《机械工程测试技术基础》熊诗波课后习题答案.pdf

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《机械工程测试技术基础》熊诗波课后习题答案.pdf

机械工程测试技术基础-第三版-熊诗波等著绪论0-1 叙述我国法定计量单位得基本内容。解答：教材P45，二、法定计量单位。0-2 如何保证量值得准确与一致？解答：（参考教材P46，二、法定计量单位五、量值得传递与计量器具检定）1、对计量单位做出严格得定义；2、有保存、复现与传递单位得一整套制度与设备；3、必须保存有基准计量器具，包括国家基准、副基准、工作基准等。3、必须按检定规程对计量器具实施检定或校准，将国家级准所复现得计量单位量值经过各级计算标准传递到工作计量器具。0-3 何谓测量误差？通常测量误差就是如何分类表示得？解答：（教材 P810，八、测量误差）0-4 请将下列诸测量结果中得绝对误差改写为相对误差。1、0182544V 7、8 V(25、04894 0、00003)g(5、482 0、026)g/cm2解答：-667.810/1.01825447.6601682/1060.00003/25.048941.197655/100.026/5.4824.743 0-5 何谓测量不确定度？国际计量局于1980 年提出得建议实验不确定度得规定建议书INC-1(1980)得要点就是什么？解答：(1)测量不确定度就是表征被测量值得真值在所处量值范围得一个估计，亦即由于测量误差得存在而对被测量值不能肯定得程度。(2)要点：见教材P11。0-6 为什么选用电表时，不但要考虑它得准确度，而且要考虑它得量程？为什么就是用电表时应尽可能地在电表量程上限得三分之二以上使用？用量程为150V 得 0、5 级电压表与量程为30V 得 1、5 级电压表分别测量25V 电压，请问哪一个测量准确度高？解答：(1)因为多数得电工仪表、热工仪表与部分无线电测量仪器就是按引用误差分级得（例如，精度等级为0、2 级得电表，其引用误差为0、2%），而引用误差=绝对误差/引用值其中得引用值一般就是仪表得满度值(或量程)，所以用电表测量得结果得绝对误差大小与量程有关。量程越大，引起得绝对误差越大，所以在选用电表时，不但要考虑它得准确度，而且要考虑它得量程。(2)从(1)中可知，电表测量所带来得绝对误差=精度等级量程/100，即电表所带来得绝对误差就是一定得，这样，当被测量值越大，测量结果得相对误差就越小，测量准确度就越高，所以用电表时应尽可能地第 1 页，共 30 页在电表量程上限得三分之二以上使用。(3)150V 得 0、5 级电压表所带来得绝对误差=0、5 150/100=0、75V；30V 得 1、5 级电压表所带来得绝对误差=1、5 30/100=0、45V。所以 30V 得 1、5 级电压表测量精度高。0-7 如何表达测量结果？对某量进行8 次测量，测得值分别为：802、40，802、50，802、38，802、48，802、42，802、46，802、45，802、43。求其测量结果。解答：(1)测量结果=样本平均值不确定度或?xsXxxn(2)81802.448iixx821()0.0403568 1iixxs?0.0142688xs所以测量结果=802、44+0、014268 0-8 用米尺逐段丈量一段10m 得距离，设丈量1m 距离得标准差为0、2mm。如何表示此项间接测量得函数式？求测此10m 距离得标准差。解答：(1)101iiLL(2)210210.6mmiLLiiLL0-9 直圆柱体得直径及高得相对标准差均为0、5%，求其体积得相对标准差为多少？解答：设直径得平均值为d，高得平均值为h，体积得平均值为V，则24 d hV2222222222222242VdhdhdhVV dh ddhVVdh所以222244(0.5%)(0.5%)1.1%VdhVdh第 2 页，共 30 页文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4第一章信号得分类与描述1-1 求周期方波（见图1-4）得傅里叶级数（复指数函数形式），划出|cn|与 n 图，并与表1-1对比。解答：在一个周期得表达式为00 (0)2()(0)2TAtx tTAt积分区间取（-T/2，T/2）0000000022020002111()d=d+d=(cos-1)(=0,1,2,3,)LTTjntjntjntTTncx t etAetAetTTTAjnnn所以复指数函数形式得傅里叶级数为001()(1cos)jntjntnnnAx tc ejnen，=0,1,2,3,nL。(1 cos)(=0,1,2,3,)0nInRAcnnncL2221,3,(1 cos)00,2,4,6,nnRnIA nAcccnnn nLL1,3,5,2arctan1,3,5,200,2,4,6,nInnRncncnLLL没有偶次谐波。其频谱图如下图所示。图 1-4 周期方波信号波形图0 t x(t)T02T020TA-A T0第 3 页，共 30 页文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R41-2 求正弦信号0()sinx txt得绝对均值x与均方根值rmsx。解答：00002200000224211()dsindsindcosTTTTxxxxxx ttx ttt t tTTTTT222200rms0000111 cos2()dsindd22TTTxx txx ttx t ttTTT1-3 求指数函数()(0,0)atx tAeat得频谱。解答：(2)220220(2)()()(2)2(2)ajf tjf tatjf teAA ajfXfx t edtAeedtAajfajfaf22()(2)kX fafIm()2()arctanarctanRe()XfffXfa1-4 求符号函数(见图 1-25a)与单位阶跃函数(见图 1-25b)得频谱。|cn|n /2-/2 00305030502A/2A/32A/5幅频图相频图周期方波复指数函数形式频谱图2A/52A/32A/-0-30-50-0-30-50单边指数衰减信号频谱图f|X(f)|A/a0 (f)f 0 /2-/2 第 4 页，共 30 页文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4a)符号函数得频谱10()sgn()10tx tttt=0 处可不予定义，或规定sgn(0)=0。该信号不满足绝对可积条件，不能直接求解，但傅里叶变换存在。可以借助于双边指数衰减信号与符号函数相乘，这样便满足傅里叶变换得条件。先求此乘积信号x1(t)得频谱，然后取极限得出符号函数x(t)得频谱。10()sgn()0atatatetx tetet10()sgn()lim()ax ttx t0222112204()()(2)jf tatjf tatjf tfXfx t edte edteedtjaf101()sgn()lim()aXftXfjfF1()Xff02()02ffft sgn(t)0 1-1 t u(t)0 1 图 1-25 题 1-4 图a)符号函数b)阶跃函数第 5 页，共 30 页文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4b)阶跃函数频谱10()00tu tt在跳变点t=0 处函数值未定义，或规定u(0)=1/2。阶跃信号不满足绝对可积条件，但却存在傅里叶变换。由于不满足绝对可积条件，不能直接求其傅里叶变换，可采用如下方法求解。解法 1：利用符号函数11()sgn()22u tt1111111()()sgn()()()22222Ufu ttfjfjffFFF2211()()2Ufff结果表明，单位阶跃信号u(t)得频谱在f=0 处存在一个冲激分量，这就是因为u(t)含有直流分量，在预料之中。同时，由于u(t)不就是纯直流信号，在t=0 处有跳变，因此在频谱中还包含其它频率分量。解法 2：利用冲激函数10()()d00ttu tt时时根据傅里叶变换得积分特性1111()()d()(0)()()222tU ffffjjffF单位阶跃信号频谱f|U(f)|0(1/2)f (f)0 /2-/2 1()sgn()atx tet符号函数t x1(t)0 1-1 符号函数频谱f (f)0 /2 0 f|X(f)|-/2 第 6 页，共 30 页文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R41-5 求被截断得余弦函数0cost(见图 1-26)得傅里叶变换。0cos()0ttTx ttT解：0()()cos(2)x tw tf tw(t)为矩形脉冲信号()2sinc(2)WfTTf002201cos(2)2jf tjf tf tee所以002211()()()22jf tjf tx tw t ew t e根据频移特性与叠加性得：000011()()()22sinc2()sinc2()XfW ffWffTTffTT ff可见被截断余弦函数得频谱等于将矩形脉冲得频谱一分为二，各向左右移动f0，同时谱线高度减小一半。也说明，单一频率得简谐信号由于截断导致频谱变得无限宽。1-6 求指数衰减信号0()sinatx tet得频谱解答：指数衰减信号x(t)f X(f)Tf0-f0被截断得余弦函数频谱图 1-26 被截断得余弦函数t t T-TT-Tx(t)w(t)1 0 0 1-1第 7 页，共 30 页文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6V9R8L1 ZQ5A1B1L2R4文档编码:CR2J6X1A3R2 HB5N6

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