SIGNAL AND SYSTEM 50 MOST IMPORTANT EXPECTED MCQ WITH SOLUTION FOR VIZAG MT AND BEL PE EXAM 2017

” ( 1 ) Unilateral Laplace Transform is applicable for the determination of
linear constant coefficient differential equations with ________
” 1) Zero
initial condition
” 2) Non-zero initial condition
” 3) Zero final
condition
” 4) Non-zero final condition
” 5) None of these
Answer :
2) Non-zero initial condition
Solution : Unilateral Laplace Transform is
applicable for the determination of linear constant coefficient differential
equations with Non-zero initial condition
” ( 2 ) Two rectangular waveforms
of duration t1 and t2 seconds are convolved. What is the shape of the resulting
waveform?
” 1) Triangular
” 2) Trapezoidal
” 3) Rectangular
” 4)
Semi-circular
” 5) circular
Answer : 2) Trapezoidal
Solution : If two
rectangular waveforms of duration t1 and t2 seconds are convolved. then the
shape of the resulting waveform is Trapezoidal.
” ( 3 ) What is the nature of
Fourier representation of a discrete & aperiodic signal?
” 1) Continuous
& periodic
” 2) Discrete and aperiodic
” 3) Continuous &
aperiodic
” 4) Discrete & periodic
” 5) None of these
Answer : 1)
Continuous & periodic
Solution : Fourier representation of a discrete
& aperiodic signal is Continuous & periodic.
” ( 4 ) Which property
of periodic signal in DTFS gets completely clarified / identified by the
equation x (n – n0 )?
” 1) Conjugation
” 2) Time Reversal
” 3)
Frequency Shifting
” 4) Time Shifting
” 5) None of these
Answer : 4)
Time Shifting
Solution : Time Shifting property of periodic signal in DTFS
gets completely clarified by the equation x (n – n0 ).
” ( 5) Duality Theorem
/ Property of Fourier Transform states that _________
” 1) Shape of signal in
time domain & shape of spectrum can be interchangeable
” 2) Shape of
signal in frequency domain & shape of spectrum can be interchangeable

3) Shape of signal in time domain & shape of spectrum can never be
interchangeable
” 4) Shape of signal in time domain & shape of spectrum
can never be interchangeable
” 5) None of these
Answer : 1) Shape of
signal in time domain & shape of spectrum can be interchangeable

Solution : Duality Theorem / Property of Fourier Transform states that Shape
of signal in time domain & shape of spectrum can be interchangeable.

( 6 ) Which property of fourier transform gives rise to an additional phase
shift of -2? ftd for the generated time delay in the communication system
without affecting an amplitude spectrum ?
” 1) Time Scaling
” 2)
Linearity
” 3) Time Shifting
” 4) Duality
” 5) None of
these
Answer : 3) Time Shifting
Solution : Time Shifting property of
fourier transform gives rise to an additional phase shift of -2? ftd for the
generated time delay in the communication system without affecting an amplitude
spectrum
” ( 7 ) Which among the following operations is/are not involved
/associated with the computation process of linear convolution?
” 1) Folding
Operation
” 2) Shifting Operation
” 3) Multiplication Operation
” 4)
Integration Operation
” 5) None of these
Answer : 4) Integration
Operation
Solution : Integration Operation is not associated with the
computation process of linear convolution.
” ( 8 ) Which type of system
response to its input represents the zero value of its initial condition?

1) Zero state response
” 2) Zero input response
” 3) Total response

” 4) Natural response
” 5) None of these
Answer : 1) Zero state
response
Solution : The zero state response (ZSR), also known as the forced
response is the behavior or response of a circuit with initial state of zero.
The ZSR results only from the external inputs or driving functions of the
circuit and not from the initial state. The ZSR is also called the forced or
driven response of the circuit.
” ( 9 ) Which among the following belongs to
the category of non-recursive systems?
” 1) Non-causal IIR Systems
” 2)
Causal IIR Systems
” 3) Non-causal FIR Systems
” 4) Causal FIR Systems

” 5) None of these
Answer : 4) Causal FIR Systems
Solution : Causal
FIR Systems is non-recursive systems.
” ( 10 ) Damped sinusoids are
_____
” 1) sinusoid signals multiplied by growing exponentials
” 2)
sinusoid signals divided by growing exponentials
” 3) sinusoid signals
multiplied by decaying exponentials
” 4) sinusoid signals divided by
decaying exponentials
” 5) None of these
Answer : 3) sinusoid signals
multiplied by decaying exponentials
Solution : Damped sinusoids are sinusoid
signals multiplied by decaying exponentials
” ( 11 ) Under which conditions
does an initially relaxed system become unstable ?
” 1) only if bounded input
generates unbounded output
” 2) only if bounded input generates bounded
output
” 3) only if unbounded input generates unbounded output
” 4) only
if unbounded input generates bounded output
” 5) None of these
Answer :
1) only if bounded input generates unbounded output
Solution : only if
bounded input generates unbounded output
” ( 12) All causal systems must have
the component of
” 1) memory
” 2) time invariance
” 3) stability

” 4) linearity
” 5) None of these
Answer : 1) memory
Solution :
All causal systems must have the component of memory
” ( 13 ) A system is
said to be defined as non causal, when
” 1) the output at the present depends
on the input at an earlier time
” 2) the output at the present does not
depend on the factor of time at all
” 3) the output at the present depends
on the input at the current time
” 4) the output at the present depends on
the input at a time instant in the future
” 5) None of these
Answer : 4)
the output at the present depends on the input at a time instant in the future

Solution : A non causal system’s output is said to depend on the input at a
time in the future.
” ( 314) A time invariant system is a system whose
output
” 1) vanishes with a delay in input
” 2) remains same with a delay
in input
” 3) decreases with a delay in input
” 4) increases with a
delay in input
Answer : 2) remains same with a delay in input
Solution :
A time invariant system’s output should be directly related to the time of the
output. There should be no scaling, i.e. y(t) = f(x(t)).
” ( 15) A system
which is linear is said to obey the rules of
” 1) homogeneity
” 2)
scaling
” 3) additivity
” 4) both scaling and additivity
” 5) None
of these
Answer : 4) both scaling and additivity
Solution : A system is
said to be additive and scalable in order to be classified as a linear
system.
” ( 16 ) Double integration of a unit step function would lead
to
” 1) an impulse
” 2) a parabola
” 3) a ramp
” 4) a doublet

” 5) None of these
Answer : 2) a parabola
Solution : Double
integration of a unit step function would lead to a parabola.
” ( 17 ) A
signal g(t) = A then g(t) is a
” 1) energy signal
” 2) power signal

3) neither energy nor power signal
” 4) insufficient data
” 5) both 1
& 2
Answer : 2) power signal
Solution : A signal g(t) = A then g(t)
is a power signal.
” ( 18 ) The Fourier series of an odd periodic function
contains
” 1) odd harmonics only
” 2) even harmonics only
” 3) cosine
harmonics only
” 4) sine harmonics only
” 5) None of these
Answer :
4) sine harmonics only
Solution : The Fourier series of an odd periodic
function contains sine harmonics only
” ( 19 ) As per time displacement
theorem in Laplace transformation, displacement in the time domain by T
becomes
” 1) division by s in the s domain
” 2) division by e-sT in the s
domain
” 3) multiplication by s in the s domain
” 4) multiplication by
e-sT in the s domain
” 5) None of these
Answer : 4) multiplication by
e-sT in the s domain
Solution : £f(t – T) = e-st F(s).
” ( 20 ) The
signal defined by the equations f(t) = 0 for t < 0, f(t) = E for 0 ? t ? a
and f(t) = 0 for t > a is
” 1) a step function
” 2) a pulse function

” 3) a shifted step function originating at t = a
” 4) unit step
function
” 5) None of these
Answer : 2) a pulse function
Solution :
The signal defined by the equations f(t) = 0 for t < 0, f(t) = E for 0 ? t ?
a and f(t) = 0 for t > a is a pulse function
” ( 21 ) Which one of the
following is correct? Energy of a power signal is
” 1) finite
” 2) zero

” 3) infinite
” 4) between 1 and 2
” 5) None of these
Answer : 3)
infinite
Solution : Energy of a power signal is infinite
” ( 22 ) Auto
correlation function
” 1) is an even function of t
” 2) is an odd
function of t
” 3) may be an even or odd function of t
” 4) is both an
odd and even function of t
” 5) None of these
Answer : 1) is an even
function of t
Solution : Auto correlation function is an even function of
t
” ( 23 ) In RLC circuits the state variables generally selected are
” 1)
voltages across capacitors
” 2) currents through resistances and voltages
across capacitors
” 3) currents through resistances and capacitances

4) currents through inductances and voltages across capacitances
” 5) None
of these
Answer : 4) currents through inductances and voltages across
capacitances
Solution : In RLC circuits the state variables generally
selected are currents through inductances and voltages across capacitances.

( 24 ) The theoretical power of white noise is
” 1) infninite
” 2) depend
upon frequency of signal
” 3) finite
” 4) zero
” 5) None of
these
Answer : 2) depend upon frequency of signal
Solution : The
theoretical power of white noise is depend upon frequency of signal
” ( 25 )
If f(t) is an even function, the coefficients Fn in the exponential form of
Fourier series
” 1) are real
” 2) are imaginary
” 3) are complex

” 4) may be real or imaginary
” 5) None of these
Answer : 1) are real

Solution : If f(t) is an even function, the coefficients Fn in the
exponential form of Fourier series are real
” ( 26 ) For a ______ channel, we
need to use the Shannon capacity to find the maximum bit rate.
” 1) noisy

” 2) noiseless
” 3) bandpass
” 4) low-pass
” 5) low
rate
Answer : 1) noisy
Solution : For a noisy channel, we need to use the
Shannon capacity to find the maximum bit rate.
” ( 27 ) For a ______ channel,
the Nyquist bit rate formula defines the theoretical maximum bit rate.
” 1)
noisy
” 2) noiseless
” 3) bandpass
” 4) low-pass
” 5) low
rate
Answer : 2) noiseless
Solution : For a noiseless channel, the
Nyquist bit rate formula defines the theoretical maximum bit rate.
” ( 28 )
Baseband transmission of a digital signal is possible only if we have a ____
channel.
” 1) low-pass
” 2) bandpass
” 3) low rate
” 4) high rate

” 5) None of these
Answer : 1) low-pass
Solution : Baseband
transmission of a digital signal is possible only if we have a low-pass
channel.
” ( 29 ) The _____ of a composite signal is the difference between
the highest and the lowest frequencies contained in that signal
” 1)
frequency
” 2) period
” 3) bandwidth
” 4) amplitude
” 5) None of
these
Answer : 3) bandwidth
Solution : The bandwidth of a composite
signal is the difference between the highest and the lowest frequencies
contained in that signal
” ( 30 ) A sine wave in the ______ domain can be
represented by one single spike in the _____ domain.
” 1) time; frequency

” 2) frequency; time
” 3) time; phase
” 4) phase; time
” 5) None
of these
Answer : 1) time; frequency
Solution : A sine wave in the time
domain can be represented by one single spike in the frequency domain.
” ( 31
) ________is the rate of change with respect to time.
” 1) Amplitude
” 2)
Time
” 3) Frequency
” 4) Voltage
” 5) None of these
Answer : 3)
Frequency
Solution : Frequency is the rate of change with respect to
time.
” ( 32 ) What does the spectral density function of any signal
specify?
” 1) Distribution of energy or power
” 2) Consumption of energy
or power
” 3) Conservation of energy or power
” 4) Generation of energy
or power
” 5) None of these
Answer : 1) Distribution of energy or power

Solution : the spectral density function of any signal specify distribution
of energy or power
” ( 33 ) The ESD of a real valued energy signal is always
________
” 1) An even (symmetric) function of frequency
” 2) An odd
(non-symmetric) function of frequency
” 3) A function that is odd and
half-wave symmetric
” 4) None of the above
Answer : 1) An even
(symmetric) function of frequency
Solution : The ESD of a real valued energy
signal is always n even (symmetric) function of frequency
” ( 34 ) Where does
the maximum value of auto-correlation function of a power signal occur?
” 1)
At origin
” 2) At extremities
” 3) At unity
” 4) At infinity

5) None of these
Answer : 1) At origin
Solution : At origin the maximum
value of auto-correlation function of a power signal occur.
” ( 35 ) What
would happen if the value of term [(m-x) / (? ? 2)] increases in the expression
of Guassian CDF?
” 1) Complementary error function also goes on increasing

” 2) Complementary error function goes on decreasing
” 3) Complementary
error function remains constant or unchanged
” 4) Cannot predict
” 5)
None of these
Answer : 2) Complementary error function goes on decreasing

Solution : if the value of term [(m-x) / (? ? 2)] increases in the
expression of Guassian CDF Complementary error function goes on decreasing

( 36 ) What is the value of an area under the conditional PDF ?
” 1) Greater
than ‘0’ but less than ‘1’
” 2) Greater than ‘1’
” 3) Equal to ‘1’

4) Infinite
” 5) None of these
Answer : 3) Equal to ‘1’
Solution :
the value of an area under the conditional PDF equal to 1
” ( 37 ) According
to Rayleigh’s theorem, it becomes possible to determine the energy of a signal
by________
” 1) Estimating the area under the square root of its amplitude
spectrum
” 2) Estimating the area under the square of its amplitude spectrum

” 3) Estimating the area under the one-fourth power of its amplitude
spectrum
” 4) Estimating the area exactly half as that of its amplitude
spectrum
” 5) None of these
Answer : 2) Estimating the area under the
square of its amplitude spectrum
Solution : According to Rayleigh’s theorem,
it becomes possible to determine the energy of a signal by Estimating the area
under the square of its amplitude spectrum.
” ( 38 ) Where is the ROC defined
or specified for the signals containing causal as well as anti-causal
terms?
” 1) Greater than the largest pole
” 2) Less than the smallest
pole
” 3) Between two poles
” 4) Cannot be defined
Answer : 3)
Between two poles
Solution : ROC defined Between two poles for the signals
containing causal as well as anti-causal terms.
” ( 39 ) According to the
time-shifting property of Laplace Transform, shifting the signal in time domain
corresponds to the ______
” 1) Multiplication by e-st0 in the time domain

” 2) Multiplication by e-st0 in the frequency domain
” 3) Multiplication
by est0 in the time domain
” 4) Multiplication by est0 in the frequency
domain
” 5) None of these
Answer : 2) Multiplication by e-st0 in the
frequency domain
Solution : According to the time-shifting property of
Laplace Transform, shifting the signal in time domain corresponds to the
Multiplication by e-st0 in the frequency domain
” ( 40 ) Which result is
generated/ obtained by the addition of a step to a ramp function ?
” 1) Step
function of zero slope
” 2) Ramp function of zero slope
” 3) Ramp
Function shifted by an amount equal to step
” 4) Step Function shifted by an
amount equal to ramp
” 5) None of these
Answer : 3) Ramp Function shifted
by an amount equal to step
Solution : Ramp Function shifted by an amount
equal to step by the addition of a step to a ramp function.
” ( 41 )
Generally, the convolution process associated with the Laplace Transform in time
domain results into________
” 1) Simple multiplication in complex frequency
domain
” 2) Simple division in complex frequency domain
” 3) Simple
multiplication in complex time domain
” 4) Simple division in complex time
domain
” 5) None of these
” ( 42 ) The tree selected for the formation of
state equations contains
” 1) all voltage sources
” 2) all capacitors

” 3) all inductors and current sources
” 4) all voltage sources and
maximum number of capacitors
” 5) None of these
Answer : 4) all voltage
sources and maximum number of capacitors
Solution : The tree selected for
the formation of state equations contains all voltage sources and maximum number
of capacitors
” ( 43 ) For a second order system, damping ratio ? is such
that 0 < ? <. Then the roots of characteristic equation are
” 1) real
but not equal
” 2) imaginary
” 3) complex conjugate
” 4) real and
equal
” 5) None of these
Answer : 3) complex conjugate
Solution : For
a second order system, damping ratio ? is such that 0 < ? <. Then the
roots of characteristic equation are complex conjugate
” ( 44 ) The inverse
Laplace transform of 1/(s – a)2 is
” 1) eat
” 2) t eat
” 3) t2 eat

” 4) eat/t
” 5) t/eat
Answer : 2) t eat
Solution : The inverse
Laplace transform of 1/(s – a)2 is t eat
” ( 45 ) The discrete time system
describes by y(n) = x(n2) is
” 1) non-casual, non-linear, time variant

2) non-casual, Linear, time invariant
” 3) casual, non-linear, timevari

” 4) casual, Linear, time varying
” 5) casual, Linear, time
invariant
Answer : 4) casual, Linear, time varying
Solution : The
discrete time system describes by y(n) = x(n2) is casual, Linear and time
varying
” ( 46 ) The integral of k u(t) is
” 1) 1/k ?(t)
” 2) k ?(t)

” 3) a ramp of slope 1/k
” 4) a ramp of slope k
” 5) None of
these
Answer : 4) a ramp of slope k
Solution : The integral of k u(t) is
a ramp of slope k
” ( 47 ) In a complex wave, the negative half of the wave
is a reproduction of the positive half wave. Then
” 1) the wave does not
contain triple harmonics
” 2) the wave does not contain odd harmonics

3) the wave does not contain even harmonics
” 4) the wave contains only
fundamental and third harmonic
Answer : 3) the wave does not contain even
harmonics
Solution : In a complex wave, the negative half of the wave is a
reproduction of the positive half wave. Then the wave does not contain even
harmonics
” ( 48 ) Which of the following is/are not a property/properties
power spectral density function Sx(?)?
” 1) Sx(?) is real function of ?

2) Sx(?) is a even function of ?
” 3) Sx(?) is a odd function of ?
” 4)
Sx(?) is non-positive function of ?Sx(?) ? 0 for all ?
” 5) All of the
above
Answer : 4) Sx(?) is non-positive function of ?Sx(?) ? 0 for all ?

Solution : Properties of power spectral density function Sx(?):
Sx(?) is
real function of ?
Sx(?) is a even function of ?
Sx(?) is a odd function
of ?
” ( 49 ) For Ergodic Process
” 1) ensemble Average equal to time
Average
” 2) ensemble Average is not equal to time Average
” 3) ensemble
Average > Time Average
” 4) ensemble Average < Time Average
” 5)
both 1 & 3
Answer : 1) ensemble Average equal to time Average

Solution : For Ergodic Process ensemble Average equal to time Average

( 50 ) FIR digital filter having __________ stability than FIR filter.
” 1)
good stability
” 2) poor stability
” 3) stability not guarnteed
” 4)
poor stability
” 5) None of these
Answer : 1) good stability
Solution
: FIR digital filter having good stability stability than FIR filter.

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