ADF4368 Harmonics

Question

I am using ADF4368 as a sampling clock generator for AD9209, where VCO of ADF4368 is fixed to 7.2GHz and output is fixed to 3.6GHz. Second, third Harmonics of ADF4368 output is quite high as per ADF4368 datasheet. Does it affect SNR of my ADC?

emrecangidik · Accepted Answer

Hi Manikandan, 
 Do you mean the second and third harmonics are higher than the datasheet specifications? 
 From a clocking point of view; 
 ADF4368 is designed to provide a high slew rate signal with a low jitter. To achieve a high slew rate, ADF4368's buffers generate a square wave-ish signal instead of pure sinusoidal. These harmonic contributions help to achieve a square wave-ish signal. Due to the AM-PM conversion, higher slew rate signals help to achieve lower jitter which improves the SNR performance of the data converters. 
 Theoretically speaking, if the generated signal behavior is as expected and not disturbed by external components, these harmonics shouldn't affect the SNR of the ADC. 
 Thanks, Emrecan)

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ADF4368 Harmonics