate logic circuit.Frequency hopping is also mentioned in radio pioneer Johannes Zennecks book Wireless Telegraphy (German, 1908, English translation McGraw Hill, 1915), although Zenneck himself states that Telefunken had already tried it several years earlier. Zennecks book was a leading

8、 text of the time, and it is likely that many later engineers were aware of it. A Polish engineer, Leonard Danilewicz, came up with the idea in 1929.Several other patents were taken out in the 1930s, including one by Willem Broertjes (Germany 1929, U.S. Patent 1,869,695, 1932). During World War II,

9、the US Army Signal Corps was inventing a communication system called SIGSALY for communication between Roosevelt and Churchill, which incorporated spread spectrum, but due to its top secret nature, SIGSALYs existence did not become known until the 1980s.The most celebrated invention of frequency hop

10、ping was that of actress Hedy Lamarr and composer George Antheil, who in 1942 received U.S. Patent 2,292,387 for their Secret Communications System. Lamarr had learned about the problem at defense meetings she had attended with her former husband Friedrich Mandl, who was an Austrian arms manufacture

11、r. The Antheil-Lamarr version of frequency hopping used a piano-roll to change among 88 frequencies, and was intended to make radio-guided torpedoes harder for enemies to detect or to jam. The patent came to light during patent searches in the 1950s when ITT Corporation and other private firms began

12、 to develop Code Division Multiple Access (CDMA), a civilian form of spread spectrum, though the Lamarr patent had no direct impact on subsequent technology. It was in fact ongoing military research at MIT Lincoln Laboratory, Magnavox Government & Industrial Electronics Corporation, ITT and Sylvania

13、 Electronic Systems that led to early spread-spectrum technology in the 1950s. Parallel research on radar systems and a technologically similar concept called phase coding also had an impact on spread-spectrum development.Commercial useThe 1976 publication of Spread Spectrum Systems by Robert Dixon,

14、 ISBN 0-471-21629-1, was a significant milestone in the commercialization of this technology. Previous publications were either classified military reports or academic papers on narrow subtopics. Dixons book was the first comprehensive unclassified review of the technology and set the stage for incr

15、easing research into commercial applications.Initial commercial use of spread spectrum began in the 1980s in the US with three systems: Equatorial Communications Systems very small aperture (VSAT) satellite terminal system for newspaper newswire services, Del Norte Technologys radio navigation syste

16、m for navigation of aircraft for crop dusting and similar applications, and Qualcomms OmniTRACS system for communications to trucks. In the Qualcomm and Equatorial systems, spread spectrum enabled small antennas that viewed more than one satellite to be used since the processing gain of spread spectrum eliminated interference. The Del Norte system used the high bandwidth of spread spectrum to improve location accuracy.In 1981,