I used ADF5356 PLL synthesizer. And i use reference oscillator freq is 10MHz with initially offset 0.1ppm and stability is 10 ppb. I need to output freq is 3750 MHz.

Expected output result:

10MHz × 0.1 ppm = 1 Hz

So, i use doubler option.

10 MHz × 2 = 20.000002 MHz

VCO output 3750 MHz

3750 MHz × 0.1 ppm = 375 Hz

Total output freq is = 3750.000375 MHz

Actual output:

Actual output is offset vary every power on and off for system. Every power on different offset came.

I did not get stable offset. Loop filter 5 KHz

Please help this problem.

Thanks and Regards Purushothaman

  • 1
    \$\begingroup\$ Please ask a specific question and edit \$\endgroup\$
    – Voltage Spike
    Mar 4 at 16:49
  • \$\begingroup\$ What are you using for the reference oscillator? \$\endgroup\$
    – RussellH
    Mar 4 at 18:21
  • \$\begingroup\$ Leave the reference oscillator running. Lock the frequency counter to the reference oscillator. Are you using a frequency counter, or some other method like a spectrum analyser to measure frequency? Do you still get the same variation when you switch the PLL on and off? If yes, it's a PLL problem. If not, it's an oscillator (including the oscillator in your freqeuncy counter) problem. Do the experiment, and edit the results into your question. \$\endgroup\$
    – Neil_UK
    Mar 4 at 18:51
  • \$\begingroup\$ How are you measuring the frequency? Hope you are using averaging. \$\endgroup\$
    – sai
    Mar 9 at 7:11


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