Introduction:

• The block diagram of PAL encoder is shown in figure, it uses the gamma corrected RGB signals from the camera tube as input and produces the composite colour video signal at its output.
  • The gamma corrected RGB signals are applied to the Y matrix, which is a resistive network. It will attenuate RGB signals in adequate proportions to produce the luminance signal Y and its inverted version (–Y).
  • The Y signal is applied to the delay line while -Y signal is applied to the (V-U) matrix.
  • The (V-U) matrix is a resistive network which combines the R, B and –Y signals in appropriate proportion to produce the chrominance signal V and U. The relation between V and U and RGB signals can be expressed using the following equations:

Mathematically,

                                  Y = 0.3R + 0.59G + 0.11B
                                       U = 0.477(R-Y)
                                       V = 0.895(B-Y)

• At the output of (V-U) matrix we get U and V signals as shown in figure, the 90 degree phase shifted colour subcarrier(CSC) and the U signal are applied to the U modulator. The U and V signals are bandlimited to 1-2 MHz. The U modulator output is denoted by a Fu.

Diagram:

• The CSC is also applied to the PAL switch controlled by the sync pulse generator to obtain phase shift of zero degree and 180 degree on alternate lines. This CSC is modulated by V signal to produce signal ±Fv at the output of the V modulator.
• The Fu and ±Fv signals are then added together to obtain the F signal, which is further added to the delay compensated luminance Y and the sync and blanking pulses from the sync pulse generator to produce the composite colour video signal.