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Eval ADC for -140dB THD+N Measurement


I need to buid a Noise/Distorsion meter for further product qualification.

I've got mains fonctionnal blocks:

- fixed oscillator, -140db THD+N @1kHz, 10Vpp

- oscillator matched suppression notch filter

- discrete 400pV/Hz Amplifier G=1k or 10k.

For G=1k, a -150dB (40dB over input noise) is now -90dB, and could fit in average ADC dynamic range. For G=10k, a -170dB (20dB over input noise) appears to be -90dB too. But we also need an awesome oscillator!

I can't afford a brand new fft oscilloscope, keeping money for prototyping.

Thus I am looking for an ADC evaluation board with a software providing fft, THD, noise measure and sample averaging.

I've found that AD7124-X evaluation software would fit exactly my application but those converters are meant for DC measurement. 

AD7690 and AD7982 could be good choices, but I don't know if sample averaging is available in evaluation software. I wanted averaging to get better dynamic range, but maybe simply downclocking would improve DR.

After going through several pulSAR product documentation, none have digital filter inside. (So no averaging function in eval-softwarw?)

Then I should go with adc eval board using the fpga board which have a common fft software that fit my requirement.

But I like the system to run with eval-sdb-cb1z to keep it cheap, also I saw several compatible eval board as ad7124, ad5544 and ad5380 that could be usefull to run other in-house tests.

Is there a adc eval board that will fullfill my requirements? FTT "DC" to 200kHz, -90dB or better THD+N over the band, averaging using eval software.

Maybe I am over designing the thing and AD7690 or AD7982 will be OK..

Thank you for your support.

Best regards,