Envelope correlations (4/5) Frequency correlation and time correlation allow a rigorous definition of coherence bandwidth and coherence time. Given a reference,residual frequency correlation "a",then coherence bandwidth is: B=币with R,(o)≤for w≥项 Similarly,given a reference,residual time correlation "a",then coherence time IS To=7 with R,()同sa fort≥i Coherence distance L.can also be defined in the following way: L9=I with R,(0)≤a forx≥lEnvelope correlations (4/5) Frequency correlation and time correlation allow a rigorous definition of coherence bandwidth and coherence time. Given a reference, residual frequency correlation “ a ”, then coherence bandwidth is: BC (a) = w with Rf (w) ≤ a for w ≥ w Similarly, given a reference, residual time correlation “ a ”, then coherence time is : TC (a) = t with R t(t ) ≤ a for t ≥ t Coherence distance Lc can also be defined in the following way: LC (a) = l with R x (l) ≤ a for x ≥ l