Signals and Systems
In Laplace transform, multiplication by e-at in time domain becomes
Answer: A
£e-at f(t) = F(s + a).
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ROC of sequence x[n] = (3)n ∪[n] + (4)n ∪[- n - 1]
Answer: B
No Explanation.
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The property is not valid for basic singularity function is
Answer: D
Singularity function is discontinuous at origin like ∪(t), δ(t).
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A voltage V(t) is a Gaussian ergodic random process with a mean of zero and a variance of 4 volt2. If it is measured by a dc meter. The reading will be
Answer:
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In an ac circuit the fundamental component of current wave lags the corresponding voltage wave by 20°. The third harmonic component of current wave lags the corresponding voltage by an angle.
Answer: B
No explanation.
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Which one is a causal system?
Answer: A
For causal output must depend upon Present and past not on future.
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Which one is time invariant system?
Answer: B
For time invariant system
y(n, k) = y(n - k), where y(n, k) mean shift the input by n - k, while y(n - k) mean change all the n
(a) y[n] = x[2n]
⇒ y(n, k) = x[2n - k]
y(n - k) = x[2(n - k)]
y(n, k) ≠ y(n - k) Time variant
(b) y[n] = x[n] x[n - 1]
y[n, k] = x[n - k] x[n - k - 1]
y[n - k] = x[n - k] x[n - k - 1]
y[n, k] = x[n - k] Time Invariant
(c) y[n] = x[n/2] ⇒ y[n, k] 
⇒ y[n - k] 
y[n, k] ≠ y[n - k] Time variant.
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δ(t) is a
Answer: B
Because Unit step is a Power signal. So By trignometric identifies d(t) also power.
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The ROC of sequence in the Z.T. of sequence x[n] = an ∪ [n] is
Answer: C
The simplest method to find the ROC. Put denominator to greater than zero.
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The signal defined by the equations f(t) = 0 for t < 0>f(t) = E for 0 ≤ t ≤ a and f(t) = 0 for t > a is
Answer: B
It is a pulse lasting for t = a.
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