When to measure the incidental PM at AM

because in time domain and frequency domain

AM and PM are accompanied but not independent

so it's difficult to measure incidental PM.Traditional method by spectrum analysis is complex

and is only applicable to situation with small PM index.A new method is proposed:Under a particular frequency Relationship

by digital vector demodulation and sampling

to transform the AM and PM to magnitude error and phase error in IQ domain independently

on the measurement rules

there is analytical relationship between digital demodulation phase error and the analog incidental PM.For a total of 120 cases of parameters combination

experiment is carried out;the measurement results confirmed that the method is accurate.