PRINCIPLES OF COMMUNICATION ENGINEERING

QUESTION BANK

UNIT - I

AMPLITUDE MODULATION

PART- A (2 MARKS)

1. Define amplitude modulation?

2. What is AM envelope?

3. Write the bandwidth of AM?

4. What is the need of modulation index?

5. Which one is called as percent modulation?

6. Define low level modulation?

7. Define heterodyning?

8. Calculate the BW of FM signal whose frequency deviation is 75 KHZ and signal frequency

is 2.5 KHZ?

9. What are the two major limitations of the standard form of amplitude modulation?

10. Define modulation index for AM?

PART- B

1. Draw the amplitude modulated wave equation and explains each term with the help of

frequency spectrum (16)

2. a) Define amplitude modulation. Derive an expression for the AM wave. (8)

b) Explain in detail about am voltage distribution

3. a) Draw the block diagram high level AM transmitter and explain the function of each

block. (8)

b) Derive the waveform of power relation between carrier power and total transmitter

power of AM signal. (8)

4. a) Draw the waveform AM signal for over modulation, under modulation and 100%

modulation (8)

b) With the help of neat block diagram explain functioning of a super heterodyne receiver

list out signifance. (8)

5. a) State the advantage, disadvantage and applications of AM (8)

b) With the help of block diagram explain the operation of a low level AM transmitter (8)

6. a) Explain the detection of AM signals using envelope detector. (8)

b) Mention the draw backs of a TRF Receiver. (8)

UNIT – II

ANGLE MODULATION

PART- A (2 MARKS)

1. What is angle modulation?

2. Define phase modulation?

3. Illustrate the relation between frequency modulation and phase modulation?

4. What is phase deviation?

5. What is modulation index of PM?

6. Write the advantages and disadvantages of FM compared to AM?

7. State Carson’s rule of FM bandwidth?

8. Write the advantage of angle modulation over amplitude modulation?

9. How the angle modulated wave forms are classified defends upon modulation

index value?

10. Distinguish between narrow band FM and wide band FM?

PART - B

1. a) Explain the direct method of producing FM with block diagram (8)

b) Draw the block diagram of an FM transmitter and FM wave form modulating signal of

EM sin ω>t. (8)

2. a) Distinguish between FM and AM (8)

b) Explain the pre-emphasis and de-emphasis used in FM Transmitter and receiver (8)

3. a) Explain the process of demodulating FM signal using PLL. (8)

b) Discuss about FM and PM waveforms. (8)

4. Draw the block diagram of wideband FM transmitter based on Armstrong method of FM

generation. Explain its operation. (16)

5. Explain the following

i) Narrow band and wideband of FM signal (8)

ii) Direct and indirect methods of FM generation (8)

6. Draw the block diagram of an FM receiver and explain the working of same. (16)

UNIT - III

DIGITAL MODULATION

PART- A (2 MARKS)

1. Bring out the difference between DPSK and BPSK?

2. Mention any four advantage of digital modulation over analog modulation?

3. Define peak frequency deviation for FSK?

4. What are the advantages of M-ary signaling scheme?

5. Define Deviation ratio?

6. What is meant by frequency shift keying?

7. What do you meant by M-ARY encoding?

8. Define FSK bite rate and baud?

9. What are all the types of FSK system and explain them?

10. Define DPSK?

PART - B

1. Explain in detail about the generation and co-herent detection of QPSK signal with neat

block diagram (16)

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2. Explain the process of generating and detecting DPSK signal with the help of block

diagram and given binary data sequence assigning starting reference bit as one

0010010011. (16)

3. Explain BPSK transmitter and receiver with the help of block diagrams. (16)

4. a) Illustrate the basic idea of correlative coding by considering the specific example of duo

binary signaling (8)

b) Mention the major drawback of detective original binary sequence from the duo binary

coder output and suggest a practical means of avoiding that drawback (8)

5. Explain the generation and detection of DPSK signal. (16)

6. With block diagram explain M-ary PSK Receiver. Compare M-ARY Modulation schemes?

(16)

UNIT- IV

BASEBAND DATA TRANSMISSION

PART-A (2 MARKS)

1. State sampling theorem?

2. What is aliasing?

3. What is PAM?

4. Define source coding theorem?

5. What is Nyquist rate?

6. What is inter symbol interference?

7. What is the purpose of using eye pat tern?

8. Define adaptive delta modulation?

9. What are the types of sampling?

10. What ARE the properties of PAM SIGNALS?

PART B

1. a) Explain inter symbol interference and eye pattern . (8)

b) State and prove sampling theorem. (8)

2. a) Draw the eye diagram and explain its importance in data transmission. (8)

b) Explain adaptive delta modulation. (8)

3 . What are the drawbacks in delta modulation and how they are overcome in adaptive delta

modulation? Explain with the help of neat diagram. (16)

4. a) Describe base band M-ary PAM system for the case of quaternary(M=4)system. (8)

b) Explain about the basic elements of base band binary PAM system with neat block

diagram. (8)

5. Explain in detail the Nyquist criterion for distortion less transmission of base band PAM

signal (16)

UNIT - V

SPREAD SPECTRUM AND MULTIPLE ACCESS TECHNIQUES

PART- A (2 MARKS)

1. Define spread spectrum?

2. List out the various applications of spread spectrum communication?

3. List out various speech coding techniques?

4. Define processing gain?

5. List out the different types of frequency hopping?

6. Compare DS-SS AND FH-SS?

7. List out major multiple access technique?

8. List out any two features of TDMA?

9. Write the problems in CDMA?

10. Why speech coding is done by wireless technique? PRINCIPLES OF COMMUNICATION

PART - B

1. With the help of neat block diagram explain DS spectrum system with coherent binary

PSK. (16)

2. Draw the block diagram of simple PN sequence generator using shift register and obtain

the output sequence. For this output sequence verify the properties of the PN sequence. (16)

3. What is frequency HOP spread spectrum? Explain the generation of slow frequency HOP

spread M-ary FSK and fast frequency HOP spread M-ary FSK with appropriate diagrams.

(16)

4. a) What is spread spectrum modulation? Describe the following features of spread

spectrum modulation. (8)

i) Anti jamming

ii) Ranging

iii) Multiple accessing

iv) Message security

b) Compare FDMA, TDMA and CDMA. (8)

5. Explain the working of multi pulse excited LPC and CODE excited LPC by suitable

diagrams. (16)

6. Explain CDMA system with its features. List out various problems available in CDMA

system. (16)