Generalised framework for nonparametric coherence function estimation

By introducing a nonlinear function of covariance matrix, a generalised framework for the nonparametric coherence function (NPCF) estimation is presented. This framework helps us understand the properties of several existing NPCF estimators more easily, including the single- and multi-window based approaches. Moreover, by properly choosing the parameters of the generalised class of NPCF estimators, a good tradeoff between spectral resolution and variance can be achieved.