RESUMEN

One of the general methods in linear control theory is based on harmonic and non-harmonic Fourier series. The key of this approach is the estabilishment of the various suitable adaptations and generalizations of the classical Parseval equality. A new and systematic approach was begun in our papers [1]-[4] in collaboration with Baioccchi. Many recent results of this kind, obtained through various Ingham-type theorems, were exposed recently in [9]. Although this work concentrated on continous models, in connection with numerical simulations a natural question is whether these results also admit useful discrete versions. The purpose of this paper is to establish discrete versions of various Ingham-type theorems by usisng our approach. They imply the earlier continous results by a simple limit process.