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T ELEVISION - 1 T Srinivasa Rao1Communication Systems (EC-326)

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Presentation on theme: "T ELEVISION - 1 T Srinivasa Rao1Communication Systems (EC-326)"— Presentation transcript:

1 T ELEVISION - 1 T Srinivasa Rao1Communication Systems (EC-326)

2 EC 326 COMMUNICATION SYSTEMS UNIT - 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. T Srinivasa Rao3Communication Systems (EC-326)

4 Elements of a T V System Picture Transmission Sound Transmission Picture Reception Sound Reception Synchronization Receiver Controls Colour Television. T Srinivasa Rao4Communication Systems (EC-326)

5 Basic monochrome television transmitter T Srinivasa Rao5Communication Systems (EC-326)

6 Basic monochrome television receiver T Srinivasa Rao6Communication Systems (EC-326)

7 Simplified cross-sectional view of a Vidicon TV camera tube T Srinivasa Rao7Communication Systems (EC-326)

8 Path of scanning beam in covering picture area T Srinivasa Rao8Communication Systems (EC-326)

9 Elements of a picture tube T Srinivasa Rao9Communication Systems (EC-326)

10 Signal transmission paths illustrating compatibility between colour and 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 T Srinivasa Rao10Communication 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" T Srinivasa Rao11Communication 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" T Srinivasa Rao12Communication 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" T Srinivasa Rao13Communication 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 T Srinivasa Rao14Communication Systems (EC-326)

15 Vidicon TV Pick-up Tube T Srinivasa Rao 15 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. T Srinivasa Rao16Communication Systems (EC-326)

17 Television Scanning beam scanning for standard TV – 625 lines in total image frames – 25 images (frames) scanned per second Oscillators – Vertical – Horizontal Vertical (Slower) Horizontal (Faster) T Srinivasa Rao17Communication Systems (EC-326)

18 CRT T Srinivasa Rao18Communication Systems (EC-326)

19 TV Interlacing frame frame scanned in two passes, first the odd lines then the even – One frame takes 1/25th second – avoids flicker field each pass called a field – takes 1/50th second 1st Field (Odd lines)2nd Field (Even lines) + = += One Frame 1/50th sec. 1/25th sec. T Srinivasa Rao19Communication Systems (EC-326)

20 T Srinivasa Rao20Communication 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 Vertical Retrace Horizontal Retrace T Srinivasa Rao21Communication Systems (EC-326)

22 T Srinivasa Rao22Communication Systems (EC-326)

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24 Image Formation and Display T Srinivasa Rao24

25 Video Signal Voltage level indicates brightness Blanking during non-video – retrace T Srinivasa Rao25Communication Systems (EC-326)

26 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 T Srinivasa Rao26Communication Systems (EC-326)

27 T Srinivasa Rao27

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30 Details of Horizontal Scanning T Srinivasa Rao30Communication Systems (EC-326)

31 T Srinivasa Rao31Communication Systems (EC-326)

32 T Srinivasa Rao32Communication Systems (EC-326)

33 T Srinivasa Rao33Communication Systems (EC-326)

34 T Srinivasa Rao34Communication Systems (EC-326)

35 T Srinivasa Rao35Communication Systems (EC-326)

36 T Srinivasa Rao36Communication Systems (EC-326)

37 T Srinivasa Rao37Communication Systems (EC-326)

38 T Srinivasa Rao38Communication Systems (EC-326)

39 T Srinivasa Rao39Communication Systems (EC-326)

40 T Srinivasa Rao40Communication Systems (EC-326)

41 Characteristics of the 625-B Monochrome TV System 41

42 Next… Television – 2 … T Srinivasa Rao42Communication Systems (EC-326)


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