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Original question:

AFE4404: AFE SNR measurement - getting started

AFE4404: AFE SNR measurement - getting started

John11513
Expert 5720 points
Part Number: AFE4404

Hi,

I also have two questions about SNR measurement of AFE4404:

1) About receiver SNR, if this measure can be comparable with datasheet: applying a 0.5*FSR signal to input, calculate the STDEV of ADC data and calculate the SNR as: SNR=20*log10(2^22/stdev(ADC data)). 

The datasheet specify SNR over 20Hz bandwidth, should a digital filter be applied to ADC data to limit the bandwidth to 20Hz before calculate the SNR?

2) How to measure the SNR of transmitter?

Thank you,

John

  • 0
    TI__Genius 12575 points
    Hi John,

    Your formula is correct for the Nyquist bandwidth.
    For 20Hz SNR, you can calculate the noise in this bandwidth using the FFT. if you plugin this noise ( upto 20Hz) in your calculations, you will get SNR for 20Hz.

    There is no easy way to calculate the SNR of transmitter alone. One way is to do some kind of electrical loop-back where output of the transmitter is fed back to receiver and we calculate the SNR. However in this case you will get the SNR for both RX and TX combined.

    For only TX SNR, we may have to use external ADC or some instruments, provided external component has pretty low noise.

    Regards,
    Prabin