DSP101

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

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

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

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

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Multitrate Signal Processing

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

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

• ????? quantization ????????? Noise

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Signals 3 Bit Vs 8 Bit
3 Bit
8 Bit
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Quantization Errors 3 Bit Vs 8 Bit
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????????????????? ??????? ??? noise
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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 ???
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(No Transcript)
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????????
????? ??????????????????
(Bandlimited)???
?????? ??????downsampling ????????????????
??????? ??????????????? D ?????????????????
aliasing ?? y(n)
??????
D/A
A/D
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????????????????? D/A ??? ???
??????????? ???????
?????????????????? A/D ?????????????
??????????????? aliasing
2 ???????
???????
15
???????????
????????????????? D 3 ????? y(n) ??????? x(n)
(???????aliasing)
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Downsampling
?????????????????????? D ????
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???????????downsampling
D2
D3
dsp_10_2.eps
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???????????????? downsampling
D2
D3
dsp_10_3.eps
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Upsampling
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??????????? upsampling
I2
I3
dsp_10_4.eps
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???????????????? upsampling
I2
I3
dsp_10_5.eps
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???? ???? ???????????? downsampling ???
upsampling ??????????????
????????????????? downsampling ?????? sampling
?????? ??? sampling ??????
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???sampling ????????????? D ?????????????????????
??? D ????
???????
??????????????? (aliasing formula)
downsampling
sampling
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??????????????? aliasing ???
??? D3
???? aliasing
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????????? (Decimation)
??????????? (decimator) downsampler?????????????
? (??? aliasing)
??????????
LPF
????????? 1
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??????????????? (Interpolation)
????????????????? (interpolator)
upsampler??????????????
LPF
??????????
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?????????????? upsampling ??? Interpolation
upsampling
Interpolation
dsp_10_6.eps
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???????????????????????? 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)
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?????????????????????????????????????????????
?????? cascade ???????????????????? ????
??????????????? ??????????? ?????????????????????
?????????????
????????? 1
LPF
LPF

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????????????????????????????????
LPF
???
??????? LPF ??????????
???????????????????????????????? ???????
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????????
??????????? x(n) ??????????????? xa(t)
??????????????? 8 kHz ????????????? ?????? y(n)
??? ????????????? 10 kHz??? x(n)
???????????????????????
??????
????????? ??????????????????????????? ???
??????????????????????? !
LPF
fsx 8 kHz
fsy10 kHz
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??????????????????????????? CD ?? DAT
(Digital Audio Tape) CD ??????????? 44.1 kHz
DAT ??????????? 48 kHz
????????
????????????
??????????????????????????????????????????????????
????????
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?????????????????????????????????????????? ???
?? ??????????????????????????????????????
??????
LPF
fsDAT48 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)
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?????????????????? SACD
36
????

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