Causality Condition of a Discrete-Time LTI System a discrete-time lti system is causal if and only if its impulse response hn is a causal sequence Example- The discrete-time system defined yn]=1x{]+x2x{n-1]+a3x[n-2]+4x[n-3] is a causal system as it has a causal impulse response {h4n]}={a1a234} 10 Copyright C 2001, S K MitraCopyright © 2001, S. K. Mitra 10 Causality Condition of a Discrete-Time LTI System • A discrete-time LTI system is causal if and only if its impulse response {h[n]} is a causal sequence • Example - The discrete-time system defined by is a causal system as it has a causal impulse response [ ] [ ] [ 1] [ 2] [ 3] y n = 1 x n +2 x n − +3 x n − +4 x n − { [ ]} { } h n = 1 2 3 4 