抽样定理实验报告

抽样定理实验报告 实验十一 抽样定理 学生姓名 *** 学 号 *** 专业班级 *** 学 院 *** 完成时间 ***年*月 adership: Luo Mingjun, rectification time: before September 25th, insist for a long time) 1, 2, to further improve research, solve thoroughly, not solid, the effect is not obvious. The major issues and enterprises it is a matter of security bureau year development, the vital interests of the problem, determine the research topic, by members of the Party led research. Basic research to see the truth, to the truth, do not say hello, not pre arranged. After the investigation to submit the research report. 3, insist on grassroots party members take the lead in implementing the line. <. In the construction of work style building long-term mechanism views > and < on the depth of the grassroots, the people, promoting harmony activities notice >, more mines and enterprises, solve the masses of grassroots leaders, mine is not enough. 4, contact a crowd. Combined with the "grassroots cadres contact farmers" activities and each cadres to contact a people, by 一、实验目的 1、了解电信号的采样方法与过程以及信号恢复的方法。 2、验证抽样定理。 二、实验仪器 1、20M双踪示波器一台。 、信号与系统实验箱。 2 三、原理说明 1、离散时间信号可以从离散信号源获得，也可以从连续时间信号抽样而得。抽样信号 可以看成连续信号和一组开关函数的乘积。是一组周期性窄脉冲，见图，，ftf，，ts，，ts，，ts 111-1，T称为抽样周期，其倒数称抽样频率。 f,SsTS s，，t tTs, 图11-1 矩形抽样脉冲 对抽样信号进行傅里叶分析可知，抽样信号的频率包括了原连续信号以及无限个经过平移的原信号频率。平移的频率等于抽样频率及其谐波频率、„„。当抽样信号是f2f3fsss ，，sinx周期性窄脉冲时，平移后的频率幅度按规律衰减。抽样信号的频谱是原信号频谱x 周期的延拓，它占有的频带要比原信号频谱宽得多。 2、正如测得了足够的实验数据以后，我们可以在坐标纸上把一系列数据点连起来，得到一条光滑的曲线一样，抽样信号在一定条件下也可以恢复到原信号。只要用一截止频率等于原信号频谱中最高频率f的低通滤波器，滤除高频分量，经滤波后得到的信号包含了原n 信号频谱的全部内容，故在低通滤波器输出可以得到恢复后的原信号。 3、但原信号得以恢复的条件是f,2Bf，其中为抽样频率，B为原信号占有的频带ss f,2B宽度。而为最低抽样频率又称“奈奎斯特抽样率”。当时，抽样信号的频f,2Bsmin 谱会发生混迭，从发生混迭后的频谱中我们无法用低通滤波器获得原信号频谱的全部内容。 f,2B在实际使用中，仅包含有限频率的信号是极少的。因此即使，恢复后的信号失真还s f,2Bf,2B是难免的。图11-2画出了当抽样频率(不混叠时)及当抽样频率(混叠ss时)两种情况下冲激抽样信号的频谱。( a) 连续信号的频谱 F，，,f，，t 1 t,,,,00mm adership: Luo Mingjun, rectification time: before September 25th, insist for a long time) s contact farmers" activities and each cadres to contact a people, bycadred enterprises, solve the masses of grassroots leaders, mine is not enough. 4, contact a crowd. Combined with the "grassroots term mechanism views > and < on the depth of the grassroots, the people, promoting harmony activities notice >, more mines an-g longt. 3, insist on grassroots party members take the lead in implementing the line. <. In the construction of work style buildinarch to see the truth, to the truth, do not say hello, not pre arranged. After the investigation to submit the research reporrese ar development, the vital interests of the problem, determine the research topic, by members of the Party led research. Basicsolve thoroughly, not solid, the effect is not obvious. The major issues and enterprises it is a matter of security bureau ye 1, 2, to further improve research, 2 实验十一 抽样定理 b() 高抽样频率时的抽样信号及频谱(不混叠) ,,2,sm F，，,sf，，t1s Ts t,,,,0T,,,s0ssmm () 低抽样频率时的抽样信号及频谱(混叠) ,,2,csm 图11-2 抽样过程中出现的三种情况 实验中选用三种抽样频率对连续信号进行抽样，以验证抽f,2B,f,2B,f,2Bsss 样定理——要使信号采样后能不失真地还原，抽样频率必须大于信号频率中最高频率的fs 两倍。 4、为了实现对连续信号的抽样和抽样信号的复原，可用实验原理框图11-3的 方案 气瓶 现场处置方案 .pdf气瓶 现场处置方案 .doc见习基地管理方案.doc关于群访事件的化解方案建筑工地扬尘治理专项方案下载 。除选用足够高的抽样频率外，常采用前置低通滤波器来防止原信号频谱宽而造成抽样后信号频谱的混叠。但这也会造成失真。如实验选用的信号频带较窄，则可不设前置低通滤波器。本实验就是如此。 抽低 通 信 号 样滤 波 输 入 门 抽 样 脉 冲 图11-3 抽样定理实验方框图 四、实验内容及步骤 1、按下总电源开关，将函数信号发生器产生的正弦波或三角波，送入抽样器，即用跳线将函数信号发生器的输出端与本实验模块的输入端相连，观察经抽样后的正弦波或三角波信号。正弦波的频率一般不超过1KHz(三角波要更低一些)，幅度(峰值)为2V左右，为便于观察，抽样信号频率一般选择50HZ,400HZ的范围，而抽样脉冲的频率则是通过电位器W501来调节的。 2、若使用外接信号源，应将外接信号源的地与本实验箱的地相连，并将信号源的输出端接入本实验模块的输入端。 3、各测试点的波形分别为: GND :接地端; TP501:输入信号的波形; TP502:本地输出的抽样脉冲; TP503:经反相后的抽样脉冲; TP504:抽样信号输出; adership: Luo Mingjun, rectification time: before September 25th, insist for a long time) contact a people, bys to ders, mine is not enough. 4, contact a crowd. Combined with the "grassroots cadres contact farmers" activities and each cadregrassroots, the people, promoting harmony activities notice >, more mines and enterprises, solve the masses of grassroots lea term mechanism views > and < on the depth of the-lead in implementing the line. <. In the construction of work style building long ello, not pre arranged. After the investigation to submit the research report. 3, insist on grassroots party members take thesay h em, determine the research topic, by members of the Party led research. Basic research to see the truth, to the truth, do notbvious. The major issues and enterprises it is a matter of security bureau year development, the vital interests of the probl1, 2, to further improve research, solve thoroughly, not solid, the effect is not o 3 TP505:还原后的信号输出。 未失真信号 --------,-------,--------, 4、改变抽样频率为和，观察复原后的信号，比较其失真程度。 f,2Bf,2Bss 结论:抽样频率是的失真程度远远小于时的失真程度。 f,2Bf,2Bss 五、心得体会 进行该次试验～组装、调整函数信号发生器时～面对复杂的电路板～才体会到了事先做好预习的重要性。看懂预习册的电路图～仔细得寻找相关的元件～耐心、细心。对要做的实验内容得有一定的了解和分析能力～即相关的知识掌握～才能够在实验过程中检查数据的正确性～和准确性。 打开示波器的时候～看到的不是预想的波形～得学会分析～慢慢地调节和观察～直到成功观察到对应的图像。 adership: Luo Mingjun, rectification time: before September 25th, insist for a long time) s contact farmers" activities and each cadres to contact a people, bycadred enterprises, solve the masses of grassroots leaders, mine is not enough. 4, contact a crowd. Combined with the "grassroots term mechanism views > and < on the depth of the grassroots, the people, promoting harmony activities notice >, more mines an-g longt. 3, insist on grassroots party members take the lead in implementing the line. <. In the construction of work style buildinarch to see the truth, to the truth, do not say hello, not pre arranged. After the investigation to submit the research reporrese ar development, the vital interests of the problem, determine the research topic, by members of the Party led research. Basicsolve thoroughly, not solid, the effect is not obvious. The major issues and enterprises it is a matter of security bureau ye 1, 2, to further improve research, 4