DTEL(Department for Technology Enhanced Learning)

Transcription

1 The (Department for Technology Enhanced Learning) Centre for Technology enabled Teaching & Learning Teaching Innovation - Entrepreneurial - Global 1

2 Presentation on Audio Video Engineering Author Suraj Patinge M-Tech (VLSI Design),Lecturer Electronics Engineering Department Suraj Irkhede M-Tech (VLSI Design),Lecturer Electronics & Tele Engineering Department Department of Electronics Engineering Nagar Yuwak Shikshan Sanstha s Shri Datta Meghe Polytechnic Wanadongri, Hingna Road Nagpur

3 PREFACE As educators, weallhavethesamecommongoal to guideourstudents so thatthey gain the maximum possible in a positive environment that promotes their success and inculcates in them desire to learn. Oneof the best tools available to us in this pursuit is PPT instruction that is systematic and self Learning. The goal of this PPT is to help teachers in the use of elearning that it is both effective and efficient method for teaching our students. It has been developed for purely academic and non-commercial purpose. Our desire in preparing this PPT is to support the teachers, who have the very demanding task of Teaching-Plan to deliver instruction on a lecture/period basis. The PPT is therefore prepared lecture wise. Further at the end of each chapter Questions have also been included for practice. WebegininChapter1withbasicelementslikeDifferenttypesofAudiosystem&there advantages. In Chapters 2 we learn in details the Architecture of CD Player. Chapter 3 we understand the concept of Black & White and Color Television. Chapter 4 concentrates on TV Transmitter & Receiver. In Chapter 5, we focus on Color TV Receiver. Chapter 6 presents Understanding of MATV,CATV,CCTV. With deep regards and humility, we thank both our Management of MGI for motivating and our CEO for strong follow-ups to prepare PPTs under. We dedicate this PPT to students and our shared profession. S.U.Patinge Suraj Irkhede 3

4 CONTENT: AUDIO VIDEO ENGINEERING 1. CHAPTER 1: Hi Fi Audio Amplifier Slide no : 6 2 CHAPTER 2: CD player Slide no : 37 3 CHAPTER 3: TV Fundamentals Slide no : 61 4 CHAPTER 4: TV Transmitter and Receiver Slide no : 91 5 CHAPTER 5: Colour TV. Slide no : CHAPTER 6: Cable Television Slide no : 183 4

5 GENERAL OBJECTIVE The student will be able to: 1 2 Understand operation of audio amplifiers. Analyze quality of reception of various sound systems and graphic equalizer. 3 Understand CD player mechanism.. 4 Understand the principle of operation of various advanced TV systems. 5

6 CHAPTER 1:- SYLLABUS 1 2. Introduction to Amplifiers: Mono, Stereo, PA Difference between Stereo and Mono amplifier Block diagram of Hi Fi amplifier and its working Dolby NR recording system Types of speaker Woofer, Mid-range, Tweeter 6 Cross over network circuit and its function 6

7 CHAPTER-1 SPECIFIC OBJECTIVE / COURSE OUTCOME The student will be able to: 1 Distinguish between different types of Audio amplifiers 2 Draw labeled sketch of Hi-Fi amplifier 3 Define pre-emphasis and de-emphasis 7

8 LECTURE 1.1 :- HI-FI Amplifier Block diagram of mono amplifier system Fig 1.1 : Block diagram of mono amplifier 8 8

9 LECTURE 1.1 :- HI-FI Amplifier Mono amplifier system (Figure -1.1) Mic : It convert sound waves into electrical signal & send to buffer stage. Buffer stage : It s function is to provide impedance matching. Power amp : It can provide amplified signal for different sound waves. Loud speaker : It Convert electrical signal into sound signal. 9

10 LECTURE 1:-LECTURE HI-FI AMPLIFIER 1.1 :- HI-FI Amplifier Block diagram of Stereophonic amplifier Fig 1.2: Block diagram of stereophonic amplifier 10 10

11 LECTURE LECTURE1:- HI-FI AMPLIFIER 1.1 :- HI-FI Amplifier Stereophonic amplifier (Figure -1.2) Mic : It convert sound waves into electrical signal & send to buffer stage. Power amp : Provide amplified signal for different sound waves. Loud speaker : It Convert electrical signal into sound signal

12 LECTURE LECTURE1:- HI-FI BASICS AMPLIFIER OF 1.1 ELECTRONIC :- COMM. HI-FI Amplifier Advantages : Sound has direction right & left. This system is used for high-fidelity amplification purpose. Disadvantages : Amplitude/frequency/phase distortion is more

13 LECTURE 2:- LECTURE1:- HI-FI BASICS AMPLIFIER OF 1.2 ELECTRONIC :- COMM. HI-FI Amplifier Public address amplifier system Amplifier used for addressing the people is known as public address amplifier. Provide sound to long distance without scarifying the original signal / information

14 LECTURE 2:- LECTURE1:- HI-FI BASICS AMPLIFIER OF ELECTRONIC :- COMM. HI-FI Amplifier Block diagram of Public address amplifier Mixer Voltage Amplifier Processing Control Driver Amplifier Fig 1.3: Block Diagram of Public address amplifier 14 14

15 LECTURE 2:- LECTURE1:- HI-FI BASICS AMPLIFIER OF ELECTRONIC :- COMM. HI-FI Amplifier Public address amplifier (Figure -1.3) Mic : It convert Sound Waves Into Electrical signal. Mixer : It combines all the input& produced output V4=v1+v2+v3. Voltage Amplifier : Amplifies weak signal coming from mixer stage

16 LECTURE 2:- LECTURE1:- HI-FI BASICS AMPLIFIER OF 1.2 ELECTRONIC :- COMM. HI-FI Amplifier Public address amplifier (Figure -1.3) Power amp : Provide high amplified signal for different sound waves. Loud speaker : It Convert electrical signal into sound signal

17 LECTURE 2:- LECTURE1:- HI-FI BASICS AMPLIFIER OF 1.2 ELECTRONIC :- COMM. HI-FI Amplifier Advantages : Minimum noise level For amplification of speech signal frequency response is flat. Gain is constant. Disadvantages : It has the effect of positive feedback which will oscillate the amplifier & will reproduced the distortion

18 LECTURE 3:- LECTURE1:- HI-FI BASICS AMPLIFIER OF 1.3 ELECTRONIC :- COMM. HI-FI Amplifier Minimum requirement of HI-FI amplifier. Directional sound. HI-FI Amplifier System (Figure 1.4) Amplifier output is similar to original information called HI-FI amplifier It should have minimum frequency & phase distortion. Minimum noise level. Flat frequency

19 LECTURE 3:- LECTURE1:- HI-FI BASICS AMPLIFIER OF 1.3 ELECTRONIC :- COMM. HI-FI Amplifier Block Diagram of HI-FI Amplifier System Fig 1.4: Block Diagram of HI-FI amplifier 19 19

20 LECTURE 3:- LECTURE1:- HI-FI BASICS AMPLIFIER OF 1.3 ELECTRONIC :- COMM. HI-FI Amplifier HI-FI Amplifier System (Figure 1.4) Output from various input sources like disk player or mic are connected to switches. Switches are connected to pre-amplifier whose function is to provide AV=high. Output of pre-amplifier contain more noise to remove these noise we used equalizer. Equalizer consist of different filters like low, medium & high frequency filter

21 LECTURE 3:- LECTURE1:- HI-FI BASICS AMPLIFIER OF 1.3 ELECTRONIC :- COMM. HI-FI Amplifier Output of equalizer fed to power amplifier to provide Av =high & Ai=high & fed to crossover network through impedance matching circuit. Output of crossover network contains electrical signal for 60Hz to 15Khz with flat frequency response. One speaker is unable to reproduced equal intensity sound hence, a separate speaker is used for low, medium & high frequency as woofer, midrange & tweeter. Crossover network separate low frequency signal for woofer, medium frequency signal for midrange & high frequency signal for tweeter 21 21

22 LECTURE 3:- LECTURE1:- HI-FI BASICS AMPLIFIER OF 1.3 ELECTRONIC :- COMM. HI-FI Amplifier Compare Stereo / Mono Amplifier Stereo Amplifier. Two dimensional sound Two pre-amplifier used Sound is natural Direction of sound sensed easily Costly Mono Amplifier. Direction sound One pre-amplifier used Lack of naturalness No sense of direction Less costly than stereo Table1 : Comparison between Stereo & Mono Amplifier 22 22

23 LECTURE 3:- LECTURE1:- HI-FI BASICS AMPLIFIER OF 1.3 ELECTRONIC :- COMM. Compare Stereo / PA Amplifier Stereo Amplifier. Distance increases sound level decreases Noise is more Sensitivity is less Echo effect is more Variation in gain with respect to temperature Less costly HI-FI Amplifier PA Amplifier. They prefer for addressing people for larger area. Minimum noise level Sensitivity is more Echo effect is less It is high power temperature compensated so, variation in gain is minimum Cost is more Table 2 : Comparison between Stereo & PA Amplifier 23 23

24 LECTURE 4:- LECTURE1:- HI-FI AMPLIFIER 1.4 :- Compare Woofer/Midrange/Tweeter Parameter Woofer Mid Range Tweeter Frequency response HI-FI Amplifier 16Hz to 500Hz 500Hz to 5Khz 5Khz to 20Khz Size Large Medium Small Cross over Used 2 & 3 Only 3 way Used 2 & 3 network way system system way system Cost Large Medium Less Uses in Frequency Passed Mono / Stereo amplifier. Hi-Fi system Stereo/Hi-Fi system Low Medium High Table 3 : Comparison between Woofer, Midrange & Tweeter 24 24

25 LECTURE 4:- LECTURE1:- HI-FI AMPLIFIER 1.4 :- HI-FI Amplifier Microphone gain control. Controls of Hi-Fi System Master gain control (Volume control). Tone control 1. Bass control 2. Treble control 25 25

26 LECTURE 4:- LECTURE1:- HI-FI AMPLIFIER 1.4 :- HI-FI Amplifier Microphone Gain Control Controls output of microphone. Connected in either pre-amplifiers or mixers. Potentiometers are used for the gain controls. Master Gain Control Logarithmic potentiometers are used for the gain control which matches logarithmic response of the human ears. Value of resistance is twice that of load

27 LECTURE 5:- LECTURE1:- HI-FI BASICS AMPLIFIER OF 1.5 ELECTRONIC :- COMM. Tone Control HI-FI Amplifier Bass Control: Bass effect will increase if capacitance in series with the signal increases. Higher the capacitance the value of reactance decreases. Fig 1.5: Circuit diagram of Bass Control 27 27

28 LECTURE 5:- LECTURE1:- HI-FI AMPLIFIER 1.5 :- Treble Control HI-FI Amplifier High resistance at potentiometer will develop maximum signal across the load and goes on boosting treble. For high value of capacitance value the reactance decreases (Xc=2*pi*fc) Fig 1.6: Circuit diagram of Treble Control 28 28

29 HI-FI Amplifier Graphic equalizer Special type of tone control where audio spectrum is divided into various narrow spectrums. LECTURE 5:- LECTURE1:- HI-FI BASICS AMPLIFIER OF 1.5 ELECTRONIC :- COMM. Individual spectrums can be boosted by moving sliders in between +15 db to -15 db. Fig 1.7: Frequency response of graphic equalizer 29 29

30 LECTURE 6:- LECTURE1:- HI-FI AMPLIFIER 1.6 :- HI-FI Amplifier Cross Over Networks Necessity of cross over network : To avoid overheating of speaker. To increase overall efficiency. To avoid distorted output when full power is fed to load outside the frequency range

31 LECTURE 6:- LECTURE1:- HI-FI AMPLIFIER 1.6 :- Cross over network (2 way) Consists of low pass filter connected across woofer and high pass filter connected across tweeter. fc is lower cut off frequency for high pass filter while it is higher cut off frequency for low pass filter HI-FI Amplifier Response Curve Fig 1.8: Circuit diagram of 2 way cross over network Circuit Diagram 31 31

32 LECTURE 7:- LECTURE1:- HI-FI AMPLIFIER 1.7 :- HI-FI Amplifier Cross over network (3 way) Fig 1.9: Circuit diagram of 3 way crossover network Response Curve 32 32

33 LECTURE LECTURE1:- 7:- HI-FI AMPLIFIER 1.7 :- HI-FI Amplifier Dolby NR (Noise Reduction) Recording System Required to emphasis (Boost) the low power signal before recording since these signal are more effected by noise. Low power notes are more closer to the noise signal. These signals are pre-emphasized before recording and de-emphasized before playing them back

34 LECTURE 7:- LECTURE1:- HI-FI AMPLIFIER 1.7 :- HI-FI Amplifier Pre-emphasis is of 10db to 15db for low power notes. Selected signals are pre-emphasized which are below a predetermined level while above this are passed through dolby system directly. Two types of dolby systems. 1) Dolby A systems. 2) Dolby B systems

35 LECTURE 7:- LECTURE HI-FI AMPLIFIER 5:-1.7 :- HI-FI Amplifier Chapter 1 Question Bank List important characteristics of hi-fi amplifier & draw its block diagram. State and explain necessity of cross-over network in hi-fi amplifier. With neat circuit diagram explain operation of graphic equalizer. What is hi-fi system? list specification of hi-fi system. Compare woofer, tweeter and squeakers 35

36 LECTURE 7:- LECTURE1:- HI-FI AMPLIFIER 1.7 :- Summary HI-FI Amplifier Tone control circuit is used to modify an audio signal before it is fed to speaker. Equalization is processed for adjusting the strength of certain frequencies. Multi-speaker system uses woofer, midrange and tweeter. Hi-FI system is produces high quality sound as compared to stereo, Mono & PA amplifier system

37 CHAPTER 2:- SYLLABUS 1 2. CD Material used, Size and Capacity. Block diagram and operation of CD player. 3 4 Component used for CD mechanism: Function of remote control transmitter and receiver CD 37

38 CHAPTER-2 SPECIFIC OBJECTIVE / COURSE OUTCOME The student will be able to: 1 Describe the principle detection mechanism of CD player 2 List the components used in CD mechanism 38

39 LECTURE 2.1:- CD Player The compact disc is one of the popular form of entertainment in digital technology. The 1000 th play of compact disc will sound every bit as good as the first. The disc rotates at 500 rpm when the laser beam starts at centre and slows to 200 rpm to the outer side of the disc. CDs have a special feature called programming

40 LECTURE LECTURE 1:- CD PLAYER 2.1:- CD Player Material used and size CD Made of polycarbonate materials. 12 cm in diameter and 1.2 mm thick. Consists of reflective layer surface coated with thin layer of aluminum. Surface covered with transparent plastic coating

41 LECTURE LECTURE 1:- CD PLAYER 2.1:- Specification of CD CD Player Specification Full disc diameter 120 mm or 12 cm (4.75 ) Disc thickness 1.2 mm Disc material Polycarbonate Track width 0.5 micron approx Sampling frequency 1.6 microns (nominal) Frequency response 5 to hz + /- 3db Harmonic distortion 0.008% at 1 khz Signal to noise ratio Greater than 85 db 41 41

42 LECTURE LECTURE 1:- CD PLAYER 2.1:- CD Player Programming is possible. Features Particular section on CD can be selected for play. Unwanted programme can be skipped while playing. Random or shuffle play is possible. Covered by transparent plastic or lacquer

43 LECTURE LECTURE 1:- CD PLAYER 2.1:- CD Player Block diagram of CD Player CD For Digital Output BNC/RCA Servo Control Board 7 Segment Display & Push Button Remote Control Digital Filter D.S.P & DAC Section Output Stage &Filter Analog Output Left Analog Output Right Power Supply Unit & AC Mains Power Transformer Fig 2.1 : Block diagram of CD Player 43 43

44 LECTURE LECTURE 1:- CD PLAYER 2.1:- CD Player The optical mirror and lens system reads the data from the CD. CD Player(Figure -2.1) The digital output is converted into original analog signal by using digital to analog converter. The scanning of the tracks by laser beam is done from the centre towards the edge. As the circumference of the outer spirals is larger than the inner spirals the track speed is made constant, i.e. constant linear velocity of 1.2 m/sec

45 LECTURE LECTURE 2 :- CD PLAYER 2.2:- CD Player Component used in CD Player Pickup assembly. Gear system. Drive motors. CD lens

46 LECTURE LECTURE 2 :- CD PLAYER 2.2:- CD Player CD Mechanism track focus CD sled diffraction grating detectors laser 46 Fig 2.2 : CD Mechanism 46

47 LECTURE LECTURE 2 :- CD PLAYER 2.2:- CD Player CD Mechanism (Figure -2.2) The laser beam is generated by small, low power semiconductor diode made up of aluminum-galliumarsenide. The CD carries the left and right channel information separately but interleaves on a single track. Signals are recorded in PCM format. CD is scanned by a sever-control, optical pickup at a constant linear velocity of 1.2 meters per second

48 LECTURE LECTURE 2 :- CD PLAYER 2.2:- CD Player Track pitch Diameter Pit length Pit depth Pit width Laser wavelength CD Medium 1.6 microns 120 mm microns 0.11 microns 0.5 microns 780 nm 48 48

49 LECTURE LECTURE 3 :- CD PLAYER 2.3:- Interleaving CD Player The majority of errors that may occur during playback of CD results from scratches, dust and dirt that may reflect the laser beam. Because of the high density of information on CD, such deflects can easily wiped out several adjacent bits or samples on track. If all the affected samples belong to the same frame, many multiposition errors can occur inside each frame. Interleaving is used to avoid multiposition errors in a frame during playback

50 LECTURE LECTURE 3 :- CD PLAYER 2.3:- CD Player De-interleaving De-interleaving occurs in the CD player at the time of playback. During reading of the CD, the same dropout occurs and again results in three missing data symbols (4,6 and 8). De interleaving is then performed in the CD player to restore the original sequence of data symbols

51 LECTURE LECTURE 4 :- CD PLAYER 2.4:- CD Player Controls system in CD Player The control system of CD player is microprocessor based system. The necessary controls are play and eject, with the addition of at least pause and some buttons which allows rapid skipping through the program material

52 LECTURE LECTURE 4 :- CD PLAYER 2.4:- CD Player Controls on front panel of CD player Fig 2.3 :Front panel of CD Player 52 52

53 LECTURE LECTURE 4 :- CD PLAYER 2.4:- CD Player Controls on front panel of CD player 1. Standby Button 2. Disk Tray 3. Front panel Display 4. Remote Sensor 5. Open Close Button 6. Playback Dial 7. Pause Button 8. Stop Button 9. Surround Button 10. Picture Mode Button 53 53

54 LECTURE LECTURE 4 :- CD PLAYER 2.4:- CD Player Remote Control of CD Player Remote control transmitter consists of encoder circuit, battery power supply and infra-red led transmitter. It has a transmitter which transmits infra-red waves towards the receiver. this receiver detects the infra-red waves and produces specific electronic signals. Every key has different circuit configuration

55 LECTURE LECTURE 4 :- CD PLAYER 2.4:- CD Player Functions of Remote Control Power. Eject. Phase. Program. Repeat. Shuffle. On/Off Time. Preamplifier control. Volume up and down control. Mute function

56 LECTURE LECTURE 4 :- CD PLAYER 2.4:- CD Player Advantages of Florescent display used in CD Player A visual indication of CD player status is displayed on a multicharacter vacuum florescent display. The vacuum florescent display is easy to read and coupling with standard remote handset. Vacuum florescent display are bright enough to read in full sunlight as well as dimmable for use at night. Viewing angle is more than 45 degree

57 LECTURE LECTURE 5 :- CD PLAYER 2.5:- Advantages of CD CD Player High density digital data storage. No wear and tear since CD is read by laser beam. Good sound quality. Less distortion and no audible background noise. Constant speed of read out can be maintained. Smaller in size. Immune to surface contamination

58 LECTURE LECTURE 5 :- CD PLAYER 2.5:- CD Player Disadvantages of CD Data stored once can not be erased or altered. Read only in nature (i.e. cd-rom). CD read/write needs specialized set-ups. Cost of CD write or read equipments may be higher

59 LECTURE LECTURE 5 :- CD PLAYER 2.5:- Application of CD CD Player RADIO and TV studios Data backups. Transportation of software and data. Business data storage in large capacity. Film achieves. Storage of entertainment programs. Data storage for longer durations

60 LECTURE 7:- LECTURE1:- HI-FI AMPLIFIER 2.5:- 1.7 :- Summary CD Player The CD player system is basically similar to any other audio player system such as cassette tape recorder with some additional digital signal processing circuit. The CD can contain any kind of audio signal such as long speeches, music, etc. Digital circuit offers almost complete immunity to noise. Storage capacity of CD is more as compared with cassette tape. Sound quality is good

61 LECTURE LECTURE 5 :- CD PLAYER 2.5:- State the advantages of CD. CD Player Chapter 2 Question Bank What is frequency interleaving? why it is used in CD player. State the function of various drive motors in CD players. List the advantages of fluorescent display system used in CD player. Draw & explain block diagram of CD player. 61

62 CHAPTER 3:- SYLLABUS 1. Concept: Aspect ratio, image continuity Vestigial sideband transmission Colour theory. Composite Video Signal TV channel allocation for band I & band III. 62

63 CHAPTER-3 SPECIFIC OBJECTIVE / COURSE OUTCOME The student will be able to: 1 Define various terms used in TV system 2 Draw and label composite video signal wave-forms 3 State CCIR-B standards for TV system 63

64 LECTURE 3.1:- Aspect ratio TV Fundamental The width to height ratio is called as aspect ratio and it is fixed at 4:3 where 4= width, 3= height. It is fixed to 4:3 ratio, it gives best viewing comfort, and artistic appreciation are obtained when picture has a rectangular format. Binocular vision of our eyes is greeter in the horizontal plane than in vertical plane. The region of maximum resolution at the centre of the retina has greater area along the width than height

65 LECTURE 1:- LECTURE TV FUNDAMENTAL 3.1:- Image continuity TV Fundamental When the picture information is transmitted line by line, we get impression of continuity due to a phenomenon called persistence of vision of the human eye. Persistence of vision is the property of human eye that any impression produced on the retina will persist for 1/16 th of a second. If within short interval of persistence of vision, a series of images are presented to the eye, and eye will see the images without break is called image continuity

66 LECTURE 1:- LECTURE TV FUNDAMENTAL 3.1:- Scanning Technique TV Fundamental Scanning is the process similar to the reading the written information on the page, starting at top left and end at the bottom right. The scanning is also done line-by-line horizontally from left to right at a fast rate and vertically from top to bottom at a slow rate

67 LECTURE 1:- LECTURE TV FUNDAMENTAL 3.1:- Scanning Technique TV Fundamental Start of a line W End of a line H Trace Retrace Raster Fig 3.1 : Scanning used in TV 67 67

68 LECTURE 1:- LECTURE TV FUNDAMENTAL 3.1:- Interlaced scanning TV Fundamental In this there are two sequences of scanning for each frame, scanning lines of one sequence occur in between the line of the other sequence. The numbers in the figure 3.2 are for 625 lines per frame and blanking period for each sequence is equal to 20 lines. The figure 3.2. shows interlaced scanning, the first sequence of scanning starts left corner and end at point enter of bottom, after completing 292 ½ lines. The vertical retrace start scanning from center of bottom at the middle of top which takes 20 lines

69 LECTURE 1:- LECTURE TV FUNDAMENTAL 3.1:- Interlaced scanning TV Fundamental Line 1 Line 2 Line 3 Line 314 Line 315 Line 316 Even Fields Retrace during line 313 at theendofevenfield Retrace at the end of line 625 beginning of line 1 at the end of odd filed Odd Fields Line 311 Line 312 Line 313 Line 623 Line 624 Line 625 Fig 3.2 : Interlace Scanning 69

70 LECTURE 1:- LECTURE TV FUNDAMENTAL 3.1:- Interlaced scanning TV Fundamental Fig 3.2 : Interlace Scanning [4] 70 70

71 LECTURE 2 LECTURE :- TV FUNDAMENTAL 3.2:- TV Fundamental Scanning periods horizontal Duration of one horizontal line is 1/15625=64ms out of 64ms, active line period is 52ms and remaining 12ms is blanking period. Scanning periods Vertical The line frequency set at 50 Hz, the nominal duration of one vertical trace is 20ms (1/50=20ms), 20ms can be divide into trace period + retrace period=18.720ms ms 71 71

72 LECTURE 2 LECTURE :- TV FUNDAMENTAL 3.2:- Vestigial sideband transmission In this video is modulated in AM & sound is modulated in FM. In AM one carrier & two sideband. Information contain in both the sideband. TV Fundamental They consume more power & more bandwidth. Neglecting one sideband will loss brightness information of video. Transmission of one complete sideband (USB) & part of (LSB) this method of transmission is called as (VSB)

73 LECTURE 2 LECTURE :- TV FUNDAMENTAL 3.2:- TV Fundamental Advantages of Vestigial sideband Less power required. Bandwidth required is less. Disadvantages of Vestigial sideband It produced phase distortion. It may affect due to characteristics or specification of Video signal like hue, luminance, brightness, contrast etc

74 LECTURE 3 LECTURE :- TV FUNDAMENTAL 3.3:- TV Fundamental Bandwidth for Color signal In the PAL color system is compatible with the CCIRB-625 line monochrome system. The color subcarrier is located 4.43 MHz away from the picture carrier. Brightness signal is transmitted at frequency bandwidth of 5MHz, however such a large frequency spectrum is not necessary for color video signal. Thus the maximum bandwidth is necessary for color signal transmission is around 3 MHz

75 LECTURE 3 LECTURE :- TV FUNDAMENTAL 3.3:- TV Fundamental Specification of color or color characteristics Brightness in TV picture is the average intensity of light. It determines the background level of illumination in the reproduced picture. In TV receiver, brightness can be increase or decreases by changing the DC bias between the control grid and cathode of the picture tube

76 LECTURE 4 LECTURE :- TV FUNDAMENTAL 3.4:- TV Fundamental Contrast Thus illumination of pixel will appear differently with different brightness of the background. For example a white pixel will appear very white in contrast with black background, but will appear dual white in white background. In other words contrast is the variation in brightness of individual pixel over the general average brightness of the whole screen, the two phenomena contrast & brightness are interrelated

77 LECTURE 4 LECTURE :- TV FUNDAMENTAL 3.4:- TV Fundamental Viewing distance luminance It is the total amount light intensity/energy which is received by human eye irrespective light is called as luminance. It is the measure of visual sensation of the quantity or brightness of light emitted from a pixel. Luminance is not concerned with the surrounding, it is concerned with the pixel from which light is being emitted. The eye is not equally sensitive to all color, it is sensitivity is 59% for green, 30% for red and 11% for blue

78 LECTURE 4 LECTURE :- TV FUNDAMENTAL 3.4:- TV Fundamental Grassman s law When a color is produced by adding three primary colors, its luminance is the sum of luminance of individual primary colors. This algebraic relationship is called Grass man s law. Y=0.59(G)+0.30(R)+0.11(B),where R,G,B are the intensities of green, red, blue lights

79 LECTURE 4 LECTURE :- TV FUNDAMENTAL 3.4:- TV Fundamental Hue or tint This is predominant spectral color in light. It is the actual color seen by the human eye. Example:- Red, Green & Blue color represent different color in visible spectrum

80 LECTURE 5 LECTURE :- TV FUNDAMENTAL 3.5:- TV Fundamental It shows the purity of color. Saturation It is the amount of light mixed with color. A color which is diluted with pure red without white is saturated color but red mixed with white is de saturated

81 LECTURE 5 LECTURE :- TV FUNDAMENTAL 3.5:- TV Fundamental Compatibility Color TV system produced a normal Black & White picture on Black & White TV receiver without any modification is known as compatibility. Similarly Black & White transmission should be able to produced Black & White picture on color TV screen is known as reverse compatibility

82 LECTURE 5 LECTURE :- TV FUNDAMENTAL 3.5:- TV Fundamental Color Theory Light rays are electromagnetic waves whose properties are governed by the frequency or wavelength. There are two types of color : 1) Primary color 2) Secondary color 82 82

83 LECTURE 5 LECTURE :- TV FUNDAMENTAL 3.5:- TV Fundamental Primary color There are three primary colors red, green, blue. They are called as primary because all other colors can obtained by mixing of these three colors in appropriate proportion. When all three primaries colors are incident in equal strength, we get white color or gray shades of white

84 LECTURE 6 LECTURE :- TV FUNDAMENTAL 3.6:- TV Fundamental Secondary / Complementary When any two primary colors of equal intensity are mixed, the resultant color is called complementary color. They are also known as secondary color. There are three complementary color yellow, cyan, magenta. these are obtained as Red + Green = Yellow, Green + Blue = Cyan, Blue + Red = Magenta. These are also known as complementary colors because when combined with the remaining primary color they give white. Yellow is complementary to Blue because Yellow + Blue will give white

85 LECTURE 6 LECTURE :- TV FUNDAMENTAL 3.6:- TV Fundamental Additive Mixing of Colors Additive mixing shows the addition of basic primary color in specific percentage to developed a desired color example:- 30%red +59%green +11%blue = white. This additive mixture of RGB form white color Example:30%red +11%blue = magenta,30%red +59%green = yellow,11%blue +59%green = cyan. Mixture of three primary color RGB in adjustable intensity can create different types of color

86 LECTURE 7 LECTURE :- TV FUNDAMENTAL 3.7:- TV Fundamental Subtractive Colors Mixing If the respective color are formed by subtraction of color is known as subtractive mixing. It can developed by primary & secondary color by subtractive one or more than one color from white, Example: Red = white blue green, Green = white red blue, Blue = white red green

87 LECTURE 7 LECTURE :- TV FUNDAMENTAL 3.7:- Compression between Additive & Subtractive Mixing Additive mixing Addition of light from two or more colors is done in additive mixing. Here mixing of primaries result is white Additive primaries are, red, blue & green. Light from two or more colors from independent sources obtained through different filter. TV Fundamental Subtractive mixing Subtraction of parts is done from white. Mixing of subtractive primaries result is black. Subtractive primaries are cyan, magenta, & yellow. Reflecting properties of pigments are used in subtractive mixing

88 LECTURE 8 LECTURE :- TV FUNDAMENTAL 3.8:- TV Fundamental Composite Video Signal Picture information is not transmitted alone it is transmitted with blanking pulses and sync pulses, and this complete signal is called as Composite video signal. It can be represented either with positive polarity or negative polarity. Video signal along with picture information varies in accordance with the variation of intensity of light at various picture element. Average value for the whole picture frame is the DC value which represent background brightness of the picture

89 LECTURE 8 LECTURE :- TV FUNDAMENTAL 3.8:- TV Fundamental Fig 3.4 : Composite Video Signal [4] 89 89

90 LECTURE 9 LECTURE :- TV FUNDAMENTAL 3.9:- Blanking Pulse TV Fundamental Blanking pulse are used to blank retrace period of horizontal scanning as well as vertical scanning process in the transmitter and also in the receiver. In the absence of blanking,retrace will become visible on the screen and will cause distortion in the picture. In INDIA H-blanking pulse is 12 micro sec wide and H-sync pulse mounted on it is 4.7 micro sec wide. Width of V- blanking pulse is 1289 micro sec and of V-sync pulse mounted on it is 160 micro sec

91 LECTURE 9 LECTURE :- TV FUNDAMENTAL 3.9:- TV Fundamental Color Burst The subcarrier is suppressed in the modulated signal at transmitter, it is necessary to generate in the receiver for demodulation of the color signal. This signal generated must be of exactly same frequency and phase as that of the transmitter. To ensure this short wave of 8 to 10 pulse called color burst is sent to the receiver along with the sync signal. The burst signal acts as pilot carrier. Burst signal having 1) 8 to 10 cycle 2) Location at back porch of horizontal sync pulse 3) Duration of back porch is 5.8 micro sec 91 91

92 LECTURE 5:- 9 LECTURE TV FUNDAMENTAL 3.9:- TV Fundamental Chapter 3 Question Bank Explain additive color mixing. state grassmans law. What is color burst signal? why and where it added. Define the persistence of vision. how it helps in image continuity. Define the term hue and saturation in TV. Explain generation of g-y signal from UV signals. Draw CVS signal of 3 scanned lines. Explain additive mixing & subtractive mixing used in TV 92

93 LECTURE 9 LECTURE :- TV FUNDAMENTAL 3.9:- TV Fundamental Summary Concept of Aspect Ratio, Compatibility, and other characteristics. Concept of CVS (Composite video Signal) Concept of VSB (Vestigial Side band ) Concept of color theory 93 93

94 CHAPTER 4:- SYLLABUS Introduction and Audio signal Transmission Positive and Negative Modulation Introduction to Television Camera tube and its type 4 5 Colour picture tube Colour TV Transmitter 6 Colour TV Receiver. 94

95 CHAPTER-4 SPECIFIC OBJECTIVE / COURSE OUTCOME The student will be able to: 1 Introduction to Television Camera tube and its type 2 3 Introduction to Colour picture tube and its type Colour TV Transmitter and Colour TV Receiver 95

96 LECTURE 1 TV transmitter and receiver Introduction and Audio signal Transmission. Audio signal: The Signal Which carries only sound information is called audio information. A TV sound signal occupies somewhat less bandwidth in spectrum than in standard FM broadcast station. Video Signal: The Signal Which carries only picture information is called Video information. Advantage of frequency modulation: Noise reduction Transmitter efficiency Adjacent channel interference Co-channel interference 96 96

97 LECTURE 1 TV transmitter and receiver Introduction and Audio signal Transmission AM and FM : FM is not suitable for video transmission because due to multiple reception of FM, the ghost interference appear. as well as the bandwidth for FM is greater than that for AM. TV signal: The electrical equivalence of original information (audio or video) used for Transmitting information at longer distance in Television is Called TV signal. Signal bandwidth :The complete range of frequency of a TV signal is called signal bandwidth. The TV signal occupies a channel in the spectrum with a bandwidth of 7MHz

98 LECTURE 1 TV transmitter and receiver Positive and. Negative modulation Positive Modulation : When the intensity of picture brightness causes increase in amplitude of the modulated envelope, it is called positive modulation. Fig 1. Positive modulation[2] 98 98

99 LECTURE 1 Positive and Negative modulation. Negative Modulation: When the polarity of modulating video signal is so chosen that sync tips lie at the 100 percent level of carrier amplitude and increasing brightness produces decrease in the modulation envelope, it is called negative modulation. Modulating signal TV transmitter and receiver Carrier signal Fig 2. negative modulation[2] 99 99

100 LECTURE 1 TV transmitter and receiver Merit and. demerit of negative modulation Negative modulation is preferred for video signal transmission over positive modulation for following reasons Effect of noise interference on picture signal. Effect of noise interference on synchronization. Peak power available from the transmitter. Use of AGC (Automatic Gain Control) circuits in the receiver

101 LECTURE 1 TV transmitter and receiver Merit and. demerit of negative modulation Merit: The merits of negative modulation over positive modulation, so far as picture signal distortion and AGC voltage source are concerned, have led to the use of negative modulation in almost all TV systems now in use. Demerit: Disadvantage of negative modulation is that as sync. Pulses are affected by noise there will be loss of horizontal or vertical synchronization which result in diagonal and vertical rolling of picture

102 LECTURE 2 TV transmitter and receiver. Introduction to Television Camera tube and its type A TV camera tube may be called the eye of a TV system. For such an analogy to be correct the tube must possess characteristic that are similar to its human counterpart. Some of the more important functions must be, Sensitivity to visible light. Wide dynamic range with respect to light intensity. Ability to scene. resolve details while viewing a multi element

103 LECTURE 2 TV transmitter and receiver Television camera tube. Basic principle: An electron tube use a light-sensitive material/receptor that converts an optical image into an electrical television video signal. The tube is used in a television camera to generate a train of electrical pulses representing the light intensities present in an optical image focused on the tube. An electrical signal corresponding to the amount of light at that point of the optical image is generated by the tube. This signal represents the video or picture portion of a television signal

104 LECTURE 2 Television Camera tube. Photoelectric Effects The two photoelectric effects used for converting variations of light intensity into electrical variations are (i) photoemission and (ii) photoconductivity. Photoemission: TV transmitter and receiver Certain metals emit electrons when light falls on their surface. These emitted electrons are called photoelectrons and the emitting surface a photocathode. Light consists of small bundles of energy called photons

105 LECTURE 2 TV transmitter and receiver The number. of electrons which can overcome the potential barrier and get emitted,depend on the light. Alkali metal are used as photocathode because they have very low work function. Fig3. Photoemission[2]

106 LECTURE 3 TV transmitter and receiver Photoconduction In some metal., when light photon fall on it then its conductivity / resistivity change. Semiconductor metals like selenium, tellurium and lead with their oxide have this property known as photoconductivity. The variation of resistance at each point across the surface of the material is utilized to develop a varying signal by scanning it uniformly with an electron beam. Fig4. photoconduction[2]

107 LECTURE 3 TV transmitter and receiver. Types of Camera Tubes Image Orthicon tube Vidicon Plumbicon

108 LECTURE 3 TV transmitter and receiver Image. orthicon tube Principle : Photo emissive It has three section: - Image section - Scanning section - Electron gun cum-multiplier section

109 LECTURE 3 TV transmitter and receiver Image orthicon. tube Fig 5. Image Orthicon tube

110 LECTURE 3 TV transmitter and receiver Image orthicon. tube Glass plate : coated with Silver-antimony serve as photocathode. Lens assembly : light from the scene to be televised is focused on the photocathode surface by lens system. Photocathode surface is semitransparent and light rays penetrate it to reach its inner surface where electron emission takes place. Target plate : when electron emit from cathode,it can not store charge being a conductor

111 LECTURE 3 TV transmitter and receiver. Image orthicon tube For this reason the electron image is made to move towards the target plate located at short distance from it. The target plate is made of a very thin sheet of glass and can store charge received by it. This is maintained at about 400v more +ve w.r.t photocathode When electron move from cathode to target plate there is chance that it may repel each other,this can result in distortion of the information available as charge image

112 LECTURE 3 Image orthicon tube. TV transmitter and receiver To prevent this divergence effect an axial magnetic field generated by focus is employed. This magnetic field impart helical motion to electrons and focus them on target plate. The image side of target plate has coating of cesium that emit secondary electron. these secondary electron is collected by wire mesh which is located at front of target plate. The +ve charge appeared on target plate is proportional to light intensity distribution on photocathode

113 LECTURE 4 TV transmitter and receiver Scanning. section Fine electron beam Focus,alignment coil Deflection coil - Horizontal deflection - Vertical deflection

114 LECTURE 4 TV transmitter and receiver Electron. gun assembly and multiplier Electron gun Multistage electron multiplier

115 LECTURE 4 TV transmitter and receiver. Vidicon Principle : Photoconductive It has three section: - Target section - Scanning section - Electron gun

116 LECTURE 4 TV transmitter and receiver Vidicon. Fig 6. vidicon

117 LECTURE 4 TV transmitter and receiver Target. section Glass plate Lens assembly Fig 7. Target section

118 LECTURE 4 TV transmitter and receiver Fine electron beam Focus.,alignment coil Deflection coil - Horizontal deflection - Vertical deflection Fig 8.Electode and coil arrangement in vidicon and plumbicon

119 LECTURE 4 TV transmitter and receiver Electron gun. assembly Electron gun Fig 9.Electode and coil arrangement in vidicon and plumbicon

120 LECTURE 4 TV transmitter and receiver Principle of operation. Fig 10. Equivalent circuit of Target tube

121 LECTURE 4 TV transmitter and receiver Application. of vidicon Earlier type of vidicon were used only where there was no fast movement, because of inherent lag. These application involved: - Slides - Pictures - Closed circuit TV etc. The present day improved vidicon find wide application in - Education - Medicine - industry - Aerospace - Scanography

122 LECTURE 5 TV transmitter and receiver Plumbicon. Camera Tube lower image lag. It has fast response and produce high quality pictures at low light level. It has small size and light weight and has low power operating characteristics. It is similar to vidicon tube except small change in target plate

123 LECTURE 5 TV transmitter and receiver Plumbicon Camera Tube. Fig 11.Electode and coil arrangement in vidicon and plumbicon

124 LECTURE 5 TV transmitter and receiver Intrinsic layer Fig 12. Target plate

125 LECTURE 6 TV transmitter and receiver Generation of the colour signal. Plan of a colour television camera showing generation of colour signals and Y matrix for obtaining the luminance (brightness) signal. Fig 13. Generation of the colour signal

126 LECTURE 6 TV transmitter and receiver Figure shows. a simple block schematic of a colour TV camera. It essentially consists of three camera tubes in which each tube receives selectively filtered primary colours Each camera tube develops a signal voltage proportional to the respective colour intensity received by it. Light from the scene is processed by the objective lens system. The image formed by the lens is split into three images by means of glass prisms

127 LECTURE 6 TV transmitter and receiver These prisms are designed as diachroic mirrors.. A diachroic mirror passes one wavelength and rejects other wavelengths (colours of light). Thus red, green, and blue colour images are formed. The rays from each of the light splitters also pass through colour filters called trimming filters. These filters provide highly precise primary colour images which are converted into video signals by image-orthicon or vidicon camera tubes. Thus the three colour signals are generated. These are called Red (R), Green (G) and Blue (B) signals

128 LECTURE 6 TV transmitter and receiver Solid State camera based on CCD. CCD (Charged coupled device) in conventional camera tube scanning was done by deflection a beam of electrons horizontally and vertically with the help of saw tooth currents flowing through the respective deflection coil in a cathode ray tube. The CRT is a thermionic device and hence is bulky, costly, require high voltages and less durable. With the development of large scale integration circuit, it becomes possible to etch extremely small photodiode onto a chip by X-ray using photolithography process and thus design a fully solid state video camera

129 LECTURE 6 TV transmitter and receiver Solid State. camera based on CCD Photodiode is sensitive to light when light from a scene strike it, electron are generated. There no. is proportional to the intensity of light. The operation of a solid state image scanner is based on the functioning of CCDs which can store and transfer the analog charge signals. Used in digital camera

130 LECTURE 6 TV transmitter and receiver. Fig14. Solid State camera based on CCD[2]

131 LECTURE 7 TV transmitter and receiver Colour television. display tubes Based on the gun configuration and the manner in which phosphors are arranged on the screen, three different types of colour picture tubes have been developed. These are: Delta-gun colour Picture tube Guns-in-line or Precision-in-line (P-I-L) colour picture tube. Single sun or Trintron Colour picture tube

132 LECTURE 7 TV transmitter and receiver Delta-gun colour picture tube. Fig15. Delta-gun colour picture tube[2]

133 LECTURE 7 TV transmitter and receiver. Delta-gun colour picture tube It employs three separate guns one for each phosphor. The guns are equally spaced at 120 interval with respect to each other and tilted inwards in relation to the axis of the tube. Each phosphor dot corresponds to one of the three primary colours. The mask has one hole for every phosphor dot triad on the screen

134 LECTURE 7 TV transmitter and receiver Delta-gun. colour picture tube The various holes are so oriented that electrons of the three beams on passing through any one hole will hit only the corresponding colour phosphor dots on the screen. higher anode voltages are needed in colour picture tubes than are necessary in monochrome tubes. The ratio of the electron passing through the holes to those reaching shadow mask is only 20%

135 LECTURE 8 TV transmitter and receiver Precision-in-line. (p.i.l.) Colour picture tube This tube as the name suggests has three guns which are aligned precisely in a horizontal line. The in-line gun configuration helps in simplifying convergence adjustments. One vertical line of slots is for one group of fine strips of red green and blue phosphors. Since all the three electron beams are on the same plane, the beam in the centre (green) moves along the axis of the tube

136 LECTURE 8 TV transmitter and receiver Precision-in-line. (P.I.L.) Colour picture tube Fig16. Precision-in-line (p.i.l.) Colour picture tube[2]

137 LECTURE 8 TV transmitter and receiver Precision-in-line (p.i.l.) Colour picture tube. However, because of inward tilt of the right and left guns the blue and red beams travel at an angle and meet the central beam at the aperture grille mask. The P.I.L. tube is more efficient, i.e., has higher electron transparency and needs fewer convergence adjustments on account of the in-line gun structure. It is the most used tube in the present day colour receiver

138 LECTURE 8 TV transmitter and receiver Trinitron Colour. picture tube The Trinitron or three in-line cathodes colour picture tube was developed by SONY Corporation of Japan around It employs a single gun having three in-line cathodes. This simplifies constructional problems since only one electron gun assembly is to be accommodated. The three phosphor triads are arranged in vertical strips as in the P.I.L. tube. Each strip is only a few thousandth of a centimeter wide

139 LECTURE 8 TV transmitter and receiver Trinitron Colour picture tube. Fig15. Trinitron Colour picture tube[2]

140 LECTURE 8 TV transmitter and receiver Trinitron Colour picture tube. A metal aperture grille like mask is provided very close to the screen. It has one vertical slot for each phosphor triad. The grille is easy to manufacture and has greater electron transparency as compared to both delta-gun and P.I.L. tubes. the beams have a common focus plane a sharper image is obtained with good focus over the entire picture area. All this simplifies convergence problems and fewer adjustments are necessary

141 LECTURE 9 TV transmitter and receiver Colour TV receiver. Fig16. Colour TV receiver

142 LECTURE 9 TV transmitter and receiver Colour TV receiver Tuner: The. purpose of the tuner is to amplify both sound and picture signals Picked-up by the antenna and to convert the signal frequencies into intermediate frequencies and their sidebands. AFT: AFT circuit actually controls the local oscillator frequency to obtain a picture. Video Signal Paths: It is necessary to increase the level of detected video signal before feeding into various sections of the receiver. Delay Line: It is provided to reproduce the brightness and colour information at the same time for any element of the picture

143 LECTURE 9 TV transmitter and receiver Colour TV receiver. IF Amplifier :It amplifies the IF signal, as IF is much lower than the signal frequency and is fixed, the IF amplifier has high stable gain and high selectivity. Video Detector : It is a enveloped detector using diode, by process of rectification and filtering, detect the baseband signal of CVS and frequency modulated intercarrier frequency (5.5 MHz) The standard o/p of video detector is 1v peak to peak. Automatic gain control : Its function is to control the gain of RF & IF amplifier to reduced the differenced between o/p for strong and weak signal to maintained constant o/p signal

144 LECTURE 9 TV transmitter and receiver. Colour TV receiver. Sync separator : Signal extracted from the video detector goes to a sync separator stage. The H-sync and V-sync pulses are further separated from each other by using differentiating and integrating circuits. Vertical sweep generator : The V-sync pulse trigger the V- sweep generator so that it start at the right time. Its frequency is 50 Hz. V-sweep amplifier : V-sweep is amplified by buffer amplifier, driver amplifier and the o/p power amplifier

145 LECTURE 9 TV transmitter and receiver Colour TV receiver. Horizontal sweep generator : H-sweep frequency is timed and controlled by H-sync pulse through AFC circuit. AFC is comparator circuit which compare the H-sync frequency with the sweep generator frequency. H-sweep amplifier : The H-sweep is amplified by buffer, driver and power amplifier stages. Sound section : Intercarrier frequency amplifier It receives frequency modulated intercarrier frequency of 5.5 MHz through the trap circuit, and amplifies it

146 LECTURE 9 TV transmitter and receiver Colour TV receiver. FM detector : It consist of a limiter and phase shift discriminator. It work on the principle of shift in phase when the i/p frequency changes with respect to the resonant frequency of a resonant circuit. Audio voltage amplifier : Audio signal is amplified by RC coupled audio voltage amplifier De-emphasis The audio signal goes through de-amphasis for high audio frequencies for high signal to noise ratio. Audio power amplifier : This is final amplifier which gives sufficient power o/p to drive the loudspeaker system of the TV receiver. Generally it is push pull type amplifier

147 LECTURE 9 TV transmitter and receiver Colour TV transmitter. Fig17. Colour TV transmitter

148 LECTURE 9 TV transmitter and receiver Colour TV transmitter. VSB Filter The modulator o/p is of double sideband type, which is converted into VSB type by a sharp filter. The filter is design so that it passes the carrier and the upper sideband i.e carrier frequency +5 MHz full without attenuation. The lower sideband produced up to 0.75 MHz below the carrier frequency, thereafter it is sharply attenuated. The signal achieved called as AMVSB signal. Frequency Multiplier : The crystal oscillator cannot directly produced VHF or UHF range frequencies. The frequency multiplier are used to get the desired channel frequency called video carrier

149 LECTURE 9 TV transmitter and receiver Colour TV transmitter. FM modulator Low level modulation is used before the final power amplifier to save audio power requirement. As a crystal is used to generate carrier frequency, direct frequency modulation is not suitable because it would be difficult to vary the frequency of a crystal. Audio carrier generator It uses a crystal oscillator which is highly stable due to its Q being very high. It generate very low radio frequency

150 LECTURE 9 Chapter 4 Question Bank 1. Differentiate between Positive and Negative Modulation. 2. State the working principle of PIL colour picture tube with diagram. 3. Describe construction and working of plumbicon camera tube 4. Explain delta gun picture tube. 5. Explain the working of Vidicon Camera tube. 6. Explain preference of FM over AM for sound signal 7. Draw and Explain the block diagram of colour Tv receiver. 8. Draw and Explain the block diagram of colour Tv Transmitter. 150

151 LECTURE 9 TV transmitter and receiver SUMMARY Concept of Positive and Negative Modulation Concept of Television Camera tube and its type Concept of Colour picture tube and its type Concept of Colour TV Transmitter and Colour TV Receiver

152 CHAPTER 5:- SYLLABUS 1 2 Introduction & Pal-D Decoder Yagi-Uda Antenna. 3 Chroma signal Amplifier & Burst Pulse Blanking 4 Colour Killer Control Circuit & Separation of U & V Signals 5 ACC Amplifier & Colour Signal Matrixing 6 RGB Drive Amplifier 152

153 CHAPTER 5:- SYLLABUS 7 8 EHT Generation Introduction to HDTV. 9 LCD TV & LED TV Technology 153

154 CHAPTER-5 SPECIFIC OBJECTIVE / COURSE OUTCOME The student will be able to: 1 Introduction & Pal-D Decoder & Yagi-Uda Antenna. 2 Colour Killer Control Circuit & Separation of U &V Signals 3 RGB Drive Amplifier, EHT Generation, LED,LCD. 154

155 LECTURE 1 Colour TV Introduction Television means to see from a distance. In the early years of the twentieth century many scientists experimented with the idea of using selenium photosensitive cells for converting light from pictures into electrical signals and transmitting them through wires. The function of PAL-D decoder is conversion of chrominance signal into U, V signal and then to corresponding R,G,B signal. The Process is done only by using single IC

156 LECTURE 1 Pal-D Decoder Colour TV Chroma signal selection: select the chrominance signal and rejects all other unwanted components of the composite signal. Color Killer Circuit: As the name suggests this circuit becomes ON and disables the Chroma amplifier during monochrome reception. Sync Demodulator: The output from adder and sub tractor from adder and subtractor consists of two independent DSBSC RF signals (U and V). Color difference amplifier and matrixing: Three color difference signals amplified and fed to appropriate grids of the picture tube

157 LECTURE 1 PAL-D Decoder Colour TV Fig1: Block Diagram of Pal-D Decoder

158 LECTURE 1 Pal-D Decoder Colour TV Burst gate amplifier: separate the colour burst from the chrominance signal. Reference oscillator: generate exactly right frequency with same phase reference as the original colour subcarrier. Automatic phase control: compare the burst and locally generated subcarrier to develop a control voltage. Burst phase discriminator: give the output as subcarrier oscillator control voltage and pulse having indent signal. PAL delay line: Averaging and separate U & V modulation signal. Adder and Substractor: U & V signal go to adder and subs tractor stage directly as well as through delay line

159 LECTURE 2 Colour TV Yagi-Uda Antenna The antenna is mounted on a suitable structure at a height around 10 meters above the ground level. Try changing the height of the antenna to obtain maximum signal strength & Rotate the antenna to check against ghost images and reception of signals from far-off stations. Fig2. yagi-uda antenna

160 LECTURE 2 Colour TV Yagi-Uda Antenna The antenna widely used with television receivers for locations within 40 to 60 km from the transmitter is the folded dipole with one reflector and one director. This antenna provides a gain close to 7 db and is relatively unidirectional as seen from its radiation pattern. The receiving antenna is mounted horizontally for maximum pick-up from the transmitting antenna. The antenna elements are normally made out of 1/4 (0.625 cm) to 1/2 (1.25 cm) di aluminum pipes of suitable strength

161 LECTURE 3 Colour TV Chroma signal Amplifier Stage 1: Q1 gets input from its base via. Capacitor c1. gain of this stage is decided by reactance of L1 and magnitude of ACC controlling voltage fed at base of Q2 through R1 and R2. C2 avoids undesirable feedback between Q1 and ACC amplifier. Output signal at collector of Q1 is typically 0.5v peak to peak. Output of stage 1 is given to stage 2 via. C6 and to the burst preamplifier through C5. Stage 2: This amplifier consists of transistors Q2 and Q3.Q2 acting as emitter follower. Q3 works as phase splitting amplifier whose purpose is to provide antiphase chroma signal for chroma delay line circuit which separated u and v signals

162 LECTURE 3 Colour TV Chroma signal Amplifier Color saturation control circuit: function of saturation control circuit is to form variable attenuator to change magnitude of chorma signal which is fed to U &V demodulator. Burst pulse blanking: the function of diode D3 D4 and R18 in chorma amplifier is to prevent colour burst pulse from getting through 2 nd stage of chorma amplifier. Color killer control: upper end of R10 is connected to positive voltage generate by colour killer circuit on rectification of burst pulses. When colour signal is received bias voltage is 12v. This make Q2 on and ensure flow of chorma signal to Q

163 LECTURE 3 Colour TV Fig3: Chroma Signal Amplifier Circuit

164 LECTURE 4 Colour TV Burst Pulse Blanking The output from the video preamplifier is fed to the first stage of chorma band pass amplifier through an emitter follower stage Q1. Negative going horizontal blanking pulse are coupled to the base of Q1 through diode D1. The pulse Drive Q1 into cut off during colour burst intervals and thus prevent it from reaching the demodulator. 164

165 LECTURE 4 Colour TV Fig4: Colour Burst Blanking Circuit 16 5

166 LECTURE 5 Colour TV Color Killer Control The dc operating voltage to Q9 is applied Via center lap on L4. Such a connection cause L4 to function as a autotransformer and enable a waveform of about 24v to be developed at collector of Q9. This waveform is fed to the C30 to D10 which function as rectifier. R62 and C33 form a low pass filter which provide a steady dc about 13.5v as the output. This prevent any stray colour signal reaching R,G,B amplifier and hence no colour noise appear on black and white picture during monochrome transmission

167 LECTURE 5 Colour TV Fig5: Colour Killer Control Circuit

168 LECTURE 6 Colour TV Separation of U and V Signals Chroma signal is applied to Q1. Amplified chroma signal is applied to delta line through transformer T1. The signal after passing through he delay line across A winding of transformer T2. As the T2 is centre tapped with equal turn the voltage induced by the signal from delay line will be equal in amplitude but apposite in phase. On the other hand direct signal will include voltages with same phase in both A and B windings. 168

169 LECTURE 6 Colour TV Fig6: Circuit For Separating U and V Signals 169

170 LECTURE 7 ACC Amplifier Colour TV Burst pulse is fed to ACC amplifier diode D8 and R43, C21 and C22 forms half wave rectifier and filter circuit. It provides negative d.c. voltage which is proportional to amplitude of received signal. Output of Q7 is positive voltage which changes with amplitude of chroma signal. This voltage is normally 7v. It is given to the 1 st chorma amplifier to control its gain. Purpose of R46 & R47 is to obtain correctly steady bias for the 1 st chorma amplifier. 170

171 LECTURE 7 Colour TV ACC Amplifier Circuit Fig7: ACC Amplifier Circuit 171

172 LECTURE 8 Colour TV Colour Signal Matrixing As we know R,G,B matrixing is used in modern colour receivers. The view is to explain the technique of obtaining R,G,B signal of sufficient amplitude from the weighted U and V signals. The output is taken at Emitter follower Q7 In this way at receiver color matrixing circuit convert U,V and Y signal to R G B signal

173 LECTURE 8 Colour TV Color Signal Matrixing Fig8: Color Signal Matrixing Circuit 173

174 LECTURE 9 Colour TV RGB Drive Amplifier The video amplifier system intended for high resolution RGB color monitor applications. In addition to three matched video amplifiers, the video amplifier contains three gated differential input black level clamp comparators for brightness control and three matched attenuator circuits for contrast control. The video amplifier also contains a voltage reference for the video inputs. 174

175 LECTURE 9 RGB Drive Amplifier Colour TV Fig9: RGB Drive Amplifier 175

176 LECTURE 10 Colour TV RGB Drive Amplifier Features: Three wideband video amplifiers (70 b3db) Inherently matched (g0.1 db or 1.2%) attenuators for contrast control Three externally gated comparators for brightness control Provisions for independent gain control (Drive) of each video amplifier Video input voltage reference Low impedance output 176

177 LECTURE 9 Colour TV RGB Drive Amplifier Applications: High resolution RGB CRT monitors Video AGC amplifiers Wideband amplifiers with gain and DC offset controls

178 LECTURE 10 EHT Generation The term high voltage usually means electrical energy at voltages high enough to inflict harm. Equipment and conductors that carry high voltage warrant particular safety requirements and procedures. High voltage is used in electrical power distribution in cathode ray tube, to generate X-ray and particle beam to demonstrate arcing, for ignition, in photomultiplier tube and in high power amplifier vacuum tube and other industrial and scientific applications. 178

179 LECTURE 10 EHT Generation Colour TV Fig10 : EHT Generation 179

180 LECTURE 11 : HDTV High-definition television (HDTV) provides a resolution that is substantially higher than that of standard definition television Early HDTV broadcasting used analog technology, but today it is transmitted digitally and uses video compression. HDTV technology was introduced in the United States in the late 1980s and made official in 1993 by the digital HDTV, grand alliance a group of television, electronic equipment, 180

181 LECTURE 11 HDTV HDTV broadcast systems are identified with three major parameters: Frame size in pixels is defined as number of horizontal pixels number of vertical pixels, for example or Often the number of horizontal pixels is implied from context and is omitted, as in the case of 720p and 1080p. Scanning system is identified with the letter p for progressive scanning or i for interlace scanning. Frame rate is identified as number of video frames per second. For interlaced systems the number of frames per second should be specified, but it is not uncommon to see the field rate 181

182 LECTURE 12 LCD A liquid-crystal display (LCD) is a flat panel display, electronic visual display, or video display that uses the light modulating properties of liquid crystal. Liquid crystals do not emit light directly. Each pixel of an LCD typically consists of a layer of molecules aligned between two transparent electrode, and two polarizing filter (parallel and perpendicular), the axes of transmission of which are (in most of the cases) perpendicular to each other LCD panels produce no light of their own, they require external light to produce a visible image. 182

183 LECTURE 12 Colour TV LCD Advantages: Very compact and light. Very little heat emitted during operation, due to low power consumption. The possible ability to have little or no flicker depending on backlight technology. Usually no refresh-rate flicker, because the LCD pixels hold their state between refreshes. Is very thin compared to a CRT monitor, which allows the monitor to be placed further back from the user, reducing close-focusing related eye-strain. 183

184 LECTURE 12 : Disadvantages: LCD Loss of contrast in high temperature environments. Not usually designed to allow easy replacement of the backlight. Poor display in direct sunlight, often completely unviewable. Cannot be used with light gun/pen. Hard to read when wearing polarized sunglasses. Loss of brightness and much slower response times in low temperature environments.. 184

185 LECTURE 12 What are the different types of LCD? LCD Transmissive LCD :The Transmissive LCD is illuminated from one side and viewed from the opposite side. Activated cells appear dark and inactive cells appear bright. One disadvantage of Transmissive LCD is that lamp used to illuminate the LCD consumes more power than consumed by the LCD itself. Reflective LCD : This is commonly used in pocket calculators and digital watches. It is viewed by ambient light reflected in a mirror behind the display. They have lower contrast than the Transmissive type, because the ambient light passes twice through the display before reaching the viewer. The advantage is that there is no lamp to consume power, so the battery life is long. 185

186 LECTURE 12 LED An LED display is a flat panel display which uses an array of light emitting diode as a video display An LED panel is a small display, or a component of a larger display. The first true all-led flat panel television screen was possibly developed, demonstrated and documented by James P. Mitchell in 1977 There are two types of LED panels: conventional (using discrete LEDs) and surface mounted device(smd) panels A cluster of red, green, and blue diodes is driven together to form a full-color pixel, usually square in shape. 186

187 LECTURE 12 Colour TV LED TV Technology: The LED TV is more advanced version of LCD TV The LED TV use LCD panel with LED backlighting. An LED diode. TV illuminate its LCD panel with light Emitting Specifically this current flow between anode which are positively charged electrode and LED cathode which are negatively charged electrode. In contrast a traditional LCD utilizes fluorescent lamp for backlighting. 187

188 LECTURE 12 Chapter 5 Question Bank 1. explain Pal-D Decoder with its block diagram. 2. explain basic principle of Yagi-Uda Antenna. 3. Write short note on Colour Killer Control Circuit 4. Explain Separation of U & V Signals 5. Explain Concept of RGB Drive Amplifier 6. draw the circuit diagram and Explain operation of EHT Generation. 7. Explain Concept of Chroma signal Amplifier 8. Explain Burst Pulse Blanking 9. Explain Concept of ACC Amplifier 10. Explain Colour Signal Matrixing 11. Explain the concept of LCD. 12.Write short note on LED. 188

189 LECTURE 12 Colour TV SUMMARY Concept of Pal-D Decoder & Yagi-Uda Antenna. Concept of Colour Killer Control Circuit & Separation of U & V Signals Concept of RGB Drive Amplifier EHT Generation LED LCD Concept of Chroma signal Amplifier & Burst Pulse Blanking Concept of ACC Amplifier & Colour Signal Matrixing

190 CHAPTER 6:- SYLLABUS 1 2 Introduction to Cable TV and cable signal sources Cable TV system component 3 4 MATV and CATV CCTV and video monitor for CCTV 5 Direct to home service(dth) 6 DHT service provider and db meter 190

191 CHAPTER-6 SPECIFIC OBJECTIVE / COURSE OUTCOME The student will be able to: 1 Cable TV system component 2 MATV CATV and CCTV 3 Direct to home service(dth) & db meter 191

192 LECTURE 1 Cable TV Introduction to cable TV Basically cable TV system is classified as 1) MATV(master antenna TV) 2) CCTV(close circuit TV) 3) CATV(cable TV) Cable TV was initially introduce for the benefit is possible of communication in rural area that were beyond the range of broadcast transmission However with the advent of satellite television, reception of signal from a large number of TV station located far away become possible. With this cable TV developed in a complex multi channel 192 system and expanded in a big way in all countries. 192

193 LECTURE 1 Cable TV Cable signal. resources The first step in cable TV is to collect the desired signal from available source The main signal coming from various satellite. for that purpose high gain antenna is required. By correct adjustment of this antenna towards satellite, collect signal arriving from it by dish and deliver these to LNBC. this minimize the losses in co axial cable

194 LECTURE 1 Cable TV. Cable TV system component Dish antenna: For application where very high gain and very narrow bandwidth are needed the parabolic dish antenna is use. This antenna provide the required gain and bandwidth. Principle: the parabolic reflector collects all the electromagnetic waves from satellite due to parabolic shape reflected rays concentrated at focal point which give the high gain signal

195 LECTURE 1 Cable TV. Fig1: Geometry of Parabola

196 LECTURE 1 Cable TV. Specification of Dish Antenna: Size-8feet. Gin-36db. Band-c(3.7 to 4.2GHz downlink frequency) Look angle-360 rotation in azimuth. Offset angle-24.62limit Focal length-90cm Azimuth angle= 0 to 360 Aperture efficiency-75%

197 LECTURE 2 Cable TV LNBC The main. function of LNBC is to convert the electrical signal to a low frequency range to minimize losses in co axial cable that carry dish antenna signal to control room. working principle: LNBC down convert the GHz Frequency into MHZ Also to reject the noise and increase the gain of the signal Fig2: Block diagram of LNBC

198 LECTURE 1 Cable TV. Specification of LNBC Input frequency to 4.2 GHz output frequency-950 to 1525 GHz Local oscillator frequency-5150mhz Impeadance-75 ohm

199 LECTURE 2 Cable TV Multiplexer. Multiplexer means many input give only one output simultaneously. Multiplexer is a linear mixer and all the signal are simply added together algebraically. the resultant output signal is a composite of all the channel carrier and their modulation product. i/p signal from modulator Signal composite signal Fig3: Concept of signal multiplexing

200 LECTURE 2 Cable TV. Multiplexer Specification Frequency response- flat upto 550MHz Insertion loss- less than 3 db Isolation-35db Input to output-12:

201 LECTURE 2 Cable TV Connectors To make. the connection between cable or to amplifier splitter and tap offs, it is necessary to use good quality whether proof co-axial connector. Such a loss of signal not only causes interference in reception on TV sets in many way but also necessities installation of more line amplifier. Fig4: cable connector