Consider the system as shown below
where, y(t)=x(et). The system is
Correct Answer :
linear and non-causal.
Solution :
The correct option is linear and non-causal.
Given the block diagram representing a system with input and output :
The input-output relationship of the system is given by:
To determine the characteristics of the system, we analyze both its linearity and its causality.
1. Linearity Test:
A system is linear if it satisfies the principle of superposition (homogeneity and additivity).
Let be the output corresponding to an input :
Let be the output corresponding to another input :
Now, let us apply a linear combination of the two inputs as the new input, , where and are constants.
The corresponding output is:
Substituting the expressions for and , we get:
Since the system satisfies the superposition principle, it is linear.
2. Causality Test:
A system is causal if the output at any time depends only on present and/or past values of the input. If the output depends on any future values of the input, the system is non-causal.
Let us evaluate the output at a few specific time instants:
For :
Here, the output at depends on the input at the future time .
For :
Here, the output at depends on the input at the future time .
Since the output depends on future values of the input (because for all real ), the system is non-causal.
Conclusion:
The system is both linear and non-causal.
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