Editing System analysis (section)

== LTI systems ==
{{main|Linear time-invariant system}}
As mentioned above, there are many methods of analysis developed specifically for [[LTI system theory|Linear time-invariant systems]] (LTI systems).  This is due to their simplicity of specification.  An [[LTI system theory|LTI system]] is completely specified by its [[transfer function]] (which is a [[rational function]] for digital and lumped analog LTI systems).  Alternatively, we can think of an LTI system being completely specified by its [[frequency response]].  A third way to specify an LTI system is by its characteristic [[linear differential equation]] (for analog systems) or linear [[difference equation]] (for digital systems).  Which description is most useful depends on the application.

The distinction between [[Lumped-element model|lumped]] and [[Distributed-element model|distributed]] LTI systems is important.  A lumped LTI system is specified by a finite number of parameters, be it the [[zeros and poles]] of its transfer function, or the [[coefficient]]s of its differential equation, whereas specification of a distributed LTI system requires a complete [[Function (mathematics)|function]], or partial differential equations.