pcm通信系统设计

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1、课程设计任务书学生姓名：骆准专业班级：电信0601班指导教师：陈永泰作单位：信息工程学院题目：PCM通信系统设计初始条件：具备通信课程的理论知识；具备模拟与数字电路基本电路的设计能力；掌握通信电路的设计知识，掌握通信电路的基本调试方法；自选相关电子器件；可以使用实验室仪器调试。要求完成的主要任务：（包括课程设计工作量及其技术要求，以及说明书撰写等具体要求）1、PCM码速率128KB，两路时分复用，通信双方有线连接，语音信号无明显失真，采用A律压缩13折线芯片；2、系统时钟信号频率2.048MHZ，时隙同步信号频率

2、为8KHZ；3、选用相应合适的芯片，设计确定电路形式，对单元电路和整体系统进行计算、仿真验证。4、进行系统仿真，调试并完成符合要求的课程设计书。时间安排：二十二周一周，其中3天硬件设计，2天硬件调试指导教师签名：年月日系主任（或责任教师）签名：年月日目录摘要·····························································I1PCM原理·······················································11.1PCM

3、系统组成················································11.2抽样·······················································21.3量化·······················································21.4编码·······················································32时分复用原理················

4、···································43实验电路图·····················································73.1编译码芯片介绍··············································73.2引脚图·····················································73.3PCM编译码电路···································

5、··········84仿真图························································115心得体会······················································13参考文献························································14致谢····························································1

6、51PCM原理1.1PCM系统组成干扰音频信号编码量化信道译码低通滤波音频信号抽样图1.1PCM通信系统方框图1.2抽样低通抽样定理指出，一个频带受限信号m(t)，如果它的最高频率为fh，则可以唯一地由频率等于或大于2fh的样值序列所决定。在满足抽样定理的条件下，抽样信号保留了原信号的全部信息。并且，从抽样信号中可以无失真地恢复出原始信号。音频信号频谱如图1.2。因为对时域信号进行采样相当于将时域信号按抽样抽样频率为周期进行周期延扩，因此需要在抽样后得到的信号后一级加上一个低通滤波器，将音频信号滤出。抽样后信号频

7、谱如图1.3。1.2音频信号的频谱1.3抽样后的频谱由于语音信号的频率范围为300～3400HZ,通常将语音信号通过一个3400Hz低通滤波器（或通过一个300～3400Hz的带通滤波器），限制语音信号的最高频率为3400Hz，这样可以用频率大于或等于6800Hz的样值序列来表示。抽样分为自然抽样和平顶抽样。自然抽样是在抽样脉冲持续期间，样值幅度随输入信号变化而变化。平顶抽样是抽样值的幅度为抽样时刻信号的瞬时值，在抽样脉冲持续期间样值幅度。1.3量化量化是把经过抽样得到的瞬时值将其幅度离散，即用一组规定的电平，把

8、瞬时抽样值用最接近的电平值来表示。一个模拟信号经过抽样量化后，得到已量化的脉冲幅度调制信号，它仅为有限个数值。因此量化后信号是离散的。量化分为均匀量化和非均匀量化。均匀量化是把输入信号的量化范围按等间隔分割的量化。均匀量化中，每个量化区间的量化电平均取在各区间的中点。均匀量化的信号的动态范围受到较大的限制，小信号的信噪比小，由于门限效应，编码时的位数相对较多，设备较复杂。