Color television system for elimination of phase errors

Claim 2

A color television system operative to provide a composite television signal from three primary signals and operative to work on a received chrominance signal; said composite signal being made up of a luminance signal on a carrier and said chrominance signal; said chrominance signal being made up of two difference signals amplitude modulated on a sub-carrier with respect to two mutually perpendicular axes and a constant amplitude reference color burst at the frequency of the subcarrier, said two differance signals being absent at the start of every second line when said color burst is present, the first of said difference signals being present while the second of said two differance signals is absent during odd-numbered lines, and said second differance signal being present while said first differance signal is absent during even-numbered lines; said system comprising: first means operative to receive said three primary signals and to generate said luminance signal on a carrier and said two differance signals; second means operative to receive said two differance signals and said luminance signal and to generate said chrominance signal, said second means being further operative to provide phase angle separation between said two amplitude modulated difference signals and to effect surpression of each of said two amplitude modulated signals singly and simultaneously, and to combine said luminance and chromiance signals; and third means operative to receive said chrominance signal and to effect a time delay between said amplitude modulated differance signals and to combine said two amplitude modulated differance signals so that both of said amplitude modulated differance signals which are transmitted on alternate lines are present during each line.

Claim 3

A color television system operative to provide a composite television signal from three primary signals and operative to work on a received chrominance signal; said composite signal being made up of a luminance signal on a carrier and said chrominance signal; said chrominance signal being made up of two difference signals amplitude modulated on a sub-carrier with respect to two mutually perpendicular axes and a constant amplitude reference color burst at the frequency of the sub-carrier, said two differance signals being absent at the start of every second line when said color burst is present, the first of said difference signals being present while the second of said two differance signals is absent during odd-numbered lines, and said second differance signal being present while said first differance signal is absent during even-numbered lines; said system comprising: first means operative to receive said three primary signals and to generate said luminance signal on a carrier and said two differance signals; second means operative to receive said two differance signals and said luminance signal and to generate said chrominance signal, said second means being further operative to provide phase angle separation between said two amplitude modulated difference signals and to effect surpression of each of said two amplitude modulated signals singly and simultaneously, and to combine said luminance and chromiance signals; and third means operative to receive said chrominance signal and to effect a time delay between said amplitude modulated differance signals and to combine said two amplitude modulated differance signals so that both of said amplitude modulated differance signals which are transmitted on alternate lines are present during each line.

Claim 4

A color television system operative to provide a composite television signal from three primary signals and operative to work on a received chrominance signal; said composite signal being made up of a luminance signal on a carrier and said chrominance signal; said chrominance signal being made up of two difference signals amplitude modulated on a sub-carrier with respect to two mutually perpendicular axes and a constant amplitude reference color burst at the frequency of the sub-carrier, said two differance signals being absent at the start of every second line when said color burst is present, the first of said difference signals being present while the second of said two differance signals is absent during odd-numbered lines, and said second differance signal being present while said first differance signal is absent during even-numbered lines; said system comprising: first means operative to receive said three primary signals and to generate said luminance signal on a carrier and said two differance signals; second means operative to receive said two differance signals and said luminance signal and to generate said chrominance signal, said second means being further operative to provide phase angle separation between said two amplitude modulated difference signals and to effect surpression of each of said two amplitude modulated signals singly and simultaneously, and to combine said luminance and chromiance signals; and third means operative to receive said chrominance signal and to effect a time delay between said amplitude modulated differance signals and to combine said two amplitude modulated differance signals so that both of said amplitude modulated differance signals which are transmitted on alternate lines are present during each line.

Claim 5

The color television system according to claim 1 wherein: said first means comprise a matrix to which primary color input signals are supplied and which produces a luminance signal and two difference signals based upon these input signals; said second means comprise a sub-carrier generator, a first phase-shift device for producing a phase shift of the sub-carrier in a first direction, a seconD phase-shift device for producing a phase shift of the sub-carrier in a second direction which is at 90* to the first, means for modulating the sub-carrier phase-shifted in the first direction by one of said difference signals and for modulating the phase-carrier phase-shifted in the second direction by the second difference signal; means for adding the modulated signals to the luminance signal , said means comprising switching and adding means which effect the alternate addition to the luminance signal of the sub-carrier phase-shifted in the first direction and modulated by the first difference signal during one line, and of the sub-carrier phase-shifted in the second direction and modulated by the second difference signal during the following line.

Claim 6

The color television system according to claim 2 wherein said means for modulating said sub-carrier comprise a first modulator for amplitude-modulating the sub-carrier as phase-shifted in the first direction with one of said difference signals, a second modulator for amplitude modulating the sub-carrier as phase-shifted in the second direction, a switch or double gate whose inputs are connected to the modulators, an adder having one input connected to the output of the switch and its other input connected to the source of said reference color burst, and means for controlling the switch at half the line-scan frequency.

Claim 7

The color television system according to claim 2, wherein said means for modulating said sub-carrier further comprise a first switch whose inputs receive the difference signals, a second switch whose inputs are connected to two phase-shift devices, a modulator whose inputs are connected to the outputs of the two switches, and means for controlling the two switches at half the line-scan frequency, and said second means further comprise an adder having one input supplied by the color burst signal and its other input connected to the output of the modulator.

Claim 8

The color television system according to claim 4, wherein said second means further comprise a color burst gate the input of which is connected to said sub-carrier generator, a second adder which receives at one input said luminance signal and at the other input said color burst signal and said chrominance signal, means being provided for supplying opening pulses to said color burst gate at half the line-scan frequency.

Claim 9

The color television system according to claim 2, wherein said second means further comprise means for alternately blocking said modulating difference signals during successive line-scan periods.

Claim 10

The color television system according to claim 6 wherein said second means further comprises an adder to add to at least one of said modulating difference signals a pulse of half line-scan frequency whose duration and position determine the reference marker color burst.

Claim 11

The color television system according to claim 1 wherein said third means comprise a delay line whose delay is equal to the duration of line-scan; a permutating device having two inputs for connection to the sub-carrier separator of an NTSC receiver, one directly and the other via said delay line, said permutating device having outputs designed for connection to synchronous demodulators; means for controlling the permutating device through the medium of a line-scan flyback signal from said receiver; and means for restoring the phase of said control means, comprising a detector designed for connection to the color burst gate of the receiver and connected via a filter to a control circuit.

Claim 12

The color television system according to claim 8 wherein said third means further comprise a phase-shift device designed for connection to the local oscillator of the receiver and producing a phase-shift of the sub-carrier in the first direction; a second phase-shift device likewise designed for connection to the local oscillator; a first synchronous amplitude demodulator having one input connected to one of the outputs of the permutating device and a Second input connected to the first phase-shift device in order to produce one of the components of the chrominance signal; a second synchronous amplitude demodulator having one input connected to the other output of the permutating device and a second input connected to the second phase-shift device in order to furnish the other component of the chrominance signal; a first balanced modulator whose inputs are connected to the first phase-shift device and to the first demodulator; a second balanced modulator whose inputs are connected to the second phase-shift device and to the second demodulator; and an adder whose inputs are connected to the two modulators and whose output is designed for connection to the synchronous demodulators of the receiver.

Claim 13

A color television system operative to provide a composite television signal from a composite NTSC signal, and operative to work on a receiver chrominance signal; said composite television signal being made up of a luminance signal on a carrier and said chrominance signal; said chrominance signal being made up of two differance signals amplitude modulated on a sub-carrier with respect to two mutually perpendicular axes and a constant amplitude reference color burst at the frequency of the sub-carrier, said two differance signals being absent at the start of every second line when said color burst is present, the first of said differance signals being present while the second of said two differance signals is absent during odd-numbered lines, and said second differance signal being present while said first differance signal is absent during even-numbered lines; said system comprising: first means operative to receive said composite NTSC signal and to generate said chrominance signal; second means operative to combine said composite NTSC signal with said chrominance signal to provide said composite television signal; and third means operative to receive said chrominance signal and to effect a time delay between said amplitude modulated differance signals and to combine said two amplitude modulated differance signals so that both of said two amplitude modulated differance signals which are transmitted on alternate lines are present during each line.

Claim 14

A color television system operative to provide a composite television signal from a composite NTSC signal, and operative to work on a receiver chrominance signal; said composite television signal being made up of a luminance signal on a carrier and said chrominance signal; said chrominance signal being made up of two differance signals amplitude modulated on a sub-carrier with respect to two mutually perpendicular axes and a constant amplitude reference color burst at the frequency of the sub-carrier, said two differance signals being absent at the start of every second line when said color burst is present, the first of said differance signals being present while the second of said two differance signals is absent during odd-numbered lines, and said second differance signal being present while said first differance signal is absent during even-numbered lines; said system comprising: first means operative to receive said composite NTSC signal and to generate said chrominance signal; second means operative to combine said composite NTSC signal with said chrominance signal to provide said composite television signal; and third means operative to receive said chrominance signal and to effect a time delay between said amplitude modulated differance signals and to combine said two amplitude modulated differance signals so that both of said two amplitude modulated differance signals which are transmitted on alternate lines are present during each line.

Claim 15

A color television system according to claim 10 wherein said first means comprise a sub-carrier separator, a sync. signal separator; a shaper signal for producing line-scan frequency pulses from the sync. signals; a color burst gate controlled by the line-scan frequency pulses; a local oscillator tuned to the sub-carrier frequency; a phase comparator connected to the sub-carrier separator via the color burst gate and to the local oscillator via a loop circuit designed to keep the oscillator in phase with the reference phase determined by the color burst; a first phase-shift device connected to the local oscillator and designed to produce a phase-shift in the sub-carrier in a first direction, this latter for example making an angle of 180* with respect to the axis of the sub-carrier produced by the oscillator; a second phase-shift device designed to phase-shift the sub-carrier in a second direction at an angle of 90* with respect to the first direction; a first synchronous amplitude demodulator connected to the sub-carrier separator and to the first phase-shift device in order to demodulate said sub-carrier in said first direction and thus produce one of said difference signals; and a second synchronous amplitude demodulator connected to the sub-carrier separator and to the second phase-shift device in order to demodulate said sub-carrier in said second direction and thus produce the second difference signal; and further comprising a third phase-shift device for phase-shifting the sub-carrier in a third direction making an angle of 180* with respect to said first direction; a fourth phase-shift device for phase-shifting the sub-carrier in a fourth direction making an angle of 180* with respect to said second dirEction; means for modulating said sub-carrier phase-shifted in said third direction by the said first difference signal and for modulating the sub-carrier phase-shifted in the fourth direction by said second difference signal; and wherein said second means comprise switching and adding means for alternatively adding to the incident signal the sub-carrier phase-shifted in said third direction and modulated by said first difference signal during one line, and the sub-carrier phase-shifted in the fourth direction and modulated by said second difference signal during the following line, in order to sequentially eliminate from the incident signal alternatively one component of the chrominance vector and then the other component thereof.

Claim 16

The color television system according to claim 11 wherein said first means further comprises a first balanced modulator for amplitude-modulating the sub-carrier phase-shifted in the third direction with the first difference signal; a second balanced modulator for amplitude-modulating the sub-carrier phase-shifted in the fourth direction; a switch or double gate whose inputs are connected to the modulators; and said second means further comprise an adder having one input supplied with the incident signal and its other input connected to the output of the switch and means for controlling the switch at half the line-scan frequency.

Claim 17

The color television system according to claim 10 wherein said first means further comprise a first switch whose inputs receive the difference signals; a second switch whose inputs are connected to the two phase-shift devices; a modulator whose inputs are connected to the out-puts of the two switches; and said second means further comprise an adder one input of which receives the incident signal whilst its other input is connected to the output of the modulator; and means for controlling the two switches at half the line-scan frequency.

Claim 18

A color television system according to claim 10 wherein said first means comprise a color burst blocking gate arranged to receive said NTSC signal, and means for supplying closing pulses to said gate at half the line-scan frequency.

Claim 19

The color television system according to claim 10 wherein said third means comprise a delay line whose delay is equal to the duration of line-scan; a permutating device having two inputs for connection to the sub-carrier separator of an NTSC receiver, one directly and the other via said delay line, said permutating device having outputs designated for connection to synchronous demodulators; means for controlling the permutating device through the medium of a line-scan flyback signal from said receiver; and means for restoring the phase of said control means, comprising a detector designed for connection to the color burst gate of the receiver and connected via a filter to a control circuit.

Claim 20

The color television system according to claim 15 wherein said third means further comprises a phase-shift device designed for connection to the local oscillator of the receiver and producing a phase-shift of the sub-carrier in the first direction; a second phase-shift device likewise designed for connection to the local oscillator; a first synchronous amplitude demodulator having one input connected to one of the outputs of the permutating device and a second input connected to the first phase-shift device in order to produce one of the components of the chrominance signal; a second synchronous amplitude demodulator having one input connected to the other output of the permutating device and a second input connected to the second phase-shift device in order to furnish the other component of the chrominance signal; a first balanced modulator whose inputs are connected to the first phase-shift device and to the first demodulator; a second balanced modulator whose inputs are connected to the second phase-shift device and to the second demodulator; and an adder whose inputs are connected to the two modulators and whose output is designed foR connection to the synchronous demodulators of the receiver.

Claim 21

A color television system operative to provide a composite television signal from three primary signals; said composite signal being made up of a luminance signal on a carrier and a chrominance signal; said chrominance signal being made up of two differance signals amplitude modulated on a sub-carrier with respect to two mutually perpendicular axes and a constant amplitude reference color burst at the frequency of the sub-carrier, said two differance signals being absent at the start of every second line when said color burst is present, the first of said difference signals being present while the second of said two differance signals is absent during odd-numbered lines, and said second differance signal being present while said first differance signal is absent during even-numbered lines; said system comprising: first means operative to receive said three primary signals and to generate said luminance signal on carrier and said two differance signals; and second means operative to receive said two differance signals and said luminance signal and to generate said chrominance signal, said second means being further operative to provide phase angle separation between said two amplitude modulated differance signals and to effect surpression of each of said two amplitude modulated signals singly and simultaneously, and to combine said luminance and chrominance signals.

Claim 22

A color television system operative to provide a composite television signal from three primary signals; said composite signal being made up of a luminance signal on a carrier and a chrominance signal; said chrominance signal being made up of two differance signals amplitude modulated on a sub-carrier with respect to two mutually perpendicular axes and a constant amplitude reference color burst at the frequency of the sub-carrier, said two differance signals being absent at the start of every second line when said color burst is present, the first of said difference signals being present while the second of said two differance signals is absent during odd-numbered lines, and said second differance signal being present while said first differance signal is absent during even-numbered lines; said system comprising: first means operative to receive said three primary signals and to generate said luminance signal on carrier and said two differance signals; and second means operative to receive said two differance signals and said luminance signal and to generate said chrominance signal, said second means being further operative to provide phase angle separation between said two amplitude modulated differance signals and to effect surpression of each of said two amplitude modulated signals singly and simultaneously, and to combine said luminance and chrominance signals.

Claim 23

A color television system operative to provide a composite television signal from a composite NTSC signal; said composite television signal being made up of a luminance signal on a carrier and a chrominance signal; said chrominance signal being made up of two differance signals amplitude modulated on a sub-carrier with respect to two mutually perpendicular axes and a constant amplitude reference color burst at the frequency of the sub-carrier, said two differance signals being absent at the start of every second line when said color burst is present, the first of said differance signals being present while the second of said two differance signals is absent during odd-numbered lines, and said second differance signal being present while said first differance signal is absent during even-numbered lines, said system comprising: first means operative to receive said composite NTSC signal and to generate said chrominance signal; and second means operative to combine said composite NTSC signal with said chrominance signal to provide said composite television signal.

Claim 24

A color television system operative to provide a composite television signal from a composite NTSC signal; said composite television signal being made up of a luminance signal on a carrier and a chrominance signal; said chrominance signal being made up of two differance signals amplitude modulated on a sub-carrier with respect to two mutually perpendicular axes and a constant amplitude reference color burst at the frequency of the sub-carrier, said two differance signals being absent at the start of every second line when said color burst is present, the first of said differance signals being present while the second of said two differance signals is absent during odd-numbered lines, and said second differance signal being present while said first differance signal is absent during even-numbered lines, said system comprising: first means operative to receive said composite NTSC signal and to generate said chrominance signal; and second means operative to combine said composite NTSC signal with said chrominance signal to provide said composite television signal.