# Online Electronics and Communication Engineering Test - Signals and Systems Test

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Instruction:

• This is a FREE online test. DO NOT pay money to anyone to attend this test.
• Total number of questions : 20.
• Time alloted : 30 minutes.
• Each question carry 1 mark, no negative marks.
• DO NOT refresh the page.
• All the best :-).

1.

Consider Pole zero diagram as shown, If two Poles are moved in opposite direction towards ω = p/2 and -p/2, the filter will be

A.
 change to high pass filter
B.
 change to Band Pass filter
C.
 remains same
D.
 change to LPF

Your Answer: Option (Not Answered)

Correct Answer: Option C

Explanation:

But still we will get the same response, zero are at same position.

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2.

The continuous time system with impulse response h(t) = is stable, for n is even, when

A.
 a = 0
B.
 a > 0
C.
 a < 0
D.
 a ≤ 0

Your Answer: Option (Not Answered)

Correct Answer: Option C

Explanation:

For stable system exponential must be -ve so that a < 0.

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3.

A function having frequency f is to be sampled. The sampling time T should be

A.
B.
C.
D.

Your Answer: Option (Not Answered)

Correct Answer: Option C

Explanation:

Sampling frequency must be more than 2f. Therefore .

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4.

Inverse Laplace transform of is

A.
 2 exp (- 2.5 t) cosh (0.5 t)
B.
 exp (- 2 t) + exp (- 3 t)
C.
 2 exp (- 2.5 t) sinh (0.5 t)
D.
 2 exp (- 2.5 t) cos 0.5 t

Your Answer: Option (Not Answered)

Correct Answer: Option B

Explanation:

f(t) = e-2t + e-3t.

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5.

Pick the odd one

A.
 variance
B.
 standard deviation
C.
 expectation
D.
 chebyshev inequality

Your Answer: Option (Not Answered)

Correct Answer: Option D

Explanation:

Because Variance, standard Deviation, Expectation are related to each other.

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6.

If the poles of H(z) are at

A.
B.
 z = 1 and z = 3
C.
D.
 z = -1 and z = -3

Your Answer: Option (Not Answered)

Correct Answer: Option A

Explanation:

.

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7.

A linear system is characterized by H(ω) = Be-2ω2 the system is physically

A.
 unrealizable
B.
 realizable
C.
 depends upon B
D.
 depends upon constant 2

Your Answer: Option (Not Answered)

Correct Answer: Option A

Explanation:

Exponential function cannot be linear.

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8.

ROC of sequence x[n] = (3)n ∪[n] + (4)n ∪[- n - 1]

A.
 |z| > 4
B.
 3 < |z| < 4
C.
 |z| < 4
D.
 |z| > 3

Your Answer: Option (Not Answered)

Correct Answer: Option B

Explanation:

x[n] = (3)n ∪(n) + (4)n ∪(- n - 1)

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9.

The eigen values of matrix are

A.
 1, 1
B.
 - 1, - 1
C.
 j, - j
D.
 1, - 1

Your Answer: Option (Not Answered)

Correct Answer: Option D

Explanation:

Eigen values of matrix A are roots of characteristic equation. [λ1- A] = 0 where λ is a scalar. Therefore

(λ + 1)(λ - 1) = 0. The roots are - 1 and + 1.

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10.

If f1(t)<< F1(jω) and f2(t)↔ F2(jω), then [a1 f1(t) + a2f2(t)]↔

A.
 a1F1(jω) + a2F2(jω)
B.
 a1a2F1(jω) + F2(jω)
C.
 a1F1(jω) - a2F2(jω)
D.
 a1F1*(jω) + a2F2*(jω)

Your Answer: Option (Not Answered)

Correct Answer: Option A

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11.

Consider the following sets of values of E, R and C for the circuit in the given figure.

1. 2 V, 1 Ω, 1.25 F
2. 1.6 V, 0.8 Ω, 1 F
3. 1.6 V, 1 Ω, 0.8 F
4. 2 V, 1.25 Ω, 1 F
Which of these of values will ensure that the state equation is valid?

A.
 1 and 4
B.
 1 and 2
C.
 3 and 4
D.
 2 and 3

Your Answer: Option (Not Answered)

Correct Answer: Option D

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12.

Assertion (A): The conditions under which it is possible to write Fourier series of a periodic function are called Drichlet conditions.

Reason (R): If f(t) = - f(- t), it is refereed to as odd symmetry.

A.
 Both A and R are correct and R is correct explanation of A
B.
 Both A and R are correct but R is not correct explanation of A
C.
 A is true, R is false
D.
 A is false, R is true

Your Answer: Option (Not Answered)

Correct Answer: Option B

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13.

Which one of the following rules determines the mapping of s-plane to z-plane?

A.
 Right half of the s-plane maps into outside of the unit circle in z-plane
B.
 Left half of the s-plane maps into outside of the unit circle.
C.
 Imaginary axis in s-plane maps in to the circumference of the unit circle.
D.
 All of the above

Your Answer: Option (Not Answered)

Correct Answer: Option D

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14.

Half wave sysmmetry means f(t) = - f(t ± T/2).

A.
 True
B.
 False

Your Answer: Option (Not Answered)

Correct Answer: Option A

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15.

The z-transform of sequence x[n] = δ(n) is

A.
 1
B.
 ∞
C.
 0
D.
 z

Your Answer: Option (Not Answered)

Correct Answer: Option A

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16.

If xk = 2k for k ≤ 0 and xk = 0 for k ≥ 0, Z transform of the sequence x is

A.
B.
C.
D.

Your Answer: Option (Not Answered)

Correct Answer: Option D

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17.

If f(t) is an odd function

A.
 True
B.
 False

Your Answer: Option (Not Answered)

Correct Answer: Option B

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18.

If xk = ak and k ≥ 0
X(z) = (1 - az-1)-1 with |a| < |z|

A.
 True
B.
 False

Your Answer: Option (Not Answered)

Correct Answer: Option B

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19.

The function sinc x is equal to

A.
B.
C.
D.

Your Answer: Option (Not Answered)

Correct Answer: Option A

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20.

The following table gives some time functions and the Laplace transforms

Of these correctly matched pairs are

A.
 2 and 4
B.
 1 and 4
C.
 3 and 4
D.
 1 and 2

Your Answer: Option (Not Answered)

Correct Answer: Option A

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