قسم معالجة إشارة النصوع .. كتاب التلفزيون الملون والعادي

2-20 Luminance signal processing section:

This section deals with screen lighting information, which is the black and white monochrome image information in the composite visual signal - and since the signal in the receiving device is wired and processed in opposite sequence to the transmitter, therefore the first stage in processing the visual signal after detection is to separate the luminance signal, not from the color signal. (2 - 20) by means of two filter circuits


A- A low-pass filter (LPF) allows only the luminance carrier signal (Y) to pass because its frequency is 125 MHz (Fig. (3-20).

b - A high-pass filter (BPF) allows only the color carrier signal to pass through and its center frequency is 4.43 MHz. The luminance signal processing circuits contain multiple amplification stages to gain the signal sufficient strength to give sufficient lighting, and prevent interference problems, and additional circuits required by color reception and not found in monochrome TV - noise cancellation circuits - black stabilization, automatic lighting limiter, and other special circuits. Processing the luminance signal Its circuits are distinguished from similar circuits in black and white television by the presence of a larger and more complex series of processing, control and amplification circuits for the signal before it is sent to the color screen diode, because the required signal voltage at the output is equal to (-70 volts) and the signal path must be Y so that it secures the curve A specific laminar and laminar pass guarantees - as we mentioned - that no distortion or interference occurs during the transfer of rapid changes of luminance from white to black - it is also required to ensure that the sub-carrier frequency of the coloration signal is sufficiently suppressed, and for this a rejection filter (notch) is used and there must be a unit to retrieve the vehicle The continuous signal before it reaches the valve because the DC compound has an important role in forming a good image. And since the No signal and the color difference signals have to reach the screen diode at the same time, therefore, the Y luminance signal must be hindered and delayed from the color difference signals by (1 microsecond) in a special circuit called the delay line, as the passage of the signal with the highest frequency takes longer time within the screen scroll filter.