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Jawahar Navodaya Vidyalaya

Jawahar Navodaya Vidyalaya. Borai - Durg (C.G.). WELCOMES YOU. A Presentation On. Principle Of Communication. Prepared By Shri P. Ghosh P.G.T. (Physics). PRINCIPLE OF COMMUNICATION. INTRODUCTION.

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Jawahar Navodaya Vidyalaya

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  1. Jawahar Navodaya Vidyalaya Borai - Durg (C.G.) WELCOMES YOU

  2. A PresentationOn Principle Of Communication Prepared By Shri P. Ghosh P.G.T. (Physics)

  3. PRINCIPLE OF COMMUNICATION • INTRODUCTION New method of communication have been developed. We can talk to any person anywhere just by dialing a number on the telephone. The radio & television provide audio & visual information. Video phones, voice mail & satellite conferences enable us to see live images instantly and allow us to communicate directly with people located in different parts of the globe. Digital data transmission and retrieval has enabled us to realize e-mail, fax & internet.

  4. COMMUNICATION SYSTEM System to transmit information from one point to another

  5. It consist of three major parts : • 1. TRANSMITOR • 2. COMMUNICATION CHANNEL • 3. RECEIVER

  6. Communication System Message Output Transmitor Communication channel Receiver Signal Signal

  7. TRANSMITOR • A setup that transmits the message to the receiving end through a communication channel. • The basic component of transmitor are : • Message Signal Generator • Modulator • Antenna Original Message signal generator Modulator Amplifier Signal Carrier wave Oscillator

  8. MESSAGE SIGNAL • It is a single valued function of time that conveys the information.Signals can be analog or digital. • Analog Signal • A signal that is continuous function of time.

  9. (2) Digital Signal A discontinuous signal has two levels represented by 0 & 1. 1 1 0 0

  10. Bandwidth The range over which the frequencies in a signal vary, is called band width of the signal. Base band The term base band is to designate the band of frequency representing the original signal as delivered by source of information.

  11. Advantages of Digital Signal over Analog Signal • Freedom from noise and external disturbances. • Security of message is more improved. Safe for transmitting • secret message • 3. For transmission a common format is needed to encode • various type of message. (Audio, Video & Data Signal.

  12. MODULATION Modification of the message signal suitable for transmission. The audio frequency signals (20 htz to 20 k.htz) cannot be transmitted as such over a long distance. To overcome this difficulties we superimpose audio frequency signals on a high frequency sine wave, called a carrier wave. This process is called modulation.

  13. Carrier Waves (Radio Frequency) • The modulation of carrier wave is carried out by three ways : • Amplitude Modulation : The amplitude of the carrier wave vary according to the amplitude of the base band signal Audio Frequency Waves Carrier Waves (Radio Frequency)

  14. Advantages • It is easier method of transmission & reception of speech signal. • Receiver used are simple and cheap. Disadvantages • Small operating frequency range. • Low efficiency. • Noise in output. • Distorted reproduction. • Poor quality

  15. 2. Frequency Modulation : The frequency of carrier wave varied according to base band signal.

  16. Advantages • Wider operating frequency range. • More efficiency. • More noise resistance • Undistorted reproduction. • Good quality

  17. The television broadcast requires larger bandwidth and therefore requires F. M. Modulation as F. M. signal is having larger bandwidth. In F. M. Signal the intelligence is in the form of frequency variations and therefore the noise generated by atmospheric and men made electrical discharge does not harm the intelligence. However equipments needed to produce F. M. signals and receive them are more complex and expensive.

  18. Range of frequencies allotted for commercial F. M. Radio & TV broadcast

  19. 3. Pulse Modulation : • The A.M. and F.M. are extensively employed for Radio & TV • transmission . • Sampling of information signal at periodic intervals and • transmitting a very short pulse of radio frequency carrier for • each sample. • The common pulse system employed in pulse modulation of analog signals are : • Pulse Amplitude Modulation (P.A.M.) • Pulse Position Modulation (P.P.M.) • Pulse Duration Modulation (P.D.M.) • Pulse Code Modulation (P.C.M.)

  20. Pulse Amplitude Modulation (P.A.M.) : • Amplitude of the pulses of carrier pulse train is varied in • accordance with the instantaneous value of modulating signal. P. A. M.

  21. 2. Pulse Duration Modulation (P.D.M.) : The width of the pulses of carrier pulse train is varied in accordance with the instantaneous value of modulating signal. P. D. M.

  22. 3. Pulse Position Modulation (P.P.M.) : The position of the pulses of carrier pulse train is varied in accordance with the instantaneous value of modulating signal. P.P.M.

  23. 4. Pulse Code Modulation (P.C.M.) : The message transmitted by mean of coded signals following three operations : 1. Sampling 2. Quantisation 3. Coding

  24. Sampling : The process of generating pulses of zero width and • of amplitude equal to instantaneous amplitude of analog signal.

  25. 2. Quantisation : The process of dividing the maximum amplitude of the analog voltage Signal into a fixed number of level is called quantisation.

  26. 3. Coding : The process of digitizing the quantised pulses according to some code is called coding. Quantisation Level Binary Code 0 000 1 001 2 010 3 011 4 100 5 101 6 110 7 111

  27. ANTENNA An antenna is a vital component of any communication system. It is employed both at the transmitting as well as receiving end. At the transmitor it radiates Electromagnetic Wave. While at receiving end it picks up the transmitted signals. First conversion takes place at transmitor Electrical Signals in to Electromagnetic Wave and at receiving end E.M. wave in to Electrical Signals.

  28. Simple Dipole Antenna Dish Antenna

  29. COMMUNICATION CHANNEL The communication channel is the physical path between the transmitor and receiver. Transmission medium guided unguided Space communication Twisted pair Co-axial cable Optical fibre Optical communication Line communication Sky wave propagation 2 MHz to 30 MHz Space wave propagation 30 MHz to 300 GHz Surface wave propagation Up to 2 MHz

  30. The spectrum of electro-magnetic waves depiciting the frequency range being employed by various communication services

  31. Point to point transmission characteristics of guided media

  32. Characteristics of unguided communication bands

  33. RECEIVER Receiver is to re-construct the original message or data after its propagation through communication channel. The process consisting to decoupling of the carrier wave and modulating signal known as demodulation. Tunable Amplifier De-Modulator

  34. Arrangement of Transmission & Reception of Message Signal. Original Tunable Amplifier De-Modulator Message signal generator Modulator Amplifier Signal Carrier wave Oscillator

  35. MODEM A modem acts as a Modulator in transmitting end and as a De-Modulator at receiving end. MODEM MODEM Modulator De-Modulator Modulator De-Modulator Digital Signal Analog Signal Digital Signal On Telephone Line

  36. FAX The Electronic Transmission of a document at a distant place via telephone line is known as Facsimile or Fax.

  37. Original Document Digital Signal Sensor Modem Optical Scanner Light Signal Analog Signal On Telephone Line Digital Signal Sensor Modem Optical Scanner Fax Copy Printer

  38. END OF PART - I

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