7.09  coherence. Number calculated from the cross spectrum, ranging from 0 to 1 indicating to what degree the output of a system is linear, causal, and time invariant, with respect to the input.

Annotation 1      The coherence, γ2, is calculated as


where GAB is the cross spectrum, GAA is the input auto spectrum, and GBB is the output auto spectrum.

Annotation 2      Coherence also may be reduced by additive noise at the system input or output.

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