# Analog and Digital communications ND09 3rd CS2204

B.E/B.Tech EXAMINATIONS,NOVEMBER/DECEMBER 2009
THIRD SEMESTER
COMPUTER SCIENCE AND ENGINEERING
CS 2204-ANALOG AND DIGITAL COMMUNICATIONS
(REGULATIONS 2008)

PART A-(10X2=20 marks)

1.A carrier wave is represented by equation s(t)=12sinwt.Draw the wave form of an AM wave for depth of modulation of 0.5.
2.Compare FM with AM
3.What is coherent detection?
4.Why is binary ASK called on-off keying?
5.What are the errors in DM?
6.Define companding
7. What are the two methods of error detection and correction?
8.What do you mean by signaling rate?
9.Define processing gain
10.What is CDMA?

PART B-(5X16=80 marks)

11.(a)(i)The output voltage of a transmitter is given by 500(1+0.4sin3140t)cos6.28X10^7t
This voltage is fed to a load of 600 ohms.Determine
1.Carrier frequency
2.Modulating frequency
3.Carrier power (9)
Or
(b)(i)Carrier frequency modulated with a sinusoidal signal of 2kHz resulting in a maximum frequency deviation of 5kHz.Find
1.Modulating index
2.Bandwidth of modulated signal (4)
(ii)Explain the method of generating FM signal using indirect method(12)

12.(a)(i)Explain the coherent binary FSK system with a neat diagram of transmitter and receiver(12)
Or
(b)(i)Explain the generation and detection of coherent QPSK system in detail(12)
(ii)What is DPSK?Explain its bandwidth requirements.

13.(a)(i)Explain in detail about DPCM with suitable diagram(10)
(ii)1kHz signal is sampled by 8kHz sampling signal and the samples are encoded with 12 bit PCM system.Find
1.Required bandwidth for PCM system
2.Total number of bits in the digital output signal in 10 cycles(6)
Or
(b)(i)Write short notes on ISI(6)
(ii)What is eye pattern?Explain how is the performance of a base-band pulse transmission system measured with this?(10)

14(a)(i)Write short notes on error correcting codes
(ii)Find the generator polynomial of (7,4) cyclic code and find the codeword for the message 1001(12)
Or
(b)Explain in detail about the serial interface with its control signals and timing information(16)

15(a)(i)What are pseudo noise sequences?How are they generated?(6)
(ii)Explain direct sequence spread spectrum system in detail(10)
Or
(b)(i)Explain 2 types of FH spread spectrum systems with suitable diagrams(16)