dpsk通信系统仿真论文_-西安理工.doc

DPSK通信系统仿真 院系：西安理工大学高科学院 班级：11级电子信息工程 学号 姓名：陈振波 教师：刘高辉 2015年4月7日 目录 1 设计题目························································3 2 设计要求························································3 3 设计原理························································3 3.1 DPSK调制····················································3 3.2 DPSK解调····················································4 4 设计流程························································5 5 代码实现························································5 5.1 基带信号的获取···············································5 5.2 差分编码·····················································6 5.3 DPSK调制···················································7 5.4 AWGN信道···················································8 5.5 限噪处理·····················································8 5.6 差分相干解调·················································9 5.4 AWGN信道··················································11 5.7 功率谱密度图的绘制 6 测试结果·······················································12 6.1 调制解调正确性的测试········································12 6.2 系统抗噪性能的测试··········································14 7 总结····························································17 8 心得体会·······················································17 附：完整代码·····················································18 1 设计题目 用MATLAB仿真DPSK通信系统 2 设计要求 基本参数如下： Fc=1800Hz Rb=1200bps 考虑加入AWGN信道，Eb/N0=20dB 自定义一小段信息序列 结果要求： 绘制各阶段信号波形 绘制信号的PSD 3 设计原理 二进制差分相移键控常简称为二相相对调相，记为2DPSK。它不是利用载波相位的绝对数值传送数字信息，而是用前后码元的相对载波相位值传送数字信息。所谓相对载波相位是只本码元初相与前一码元初相之差。 3.1 DPSK调制 DPSK方式即是利用前后相邻码元的相对载波相位值去表示数字信息的一种方式。例如，假设相位值用相位偏移表示 图3-1 2PSK及2DPSK信号的波形 2DPSK的产生基本类似于2PSK，只是调制信号需要经过码型变换，将绝对码变为相对码。2DPSK产生的原理框图如图2-2所示[1]，图（a）为模拟调制法，图（b）为键控法。 (a) 模拟调制法 (b) 键控法 图3-2 2DPSK信号的调制原理图 从上面分析可见，无论接收信号是2DPSK还是2PSK信号，单从接收端看是区分不开的。因此2DPSK信号的功率谱