離散時(shí)間信與系統(tǒng)課件

1、1,0( )0,0nnn1,0( )0,0nu nn101( )00NnNRnnnN或0( )()( )( )(1)( )( )()kNu nnknu nu nRnu nu nN nAanx0( )00nanx nn0,jjeaaeAA 0000cossinnnj njnjnx nA eaeA aeA anjn1a2 rnjjnnrjeAeAenx2200r200和22, 0,或02T000cos()cos()AnAnN02Nk2( )nSx n( )() ()mx nx mnm kx nx knk1()0mnnmmn( )( ) ()0 x nmnx mnmmn( )( ) ()mx nx

2、mnm( ) ( )() ()my nT x nTx mnm( ) ( )h nTn( )( )()my nx m Tnm()()Tnmh nm( )() ()( )( )my nx m h nmx nh n對(duì)序列對(duì)序列xn和和hn進(jìn)行卷積運(yùn)算，首先將進(jìn)行卷積運(yùn)算，首先將xn分解分解成脈沖和的形式，然后將每個(gè)脈沖分別作用到成脈沖和的形式，然后將每個(gè)脈沖分別作用到hn上得到響應(yīng)，最后將響應(yīng)累加起來即得到卷積結(jié)上得到響應(yīng)，最后將響應(yīng)累加起來即得到卷積結(jié)果。因?yàn)樵撨^程需要運(yùn)用疊加定理，所以卷積運(yùn)果。因?yàn)樵撨^程需要運(yùn)用疊加定理，所以卷積運(yùn)算只能用于線性時(shí)不變系統(tǒng)。算只能用于線性時(shí)不變系統(tǒng)。203 x

3、nxnx nx n強(qiáng)調(diào)：只有線性時(shí)不變系統(tǒng)才可以應(yīng)用單位脈沖響強(qiáng)調(diào)：只有線性時(shí)不變系統(tǒng)才可以應(yīng)用單位脈沖響應(yīng)卷積輸入信號(hào)來表示結(jié)果。應(yīng)卷積輸入信號(hào)來表示結(jié)果。203 y nyny ny n*nxnhnhnxkknhkxnhnx*knm*nxnhmhmnxnhnxm)*)(*2121nhnxnhnxnhnhnxknm( )kSh k ( )( ) ()( )kmy nh k x nkmh k ()( )0()( )0( )0hnh nhnx nh n2( )(0)() ( )( )kkh kyxk h kSh kdnnnhothersMnMMMknMMnhMMk0111121212121nknu

4、nnknh0001 1nnnh 1nnnhnjenxnh() ( )jn kj nj kkky nh k eeh k ekkjjwekheH)(njjeeHny)()(jweH)()()(jwIjwRjwejHeHeH)()()(jweHjARGjwjweeHeH 1,2,3,4,5,( 11)h nh51() jwj kj kkkH eh k eke-10-8-6-4-20246810246810121416()jH e()( )jj nnX ex n e1( )()2jj nx nX eed)()()(jwIjwRjwejHeHeH)()()(jweHjARGjwjweeHeH)(jweH

5、()jwARG H e, deemxdeeXnxnjnnjnjj21)(21 demxmnjn)(21)()(sin21)(mnmnmndemnj mxmnmxnxn*nxnxee*nxnxoonxnxnxoe)(21*nxnxnxe)(21*nxnxnxojeXnx*nnjjenxeX)(*nnjjenxeX)( x n* x n jx nX e設(shè)， x n* x njeXnx* jx nXejeXnx*jeXnx*jxnXejeeXnxRe-10-8-6-4-20246810246810121416182022-10-8-6-4-20246810246810121416182022jeXn

6、xjeeXnxRejeXnxjeeXnxRe-2-1.5-1-0.500.511.52-4-3-2-101234-2-1.5-1-0.500.511.52-4-3-2-10123421Re*nxnxnxjejjeXeXeX*21-10-8-6-4-20246810246810121416182022-10-8-6-4-20246810246810121416182022頻 率幅度jeXnxIm jojx nXe21Im*nxnxnxjjojjeXeXeX*21-2-1.5-1-0.500.511.52-4-3-2-101234-2-1.5-1-0.500.511.52-4-3-2-101234

7、21Im*nxnxnxjjojjeXeXeX*21jeXnxIm jojx nXe)(21*nxnxnxeRe*21jjjeXeXeX-10-8-6-4-202468100510152025-10-8-6-4-20246810246810121416182022-2-1.5-1-0.500.511.52-4-3-2-101234jeXnx1*Re2jjjX eXeX eRejX e-2-1.5-1-0.500.511.52-4-3-2-101234)(21*nxnxnxoIm*21jjjeXjeXeX-10-8-6-4-202468100510152025-10-8-6-4-202468102

8、46810121416182022Im*21jjjeXjeXeX-2-1.5-1-0.500.511.52-4-3-2-101234-2-1.5-1-0.500.511.52-4-3-2-101234ImjjX e/ 2/ 2或者-jeXnx*nxnx*jjeXeXReRejjeXeXjjX eX eIm Im jjX eX e jjX eX e jeXnxjeYnyjjebYeaXnbynax j nj nj nnnj nj nnnax nby n eax n eby n eax n eby n ejnjdeXennxdjeXnx-2-1.5-1-0.500.511.52-4-3-2-101

9、234-2-1.5-1-0.500.511.52-4-3-2-101234jeXnxjnjdeXennxdjeXnx)(00jnjeXnxe-2-1.5-1-0.500.511.52-4-3-2-101234-2-1.5-1-0.500.511.52-4-3-2-101234jeXnx)(00jnjeXnxe0jeXnx jeXnx-2-1.5-1-0.500.511.52-4-3-2-101234-2-1.5-1-0.500.511.52-4-3-2-101234jeXnxjeXnx jeXnxdedXjnnxj-10-8-6-4-20246810246810121416182022-10-

10、8-6-4-2024681020304050607080jeXnxdedXjnnxjjeXnxdeXnxEjn2221 deYeXnynxjjn*21能量密度譜能量密度譜能量有限信號(hào)能量有限信號(hào)jeXnxjeYny* jjeYeXnynx* jjkeYeXknykx* deeYeXknykxnjjjk*21 deeYeXnkykxnjjjk*21 deYeXkykxjjk*21jeXnxjeHnh*nhnxny jjjeHeXeY nknjnnjjeknhkxenyeY mkkjmjmkkmjknmeemhkxemhkx jjmkkjmjeYeHekxemh*nhnxnydnnnhdnjjeeH jjjeHeXeYdnjjjeeXeYjeXnxjeWnwnwnxnydeXeXeYjjj21dedeXeXdeeYnynjjjnjj212121 2121dedeXeXnjjj2121deeXdeeXnjjnjjnwnx 5nuanxn 555nuaan5511jjjeaeaeX4 32 143210nanananananuan443322110011jjjjjjjeaeaeaea