Can somebody please tell me why the system $y[n] = x(2n)$ is non-causal ?

I know that causal systems depend on the past and present values of input and this system satisfies the condition. So why is the answer that the system is non-causal ?

Thank you.


1 Answer 1


No it does not satisfy the condition. Simply take an example:

$$n = 1 \implies y[1] = x[2]$$

Hence the output value at the present time $n=1$ depends on a future value of the input at time $n=2$. This violates the causality principle.


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