MaharashtraState Board of Technical Education

Semester : Fifth Sample Paper-1

Subject: Communication Techniques

Marks: 80Time:3 Hrs

Q. 1. Attempt any four.16

  1. Compare AM, FM on the basis of Bandwidth requirement, waveform ,noise and modulation index.
  2. Define Critical Frequency and Fading.
  3. Describe working principle of TDMA with diagram.
  4. Define data rate, bit rate, channel capacity and channel bandwidth.
  5. List applications of satellite and describe any one.
  6. List advantages of pulse communication over analog communication.

Q. 2. Attempt any three.12

  1. Draw the block diagram of communication system and state function of each block.
  2. Draw block diagram of AM transmitter.
  3. Explain effect of changes in atmospheric conditions on sky wave propagation.
  4. Define azimuth angle and elevation angle with sketch.

Q. 3. Attempt any three.12

  1. How frequency reuse and cell splitting take place in mobile communication?
  2. Explain the working principle of Time division multiplexing with sketch.
  3. Define baud rate and describe how it differs from information bit rate?
  4. Describe how T-lines can be used for digital transmission.

Q. 4 Attempt any two.16

  1. Study the input and output waveforms given below.

Input waveformOutput waveform

  1. Identify waveforms.II.Describe the process of generation.
  1. Draw and explain block diagram of cellular mobile phone system.
  2. Describe different analog and digital services provided by Telephone Company.

Q. 5. Attempt any three.12

  1. Define modulation and demodulation. Why it is required?
  2. Assume a data stream consisting of 12 bits and draw the encoded waveform using unipolar encoding technique.
  3. Describe Ground wave propagation. What is angle of twist?
  4. Describe HDB3 and B8ZS.

Q. 6. Attempt any three.12

  1. State and explain sampling theorem.
  2. Draw block diagram of satellite communication system.
  3. What is encoding? How digital data is converted to digital signal?
  4. Describe forward and reverse call processing.

MaharashtraState Board of Technical Education

Semester : Fifth Sample Paper-2

Subject: Communication Techniques

Marks: 80Time:3 Hrs

Q. 1. Attempt any four.16

  1. what is the difference between simplex, half duplex and duplex systems, also give its examples.Give the Importance of communicationDefine Critical Frequency and Fading.
  2. Describe working principle of FDMA with diagram.
  3. Give the classification of encoding techniques.
  4. Give the classification of encoding techniques.
  5. What are the advantages and disadvantages of FDM system.

Q. 2. Attempt any three.12

  1. A modulating signal 15Sin(2 X 103 ) is used to modulate a carrier signal 30Sin(2 X 104 ) Find

(i) Modulation index ii) Percentage modulation

(iii) Frequencies of side band and their amplitude.

  1. Draw block diagram of AM Recevier.
  2. Write short note on Sky wave propogation
  3. What is mean by terms Uplink ,DownLink , transponder , GeoSynchronous satellite

Q. 3. Attempt any three.12

  1. Why handoffs are needed ? Explain the handoff procedure.?List different types of Handsoff
  2. Explain the working principle of Frequency division multiplexing with sketch.
  3. State the types of encoding techniques represent the data 1101101 using following encoding technique.

i) NRZ-1ii)RZ

  1. Describe how analog Hierarchyis be used for transmission.

Q. 4. Attempt any three.12

  1. Study the input and output waveforms given below.

  1. Identify waveforms.
  2. Describe the process of generation.
  1. Draw and explain block diagram of satellite communication system.
  2. Describe the terms DSL , ADSL ,RADSL , HDSL ,SDSL,VDSL

Q. 5. Attempt any three.12

  1. Define modulation and demodulation. Why it is required?
  2. Assume a data stream consisting of 12 bits and draw the encoded waveform using AMI encoding technique.
  3. Describe Duct propagation with neat diagram?Define Critical frequency , Virtual height related to Sky wave propagation.
  4. Describe HDB3 and B8ZS.

Q. 6. Attempt any three.12

  1. Draw the generation block diagram of QPSK and explain its working principle
  2. Related to Antenna Describe the following characteristics
  3. Antenna radiation patterns
  4. Power Gain
  5. Directivity
  6. Polarization
  7. What is access technology?List Different type of access technology?Describe any one in details
  8. Describe interleaving , framing bit and bit stuffing related to Synchronous TDM?

MaharashtraState Board of Technical Education

Semester : Fifth Subject: Communication Techniques

Marks: 20 Test Paper - 1Time:1 Hrs

Q 1. Attempt any two. 08

  1. Draw block diagram of super heterodyne receiver and describe the functionality of IF amplifier.
  2. Define skip and Maximum usable frequency.
  3. What is meant by Nyquist Rate in Sampling? What is the standard sampling frequency for speech signal?

Q.2. Attempt any three. 12

  1. Define modulation index for AM and FM.
  2. Define the term power density and explain why it is inversely proportional to the square of the distance from the source?
  3. Draw the block diagram of digital communication system.

What is quantization noise? Show how it depends on the step size?

MaharashtraState Board of Technical Education

Semester : Fifth Winter : 2008

Subject: Communication Techniques

Marks: 80Time:3 Hrs

1.Attempt any four16

a)Draw and explain the block diagram of communication system.

b)Define

i) Critical frequency ii) Skip distance.

c) State sampling theorem and calculate the Nyquist rate for speech signal of range 300 Hz to 3400 Hz

d)Define:

i) Baud rateii) Bit rateiii) Channel capacity

iv) Channel Bandwidth

e) Compare TDMA and FDMA (4 points).

F ) State any four advantages of digital modulation methods over analog modulation.

2. Attempt any three:12

a) A modulating signal 10Sin(2 X 103 ) is used to modulate a carrier signal 20Sin(2 X 104 ) Find

i) Modulation index ii) Percentage modulation

iii) Frequencies of side band and their amplitude.

b) Draw the block diagram of high level AM transmitter. Explain the function of each block.

c) Illustrate troposphere scatters propagation with neat sketch.

d) Define elevation and Azimuth angles of satellite with neat diagram.

3.Attempt any three:12

a)Why handoffs are needed ? Explain the handoff procedure.

b)Draw the circuit diagram and illustrate the working of PWM.

c) State the types of encoding techniques represent the data 1101101 using following encoding technique.

i) Unipolar NRZii Bipolar NRZ

d) Describe how T-lines can be used for digital transmission.

4. Attempt any two

a) See the diagram in Fig(1)

i) Identify the waveforms

ii)Describe the process of generation.

Fig.(1)

b) Draw and explain the• block diagram of cellular mobile phone system.

c) Describe the working of telephone carrier system.

5. Attempt any three:

a) Represent FM in tune and frequency domain.

b) What are the types of digital to digital encoding ? How encoding differs from modulation ?

c) Draw neat sketch of different layer of Ionosphere and explain the effect of atmosphere on sky wave propagation.

d) Give brief explanation of W.D.M.

6.Attempt any three:12

a) Draw the generation block diagram of QPSK and explain its working principle.

b) State the advantages and disadvantages of CDMA.

c) Explain construction and working principle of parabolic dish antenna.

d) Explain the concept of

i) frequency reuseii) cell splitting

MaharashtraState Board of Technical Education

Semester : FifthSubject: Communication Techniques

Marks: 20 – Test Paper- 2Time:1 Hrs

Q 1. Attempt any two. 08

  1. Represent the data 10110100 using the following data formats with the help of neat diagram.
  2. RZ ii. NRZ
  3. List frequency bands used in satellite communication.
  4. Define Baud rate and bit rate.

Q. 2. Attempt any three.12

  1. Draw the block diagram of communication system and state function of each block.
  2. Draw block diagram of AM transmitter.
  3. Explain effect of changes in atmospheric conditions on sky wave propagation.
  4. Define azimuth angle and elevation angle with sketch.

Maharashtra State Board of Technical Education

Semester : Fifth Winter : 2009

Subject: Communication Techniques

Marks: 80Time:3 Hrs

Q1.Attempt any FOUR of the following

a)Give the classification of communication system.

Define Amplitude modulation and frequency modulation.

b)Define Fading and critical frequency.

c)Describe the working principle of CDMA with neat diagram.

d)Give the classification of different, types of encoding techniques. Define polar and unipolar encoding techniques.

e)Draw the block diagram of satellite communication system and explain h it works.

f)Give the advantages of digital communication over analog communication system.

Q.2.Attempt any three of the following

a)Draw the block diagramof communication system and state function of each

b)Draw block diagram of AM Receiver.

c)Describe the space wave propagation. Give the application of it

d)Describe working principle of Parabolic dish Antenna.

Q3.Attempt any THREE of the following :

a)How hand off mechanism and cell splitting take place in mobile communication.

b)Explain the working principle of Amplitude shift keying modulation (ASK) with waveforms.

c)Represent the data 10110100 using the following fonnats with neat waveforms.

(i)RZ(ii) NRZ—L

d)Describe how T-lines can be used for digital transmissions.

Q4.Attempt any TWO or the following :

a)Describe the generation process of Pulse Amplitude modulatioms with waveform. List the advantages, disadvantages and application of PAM.

b)Describe the uplink model and downlink model used by the satellite communication with neat diagram.

c)Name the different analog and digital services provided by Telephone company. Explain the analog hierarchy.

Q5. Attempt any Three of the following

a)Compare AM and FM on the basis of bandwidth requirement, waveform, noise and modulation index.

b)Consider the data stream 10111001 and encode using unipolar encoding.

c)Describe ground wave propagation. Give advantages and disadvantages of it’s.

d)With a suitable example, explain B8ZS and HDB3 encoding techniques.

Q6.Attempt any THREE of the following :

a)State the sampling theorem. Give the difference between natural sampling and flat top sampling.

b)Draw and explain the block diagram of cellular mobile phone system.

c)Define

(i)Data Rate(ii)Bit Rate(iii) Baud Rate(iv) Channel Bandwidth

d)Draw a block diagram and explain the working of TDM.

MaharashtraState Board of Technical Education

Semester : Fifth Summer : 2010

Subject: Communication Techniques

Marks: 80Time:3 Hrs

Q1.Attempt any FOUR of the following :

a)State need for modulation. Define modulation. State different types of modulation.

b)What is wave propagation ? Describe ground wave propagation.

c)Draw block diagram of PWM generator. State disadvantages of PWM.

d)Define base band and pass band transmission.

e)What is encoding ? How digjtal data is converted to digital signal.

f)What is multiple access ? State its types. State advantages of CDMA.

Q2.Attempt any THREE of the following

a)Describe digital carrier system.

b)Draw and explain block diagram of cellular mobile phone system.

c)Compare TDM and FDM wrt.

(I)Definition(ii)Schematic diagram(iii)Principle

d)Describe antennas used in satellite communication system.

Q3.Attempt any THREE of the following

a)Explain BPSK generation. Draw waveform of BPSK Modulation.

b)Define following terms

(i)Critical frequency(ii)Skip distance(iii)Virtual height(iv)MUF

c)Draw neat diagram of FM transmitter and explain function of each block.

d)Compare AM, FM and PM on the basis of bandwidth requirement and modulation index.

Q4.Attempt any TWO of the following

a)Draw neat waveform of AM signal with m=1, m< 1 and m> I where m- modulation index of AM.

b)State sampling theorem. Define Nyquist rate. Draw waveforms for ideal natural and flat op sampling and compare them.

c)Draw neat block diagram of Adaptive delta modulator. State its advantages and compare DM and ADM waveforms.

Q5.Attempt any THREE of the following :

a)Draw neat block diagram of satellite communication system. State function of up convertor.

b)What is hand off ? Explain hand off procedure.

c)Draw neat block diagram of PCM transmitter. State function of sampling circuit.

d)Define the following terms

(i) Channel capacity,(ii) Bit rate(iii) Band rate(iv) S/N ratio

Q6.Attempt any THREE of the following :

a)Draw block diagram of digital communication system.

b)Define quantization noise. Show how it depends on the step size ?

c)Describe forward and reverse call processing.

d)Represent the data 10100110 using following data format with the help of neat diagram.

(i)RZ(ii) NRZ