碼分多址通信系統(tǒng)、擴(kuò)頻通信外文翻譯-其他專業(yè)-展示頁(yè)
2025-01-31 03:02本頁(yè)面
【正文】 on’s basic characteristics, is used to transmit information to the signal bandwidth(W) is far greater than practical required minimum(effective) bandwidth ( F? ),as the radio of processing gain PG . FWGP ?? / As we well know,the ordinary AM,FM,or pulse code modulation,GP value in the area more than 10 times,collectively,the “narrowband munication”,and spreadspectrum munication GP values as hundred or even thousands of times, can be called “broadband munication”. Due to the spreadspectrum signal,it is very low power transmitters,transmission space mostly drowned in the noise,it is difficult to intercepted by the other receiver ,only spreading codes with the same (or random PN code) receiver, Gain can be dealt with ,and despreading resume the original signal. The technology superiority of spreadspectrum munication. Strong antiinterference, bit error rate is low. As noted above, the spread spectrum munication system due to the expansion of the transmitter signal spectrum, the receiver despreading reduction signal produced spreading gain, thereby greatly enhancing its interference tolerance. Under the spreading gain, or even negative in the signaltonoise ratio conditions, can also signal from the noise drowned out Extraction, in the current business munications systems, spread spectrum munications systems, spread spectrum munication is only able to work in a negative signaltonoise ratio under the conditions of munication . Antimultipath interference capability, increase the reliability of system. Spreadspectrum systems as used in the PN has a good correlation, correlation is very weak. Different paths to the transmission signal can easily be separated and may in time and realignment phase, formation of several superimposed signal power, thereby improving the system’s performance to receive increased reliability of the system. Easy to use the same frequency, improving the wireless spectrum utilization. Wireless spectrum is very valuable,although longwave microwave have to be exploited, and still can not meet the needs of munity. To this end, countries around the world are designed spectrum management, users can only use the frequency applications,rely on the channel to prevent the division between the channel interference. Due to the use of spreadspectrum munication related receive this hightech,low signal output power(“a W,as a general100mW),and will work in the channel noise and thermal noise in the background,easy to duplicate in the same area using the same frequency,can now all share the same narrowband frequency munication resources. Spreadspectrum munication is digital munication,particularly for digital voice and data transmission with their own encryption, only in the same PN code munication between users, is good for hiding and confidential in nature, facilitating munication business. Easy to use spreadspectrum CDMA munications, voice pression and
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