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Signals and Systems
Signals

Practice questions from Signals.

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Q#1 Signals GATE EE 2025 (Set 1) MCQ +1 mark -0.33 marks

Consider a continuous-time signal

 

where  is the continuous-time unit step function. Let  be the continuous time unit impulse function. The value of  is

-9

9

3

-3

Explanation:

 

 

 

 

                     

 

 

Hence, option (a) is correct.

Q#2 Signals GATE EE 2025 (Set 1) NAT +1 mark -0 marks

A continuous time periodic signal x(t)  is

 

If  is the period of , then  __________ (round off to the nearest integer).

Explanation:

 

This expression represents Power contained in the signal as per Parseval's Energy Theorem Since, the signal is in terms of a Fourier Series all the signals are orthogonal and hence their powers can be directly added.

 

 

 

 

Q#3 Signals GATE EE 2024 (Set 1) MCQ +2 marks -0.66 marks

The input  and the output  of a system are related as

 

nonlinear.

linear and time-invariant.

linear but not time-invariant.

noncausal.

Explanation:

The output of the system to two inputs are

Linearity:-

   

 hence linear

Time-variance

For  

Let

 

 to

 to

 

Now,

Q#4 Signals GATE EE 2024 (Set 1) MCQ +2 marks -0.66 marks

Consider the discrete-time systems  and  defined as follows:                                       

 

 

Which one of the following statements is true?

 and  are BIBO stable.

 and  are not BIBO stable.

 is BIBO stable but  is not BIBO stable.

 is not BIBO stable but  is BIBO stable.

Explanation:

For impulse response of this system we have to consider the input as Impulse Signal.

 

Since the impulse response is not absolutely summable the system is Unstable.

Assume x[n] is bounded that is

For

 

The above signal is bounded for all values of n and hence for a bounded input we are getting bounded output so the system is BIBO Stable.

Q#5 Signals GATE EE 2024 (Set 1) NAT +2 marks -0 marks

If the energy of a continuous-time signal  is  and the energy of the signal  is , then  is ________ (rounded off to 1 decimal place).

Explanation:

Energy of a signal is not affected by time shifting

Energy of a signal changes due to time scaling

After amplitude scaling the energy becomes

Q#6 Signals GATE EE 2023 (Set 1) NAT +2 marks -0 marks

The period of the discrete-time signal  described by the equation below is  __________ (Round off to the nearest integer).

Explanation:

Period of

Period of

= rational ∴ overall signal is periodic

N = LCM (N1, N2) = LCM (16, 6) = 48