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AD9255:Spurs around sub-harmonics of the sample clock

Question asked by Mohandas on Aug 11, 2016
Latest reply on Aug 23, 2016 by Mohandas

I am using AD9255 for an aerospace radio receiver product. We are seeing some spur in the FFT of the ADC output. It appears that the spurs are around fs/2 and fs/4. IOW if the fundamental signal into the ADC is at 39 MHz and 100.8 MHz is the sampling clock. I am seeing a spur at 11.4 MHz. This appears to come from 39 - 50.4 MHz (or 39 - fs/2). Can you please explain how this sub-harmonics of the sampling clock generate spurs?

 

Thanks,

Mohandas Amarnathan

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