Digital Signal Processing Reference
In-Depth Information
5,00
5,0
4,0
3,0
2,0
1,0
0,0
Input: sinusoidel Signal
2,50
4,5
4,0
3,5
3,0
2,5
2,0
1,5
1,0
0,5
0,0
0,050
0,045
0,040
0,035
0,030
0,025
0,020
0,015
0,010
0,005
0,000
Quantized siusoidal signal
0,00
Quantization noise
-2,50
-5,00
50
150
250
350
450
550
650
750
850
950
25
50
75
100
125
150
ms
Hz
5,00
5,0
4,0
3,0
2,0
1,0
0,0
4,5
4,0
3,5
3,0
2,5
2,0
1,5
1,0
0,5
0,0
0,050
0,045
0,040
0,035
0,030
0,025
0,020
0,015
0,010
0,005
0,000
Input: sinusoidel Signal
2,50
Quantized siusoidal signal
0,00
Quantization noise
-2,50
-5,00
50
150
250
350
450
550
650
750
850
950
25
50
75
100
125
150
ms
Hz
Illustration 149:
Quantization of a sampled signal
There are three signal curves to be seen in the time domain: the sinusoidal analog signal continuous in
time and value, the time and value discrete quantized sample signal (step curve) and the time and value
continuous difference signal in the centre of the Illustration.
At the top you see an extremely inaccurately quantized signal. Try to determine the number of allowed
quantized values within the measured region of -5V to +5V. The spectra of the three signals are shown on
the right. The spectrum of the sine shows a single line to the far left on the vertical axis. Below this is the
spectrum of the quantized signal. Additional small irregular lines are to be seen clearly within the
frequency domain. The difference signal incorporates the quantization noise. The amplitudes reach 0.05 V.
By increasing the number of possible quantization steps (how many are there here?) the step curve of the
quantized signal appears to be much nearer the analog signal: As a result the difference voltage is much
smaller. The quantization noise is less than 0.02V.
Both representations are so roughly quantized that they would not be acceptable in a technical acoustic
sense.
