Signal: Definition

Section: Introduction

Definition

A signal is a physical representation which carry an “information” from a source to a destination.

Mathematically

  • An “analogical” signal is a continuous function of the time. $$ \begin{aligned} s : & \mathbb{R} \rightarrow \mathbb{R} \\ & t \mapsto s(t) \end{aligned} $$

  • A “numerical” signal is a discrete function (ie. a sequence) of the time. $$ \begin{aligned} s : & \mathbb{Z} \rightarrow \mathbb{R} \\ & k \mapsto s[t] = s_t \end{aligned} $$