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About HMC764LP6CE frequency lock and phase noise issue

Question asked by on Dec 19, 2014
Latest reply on Jan 16, 2015 by rbrennan

Dear Sir,


We found the problem for HMC764 on frequency locking under integrated mode & bad phase noise once locked.Below is our inquiry, pls help to clarify. Thanks.

1. How is the register setting sequence due to can't find it on datasheet ? Below is our register setting & writing sequence.

   1) 00h 1 RST

   2) 02h 3 R=3

   3) 03h 174 N=372

   4) 0Bh 878 negative slope

      Fref: 30MHz (external SG)   Fout: 7.44GHz

2.How to turn on frac-N mode ? As datasheet description as below, it doesn't work while setting reg 9 [9:7] to "100" (for 220uA charge pump offset) & 011 for reg 6[12:10].

           Note: To Enable Frac Mode:  Set Reg 6 [12:10]= 011

            Also, Reg 9[9:7] or Reg 9[4:2] must be adjusted to mitigate spurs in frac mode (Dn or Up Leakage)

3.For N value described as below, it shouldn't need to divide by 2. In reality, the value of N needs to divide by 2 as above "N=372" for     7.44GHz frequency out. If I misunderstand for it ?


4.For phase noise and loop filter is as below once lock ,it really bad on SSB. Do you have some recommend for it ?


Loop filter set.jpg