DSP 10 Multirate Signal Processing ???????????????????????????

1
DSP 10Multirate Signal Processing???????????????
????????????
??. ?????? ????????????? ???????
??????????????????????
2
Content

• ?????????????????????????????????????
• ???????????????????????????????????? ???????????
• ???????????????? (Downsampling) ??? ???????????
  (Upsampling)
• ????????? (Decimation ) ??????????????????
  (Interpolation)
• ???????????????????????????????????????

3
?????????????????????????????????????

• ??????...
• 1. ????????????????????????? (CD DAT)
  ????????????????????????
• 2. ???????????????????? ???? ????? Oversampling
  ?? CD
• 3. ??????? noise ?????????????????? (?????????
  oversampling ??? noise shaping)

4
Multitrate Signal Processing

• ?????????? Downsampling, Upsampling Decimation
  Interpolation ??? Oversampling
• Downsampling ??? ????????????????
  ????????????????????????????
• Upsampling ??? ?????????????????????
  ?????????????? zero padding
• Oversampling ??? ????????????????? ??????????
  Nyquist frequency

5
??????????? oversampling ?? CD
??????????????????????????????????? (???????)
Oversampling
??????? LPF
Nyquist frequency (fs/2)
?????????????? ???????????????????????
??? (????????????????,?????????)
?????????????? (??????) ???????? ??? Aliasing
6
Quantization

• ????? quantization ????????? Noise

7
Signals 3 Bit Vs 8 Bit
3 Bit
8 Bit
8
Quantization Errors 3 Bit Vs 8 Bit
9
????????????????? ??????? ??? noise
10
Oversampling - Noise shaping
????? noise ????????? noise Shaper
Noise ??? ?????? ??????????????????????????????
?? CD ???? MASH (Panasonic) ??????? third-order
noise shaper
11
?????????????????????????????????????????
D/A
A/D
?????? ???????
?????? ??????? fs1
?????? ??????? fs2
??? fs1 lt fs2 ???????????????????? fs2 lt fs1
????????? aliasing ???
12
(No Transcript)
13
????????
????? ??????????????????
(Bandlimited)???
?????? ??????downsampling ????????????????
??????? ??????????????? D ?????????????????
aliasing ?? y(n)
??????
D/A
A/D
14
????????????????? D/A ??? ???
??????????? ???????
?????????????????? A/D ?????????????
??????????????? aliasing
2 ???????
???????
15
???????????
????????????????? D 3 ????? y(n) ??????? x(n)
(???????aliasing)
16
Downsampling
?????????????????????? D ????
17
???????????downsampling
D2
D3
dsp_10_2.eps
18
???????????????? downsampling
D2
D3
dsp_10_3.eps
19
Upsampling
20
??????????? upsampling
I2
I3
dsp_10_4.eps
21

???????????????? upsampling
I2
I3
dsp_10_5.eps
22
???? ???? ???????????? downsampling ???
upsampling ??????????????
????????????????? downsampling ?????? sampling
?????? ??? sampling ??????
23
???sampling ????????????? D ?????????????????????
??? D ????
???????
??????????????? (aliasing formula)
downsampling
sampling
24
??????????????? aliasing ???
??? D3
???? aliasing
25
????????? (Decimation)
??????????? (decimator) downsampler?????????????
? (??? aliasing)
??????????
LPF
????????? 1
26
??????????????? (Interpolation)
????????????????? (interpolator)
upsampler??????????????
LPF
??????????
27
?????????????? upsampling ??? Interpolation
upsampling
Interpolation
dsp_10_6.eps
28
???????????????????????? Compact Disc
???????????
64fs,1 bit
fs,20 bit
fs,20 bit
64fs,1 bit
Decimation filter
Interpolation filter
PCM Recorder
Delta-Sigma Modulator
1-bit ADC
front end
64fs,1 bit
Analogue Low pass filter
Pulse code modulation
?????????? (record)
???????????? (playback)
29
?????????????????????????????????????????????
?????? cascade ???????????????????? ????
??????????????? ??????????? ?????????????????????
?????????????
????????? 1
LPF
LPF

30
????????????????????????????????
LPF
???
??????? LPF ??????????
???????????????????????????????? ???????
31
????????
??????????? x(n) ??????????????? xa(t)
??????????????? 8 kHz ????????????? ?????? y(n)
??? ????????????? 10 kHz??? x(n)
???????????????????????
??????
????????? ??????????????????????????? ???
??????????????????????? !
LPF
fsx 8 kHz
fsy10 kHz
32
??????????????????????????? CD ?? DAT
(Digital Audio Tape) CD ??????????? 44.1 kHz
DAT ??????????? 48 kHz
????????
????????????
??????????????????????????????????????????????????
????????
33
?????????????????????????????????????????? ???
?? ??????????????????????????????????????
??????
LPF
fDAT48 kHz
fscd 44.1 kHz
LPF ?? ???????????????? 160 ?????
???????
?????? SACD ??????????????????????????????????????
?
34
Super Audio CD
64fs,1 bit
64fs,1 bit
PCM Recorder
1-bit ADC
front end
Analogue Low pass filter
Pulse code modulation
?????????? (record)
???????????? (playback)
35
?????????????????? SACD
36
????

• ??? decimation downsampling lowpass
• ??? interpolation upsampling lowpass
• ???????????? Decimation ??? Interpolation
  ??????????????????????????????????????????????????
  ?????????
• ?????????????? ???? SACD ????????????????????????
  ???????????????? ???? oversampling ???
  ????????????????