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The question of using Visual Analog to evaluate AD9874

I have downloaded the ADI Visual Analog Software and AD9864_74 SPI GUI to evaluate the AD9874. I use the test conditions as below:

IF =15.75MHz, -12dBm
LO=18MHz, 1 vp-p
the AD9874 registers are setting as below:

I use the Visual Analog software, the AD9874_16b average FFT, the data capture is setting as below:

And the result is as below, why result looks so bad?

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  • Yes, I am sure using the "windowed FFT" and set to Blackman-Harris. Actually, I followed the quick start of the "AD9864/AD9874 EVB Evaluation Board User Guide", using the configuration as Figure 2a, the result of the windowed FFT is the same as I posted.

    The time domain IQ plot show a sine wave is not -3.3dBFS. It appears as below:

    So How do I get the right result, for the listing conditions?

    Visual analog default setting,M=15(decimation factor 900)

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  • Yes, I am sure using the "windowed FFT" and set to Blackman-Harris. Actually, I followed the quick start of the "AD9864/AD9874 EVB Evaluation Board User Guide", using the configuration as Figure 2a, the result of the windowed FFT is the same as I posted.

    The time domain IQ plot show a sine wave is not -3.3dBFS. It appears as below:

    So How do I get the right result, for the listing conditions?

    Visual analog default setting,M=15(decimation factor 900)

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