Queries about AD10200

Dear Supporter,

I used AD10200 in my project. I tested AD10200 with signal generator. The sampling clock is 105MHz. FFT N=65536.

When I input 10MHz sine wave, the FFT result looks good. Please see below pic.

but when I input 41MHz, 71MHz or 105MHz respectively, the results look poor, please see below pics.

I am not sure why the waves are abnormal. Could you please help give me some comments on the issues?

Thanks in advance for your help!

Br,

Wayne

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  • 0
    •  Analog Employees 
    on May 13, 2014 7:43 PM

    Hello Wayne.

    From your last two FFT plots specifically, you have a great deal of spectral leakage or skirting. This is typical when you have lost coherency ( not an integer number of cycles within the data window)

    Have you applied a windowing technique on the data prior to the Fourier analysis? A Blackman Harris Window should work.

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  • 0
    •  Analog Employees 
    on May 13, 2014 7:43 PM

    Hello Wayne.

    From your last two FFT plots specifically, you have a great deal of spectral leakage or skirting. This is typical when you have lost coherency ( not an integer number of cycles within the data window)

    Have you applied a windowing technique on the data prior to the Fourier analysis? A Blackman Harris Window should work.

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