# Signals & Systems Expected MCQ PDF 1 For Coal India Limited (CIL) MT Exam 2017

1)   Which mathematical notation specifies the condition of periodicity for a continuous time signal?

a. x(t) = x(t +T0)
b. x(n) = x(n+ N)
c. x(t) = e-αt
d. None of the above

2)   Which
property of delta function indicates the equality between the area under
the product of function with shifted impulse and the value of function
located at unit impulse instant?

a. Replication
b. Sampling
c. Scaling
d. Product

3)   Which among
the below specified conditions/cases of discrete time in terms of real
constant ‘a’, represents the double-sided decaying exponential signal?

a. a > 1
b. 0 < a < 1
c. a < -1
d. -1 < a < 0

 ANSWER: -1 < a < 0

4)   Damped sinusoids are _____

a. sinusoid signals multiplied by growing exponentials
b. sinusoid signals divided by growing exponentials
c. sinusoid signals multiplied by decaying exponentials
d. sinusoid signals divided by decaying exponentials

 ANSWER: sinusoid signals multiplied by decaying exponentials

5)   An amplitude
of sinc function that passes through zero at multiple values of an
independent variable ‘x’ ______

a. Decreases with an increase in the magnitude of an independent variable (x)
b. Increases with an increase in the magnitude of an independent variable (x)
c. Always remains constant irrespective of variation in magnitude of ‘x’
d. Cannot be defined

 ANSWER: Decreases with an increase in the magnitude of an independent variable (x)

6)   A system is said to be shift invariant only if______

a. a shift in the input signal also results in the corresponding shift in the output
b. a shift in the input signal does not exhibit the corresponding shift in the output
c. a shifting level does not vary in an input as well as output
d. a shifting at input does not affect the output

 ANSWER: a shift in the input signal also results in the corresponding shift in the output

7)   Which condition determines the causality of the LTI system in terms of its impulse response?

a. Only if the value of an impulse response is zero for all negative values of time
b. Only if the value of an impulse response is unity for all negative values of time
c. Only if the value of an impulse response is infinity for all negative values of time
d. Only if the value of an impulse response is negative for all negative values of time

 ANSWER: Only if the value of an impulse response is zero for all negative values of time

8)   Under which conditions does an initially relaxed system become unstable?

a. only if bounded input generates unbounded output
b. only if bounded input generates bounded output
c. only if unbounded input generates unbounded output
d. only if unbounded input generates bounded output

 ANSWER: only if bounded input generates unbounded output

9)   Which among the following are the stable discrete time systems?
1. y(n) = x(4n)
2. y(n) = x(-n)
3. y(n) = ax(n) + 8
4. y(n) = cos x(n)

a. 1 & 3
b. 2 & 4
c. 1, 3 & 4
d. 1, 2, 3 & 4

 ANSWER: 1, 2, 3 & 4

10)   An equalizer
used to compensate the distortion in the communication system by
faithful recovery of an original signal is nothing but an illustration
of _________

a. Static system
b. Dynamic system
c. Invertible system
d. None of the above

11)   Which block of the discrete time systems requires memory in order to store the previous input?

b. Signal Multiplier
c. Unit Delay

12)   Which type/s of discrete-time system do/does not exhibit the necessity of any feedback?

a. Recursive Systems
b. Non-recursive Systems
c. Both a & b
d. None of the above

13)   Which among the following belongs to the category of non-recursive systems?

a. Causal FIR Systems
b. Non-causal FIR Systems
c. Causal IIR Systems
d. Non-causal IIR Systems

14)   Recursive Systems are basically characterized by the dependency of its output on _______

a. Present input
b. Past input
c. Previous outputs
d. All of the above

15)   What does
the term y(-1) indicate especially in an equation that represents the
behaviour of the causal system?

a. initial condition of the system
b. negative initial condition of the system
c. negative feedback condition of the system
d. response of the system to its initial input

 ANSWER: initial condition of the system

16)   Which type of system response to its input represents the zero value of its initial condition?

a. Zero state response
b. Zero input response
c. Total response
d. Natural response

17)   Which is/are the essential condition/s to get satisfied for a recursive system to be linear?

a. Zero state response should be linear
b. Principle of Superposition should be applicable to zero input response
c. Total Response of the system should be addition of zero state & zero input responses
d. All of the above

18)   Which among
the following operations is/are not involved /associated with the
computation process of linear convolution?

a. Folding Operation
b. Shifting Operation
c. Multiplication Operation
d. Integration Operation

19)   A LTI system is said to be initially relaxed system only if ____

a. Zero input produces zero output
b. Zero input produces non-zero output
c. Zero input produces an output equal to unity
d. None of the above

 ANSWER: Zero input produces zero output

20)   What are the number of samples present in an impulse response called as?

a. string
b. array
c. length
d. element

21)   Which are the only waves that correspond/ support the measurement of phase angle in the line spectra?

a. Sine waves
b. Cosine waves
c. Triangular waves
d. Square waves

22)   Double-sided phase & amplitude spectra _____

a. Possess an odd & even symmetry respectively
b. Possess an even & odd symmetry respectively
c. Both possess an odd symmetry
d. Both possess an even symmetry

 ANSWER: Possess an odd & even symmetry respectively

23)   What does the first term ‘a0’ in the below stated expression of a line spectrum indicate?
x(t) = a0 + a1 cos w0 t + a2 cos2 w0t +……+ b1 sin w0 t + b2 sin w0 t + …..

a. DC component
b. Fundamental component
c. Second harmonic component
d. All of the above

24)   Which kind
of frequency spectrum/spectra is/are obtained from the line spectrum of a
continuous signal on the basis of Polar Fourier Series Method?

a. Continuous in nature
b. Discrete in nature
c. Sampled in nature
d. All of the above

25)   Which type/s
of Fourier Series allow/s to represent the negative frequencies by
plotting the double-sided spectrum for the analysis of periodic signals?

a. Trigonometric Fourier Series
b. Polar Fourier Series
c. Exponential Fourier Series
d. All of the above

26)   What does the signalling rate in the digital communication system imply?

a. Number of digital pulses transmitted per second
b. Number of digital pulses transmitted per minute
c. Number of digital pulses received per second
d. Number of digital pulses received per minute

 ANSWER: Number of digital pulses transmitted per second

27)   As the signalling rate increases, _______

a. Width of each pulse increases
b. Width of each pulse decreases
c. Width of each pulse remains unaffected
d. None of the above

 ANSWER: Width of each pulse decreases

28)   Which
phenomenon occurs due to an increase in the channel bandwidth during the
transmission of narrow pulses in order to avoid any intervention of
signal distortion?

a. Compression in time domain
b. Expansion in time domain
c. Compression in frequency domain
d. Expansion in frequency domain

29)   Why are the
negative & positive phase shifts introduced for positive &
negative frequencies respectively in amplitude and phase spectra?

a. To change the symmetry of the phase spectrum
b. To maintain the symmetry of the phase spectrum
c. Both a & b
d. None of the above

 ANSWER: To maintain the symmetry of the phase spectrum

30)   Duality Theorem / Property of Fourier Transform states that _________

a. Shape of signal in time domain & shape of spectrum can be interchangeable
b. Shape of signal in frequency domain & shape of spectrum can be interchangeable
c. Shape of signal in time domain & shape of spectrum can never be interchangeable
d. Shape of signal in time domain & shape of spectrum can never be interchangeable

 ANSWER: Shape of signal in time domain & shape of spectrum can be interchangeable

31)   Which property of fourier transform gives rise to an additional phase shift of -2π ftd for the generated time delay in the communication system without affecting an amplitude spectrum?

a. Time Scaling
b. Linearity
c. Time Shifting
d. Duality

32)   Which among the below assertions is precise in accordance to the effect of time scaling?
A : Inverse relationship exists between the time and frequency domain representation of signal
B : A signal must be necessarily limited in time as well as frequency domains

a. A is true & B is false
b. A is false & B is true
c. Both A & B are true
d. Both A & B are false

 ANSWER: A is true & B is false

33)   Which is/are
the mandatory condition/s to get satisfied by the transfer function for
the purpose of distortionless transmission?

a. Amplitude Response should be constant for all frequencies
b. Phase should be linear with frequency passing through zero
c. Both a & b
d. None of the above

34)   What is/are
the crucial purposes of using the Fourier Transform while analyzing any
elementary signals at different frequencies?

a. Transformation from time domain to frequency domain
b. Plotting of amplitude & phase spectrum
c. Both a & b
d. None of the above

35)   What is the possible range of frequency spectrum for discrete time fourier series (DTFS)?

a. 0 to 2π
b. -π to +π
c. Both a & b
d. None of the above

36)   Which among
the following assertions represents a necessary condition for the
existence of Fourier Transform of discrete time signal (DTFT)?

a. Discrete Time Signal should be absolutely summable
b. Discrete Time Signal should be absolutely multipliable
c. Discrete Time Signal should be absolutely integrable
d. Discrete Time Signal should be absolutely differentiable

 ANSWER: Discrete Time Signal should be absolutely summable

37)   What is the nature of Fourier representation of a discrete & aperiodic signal?

a. Continuous & periodic
b. Discrete & aperiodic
c. Continuous & aperiodic
d. Discrete & periodic

38)   Which property of periodic signal in DTFS gets completely clarified / identified by the equation x (n – n0)?

a. Conjugation
b. Time Shifting
c. Frequency Shifting
d. Time Reversal

39)   A Laplace Transform exists when ______
A. The function is piece-wise continuous
B. The function is of exponential order
C. The function is piecewise discrete
D. The function is of differential order

a. A & B
b. C & D
c. A & D
d. B & C

40)   Where is the ROC defined or specified for the signals containing causal as well as anti-causal terms?

a. Greater than the largest pole
b. Less than the smallest pole
c. Between two poles
d. Cannot be defined

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