Method and apparatus for using a vertical internal test signal for phase control of an offset modulation of offset sampling system

DETAILED DESCRIPTION It is an object of the present invention to provide a method for modulation and synchronous demodulation of color television signals processed according to the offset modulation and offset sampling principle wherein the subsequent sampling and demodulation at the receiving end occurs in synchronism with the sampling and modulation at the transmitting end while maintaining compatibility with the existing television standards (NTSC, SECAM, PAL).
It is a further object of the invention to provide a suitable arrangement for implementing this method.
The above and other objects are accomplished by the invention, in the context of the transmission of a color television signal containing chrominance burst and sync signals over a Nyquist channel between a transmitting station and a receiving station, by a method for modulating and synchronously demodulating the television signal according to the offset modulation and offset sampling principle, which includes: using the chrominance burst or sync pulses as a reference signal for frequency recovery at the receiving station; generating an additional reference signal at the transmitting station and transmitting the additional reference signal over the Nyquist channel; and utilizing the additional reference signal for phase recovery at the receiving station.
An increase in resolution compatible with the Multiplexed Analog Component (MAC) method is described in connection with direct broadcasting of signals from satellites utilizing separate component transmission, and with reference to the offset sampling method, in an article by R.
Rawlings and R.
Morcom entitled "Multiplexed Analogue Components--A New Video Coding System For Satellite Broadcasting" presented at the International Broadcasting Convention at Brighton, England, 1982, and published in Electron.
Eng.
Assoc.
, IEEE Conference, IBC 82, XVI+376 P.
, at pages 158-164.
The method described in the cited paper employs a line frequent (occurs every line) clock pulse recovery burst which has a frequency that is not specified in detail