Question

if a system produces frequency in the output that are not present in the input ,then the system cannot
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Answer 1

If a system produces frequency in the output that are not present in the input ,then the system cannot be LTI system.

Explanation:

Some points about LTI (Linear time-invariant) system are given below:

• LTI is a system that produces an output signal from any input signal subject to the constraints of linearity and time-invariance.

• Any LTI system can be characterized entirely by system's impulse response function.

• One feature of LTI system is that it cannot generate any new output which is not present in its input frequency. That means if input is x(t) and output is y(t) and if input is x(t - T) output is y(t-T), where t, T is  function of time.