# Discrete-Time Fourier Transform MCQ’s

This set of Signals & Systems Multiple Choice Questions & Answers (MCQs) focuses on “Discrete-Time Fourier Transform”.

1. The time system which operates with a continuous time signal and produces a continuous time output signal is _________
a) CTF system
b) DTF System
c) Time invariant System
d) Time variant System

2. A discrete time signal is given as X [n] = cos πn9 + sin (πn7+12). The period of the signal X [n] is ______________
a) 126
b) 32
c) 252
d) Non-periodic

3. Given a discrete time signal x[k] defined by x[k] = 1, for -2≤k≤2 and 0, for |k|>2. Then, y[k] = x[3k-2] is ______________
a) y[k] = 1, for k = 0, 1 and 0 otherwise
b) y[k] = 1, for k = 1 and -1 for k=-1
c) y[k] = 1, for k = 0, 1 and -1 otherwise
d) y[k] = 1, for k = 0, 1 and 0 otherwise

4. What is the steady state value of The DT signal F (t), if it is known that F(s) = 1(s+2)2(s+4)?
a) 116
b) Cannot be determined
c) 0
d) 18

5. A discrete time signal is as given below
X [n] = cos (n8) cos (πn8)
The period of the signal X [n] is _____________
a) 16 π
b) 16(π+1)
c) 8
d) Non-periodic

6. The system described by the difference equation y(n) – 2y(n-1) + y(n-2) = X(n) – X(n-1) has y(n) = 0 and n<0. If x (n) = δ(n), then y (z) will be?
a) 2
b) 1
c) 0
d) -1

7. F(t) and G(t) are the one-sided z-transforms of discrete time functions f(nt) and g(nt), the z-transform of ∑f(kt)g(nt-kt) is given by _____________
a) ∑f(nt)g(nt)z-n
b) ∑f(nt)g(nt)zn
c) ∑f(kt)g(nt-kt) z-n
d) ∑f(nt-kt)g(nt)z-n

8. A Discrete signal is said to be even or symmetric if X(-n) is equal to __________
a) X(n)
b) 0
c) –X(n)
d) –X(-n)

9. A discrete time signal is as given below
X [n] = cos (πn2) – sin (πn8) + 3 cos (πn4+π3) The period of the signal X [n] is _____________
a) 16
b) 4
c) 2
d) Non-periodic

10. The Nyquist frequency for the signal x (t) = 3 cos 50πt + 10 sin 300πt – cos 100t is ___________
a) 50 Hz
b) 100 Hz
c) 200 Hz
d) 300 Hz 5 Star
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