1. Synchronization circuit
This circuit to pick only SYNC sygnal composite video signal, amplify and rectify it, also to deliver both vertical and horizontal SYNC signals to each deflection circugt sytem.
2. Vertical deflection circuit
Minggu, 12 April 2009
Kamis, 09 April 2009
Color TV receiver
1. How are signals transmitted
The following 4 signal are included in electric wave of one channel which is transmitted by broadcasting stations.
- Picture signal
- SYNC signal
- Color signal
- Sound signal
They consist of picture sìgnal, which pick up video signal out of transmitted from broadcasting station and catch it by antena, circuits of synchronization and deflection, which compose pictures, circuits of color sìgnal reproduction.
2. Operation of each block
3. Circuit of video signal
》3.1 Tuner
Tuner operates to selec necessary wave out of some TV electric wave , amplify it, and convert it into intermediate frequency signal ( 58.75MHz for video, 54.25MHz for sound ). Tuner of input tuning, high frequency amplification, mixture and local oscilation. And is classified into VHF use according to receiving frequency band.
Assuming that chanel 1 is comes through antena, video carrier is 91.25MHz and sound carrier is 95.75MHz.While chanel 1 is received, local oscillating by 150MHz.
>>150MHz ― 91.25MHz = 58.75MHz
>>150MHz ― 95.75MHz = 54.25MHz
3.2 Automatic frequency setting ( AFS ) circuit
This circuit is to prevent oscillation frequency at local oscillator of tuner from drifting by change of temperature , it operates to detect the deviation of picture intermediate frequency of 58.75MHz, generate control voltage and apply it to variable capacitance diode, consequently correcting oscillation frequency.
3.3 Picture intermediate frequency ( picture IF ) amplification circuit
This is composed of 3 and 4 step tuning amplifier, where most part of gain which is necssery for received is obstainf.
3.4 Picture detection circuit
Is circuit operates to pick up composite video signal out of video intermediate frequency whic amplified by picture IF amplification.Composite video signal is a composite signal consisting video ( brightness ) signal , SYNC signal, chrominance carrier video.
3.5 Video amplification circuit
Is circuit operates to amplify composite video signal and signal for picture tube. It requires wide band characteristic to evenly frequency from direct current to nearly 4MHz.This circuit also has supplementary circuits such as delay element to video signal and chrominance signal in time, contrast, brightness and picture quality.
3.6 AGC ( Automatic Gain Control ) circuit
TV design section
The following 4 signal are included in electric wave of one channel which is transmitted by broadcasting stations.
- Picture signal
- SYNC signal
- Color signal
- Sound signal
They consist of picture sìgnal, which pick up video signal out of transmitted from broadcasting station and catch it by antena, circuits of synchronization and deflection, which compose pictures, circuits of color sìgnal reproduction.
2. Operation of each block
3. Circuit of video signal
》3.1 Tuner
Tuner operates to selec necessary wave out of some TV electric wave , amplify it, and convert it into intermediate frequency signal ( 58.75MHz for video, 54.25MHz for sound ). Tuner of input tuning, high frequency amplification, mixture and local oscilation. And is classified into VHF use according to receiving frequency band.
Assuming that chanel 1 is comes through antena, video carrier is 91.25MHz and sound carrier is 95.75MHz.While chanel 1 is received, local oscillating by 150MHz.
>>150MHz ― 91.25MHz = 58.75MHz
>>150MHz ― 95.75MHz = 54.25MHz
3.2 Automatic frequency setting ( AFS ) circuit
This circuit is to prevent oscillation frequency at local oscillator of tuner from drifting by change of temperature , it operates to detect the deviation of picture intermediate frequency of 58.75MHz, generate control voltage and apply it to variable capacitance diode, consequently correcting oscillation frequency.
3.3 Picture intermediate frequency ( picture IF ) amplification circuit
This is composed of 3 and 4 step tuning amplifier, where most part of gain which is necssery for received is obstainf.
3.4 Picture detection circuit
Is circuit operates to pick up composite video signal out of video intermediate frequency whic amplified by picture IF amplification.Composite video signal is a composite signal consisting video ( brightness ) signal , SYNC signal, chrominance carrier video.
3.5 Video amplification circuit
Is circuit operates to amplify composite video signal and signal for picture tube. It requires wide band characteristic to evenly frequency from direct current to nearly 4MHz.This circuit also has supplementary circuits such as delay element to video signal and chrominance signal in time, contrast, brightness and picture quality.
3.6 AGC ( Automatic Gain Control ) circuit
TV design section
Rabu, 08 April 2009
Color TV Broadcasting
1. Principle of color TV
At broadcasting station of color tv, subjects are taken pictures in sparated condition into the 3 color primaries by using red, green and blue exlusive cameras. The pictures are camera is received by red picture tube, signal of green camera is received by picture tube,and that of blue is by blue picture tube. Then these 3 picture are piled so that the same image as the subject is reproduced.
2. System of color TV
When color TV is devised, black and white tv receivers have alreardy prevailed widely. So, the following items of compatibility were required.
a. Color tv receiver can receive black and white broadcasting.
b. Black and white tv receivers can receive color broadcasting with black and white picture.
This is called NTSC system, which is standdard system of color tv in Japan. Later, PAL system and SECAM system are develoved in Europa,and are used in many countries as standard.
3. Signal for color TV
Sensitivity of human eyes to red, green and blue is a ratio. So, assuming red mary signal is Er ,green is Eg , and blue is Eb, brightness signal Ey .
Order to make 3 primaries by combining it with brightness sìgnal and apply them to picture tubes, color difference signals, Er-Ey , Eg- Ey , Eb- Ey.
》Er- Ey = 0.70Er- 0.59Eg - 0.11Eb ...
》Eg-Ey =- 0.30Er+0.41Eg- 0.11Eb...
》Eb-Ey = -0.30Er- 0.59Eg+ 0.89Eb...
Accordingly, it only need that these 3 signal of brightness signal Ey and 2 color difference signals, Er- Ey, Eb- Ey are transmitted.These 3 signal are called transmission 3 signal components.
4. How to transmit color TV signal
In color TV, all the sìgnals should be transmitted within the band of 6MHz as well as black and white TV. The brightness signal ( Ey ) is multiplied to two color difference signal ( Er- Ey, Eb- Ey ).
5. Multiplication of crominance signal
The 2 color difference signal is transmitted by carrier of 3.58 MHz called chrominance sub-carrier two-phase modulation method is used for the transmission.That is, Eb-Ey and Er-Ey are applied to a balance modulator, and they are balance modulated separately by color sub carrier with phase difference of 90' then, these 2 are composed to be transmitted as chrominance signal.
6. Multiplication of brightness signal and chrominance sìnal
In order to multiply chrominance signal which has the band within +-0.5MHz of 3.58MHz and brightness signal having the band approximately 4MHz.
7. Composite color TV signal
At broadcasting station of color tv, subjects are taken pictures in sparated condition into the 3 color primaries by using red, green and blue exlusive cameras. The pictures are camera is received by red picture tube, signal of green camera is received by picture tube,and that of blue is by blue picture tube. Then these 3 picture are piled so that the same image as the subject is reproduced.
2. System of color TV
When color TV is devised, black and white tv receivers have alreardy prevailed widely. So, the following items of compatibility were required.
a. Color tv receiver can receive black and white broadcasting.
b. Black and white tv receivers can receive color broadcasting with black and white picture.
This is called NTSC system, which is standdard system of color tv in Japan. Later, PAL system and SECAM system are develoved in Europa,and are used in many countries as standard.
3. Signal for color TV
Sensitivity of human eyes to red, green and blue is a ratio. So, assuming red mary signal is Er ,green is Eg , and blue is Eb, brightness signal Ey .
Order to make 3 primaries by combining it with brightness sìgnal and apply them to picture tubes, color difference signals, Er-Ey , Eg- Ey , Eb- Ey.
》Er- Ey = 0.70Er- 0.59Eg - 0.11Eb ...
》Eg-Ey =- 0.30Er+0.41Eg- 0.11Eb...
》Eb-Ey = -0.30Er- 0.59Eg+ 0.89Eb...
Accordingly, it only need that these 3 signal of brightness signal Ey and 2 color difference signals, Er- Ey, Eb- Ey are transmitted.These 3 signal are called transmission 3 signal components.
4. How to transmit color TV signal
In color TV, all the sìgnals should be transmitted within the band of 6MHz as well as black and white TV. The brightness signal ( Ey ) is multiplied to two color difference signal ( Er- Ey, Eb- Ey ).
5. Multiplication of crominance signal
The 2 color difference signal is transmitted by carrier of 3.58 MHz called chrominance sub-carrier two-phase modulation method is used for the transmission.That is, Eb-Ey and Er-Ey are applied to a balance modulator, and they are balance modulated separately by color sub carrier with phase difference of 90' then, these 2 are composed to be transmitted as chrominance signal.
6. Multiplication of brightness signal and chrominance sìnal
In order to multiply chrominance signal which has the band within +-0.5MHz of 3.58MHz and brightness signal having the band approximately 4MHz.
7. Composite color TV signal
Color and vision
1. Nature of eyes to light
The electromagnetic wave which human eyes can perceive ( wave length approx.380 micro to 780 micro ) is called visible ray of light or light. The perception depends on wave length, and only light with a curtain range of wave length can be seen as colors.
Three element of colour
- luminance ( brightness)
- hue ( tint )
- saturation
Brightness means lightness of colors. When it is light, we say high brightness, and when dark, we say low brightness. Hue ( or tint ) is veriety of colors such as red, green and blue, which depends on wave length. Saturation means density of colors, which indicates the rate of how much is white light mixed.
2. Mixture of light
Red, green and blue are called color primaries, because they can not be made by mixing other colors.
In color TV receiver, to perform mixture, 3 colors of red, green and blue dots are aranged regularly on phosphorescent screen.
3. ICI chromaticity diagram
ICI ( international cnmmision on illumination ) , in which all the colors are included. In color tv, the point of R, G and B, are decided depending on emitting colors of phosphors. The inners part of the triangle encircled by the 3 points is called color area. The colors other than the triangle cannot be made, whatever proportion of the 3 colors is taken for mixing.
4. Nature of eyes to colors
If the area ìs large enough, all thers can be displayed as mentioned above. In color tv receiver, brightness and choramacity signal are transmitted at the same, for large areas ( vidio signal in charge of 0―500kHz ).
The electromagnetic wave which human eyes can perceive ( wave length approx.380 micro to 780 micro ) is called visible ray of light or light. The perception depends on wave length, and only light with a curtain range of wave length can be seen as colors.
Three element of colour
- luminance ( brightness)
- hue ( tint )
- saturation
Brightness means lightness of colors. When it is light, we say high brightness, and when dark, we say low brightness. Hue ( or tint ) is veriety of colors such as red, green and blue, which depends on wave length. Saturation means density of colors, which indicates the rate of how much is white light mixed.
2. Mixture of light
Red, green and blue are called color primaries, because they can not be made by mixing other colors.
In color TV receiver, to perform mixture, 3 colors of red, green and blue dots are aranged regularly on phosphorescent screen.
3. ICI chromaticity diagram
ICI ( international cnmmision on illumination ) , in which all the colors are included. In color tv, the point of R, G and B, are decided depending on emitting colors of phosphors. The inners part of the triangle encircled by the 3 points is called color area. The colors other than the triangle cannot be made, whatever proportion of the 3 colors is taken for mixing.
4. Nature of eyes to colors
If the area ìs large enough, all thers can be displayed as mentioned above. In color tv receiver, brightness and choramacity signal are transmitted at the same, for large areas ( vidio signal in charge of 0―500kHz ).
Principle Television
1. Television
The English word ''Television'' is said to be derived from the Greek ''Tel''( long distance) and the latin ''Vidio''(see) . In Japan, the word ''Television'' is now used as a japanese language, as well as so called ''Te-re-bi'' or TV.
We are aware that movie picture is moving little by little, though it consists of separated still picture. It seems as it is moving by rapid replacement of still picture one after another. It is because of after image, ( the characteristic that, when you are seeing some image, the image will be left even after it di sappears suddenly ). The image will stand still for a moment, 0.05―0.1 seconds, but it looks as a continous motion without any break because of the after image . Scenes of movie are replaced 24 times per second, while those of television, 30 times.
2. Picture element
In general, the element which composes one picture is called picture element . When we watch a picture on newspaper, other printed matters, etc , we can see a lot of small dots, bright and dark, making a picture, which is called picture element in camera processing .
3. Decomposition and composition of picture
But it is imposible to change one scane into electric signal whole at a time . In fact, one scane decomposed into the lot of picture element and one element having a certain brignes is changed into one electrical signal. This consecutive electric signals ( video signal ) are transmitted on the waves .and on the receiving side, the signals are received to be composed ìn the same order as decomposition. In addition, both the starting point and speed of the decomposìtion and composition should agree to each other completely.
The English word ''Television'' is said to be derived from the Greek ''Tel''( long distance) and the latin ''Vidio''(see) . In Japan, the word ''Television'' is now used as a japanese language, as well as so called ''Te-re-bi'' or TV.
We are aware that movie picture is moving little by little, though it consists of separated still picture. It seems as it is moving by rapid replacement of still picture one after another. It is because of after image, ( the characteristic that, when you are seeing some image, the image will be left even after it di sappears suddenly ). The image will stand still for a moment, 0.05―0.1 seconds, but it looks as a continous motion without any break because of the after image . Scenes of movie are replaced 24 times per second, while those of television, 30 times.
2. Picture element
In general, the element which composes one picture is called picture element . When we watch a picture on newspaper, other printed matters, etc , we can see a lot of small dots, bright and dark, making a picture, which is called picture element in camera processing .
3. Decomposition and composition of picture
But it is imposible to change one scane into electric signal whole at a time . In fact, one scane decomposed into the lot of picture element and one element having a certain brignes is changed into one electrical signal. This consecutive electric signals ( video signal ) are transmitted on the waves .and on the receiving side, the signals are received to be composed ìn the same order as decomposition. In addition, both the starting point and speed of the decomposìtion and composition should agree to each other completely.
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