Although this work is mainly focused on discrete-time signals, a discussion of continuous-time signals cannot be avoided, for at least two reasons:
The objective is not an extensive display of the knowledge needed in the field of deterministic signal processing. Many other books have already done that quite well. We will merely give the main definitions and properties useful to further developments. We will also take the opportunity to mention systems in a somewhat restricted meaning, this word referring to what are called filters.
A deterministic continuous-time signal is defined as a function of the real time variable t:
The space made up of these functions is completed by the Dirac pulse distribution, or δ(t) function. Actually a distribution (a linear functional), this object can be handled just like a function without any particular problems in the exercises we will be dealing ...