The impulse response of the ideal delay system is ht delta

The impulse response of the ideal delay system is h(t) = delta (t -td). For what values of td will the delay system be causal?

Solution

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The delay system is said to be causal, if the output depends on present and past inputs only.

Therefore, the delay system h(t) is causal if and only if the values of t_d are positive.

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