method for compensating frequency shifts in a overdrachtsweg sent through a color signal caused by the overdrachtsweg weglengtevariaties

摘要

1,051,644. Automatic frequency control; radio signalling. PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd. March 19, 1964 [March 22, 1963], Headings H3A and H4L. In colour television relaying by satellite, any Doppler frequency shift is corrected by variably delaying the received signal in accordance with any frequency error of the colour sync. burst signal derived therefrom relative to a frequency standard. The delay may be produced by a rotating magnetic storage drum, on which the signal is recorded and subsequently picked off, driven with variable speed by a motor controlled by a frequency discriminator, or by a phase discriminator with one input a local subcarrier frequency standard and the other the gated subcarrier burst signal. The standard frequency may alternatively be derived from the transmitter through a path, e.g. telephone line, not subject to Doppler effect. The discriminator output may alternatively control the circumferential angle between the record and pick-up heads of the drum, the speed of which is constant. Or the delay may be produced by supersonic oscillations passing through a fluid path of variable length. The recorded signal may be the colour subcarrier frequency, or an amplitude or frequency modulated carrier subsequently (i.e. after being delayed) demodulated to derive the colour subcarrier frequency burst.