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Using ADF4159 for a CW Radar application


im studying electrical engineering at RWTH Aachen. Right now im doing my master thesis at the Chair of High Frequency Electronics.
For my thesis I'm going to develop a radar system which will be used for tracking purposes.
At the moment im trying to figure out what parts I'm going to need for my application.
While researching, I stumbled upon the ADF4159(, which I want to use as a PLL for my frequency synthesis (the PLL will be used in combination with the ADF5901). As im going to develop a continuous radar, my main goal with this PLL is to operate it at a costant frequency. While studying the datasheet, I was able to spot that there is a register (DB31; p.15) for using/disabling a "Ramp On"-function.
So here is my question: If i set the "Ramp On"-Bit to zero, will the PLL operate at a constant frequency instead of functioning as a FMCW?
And if thats not the case, could you recommend a different PLL for my desired purpose? I would be absolutely grateful if you could enlighten me on this matter. Thanks in advance! Sincerely yours Niklas
  • Yes, if ramping is disabled then ADF4159 will lock the ADF5901 output to a constant frequency.

    If you don't require the ramping features of ADF4159, you might consider using ADF5902 for your system. This is a 24 GHz FMCW radar with integrated PLL, but the ramping feature can also be turned off to lock the output to a constant frequency.

  • Thanks a lot! Sorry for my late reply, didnt check back for a longer period of time.

    After talking to my supervisor, we decided to work with the ADF5902, so your reply was really appreciated:)

    While checking the datasheet, I came up with another question: In order to drive the VCO it seems that I have to connect the Charge Pump to the V_Tune port with a loop filter. As I dont have any experience with this and didn't find any additional information, could you tell me how a suited loop filter would look like or give me any advice where I can read up on this topic?

    Again, many thanks in advance!

  • Hi, We have free software available called ADIsimPLL which can be used to model PLL/VCO performance and to design loop filters. You can model the ADF5902 by selecting ADF4159 as your chip, then the ADF5901 as the VCO. You will be locking the PLL to the VCO/2 frequency so in the simPLL wizard set your PLL frequency to half the output frequency.

    This guide gives information on modelling FMCW ramps and tuning your loop filter design for optimum ramping performance



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