Anti-causal filter

In signal processing, an anti-causal system is one whose output depends only on present and future inputs. An anti-causal system that is also linear and time-invariant is an anti-causal filter. By contrast, a filter whose output depends only on past and present inputs is called a causal filter.

An example of an anti-causal filter is a maximum phase filter, which can be defined as a stable, anti-causal filter whose inverse is also stable and anti-causal.