Nonparametric identification of continuous linear systems with discrete measurements

Formulas for the pseudoinverse of a compact operator are applied to linear system identification and scattering function estimation from a finite set of noisy measurements. The result is a nonparametric estimator possessing several desirable features. The approach encompasses the Modified Discrete Fourier Transform and is applied herein to the important problem of closely spaced object resolsution in radar/optical signal processing.