All

we all know that charge pumps used in PLLs has a certain level of nonlinear characteristic: injected charge vs. input phase signal difference is not pefectly linear.
This non-linear behaviour impacts on mainly on PLL spurs, in particular in sigma-delta architecture.

I want to measure it in a lab (only PFD-CHP, not the whole PLL).

My basic idea is to (if inputs to PFD are available) inject two signals, with a very controlled phase shift (phase accuracy<<1deg) and measure the average current at charge pump output to calculate the injected charge.

Does anybody have hint, schematics, block diagram on lab characterization techniques of charge-pump non-linearity?
Does anybody have experience on that? Any other measurement technique?
How to generate and control this phase shifted signals with references in the 10-40MHz range?

Thank you in advance
Mazz