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WorksheetsSignals & Systems Phase 1
Total questions: 80
Worksheet time: 1hrs 20mins
Name
Class
Date
1.
The type of systems which are characterized by input and the output quantized at certain levels are called as
a)
analog
b)
discrete
c)
continuous
d)
digital
2.
The type of systems which are characterized by input and the output capable of taking any value in a particular set of values are called as
a)
Analog
b)
Discrete
c)
Digital
d)
Continuous
3.
Should real time instruments like oscilloscopes be time invariant?
a)
Yes
b)
Sometimes
c)
Never
d)
They have no relation with time variance
4.
A system is said to be defined as non causal, when
a)
the output at the present depends on the input at an earlier time
b)
the output at the present does not depend on the factor of time at all
c)
the output at the present depends on the input at the current time
d)
the output at the present depends on the input at a time instant in the future
5.
What is the other name of a Continuous Time Unit Impulse Function?
a)
Dirac delta function
b)
Unit function
c)
Area function
d)
Direct delta function
6.
Why is the impulse duration important?
a)
It is zero
b)
It changes with time
c)
It approaches zero
d)
It depends on the situation
7.
What is a doublet function?
a)
Branch of an impulse function
b)
The output of an impulse function
c)
The first derivative of an impulse function
d)
Any continuous time impulse function has another name that is doublet function
8.
How are discrete unit impulse functions and discrete time unit step functions related?
a)
They are inverse of each other
b)
∂(n)=u(n)-u(n-1)
c)
∂(n)=u(n)*2∂
d)
Integration of unit step function gives unit step function
9.
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
10.
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
11.
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
12.
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
13.
If a function f(t) u(t) is shifted to right side by t0,then the function can be expressed as
a)
f(t – t0) u(t)
b)
f(t) u(t – t0)
c)
f(t – t0) u(t – t0)
d)
f(t +t0) u(t + t0)
14.
Which block of the discrete time systems requires memory in order to store the previous input?
a)
Signal Multiplier
b)
Unit Delay
c)
Adder
d)
None of the above
15.
The covariance function of a band limited white noise is
a)
A Dirac delta function
b)
An exponentially decreasing function
c)
A sinc function
d)
A sinc2 function
16.
A discrete LTI system is non-causal if its impulse response is
a)
anu(n -2)
b)
an-2u(n)
c)
an+2u(n)
d)
anu(n +2)
17.
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
18.
What does the transfer function of a system describe for the system ?
a)
Only zero-input response
b)
Only zero-state response
c)
Both zero-input and zero-state response
d)
Neither zero-input response nor zero-state response
19.
Which one of the following is the correct statement ? The system characterized by the equation y(t) = ax(t) + b is
a)
linear for any value of b
b)
linear if b > 0
c)
linear if b < 0
d)
non-linear
20.
Which one of the following systems described by the following input-output relations is non-linear ?
a)
y(n) = n x(2n)
b)
y(n) = x (n2)
c)
y(n) = n2x(n)
d)
y(n) = x2(n)
21.
A function of one more variables which conveys information on the nature of physical phenomenon is called
a)
Noise
b)
Interference
c)
System
d)
Signal
22.
Which one of the following is correct ? Energy of a power signal is
a)
Finite
b)
Zero
c)
Infinite
d)
Between 1 And 2
23.
Which one of the following is correct ? A system can be completely described by a transfer function if it is
a)
Non-Linear And Continuous
b)
Linear And Time-Varying
c)
Non-Linear And Time-Invariant
d)
Linear And Time Invariant
24.
Convolution of two sequences X1 Z[n] and X2 [n] is represented as
a)
X1(z)* X2(z)
b)
X1(z) X2 (z)
c)
X1 (z) + X2(z)
d)
X1(z)/X2(z)
25.
Laplace transforms of f(t) and g(t) are F(s) and G(s), respectively. Which one of the following expressions gives the inverse Laplace transform of F(s) G(s) ?
a)
f(t) g(t)
b)
f(t) /g(t)
c)
f(t) + g(t)
d)
f(t) *g(t)
26.
The lengths of two discrete time sequence x1(n) and x2(n) are 5 and 7, respectively. What is the maximum length of a sequence x1(n)*x2(n) ?
a)
5
b)
6
c)
7
d)
11
27.
If the response of a system to an input does not depend on the future values of the input.Then which one of the following is true for the system ?
a)
It Is Aperiodic
b)
It Is Causal
c)
It Is Anticipator
d)
It Is Discrete
28.
What is the number of roots of the polynomial F(z) = 4z3 – 8z2 –z + 2, lying outside the unit circle ?
a)
0
b)
1
c)
2
d)
3
29.
Two rectangular waveforms of duration T1 and T2 seconds are convolved. What is the shape of the resulting waveform ?
a)
Triangular
b)
Rectangular
c)
Trapezoidal
d)
Semi-circular
30.
What are the number of samples present in an impulse response called as?
a)
String
b)
Array
c)
Length
d)
Element
31.
The poles of a digital filter with linear phase response can lie
a)
only at z = 0
b)
only on the unit circle
c)
only inside the unit circle but not at z = 0
d)
on the left side of Real (z) =0 line
32.
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
33.
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
34.
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)
None of the above
35.
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
36.
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
37.
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
38.
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
39.
What is the area under a doublet function?
a)
Unity
b)
Negative
c)
Zero
d)
Positive
40.
What are the singularity functions?
a)
Derivatives and integrals of unit impulse functions
b)
Derivatives of a unit impulse function
c)
Integrals of an impulse function
d)
Sum of successive impulse function
41.
An example of a discrete set of information/system is
a)
the trajectory of the Sun
b)
data on a CD
c)
universe time scale
d)
movement of water through a pipe
42.
A system which is linear is said to obey the rules of
a)
scaling
b)
additivity
c)
both scaling and additivity
d)
homogeneity
43.
A time invariant system is a system whose output
a)
increases with a delay in input
b)
decreases with a delay in input
c)
remains same with a delay in input
d)
vanishes with a delay in input
44.
All real time systems concerned with the concept of causality are
a)
non causal
b)
causal
c)
neither causal nor non causal
d)
memoryless
45.
When we take up design of systems, ideally how do we define the stability of a system?
a)
A system is stable, if a bounded input gives a bounded output, for some values of the input
b)
A system is unstable, if a bounded input gives a bounded output, for all values of the input
c)
A system is stable, if a bounded input gives a bounded output, for all values of the input
d)
A system is unstable, if a bounded input gives a bounded output, for some values of the input
46.
All causal systems must have the component of
a)
memory
b)
time invariance
c)
stability
d)
linearity
47.
What is the area of a Unit Impulse function?
a)
Zero
b)
Half of Unity
c)
Depends on the function
d)
Unity
48.
A periodic signal is
a)
Repeats itself at regular intervals
b)
May be represented by g(t) = g(t + T0)
c)
Value may be determined at any point
d)
All of the above
49.
Sine wave is a
a)
Periodic signal
b)
Deterministic signal
c)
Aperiodic signal
d)
Both a and c
50.
In Unit impulse function
a)
Height of pulse goes to infinity
b)
Area of pulse curve is unity
c)
Pulse width is zero
d)
All of the above
51.
For a Unit ramp function area of pulse curve is unity
a)
Starts at time t=0 and linearly increases with t
b)
Discontinuous at time t=0
c)
Both a and b
d)
None of the above
52.
The desired signal of maximum frequency wm centered at frequency w=0 may be recovered if
a)
Filter has the cut off frequency wm
b)
The sampled signal is passed through low pass filter
c)
Both a and b
d)
None of the above
53.
Calculate the minimum sampling rate to avoid aliasing when a continuous time signal is given by x(t) = 5 cos 400πt
a)
400 Hz
b)
250 Hz
c)
100 Hz
d)
None of the above
54.
Calculate the Nyquist rate for sampling when a continuous time signal is given by x(t) = 5 cos 100πt +10 cos 200πt – 15 cos 300πt
a)
300Hz
b)
150Hz
c)
600Hz
d)
None of the above
55.
A low pass filter is
a)
Is used to recover signal from sampled signal
b)
Passes the frequencies lower than the specified cut off frequency
c)
Rejects higher frequencies
d)
All of the above
56.
The instantaneous sampling
a)
Has the negligible power content
b)
Has a train of impulses
c)
Has the pulse width approaching zero value
d)
All of the above
57.
The sampling technique having the minimum noise interference is
a)
Natural sampling
b)
Flat top sampling
c)
Instantaneous sampling
d)
None of the above
58.
Superposition of signals in a linear system refers to the
a)
Output that is product of all the signals
b)
Output that is sum of all the signals
c)
Output that is of highest amplitude of all the signals
d)
Output that is of largest spectrum of all the signals
59.
Random signals is
a)
May be specified in time
b)
Occurrence is random
c)
Repeat over a period
d)
None of the above
60.
An even function f(x) for all values of x and x holds
a)
f(x) = f(-x)
b)
f(x) = f(x)f(-x)
c)
f(x) = -f(x)
d)
None of the above
61.
Unit step function is
a)
Exists only for positive side
b)
Is zero for negative side
c)
Discontinuous at time t=0
d)
All of the above
62.
The spectrum of the sampled signal may be obtained without overlapping only if
a)
fs ≥ 2fm
b)
fs < fm
c)
fs < 2fm
d)
fs > fm
63.
A distorted signal of frequency fm is recovered from a sampled signal if the sampling frequency fs is
a)
fs < 2fm
b)
fs ≥ 2fm
c)
fs > 2fm
d)
fs = 2fm
64.
The techniques used for sampling are
a)
Flat top sampling
b)
Instantaneous sampling
c)
Natural sampling
d)
All of the above
65.
Types of analog pulse modulation systems are
a)
Pulse amplitude modulation
b)
Pulse time modulation
c)
Frequency modulation
d)
Both a and b
66.
In pulse amplitude modulation,
a)
Amplitude of the pulse train is varied
b)
Width of the pulse train is varied
c)
Frequency of the pulse train is varied
d)
None of the above
67.
Pulse time modulation (PTM) includes
a)
Pulse width modulation
b)
Pulse position modulation
c)
Pulse amplitude modulation
d)
Both a and b
68.
As per sampling theorem –
a)
Twice each cycle of its highest frequency
b)
Guard time should be as large as possible
c)
The signal should be sampled at least twice each cycle of its lowest frequency
d)
Nyquist rate should be as low as possible
69.
In communication the sampling technique leads to –
a)
Higher speed of communication
b)
cheaper equipment
c)
Higher efficiency
d)
All of the above
70.
Impulse modulation systems, The number of samples required to ensure no loss of information is given by –
a)
Parsevals theorem
b)
Fourier transmission
c)
Nyquist theorem
d)
None of the these
71.
If the sampling time is less than the Nyquist interval :
a)
Simpler filters can be used to obtain the original signal
b)
Channel Capacity increases
c)
Bandwidth increases
d)
Guard time becomes less
72.
The scaling of a sequence x[n] by a factor α is given by
a)
y[n] = α [x[n]]2
b)
y[n] = α x[n2]
c)
y[n] = α x[n]
d)
y[n] = x[n]x[-n]
73.
Causal systems are the systems in which
a)
The output of the system depends on the present and the past inputs
b)
The output of the system depends only on the present inputs
c)
The output of the system depends only on the past inputs
d)
The output of the system depends on the present input as well as the previous outputs
74.
Roll-off factor is
a)
The bandwidth occupied beyond the Nyquist Bandwidth of the filter
b)
The performance of the filter or device
c)
Aliasing effect
d)
None of the above
75.
A signal x[n] is anti symmetric or odd when
a)
x[-n] = x[n] • x[n]
b)
x[n] = -x[n]
c)
x[n] = [x[n]]2
d)
x[-n] = -x[n]
76.
A signal of maximum frequency of 10 kHz is sampled at Nyquist rate. The time interval between two successive sample is –
a)
50 µs
b)
100 µs
c)
1000 µs
d)
5 µs
77.
Time reversal of a discrete time signal refers to
a)
y[n] = x[-n+k]
b)
y[n] = x[-n]
c)
y[n] = x[-n-k]
d)
y[n] = x[n-k]
78.
Time shifting of discrete time signal means
a)
y[n] = x[n-k]
b)
y[n] = x[-n-k]
c)
y[n] = -x[n-k]
d)
y[n] = x[n+k]
79.
As time tends to infinity magnitude tends to zero means its a
a)
Energy Signal
b)
Power Signal
c)
Periodic signal
d)
Ramp Signal
80.
As time tends to infinity magnitude doesn't tends to zero means
a)
Power Signal
b)
Energy Signal
c)
Impulse Signal
d)
None of Above
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