jww100 发表于 2008-9-16 08:55

【求助】IFFT的问题

按道理对频域信号进行IFFT变换得到的结果应该为实数
但我在对一组频域信号进行IFFT变换时，得到的结果不是一组实数，而是一组复数，于是我就直接取了该复数的实部

（1）我想请教一下是什么原因导致结果不是实数，而是复数？
（2）如果我直接取该复数的实部，会对结果误差造成多大的影响？

恳请赐教，感谢万分！

jww100 发表于 2008-9-18 09:12

【求助】我的IFFT到底哪里出问题了？？？

我的频域数据是一组共轭数据，为什么IFFT后得到的不是实数？而是复数?
恳请各位老师帮忙，万分感谢！
还有我的频率取样没有什么依据，如果各位老师觉得不好，请您指出。

H31 =
-22500*(i*ww+100)^2/(3*ww^6-2865*i*ww^5-956750*ww^4+158800000*i*ww^3+14127500000*ww^2-742500000000*i*ww-24750000000000)

HH31=subs(H31,ww,(-199.5)*pi:pi:(199.5)*pi)；

xxx=
xxx =
1.0e-004 *
Columns 1 through 8
   0.0909 - 0.0014i   0.0913 - 0.0043i   0.0919 - 0.0073i   0.0928 - 0.0105i   0.0940 - 0.0140i   0.0954 - 0.0179i   0.0972 - 0.0223i   0.0991 - 0.0273i
Columns 9 through 16
   0.1011 - 0.0331i   0.1031 - 0.0398i   0.1050 - 0.0477i   0.1065 - 0.0570i   0.1071 - 0.0678i   0.1064 - 0.0803i   0.1035 - 0.0946i   0.0976 - 0.1101i
Columns 17 through 24
   0.0877 - 0.1263i   0.0729 - 0.1416i   0.0533 - 0.1541i   0.0297 - 0.1616i   0.0044 - 0.1625i-0.0200 - 0.1566i-0.0410 - 0.1451i-0.0571 - 0.1301i
Columns 25 through 32
-0.0681 - 0.1135i-0.0748 - 0.0972i-0.0779 - 0.0821i-0.0785 - 0.0686i-0.0775 - 0.0569i-0.0753 - 0.0469i-0.0724 - 0.0384i-0.0692 - 0.0312i
Columns 33 through 40
-0.0658 - 0.0251i-0.0624 - 0.0199i-0.0591 - 0.0155i-0.0558 - 0.0118i-0.0527 - 0.0086i-0.0497 - 0.0058i-0.0469 - 0.0035i-0.0442 - 0.0015i
Columns 41 through 48
-0.0417 + 0.0002i-0.0393 + 0.0017i-0.0371 + 0.0029i-0.0350 + 0.0040i-0.0330 + 0.0049i-0.0311 + 0.0057i-0.0293 + 0.0064i-0.0276 + 0.0070i
Columns 49 through 56
-0.0261 + 0.0074i-0.0246 + 0.0078i-0.0232 + 0.0081i-0.0218 + 0.0084i-0.0206 + 0.0086i-0.0194 + 0.0087i-0.0183 + 0.0088i-0.0173 + 0.0089i
Columns 57 through 64
-0.0163 + 0.0089i-0.0153 + 0.0089i-0.0145 + 0.0089i-0.0136 + 0.0089i-0.0128 + 0.0088i-0.0121 + 0.0088i-0.0114 + 0.0087i-0.0107 + 0.0086i
Columns 65 through 72
-0.0101 + 0.0084i-0.0095 + 0.0083i-0.0090 + 0.0082i-0.0085 + 0.0080i-0.0080 + 0.0079i-0.0075 + 0.0078i-0.0071 + 0.0076i-0.0067 + 0.0074i
Columns 73 through 80
-0.0063 + 0.0073i-0.0059 + 0.0071i-0.0055 + 0.0070i-0.0052 + 0.0068i-0.0049 + 0.0067i-0.0046 + 0.0065i-0.0043 + 0.0064i-0.0041 + 0.0062i
Columns 81 through 88
-0.0038 + 0.0061i-0.0036 + 0.0059i-0.0034 + 0.0058i-0.0032 + 0.0056i-0.0030 + 0.0055i-0.0028 + 0.0053i-0.0026 + 0.0052i-0.0025 + 0.0051i
Columns 89 through 96
-0.0023 + 0.0049i-0.0021 + 0.0048i-0.0020 + 0.0047i-0.0019 + 0.0045i-0.0018 + 0.0044i-0.0016 + 0.0043i-0.0015 + 0.0042i-0.0014 + 0.0041i
Columns 97 through 104
-0.0013 + 0.0040i-0.0012 + 0.0039i-0.0011 + 0.0038i-0.0011 + 0.0037i-0.0010 + 0.0036i-0.0009 + 0.0035i-0.0008 + 0.0034i-0.0008 + 0.0033i
Columns 105 through 112
-0.0007 + 0.0032i-0.0007 + 0.0031i-0.0006 + 0.0030i-0.0006 + 0.0030i-0.0005 + 0.0029i-0.0005 + 0.0028i-0.0004 + 0.0027i-0.0004 + 0.0027i
Columns 113 through 120
-0.0003 + 0.0026i-0.0003 + 0.0025i-0.0003 + 0.0024i-0.0002 + 0.0024i-0.0002 + 0.0023i-0.0002 + 0.0023i-0.0001 + 0.0022i-0.0001 + 0.0021i
Columns 121 through 128
-0.0001 + 0.0021i-0.0001 + 0.0020i-0.0001 + 0.0020i-0.0000 + 0.0019i-0.0000 + 0.0019i   0.0000 + 0.0018i   0.0000 + 0.0018i   0.0000 + 0.0017i
Columns 129 through 136
   0.0000 + 0.0017i   0.0001 + 0.0017i   0.0001 + 0.0016i   0.0001 + 0.0016i   0.0001 + 0.0015i   0.0001 + 0.0015i   0.0001 + 0.0015i   0.0001 + 0.0014i
Columns 137 through 144
   0.0001 + 0.0014i   0.0001 + 0.0013i   0.0001 + 0.0013i   0.0002 + 0.0013i   0.0002 + 0.0013i   0.0002 + 0.0012i   0.0002 + 0.0012i   0.0002 + 0.0012i
Columns 145 through 152
   0.0002 + 0.0011i   0.0002 + 0.0011i   0.0002 + 0.0011i   0.0002 + 0.0011i   0.0002 + 0.0010i   0.0002 + 0.0010i   0.0002 + 0.0010i   0.0002 + 0.0010i
Columns 153 through 160
   0.0002 + 0.0009i   0.0002 + 0.0009i   0.0002 + 0.0009i   0.0002 + 0.0009i   0.0002 + 0.0009i   0.0002 + 0.0008i   0.0002 + 0.0008i   0.0002 + 0.0008i
Columns 161 through 168
   0.0002 + 0.0008i   0.0002 + 0.0008i   0.0002 + 0.0007i   0.0002 + 0.0007i   0.0002 + 0.0007i   0.0002 + 0.0007i   0.0002 + 0.0007i   0.0002 + 0.0007i
Columns 169 through 176
   0.0002 + 0.0006i   0.0002 + 0.0006i   0.0002 + 0.0006i   0.0002 + 0.0006i   0.0002 + 0.0006i   0.0002 + 0.0006i   0.0002 + 0.0006i   0.0002 + 0.0006i
Columns 177 through 184
   0.0002 + 0.0005i   0.0002 + 0.0005i   0.0002 + 0.0005i   0.0002 + 0.0005i   0.0002 + 0.0005i   0.0002 + 0.0005i   0.0002 + 0.0005i   0.0002 + 0.0005i
Columns 185 through 192
   0.0002 + 0.0005i   0.0002 + 0.0004i   0.0002 + 0.0004i   0.0002 + 0.0004i   0.0002 + 0.0004i   0.0002 + 0.0004i   0.0002 + 0.0004i   0.0002 + 0.0004i
Columns 193 through 200
   0.0002 + 0.0004i   0.0002 + 0.0004i   0.0002 + 0.0004i   0.0002 + 0.0004i   0.0002 + 0.0004i   0.0002 + 0.0003i   0.0002 + 0.0003i   0.0002 + 0.0003i
Columns 201 through 208
   0.0002 - 0.0003i   0.0002 - 0.0003i   0.0002 - 0.0003i   0.0002 - 0.0004i   0.0002 - 0.0004i   0.0002 - 0.0004i   0.0002 - 0.0004i   0.0002 - 0.0004i
Columns 209 through 216
   0.0002 - 0.0004i   0.0002 - 0.0004i   0.0002 - 0.0004i   0.0002 - 0.0004i   0.0002 - 0.0004i   0.0002 - 0.0004i   0.0002 - 0.0004i   0.0002 - 0.0005i
Columns 217 through 224
   0.0002 - 0.0005i   0.0002 - 0.0005i   0.0002 - 0.0005i   0.0002 - 0.0005i   0.0002 - 0.0005i   0.0002 - 0.0005i   0.0002 - 0.0005i   0.0002 - 0.0005i
Columns 225 through 232
   0.0002 - 0.0006i   0.0002 - 0.0006i   0.0002 - 0.0006i   0.0002 - 0.0006i   0.0002 - 0.0006i   0.0002 - 0.0006i   0.0002 - 0.0006i   0.0002 - 0.0006i
Columns 233 through 240
   0.0002 - 0.0007i   0.0002 - 0.0007i   0.0002 - 0.0007i   0.0002 - 0.0007i   0.0002 - 0.0007i   0.0002 - 0.0007i   0.0002 - 0.0008i   0.0002 - 0.0008i
Columns 241 through 248
   0.0002 - 0.0008i   0.0002 - 0.0008i   0.0002 - 0.0008i   0.0002 - 0.0009i   0.0002 - 0.0009i   0.0002 - 0.0009i   0.0002 - 0.0009i   0.0002 - 0.0009i
Columns 249 through 256
   0.0002 - 0.0010i   0.0002 - 0.0010i   0.0002 - 0.0010i   0.0002 - 0.0010i   0.0002 - 0.0011i   0.0002 - 0.0011i   0.0002 - 0.0011i   0.0002 - 0.0011i
Columns 257 through 264
   0.0002 - 0.0012i   0.0002 - 0.0012i   0.0002 - 0.0012i   0.0002 - 0.0013i   0.0002 - 0.0013i   0.0001 - 0.0013i   0.0001 - 0.0013i   0.0001 - 0.0014i
Columns 265 through 272
   0.0001 - 0.0014i   0.0001 - 0.0015i   0.0001 - 0.0015i   0.0001 - 0.0015i   0.0001 - 0.0016i   0.0001 - 0.0016i   0.0001 - 0.0017i   0.0000 - 0.0017i
Columns 273 through 280
   0.0000 - 0.0017i   0.0000 - 0.0018i   0.0000 - 0.0018i-0.0000 - 0.0019i-0.0000 - 0.0019i-0.0001 - 0.0020i-0.0001 - 0.0020i-0.0001 - 0.0021i
Columns 281 through 288
-0.0001 - 0.0021i-0.0001 - 0.0022i-0.0002 - 0.0023i-0.0002 - 0.0023i-0.0002 - 0.0024i-0.0003 - 0.0024i-0.0003 - 0.0025i-0.0003 - 0.0026i
Columns 289 through 296
-0.0004 - 0.0027i-0.0004 - 0.0027i-0.0005 - 0.0028i-0.0005 - 0.0029i-0.0006 - 0.0030i-0.0006 - 0.0030i-0.0007 - 0.0031i-0.0007 - 0.0032i
Columns 297 through 304
-0.0008 - 0.0033i-0.0008 - 0.0034i-0.0009 - 0.0035i-0.0010 - 0.0036i-0.0011 - 0.0037i-0.0011 - 0.0038i-0.0012 - 0.0039i-0.0013 - 0.0040i
Columns 305 through 312
-0.0014 - 0.0041i-0.0015 - 0.0042i-0.0016 - 0.0043i-0.0018 - 0.0044i-0.0019 - 0.0045i-0.0020 - 0.0047i-0.0021 - 0.0048i-0.0023 - 0.0049i
Columns 313 through 320
-0.0025 - 0.0051i-0.0026 - 0.0052i-0.0028 - 0.0053i-0.0030 - 0.0055i-0.0032 - 0.0056i-0.0034 - 0.0058i-0.0036 - 0.0059i-0.0038 - 0.0061i
Columns 321 through 328
-0.0041 - 0.0062i-0.0043 - 0.0064i-0.0046 - 0.0065i-0.0049 - 0.0067i-0.0052 - 0.0068i-0.0055 - 0.0070i-0.0059 - 0.0071i-0.0063 - 0.0073i
Columns 329 through 336
-0.0067 - 0.0074i-0.0071 - 0.0076i-0.0075 - 0.0078i-0.0080 - 0.0079i-0.0085 - 0.0080i-0.0090 - 0.0082i-0.0095 - 0.0083i-0.0101 - 0.0084i
Columns 337 through 344
-0.0107 - 0.0086i-0.0114 - 0.0087i-0.0121 - 0.0088i-0.0128 - 0.0088i-0.0136 - 0.0089i-0.0145 - 0.0089i-0.0153 - 0.0089i-0.0163 - 0.0089i
Columns 345 through 352
-0.0173 - 0.0089i-0.0183 - 0.0088i-0.0194 - 0.0087i-0.0206 - 0.0086i-0.0218 - 0.0084i-0.0232 - 0.0081i-0.0246 - 0.0078i-0.0261 - 0.0074i
Columns 353 through 360
-0.0276 - 0.0070i-0.0293 - 0.0064i-0.0311 - 0.0057i-0.0330 - 0.0049i-0.0350 - 0.0040i-0.0371 - 0.0029i-0.0393 - 0.0017i-0.0417 - 0.0002i
Columns 361 through 368
-0.0442 + 0.0015i-0.0469 + 0.0035i-0.0497 + 0.0058i-0.0527 + 0.0086i-0.0558 + 0.0118i-0.0591 + 0.0155i-0.0624 + 0.0199i-0.0658 + 0.0251i
Columns 369 through 376
-0.0692 + 0.0312i-0.0724 + 0.0384i-0.0753 + 0.0469i-0.0775 + 0.0569i-0.0785 + 0.0686i-0.0779 + 0.0821i-0.0748 + 0.0972i-0.0681 + 0.1135i
Columns 377 through 384
-0.0571 + 0.1301i-0.0410 + 0.1451i-0.0200 + 0.1566i   0.0044 + 0.1625i   0.0297 + 0.1616i   0.0533 + 0.1541i   0.0729 + 0.1416i   0.0877 + 0.1263i
Columns 385 through 392
   0.0976 + 0.1101i   0.1035 + 0.0946i   0.1064 + 0.0803i   0.1071 + 0.0678i   0.1065 + 0.0570i   0.1050 + 0.0477i   0.1031 + 0.0398i   0.1011 + 0.0331i
Columns 393 through 400
   0.0991 + 0.0273i   0.0972 + 0.0223i   0.0954 + 0.0179i   0.0940 + 0.0140i   0.0928 + 0.0105i   0.0919 + 0.0073i   0.0913 + 0.0043i   0.0909 + 0.0014i



hh31=ifft(xxx)
hh31 =
1.0e-005 *
Columns 1 through 8
-0.0009 - 0.0000i   0.0322 - 0.0003i   0.1181 - 0.0019i   0.1921 - 0.0045i   0.2286 - 0.0072i   0.2263 - 0.0089i   0.1966 - 0.0093i   0.1495 - 0.0082i
Columns 9 through 16
   0.0962 - 0.0061i   0.0432 - 0.0031i-0.0030 + 0.0002i-0.0398 + 0.0034i-0.0648 + 0.0061i-0.0783 + 0.0080i-0.0810 + 0.0089i-0.0752 + 0.0089i
Columns 17 through 24
-0.0628 + 0.0079i-0.0468 + 0.0063i-0.0292 + 0.0042i-0.0125 + 0.0019i   0.0023 - 0.0004i   0.0136 - 0.0023i   0.0215 - 0.0037i   0.0254 - 0.0046i
Columns 25 through 32
   0.0261 - 0.0050i   0.0239 - 0.0047i   0.0198 - 0.0041i   0.0145 - 0.0031i   0.0090 - 0.0020i   0.0035 - 0.0008i-0.0010 + 0.0002i-0.0047 + 0.0012i
Columns 33 through 40
-0.0070 + 0.0018i-0.0082 + 0.0022i-0.0083 + 0.0023i-0.0076 + 0.0021i-0.0062 + 0.0018i-0.0045 + 0.0014i-0.0027 + 0.0008i-0.0010 + 0.0003i
Columns 41 through 48
   0.0005 - 0.0002i   0.0015 - 0.0005i   0.0023 - 0.0008i   0.0026 - 0.0009i   0.0026 - 0.0010i   0.0023 - 0.0009i   0.0019 - 0.0007i   0.0014 - 0.0005i
Columns 49 through 56
   0.0008 - 0.0003i   0.0003 - 0.0001i-0.0002 + 0.0001i-0.0005 + 0.0002i-0.0007 + 0.0003i-0.0008 + 0.0004i-0.0008 + 0.0004i-0.0008 + 0.0003i
Columns 57 through 64
-0.0006 + 0.0003i-0.0004 + 0.0002i-0.0002 + 0.0001i-0.0001 + 0.0000i   0.0001 - 0.0000i   0.0002 - 0.0001i   0.0002 - 0.0001i   0.0002 - 0.0001i
Columns 65 through 72
   0.0003 - 0.0001i   0.0002 - 0.0001i   0.0002 - 0.0001i   0.0001 - 0.0001i   0.0001 - 0.0000i   0.0000 - 0.0000i-0.0000 + 0.0000i-0.0001 + 0.0000i
Columns 73 through 80
-0.0001 + 0.0000i-0.0001 + 0.0001i-0.0001 + 0.0000i-0.0001 + 0.0001i-0.0000 + 0.0000i-0.0000 + 0.0000i-0.0000 + 0.0000i-0.0000 + 0.0000i
Columns 81 through 88
   0.0000 - 0.0000i   0.0000 - 0.0000i   0.0000 - 0.0000i   0.0000 - 0.0000i   0.0000 - 0.0000i   0.0000 - 0.0000i   0.0000 - 0.0000i   0.0000 - 0.0000i
Columns 89 through 96
   0.0000 - 0.0000i-0.0000 + 0.0000i   0.0000 - 0.0000i-0.0000 + 0.0000i   0.0000 - 0.0000i-0.0000 + 0.0000i   0.0000 - 0.0000i-0.0000 + 0.0000i
Columns 97 through 104
   0.0000 - 0.0000i-0.0000 + 0.0000i   0.0000 - 0.0000i-0.0000 + 0.0000i   0.0000 - 0.0000i-0.0000 + 0.0000i   0.0000 - 0.0000i-0.0000 + 0.0000i
Columns 105 through 112
   0.0000 - 0.0000i-0.0000 + 0.0000i   0.0000 - 0.0000i-0.0000 + 0.0000i   0.0000 - 0.0000i-0.0000 + 0.0000i   0.0000 - 0.0000i-0.0000 + 0.0000i
Columns 113 through 120
   0.0000 - 0.0000i-0.0000 + 0.0000i   0.0000 - 0.0000i-0.0000 + 0.0000i   0.0000 - 0.0000i-0.0000 + 0.0000i   0.0000 - 0.0000i-0.0000 + 0.0000i
Columns 121 through 128
   0.0000 - 0.0000i-0.0000 + 0.0000i   0.0000 - 0.0000i-0.0000 + 0.0000i   0.0000 - 0.0000i-0.0000 + 0.0000i   0.0000 - 0.0000i-0.0000 + 0.0000i
Columns 129 through 136
   0.0000 - 0.0000i-0.0000 + 0.0000i   0.0000 - 0.0000i-0.0000 + 0.0000i   0.0000 - 0.0000i-0.0000 + 0.0000i   0.0000 - 0.0000i-0.0000 + 0.0000i
Columns 137 through 144
   0.0000 - 0.0000i-0.0000 + 0.0000i   0.0000 - 0.0000i-0.0000 + 0.0000i   0.0000 - 0.0000i-0.0000 + 0.0000i   0.0000 - 0.0000i-0.0000 + 0.0000i
Columns 145 through 152
   0.0000 - 0.0000i-0.0000 + 0.0000i   0.0000 - 0.0000i-0.0000 + 0.0000i   0.0000 - 0.0000i-0.0000 + 0.0000i   0.0000 - 0.0000i-0.0000 + 0.0000i
Columns 153 through 160
   0.0000 - 0.0000i-0.0000 + 0.0000i   0.0000 - 0.0000i-0.0000 + 0.0000i   0.0000 - 0.0000i-0.0000 + 0.0000i   0.0000 - 0.0000i-0.0000 + 0.0000i
Columns 161 through 168
   0.0000 - 0.0000i-0.0000 + 0.0000i   0.0000 - 0.0000i-0.0000 + 0.0000i   0.0000 - 0.0000i-0.0000 + 0.0000i   0.0000 - 0.0000i-0.0000 + 0.0000i
Columns 169 through 176
   0.0000 - 0.0000i-0.0000 + 0.0000i   0.0000 - 0.0000i-0.0000 + 0.0000i   0.0000 - 0.0000i-0.0000 + 0.0000i   0.0000 - 0.0000i-0.0000 + 0.0000i
Columns 177 through 184
   0.0000 - 0.0000i-0.0000 + 0.0000i   0.0000 - 0.0000i-0.0000 + 0.0000i   0.0000 - 0.0000i-0.0000 + 0.0000i   0.0000 - 0.0000i-0.0000 + 0.0000i
Columns 185 through 192
   0.0000 - 0.0000i-0.0000 + 0.0000i   0.0000 - 0.0000i-0.0000 + 0.0000i   0.0000 - 0.0000i-0.0000 + 0.0000i   0.0000 - 0.0000i-0.0000 + 0.0000i
Columns 193 through 200
   0.0000 - 0.0000i-0.0000 + 0.0000i   0.0000 - 0.0000i-0.0000 + 0.0000i   0.0000 - 0.0000i-0.0000 + 0.0000i   0.0000 - 0.0000i-0.0000 + 0.0000i
Columns 201 through 208
   0.0000 - 0.0000i   0.0000 + 0.0000i-0.0000 - 0.0000i   0.0000 + 0.0000i-0.0000 - 0.0000i   0.0000 + 0.0000i-0.0000 - 0.0000i   0.0000 + 0.0000i
Columns 209 through 216
-0.0000 - 0.0000i   0.0000 + 0.0000i-0.0000 - 0.0000i   0.0000 + 0.0000i-0.0000 - 0.0000i   0.0000 + 0.0000i-0.0000 - 0.0000i   0.0000 + 0.0000i
Columns 217 through 224
-0.0000 - 0.0000i   0.0000 + 0.0000i-0.0000 - 0.0000i   0.0000 + 0.0000i-0.0000 - 0.0000i   0.0000 + 0.0000i-0.0000 - 0.0000i   0.0000 + 0.0000i
Columns 225 through 232
-0.0000 - 0.0000i   0.0000 + 0.0000i-0.0000 - 0.0000i   0.0000 + 0.0000i-0.0000 - 0.0000i   0.0000 + 0.0000i-0.0000 - 0.0000i   0.0000 + 0.0000i
Columns 233 through 240
-0.0000 - 0.0000i   0.0000 + 0.0000i-0.0000 - 0.0000i   0.0000 + 0.0000i-0.0000 - 0.0000i   0.0000 + 0.0000i-0.0000 - 0.0000i   0.0000 + 0.0000i
Columns 241 through 248
-0.0000 - 0.0000i   0.0000 + 0.0000i-0.0000 - 0.0000i   0.0000 + 0.0000i-0.0000 - 0.0000i   0.0000 + 0.0000i-0.0000 - 0.0000i   0.0000 + 0.0000i
Columns 249 through 256
-0.0000 - 0.0000i   0.0000 + 0.0000i-0.0000 - 0.0000i   0.0000 + 0.0000i-0.0000 - 0.0000i   0.0000 + 0.0000i-0.0000 - 0.0000i   0.0000 + 0.0000i
Columns 257 through 264
-0.0000 - 0.0000i   0.0000 + 0.0000i-0.0000 - 0.0000i   0.0000 + 0.0000i-0.0000 - 0.0000i   0.0000 + 0.0000i-0.0000 - 0.0000i   0.0000 + 0.0000i
Columns 265 through 272
-0.0000 - 0.0000i   0.0000 + 0.0000i-0.0000 - 0.0000i   0.0000 + 0.0000i-0.0000 - 0.0000i   0.0000 + 0.0000i-0.0000 - 0.0000i   0.0000 + 0.0000i
Columns 273 through 280
-0.0000 - 0.0000i   0.0000 + 0.0000i-0.0000 - 0.0000i   0.0000 + 0.0000i-0.0000 - 0.0000i   0.0000 + 0.0000i-0.0000 - 0.0000i   0.0000 + 0.0000i
Columns 281 through 288
-0.0000 - 0.0000i   0.0000 + 0.0000i-0.0000 - 0.0000i   0.0000 + 0.0000i-0.0000 - 0.0000i   0.0000 + 0.0000i-0.0000 - 0.0000i   0.0000 + 0.0000i
Columns 289 through 296
-0.0000 - 0.0000i   0.0000 + 0.0000i-0.0000 - 0.0000i   0.0000 + 0.0000i-0.0000 - 0.0000i   0.0000 + 0.0000i-0.0000 - 0.0000i   0.0000 + 0.0000i
Columns 297 through 304
-0.0000 - 0.0000i   0.0000 + 0.0000i-0.0000 - 0.0000i   0.0000 + 0.0000i-0.0000 - 0.0000i   0.0000 + 0.0000i-0.0000 - 0.0000i   0.0000 + 0.0000i
Columns 305 through 312
-0.0000 - 0.0000i   0.0000 + 0.0000i-0.0000 - 0.0000i   0.0000 + 0.0000i-0.0000 - 0.0000i   0.0000 + 0.0000i-0.0000 - 0.0000i   0.0000 + 0.0000i
Columns 313 through 320
-0.0000 - 0.0000i   0.0000 + 0.0000i-0.0000 - 0.0000i   0.0000 + 0.0000i-0.0000 - 0.0000i   0.0000 + 0.0000i-0.0000 - 0.0000i   0.0000 + 0.0000i
Columns 321 through 328
-0.0000 - 0.0000i   0.0000 + 0.0000i-0.0000 - 0.0000i   0.0000 + 0.0000i-0.0000 - 0.0000i   0.0000 + 0.0000i-0.0000 - 0.0000i   0.0000 + 0.0000i
Columns 329 through 336
-0.0000 - 0.0000i   0.0000 + 0.0000i-0.0000 - 0.0000i   0.0000 + 0.0000i-0.0000 - 0.0000i   0.0000 + 0.0000i-0.0000 - 0.0000i   0.0000 + 0.0000i
Columns 337 through 344
-0.0000 - 0.0000i   0.0000 + 0.0000i-0.0000 - 0.0000i   0.0000 + 0.0000i-0.0000 - 0.0000i   0.0000 + 0.0000i-0.0000 - 0.0000i   0.0000 + 0.0000i
Columns 345 through 352
-0.0000 - 0.0000i   0.0000 + 0.0000i-0.0000 - 0.0000i   0.0000 + 0.0000i-0.0000 - 0.0000i   0.0000 + 0.0000i-0.0000 - 0.0000i   0.0000 + 0.0000i
Columns 353 through 360
-0.0000 - 0.0000i   0.0000 + 0.0000i-0.0000 - 0.0000i   0.0000 + 0.0000i-0.0000 - 0.0000i   0.0000 + 0.0000i-0.0000 - 0.0000i   0.0000 + 0.0000i
Columns 361 through 368
-0.0000 - 0.0000i   0.0000 + 0.0000i-0.0000 - 0.0000i   0.0000 + 0.0000i-0.0000 - 0.0000i   0.0000 + 0.0000i-0.0000 - 0.0000i   0.0000 + 0.0000i
Columns 369 through 376
-0.0000 - 0.0000i   0.0000 + 0.0000i-0.0000 - 0.0000i   0.0000 + 0.0000i-0.0000 - 0.0000i   0.0000 + 0.0000i-0.0000 - 0.0000i   0.0000 + 0.0000i
Columns 377 through 384
-0.0000 - 0.0000i   0.0000 + 0.0000i-0.0000 - 0.0000i   0.0000 + 0.0000i-0.0001 - 0.0000i   0.0001 + 0.0000i-0.0001 - 0.0000i   0.0001 + 0.0000i
Columns 385 through 392
-0.0001 - 0.0000i   0.0001 + 0.0000i-0.0001 - 0.0000i   0.0001 + 0.0000i-0.0001 - 0.0000i   0.0001 + 0.0000i-0.0001 - 0.0000i   0.0001 + 0.0000i
Columns 393 through 400
-0.0001 - 0.0000i   0.0002 + 0.0000i-0.0002 - 0.0000i   0.0002 + 0.0000i-0.0003 - 0.0000i   0.0003 + 0.0000i-0.0005 - 0.0000i   0.0007 + 0.0000i

sigma665 发表于 2008-9-18 09:30

回复 沙发 jww100 的帖子

y = ifft(X) returns the inverse discrete Fourier transform (DFT) of vector X, computed with a fast Fourier transform (FFT) algorithm. If X is a matrix, ifft returns the inverse DFT of each column of the matrix.

ifft tests X to see whether vectors in X along the active dimension are conjugate symmetric. If so, the computation is faster and the output is real. An N-element vector x is conjugate symmetric if x(i) = conj(x(mod(N-i+1,N)+1)) for each element of x.

If X is a multidimensional array, ifft operates on the first non-singleton dimension.

y = ifft(X,n) returns the n-point inverse DFT of vector X.

y = ifft(X,[],dim) and y = ifft(X,n,dim) return the inverse DFT of X across the dimension dim.

y = ifft(..., 'symmetric') causes ifft to treat X as conjugate symmetric along the active dimension. This option is useful when X is not exactly conjugate symmetric, merely because of round-off error.

y = ifft(..., 'nonsymmetric') is the same as calling ifft(...) without the argument 'nonsymmetric'.

For any X, ifft(fft(X)) equals X to within roundoff error.
貌似说的很清楚
页: [1]
查看完整版本: 【求助】IFFT的问题