Cancelling cross modulation in two color TV signals passed through non-linear path

DETAILED DESCRIPTION What is claimed is: 1.
In a system in which two color television video signals having slightly different color subcarrier frequencies are transmitting over a common channel, means to minimize the effects of cross modulation of the two color subcarriers, comprising means at the transmitting end to delay alternate lines of one of said video signals by the amount of half the period of the color subcarrier, means at the receiving end to delay the intermediate lines of said one video signal by the amount of half the period of the color subcarrier, and means at the receiving end to cancel the color subcarrier frequency components occurring during horizontal synchronizing pulses in said one video signal.
2.
A system according to claim 1 wherein said means to cancel color subcarrier frequency components comprises delay means to delay said one video signal an amount equal to one half the period of the color subcarrier frequency, and switch means to combine the delayed video signal with the undelayed video signal during the horizontal synchronizing pulses.
3.
A system according to claim 2 wherein said switch means is operated by a signal derived from the horizontal synchronizing pulses of said one video signal.




Description:
This invention relates to systems for the transmission of two color television signals over a common non-linear path.
The invention is especially useful in systems in which a plurality of different color television signals are transmitted from a ground station to a satellite in which the signals are amplified and then returned to a ground station remote from the transmitting ground station.
The receiving ground station may forward the television signals to nearby television transmitting stations which broadcast to television receivers in a local area of about 50 miles radius.
The amplifiers in the transponders in the satellites are traveling-wave-tube amplifiers because they are light in weight, use a minimum of electric power and have high gain