Gain IF section : The main function of this section is to amplify modulated IF signal over its bandwidth with an of about 0.5mV signal from the mixer to deliver about 4V into the video detector. IF section is used to equalize amplitudes of sideband components ,because of vestigial side band transmission. IF section is used to reject the signals from adjacent channels. 11. Explain in detail the NTSC color receiver system. NTSC system is compatible with 525 line American system.In order to maintain compatibility two new colour difference signals are generated and they are represented as I and Q. Since eye is capable of resolving finer details in the regions around I,it is allowed to have a maximum bandwidth of 1.5MHz.The bandwidth of Q signal is restricted to 0.5MHz. Limitations of the NTSC system. The NTSC system is sensitive to transmission path differences introduces phase errors that result in colour changes in the picture. At the transmitter,phase changes in the chroma signal take place when change over between programmes of local and television network systems takes place and when video tape recorders are switched on .The phase angle is also affected by the level of the signal while passing through various circuits .In addition cross talk between demodulator outputs at the receiver causes colour distortion. 12. Explain working of a pAL system. The weighted (B-Y) and (R-Y) signals are modulated without being given a phase shift of 33 as is done in the NTSC system. On modulation both the color difference signals are allowed the same bandwidth of about 1.3MHz. The subcarrier frequency is chosen to be 4.43MHz. The weighted color difference signals are quadrature modulated with the subcarrier. 13.Describe with necessary diagrams the encoding of color difference signal. Quadrature modulation: It is used to combine two colour difference signals in to a single variable. Frequency interleaving: The technique of combining two distinct signal within the same bandwidth is as frequency interleaving. Colour burst: Sample of colour subcarrier output at the encoder are transmitted along with other sync pulses. 14.Describe the generation of Y signal and difference signals. Find the value for cyan. In a color camera ,the luminance or Y signal is obtained by adding R,G and B in the following proportions
Gain IF section : The main function of this section is to amplify modulated IF signal over its bandwidth with an of about 0.5mV signal from the mixer to deliver about 4V into the video detector. IF section is used to equalize amplitudes of sideband components ,because of vestigial side band transmission. IF section is used to reject the signals from adjacent channels. 11. Explain in detail the NTSC color receiver system. NTSC system is compatible with 525 line American system.In order to maintain compatibility two new colour difference signals are generated and they are represented as I and Q. Since eye is capable of resolving finer details in the regions around I,it is allowed to have a maximum bandwidth of 1.5MHz.The bandwidth of Q signal is restricted to 0.5MHz. Limitations of the NTSC system. The NTSC system is sensitive to transmission path differences introduces phase errors that result in colour changes in the picture. At the transmitter,phase changes in the chroma signal take place when change over between programmes of local and television network systems takes place and when video tape recorders are switched on .The phase angle is also affected by the level of the signal while passing through various circuits .In addition cross talk between demodulator outputs at the receiver causes colour distortion. 12. Explain working of a pAL system. The weighted (B-Y) and (R-Y) signals are modulated without being given a phase shift of 33 as is done in the NTSC system. On modulation both the color difference signals are allowed the same bandwidth of about 1.3MHz. The subcarrier frequency is chosen to be 4.43MHz. The weighted color difference signals are quadrature modulated with the subcarrier. 13.Describe with necessary diagrams the encoding of color difference signal. Quadrature modulation: It is used to combine two colour difference signals in to a single variable. Frequency interleaving: The technique of combining two distinct signal within the same bandwidth is as frequency interleaving. Colour burst: Sample of colour subcarrier output at the encoder are transmitted along with other sync pulses. 14.Describe the generation of Y signal and difference signals. Find the value for cyan. In a color camera ,the luminance or Y signal is obtained by adding R,G and B in the following proportions
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