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jiangwp
Joined: 27 Jul 2004
Posts: 184
Helped: 9
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 31 Dec 2004 7:40 about relation between amplitude of input signal and SNR |
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We know the
SNR=(the RMS of input signal)/(the RMS of noise) (I)
or . a input sine signal: Vpsin(wt)
SNR=(6.02N+1.76) dB (II)
It is not related between the SNR and the amplitude , only effected by the N.
In the mean while, we estimate the SNR from the above the equation (I) ,
also there is no realtion between the amplitue and the SNR.
but , we test the DAC/ADC chip , we will find the SNR increase with the increase of the input signal amplitude unlil overloading . Why?
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glenjoy
Joined: 01 Jan 2004
Posts: 1021
Helped: 47
Location: Philippines
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| 31 Dec 2004 8:39 about relation between amplitude of input signal and SNR |
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| Amplitude of a signal can be the Average or the Maximum Amplitude, therefore you can derive the RMS from it.
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reltol1
Joined: 15 Dec 2004
Posts: 19
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| 31 Dec 2004 10:46 Re: about relation between amplitude of input signal and SNR |
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Eq. (II) comes when the input signal is full scale.
Then surely SNR increases when you use a larger amplitude input.
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Hughes
Joined: 10 Jun 2003
Posts: 712
Helped: 84
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| 31 Dec 2004 13:33 Re: about relation between amplitude of input signal and SNR |
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| The equation 'SNR=(6.02N+1.76) dB' represents the relation in ideal ADC/DAC. In ideal ADC/DAC, the N (noise) is quantization noise only. But in a pratical ADC/DAC, there will be other noise sources, such as thermal noise. These noise sources are independent on the signal amplitude. As a result, the SNR in a pratical ADC/DAC may be worse than that predicted by the above equation, and the SNR increases as the signal amplitude increases.
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