NI-PXIE-6368_AO/AI_Dual_Tone_Generation and Capture_(Inter modulation Distortion)

[sagar7077bishwas]

Hi Team,

Dual tone of 20Khz and 25Khz wave form is generated at 1MSPS sampling rate with NI-PXIE_6368_AO channel and the same is captured with NI_PXIE_6368_AI_channel at 1MSPS sampling rate below are spectrum of the captured wave.

Input Wave Form:

Actual Spectrum:

Zoomed in spectrum:

while studying the spectrum it seems that every 5Khz (5,10,15,20,etc...) spurs are occurring repeatedly.
Could you please suggest how to avoid this spurs while measuring IMD?



Regards,
Sagar

[santo_13]

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@sagar7077bishwas wrote:

Hi Team,

Dual tone of 20Khz and 25Khz wave form is generated at 1MSPS sampling rate with NI-PXIE_6368_AO channel and the same is captured with NI_PXIE_6368_AI_channel at 1MSPS sampling rate below are spectrum of the captured wave.

Input Wave Form:

Actual Spectrum:

Zoomed in spectrum:

while studying the spectrum it seems that every 5Khz (5,10,15,20,etc...) spurs are occurring repeatedly.
Could you please suggest how to avoid this spurs while measuring IMD?



Regards,
Sagar

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How are you ensuring a continuous generation? regenerate from memory?

How are the two-tone signal generated, from file or from formula?

[Henrik_Volkers]

And if you try 20kHz and 26kHz ?   

But my first guess also would be in the same direction of santhosh: Generation : Do you repeat a block of 2.5 ms length ?  

Another point: 

You want that the output and the input sample are delayed by half a sample. (allow the output to settle) 

In Software: use different edges of the sampleclock for AO and AI (or different sampleclock delays  if supported)

Hardware : build a 500ns delay line ... about 100m RG58 😄