phase detector gain

Hello Everyone;
How I can determine the gain of phase detector in a PLL? For example, see the ADF4118 datasheet:
http://www.analog.com/UploadedFiles/..._4117_4118.pdf

from page 13 it is a PFD with the charge pump , the PEF gain is ICP/(2*pi)

checl razavi book chapter 8 , about this phase detector , also check the Ronlad best book

khouly

To measure the phase detector gain, you need to measure the phase shift between the VCO output waveform and the input waveform.