Color television receivers

Claim 2

A receiver for colour television signals of the kind in which colour information is carried as phase dependent modulation of a sub-carrier, the receiver including means for converting a received video signal to an intermediate frequency which is a phase locked integral multiple of the sub-carrier frequency; and means for synchronously demodulating the intermediate frequency signal to produce luminance and chrominance information.

Claim 3

A receiver according to claim 1, wherein the intermediate frequency is 4 N times the sub-carrier frequency, where N is an integer.

Claim 4

A receiver according to claim 2, wherein the intermediate frequency is 35.46895 MHz and the sub-carrier frequency is 4.43361875 MHz.

Claim 5

A receiver according to claim 1, wherein the intermediate frequency is 28.63636 MHz and the sub-carrier frequency is 3.579545 MHz.

Claim 6

A receiver for colour television signals of the kind in which colour information is carried as phased dependent modulation of a sub-carrier signal, the receiver including a local oscillator, means for mixing a received video signal with a signal generated by said local oscillator to produce an intermediate frequency signal having a frequency which is a phase-locked integral multiple of said sub-carrier frequency; crystal controlled oscillator means; means for locking the crystal controlled oscillator means to a multiple of the sub-carrier frequency; phase comparator means for comparing the output signal frequency of the crystal controlled oscillator means with said intermediate frequency signal; and means responsive to an output signal from said comparator means for adjusting the frequency or phase of said local oscillator output signal in a sense to bring the intermediate frequency signal into said phase-locked relation with the output signal of said crystal controlled oscillator means.

Claim 7

A receiver for colour television signals of the kind in which colour information is carried as phased dependent modulation of a sub-carrier signal, the receiver including a local oscillator, means for mixing a received video signal with a signal generated by said local oscillator to produce an intermediate frequency signal having a frequency which is a phase-locked integral multiple of said sub-carrier frequency; crystal controlled oscillator means; means for locking the crystal controlled oscillator means to a multiple of the sub-carrier frequency; phase comparator means for comparing the output signal frequency of the crystal controlled oscillator means with said intermediate frequency signal; and means responsive to an output signal from said comparator means for adjusting the frequency or phase of said local oscillator output signal in a sense to bring the intermediate frequency signal into said phase-locked relation with the output signal of said crystal controlled oscillator means.

Claim 8

A receiver according to claim 5, wherein the means for phase-locking the crystal oscillator is responsive to a colour burst signal derived from the received signal.

Claim 9

A receiver according to claim 5, wherein the local oscillator is a varactor tuned oscillator.

Claim 10

A receiver according to claim 7, including means for applying preset voltages to a varactor of the local oscillator to effect channel selection.

Claim 11

A receiver according to claim 8, including means for generating a slowly varying voltage ramp which is added to the preset voltages to widen the capture range of the local oscillator frequency control.

Claim 12

A receiver according to claim 5, including synchronous demodulator means for receiving said crystal controlled oscillator signal producing a Y or Y-chroma signal.

Claim 13

A receiver according to claim 10, including means for combining said crystal controlled oscillator signal and a signal of sub-carrier frequency and means for utilizing said combined signal and said intermediate frequency signal to produce U- and V- signals.

Claim 14

A receiver according to claim 10, including demodulator means for utilizing the crystal oscillator signal and a signal of sub-carrier frequency sequentially and separately to demodulate the intermediate frequency signal to produce U- and V- signals.

Claim 15

A receiver according to claim 11 or 12, including means for dividing the output frequency of the crystal oscillator to derive said signal of sub-carrier frequency.

Claim 16

A receiver according to claim 12, including surface wave filter means having a flat amplitude response connected to provide suitable relative delays between the Y signal and the U- and V- signals.

Claim 17

A receiver according to claim 11, including gating means enabled to pass the intermediate frequency signal or a signal derived therefrom at appropriate times to produce the Y, U and V signals.

Claim 18

A receiver for colour television signals of the kind in which colour information is carried as phase dependent modulation of a sub-carrier signal, the receiver including a varactor controlled local oscillator, means for mixing a received video signal with a signal generated by said local oscillator to produce an intermediate frequency signal having a frequency which is a phase-locked integral multiple of said sub-carrier frequency; crystal controlled oscillator means; means responsive to a colour burst signal derived from said received video signal for locking the crystal controlled oscillator means to a multiple of the sub-carrier frequency; phase comparator means for comparing the output signal frequency of the crystal controlled oscillator means with said intermediate frequency signal; means responsive to an output signal from said comparator means for adjusting the frequency or phase of the local oscillator output signal in a sense to bring the intermediate frequency signal into said phase-locked relation with the output signal of said crystal controlled oscillator means; synchronous demodulator means for receiving said crystal controlled oscillator means output signal and said intermediate frequency signal for producing a Y or Y-chroma signal; and further demodulator means for utilizing the crystal controlled oscillator signal and a signal of sub-carrier frequency sequentially and separately to demodulate the intermediate frequency signal to produce U- and V- signals.

Claim 19

A receiver for colour television signals of the kind in which colour information is carried as phase dependent modulation of a sub-carrier signal, the receiver including a varactor controlled local oscillator, means for mixing a received video signal with a signal generated by said local oscillator to produce an intermediate frequency signal having a frequency which is a phase-locked integral multiple of said sub-carrier frequency; crystal controlled oscillator means; means responsive to a colour burst signal derived from said received video signal for locking the crystal controlled oscillator means to a multiple of the sub-carrier frequency; phase comparator means for comparing the output signal frequency of the crystal controlled oscillator means with said intermediate frequency signal; means responsive to an output signal from said comparator means for adjusting the frequency or phase of the local oscillator output signal in a sense to bring the intermediate frequency signal into said phase-locked relation with the output signal of said crystal controlled oscillator means; synchronous demodulator means for receiving said crystal controlled oscillator means output signal and said intermediate frequency signal for producing a Y or Y-chroma signal; and further demodulator means for utilizing the crystal controlled oscillator signal and a signal of sub-carrier frequency sequentially and separately to demodulate the intermediate frequency signal to produce U- and V- signals.

Claim 20

A receiver according to claim 16, including means for dividing the output frequency of said crystal controlled oscillator means to derive said signal of sub-carrier frequency.

Claim 21

A receiver according to claim 16, including surface wave filter means having a flat amplitude response connected to provide suitable relative delays between the Y- and the U- and V- signals.