Posted Date: 01 Jun 2019      Posted By:: Tushar Pathak    Member Level: Bronze  Points: 3 (₹ 2)

# 2019 Dayanand Sagar University B.E Electronics & Communication Engineering SS, 4th semester, ECE,2019 Question paper

 Course: B.E Electronics & Communication Engineering University/board: Dayanand Sagar University

Signal and Syestem model paper. Containing short and long answer.Question mainly based on signal and system and time /frequency represantation of time...

1 a.Give the condition for periodicity of sum of two or more signals.
b.Energy signals are signals with
i) 0 c.The result of u(t)-u(t-1) is_______.
d.A DT sinusoidal signal is said to be periodic iff it satisfies the condition__________.
e.Damped sinusoids are sinusoidal signals multiplied by decaying exponentials. (TRUE/FALSE)
f.Unit step signal is ____________
i)Energy signal ii)Power signal iii) neither energy nor power iv)None
g.Convolution of a signal with impulse signal gives_________.
h.Define causality property of a system.
i.What is the length of the convolved sequence of two finite duration signals of length L1 and L2?
j.Name the mathematical operation that relates output of the LTI system with its input and impulse
response.
k.A LTI system is said to be initially relaxed system only if ____
i) Zero input produces zero output ii) Zero input produces non-zero output
iii) Zero input produces an output equal to unity iv) None of the above
l.Give general difference equation representation of DT LTI system.
m.Write the relation between Fourier transform and Z- transform.
n.What do you mean by pole of a Transfer function?
o.The Fourier transform of rectangular pulse is ______
p.The DTFT is Fourier representation of ________
i)Continuous Time Periodic Signal ii)Continuous Time Non periodic Signal
iii)Discrete Time Periodic Signal iii)Discrete Time Non periodic Signal
q.Define Nyquist rate.
r.Sampling process converts a CT signal in to __________
i)Digital signal ii)Discrete time signal iii)Discrete amplitude signal iv)None
s. Anti-aliasing filter is a _________
i) High Pass Filter ii) Low Pass Filter iii) Notch filter iv) All Pass filter
t. If a signal x(t) is sum of three signals of fundamental frequencies 100Hz,155Hz and 325 Hz
respectively the sampling frequency for x(t) is. 1 x 20
2a. Distinguish between Energy and Power signals and hence test whether unit step signal is energy or
power signal by finding its energy and power. 6
b.Given x(t) perform the following operations x(0.5t-3), [x(t+2)+x(t-3) ] 6
c. List any 4 properties of impulse function 4
3 a.Explain with example Linearity property of LTI system. 2
b.Check for time invariance and stability of the system defined by 4
c. Find the response of the system whose impulse response is
for the input for and.Show all the signals and mathematical notations properly. 10
4a.Solve the first order difference equation by using the classical method of solving difference
equations. Find and plot the forced response yf(n) for y(n)+3y(n-1)=0, with zero initial conditions and
x(n)=u[n].Where u[n] is unit step function. 8
b. Using unilateral Z transform method determine the forced response and natural response of the
system described by y[n]-(1/4)y[n-1]-(1/8)y[n-2]=x[n]+x[n-1],where y[-1]=y[-2]=1 for the input
x[n]=3u[n]. 8
5a.Evaluate FS representation of the signal shown below. 6
b.Use the defining equation for the DTFT to evaluate the frequency-domain representations for
the following signal. Sketch the magnitude and phase spectra.
(a) x[n] = (3/4 )n u[n - 4] 10
(OR)
a Evaluate the DTFS representation of below signal. Sketch magnitude and
phase plot. 10
b Determine the inverse FT of 6

6a.Find the FT representation for periodic signal x(t)=cos(wt) and draw the spectrum. 10
b State sampling theorem and briefly explain how to practically reconstruct the signal. 6
(OR)
a. Find the fourier transform of the signum function, x(t)=sgn(t). 6
c. Explain the process of aliasing and significance of anti-aliasing filter. 6
b. Find the Nyquist rate and Nyquist intervals for each of the following signals
a) x(t)=cos(2pt) + cos(5pt) b) g(t)=sinc (200t)+ sinc2(200t) 4

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