Hello team,
We have designed a PLL card taking ADF4159 EVM as reference. Our requirement was to generate a frequency between 9.3GHz and 9.45GHz, so accordingly we have designed the loop filter in the card and the VCO we used was HMC510LP5E. Reference input frequency was 100MHz.
One thing that differs our designed card and EVM design was the inclusion of T attenuator along with the PI attenuator. We included only the PI attenuator. Due to which we assume that RF IN (VCO/2 of the HMC510LP5E) that was fed to PLL chip has exceeded the RF input power range i.e., -10 to 0dBm.
Our queries are
1. Can the exclusion of T attenuator affect the phase noise of the RF signal?
2. We are able to see spurs at -50dBc/Hz to peak signal. Can the spurs be generated due to non-presence of T attenuator in our design?
3. Can it lead to thermal shutdown of the PLL? We observed the thermal shutdown of PLL when the pll was kept in thermal chamber where temperatures were greater than the 55 degree centigrade.
Your answers will be helpful.
Thanks,
GAR.