Anna University Chennai 2005 B.E DIGITAL COMMUNICATIONS - Question Paper

Code: A-20
Time: three Hours Subject: DIGITAL COMMUNICATIONS
Max. Marks: 100


NOTE: There are 11 ques. in all.

ques. one is compulsory and carries 16 marks. ans to Q. 1. must be written in the space given for it in the ans book supplied and nowhere else.

ans any 3 ques. every from Part I and Part II. every of these ques. carries 14 marks.

Any needed data not explicitly given, may be suitably presumed and said.

Q.1 select the accurate or best option in the following: (2x8)

a. The TEom modes of a circular waveguide have a unique characteristic in that the attenuation of these fields continues to

(A) increase at higher frequencies.
(B) reduce at higher frequencies.
(C) constant over the operating band.
(D) reduce at lower part of frequency based and then increases.
b. A Smith chart is used

(A) To compute Current. Voltage.
(C) To compute Power.
(B) To compute
(D) To compute Impedance.
c.
A Dominant mode in a rectangular wave guide is a

(A Non propagating mode.
(B) A propagating mode with least cut off frequency.
(C) Propagating mode with circular polarization.
(D) Hybrid mode.
d. A Microstrip is formed by

(A) 1 conductor ranging from 2 ground planes and dielectric.
(B) 1 conductor and 1 ground plane and dielectric.
(C) 1 conductor surrounded by a circular ground plane and dielectric.
(D) 2 conductors with 1 ground plane and dielectric.
e. A matched termination is a
(A) A tapered Capacitive load
(C) A tapered Resistive load. (B) A tapered Inductive load.
(D) Tuned circuit load.


f. PIN diode is used for

(A) Switching.
(C) Oscillation.
(B) Amplification.
(D) Attenuation.
g.
VSWR stands for

(A) Very Short Waves Receiver.
(C) Voltage Standing Wave Ratio.
(B) Voltage Standing Wave Range.
(D) Variable Source Wave guide
Resonator.
h.
Repeators are circuits
(A) To give attenuation.
(C) To give oscillation. (B) To give feedback.
(D) To give amplification.
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PART I
ans any 3 ques.. every ques. carries 14 marks.
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Q.2 Derive the relevant equations for determining the characteristic impedance of a transmission line.
An open wire transmission line has and . The signal frequency is four GHz. compute

Earning:   Approval pending.