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ADF4371 Phase Noise Concerns very low at 5,25,50KHz offset to carrier 35dBc

Category: Hardware
Product Number: EV-ADF4371
Software Version: StmIDE
  •     1. Since we haven't reached device optimal performance we are working on it from last 6months still we are wondering we are stuck in phase noise problem. It is worse than we expect 35dBc @50KHz

  • For optimisation of phase noise in Eval-ADF4371 We have tried lot software changes done so far still we are working on it. 
  • From hardware we have tried different types of loop filters and different combination PFD upto 200MHz, 100 MHz by using  ADF4351 as well as 10 MHz 50 PPB Stable clock.
  • Power supply chain we have used Rigol smps as well as cosel, traco power modules changed different combinations
  • My working band is x2&X4. i.e 8-30 GHz here out put power level variation also around 7 dbm at x2, 10 dBm @X4 port. But my concern is phase noise
  • Please help me ou from this problem currently we have changed loop filter is 200KHz 
  • Response to above loop filters wasn't good its around 35dBc@5,15,25 KHz. Spectral quality is degraded. Spectrum is little bit shaking(like small vibration) Please help me out of this problem we have purchased 1.Eval-ADF4371 board and two ADF4371BCCZ SMD IC from ANALOG DEVICES
  • If you have questions about how good my PFD, DC source and loop filters we have used same configurations  for EV-ADF5355 this board phase noise as well as spectrum quality is very good as compared to EV-ADF4371.
  • Hi,

    You stated that you are seeing 35 dB worse result than expected. What is your reference point? Are you comparing your measurement result with ADISIMPLL result? If so, did you model your reference source in ADISIMPLL and used that for the simulation? 



  • Phase noise at 5 kHz, 10 kHz and 25 kHz highly dominated by the reference noise, so you need to select the reference source carefully. 

  • Yes i have simulated both my reference source as well as adf4371 at 5, 10,25KHz  phase noise is approx 90 dbc offset to carrier but in practical my reference source that is feeding to ADF4351 board is generated from ADF4351 synthesizer 120MHz with stable very low spur and phase noise spur at 90 dBc, level of +5dBm.

    1. We have baught new Ev-Adf4371 board yesterday that board is also similar behavior at this time we have used  Rigol SMPS, 120MHz generated reference source from vector signal generator responce is below 

    My airm is to reduce this spur levels to to low extend >60dBc.

    I haven't changed anything from new Eval-ADF4371 board only internal clock removed and set to ext clock 

    At this point my PFD is 120MHz very stable generated from VSG. Monitors on R&S FSVR VSA. 

    I want to see the ideal response of Eval-ADF4371 at frequency 12-18GHz 10,25,50,100,KHz offset to carrier.

    If anyone is having better results share with me with your best performance approch.....