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Can AD9956 generate fine-tuned sine output and perform a sweep in frequency bands above >400MHz?

Question asked by Segretal on Mar 2, 2017
Latest reply on Mar 16, 2017 by Segretal

Dear EngineerZone Community,


I have a fairly simple question regarding AD9956 evaluation board capability or not to generate and sweep finely-tuned sine wave-forms above >400MHz.


Currently we are utilizing a AD9859-EVAL to generate and sweep sine wave signals across 114-164MHz, fed to an antenna element.



However our application requires that the above function be extended to 2 much higher frequency domains of 750-905 MHz and 1645-1745 MHz, with an incremental sweep step of 25kHz.


Hence we were considering of utilizing a AD9956-EVAL because according to the datasheet  "enables the synthesis of digitally programmable, frequency-agile analog sinusoidal wave-forms up to 2.7 GHz".


However under closer examination of the datasheet, and if I'm not mistaken, the DDS block can only receive a system clock only up to 400MHz and for higher frequencies the RF divider must be engaged.



Therefore I am bit confused here and I would be grateful if you could help me:


  1. Does this mean that the output frequency can only be fine-tuned and swept (eg. via the linear sweep mode option) in frequency bands only below <400MHz (eg. 300-350MHz) ? 

  2. Am I right to assume that for frequencies above >400MHz, it is only possible to output integer divisions of the VCO frequency determined by the RF divider value (eg. 1,2,4 or 8), but not fine-tune it via the FTW and perform a linear sweep in specific frequency bands (eg. across 750-905 MHz and 1645-1745MHz and 25kHz sweep step)? 
  3. Is there perhaps some specific way that AD9956-EVAL can be configurated that eludes my attention and can enable such a functionality?



Thank you for your time and I look forward to your replies!