A question confused me for quite a while:
In a generic RF PLL with phase detector, Loop filter, VCO and loop divider /N,  if the division ratio N is scaled down to N/2, the reference frequency is 2xfref, while ALL OTHER components are kept the same, how will the PLL output spectrum change?  Close-in phase noise floor?  Far-out phase noise?

Please comment on it.  

thanks!