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ADF4351 output signal

Question asked by serg-ant on Dec 6, 2012
Latest reply on Dec 10, 2012 by serg-ant

Good evening!


I use ADF4351 synthesizer to generate 2.46 GHz output sine.

Reference frequency is 25.625 MHz, I'm using integer-N mode, so only N counter is currently utilized.

N counter value = 96

Cycle slip reduction is on, ABP is on. Digital lock detect shows, that PLL is locked.

Loopback filter bandwidth is ~3 kHz, phase margin ~42 deg (according to ADISimPLL  simulation).


Is it OK to have the output signal spectrum like on attached picture? I don't know, should I try to make output signal better (actually I would like it to be better) or is it normal for this synthesizer?


P.S. Don't look at absolute level of signal, unfortunatelly I don't have RF probe for 2.5 Ghz right now, so I use 500 MHz probe.