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Friday, May 27, 2011

Advanced Communication, Digital Communication Viva Question-Answer for 6th Sem




Q1. What is multiplexing?


Ans: Multiplexing is method by which multiple analog message signals or digital data streams are combined into one signal over a shared mediu
ANSWER
Q2. What are different types of multiplexing?


Ans: i) Space-division multiplexing (SDM)
ii) Frequency-division multiplexing (FDM)
iii) Time-division multiplexing (TDM)
iv) Code-division multiplexing (CDM)
ANSWER
Q3. What is TDM?

Ans: TDM is the process of dividing up one communication time slot into smaller time slots.
OR, It is the technique of separating the signal in time is called TDM.


ANSWER
Q4. What do you mean by FDM?

Ans: Frequency division multiplexing is the technique of separating the signal in frequency is reffered as FDM.


ANSWER
Q5. What is Amplitude shift Keying (ASK) ?

Ans: It is a type of digital modulation in which, the digital data modulates amplitude of the carrier.


ANSWER
Q6. What are different types of digital modulation?

Ans: i) Phase shift keying (PSK)
ii) Frequency shift keying (FSK)
iii) Amplitude shift keying (ASK)


ANSWER
Q7. What is Phase shift keying ( PSK)?

Ans: In this technique, the digital data modulates the phase of the carrier.


ANSWER
Q8. What is Frequency shift keying (FSK) ?

Ans: In this technique, the digital data modulates the frequency of the carrier.


ANSWER
Q9. What is Binary Phase shift Keying (BPSK) ?

Ans: In BPSK, binary symbol ‘1’ and ‘0’ modulate the phase of the carrier.


ANSWER
Q10. What is bandwidth of BPSK signal?

Ans: BW=2fb. where fb=1/Tb.


ANSWER
Q11. What do you mean by Differential Phase Shift Keying (DPSK)?

Ans: DPSK is differentially coherent modulation method. It does not need a coherent carrier at the demodulator. The input sequence of binary bits is modified such that the next bit depends upon the previous bit. In DPSK the phase of the carrier changes only on symbol ‘1’, while in BPSK, phase of the carrier get changes both at ‘1’ and at ‘0’. So this is the major difference between DPSK and BPSK.


ANSWER
Q12. What is Bandwidth of DPSK?

Ans: BW= fb.

ANSWER
Q13. Show the phase change in DPSK at the digital input 10111101.


Ans: Draw it by yourself with help of your textbook.
ANSWER
Q14. What is QPSK?

Ans: Quadrature phase shift keying (QPSK) also known as 4-PSK, so the phase get changed at four different point or angle and that is at 45, 135,225 and 315O at the digital input 00,10,11,01 respectively.


ANSWER
Q15. Why JK flip-flop is being used in this type if Keying?

Ans: JK flip-flop is used in this type of keying in order to separate the even an odd bits according to the digital inputs.


ANSWER
Q16. What are the advantages over other types of keying?

Ans: i) The BW required by QPSK is just half of the BPSK.
ii) The information transmission rate is higher.
iii) Carrier power remains constant.


ANSWER
Q17. What is a GUNN DIODE?

Ans: Gunn diode is a bulk semiconductor device, normally made up of N-type semiconductor.

ANSWER
Q18. How would you find the propagation loss for two different known length and voltage of optical fiber.


Ans: Propagation loss= 10/(L1-L2) log V2/V1 .
Where L1,L2 are length of two different optical fiber and V2 and V1 are the voltages across it.

ANSWER
Q19. What is the used formula to find out the bending loss for an optical fiber?


Ans: There is no any fixed formula to find so, bending loss is the relation between the voltages (V) to the diameter (d) of bended optical fiber.
ANSWER


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27 comments:

Anonymous,  May 29, 2011 at 1:51 PM  

thank you...

Anonymous,  May 31, 2011 at 8:43 PM  

thanku u so mch keep it up

Anonymous,  October 4, 2011 at 11:05 AM  

really good! thank u a lot.

Anonymous,  October 22, 2011 at 8:16 PM  

thanks for ur questions

Anonymous,  October 28, 2011 at 1:54 PM  

really this works, thanku....

prasanthi,  October 30, 2011 at 10:14 PM  

very nice thank u

Anonymous,  November 21, 2011 at 3:22 PM  

thanks a lot.

Anonymous,  December 15, 2011 at 9:54 PM  

good work thank u

Anonymous,  March 19, 2012 at 9:14 PM  

thank uuuuuuuu

sachin,  April 20, 2012 at 2:52 PM  

its too good

asha,  May 24, 2012 at 7:03 PM  

very good but needs more

santhu May 27, 2012 at 7:17 PM  

Need more about antenna part..

Anonymous,  May 28, 2012 at 4:20 PM  

thank you

Anonymous,  June 3, 2012 at 11:54 PM  

we need more

Anonymous,  October 17, 2012 at 10:13 AM  

need some more

Anonymous,  November 8, 2012 at 11:04 PM  

thanks.....

raji,  November 16, 2012 at 6:22 AM  

need more questions

City Students November 18, 2012 at 12:19 AM  

Thanks everyone, we are under process to add some more viva questions with their answers, and it'll be uploaded very soon. Till then go through your preferred books.

lokesh kumar,  November 18, 2012 at 9:08 AM  

very informative

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