I have been looking into a Satellite tone ranging system. Phase error Performance criteria has been given as a function of $S/N_0=40 dB.Hz$ of the Major tone. The major tone is 100 kHz away from the main carrier and is PM Modulated with a modulation index of 1.1. I want to replicate the same conditions but don't know how to convert $S/N_0$ to $C/N$. Any help will be greatly appreciated.