how to simulate the phase error of a quadrature oscillator?

Dose anybody know how to simulate the phase error of a quadrature oscillator?
I don't know how to get the phase errors between the four quadrature branches, e.g. by presenting a plot of the deviations.
thanks!

Are you referring to a specific simulation tool? Most tools have functions and expressions in the plot postprocessor that can easily present the intended display.

The simulation tool is ADS2009. Can you tell me which functions and expressions I should use?
Thanks!