Quadratic time-varying spectral estimation for underspread processes

We study time-varying spectral estimation for nonstationary processes with restricted time-frequency (TF) correlation. We present explicit bias and variance expressions for quadratic TF-invariant (QTFI) estimators of an expected real-valued QTFI representation based on a single noisy observation. Unbiased theoretical estimators with globally minimal variance are derived and approximately realized by a matched multiwindow method.<
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