Amplitude Modulated Coherence Analysis of Biomedical Signals

We describe a generalization of traditional coherence that estimates the relationship between frequency components of one or two signals at different frequencies. The key idea of this technique is to apply amplitude modulation to one of the signals prior to a traditional coherence analysis. The modulated coherence includes traditional coherence as a special case. This is useful for identifying nonlinear relationships in stochastic signals that cannot be determined by traditional analysis methods based on second-order statistics. We demonstrate the usefulness of modulated coherence on synthetic signals, an electrocardiogram, and a tremor recording.