M序列的产生和性能分析

摘要

不确定度

在扩频函数中，伪随机信号不但要求具有尖锐的互相关函数，互相关函数应接近于零，而且具有足够长的码周期，以确保抗侦破、抗干扰的要求；由足够多的独立地址数，以实现码分多址的要求。M序列是伪随机序列的一种，可由m序列添加全0状态而得到。m序列与M序列对比得出在同级移位寄存器下M序列的数量远远大于m序列数量，其可供选择序列数多，在作跳频和加密码具有极强的抗侦破能力。

本文在matlab中的Simulink下用移位寄存器建立了4级、5级、6级M序列的仿真模型，进行了仿真，画出其时域图、频谱图、互相关性图。通过时域图和频域图可看出，经过扩频后的信号频带明显的被扩展；由M序列互相关性图，得出M序列有较小的互相关性，较强的自相关性，但相关性略差于m序列。最后，本文又将M序列应用于CDMA扩频通信仿真系统中，得到下列结论：当使用与扩频时相同的M序列做解扩操作与用其他序列做解扩的输出有巨大的差别。使用相同的序列进行解扩时系统输出值很大，而使用其他序列解扩时输出值在零附近变化。这就是扩频通信的基础。

关键词2012年广东高考语文作文：伪随机编码, 扩频通信自相关函数，互相关函数

M SEQUENCE GENERATION AND PERFORMANCE ANALYSIS

足菌肿ABSTRACT

In spread-spectrum communication, pseudo-random sequence must have high autocorrelation value, low cross correlation, long code period and lots of dependent address to satisfy code division multiple access(CDMA). 伟力糖尿病仪M sequence is one kind of the pseudo-random sequences. It can be may obtained through adding entire 0 states to m sequence. The number of M sequence is greater than the m-sequence under the same level shift register. It may supply the more choice. The M-sequence is often applied to the frequency hopping and adds the password to have greatly strengthened anti- solves the ability.城市信报

At first, M sequences which has n=4、5、7 levels of shift registers are produced under Si无边界网络

mulink of Matlab. The time domain chart, the spectrograph, the mutual correlation chart are plotted. Through the time domain chart and the spectrograph, we could see how the bandwidth of the information signal is expanded. The pseudo-random symbol speed rate higher noise signal frequency spectrum is proliferated widely, the output power spectrum scope is lower. This can explain the spread-spectrum communication system principle from the frequency range. Through the M sequence’s auto correlation chart we can see that the auto correlation of M-sequence is quite good but is inferior to the m sequence. Finally, the M sequence is applied to the code division multiple access (CDMA) communication system. This is the spread-spectrum communication foundation.

KEY WORDS：Pseudo-random code, auto-correlation, cross-correlation

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