| 摘要 |
<p>PURPOSE:To reduce the generation of transmission line phase distortion by imposing orthogonal balanced modulation on a subcarrier for a high-definition luminance signal with a signal obtained by inverting two frequency-divided high-definition luminance signals in polarity at intervals of one scanning line and generating a high-definition carrier luminance signal, and multiplexing it with an NTSC color television signal and sending the resulting signal. CONSTITUTION:A luminance signal Y and a low-frequency luminance signal YL are inputted to an adder 9 for subtraction to obtain the high-definition luminance signal YH. The YH is further separated into signals of two frequency bands by an LPF 10 and an adder 11 and inputted to balanced modulators 12 and 13 respectively to obtain high-definition carrier luminance signals YH1 and YH2. A changeover switch 16 is switched by being applied with a control signal of frequency a half as high as a horizontal scanning frequency fH and the subcarrier which is inverted in polarity at intervals of one scanning line and 90 deg. out of phase with the output of a 90 deg. phase device 14 appears at the output of the changeover switch 16. This is inputted to the balanced modulator 13. Thus, high-definition carrier luminance signals YH1+ or -j and YH2 are obtained which are modulated in conjugate complex relation at intervals of one scanning line as well as a PAL signal.</p> |
