Editing Signal (section)

=== Periodic ===
A signal is said to be [[Periodic function|periodic]] if it satisfies the condition:

<math>x(t) = x(t + T)\quad \forall t \in [t_0 , t_{max}]</math> or <math>x(n) = x(n + N)\quad \forall n \in [n_0 , n_{max}]</math>

Where:

<math>T</math> = fundamental time [[Period (physics)|period]],

<math>1/T = f </math>= fundamental [[frequency]].

The same can be applied to <math>N</math>. A periodic signal will repeat for every period.

==== Time discretization{{anchor|Discretization}} ====
[[File:Sampled.signal.svg|right|thumb|Discrete-time signal created from a continuous signal by [[Sampling (signal processing)|sampling]]]]

Signals can be classified as [[Continuous signal|continuous]] or [[discrete time]].  In the mathematical abstraction, the domain of a continuous-time signal is the set of real numbers (or some interval thereof), whereas the domain of a discrete-time (DT) signal is the set of [[integer]]s (or other subsets of real numbers).  What these integers represent depends on the nature of the signal; most often it is time.

A continuous-time signal is any [[mathematical function|function]] which is defined at every time ''t'' in an interval, most commonly an infinite interval. A simple source for a discrete-time signal is the [[Sampling (signal processing)|sampling]] of a continuous signal, approximating the signal by a sequence of its values at particular time instants.