# How can i calculate the SNR from the ADC data

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#### rusty629

##### Newbie level 1 calculation of snr in digital signal

Hello everyone，i have a problem with my ADC data.
I want to calculate the ADC's SNR,and i 've done FFT using MATLAB,i found some matlab program to calculate the SNR,but many of some can not work,so is there anyone can help me with it ,or tell me where i can find answers.
thank you very much!!

#### del-sig

##### Newbie level 5 Hi

I got sigma delta modulator design (.mdl files) from my senior. I wanna simulate and have to calculate SNDR/SNR from fft plot using matlab. I'm using hanning window to get fft. I was wondering how to calculate snr/sndr/dr from matlab.

#### iffe

##### Newbie level 4 Hi all,

Sorry to bother you. I am new in this forum. I have the same problem of the calculation of SNR. Please help.

Sine wave is quantized and then I have calculated its SNR using FFT. The coherence condition with windowing as well is implemented to avoid leakage in the adjacent frequency bins.

I am unable to calculate the SNR accurately with different resolution of quantizer (ADC).

If I use a standard formula for quantization noise power (Q^2 / 12), the SNR corresponds with the theoretical formula of SNR (SNR = 6.02*NoOfBits + 1.76) but when I try to use my own calculated noise power, the SNR does not corresponds with the theoretical formula with different resolution.

I think, I am not calculating the noise power in the correct way. I have considered the noise spectrum starting from 2nd bin to input bandwidth.

By the way I am using the formula of SNR = 10*log10(RMS_of_Signal/Mean_of_RSS_of_Noise)

/Iffe

#### eziggurat

##### Full Member level 6 I remember calculating SFDR for 100 Mhz ADC. I see if I can find the C code for it and extrapolate equation and post it here. That might help you on the SNR.

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