PTU B.Tech ECE 4th Semester May 2019 57512 SIGNALS AND SYSTEMS Question Papers

PTU Punjab Technical University B-Tech May 2019 Question Papers 4th Semester Electronic and Communication Engineering (ECE)

Roll No.
Total No. of Pages : 02
Total No. of Questions : 09
B.Tech.(EIE) (2011 & Onwards) (Sem.?4)
SIGNALS AND SYSTEMS
Subject Code : EC-206
M.Code : 57512
Time : 3 Hrs. Max. Marks : 60
INSTRUCTION TO CANDIDATES :
1.
SECTION-A is COMPULSORY consisting of TEN questions carrying T WO marks
each.
2.
SECTION-B contains FIVE questions carrying FIVE marks each and students
have to attempt any FOUR questions.
3.
SECTION-C contains T HREE questions carrying T EN marks each and students
have to attempt any T WO questions.



SECTION-A
Q1. Explain briefly :

a) Define unit ramp signal.

b) What is power spectral density?

c) Sketch the following signal:


x(t) = A[u(t + a) ?u(t - a)] for a > 0

d) What is matched filter?

e) How can you classify Random processes?

f) What is meant by signum function? Explain.

g) Explain the relationship between joint PDF and Probability.

h) Define Analog Signal

i) State the sampling theorem for low pass signals.

j) An amplifier has a bandwidth of 4 MHz with 10k as the input resistor. Calculate the

RMS voltage at the input to this amplifier if the room temperature is 25?C.

SECTION-B
Q2. Find the Fourier transform of an Impulse function x(t) = (t). Also draw its spectrum.
Q3. Show that a system with excitation x(t) and response y(t) described by y(t) = u(x(t)) is non-
linear, time invariant, stable and non-invertible.
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Q4. Explain the joint probability function and its various properties.
Q5. What do you mean by noise? How can you classify the noise?
Q6. A receiver having equivalent input noise resistance of 2500 and input resistance of 500
is connected to an antenna of resistance 50 Calculate the noise figure in dBs and
equivalent noise temperature of the receiver.

SECTION-C
Q7. Find the Fourier Transform of following signals x1(t) and x2(t)
x1(t)
x2(t)
5
A
t
?4
0
t
T
2T
4
?A

FIG.1
Q8. Explain what matched filter is. How it differs from optimum filter? Derive an expression
for error probability of matched filter.
Q9. A random variable X has PDF as :

x


cos
,
4
x 4



f (x) 1
6
8

x


0
elsewhere



Find :

a) Mean value

b) Variance

c) Mean Square value

d) Standard deviation

NOTE : Disclosure of Identity by writing Mobile No. or Making of passing request on any
page of Answer Sheet will lead to UMC against the Student.
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