Hi i am trying to use ADF4355-2 with fractional -N mode. But spur products are too strong, like -39 dBc . Here the images when i set output frequency to 1720,002 MHz . What can i do to get rid of these spurs. Other image is my ADF4355-2 settings.
For the o/p channel selected, the spurs 4kHz away from the fundamental are integer boundary spurious, you can reduce the levels
1) reducing the loop filter bandwidth
2) or if possible use frequency planning ( change the PFD )
see attached article , regards,
The VCO step size should equal the channel spacing x o/p divider, as you have specified 100KHz, then the VCO step size = 200kHz, can you try the settings here (using our evaluation software) for an o/p of 1720.002MHz...note in R12 the ADC clock freq should be < 100kHz, also your fundamental signal levels look very low, how are you interfacing to the RFOUTA?
Hi, thanks for the answer. I re-programmed the registers according to the your software. But nothing is changed. I am using 30dB attenuator and 4 way splitter so thats why my output is low.
Don't you see these spurs on evaluation board ?
I had designed my own ADF4355-3 board . In that I unfortunately connected pin 23 and 24 to 3.3v does any thing happens to chip? Does these two pins effect the loop filter and mux pins to produce output because I am not getting output. Please help me out with this situation.I want to know the output of ADF4355-3 depends on pin 23 and pin24 voltages?
I also want to know whether Vvco and Vdd can be given same 3.3v from one regulator for adf 4355-3 board?
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