Unlike a continuous-time signal, a discrete-time signal is not a function of a continuous argument; however, it may have been obtained by sampling from a continuous-time signal. When a discrete-time signal is obtained by sampling a sequence at uniformly spaced times, it has an associated sampling rate.
Discrete-time signals may have several origins, but can usually be classified into one of two groups:
- By acquiring values of an analog signal at constant or variable rate. This process is called sampling.
- By observing an inherently discrete-time process, such as the weekly peak value of a particular economic indicator.
- "Digital Signal Processing" Prentice Hall - Pages 11-12
- "Digital Signal Processing: Instant access." Butterworth-Heinemann - Page 8
- Gershenfeld, Neil A. (1999). The Nature of mathematical Modeling. Cambridge University Press. ISBN 0-521-57095-6.
- Wagner, Thomas Charles Gordon (1959). Analytical transients. Wiley.