Apparatus for correcting phase shifts in angle-modulated signals

Claim 2

Apparatus for providing from an angle-modulated first reference signal affected by noise a second reference signal having an angular position which follows in a fixed relationship the angular position or said angle-modulated first reference signal, comprising in combination: a. firSt means for providing said first reference signal affected by noise; b. second means connected to said first means for filtering said first reference signal from said noise, said second means including first filter means imposing a first phase shift on said first reference signal; c. third means including buffer means for deriving a feedback signal from said second reference signal; d. second filter means connected to said third means for imposing on said feedback signal a second phase shift corresponding to said first phase shift; e. fourth means connected to said first and second filter means for heterodyning said first reference signal having said first phase shift and said feedback signal having said second phase shift to produce a heterodyned signal; f. fifth means connected to said fourth means for extracting from said heterodyned signal a difference signal corresponding to the frequency difference between said first reference signal having said first phase shift and said feedback signal having said second phase shift; g. sixth means for providing a stable third reference signal; h. seventh means connected to said fifth and sixth means for deriving a phase-error signal varying in accordance with phase discrepancies between said stable third reference signal and said difference signal; and i. oscillator means connected to said seventh means for providing in response to said phase-error signal said second reference signal having said angular position, with said third means being connected to said oscillator means.

Claim 3

Apparatus as claimed in claim 1, wherein said third, fourth, fifth and seventh means, said second filter means, and said oscillator means are connected in a phase-locked circuit.

Claim 4

Apparatus for correcting effects of angular errors in a color video signal accompanied by a first reference signal angle-modulated in accordance with said angular errors and affected by noise, comprising in combination: a. first means for providing said color video signal with said angular errors and said angle-modulated first reference signal; b. second means connected to said first means for separating said angle-modulated first reference signal from said color video signal; c. third means connected to said second means for filtering said angle-modulated first reference signal from said noise, said third means including first filter means imposing a first phase shift on said angle-modulated first reference signal; d. fourth means connected to said third means for receiving said phase-shifted angle-modulated and filtered first reference signal and for correcting said first phase shift to produce a second reference signal having an angular position which follows in a fixed relationship the angular position of said angle-modulated first reference signal prior to imposition of said first phase shift, said fourth means including buffer means for deriving a feedback signal from said second reference signal, second filter means connected to said buffer means for imposing on said feedback signal a second phase shift corresponding to said first phase shift, means connected to said first and second filter means for heterodyning said first reference signal having said first phase shift and said feedback signal having said second phase shift to produce a heterodyned signal, means connected to said heterodyning means for extracting from said heterodyned signal a difference signal corresponding to the frequency difference between said first reference signal having said first phase shift and said feedback signal having said second phase shift, means for providing a stable reference signal, means connected to said difference signal extracting means and said stable third reference signal providing means for deriving a phase-error signal varying in accordance with phase discrepancies between said stable third reference signal and said difference signal, and oscillator means connected to said phase-error deriving means for providiNg in response to said phase-error signal said second reference signal having said angular position, with said buffer means being connected to said oscillator means; e. fifth means connected to said first and fourth means for processing said color video signal with the aid of said second reference signal to dispose modulation components of said color video signal about a substantially stable carrier while substantially retaining phase and amplitude interrelationships of said modulation components.

Claim 5

Apparatus for correcting effects of angular errors in a color video signal accompanied by a first reference signal angle-modulated in accordance with said angular errors and affected by noise, comprising in combination: a. first means for providing said color video signal with said angular errors and said angle-modulated first reference signal; b. second means connected to said first means for separating said angle-modulated first reference signal from said color video signal; c. third means connected to said second means for filtering said angle-modulated first reference signal from said noise, said third means including first filter means imposing a first phase shift on said angle-modulated first reference signal; d. fourth means connected to said third means for receiving said phase-shifted angle-modulated and filtered first reference signal and for correcting said first phase shift to produce a second reference signal having an angular position which follows in a fixed relationship the angular position of said angle-modulated first reference signal prior to imposition of said first phase shift, said fourth means including buffer means for deriving a feedback signal from said second reference signal, second filter means connected to said buffer means for imposing on said feedback signal a second phase shift corresponding to said first phase shift, means connected to said first and second filter means for heterodyning said first reference signal having said first phase shift and said feedback signal having said second phase shift to produce a heterodyned signal, means connected to said heterodyning means for extracting from said heterodyned signal a difference signal corresponding to the frequency difference between said first reference signal having said first phase shift and said feedback signal having said second phase shift, means for providing a stable reference signal, means connected to said difference signal extracting means and said stable third reference signal providing means for deriving a phase-error signal varying in accordance with phase discrepancies between said stable third reference signal and said difference signal, and oscillator means connected to said phase-error deriving means for providiNg in response to said phase-error signal said second reference signal having said angular position, with said buffer means being connected to said oscillator means; e. fifth means connected to said first and fourth means for processing said color video signal with the aid of said second reference signal to dispose modulation components of said color video signal about a substantially stable carrier while substantially retaining phase and amplitude interrelationships of said modulation components.