Question about ADC measurement

[Lantis]

A 90MHz sampling rate(conversion rate) 6bit ADC, for testing convenience, I combine two consecutive ouput codes into a 12 bits data outputs with 45MHz.
Is it ok to perform FFT on only 6bits outputs? (that is, only odd output code of 90 MHz samples.)

Thank you very much.

 

[fxxjssc]

hi Lantis,
nyquist or oversampling one?
seem former one,
advise you record data and perform fft in matlab
that would be better
may helps

 

[gsuarez]

I agree with fxxjssc. Record the data and code a simple fft routine in matlab. Also you can use the National Semiconductor WaveVision 4 software.

www.national.com/appinfo/adc/wv4.html

This software is inteded for their boards, but it has the capability of importing data from files (like .dat .txt etc). Since it uses the fft algorithm you need data in multiples of base 2. The software gives you several info (THD, harmonics, SFDR, SINAD, ENOB, data histograms). Also provides fft windowing options. Let me know if this works for you.

George