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ADS5402 / FFT results

Toshiyuki
Mastermind 7075 points
Other Parts Discussed in Thread: ADS5402, ADC12D800RF

Hi,

We have evaluated ADC12D800RF and ADS5402.and we compared the two FFT results.

*Input Signal - 844MHz、Sampling Clock - 500MSPS、Input Signal and Sampling Clock were generated by Signal Generator.

ADS5402 had property degradation around the 156MHz.

Is there something that is considered to be the cause of that?

Best Regards,

Kato

  • 0
    Mastermind 7075 points

    Hi,

    I haven't got your answer yet.

    ADS5402 had property degradation around the 156MHz in FFT results.

    Is there something that is considered to be the cause of that?

    I'm looking forward to hearing from you.

    Best Regards,

    kato

  • 0 in reply to Toshiyuki
    TI__Mastermind 29220 points

    Hi,

    I don't know what would produce noise with that shape around the fundamental.   We *do* usually see a smaller rise in the noise floor around the fundamental that is simply the passband of the bandpass filter that we use on ths signal from the signal generator.  For example, if the analog tone is 100MHz and the filter we use has a 3% passband thenthe width of the phase noise that the filter lets through can be see to be about 3MHz around the fundamental.  But that is usually not as pronounced as what is seen in the plot you attached, and there seems to be a dip right in very close to the fundamental.

    Is this setup using a bandpass filter on the signal from the signal generator?  What is the source for the clock, and could the clock and analog tone be made coherent so that the Blackman Harrs windowing function could be taken out of consideration? 

    Regards,

    Richard P.