Title: ??? ???????(DFT)
1??? DFT ???????
2 5-1 ??
- ?.DFT??????
- 1.?????????????
- 2.???????????????
- 3.???????????,????
- ?????????DFT?????
- ???
3- ?.DFT?????????
-
- DFT???????
- ???????,
- ???????
????
????
DFT(FFT)
????
4- 5-2 ???????????
- ?.??????????????-????
t
0
0
5??? ????,? ?????? ?????
6 7?????Tp, ???????2p/Tp
8- ?.??????????????
-
--???????
---
---
0
9(No Transcript)
10x(nT)x(n)
NT
t
0
T
2T
n
1 2 N
11 ???????,?????????????,???????????
12DFT????? ??????,???????
13(No Transcript)
14??n???,
??k???,
??,
155.3 DFT/IDFT??(P197-199)
165.4 ?????? P199-203
17- 5-5 DFT???
- ?.??
- 1.?????N??
- ??
-
- ??
18- 2. ? ???N1?N2???,
- ?? ?????,???
- ?????N??
19- ?.???????
- 1.??
- ??????? ????????
- ????????
- ??? ??????
- ??????
- ????????
-
20(No Transcript)
21(No Transcript)
22(No Transcript)
23- 2.???????
- ?????????,????n0?N-1???
- ???,??????????????,????
- ??????????????????? ??
- ??N??????,????????? ??
- ???,??????????????????,
- ???????? ?
242
1
n0
3
N6
4
5
25???????
1.??????????????????
???N????????????????? ????????
??,?
262.????????????????????????
?????????????????????? ???????
??
??
?????N???????????????? ??????
273.????????
??
284.????????
??
??
295.????????
??
306.????????
??
317.??????????
8.X(k)??????????????????????
329.??????????
?x(n)?????,??????,?
X(k)Xep(k) ??Xep(k)????
?x(n)??????,??????,?
X(k)Xop(k) ??Xop(k)????
33- ?.?????
- 1.??????
- ? ? ?????N????
- ??,? ,
?? ,?
34??
???? ???????, ???????
? ????
??
35(No Transcript)
36(No Transcript)
37m
0
m
0
m
0
m
0
38(No Transcript)
39????
40?.??????????????? 1.???? ????
???? ???????
41 ?????? ?????? ??????? ???
??????. ??
1
n
0
1
2
1
n
0
1
2
3
42(No Transcript)
43m
3
3
2
2
1
1
n
2
1
3
4
0
5
44- 2.???????????
- ?????????????????????.
- ???? , ????
,???????L????, ?? ???????????????
,? - ????????
45(No Transcript)
46- ??,??????????????,????L.?? ?
????,????L???? - ?????????????????,????????????????????
???,?
475.7 FFT
- ?.DFT??????
-
-
- ???????????????1/N.
48??X(k)??????,?X(1)
- ??x(n)? ????,??????
- X(k)????N???????,? ?
- ??????.??,???X(k)??N2??
- ?????,N(N-1)???????.?N?
- ??,????????,?N1024,???
- ?1048576 ?(?????)??.??,????????.
49?.?????
???
???
?
50- ??????,????????,?
- ?DFT??????,????????,?
- ?????.1965?,??(cooley)???
- (Tukey)????FFT??.??N?DFT,??
- (N/2)log2N ???????.??N1024210 ?,
- ??(1024/2)log2 210 512105120??
- 5120/10485764.88 ,????20?
51- ?.????(?2FFT)
- (?)N/2?DFT
- 1.?? ?n????????DFT,?N2L ,???,????????
- n????
- n????
??,
52(n???) (n???)
53 - ??,
- 2.????
- (1) X (k),X (k)??N/2??DFT?
- (2) X(k)X (k)W X (k)?????
- X(k)?k ?
- ????????
1 2
k
1 2
N
543.X(k)???????
?? (???),??
- ??,
- ????,X1(k),X2(k)????,??
- ?????????
55??? ,??
- ??,X(k)????,????X1(k), X2 (k)????????
- N??DFT????N/2??DFT????
564.????
?X1(k)?X 2(k)??X(k)???????????-????
???
???
(N/2???)
1 1
(???)
1
1
(???)
-1
575.???????
???????????
- (1)N/2??DFT???????
- ????
- (2)??N/2??DFT???????
- ????
- (3)N/2?????????????
- ????
??
?????
??
??,N?DFT????N2 ??N(N-1)? ???????,??????
???? ???
58- ?? N8 ??DFT,???????
- N/24??DFT.??????
- (1)n????,?
- ????
-
-
-
59 60(3)?X (k)?X (k)??????,???? X(0) X(3),?????X(4)
X(7) ?????????
1 2
X1(0)
X(0)
- x1(0)x(0)
- x1(1)x(2) N/2?
- x1(2)x(4) DFT
- x1(3)x(6)
-
- x2(0)x(1)
- x2(1)x(3) N/2?
- x2(2)x(5) DFT
- x2(3)x(7)
X1(1)
X(1)
X1(2)
X(2)
X1(3)
X(3)
X2(0)
X(4)
0
-1
W
X2(1)
N
X(5)
1
-1
W
X2(2)
N
X(6)
2
W
-1
N
X2(3)
X(7)
-1
3
W
N
61(?) N/4?DFT
- ??N2 L ,?? N/2????,???
- ?????N/2???????????
- ?????N/4???????,n????? N/2????
??N/4??DFT,??
(???)
(???)
62??????N/4?X1(k)
?N/4?X1(k)?
63???n????,N/2?????N/4? ?????DFT,??
(???)
(???)
64 ??,N8??DFT??????N/4?DFT, ??????
(1) ????x(n)??????
??N/4?DFT,????X3(0), X3(1)?
65(2) ????x(n)??????
??N/4?DFT,????X4(0), X4(1)?
(3) ????x(n)??????
??N/4?DFT,????X5(0), X5(1)?
66(4) ????x(n)??????
??N/4?DFT,????X6(0), X6(1)?
(5)? X3(0), X3(1), X4(0), X4(1)??????,
??X1(0), X1(1), X1(2), X1(3)?
(6)? X5(0), X5(1), X6(0), X6(1)??????,
??X2(0), X2(1), X2(2), X2(3)?
67(7)?X1(0), X1(1), X1(2), X1(3),X2(0),
X2(1),X2(2), X2(3)??????, ?? X(0),
X(1), X(2), X(3) X(4), X(5), X(6), X(7) ?
- (0) (0) (0) N/4
- (1) (2) (4) DFT
- (0) (1) (2) N/4
- (1) (3) (6) DFT
- (0) (0) (1) N/4
- (1) (2) (5) DFT
- (0) (1) (3) N/4
- (1) (3) (7) DFT
X(0)
3 1
X(1)
3 1
X(2)
4 1
0
-1
N
X(3)
4 1
2
-1
N
X(4)
5 2
-1
X(5)
5 2
-2
X(6)
6 2
0
-1
N
N
6 2
X(7)
2
-1
68- ??,?????,????N/4?DFT,
- ??????,???????????
- ??N?DFT?1/4?
- ??N8?DFT,N/4?????DFT,??
69 70??,8?DFT?FFT???????
X(0)
- (0)
- (4)
- (2)
- (6)
- (1)
- (5)
- (3)
- (7)
0
W
X(1)
N
-1
X(2)
-1
0
W
X(3)
N
0
-1
-1
X(4)
N
1
-1
0
W
X(5)
N
N
2
-1
-1
X(6)
N
3
-1
0
-1
W
X(7)
N
N
-1
-1
-1
71- ??FFT??,??????????
- ??????????????????
- ??,???????????? ?
- ?.???
- ???????,N8??????? N2 8,????,N2L
??L?????, - ??????N/2????? ??,???
- ????????,?????
(DIT)
3
72- ??,N??FFT?????
- ?? mF (N/2)L(N/2) log2 N
- ?? aF N LN log2 N
- ???????????????
- ? ???????,????????
- ??.??4-1??(pp.145)?
73????????????????????????
- (0)X0(0) X1(0) X2(0)
X3(0)X(0) - (4)X0(1) X1(1) X2(1)
X3(1)X(1) - (2)X0(2) X3(2)X(2)
- (6)X0(3) X3(3)X(3)
- (1)X0(4) X1(4) X2(4)
X3(4)X(4) - (5)X0(5) X3(5)X(5)
- (3)X0(6) X3(6)X(6)
- (7)X0(7) X1(7) X2(7) X3(7)X(7)
0
W
N
-1
0
W
. . .
. . .
N
0
2
-1
W
W
N
N
0
-1
-1
W
N
0
1
. . .
W
. .
W
N
N
-1
0
2
W
W
N
N
3
-1
2
0
W
W
W
N
N
N
-1
-1
74 ???????,???N???/??,???log2
NL?(?)????(??????).
??m(m1,2, ,L)???m??k,j???? ???????(?/
?)??(0,1,2, ,N-1)???????????????????, ?
75 76- ?m2?,??(?????)
-
-
-
- ?m3?,??(?????)
-
-
77- ??,????????????????(?)k?j?????
- ?????????????? ,????(??)???
??,??????????????????????????????,?????????????(?)
?N/2?????,????N?????,??? ??????
78- 2 ?????
- ????,??X(k)??????
- ??????,???????
- ?????????,?????
- ???
79 ??????????,?N8?? ????
80- 3.?????
- ???????????????
- ?,???????????????
- ?????????n,????
- (n2 n1 n0 )2 ,?????? ??,????????(n0 n1 n2 )2
,?? ,N8????
81????n ???n n n ??????n n n ????n
2 1 0
0 1 2
- 0 0 0 0 0 0 0 0
- 1 0 0 1 1 0 0 4
- 2 0 1 0 0 1 0 2
- 3 0 1 1 1 1 0 6
- 4 1 0 0 0 0 1 1
- 5 1 0 1 1 0 1 5
- 6 1 1 0 0 1 1 3
- 7 1 1 1 1 1 1 7
82??????
????
????
??
???
4.??????????2m-1 ??,m???m?,?m 1, ,L
??N823 ,???(?)???21-11,
???(?)???22-12, ???(?)???23-14?
83- 5.WNr ???(?????)
- ?????????????2m-1 ,?
- ??????
- Xm(k)Xm-1(k)Xm-1(k2m-1)WNr
- Xm(k2m-1)Xm-1(k)-Xm-1(k2m-1)WNr
- ??N???,???r???????
??,?k(n2n1n0)2 ,??k (n2n1n0)2
??(L-m)?,??????,???? (r)2 ??,?(r)2 (k)22L-m ?
84- ?? N823
- (1)k2 , m3 ?r?,?k2(010)2 ??L-m3-30 ,?
r(010)22 - (2)k3 ,m3 ?r? k 3(011)2,??0?,r3
- (3)k5 ,m2?? k5(101)2 ??L-m1? r(010)2
2?
85- 6.????
- ????? (n),n0,1, ,N-1, ?N
- ???
- ???? , r0,1, ,(N/2)-1,
- ?N/2?????
- ??(NN/2)??????