Intuitive explanation of coherence

1. What is coherence analysis?
2. What is coherence of a signal?
3. How do you interpret a coherence plot?
4. What is the coherence of two signals?

What is coherence analysis?

Coherence analysis is a method developed on base of classic coherence analysis and signal's joint time-frequency representations in recent years. It was used to extract transient characteristics of interactions among brain areas. It describes the temporal, spatial and frequency relationships of brain activities.

What is coherence of a signal?

In signal processing, the coherence is a statistic that can be used to examine the relation between two signals or data sets. It is commonly used to estimate the power transfer between input and output of a linear system.

How do you interpret a coherence plot?

A coherence value near 1 indicates that the system is linear time-invariant at frequency f and confirms that the controller is capable of control at f. A coherence value near zero indicates that the system is non-linear, statistically changing with time, or both, signifying a low quality of control.

What is the coherence of two signals?

Coherence measures the degree of linear dependency of two signals by testing for similar frequency components. If two signals correspond to each other perfectly at a given frequency, the magnitude of coherence is 1.