# Convolution

This set of MATLAB Multiple Choice Questions & Answers (MCQs) focuses on “Convolution”.

1. The unit step response of an L.T.I. system is the convolution of a step signal and it’s ________
a) Impulse response
b) Ramp response
c) Parabolic response
d) Time response

2. What is the output of the following code?

`conv([1 2],[3 4])`

a) [3 10 8]
b) [8 10 3]
c) [3 8]
d) [4 6]

3. What is the working of the conv2() command?
a) 2-d convolution
b) 1-d convolution
c) 3-d convolution
d) n-d convolution

4. What is the output of the following code?

`conv([1;3],[1;3])`

a) A column vector of 1 6 9
b) A row vector of 9 6 1
c) A row vector of 1 6 9
d) A column vector of 9 6 1

5. What is the output of the following code?

`conv(3,9)`

a) 27
b) 3
c) 9
d) Error

6. What is the output of the following code?

`conv[1 2]`

a) Error in input
b) Error in []
c) 2
d) 0

7. What is the output of the following code?

```>>p=conv([ones(1,100)],[ones(1,100)]);
>>x=[1:1:199];
>> plot(x,p)```

a) A triangular pulse
b) A step pulse
c) A sinusoid
d) Error

8. What is the length of the output?

`p=conv([ones(1,150)],[ones(1,150)]);`

a) 299
b) 298
c) 300
d) Error

9. What is the dimension of the output?

`conv([1;2],[1;2])`

a) 1*3
b) 1*4
c) 1*2
d) 2*2

10. What is the output of the following code?

`conv([1],[2;3])`

a) A column vector of 2 and 3
b) A column vector of 3 and 2
c) A row vector of 3 and 2
d) A row vector of 2 and 3

11. What is the output of the following code?

`conv({1 2},{3 4})`

a) Error
b) 6 8
c) 3 8
d) 3 10 8

12. What is the shape output of the following code?

`p=conv([ones(1,100)],[ones(1,50)])`

a) A trapezoid
b) A rectangular pulse
c) A triangular pulse
d) Error

13. What is the peak value of the output graph from the following code?

```>>q=conv([1 2],[2 1]);
>> plot([0 1 2],q)```

a) 5
b) 4
c) 1
d) Error

14. The output of p=conv([ones(1,50)],[ones(1,100)]) and p=conv([ones(1,100)],[ones(1,50)]) are same.
a) True
b) False

15. The signal get shifted by 1 units in time due to the following code: conv([ 1 2 3],[ 0 1 0 ]).
a) True
b) False

16. After what instant in time will the signal output become zero?

`p=conv([ones(1,100)],[ones(1,50),zeros(1,50)]);`

a) 150
b) 149
c) 151
d) Error

17. For a causal L.T.I. system, the impulse response is 0 for _________
a) t<0
b) t=0
c) t>0
d) Always

18. The convolution of a discrete signal with itself is _________
a) Squaring the signal
b) Doubling the signal
d) is not possible

19. The convolution of a function with an impulse function delayed to an instant 3 in time results in ____________
a) An advance in the function by 3 units in time
b) The function itself
c) A delay in the function by 3 units in time
d) Cannot be determined

20. What is the output of the following code?

```a=con([1 2],[1 2]);
b=cconv([1 2],[1 2]);```

a) a=b
b) a<b
c) a>b
d) a!=b

21. A continuous signal can be represented as the product of an impulse function and the signal itself.
a) True
b) False

22. What is the output of the following code?

`cconv([1 2],[0 1 0])`

a) [0 1 2 0]
b) [1 2 0 0]
c) [1 2 0 0]
d) [0 0 1 2]

23. What is the Scope value if the signal generator has a frequency of 2 Hz only?

a) An attenuated signal of same frequency
b) The entire signal at the same frequency
c) The entire signal at reduced frequency
d) An attenuated signal at reduced frequency

24. What is the output of the following code?

```P=tf([1 2],[3 4]);
Q=tf([1 2],[3 4]);
Z=P.Q;```

a) Z is the response of the system whose pole is at s=-4/3
b) Z is the response of the system whose pole is at s=4/3
c) Z is the response of the system whose poles are at s=-4/3 & s=+4/3
d) Z is the response of the system whose zeros are at s=-4/3

25. What is the inverse laplace transform of Z from the following?

```P=tf([1],[1 0 0]);
Q=tf([1],[1 0]);
Z=P.Q;```

a) t2
b) t2/2
c) t3
d) Error

26. What is the output of the following code?

```P=tf([1 2],[3 4]);
Q=tf([1 2],[3 4]);
Z=P.Q;
ilpalace(Z)```

a) Error
b) t
c) t2
d) Cannot be determined

27. What is the output of the following code?

`conv[1 2]`

a) Error in input
b) Error in []
c) 2
d) 0