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ADF4356 strong spurs

Question asked by Coney on Mar 3, 2017
Latest reply on Mar 9, 2017 by Coney

Dear technical support,

  I'am debuging the ADF4356. But there are very strong spurs as high as -66dBc

  It's my own board.

  LoopFilter bandwidth is 40KHz,

  f_ref = 140MHz,   R_div = 2,     f_pfd = 70MHz,       Icp = 0.9mA

  In this photo,f_vco = 4050MHz,10MHz away from f_pfd's integer boundary.

  IBS is far away from the carrier frequency. When the carrier frequency is 30MHz away form f_pfd's integer boundary, it's about -78dBc. I can't tolerate it.

  I have searched for the answer for a long time and tried many ways. I hope you can help me .

  Thank you very much.

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