2N次方广谱伪随机信号发生器及VHDL程序.doc

目 录 第一章 前言·························································································· 1 第二章 伪随机信号·············································································· 2 2.1 2n伪随机信号简介······································································· 2 第三章 伪随机信号的时域分析·························································· 3 第四章 伪随机信号发生器的VHDL描述········································ 8 4.1 用VHDL设计产生双频波··························································· 9 4.2 用VHDL设计产生三频波··························································· 9 4.3 主要构思及设计图····································································· 10 4.4 各种波的程序及波形································································· 14 第五章 结论························································································ 30 参考文献································································································ 31 致谢······································································································· 32 前言 伪随机信号处理最早是从空间工程和军事等应用中发展起来的，至今已有40多年的历史。在这些应用中，重点主要集中在寻求某种信号格式以及信号处理技术，以保证信息的完整性，尤其在受到干扰攻击的时候更是如此。随着数字移动通信系统的发展、对定位系统需求的持续增长以及集成电路集成度的日益提高，伪随机信号处理作为一种可行的技术在民用和商用系统中得到越来越多的应用。 伪随机序列通过设置数学乱源产生,它的伪随机性表现在预先的可确定性、可重复产生与处理,伪随机序列虽然不是真正的随机序列,但是当伪随机序列周期足够长时,伪随机序列具有随机序列的良好统计特性。伪随机序列广泛应用于密码学、扩频通讯、导航、集成电路的可测性设计等许多重要领域[3]。比如,密码学中伪随机序列通常被作为密钥,流密码中通过密钥流生成器产生性能优良的密钥流序列,使用该序列加密信息流得到密文序列,所以流密码的安全强度完全决定于密钥流序列的好坏。扩频通信中伪随机序列作为扩频码,利用伪随机序列码把基带信号的频谱进行扩展,形成相当带宽的低功率谱密度信号进行发射。使用不同的伪随机序列编码,不同通信用户可以在同一频段、同一时间工作,互不影响或影响极小。具有良好的伪随机特性的扩频编码对扩频通信及其技术的应用是非常重要的。基于伪随机序列具有的科学和社会价值, 对伪随机序列已经有了比较深入的研究。伪随机序列信号在雷达、遥控、遥测、通信加密和无线电测量系统领域有着广泛的应用。 第二章 伪随机信号简介 2n系列伪随机信号为中国工程院院士何继善发明和命名（He，jishan，1997，何继善，1998）。2n系列信号随着n的不同，在时间域上具有不同的波形，其频谱也相应的不同。但这些信号的频谱有一个共同的特点，就是它们的频谱在频率为2n共n个频率上大小基本相等，在这些频率上功率之和占了信号总平均功率的大部分，其余谐波含有的功率只占小部分，2n系列伪随机信号的名称也因此得来。单个伪随机信号根据n的取值命名为伪随机n频波。例如，当n取值为3、5、7、11时，将所对应的伪随机信号命名为伪随机三频波、伪随机五频波、伪随机七频波、伪随机十一频波。因此，2n系列伪随机信号是指无数个满足上述特点的信号的集合，伪随机n频波指的是2