MG2351 PRINCIPLES OF MANAGEMENT Questions Bank 2014


Anna University, Chennai

Anna_University,_Chennai_logo

SRINIVASAN ENGINEERING COLLEGE, PERAMBALUR

DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING MG2351 PRINCIPLES OF MANAGEMENT

QUESTION BANK- PART- B

UNIT-I

1. Describe the role of Managers

2. What are the historical inputs for management?

3. What are the difference between Management and Administration?

4. In today’s context explain in detail the different functions of management

5. Elucidate the strategies for international business

6. What are contributions of F.W.Taylor?

7. Draw out clearly whether Management is Science or Art.

8. Discuss in detail about Henri Fayols contribution towards principles of management


UNIT-II

9. Explain the decision making process & its techniques.

10. What are the principles of formulating policies in modern organizations? Explain the essentials of formulating polices.

11. What are the various steps in planning? Discuss the considerations for planning process?

12. What are the modern techniques used in planning process?

13. State the various process of MBO.

14. Describe the formal & informal Organizations.

15. Explain the nature and purpose of organization

16. What are the various types of Plans?


UNIT-III

17. What are the various types of organization? Discuss the merits and demerits of various organizational structures?

18. Explain the nature and purpose of Organizing

19. What are the difference between centralization and decentralization?

20. What are the steps involved in selection process?.

21. Describe the various types of training

22. Explain in detail about the performance appraisal.


UNIT-IV

23. Explain various theories of motivation?

24. Explain the different form of motivation technique.

25. Explain various types of leadership?

26. Explain the process of Communication.

27. Elucidate the barriers in Communication.

28. Describe in detail about the organization culture

29. Explain in detail about the creativity and innovation


UNIT-V

30. What are the various methods of control techniques?

31. Explain in detail about the maintenance control and Quality control

32. Describe the process of controlling

33. Explain the various types of control

34. Explain in detail about the cost control and purchase control

35. Describe the importance of controlling.

EC2352-COMPUTER NETWORKS Questions Bank 2014


Anna University, Chennai

Anna_University,_Chennai_logo

SRINIVASAN ENGINEERING COLLEGE

PERAMBALUR

DEPARTMENT OF ELECCTRONICS AND COMMUNICATION ENGINEERING

EC2352-COMPUTER NETWORKS PREPARED BY: RAGHAVENDRA REDDY.MALAPATI

UNIT-I

PHYSICAL LAYER PART-A

1. What are the five important components of data communication?

2. List two advantages of layering principle in computer networks.

3. With the example explain half duplex communication.

4. Mention any two functions of session layer.

5. Name four topologies of computer networks.

6. Suggest two points to improve the performance of network.

7. With the example explain half duplex communication.

8. Define protocol.

9. Differentiate guided and unguided media.

10. What is the Null modem?

11. Define Topology.

12. Define standards.

13. What are the design factors for transmission media?

14. Difference between Guided media and un guided media.

15. Define line coding.

16. What are most popular modems?

17. Define network.

18. What are the criteria for networks for networks?

19. Define point to point and Multi point.

20. What is DSL

PART-B

1. Explain the OSI-ISO model I of computer with neat diagram. (16)

2. Distinguish between Point to Point links and multi-point links

Raghavendra Reddy Malapati Page 1

with relevant diagram. (16)

3. (i) compare connection oriented and connection less service. (8)

(ii) Differentiate Guided media and un guided media. (8)

4. Write shot notes on

a. TCP/IP protocol suite(4)

b. Networks Model(4)

c. datagram network(4)

d. Virtual circuit network(4)

5. Perform a comparative study between the ISO-OSI model and TCP/IP

reference model. (16)

6.Explain how cable TV used for data transfer?

7.Explain different switched networks

1. Define framing?

2. What is byte stuffing?


UNIT-II DATA LINK LAYER

PART-A ( 2Marks)

3. Write the importance of CRC in the network.

4. Sketch the Manchester encoding for the bit steam 0001110101.

5. Name the protocols used for CSMA

6. Wireless network and mobile networks are not identical explain

7. What is importance of hamming distance? What is Manchester Encoding?

8. What is mean by count to infinity problem?

9. What is Manchester Encoding?

10. What is the importance of variable sized sliding window in TCP?

11. Explain Aloha protocol.

12. Give the significance of termination.

13. What is IEEE 802.4 Standard?

14. Define Syndrome?

15. What are the various ARQ Retransmission strategies?

16. What is mediea sharing? State types of media sharing

17. State different IEEE 802 protocol.

18. Define throughput.

19. Define collision?

20. What is VLAN

21.Differentiate Wired LAN and Wireless LAN

22. What is Bluetooth?.

PART-B

Raghavendra Reddy Malapati Page 2

1. Write short notes on. a. GO Back NARQ (8)

b. Selective Repeat ARQ (8)

2. (i) ExplainProtocols for noiseless and Noisy channels. (8)

(ii) Explain numbering of frames in GO Back NARQ, Selective Repeat ARQ protocols. (8)

3. (i) Explain Ethernet protocol. (8)

(ii) Explain MAC sub layer protocol and frame structure of IEEE 802.11. (8)

4.Discuss in detail about standard ETHERNET

5. Discuss in detail about Gigabit Ethernet

6. (i) Explain any one of the protocols used for flow control in noisy channels. (8)

(ii) Write short note on architecture and layers of Frame relay and ATM

7. Explain in detail about connecting devices

1. What is subnetting?


UNIT-III NETWORK LAYER

PART-A (2 Marks)

2. What is the use of IP address?

3. State the difference between classless and classful addressing.

4. What is the difference between direct and indirect delivery.

5. What is the purpose of RIP.

6. what is the use of BGP.

7. What is the use of routing table.

8. Define Datagram.

9. Define Internet works?

10. What are the different type switching.

11. What is use the of Router?

12. What is the use of network layer?

13. What is MTU?

14. Define Fragmentation offset

15. Write the difference between bridge routers.

16. Find the error if any the following IP address. a. 111.56.045.78 b. 75.45.301.14

17. Where the routing table is maintained also state the purpose of maintaining a routing table.

18. What is datagram socket?

19. Write any four routing algorithm.

20. What is an IP address?

Raghavendra Reddy Malapati Page 3

PART-B

1. Find the class of each IP address given suitable explanation. (16)

a. 227.12.14.87 b.193.14.56.22 c. 14.23.120.8

d. 252.5.15.111 e. 134.11.78.56

f. 000 000 00 1111 0000 11111111 00110011 g. 10000000 1111 0000 11111111 00110011

2. What is BOOTP and explain.

3. State the major difference between Vector Routing and link state routing. (16)

4. Discuss ARP and RARP

5. What is the subnet work address if the destination address is 200.45.34.56 and the subnet mask is 255.255.240.0. (16)

6. What are the limitations of distance vector routing.

7. Explain Unicast and Multicast protocols. (16)

8.Explain the following DHCP,ICMP and IGMP


UNIT-IVTRANSPORT LAYER

PART-A ( 2 Marks)

1. What is the maximum case of UDP datagram?

2. What is the use of sequence numbers?

3. What is the source post numbers?

4. What is client process?

5. Name the policies that can precast congestion?

6. How are congestions control and quality of source hexapod?

7. What is the definition of burst data?

8. What is traffic shaping? Name two methods of shape traffic?

9. What determine the sender Window size in TCP

10. How is Resource Reservation Protocol related to integrated services

11. What is Traffic descriptor?

12. What is Access rate ?

13. What is the methods to improve Qos?

14. What is necessity of flow control

15. What is multicast? What is the difference between unicast and multicast?

16. what are the two multiplexing strategies used in transport layer?

17. Why transport layer extends host to delivery to process

18. State why telnet uses network virtual terminal?

19. What is the service provided by TCP?

Raghavendra Reddy Malapati Page 4

20. Difference between UDP and TCP.

PART-B

1. List and discuss the states used in TCP connection management finite state machine. i. Discuss how multiplexing and demultiplexing is done in the transport layer. (8) ii. Explain in detail the mechanism in transport layer for controlling congestion. (8)

2. i) Explain choke packets methods of congestion control. (8)

ii) Explain classless inter domain running(CINR). (8)

3. i) Explain various problem and corresponding solution in establishing a connection at transport layer. (8)

ii) Explain the connection release process applied at transport layer. (4)

iii) Explain window management in TCP. (4)

4. i) Discuss about quality of services. (8)

ii) Write short notes on integrated services. (8)


UNIT-V APPLICATION LAYER

PART-A ( 2 Marks)

1. Define authentication and name any two authentication protocols.

2. List any two types of DNS messages.

3. What is FTP?

4. State why telnet uses network virtual terminal ?

5. How does the user gets E-mail from the message transfer agent?

6. What is the importance of cookies?

7. State the goals behind ISDN?

8. What is telnet used for ? Discuss.

9. Define security in networking.

10. State Why telnet uses network virtual teriminal?

11. What are the elements of WWW?

12. What is the function provided by FTP?

13. Define SMTP?

14. What is the use of DNS?

15. Give example for hierarchy in DNS?

16. Compare plain text and cipher text?

17. what is symmetry key algorithm?

18. what are all the services provided my E-mail?

Raghavendra Reddy Malapati Page 5

19. Define HTML?

20. Define Fire walls?

PART-B

1.i) Explain in detail the File transfer protocol. (8)

ii) Describe Cryptography. (8)

2. i) Explain in detail a protocol for electronic mail. (8)

ii) Explain in detail Multimedia security. (8)

3. i) what is HTTP protocol used for? (6)

ii). What is the default port number of HTTP protocol? (5)

iii).Discuss the features of HTTP and also discuss how HTTP works.(5)

4. Explain the importance of communication security. (16)

5. Explain in detail the following i) Fault management. (8)

ii) security management. (8)

6.Explain in detail Authentication protocols

Raghavendra Reddy Malapati Page 6

EC2352-COMPUTER NETWORKS Questions Bank 2014


Anna University, Chennai

Anna_University,_Chennai_logo

SRINIVASAN ENGINEERING COLLEGE

PERAMBALUR

DEPARTMENT OF ELECCTRONICS AND COMMUNICATION ENGINEERING

EC2352-COMPUTER NETWORKS PREPARED BY: RAGHAVENDRA REDDY.MALAPATI

UNIT-I

PHYSICAL LAYER PART-A

1. What are the five important components of data communication?

2. List two advantages of layering principle in computer networks.

3. With the example explain half duplex communication.

4. Mention any two functions of session layer.

5. Name four topologies of computer networks.

6. Suggest two points to improve the performance of network.

7. With the example explain half duplex communication.

8. Define protocol.

9. Differentiate guided and unguided media.

10. What is the Null modem?

11. Define Topology.

12. Define standards.

13. What are the design factors for transmission media?

14. Difference between Guided media and un guided media.

15. Define line coding.

16. What are most popular modems?

17. Define network.

18. What are the criteria for networks for networks?

19. Define point to point and Multi point.

20. What is DSL

PART-B

1. Explain the OSI-ISO model I of computer with neat diagram. (16)

2. Distinguish between Point to Point links and multi-point links

Raghavendra Reddy Malapati Page 1

with relevant diagram. (16)

3. (i) compare connection oriented and connection less service. (8)

(ii) Differentiate Guided media and un guided media. (8)

4. Write shot notes on

a. TCP/IP protocol suite(4)

b. Networks Model(4)

c. datagram network(4)

d. Virtual circuit network(4)

5. Perform a comparative study between the ISO-OSI model and TCP/IP

reference model. (16)

6.Explain how cable TV used for data transfer?

7.Explain different switched networks

1. Define framing?

2. What is byte stuffing?


UNIT-II DATA LINK LAYER

PART-A ( 2Marks)

3. Write the importance of CRC in the network.

4. Sketch the Manchester encoding for the bit steam 0001110101.

5. Name the protocols used for CSMA

6. Wireless network and mobile networks are not identical explain

7. What is importance of hamming distance? What is Manchester Encoding?

8. What is mean by count to infinity problem?

9. What is Manchester Encoding?

10. What is the importance of variable sized sliding window in TCP?

11. Explain Aloha protocol.

12. Give the significance of termination.

13. What is IEEE 802.4 Standard?

14. Define Syndrome?

15. What are the various ARQ Retransmission strategies?

16. What is mediea sharing? State types of media sharing

17. State different IEEE 802 protocol.

18. Define throughput.

19. Define collision?

20. What is VLAN

21.Differentiate Wired LAN and Wireless LAN

22. What is Bluetooth?.

PART-B

Raghavendra Reddy Malapati Page 2

1. Write short notes on. a. GO Back NARQ (8)

b. Selective Repeat ARQ (8)

2. (i) ExplainProtocols for noiseless and Noisy channels. (8)

(ii) Explain numbering of frames in GO Back NARQ, Selective Repeat ARQ protocols. (8)

3. (i) Explain Ethernet protocol. (8)

(ii) Explain MAC sub layer protocol and frame structure of IEEE 802.11. (8)

4.Discuss in detail about standard ETHERNET

5. Discuss in detail about Gigabit Ethernet

6. (i) Explain any one of the protocols used for flow control in noisy channels. (8)

(ii) Write short note on architecture and layers of Frame relay and ATM

7. Explain in detail about connecting devices

1. What is subnetting?


UNIT-III NETWORK LAYER

PART-A (2 Marks)

2. What is the use of IP address?

3. State the difference between classless and classful addressing.

4. What is the difference between direct and indirect delivery.

5. What is the purpose of RIP.

6. what is the use of BGP.

7. What is the use of routing table.

8. Define Datagram.

9. Define Internet works?

10. What are the different type switching.

11. What is use the of Router?

12. What is the use of network layer?

13. What is MTU?

14. Define Fragmentation offset

15. Write the difference between bridge routers.

16. Find the error if any the following IP address. a. 111.56.045.78 b. 75.45.301.14

17. Where the routing table is maintained also state the purpose of maintaining a routing table.

18. What is datagram socket?

19. Write any four routing algorithm.

20. What is an IP address?

Raghavendra Reddy Malapati Page 3

PART-B

1. Find the class of each IP address given suitable explanation. (16)

a. 227.12.14.87 b.193.14.56.22 c. 14.23.120.8

d. 252.5.15.111 e. 134.11.78.56

f. 000 000 00 1111 0000 11111111 00110011 g. 10000000 1111 0000 11111111 00110011

2. What is BOOTP and explain.

3. State the major difference between Vector Routing and link state routing. (16)

4. Discuss ARP and RARP

5. What is the subnet work address if the destination address is 200.45.34.56 and the subnet mask is 255.255.240.0. (16)

6. What are the limitations of distance vector routing.

7. Explain Unicast and Multicast protocols. (16)

8.Explain the following DHCP,ICMP and IGMP


UNIT-IVTRANSPORT LAYER

PART-A ( 2 Marks)

1. What is the maximum case of UDP datagram?

2. What is the use of sequence numbers?

3. What is the source post numbers?

4. What is client process?

5. Name the policies that can precast congestion?

6. How are congestions control and quality of source hexapod?

7. What is the definition of burst data?

8. What is traffic shaping? Name two methods of shape traffic?

9. What determine the sender Window size in TCP

10. How is Resource Reservation Protocol related to integrated services

11. What is Traffic descriptor?

12. What is Access rate ?

13. What is the methods to improve Qos?

14. What is necessity of flow control

15. What is multicast? What is the difference between unicast and multicast?

16. what are the two multiplexing strategies used in transport layer?

17. Why transport layer extends host to delivery to process

18. State why telnet uses network virtual terminal?

19. What is the service provided by TCP?

Raghavendra Reddy Malapati Page 4

20. Difference between UDP and TCP.

PART-B

1. List and discuss the states used in TCP connection management finite state machine. i. Discuss how multiplexing and demultiplexing is done in the transport layer. (8) ii. Explain in detail the mechanism in transport layer for controlling congestion. (8)

2. i) Explain choke packets methods of congestion control. (8)

ii) Explain classless inter domain running(CINR). (8)

3. i) Explain various problem and corresponding solution in establishing a connection at transport layer. (8)

ii) Explain the connection release process applied at transport layer. (4)

iii) Explain window management in TCP. (4)

4. i) Discuss about quality of services. (8)

ii) Write short notes on integrated services. (8)


UNIT-V APPLICATION LAYER

PART-A ( 2 Marks)

1. Define authentication and name any two authentication protocols.

2. List any two types of DNS messages.

3. What is FTP?

4. State why telnet uses network virtual terminal ?

5. How does the user gets E-mail from the message transfer agent?

6. What is the importance of cookies?

7. State the goals behind ISDN?

8. What is telnet used for ? Discuss.

9. Define security in networking.

10. State Why telnet uses network virtual teriminal?

11. What are the elements of WWW?

12. What is the function provided by FTP?

13. Define SMTP?

14. What is the use of DNS?

15. Give example for hierarchy in DNS?

16. Compare plain text and cipher text?

17. what is symmetry key algorithm?

18. what are all the services provided my E-mail?

Raghavendra Reddy Malapati Page 5

19. Define HTML?

20. Define Fire walls?

PART-B

1.i) Explain in detail the File transfer protocol. (8)

ii) Describe Cryptography. (8)

2. i) Explain in detail a protocol for electronic mail. (8)

ii) Explain in detail Multimedia security. (8)

3. i) what is HTTP protocol used for? (6)

ii). What is the default port number of HTTP protocol? (5)

iii).Discuss the features of HTTP and also discuss how HTTP works.(5)

4. Explain the importance of communication security. (16)

5. Explain in detail the following i) Fault management. (8)

ii) security management. (8)

6.Explain in detail Authentication protocols

Raghavendra Reddy Malapati Page 6

EC2352-COMPUTER NETWORKS Two Marks Questions With Answers 2014


Anna University, Chennai

Anna_University,_Chennai_logo

SRINIVASAN ENGINEERING COLLEGE

PERAMBALUR

DEPARTMENT OF ELECCTRONICS AND COMMUNICATION ENGINEERING

EC2352-COMPUTER NETWORKS

PREPARED BY: RAGHAVENDRA REDDY.MALAPATI

COMPUTER NETWORKS QUESTION BANK WITH ANSWERS

December 3

2013

UNIT 1 PHYSICAL LAYER

1. What is mean by data communication?

Data communication is the exchange of data (in the form of 1s and 0s) between two devices via some form of transmission medium (such as a wire cable).

2. What are the three criteria necessary for an effective and efficient network?

The most important criteria are performance, reliability and security. Performance of the network depends on number of users, type of transmission medium, the capabilities of the connected h/w and the efficiency of the s/w. Reliability is measured by frequency of failure, the time it takes a link to recover from the failure and the network’s robustness in a catastrophe. Security issues include protecting data from unauthorized access and viruses.

3. What are the three fundamental characteristics determine the effectiveness of the data communication system?

The effectiveness of the data communication system depends on three fundamental

characteristics:

Delivery: The system must deliver data to the correct destination. Accuracy: The system must deliver data accurately.

Timeliness: The system must deliver data in a timely manner.

4. What are the advantages of distributed processing?

Advantages of distributed processing include security/encapsulation, distributed databases, faster problem solving, security through redundancy and collaborative processing.

5. Why are protocols needed?

In networks, communication occurs between the entities in different systems. Two entities cannot just send bit streams to each other and expect to be understood. For communication, the entities must agree on a protocol. A protocol is a set of rules that govern data communication

6. Why are standards needed?

Co-ordination across the nodes of a network is necessary for an efficient communication. If there are no standards, difficulties arise. A standard provides a model or basis for development to which everyone has agreed.

7. What is the difference between a passive and an active hub?

An active hub contains a repeater that regenerates the received bit patterns before sending them out. A passive hub provides a simple physical connection between the attached devices.

8. Distinguish between peer-to-peer relationship and a primary-secondary relationship.

Peer-to-peer relationship: All the devices share the link equally.

clip_image003Primary-secondary relationship: One device controls traffic and the others must transmit through it.

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clip_image001[2]9. Group the OSI layers by function.

The seven layers of the OSI model belonging to three subgroups. Physical, data link and network layers are the network support layers; they deal with the physical aspects of moving data from one device to another. Session, presentation and application layers are the user support layers; they allow interoperability among unrelated software systems. The transport layer ensures end-to-end reliable data transmission.

10. What are header and trailers and how do they get added and removed?

Each layer in the sending machine adds its own information to the message it receives from the layer just above it and passes the whole package to the layer just below it. This information is added in the form of headers or trailers. Headers are added to the message at the layers 6,5,4,3, and 2. A trailer is added at layer2. At the receiving machine, the headers or trailers attached to the data unit at the corresponding sending layers are removed, and actions appropriate to that layer are taken.

11. The transport layer creates a communication between the source and destination.

What are the three events involved in a connection?

Creating a connection involves three steps: connection establishment, data transfer and connection release.

12. How does NRZ-L differ from NRZ-I?

In the NRZ-L sequence, positive and negative voltages have specific meanings:

positive for 0 and negative for 1. in the NRZ-I sequence, the voltages are meaningless. Instead, the receiver looks for changes from one level to another as its basis for recognition of 1s.

13. What are the functions of a DTE? What are the functions of a DCE?

Data terminal equipment is a device that is an information source or an information sink. It is connected to a network through a DCE.

Data circuit-terminating equipment is a device used as an interface between a DTE

and a network.

14. What does the electrical specification of EIA-232 describe?

The electrical specification of EIA-232 defines that signals other than data must be sent using OFF as less than -3 volts and ON as greater than +3 volts. The data must be transmitted using NRZ-L encoding.

15. Discuss the mode for propagating light along optical channels

There are two modes for propagating light along optical channels, multimode and single mode.

Multimode: Multiple beams from a light source move through the core in different paths. Single mode: Fiber with extremely small diameter that limits beams to a few angles, resulting in an almost horizontal beam.

16. What is refraction?

The phenomenon related to the bending of light when it passes from one medium to another.

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17. What are the disadvantages of optical fiber as a transmission medium?

The disadvantages of optical fiber are

• Very expensive.

• Installation and maintenance is difficult.

• Fragility

18. What are the criteria used to evaluate transmission medium?

The criteria used to evaluate transmission medium are

• Throughput

• Propagation speed

• Propagation time

• Wavelength

19. Explain cross talk and what is needed to reduce it?

Effect of one wire on another is called as cross talk. One wire will be the sending antenna and the other wire will be the receiving antenna. We can use the shielded twisted pair cable or coaxial cable for transmission, which contains metal foil to reduce cross talk.


UNIT-II DATA LINK LAYER

1. What are the responsibilities of data link layer?

Specific responsibilities of data link layer include the following. a) Framing

b) Physical addressing c) Flow control

d) Error control

e) Access control

2. Mention the types of errors002E

There are 2 types of errors a) Single-bit error.

b) Burst-bit error.

3. Define the following terms.

a) Single bit error: The term single bit error means that only one bit of a given data unit

(such as byte character/data unit or packet) is changed from 1 to 0 or from 0 to 1.

b) Burst error:Means that 2 or more bits in the data unit have changed from 1 to 0 or from

0 to 1.

4. What is redundancy?

It is the error detecting mechanism, which means a shorter group of bits or extra bits may be appended at the destination of each unit.

5. List out the available detection methods.

There are 4 types of redundancy checks are used in data communication. a) Vertical redundancy checks (VRC).

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b) Longitudinal redundancy checks (LRC). c) Cyclic redundancy checks (CRC).

d) Checksum.

6. Write short notes on VRC.

The most common and least expensive mechanism for error detection is the vertical redundancy check (VRC) often called a parity check. In this technique a redundant bit called a parity bit, is appended to every data unit so, that the total number of 0’s in the unit (including the parity bit) becomes even.

7. Write short notes on LRC.

In longitudinal redundancy check (LRC), a block of bits is divided into rows and a redundant row of bits is added to the whole block.

8. Write short notes on CRC.

The third and most powerful of the redundancy checking techniques is the cyclic redundancy checks (CRC) CRC is based on binary division. Here a sequence of redundant bits, called the CRC remainder is appended to the end of data unit.

9. Write short notes on CRC generator.

A CRC generator uses a modulo-2 division.

a) In the first step, the 4 bit divisor is subtracted from the first 4 bit of the dividend.

b) Each bit of the divisor is subtracted from the corresponding bit of the dividend without disturbing the next higher bit.

10. Write short notes on CRC checker.

A CRC checker functions exactly like a generator. After receiving the data appended with the CRC it does the same modulo-2 division. If the remainder is all 0’s the CRC is dropped and the data accepted. Otherwise, the received stream of bits is discarded and the dates are resent.

11. What are the steps followed in checksum generator?

The sender follows these steps

a) The units are divided into k sections each of n bits.

b) All sections are added together using 2’s complement to get the sum. c) The sum is complemented and become the checksum.

d) The checksum is sent with the data.

12. List out the steps followed is checksum checker side.

The receiver must follow these steps

a) The unit is divided into k section each of n bits.

b) All sections are added together using 1’s complement to get the sum. c) The sum is complemented.

d) If the result is zero.

13. Write short notes on error correction.

It is the mechanism to correct the errors and it can be handled in 2 ways.

a) When an error is discovered, the receiver can have the sender retransmit the entire data

Raghavendra Reddy Malapati Page 5

unit.

b) A receiver can use an error correcting coder, which automatically corrects certain errors.

14. What is the purpose of hamming code?

A hamming code can be designed to correct burst errors of certain lengths. So the simple strategy used by the hamming code to correct single bit errors must be redesigned to be applicable for multiple bit correction.

15. Define flow control.

Flow control refers to a set of procedures used to restrict the amount of data. The sender can send before waiting for acknowledgment.

16. What is a buffer?

Each receiving device has a block of memory called a buffer, reserved for storing incoming data until they are processed.

17. Mention the categories of flow control.

There are 2 methods have been developed to control flow of data across communication links.

a) Stop and wait- send one from at a time.

b) Sliding window- send several frames at a time.

18. Define ARQ

Error control in the data link layer is based on Automatic repeat request (ARQ), which means retransmission of data in 3 cases.

a) Damaged frame b) Lost frame

c) Lost acknowledgment.

19. Mention the function of go-back N-ARQ.

It is the popular mechanism for continuous transmission error control. In this method, if our frame is lost or damaged, all frames sent since the last frame acknowledged are retransmitted.

20. What is selective reject ARQ?

In selective reject ARQ only the specific damaged or lost frame is retransmitted. If a frame is corrupted in transit, a NAK is returned and the frame is resent out of sequence.

21. List the various ways of station configuration.

The stations are configured in 3 ways a) Unbalanced configuration

b) Symmetrical configuration c) Balanced configuration

22. Mention the types of frames in HDLC.

There are 3 types of HDLC frames. a) Information frames (I-frames)

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b) Supervisory frames (S-frames)

c) Unnumbered frames (U-frames)

23. Give the usage of I, S, U frames.

I frames – used to transport user data and control information relating to user data.

S frames – used only to transport control information, primarily data link layer and error controls.

U frames – reserved for systems management.

24. Write the types of frame fields contained in HDLC

Each frame in HDLC may contain up to 6 fields. a) Beginning flag field

b) An address field c) A control field

d) An information field

e) A frame check sequence (FCS) field f) An ending flag field.

25. Define LAN.

A Local Area Network (LAN) is a data communication system that allows a number of independent devices to communicate directly with each other in a limited geographic area002E

26. Mention the various architecture in a LAN

LAN is dominated by 4 architectures. a) Ethernet

b) Token bus c) Token ring

d) Fiber distributed data interface (FDDI)

27. Define a standard 802.3

IEEE 802.3 supports a LAN standard originally developed by Xerox and later extended by a joint venture between digital equipment corporations. Intel Corporation and Xerox. This was called ‘Ethernet’.

28. Mention the different kinds of Ethernet networks.

a) Switched Ethernet b) Fast Ethernet

c) Gigabit Ethernet

29. Write short notes on FDDI.

Fiber distributed data interface is a local areas. Network protocol standardized by ANSI and ITU-7. It supports data rates of 100 Mbps and provides a high-speed alternative to Ethernet and token ring access method used here is token passing.

30. Describe the three HDLC station types?

The three HDLC station types are:

Primary station: The primary station has the complete control of the link. The Primary

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station sends commands to the secondary station. Secondary station: The secondary station sends responses.

Combined station: The combined station is one which acts either as a primary or a Secondary, depending upon the nature and direction of the transmission. Combined station sends both commands and responses

31. What is piggy backing?

Piggy backing means combining data to sent and acknowledgement of the frame received in one single frame. Piggy backing can save bandwidth because the overhead from a

data frame and an ACK frame can be combined into just one frame


UNIT III NETWORK LAYER

1. What are the network support layers and the user support layers?

Network support layers:

The network support layers are Physical layer, Data link layer and Network layer. These deals with electrical specifications, physical connection, transport timing and reliability.

User support layers:

The user support layers are: Session layer, Presentation layer, Application layer. These allow interoperability among unrelated software system.

2. What are the functions of LLC?

The IEEE project 802 model takes the structure of an HDLC frame and divides it into 2 sets of functions. One set contains the end user portion of the HDLC frame – the logical address, control information, and data. These functions are handled by the IEEE

802.2 logical link control (LLC) protocol.

3. What are the functions of MAC?

MAC sub layer resolves the contention for the shared media. It contains synchronization, flag, flow and error control specifications necessary to move information from one place to another, as well as the physical address of the next station to receive and route a packet.

4. What are headers and trailers and how do they get added and removed?

The control data added to the beginning of a data is called headers. The control data added to the end of a data is called trailers. At the sending machine, when the message passes through the layers each layer adds the headers or trailers. At the receiving machine, each layer removes the data meant for it and passes the rest to the next layer.

5. What are the responsibilities of network layer?

The network layer is responsible for the source-to-destination delivery of packet across multiple network links. The specific responsibilities of network layer include the following:

• Logical addressing.

• Routing.

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6. What is a virtual circuit?

A logical circuit made between the sending and receiving computers. The connection is made after both computers do handshaking. After the connection, all packets follow the same route and arrive in sequence.

7. What are data grams?

In datagram approach, each packet is treated independently from all others. Even when one packet represents just a place of a multipacket transmission, the network treats it although it existed alone. Packets in this technology are referred to as datagram.

8. What are the two types of implementation formats in virtual circuits?

Virtual circuit transmission is implemented in 2 formats.

• Switched virtual circuit

• Permanent virtual circuit

9. What is meant by switched virtual circuit?

Switched virtual circuit format is comparable conceptually to dial-up line in circuit switching. In this method, a virtual circuit is created whenever it is needed and exits only for the duration of specific exchange.

10. What is meant by Permanent virtual circuit?

Permanent virtual circuits are comparable to leased lines in circuit switching.In this method, the same virtual circuit is provided between two uses on a continuous basis. The circuit is dedicated to the specific uses.

11. Define Routers.

Routers relay packets among multiple interconnected networks. They Route packets from one network to any of a number of potential destination networks on internet routers operate in the physical, data link and network layer of OSI model.

12. What is meant by hop count?

The pathway requiring the smallest number of relays, it is called hop-count routing, in which every link is considered to be of equal length and given the value one.

13. What is time-to-live or packet lifetime?

As the time-to-live field is generated, each packet is marked with a lifetime; usually the number of hops that are allowed before a packet is considered lost and accordingly, destroyed. The time-to-live determines the lifetime of a packet.

14. What is meant by brouter?

A brouter is a single protocol or multiprotocol router that sometimes acts as a router and sometimes acts as a bridge.

15. Write the keys for understanding the distance vector routing.

The three keys for understanding the algorithm are

• Knowledge about the whole networks

• Routing only to neighbors

• Information sharing at regular intervals

16. How the packet cost referred in distance vector and link state routing?

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In distance vector routing, cost refer to hop count while in case of link state routing, cost is a weighted value based on a variety of factors such as security levels, traffic or the state of the link.

17. How the routers get the information about neighbor?

A router gets its information about its neighbors by periodically sending them short greeting packets. If the neighborhood responds to the greeting as expected, it is assumed to be alive and functioning. If it dose not, a change is assumed to have occurred and the sending router then alerts the rest of the network in its next LSP.

18. Define IP address.

IP address is the 3-bit number for representing a host or system in the network. One portion of the IP address indicates a networking and the other represents the host in a network.

19. What are the four internetworking devices?

The four internetworking devices are,

• Repeaters

• Bridges

• Routers

• Gateway

20. What is Token Bus?

Token Bus is a physical bus that operates as a logical ring using tokens. Here stations are logically organized into a ring. A token is passed among stations. If a station wants to send data, it must wait and capture the token. Like Ethernet, station communicates via a common bus.

21. What is token passing?

Stations may attempt to send data multiple times before a transmission makes it onto a link. This redundancy may create delays of indeterminable length if the traffic is heavy. Token ring resolves this uncertainty by requiring that stations take turns sending data. Each station may transmit only during its turn and may send only one frame during each turn. The mechanism that coordinates this rotation is called token passing.

22. What are the rules of boundary-level masking?

The rules of boundary-level masking

• The bytes in the IP address that corresponds to 255 in the mask will be repeated in the sub network address

• The bytes in the IP address that corresponds to 0 in the mask will change to 0 in the

sub network address

23. What are the rules of no boundary-level masking?

• The bytes in the IP address that corresponds to 255 in the mask will be repeated in the sub network address

• The bytes in the IP address that corresponds to 0 in the mask will change to 0 in the sub

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network address

• For other bytes, use the bit-wise AND operator

24. What is LSP?

In link state routing, a small packet containing routing information sent by a router to all other router by a packet called link state packet


UNIT IV TRANSPORT LAYER

1. What is function of transport layer?

The protocol in the transport layer takes care in the delivery of data from one application program on one device to an application program on another device. They act as a link between the upper layer protocols and the services provided by the lower layer.

2. What are the duties of the transport layer?

The services provided by the transport layer

End-to- end delivery

Addressing Reliable delivery Flow control Multiplexing

3. What is the difference between network layer delivery and the transport layer delivery?

Network layer delivery: The network layer is responsible for the source-to-destination

delivery of packet across multiple network links.

Transport layer delivery: The transport layer is responsible form source-to-destination delivery of the entire message.

4. What are the four aspects related to the reliable delivery of data?

The four aspects are, Error control Sequence control Loss control Duplication control

5. What is meant by segment?

At the sending and receiving end of the transmission, TCP divides long transmissions into smaller data units and packages each into a frame called a segment.

6. What is meant by segmentation?

When the size of the data unit received from the upper layer is too long for the network layer datagram or data link layer frame to handle, the transport protocol divides it into smaller usable blocks. The dividing process is called segmentation.

7. What is meant by Concatenation?

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The size of the data unit belonging to a single session are so small that several can fit together into a single datagram or frame, the transport protocol combines them into a single data unit. The combining process is called concatenation.

8. What are the techniques used in multiplexing?

The three basic techniques of multiplexing are, Frequency-division multiplexing

Time-division multiplexing

Wave-division multiplexing

9. What is meant by congestion?

Congestion in a network occurs if user sends data into the network at a rate greater than that allowed by network resources.

10. How will the congestion be avoided?

The congestion may be avoided by two bits

BECN - Backward Explicit Congestion Notification

FECN - Forward Explicit Congestion Notification

11. What is the function of BECN BIT?

The BECN bit warns the sender of congestion in network. The sender can respond to this warning by simply reducing the data rate.

12. What is the function of FECN?

The FECN bit is used to warn the receiver of congestion in the network. The sender and receiver are communicating with each other and are using some types of flow control at a higher level.

13. What is meant by quality of service?

The quality of service defines a set of attributes related to the performance of the connection. For each connection, the user can request a particular attribute each service class is associated with a set of attributes.

14. List out the user related attributes?

User related attributes are SCR – Sustainable Cell Rate PCR – Peak Cell Rate

MCR- Minimum Cell Rate

CVDT – Cell Variation Delay Tolerance

15. What are the networks related attributes?

The network related attributes are, Cell loss ratio (CLR)

Cell transfer delay (CTD) Cell delay variation (CDV) Cell error ratio (CER)

16. What is frame?

A frame consists of one complete cycle of time slots, including one or more slot dedicated to each sending device.

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17. What is framing bits?

One or more synchronization bits are usually added to the beginning of each frame. These bits are called framing bits.


UNIT – V APPLICATION LAYER

1. What is the purpose of Domain Name System?

Domain Name System can map a name to an address and conversely an address to name.

2. Discuss the three main division of the domain name space.

Domain name space is divided into three different sections: generic domains, country domains & inverse domain.

Generic domain: Define registered hosts according to their generic behavior, uses

generic suffixes.

Country domain: Uses two characters to identify a country as the last suffix.

Inverse domain: Finds the domain name given the IP address.

3. Discuss the TCP connections needed in FTP

FTP establishes two connections between the hosts. One connection is used for data transfer, the other for control information. The control connection uses very simple rules of communication. The data connection needs more complex rules due to the variety of data types transferred.

4. . Discuss the basic model of FTP.

The client has three components: the user interface, the client control process, and the client data transfer process. The server has two components: the server control process and the server data transfer process. The control connection is made between the control processes. The data connection is made between the data transfer processes.

5. What is the function of SMTP?

The TCP/IP protocol supports electronic mail on the Internet is called Simple Mail Transfer (SMTP). It is a system for sending messages to other computer users based on e- mail addresses. SMTP provides mail exchange between users on the same or different computers.

6. What is the difference between a user agent (UA) and a mail transfer agent (MTA)?

The UA prepares the message, creates the envelope, and puts the message in the envelope. The MTA transfers the mail across the Internet.

7. How does MIME enhance SMTP?

MIME is a supplementary protocol that allows non-ASCII data to be sent through SMTP. MIME transforms non-ASCII data at the sender site to NVT ASCII data and deliverers it to the client SMTP to be sent through the Internet. The server SMTP at the receiving side receives the NVT ASCII data and delivers it to MIME to be transformed back to the original data.

8. Why is an application such as POP needed for electronic messaging?

Workstations interact with the SMTP host which receives the mail on behalf of every

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host in the organization, to retrieve messages by using a client-server protocol such as Post Office Protocol , version 3(POP3). Although POP3 is used to download messages from the server, the SMTP client still needed on the desktop to forward messages from the workstation user to its SMTP mail server

9. Write down the three types of WWW documents.

The documents in the WWW can be grouped into three broad categories: static, dynamic and active.

Static: Fixed-content documents that are created and stored in a server. Dynamic: Created by web server whenever a browser requests the document. Active: A program to be run at the client side.

10. What is the purpose of HTML?

HTML is a computer language for specifying the contents and format of a web document. It allows additional text to include codes that define fonts, layouts, embedded graphics

and hypertext links.

11. Define CGI.

CGI is a standard for communication between HTTP servers and executable programs. It is used in crating dynamic documents.

12. Name four factors needed for a secure network.

Privacy: The sender and the receiver expect confidentiality.

Authentication: The receiver is sure of the sender’s identity and that an imposter has not sent the message.

Integrity: The data must arrive at the receiver exactly as it was sent.

Non-Reputation: The receiver must able to prove that a received message came from a specific sender.

13. . How is a secret key different from public key?

In secret key, the same key is used by both parties. The sender uses this key and an encryption algorithm to encrypt data; the receiver uses the same key and the corresponding decryption algorithm to decrypt the data. In public key, there are two keys: a private key and a public key. The private key is kept by the receiver. The public key is announced to the public.

14. What is a digital signature?

Digital signature is a method to authenticate the sender of a message. It is similar to that of signing transactions documents when you do business with a bank. In network transactions, you can create an equivalent of an electronic or digital signature by the way you send data.

15. What are the advantages & disadvantages of public key encryption?

Advantages:

a). Remove the restriction of a shared secret key between two entities. Here each entity can create a pair of keys, keep the private one, and publicly distribute the other one.

b) The no. of keys needed is reduced tremendously. For one million users to communicate, only two million keys are needed.

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Disadvantage:

If you use large numbers the method to be effective. Calculating the cipher text using the long keys takes a lot of time. So it is not recommended for large amounts of text.

16. What are the advantages & disadvantages of secret key encryption?

Advantage:

Secret Key algorithms are efficient: it takes less time to encrypt a message. The reason is that the key is usually smaller. So it is used to encrypt or decrypt long messages. Disadvantages:

a) Each pair of users must have a secret key. If N people in world want to use this

method, there needs to be N (N-1)/2 secret keys. For one million people to communicate, a half-billion secret keys are needed.

b) The distribution of the keys between two parties can be difficult.

17. Define permutation.

Permutation is transposition in bit level.

Straight permutation: The no. of bits in the input and output are preserved. Compressed permutation: The no. of bits is reduced (some of the bits are dropped). Expanded permutation: The no. of bits is increased (some bits are repeated).

18. Define substitutional & transpositional encryption.

Substitutional: A character level encryption in which each character is replaced by another character in the set.

Transpositional: A Character level encryption in which the characters retain their

clip_image007[2]plaintext but the position of the character changes

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EC2254 - LINEAR INTEGRATED CIRCUITS Two Mark Questions With Answers 2014


Anna University, Chennai

Anna_University,_Chennai_logo

 (IC FABRICATION AND CIRCUIT CONFIGURATION FOR LINEAR ICs)

(TWO MARKS QUESTION AND ANSWERS)

1. Define an Integrated circuit.

An integrated circuit(IC) is a miniature ,low cost electronic circuit consisting of active

and passive components fabricated together on a single crystal of silicon.The active components

are transistors and diodes and passive components are resistors and capacitors.

2. Mention the advantages of integrated circuits over discrete

components. (May 2010)

*Miniaturisation and hence increased equipment density.

*Cost reduction due to batch processing.

*Increased system reliability due to the elimination of soldered

joints.

*Improved functional performance.

*Matched devices. *Increased operating

speeds.

*Reduction in power consumption.

3. Define sheet resistance.(may 2010)

Sheet resistance is defined as the resistance in ohms /square offered by

the diffused area.

4. What is the use of buried n+ layer in monolithic IC transistor?(MAY

2010)

The buried n+ layer provides a low resistance path in the active collector

region for the flow of current

5. What are the two common methods for obtaining integrated capacitors?

(may 2010)

• Monolithic junction capacitor

• Thin-flim capacitor

6.What are the basic processes involved in fabricating ICs using planar

technology?

1.Silicon wafer (substrate) preparation

2.Epitaxial growth

3.Oxidation

4.Photolithography

5.Diffusion

6.Ion implantation

7.Isolation technique

8.Metallization

9.Assembly processing & packaging

7. What is active load? Where it is used and why? (MAY/JUNE 2010 )

The active load realized using current source in place of the passive load in the collector

arm of differencial amplifier makes it possible to achieve high voltage gain without requiring large power supply voltage.

8. Why open loop OP-AMP configurations are not used in linear

applications?(may/june 2010)

The open loop gain of the op-amp is not a constant and it varies with changing the

temperature and variations in power supply.Also the bandwidth of the open loop op-amp is

negligibly small.For this reasons open loop OP-AMP configurations are not used in linear

applications.

9. Define virtual ground of a OP-Amp? (may/june 2010)

A virtual ground is a ground which acts like a ground. It is a point that is at the fixed ground potential (0v),though it is not practically connected to the actual ground or common

terminal of the circuit.

10.List out the steps used in the preparation of Si - wafers.

1.Crystal growth &doping

2.Ingot trimming & grinding

3.Ingot slicing

4.Wafer policing & etching

5.Wafer cleaning

11. Write the basic chemical reaction in the epitaxial growth process of pure

silicon.

The basic chemical reaction in the epitaxial growth process of pure silicon is the

hydrogen reduction of silicon tetrachloride.

1200C SiCl4 + 2H2 <> Si + 4 HCl

12. What are the two important properties of SiO2?

1.SiO2 is an extremely hard protective coatng & is unaffected by almost all reagents except by hydrochloric acid. Thus it stands against any contamination.

2.By selective etching of SiO2 , diffusion of impurities through carefully defined

windows in the SiO2 can be accomplished to fabricate various components.

13. Explain the process of oxidation.

The silicon wafers are stacked up in a quartz boat & then inserted into quartz furnace

tube. The Si wafers are raised to a high temperature in the range of 950 to 1150oC & at the same

time, exposed to a gas containing O2 or H2O or both.The chemical action is

Si + 2H2O > Si O2+ 2H2

14. What is meant by molecular beam epitaxy(MBE)?

In the molecular beam epitaxy, ilicon along with dopants is evaporated.The evaporated species are transported at a relatively high velocity in a vacuum to the substrate.The relatively

low vapour pressure of silicon & the dopants ensures condensation on a low temperature

substrate.Usually, silicon MBE is performed under ultra high vacuum (UHV) condition of 10-8

to 10-10 Torr

15. What are the advantages and limitations implantation of ion

implantation?

Advantages:

• Accurate control over doping

• Very good reproducibility

• Precise resistance value

• A room temperature process

Limitations:

• Annealing at higher temperature is required for avoiding the crystal

damage

• The possibility of dopant implanting through various layers wafer.

16.Define input offset voltage.

A small voltage applied to the input terminals to make the output voltage as zero when

the two input terminals are grounded is called input offset voltage.

17. Define input offset current. State the reasons for the offset currents at the input of the op-amp.

The difference between the bias currents at the input terminals of the op-amp is called as

input offset current. The input terminals conduct a small value of dc current to bias the input

transistors.Since the input transistors cannot be made identical,there exists a difference in bias

currents.

18. Define CMRR of an op-amp.(DEC 09)

The relative sensitivity of an op-amp to a difference signal as compared to a common -

mode signal is called the common -mode rejection ratio. It is expressed in decibels.

CMRR= Ad/Ac

19.What are the applications of current sources?

Transistor current sources are widely used in analog ICs both as biasing elements and as

load devices for amplifier stages.

20. Justify the reasons for using current sources in integrated circuits.

(i) Superior insensitivity of circuit performance to power supply variations and

temperature.

(ii) More economical than resistors in terms of die area required to provide bias

currents of small value.

(iii) When used as load element, the high incremental resistance of current source

results in high voltage gain at low supply voltages.

21. What is the advantage of widlar current source over constant current

source?

Using constant current source output current of small magnitude(microamp range) is not

attainable due to the limitations in chip area. Widlar current source is useful for obtaining small

output currents.Sensitivity of widlar current source is less compared to constant current source.

22.Mention the advantages of Wilson current source.

(i) Provides high output resistance.

(ii) Offers low sensitivity to transistor base currents

23.Define sensitivity.

Sensitivity is defined as the percentage or fractional change in output current per percentage or fractional change in power-supply voltage.

24.What are the limitations in a temperature compensated zener-reference source?

A power supply voltage of atleast 7 to 10 V is required to place the diode in the

breakdown region and that substantial noise is introduced in the circuit by the avalanching diode.

25.In practical op-amps, what is the effect of high frequency on its performance?

The open-loop gain of op-amp decreases at higher frequencies due to the presence of

parasitic capacitance. The closed-loop gain increases at higher frequencies and leads toinstability.

26. What is the need for frequency compensation in practical op-amps?

Frequency compensation is needed when large bandwidth and lower closed loop gain is

desired. Compensating networks are used to control the phase shift and hence to improve the stability.

27.Define slew rate.(MAY 2010)

The slew rate is defined as the maximum rate of change of output Voltage caused by a

step input voltage.An ideal slew rate is infinite which means that op-amp's output voltage should

change instantaneously in response to input step voltage.

28.Why IC 741 is not used for high frequency applications?

IC741 has a low slew rate because of the predominance of capacitance present in the

circuit at higher frequencies. As frequency increases the output gets distorted due to limited slew rate.

29. What causes slew rate?(DEC 09)

There is a capacitor with-in or outside of an op-amp to prevent oscillation. The capacitor

which prevents the output voltage from responding immediately to a fast changing input.

30. What happens when the common terminal of V+ and V- sources is not

grounded? (DEC 09)

If the common point of the two supplies is not grounded, twice the supply voltage will

get applied and it may damage the op-amp.


UNIT- II

APPLICATION OF OPERATIONAL AMPLIFIERS

1. Mention some of the linear applications of op - amps. (DEC 09)

Adder, subtractor, voltage -to- current converter, current -to- voltage converters,

instrumentation amplifier, analog computation ,power amplifier, etc are some of the linear op- amp circuits.

2. Mention some of the non - linear applications of op-amps:-

Rectifier, peak detector, clipper, clamper, sample and hold circuit, log amplifier, anti -

log amplifier, multiplier are some of the non - linear op-amp circuits.

3.What are the areas of application of non-linear op- amp circuits?

1. Industrial instrumentation

2. Communication

3. Signal processing

4. What is voltage follower?(MAY 2010)

A circuit in which output folloes the input is called voltage follower.

5. What is the need for an instrumentation amplifier?

In a number of industrial and consumer applications, the measurement of physical quantities is usually done with the help of transducers. The output of transducer has to be

amplified So that it can drive the indicator or display system. This function is performed by an

instrumentation amplifier.

6. List the features of instrumentation amplifier:

1.High gain accuracy

2.High CMRR

3.High gain stability with low temperature co-efficient

4Low dc offset

5.Low output impedance

7. What are the applications of V-I converter?

₃ 1.Low voltage dc and ac voltmeter

2.L E D

3.Zener diode tester

8. Define Bandpass filter. (MAY 2010)

The bandpass filter is the combination of high and low pass filters, and this allows a specified range of frequencies to pass through.

9. Write transfer function of op amp as an integer. (MAY 2010)

The transfer function of the integer is

ôAô=1/wR1cf

10. What do you mean by a precision diode?

The major limitation of ordinary diode is that it cannot rectify voltages below the cut - in

voltage of the diode. A circuit designed by placing a diode in the feedback loop of an op - amp

is called the precision diode and it is capable of rectifying input signals of the order of millivolt.

11. Write down the applications of precision diode.

1.Half - wave rectifier

2.Full - Wave rectifier

3.Peak - value detector

4.Clipper

5.Clamper

12. Define Logarithmic and antilogarithmic amplifier. (MAY 2010)

When a logarithmic PN junction is used in the feedback network of op-amp, the circuit

exhibits log or antilog response.

The logarithmic amplifier is a current to voltage converter with the

transfer characteristics v0=vi In(If/Ii)

Antilog amplifier is a decoding circuit which converts the logarithmically encoded

signal back to the original signal levels as given by vl=vR10-kvi

13. Differentiate Schmitt trigger and comparator. (MAY 2010)

comparator.

1. It compares the input signal with

references voltage then yields the

output voltage

2. It need not consist of feedback

3. comparator output need not to be

square wave

14. List the applications of Log amplifiers:

Schmitt trigger

1. It operates between two reference

points namely UTP&LTP.

2. It employs positive feedback

3. Its output is square wave.

1.Analog computation may require functions such as lnx, log x, sin hx etc. These

functions can be performed by log amplifiers

2.Log amplifier can perform direct dB display on digital voltmeter and spectrum analyzer

3.Log amplifier can be used to compress the dynamic range of a signal

15. What are the limitations of the basic differentiator circuit?

1.At high frequency, a differentiator may become unstable and break into oscillations

2,The input impedance decreases with increase in frequency , thereby making the

circuit sensitive to high frequency noise.

16. Write down the condition for good differentiation .

1.For good differentiation, the time period of the input signal must be greater than or

equal to Rf C1

2.T > R f C1 Where, Rf is the feedback resistance

3.Cf is the input capacitance

17. What is a comparator?(MAY 2010)

A comparator is a circuit which compares a signal voltage applied at one input of an op-

amp with a known reference voltage at the other input. It is an open loop op - amp with output +

Vsat .

18. What are the applications of comparator?

1.Zero crossing detector

2.Window detector

3.Time marker generator

4.Phase detector

19. What is a Schmitt trigger?(DEC 09,MAY 10)

Schmitt trigger is a regenerative comparator. It converts sinusoidal input into a square

wave output. The output of Schmitt trigger swings between upper and lower threshold voltages,

which are the reference voltages of the input waveform.

20. What is a multivibrator?

Multivibrators are a group of regenerative circuits that are used extensively in timing

applications. It is a wave shaping circuit which gives symmetric or asymmetric square output. It

has two states either stable or quasi- stable depending on the type of multivibrator.

21. What do you mean by monostable multivibrator?

Monostable multivibrator is one which generates a single pulse of specified

duration in response to each external trigger signal. It has only one stable state.

Application of a trigger causes a change to the quasi-stable state.An external trigger signal

generated due to charging and discharging of the capacitor produces the transition to the original stable state

22. What is an astable multivibrator?

Astable multivibrator is a free running oscillator having two quasi-stable states. Thus,

there is oscillations between these two states and no external signal are required to produce the change in state.

23. What is a bistable multivibrator?

Bistable multivibrator is one that maintains a given output voltage level unless an

external trigger is applied . Application of an external trigger signal causes a change of state,

and this output level is maintained indefinitely until an second trigger is applied . Thus, it

requires two external

triggers before it returns to its initial state

24. Mention any two audio frequency oscillators.

i. RC phase shift oscillator

ii. Wein bridge oscillator

25. What are the characteristics of a comparator?

1.Speed of operation

2.Accuracy

3.Compatibility of the output

26. What is a filter?

Filter is a frequency selective circuit that passes signal of specified band of frequencies

and attenuates the signals of frequencies outside the band

27. What are the demerits of passive filters?

Passive filters works well for high frequencies. But at audio frequencies, the inductors

become problematic, as they become large, heavy and expensive.For low frequency applications,

more number of turns of wire must be used which in turn adds to the series resistance degrading

inductor's performance ie, low Q, resulting in high power dissipation.

28. What are the advantages of active filters?

Active filters used op- amp as the active element and resistors and capacitors as passive

elements.

29. Define low pass filter.

A low pass filter allows only low frequency signals upto a certain break point fH to pass

through.

30. Define High pass filter.

A low pass filter allows only high frequency signals upto a certain break point fH to pass

through


UNIT- III

ANOLOG MULTIPLIER AND PLL

1. List the basic building blocks of PLL:

1.Phase detector/comparator

2.Low pass filter

3.Error amplifier

4.Voltage controlled oscillator

2. Define FSK modulation.(MAY 2010)

FSK is a type of frequency modulation ,in which the binary data or code is

transmitted by means of a carrier frequency that is shifted between two fixed

frequency namely mark(logic1) and space frequency(logic 0).

3. What is analog multiplier?(MAY 2010)

A multiplier produces an output v0, which is proportional to the product of two inputs vx

and vy

V0= kvxvy

4. List out the various methods available for performing for analog multiplier.

• Logarithmic summing technique

• Pulse height /width modulation technique

• Variable transconductance technique

• Multiplication using gilbert cell

• Multiplication technique using transconductance technique

5. Mention some areas where PLL is widely used. (DEC 2009)

1.Radar synchronizations

2. Satellite communication systems

3. Air borne navigational systems

4. FM communication systems

5.Computers.

6. What are the three stages through which PLL operates?

1.Free running

2.Capture

3.Locked/ tracking

7. Define lock-in range of a PLL. (MAY 2010)

The range of frequencies over which the PLL can maintain lock with the incoming signal

is called the lock-in range or tracking range. It is expressed as a percentage of theVCO free running frequency.

8. Define capture range of PLL. (MAY 2010)

The range of frequencies over which the PLL can acquire lock with an input signal is

called the capture range. It is expressed as a percentage of the VCO free

running frequency.

9.Define Pull-in time.

The total time taken by the PLL to establish lok is called pull-in time.It depends on the

initial phase and frequency difference between the two signals as well as on the overall loop

gain and loop filter characteristics

10. Write the expression for FSK modulation.(MAY 2010)

∆vf=f2-f1/k0

11. Define free running mode .(MAY 2010)

An interactive computer mode that allows more than one user to have

simultaneous use of a program.

12. For perfect lock, what should be the phase relation between the incoming signal

and VCO output signal?

The VCO output should be 90 degrees out of phase with respect to the input

signal.

13.Give the classification of phase detector:

1.Analog phase detector .

2.Digital phase detector

14.What is a switch type phase detector?

An electronic switch is opened and closed by signal coming from VCO and the input

signal is chopped at a repetition rate determined by the VCO frequency.This type of phase

detector is called a half wave detector since the phase information for only one half of the input

signal is detected and averaged.

15.What are the problems associated with switch type phase detector?

1.The output voltage Ve is proportional to the input signal amplitude.This is undesirable

because it makes phase detector gain and loop gain dependent on the input signal amplitude.

2.The output is proportional to cosf making it non linear.

16.What is a voltage controlled oscillator?

Voltage controlled oscillator is a free running multivibrator operating at a set frequency

called the free running frequency.This frequency can be shifted to either side by applying a dc

control voltage and the frequency deviation is proportional to the dc control voltage.

17. Define Voltage to Frequency conversion factor.

Voltage to Frequency conversion factor is defined as,

Kv = fo / Vc= 8fo /Vcc

Vc is the modulation voltage

fo frequency shift

18.What is the purpose of having a low pass filter in PLL?

*It removes the high frequency components and noise.

*Controls the dynamic characteristics of the PLL such as capture range,

lock-in range,band-width and transient response.

*The charge on the filter capacitor gives a short- time memory to the PLL

19.Discuss the effect of having large capture range.

The PLL cannot acquire a signal outside the capture range, but once captured, it

will hold on till the frequency goes beyond the lock-in range.Thus , to increase the ability

of lock range,large capture range is required.But, a large capture range will make the PLL more

susceptible to noise and undesirable signal.

20.Mention some typical applications of PLL:

• Frequency multiplication/division

• Frequency translation

• AM detection

• FM demodulation

• FSK demodulation.

21.What is a compander IC? Give some examples.(DEC 2009)

The term companding means compressing and expanding.In a communication system, the audio signal is compressed in the transmitter and expanded in the receiver. Examples : LM 2704- LM 2707 ; NE 570/571.

22.What are the merits of companding?

*The compression process reduces the dynamic range of the signal before it

is transmitted.

*Companding preserves the signal to noise ratio of the original signal and avoids

non linear distortion of the signal when the input amplitude is large.

*It also reduces buzz,bias and low level audio tones caused by mild interference

2252– Communication Theory Two Marks Questions With Answers 2014


Anna University, Chennai

Anna_University,_Chennai_logo

SRINIVASN ENGINEERING COLLEGE, PERAMBALUR.

DEPARTMENT OF ECE

2 MARKS QUESTION &ANSWERS EC 2252– Communication Theory

Prepared by :ARIVASANTH.M ,AP/ECE C.SATHISHKUMAR, AP/ECE

TWO MARKS QUESTIONS

1. Define modulation?

Modulation is a process by which some characteristics of high frequency carrier signal is varied in accordance with the instantaneous value of the modulating signal.

2.What are the types of analog modulation?

Amplitude modulation. Angle Modulation

1. Frequency modulation

2. Phase modulation.

3.Define depth of modulation.

It is defined as the ratio between message amplitude to that of carrier amplitude. m=Em/Ec

4. What are the degrees of modulation?

Under modulation. m<1

Critical modulation m=1

Over modulation m>1

5.What is the need for modulation?

Needs for modulation:

Ease of transmission Multiplexing Reduced noise Narrow bandwidth

Frequency assignment

Reduce the equipments limitations.

6.What are the types of AM modulators?

There are two types of AM modulators. They are

Linear modulators

Non-linear modulators

Linear modulators are classified as follows

Transistor modulator

There are three types of transistor modulator.

Collector modulator Emitter modulator Base modulator

Switching modulators

Non-linear modulators are classified as follows

Square law modulator Product modulator Balanced modulator

7.Give the classification of modulation.

There are two types of modulation. They are

Analog modulation

Digital modulation

Analog modulation is classified as follows

Continuous wave modulation

Pulse modulation

Continuous wave modulation is classified as follows

Amplitude modulation

Double side band suppressed carrier Single side band suppressed carrier Vestigial side band suppressed carrier

Angle modulation

Frequency modulation

Phase modulation

Pulse modulation is classified as follows

Pulse amplitude modulation Pulse position modulation Pulse duration modulation Pulse code modulation

Digital modulation is classified as follows Amplitude shift keying Phase shift keying Frequency shift keying

8.What is single tone and multi tone modulation?

If modulation is performed for a message signal with more than one frequency component then the modulation is called multi tone modulation.

If modulation is performed for a message signal with one frequency component then the modulation is called single tone modulation.

9 .The antenna current of an AM transmitter is 8A when only carrier is sent. It increases to 8.93A when the carrier is modulated by a single sine wave. Find the percentage modulation.

Solution:

Given: Ic =8A It=8.93A m=0.8

Formula: It=Ic (1+m2/2) ½

8.93=8(1+m2/2) ½

m=0.701

It=8 (1+0.82/2) ½

It=9.1A

10.Compare AM with DSB-SC and SSB-SC.

AM signal

DSB-SC

SSB-SC

Bandwidth=2fm

Bandwidth=2fm

Bandwidth=fm

Contains USB, LSB, carrier

Contains USB,LSB

Contains LSB or USB

More power is required for

Transmission

Power required is less than

that of AM.

Power required is less than

AM &DSB-SC

11 What are the advantages of VSB-AM?

1.It has bandwidth greater than SSB but less than DSB system.

2.Power transmission greater than DSB but less than SSB system.

3.No low frequency component lost. Hence it avoids phase distortion.

12 Compare linear and non-linear modulators.

Linear modulators Non-linear modulators

1.Heavy filtering is not 1.Heavy filtering is required required.

2.These modulators are used in 2.These modulators are used in low level high level modulation. Modulation.

3.The carrier voltage is very much 3.The modulating signal voltage is very much greater than modulating signal greater than the carrier signal voltage. voltage.

13.How will you generating DSBSC-AM ?

There are two ways of generating DSBSC-AM such as

1.balanced modulator 2.ring modulators

14. What are advantages of ring modulator?

1.Its output is stable.

2. It requires no external power source to activate the diodes.

3.Virtually no maintenance.

4. Long life.

15. Define demodulation.

Demodulation or detection is the process by which modulating voltage is recovered from the modulated signal. It is the reverse process of modulation.

16. What are the types of AM detectors?

1. Nonlinear detectors

2. Linear detectors

17.What are the types of linear detectors?

1.Synchronous or coherent detector.

2 .Envelope or non coherent detector.

18. Draw the block diagram of coherent detector.

modulated signal

Product

modulator LPF

OUTPUT

Carrier

Signal

19.Define multiplexing.

Multiplexing is defined as the process of transmitting several message signals simultaneously over a single channel.

20.Define sensitivity.

It is defined as a measure of its ability to receive weak signals.

21.Define selectivity.

Selectivity of a receiver is defined as its ability to select the desired signals among the various signals.

22. Define stability.

It is the ability of the receiver to deliver a constant amount of output for a given a given period of time.

23.Define super heterodyne principle.

It can be defined as the process of operation of modulated waves to obtain similarly modulated waves of different frequency. This process uses a locally generated carrier wave, which determines the change of frequency.

24.A transmitter supplies 8 Kw to the antenna when modulated. Determine the total power radiated when modulated to 30%.

m=0.3;Pc=8 kw

Pt=Pc(1+m2/2)

=8.36 kw

25.What are the drawbacks of emitter modulator?

1.The amplifier is operated in class A mode, thus the efficiency is low.

2.The output power is very small. Thus it is not suitable for generating high level modulation.

26. Define frequency modulation.

Frequency modulation is defined as the process by which the frequency of the carrier wave is varied in accordance with the instantaneous amplitude of the modulating or message signal.

27. Define modulation index of frequency modulation.

It is defined as the ratio of maximum frequency deviation to the modulating frequency. β = δf/fm

28. What do you meant by multitone modulation?

Modulation done for the message signal with more than one frequency component is called multitone modulation.

29. Define phase modulation.

Phase modulation is defined as the process of changing the phase of the carrier signal in accordance with the instantaneous amplitude of the message signal.

30. How FM wave can be converted to PM wave? Message signal Differentiator FM

Carrier

31. How PM wave can be converted to FM wave?

Message Signal Integrator Phase

Modulator

Carrier

FM Signal

32. What are the types of Frequency Modulation?

Based on the modulation index FM can be divided into types. They are Narrow band FM and Wide band FM. If the modulation index is greater than one then it is wide band FM and if the modulation index is less than one then it is Narrow

band FM

33. What is the basic difference between an AM signal and a narrowband FM signal?

In the case of sinusoidal modulation, the basic difference between an AM signal and a narrowband FM signal is that the algebraic sign of the lower side frequency in the narrow band FM is reversed.

34. What are the two methods of producing an FM wave?

Basically there are two methods of producing an FM wave. They are, i) Direct method

In this method the transmitter originates a wave whose frequency varies as function of the modulating source. It is used for the generation of NBFM

ii) Indirect method

In this method the transmitter originates a wave whose phase is a function of the modulation. Normally it is used for the generation of WBFM where WBFM is generated from NBFM

35 . Compare WBFM and NBFM.

WBFM NBFM

Modulation index is greater than 1 Modulation index less than 1

Frequency deviation 75 KHz Frequency deviation 5 KHz

Bandwidth 15 times NBFM Bandwidth 2fm

Noise is more suppressed Less suppressing of noise

36. List the properties of the Bessel function.

The properties of the Bessel function is given by,

i) Jn (β)=(-1)nJ-n(β) for all n, both positive and negative. ii) For small values of the modulation index β ,we have

J0 (β)=1

J1 (β)=β/2

Jn(β)=0,n>2.

2

iii) Σ J n

(β)=1n = -∞

37. Give the average power of an FM signal.

The amplitude of the frequency modulated signal is constant .The power of the

FM signal is same as that of the carrier power. P=1/2 Ec2 .

38. Define phase deviation.

The maximum phase deviation of the total angle from the carrier angle is called phase deviation.

39. Define frequency Deviation.

The maximum departure of the instantaneous frequency from the carrier frequency is called frequency deviation.

40. State the Carson’s rule.

An approximate rule for the transmission bandwidth of an FM Signal generated by a single tone-modulating signal of frequency fm is defined as

B =2 ∆f(1+1/ β)

41.Define the deviation ratio D for non-sinusoidal modulation.

The deviation ratio D is defined as the ratio of the frequency deviation ∆f, which corresponds to the maximum possible amplitude of the modulation signal m(t),to the

highest modulation frequency .

D = ∆f / fm

42.What is the use of crystal controlled oscillator?

The crystal-controlled oscillator always produces a constant carrier frequency there by enhancing frequency stability.

43. What are the disadvantages of FM system?

1. A much wider channel is required by FM.

2. FM transmitting and receiving equipments tend to be more complex and hence it is expensive

44. How will you generate message from frequency-modulated signals?

First the frequency-modulated signals are converted into corresponding amplitude-modulated signal using frequency dependent circuits. Then the original signal is recovered from this AM signal.

45. What are the types of FM detectors?

Slope detector and phase discriminator.

46. What are the types of phase discriminator?

Foster seely discriminator and ratio detector.

47. What are the disadvantages of balanced slope detector?

1. Amplitude limiting cannot be provided

2. Linearity is not sufficient

3. It is difficult to align because of three different frequency to which various tuned circuits to be tuned.

4. The tuned circuit is not purely band limited.

48. Define probability.

The probability of occurrence of an event A is defined as,

P(A)= number of possible favorable outcomes

Total number of equal likely outcomes

49.What are mutually exclusive events?

Two possible outcomes of an experiment are defined as being mutually exclusive if the occurrence of one outcome precludes the occurrence of the other.

50. Define probability density function.

Probability density function is defined as fx(x) is defined in terms of cumulative distribution function Fx (x) as

fx(x) = d Fx (x)

dx

51. Define noise.

Noise is defined as any unwanted form of energy, which tends to interfere with proper reception and reproduction of wanted signal.

52. Give the classification of noise.

Noise is broadly classified into two types. They are External noise and internal

noise.

53. What are the types of External noise?

External noise can be classified into

1. Atmospheric noise

2. Extraterrestrial noises

3. Man –made noises or industrial noises

54. What are types of internal noise?Internal noise can be classified into

1. Thermal noise

2. Shot noise

3. Transit time noise

4. Miscellaneous internal noise

55. What are the types of extraterrestrial noise and write their origin?

The two type of extraterrestrial noise are solar noise and cosmic noise

Solar noise is the electrical noise emanating from the sun.

Cosmic noise is the noise received from the center part of our galaxy, other distant galaxies and other virtual point sources.

56. Define transit time of a transistor.

Transit time is defined as the time taken by the electron to travel from emitter to the collector.

57. Define flicker noise.

Flicker noise is the one appearing in transistors operating at low audio frequencies. Flicker noise is proportional to the emitter current and junction temperature and inversely proportional to the frequency.

58. State the reasons for higher noise in mixers.

1. Conversion transconductance of mixers is much lower than the transconductance of amplifiers.

2. If image frequency rejection is inadequate, the noise associated with the image frequency also gets accepted.

59. Define signal to noise ratio.

Signal to noise ratio is the ratio of signal power to the noise power at the same point in a system.

60. Define noise figure.

Nose figure F = S/ N at the input/ S/ N at the output

S/N = Signal power / Noise Power

61. Explain thermal noise.

Thermal noise is the name given to the electrical noise arising from the random motion of electrons in a conductor.

62. Give the expression for noise voltage in a resistor.

The mean –square value of thermal noise voltage is given by

Vn2 = 4 K T B R

K – Boltz man constant

R – resistance

T – obsolute temperature

B - Bandwidth

63. Explain White Noise.

Many types of noise sources are Gaussian and have flat spectral density over a wide frequency range. Such spectrum has all frequency components in equal portion, and is therefore called white noise. The power spectral density of white noise is independent of the operating frequency.

64. What is narrowband noise?

The receiver of a communication system usually includes some provision for preprocessing the received signal. The preprocessing may take the form of a narrowband filter whose bandwidth is large enough to pass modulated component of the receivedsignal essentially undistorted but not so large as to admit excessive noise

through the receiver. The noise process appearing at the output of such filter is called narrow band noise.

65. Give the representation of narrowband noise in terms of envelope and phase components.

Narrowband noise in terms of envelope and phase components as n(t) = r(t) cos (2πfct + Φ (t) )

r(t) = (nI 2(t) + nQ 2(t))½

Φ (t) = tan -1(nQ(t) / nI (t ))

The function r (t) and Φ (t) are called envelope and phase of n(t).

66. Give the expression for equivalent noise temperature in terms of hypothetical temperature.

The expression for equivalent noise temperature in terms of hypothetical

temperature

is Te = ( F- 1) T0

Where, F is the noise figure and T0 absolute temperature.

67. Give the Friss formula in terms of noise temperature.

The Friss formula in terms of noise temperature is

Te = T1 + T2 / G1 + T3 / G1 G2 + ………

G1 , G2 ,… Gain of amplifiers

68. What is called image frequency?

Image frequency is defined as the signal frequency plus twice the intermediate frequency. This has the effect of two stations being received simultaneously and hence it is undesirable.

fsi = fs + 2 fi

fsi - image frequency

It can be eliminated by providing adequate image signal selectivity between antenna and mixer input.

69. What is intermediate frequency?

Intermediate frequency (IF) is defined as the difference between the signal frequency and the oscillator frequency.

IF = fs – fo

when fs > fo

(or)

IF = fo –fs

when fo > fs

 

70. Define Partition noise.

In an electron tube having one or more positive grids, this noise is caused by irratic partition of the cathode current among the positive electrodes. In a transistor, the partition noise is created from the random fluctuation in the division of current between the collector and base.

71. Give the expression for noise voltage when several sources are cascaded.

Enr = Sqrt (4 KTB (R1 + R2 + …..) )

Where R1 , R2 --- are the resistances of the noise resistors.

K – Boltz man constant

T – absolute temperature

B – Bandwidth

72. Define random variable

Random variable is defined as a rule or mapping from the original sample space to a numerical sample space subjected to certain constraints. Random variable is also defined as a function where domain is the set of outcomes ωεs and whose range is R, is the real line.

73. Define Random process.

A Random process X (s,t) is a function that maps each element of a samples space into a time function called sample function. Random process is a collection of time functions.

74. Give the Laws of probability.

Additive law of probability

Case i

Case ii

When events are mutually exclusive , P (A∩B) =Φ

P(A∪B) = P(A) + P(B)

When events are not mutually exclusive

P(A∪B) = P(A) + P(B) - P (A∩B)

Multiplication law of probability:

Case i When events are independent

P(A∩B) = P(A) P(B)

Case ii When events are dependent

P(A∩B) = P(A) P(B/A)

= P(B) P(A/B)

75. What is frequency translation?

Suppose that a signal is band limited to the frequency range extending from a frequency f1 to a frequency f2. The process of frequency translation is one in which the original signal is replaced with a new signal whose spectral range extends from f1’ to f2’ and which new signal bears, in recoverable form the same information as was borne by the original signal.

76. What are two situations identified in frequency translations?

The two situations identified in frequency translation are i Up conversion

In this case the translated carrier frequency is greater than the incoming carrier frequency

ii Down conversion

In this case the translated carrier frequency is smaller than the incoming carrier frequency.

Thus, a narrowband FM signal requires essentially the same transmission bandwidth as the AM signal.

77. Define Tracking.

Tracking is the process of correctly tuning a number of tunable circuits in a

receiver.

78. What is TRF receiver?

Tuned Radio Frequency is also called straight receiver.Here the receiver operates in straight forward manner without frequency conversion.

79.What are the advantages of superheterodyne receiver over TRF?

The advantages of superheterodyne receiver over TRF are high selectivity

,improved sensitivity throughout the carrier frequency band..It eliminates image frequency.

80.What is the figure of merit of DSBSC system ?

The figure of merit of DSBSC signal is unity

81.Compare the noise performance of an AM and FM system?

The figure of merit of AM system is 1/3 when the modulation is 100 percent and that of FM is(3/2)mf2.The use of FM offers improved noise performance over AM when (3/2)mf2 > 1/3.mf –modulation index in FM.

82.What is Capture effect?

When the interference signal and FM input are of equal strength, the receiver fluctuates back and froth between them .This phenomenon is known as the capture effect.

83.What is threshold effect?

As the input noise power is increased the carrier to noise ratio is decreased the receiver breaks and as the carrier to noise ratio is reduced further crackling sound is heard and the output SNR cannot be predicted by the equation. This phenomenon is known as threshold effect.

84.How is threshold reduction achieved in FM system?

Threshold reduction is achieved in FM system by using an FM demodulator with negative feedback or by using a phase locked loop demodulator.

85. What is Pre-emphasis?

The premodulation filtering in the transistor, to raise the power spectral density of the base band signal in its upper-frequency range is called pre emphasis (or pre

distortion)

Pre emphasis is particularly effective in FM systems which are used for transmission of audio signals.

86. Define de-emphasis.

The filtering at the receiver to undo the signal pre-emphasis and to suppress noise is called de-emphasis.

87.Define Sampling theorem.

A band limited signal of finite energy, which has no frequency components higher than fm Hertz may be completely recovered from a knowledge of its samples taken at the rate of 2fm samples per second.

88.What do you infer from the receiver output of a coherent detector?

The output equation y(t)=1/2Cacm(t) +1/2nI(t) indicates that the message signal and in-phase noise component of the filtered noise appear additively at the receiver output. The quadrature component of the narrow band noise is completely rejected by the coherent detector.

89.When is the figure of merit of SSBSC system 1?

For the same average transmitted signal power and the same average noise power in the message bandwidth ,an SSB receiver will have exactly the same output signal to noise ratio as a DSB-SC receiver when both receivers use coherent detection for the recovery of the message signal.

90.Compare the noise performance of AM receiver with that of DSB-SC receiver.

The figure of merit of DSB-SC or SSB-SC receiver using coherent detection is always unity,the figure of merit of AM receiver using envelope detection is always less than unity.Therefore noise performance of AM receiver is always inferior to that of DSB- SC due to the wastage of power for transmitting the carrier.

91.What is the figure of merit of a AM system with 100 percent modulation?

The figure of merit of a AM system with 100 percent modulation is 1/3.This means that other factors being equal an AM system must transmit three times as much average power as a suppressed system in order to achieve the same quality of noise performance .

92.What are the characteristics of a receiver?

The characteristics of a receiver are sensitivity, selectivity, fidelity, signal to noise

ratio.

96.Why is equivalent noise temperature used for noise measurement?

For low noise devices the noise figure is close to unity, which makes the comparison difficult and hence it is preferable to use equivalent noise temperature.

97.What is the function of amplitude limiter in FM system?

The function of amplitude limiter in FM system is used to remove the amplitude variations by clipping the modulated wave at the filter output almost to the zero axis .The resultant wave is rounded off by another BPF that is an integral part of the limiter thereby suppressing the harmonics of the carrier frequency.

98.What are components in a frequency discriminator?

Frequency discriminator has got two components .Slope detector or differentiator with a purely imaginary frequency response that varies linearly with frequency. It produces output where the amplitude and frequency vary with the message signal. An envelope detector that recover the amplitude variations and produces message signal.

99.What is a post detection filter?

The post detection filter named as”base-band low pass filter” has a bandwidth that is just large enough to accommodate the highest frequency component of the messge signal.

100. Define lossless channel.

The channel described by a channel matrix with only one nonzero element in each column is called a lossless channel. In the lossless channel no sources information is lost in transmission.

101. Define Deterministic channel

A channel described by a channel matrix with only one nonzero element in each row is called a deterministic channel and this element must be unity.

102. Define noiseless channel.

A channel is called noiseless if it is both lossless and deterministic. The channel matrix has only one element in each row and in each column and this element is unity. The input and output alphabets are of the same size.

103. Prove that I (xi xj) = I(xi) + I(xj) if xi and xj are independent.

If xi and xj are independent.

P (xi xj) = P(xi) P(xj) I (xi xj) = log1/P(xi xj)

= log 1/ P(xi) P(xj)

= I(xi) + I(xj)

104. Explain Shannon-Fano coding.

An efficient code can be obtained by the following simple procedure, known as

Shannon- Fano algorthim.

1. List the source symbols in order of decreasing probability.

2. Partition the set into two sets that are as close to equiprobable as possible, and sign 0 to the upper set and 1 to the lower set.

3. Continue this process, each time partitioning the sets with as nearly equal probabilities as possible until further partitioning is not possible.

105. What are the types of Correlation?

The types of Correlation are Cross Correlation and Auto Correlation

106. What is the difference between Correlation and Convolution?

1. In Correlation physical time ‘t’ is dummy variable and it disappears after solution of an integral. But in convolution ‘ι’ is a dummy variable.

2. Convolution is a function of delay parameter ‘t‘ but convolution is a function of‘

t’.

3. Convolution is commutative but correlation is noncom mutative.

107. Define Signal.

A signal is defined as any physical quantity carrying information that varies with time. The value of signal may be real or complex. The types of signal are continuous signal and discrete time signal.

108.Define entropy.

Entropy is the measure of the average information content per second. It is given by the expression

H(X)=∑I P(xi)log2P(xi) bits/sample.

109.Define mutual information.

Mutual information I(X,Y) of a channel is defined by

I(X,Y)=H(X)-H(X/Y) bits/symbol

H(X)- entropy of the source

H(X/Y)- conditional entropy of Y.

110.State the properties of mutual information.

1. I(X,Y)=I(Y,X)

2. I(X,Y)>=0

3. I(X,Y)=H(Y)-H(Y/X)

4. I(X,Y)=H(X)+H(Y)-H(X,Y).

111.Give the relation between the different entropies.

H(X,Y)=H(X)+H(Y/X)

=H(Y)+H(X/Y)

H(X)- entropy of the source,H(Y/X),H(X/Y)-conditional entropy

H(Y)-entropy of destination

H(X,Y)- Joint entropy of the source and destination

112.Define information rate.

If the time rate at which source X emits symbols is r symbols per second. The information rate R of the source is given by

R=r H(X) bits/second

H(X)- entropy of the source

113.What is data compaction?

For efficient signal transmission the redundant information must be removed from the signal prior to transmission .This information with no loss of information is ordinarily performed on a signal in digital form and is referred to as data compaction or lossless data compression.

114.State the property of entropy.

1.0< H(X) < log2K , is the radix of the alphabet X of the source.

115.What is differential entropy?

The average amount of information per sample value of x(t) is measured by

H(X)= - ∞ ∫ fx(x)log fx(x)dx bit/sample

H(X) –differential entropy of X.

116.What is the channel capacity of a discrete signal?

The channel capacity of a discrete signal C= max I(X,Y) P(xi)

I(X,Y)-mutual information.

117. What is source coding and entropy coding?

A conversion of the output of a DMS into a sequence of binary symbols is called source coding. he design of a variable length code such that its average cod word length approaches the entropy of the DMS is often referred to as entropy coding.

118.State Shannon Hartley theorem.

The capacity ‘C’ of a additive Gaussian noise channel is C=B log2 (1+S/N) B= channel bandwidth ,S/N=signal to noise ratio.

119.What is the entropy of a binary memory-less source?

The entropy of a binary memory-less source H(X)=-p0 log2p0-(1-p0)log2(1-p0)

p0-probability of symbol ‘0’,p1=(1- p0 ) =probability of transmitting

symbol ‘1’

120.How is the efficiency of the coding technique measured?

Efficiency of the code =H(X) /L

L=∑p(xi)li average code word length .li=length of the code word.

121.What happens when the number of coding alphabet increases?

When the number of coding alphabet increases the efficiency of the coding technique decreases.

122.What is channel diagram and channel matrix?

The transition probability diagram of the channel is called the channel diagram and its matrix representation is called the channel matrix.

123.What is information theory?

Information theory deals with the mathematical modeling and analysis of a communication system rather than with physical sources and physical channels

124.What is the channel capacity of a BSC and BEC?

For BSC the channel capacity C=1+plog2 p +(1-p)log2(1-p). For BEC the channel capacity C=(1-p)