LMX2594: 当开启RFB分频输出时，出现意想不到的的杂散频率

Hi there,

I think the 100kHz could be come from LMX2572.

Could you try set LMX2572, register R1, CAL_CLK_DIV = 0x1?

Thanks for your reply. It does not work even through i changed them both.

I have more information for you is that the sutiation only occured when the system output frequency range from 2300MHz to 4300MHz.

Hi Neal,

If you use external reference clock to LMX2594, do you still see the 100kHz spurs?

Between 2300 and 4300MHz, are the spurs always at 100kHz offset?

Hi Noel,

  None spurious frequency presented when instead of LMX2572  by external reference.

  I did these two experiment here,

  CASE  I, LMX2594 configured as 3100.1MHz while reference is 99.671875 MHz by dividing LMX2572's output down to 64.

                 The both LMX2572 and LMX2594 were presenting spurs at its RF output port as far as 100kHz

  CASE II, LMX2594 configured as 12400.4MHz while reference is same as CASE I.

                 None spurs presented !

Hi Neal,

My guess was right, the 100kHz spurs was due to the 100MHz reference of LMX2572. 

is LMX2572 output frequency fixed at 99.671875MHz? If this is the case, after LMX2572 is locked, set R2[10] = 0. This will stop the internal clock which is used for VCO calibration. 

Hi Noel,

     The spurs are still when LMX PLLs are set to 0x100 to Reg2 after they lock.

Hi Neal,

Would you please measure the output of LMX2572? set the spectrum analyzer start/stop freq to 200MHz/3200MHz.