Based on the proposal of spectrum approach to quadratic phase coupling analysis

the comparison is made between this new method and the bispectrum method. The spectrum method has much ies calculation burden and is apt to achieve higher resolution ability as well as can be easily performed.Then the analysis of quadratic phase coupling is extended to complex domain

different and interesting results are obtained. At last spectrum method is developed to deal with another kind of nonlinear phase coupling

cubic phase coupling

fine results are obtained. Simulation examples are presented to prove the results of this paper.