
Figure 28.4 NTSC encoder block diagram. A subcarrier oscillator generates
sin
and
cos
contin-
uous waves. Quadrature modulation is performed on lowpass-filtered U and V components by
a pair of 4-quadrant multipliers. An adder forms modulated chroma, C. Chroma and luma Y' are
summed to form composite video. Frequency interleaving is achieved when subcarrier is coherent
with scanning.
If the phase of burst is altered,
and the phase of modulated
subcarrier is altered by the same
amount, an analog chroma
demodulator will still produce the
correct color. What matters is the
phase relationship between the
two. An analog decoder cannot ...