| 摘要 |
In the letterbox colour television system, additional data are transmitted with an appreciably reduced amplitude for reasons of compatibility, low frequency components having a relatively high amplitude. This results, however, in a reduction in the signal-to-noise ratio and disturbances in synchronization occur in known television receivers. The amplitude of the additional data can be increased without the disturbances in synchronization that occur in known television receivers if the additional data are transmitted in the form of a vestigial sideband modulation of the colour carrier. The frequency response of known IF filters can be exploited advantageously to form a Nyquist flank on the colour carrier. If the phase used is a constant V-phase of the colour carrier, any disturbances in the compatible reception are advantageously slight. |
