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T ELEVISION - 1

T ELEVISION - 1. EC 326 COMMUNICATION SYSTEMS UNIT - III. T Srinivasa Rao Dept. of ECE Bapatla Engineering College. Part 1. Vision characteristics and scanning systems, Composite video signal. Part 2 Camera tubes: Principle of operation, Image Orthicon, Vidicon , Plumbicon . Part 3

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T ELEVISION - 1

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  1. TELEVISION - 1 Communication Systems (EC-326)

  2. EC 326 COMMUNICATION SYSTEMSUNIT - III T Srinivasa Rao Dept. of ECE Bapatla Engineering College

  3. Part 1 Vision characteristics and scanning systems, Composite video signal. Part 2 Camera tubes: Principle of operation, Image Orthicon, Vidicon, Plumbicon. Part 3 Block diagram of broad cast TV transmitter Block diagram of broadcast TV receiver. Communication Systems (EC-326)

  4. Elements of a T V System • Picture Transmission • Sound Transmission • Picture Reception • Sound Reception • Synchronization • Receiver Controls • Colour Television. Communication Systems (EC-326)

  5. Basic monochrome television transmitter Communication Systems (EC-326)

  6. Basic monochrome television receiver Communication Systems (EC-326)

  7. Simplified cross-sectional view of a Vidicon TV camera tube Communication Systems (EC-326)

  8. Path of scanning beam in covering picture area Communication Systems (EC-326)

  9. Elements of a picture tube Communication Systems (EC-326)

  10. Signal transmission paths illustrating compatibility between colourand monochrome TV systems.R, G and B represent three camera tubes which develop video signals corresponding to the red, green and blue contents of the scene being televised Communication Systems (EC-326)

  11. Television System NTSC Standard (National Television Standards Committee) • Standard for U.S., Japan, and Korea • 4 X 3 Aspect Ratio • 525 Lines • 30 Frames Per Second • Scanned in "Fields" Communication Systems (EC-326)

  12. PAL System (Phase Alternating Line) • Another World Television Standard • 4 X 3 Aspect Ratio • 625 Lines • 25 Frames Per Second • Scanned in "Fields" • There are Slight Variations: PAL-B, -G, -H, -N • Used in Continental Europe and Parts of Africa, Middle East & So. America • More Lines = Better Resolution • Fewer Frames/Fields = More "Flicker" Communication Systems (EC-326)

  13. SECAM System (Sequential Color and Memory) • Another World Television Standard • 4 X 3 Aspect Ratio • 625 Lines • 25 Frames Per Second • Scanned in "Fields“ • Used in France, Eastern Europe and Parts of the Middle East & Africa • More Lines = Better Resolution • Fewer Frames/Fields = More "Flicker" Communication Systems (EC-326)

  14. HDTV System (High Definition Television) • 16 X 9 Aspect Ratio • A Digital System • Permits Several Levels of Picture Resolution Similar to that of High-Quality Computer Monitors, With 720 or 1080 Lines (1280 x 720 pixels or 1920 x 1080 pixels) • Ranges from 24 to 60 frames per second, progressive or interlaced scan • Uses MPEG-2 Compression to squeeze a 19 megabit-per-second data flow so that it can be accommodated by a standard broadcast TV channel of 6 MHz bandwidth • 5.1 Channels of Dolby AC-3 Digital Surround-Sound Audio Communication Systems (EC-326)

  15. Vidicon TV Pick-up Tube Communication Systems (EC-326)

  16. Basic Factors • Structure ( Aspect ratio – 4:3 ) • Continuity ( 25 FPS ) • Scanning lines (860 x 0.7) • Flicker ( Interlaced Scanning) • Resolution ( Vertical & Horizontal) • Other factors. Communication Systems (EC-326)

  17. Television Scanning • beam scanning for standard TV • 625 lines in total image • 25 images (frames) scanned per second • Oscillators • Vertical • Horizontal Vertical (Slower) Horizontal (Faster) Communication Systems (EC-326)

  18. CRT Communication Systems (EC-326)

  19. 1/50th sec. 1/50th sec. TV Interlacing • frame scanned in two passes, first the odd lines then the even • One frame takes 1/25th second • avoids flicker • each pass called a field • takes 1/50th second + = 1st Field (Odd lines) 2nd Field (Even lines) One Frame + = 1/25th sec. Communication Systems (EC-326)

  20. Communication Systems (EC-326)

  21. Synchronization • TV Camera & Monitor must be synchronized • beam at same place on image • special sync pulses sent at end of each horizontal line & vertical field • retrace • horizontal retrace • beam returned to left side of screen • vertical retrace • beam returned to the top of screen • Turns off video during retrace Horizontal Retrace Communication Systems (EC-326) Vertical Retrace

  22. Communication Systems (EC-326)

  23. Image Formation and Display

  24. Video Signal • Voltage level indicates brightness • Blanking during non-video • retrace Communication Systems (EC-326)

  25. Vertical Resolution • proportional to # of vertical scan lines • theoretic maximum • half # of visible scan lines • black lines alternate with white • max. line pairs = video lines / 2 Communication Systems (EC-326)

  26. Details of Horizontal Scanning Communication Systems (EC-326)

  27. Communication Systems (EC-326)

  28. Communication Systems (EC-326)

  29. Communication Systems (EC-326)

  30. Communication Systems (EC-326)

  31. Communication Systems (EC-326)

  32. Communication Systems (EC-326)

  33. Communication Systems (EC-326)

  34. Communication Systems (EC-326)

  35. Communication Systems (EC-326)

  36. Communication Systems (EC-326)

  37. Characteristics of the 625-B Monochrome TV System

  38. Next…Television – 2 … Communication Systems (EC-326)

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