Anna University Chennai 2005 B.E COMMUNICATION ENGINEERING - Question Paper

Code: A - 15 Subject: COMMUNICATION ENGINEERING
Time: three Hours 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 Choose the accurate or best option in the following: (2x8)

a. FM discriminator modifications FM signal into
(A) AM signal. (B) FM signal of higher intensity.
(C) PM signal. (D) Single side band AM signal.

b. The pre-emphasis circuit in Frequency Modulation system is used
(A) to increase the amplitude of low frequency component of the signal.
(B) to increase the amplitude of high frequency component of the signal.
(C) after the modulation.
(D) prior to modulation.

c. Increasing the peak power by 12 dB in a radar system will increase its range by a factor of about
(A) 2. (B) 4.
(C) 12. (D) 16.

d. Demodulation of SSB-SC requires
(A) an envelop detector. (B) a synchronous detector.
(C) a discriminator. (D) an integrator.

e. The effect of noise in a communication system is most adverse with reference to
(A) channel. (B) encoder.
(C) source / transmitter. (D) receiver.


f. Occurrence of turning up of tail when a coin is tossed has the info equal to
(A) 0 bit. (B) four bit.
(C) eight bit. (D) one bit.
1
Index Next>>g. If x and y are 2 independent Gaussian random variables with avg. zero and with variance , the joint density function is described as
(A) (B)
(C) (D)
h. Assuming R = G = B = one V, fully conducted red is
(A) 0.3 (B) 0.59
(C) 0.11 (D) 1.0
PART I
ans any 3 ques.. every ques. carries 14 marks.
Q.2 a. With the help of neat diagrams and waveforms, discuss generation of DSBFC-AM wave by using a class - C amplifier. What is the maximum collector voltage that the BJT (the active device) should be capable of standing in such modulators? (10)
b. An unmodulated carrier wave has mean power of Po. When it is amplitude modulated by a sinusoid, the power becomes P. Show that the modulation index (4)

Earning:   Approval pending.