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Original question:

ADS1602: Inquiry on SNR and ENOB Calculation for ADC Data

TMS320F28388D: Inquiry on SNR and ENOB Calculation for ADC Data

Daniel Park
Prodigy 110 points
Part Number: TMS320F28388D

Tool/software:

Hi TI Support Team,

I have data sampled at 1KHz using an ADC. The input signal is a 3.0Vpp 200Hz sine wave. I would like to calculate the SNR and ENOB from this data and have a few questions.

I understand that SNR is calculated by the ratio of the signal power to the noise power. For the signal power, I would take the magnitude at 200Hz, but for the noise power, should I sum the power of all other components or take the average of the power of the remaining components?

From my research, it appears that many sources suggest summing the power of all the remaining components. Is this correct?

If so, I have the following concerns:

The number of bins in the FFT array is equal to the number of input samples, which depends on the duration of the measurement. Therefore, calculating SNR from the FFT result of a 1-second collection versus a 10-second collection would yield a 10-fold difference. Since SNR is a measure of the quality of the ADC circuit, it doesn't seem accurate for the quality to worsen with longer measurement durations.

What is the correct method for calculating the power of the noise components?

Thank you for your assistance.

  • 0
    TI__Mastermind 34405 points

    Hi Daniel,

            For the noise component, the proper way is to use RMS calculation to represent the noise component over a period of time.  Your denominator would then be:

       sqrt(∑noise2/n).  Numerator would just be the magnitude of the fundamental signal which is sqrt(signal).  More samples mean better resolution and improvement in SNR.

    Rgards,

    Joseph

  • 0 in reply to Joseph Casuga
    Prodigy 110 points

    Hi Joseph,

    Thank you for your kind explanation. By following the method you suggested, the SNR value will be calculated to a good figure. I am not sure if modifying the formula is the right approach to achieve good results. My purpose in calculating the SNR is not for personal satisfaction but to prove performance to someone else. Therefore, I need to provide evidence that this method of calculation is correct. If you have any reference materials that can prove the calculation method you mentioned is accurate, I would appreciate it if you could share them with me.

    Regards.