PLL total noise calculation

[AdvaRes]

Hi all,

Given various noise sources, how to calculate the total transfert function noise of a PLL ?

I calculated Φout=F1×ΦRef, Φout=F2×Φtune and Φout=F3×ΦVCO. Is the total

transfert function

Φout_Total=(F1×ΦRef)+(F2×Φtune)+(F3×ΦVCO)

 

[erikl]

Given various noise sources, how to calculate the total transfert function noise of a PLL ?

I calculated Φout=F1×ΦRef, Φout=F2×Φtune and Φout=F3×ΦVCO. Is the total
transfert function

Φout_Total=(F1×ΦRef)+(F2×Φtune)+(F3×ΦVCO)

Hi again, AdvaRes,

if the various noise sources are uncorrelated, they have to be added quadratically:
(Φout_Total)^2=(F1×ΦRef)^2+(F2×Φtune)^2+(F3×ΦVCO)^2

If there should be any correlation between these noise sources (possible in a closed loop system), the total noise is less than that given above. Hence the quadratic addition of noise sources calculates the worst case value.

Salut, erikl