DSP Basic Signaling MCQ Quiz – Objective Question with Answer for DSP Basic Signaling

1. Which of the following should be done in order to convert a continuous-time signal to a discrete-time signal?

A. Sampling
B. Differentiating
C. Integrating
D. None of the mentioned

Answer: A

The process of converting a continuous-time signal into a discrete-time signal by taking samples of the continuous-time signal at discrete time instants is known as ‘sampling’.

2. The process of converting discrete-time continuous valued signal into discrete-time discrete valued (digital) signal is known as ____________

A. Sampling
B. Quantization
C. Coding
D. None of the mentioned

Answer: B

In this process, the value of each signal sample is represented by a value selected from a finite set of possible values. Hence this process is known as ‘quantization’

3. The difference between the unquantized x(n) and quantized xq(n) is known as ___________

A. Quantization coefficient
B. Quantization ratio
C. Quantization factor
D. Quantization error

Answer: D

Quantization error is the difference in the signal obtained after sampling i.e., x(n), and the signal obtained after quantization i.e., xq(n) at any instant of time.

4. Which of the following is a digital-to-analog conversion process?

A. Staircase approximation
B. Linear interpolation
C. Quadratic interpolation
D. All of the mentioned

Answer: D

The process of joining in terms of steps is known as staircase approximation, connecting two samples by a straight line is known as Linear interpolation, connecting three samples by fitting a quadratic curve is called Quadratic interpolation.

5. The relation between analog frequency ‘F’ and digital frequency ‘f’ is?

A. F=f × T(where T is sampling period).
B. f=F × T
C. No relation
D. None of the mentioned

Answer: B

Consider an analog signal of frequency ‘F’, which when sampled periodically at a rate of Fs=1/T samples per second yields a frequency of f=F/Fs=>f=F × T.

6. What is the output signal when a signal x(t)=cos(2 × π × 40 × t) is sampled with a sampling frequency of 20Hz?

A. cos(π × n)
B. cos(2 × π × n)
C. cos(4 × π × n)
D. cos(8 × π × n)

Answer: C

From the question F=40Hz, Fs=20Hz
=>f=F/Fs
=>f=40/20
=>f=2Hz
=>x(n)=cos(4 × π × n).

7. If ‘F’ is the frequency of the analog signal, then what is the minimum sampling rate required to avoid aliasing?

A. F
B. 2F
C. 3F
D. 4F

Answer: A

According to the Nyquist rate, to avoid aliasing the sampling frequency should be equal to twice the analog frequency.

8. What is the Nyquist rate of the signal x(t)=3cos(50 × π × t)+10sin(300 × π × t)-cos(100 × π × t)?

A. 50Hz
B. 100Hz
C. 200Hz
D. 300Hz

Answer: D

The frequencies present in the given signal are F1=25Hz, F2=150Hz, F3=50Hz
Thus Fmax=150Hz and from the sampling theorem,
Nyquist rate=2 × Fmax
Therefore, Fs=2 × 150=300Hz.

9. What is the discrete-time signal obtained after sampling the analog signal x(t)=cos(2000 × π × t)+sin(5000 × π × t) at a sampling rate of 5000 samples/sec?

A. cos(2.5 × π × n)+sin(π × n)
B. cos(0.4 × π × n)+sin(π × n)
C. cos(2000 × π × n)+sin(5000 × π × n)
D. none of the mentioned

Answer: B

From the given analog signal, F1=1000Hz F2=2500Hz and Fs=5000Hz
=>f1=F1/Fs and f2=F2/Fs
=>f1=0.2 and f2=0.5
=>x(n)=cos(0.4 × π × n)+sin(π × n).

10. If the sampling rate Fs satisfies the sampling theorem, then the relation between quantization errors of the analog signal(eq(t)) and discrete-time signal(eq(n)) is?

A. eq(t)=eq(n)
B. eq(t)<eq(n)
C. eq(t)>eq(n)
D. not related

Answer: A

If it obeys the sampling theorem, then the only error in A/D conversion is the quantization error. So, the error is the same for both analog and discrete-time signals.</eq(n)

11. The quality of the output signal from the A/D converter is measured in terms of ___________

A. Quantization error
B. Quantization to signal noise ratio
C. Signal to quantization noise ratio
D. Conversion constant

Answer: C

The quality is measured by taking the ratio of noises of the input signal and the quantized signal i.e., SQNR, and is measured in terms of dB.

12. Which bit coder is required to code a signal with 16 levels?

A. 8 bit
B. 4 bit
C. 2 bit
D. 1 bit

Answer: B

To code a signal with L number of levels, we require a coder with (log L/log 2) number of bits. So, log16/log2=4 bit coder is required.

13. What is the period of a signal x(t)?

A. T
B. 2T
C. T/2
D. None of the mentioned

Answer: A

A signal is said to be periodic if the duration of one complete cycle is T and it repeats itself after this duration.

14. Which of the given signals are periodic?

A. x(t) = 4 cos(5πt)
B. x(t) = u(t) – 1/2
C. x(t) = 4u(t) + 2sin(3t)
D. x[n] = 2sin(3n)

Answer: A

T=2π / 5π = 2/5, periodic with period 2/5.

15. Check whether the signal is periodic or not?
x(t) = cos(4t) + 2sin(8t)

A. Periodic with period π/2
B. Periodic with period 2
C. Periodic with period 2/π
D. Not periodic

Answer: A

T1=2π /4

T2=2π /8

T1/T2 = 2 T

=T1 or 2T2

T=π /2.

The signal x(t) = cos(4t) + 2sin(8t) periodic with period π/2

16. Find the periodicity of the following signal. x(t)=cos((2π/7)t)sin((3π/5)t)

A. 30
B. 7
C. 35
D. 5/3

Answer: C

T1=2π/2π/7 = 7,

T2=2π/3π/5=5/3,

T1/T2=5/21,

T=21T1

5T2, T=35.

17. Find the fundamental period of 1+sin^2 (3π/5)n.

A. 10/3
B. 5
C. 3π/5
D. None of the mentioned

Answer: B

sin2(3π/5)n = (1-cos(6π/5)n)/2

= 1/2-1/2cos(6π/5)n

; period = 6π/(5 × 2π)

= k/N = 3/5 ; N=5.

18. Which signal is called an energy signal?

A. Finite energy and zero power
B. Finite energy and non-zero power
C. Infinite energy and zero power
D. Infinite energy and non-zero power

Answer: A

A signal is said to be an energy signal if it has finite energy and zero average power.

19. Which signal is said to be a power signal?

A. Infinite power and zero energy
B. Infinite power and non-zero energy
C. Finite power and infinite energy
D. Finite power and zero energy

Answer: C

A signal is said to be a power signal if it has finite power and infinite energy.

20. Determine the periodicity and also find whether it is a power or energy signal?
e(-at)u(t)

A. Periodic and energy signal
B. Non-periodic and energy signal
C. Periodic and power signal
D. Periodic and energy signal

Answer: B

This is non-periodic as it does not repeat itself after any period. And on calculating we will get energy as 1/2a which is finite. Thus it is an energy signal.

21. Continuous Impulse signal is a power or energy signal?

A. Power signal
B. Energy signal
C. Both power and energy
D. Neither power nor energy signal

Answer: D

On calculating using the power and energy calculation formula we will arrive at it is neither power nor energy signal.

22. Discrete impulse signal is a power or energy signal?

A. Power signal
B. Energy signal
C. Both power and energy signal
D. Neither power nor energy signal

Answer: B

On calculating using the energy formula we will get the energy of this signal as 1 which is a finite value. Thus it is an energy signal.

23. A unit impulse function has?

A. Large amplitude
B. Zero pulse width
C. Unity weight
D. All of the mentioned

Answer: D

An impulse function has an infinite or large-amplitude, zero pulse width, and unity weight which is concentrated at zero.

24. Which of the following is a common independent variable for speech signal, EEG, and ECG?

A. Time
B. Spatial coordinates
C. Pressure
D. None of the mentioned

Answer: A

Speech, EEG, and ECG signals are examples of information-bearing signals that evolve as functions of a single independent variable, namely, time.

25. Which of the following conditions made digital signal processing more advantageous over analog signal processing?

A. Flexibility
B. Accuracy
C. Storage
D. All of the mentioned

Answer: D

A digital programmable system allows flexibility in reconfiguring the DSP operations by just changing the program, as the digital signal is in the form of 1 and 0’s it is more accurate and it can be stored in magnetic tapes.

26. Which property does y(t)=x(1-t) exhibit?

A. Time scaling
B. Time shifting
C. Reflecting
D. Time shifting and reflecting

Answer: D

First the signal x(t) is shifted by 1 to get x(1+t) and it is reflected to get x(1-t). So, it exhibits both time-shifting and reflecting properties.

27. If x(n)=(0,1,2,3,3,0,0,0) then x(2n) is?

A. (0,2,4,6,6,0,0,0)
B. (0,1,2,3,3,0,0,0)
C. (0,2,3,0,0,0,0,0)
D. None of the mentioned

Answer: C

If x(n)=(0,1,2,3,3,0,0,0) then x(2n) is

Substitute n=0,1,2… in x(2n) and obtain the values from the given x(n).

28. If x(n)=(0,0,1,2,3,4,0,0) then x(n-2) is?

A. (0,0,2,4,6,8,0,0)
B. (0,0,1,2,3,4,0,0)
C. (1,2,3,4,0,0,0,0)
D. (0,0,0,0,1,2,3,4)

Answer: D

If x(n)=(0,0,1,2,3,4,0,0) then x(n-2) is

The signal x(n) is shifted right by 2.

29. If x(n)=(0,0,1,1,1,1,1,0) then x(3n+1) is?

A. (0,1,0,0,0,0,0,0)
B. (0,0,1,1,1,1,0,0)
C. (1,1,0,0,0,0,0,0)
D. None of the mentioned

Answer: A

If x(n)=(0,0,1,1,1,1,1,0) then x(3n+1) is

First, shift the given signal left by 1 and then time scale the obtained signal by 3.

30. If a signal x(t) is processed through a system to obtain the signal (x(t)2), then the system is said to be ____________

A. Linear
B. Non-linear
C. Exponential
D. None of the mentioned

Answer: B

Let the input signal be ‘t’. Then the output signal after passing through the system is y=t2 which is the equation of a parabola. So, the system is non-linear.

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