Causality Condition of a Discrete-Time LTI System Note: a noncausal lti discrete-time system with a finite-length impulse response can often be realized as a causal system by nserting an appropriate amount of delay Example-a causal version of the factor-of- 2 interpolator is obtained by delaying the input by one sample period y小]=xln-1+(xlmn-21+x小) Copyright C 2001, S.K. MitraCopyright © 2001, S. K. Mitra 13 Causality Condition of a Discrete-Time LTI System • Note: A noncausal LTI discrete-time system with a finite-length impulse response can often be realized as a causal system by inserting an appropriate amount of delay • Example - A causal version of the factor-of- 2 interpolator is obtained by delaying the input by one sample period: [ ] [ 1] ( [ 2] [ ]) 2 1 y n = xu n − + xu n − + xu n