Automatic fine tuning with phase-locked loop and synchronous detection

Claim 2

In a color television receiver apparatus having a tuner for amplifying and converting a radio frequency carrier signal on a selected television channel and modulated by chroma, picture and sound information to one of an intermediate frequency by the action of a mixer and a variable frequency, voltage controlled local oscillator, an automatic fine tuning and modulation detection arrangement unresponsive to quadrature distortion components, in integrated circuit form, comprising in combination: a limiter formed by a pair of transistors connected in differential amplifier configuration having a first input, a second input coupled to a point of reference potential, and a pair of outputs; low pass filtering means coupled to the tuner local oscillator for selectively controlling the output frequency thereof; a phase comparator formed by a pair of transistors in differential amplifier form having a pair of inputs selectively coupled to the outputs of said limiter, a pair of outputs coupled to said low pass filtering means, and a pair of common electrodes connected in common; a reference oscillator formed by a pair of transistors connected in differential amplifier configuration having frequency determining elements for rendering an output thereof operative at a predetermined video frequency; a doubly balanced synchronous detector formed by first, second and third pairs of transistors having input, output and common electrodes, the respective outputs of said first transistor pair being connected to said common electrodes of said second and third pairs of transistors connected in common, respectively; means for applying said converted intermediate frequency carrier signal to said first input of said limiter and also to one input of said first transistor pair forming said synchronous detector; and means for coupling the output of said reference oscillator to said common electrodes of said phase comparator and to a selected one of said inputs of each of said second and third transistor pairs of said synchronous detector, the other of said inputs to each of said first, second and third transistor pairs forming said synchronous detector being connected to said point of reference potential.

Claim 3

In a color television receiver apparatus having a tuner for amplifying and converting a radio frequency carrier signal modulated by signal components including chroma, picture and sound information on a selected television channel to an intermediate frequency signal by the action of a mixer and a variable frequency voltage-controlled local oscillator, and having an intermediate frequency amplifier which exhibits a predetermined frequency bandpass characteristic in which each of said signal components is assigned a predetermined location for weighted amplification thereof, an automatic fine tuning and modulation detection system for accurately positioning the signal components of a converted carrier within the frequency bandpass of the intermediate frequency amplifier while eliminating quadrature distortion and intercarrier buzz, comprising in combination: a phase-locked control loop, including phase comparator means receiving the converted intermediate frequency signal from the intermediate frequency amplifier, and low pass filtering means, coupled to the tuner local oscillator for selectively controlling the output frequency thereof; a synchronous detector receiving the converted intermediate frequency signal from the intermediate frequency amplifier; a reference oscillator coupled to the phase comparator means and to the synchronous detector for supplying each with a reference oscillator signal at a predetermined video frequency; and phase shift means for shifting the relative phase of the reference oscillator signal and the intermediate frequency signal by 90* so as to establish a substantially zero degree phase difference between the reference oscillator and intermediate frequency signal inputs to the synchronous detector, the frequency of the reference oscillator signal being selected to cause the phase comparator means to achieve a condition of phase lock such that said oscillator and intermediate signal inputs thereto have a relative phase difference of substantially 90* and such that the local oscillator causes the converted chroma, picture and sound signal components to be accurately positioned at their predetermined frequency locations in the frequency bandpass of the intermediate frequency amplifier.

Claim 4

In a color television receiver apparatus having a tuner for amplifying and converting a radio frequency carrier signal modulated by signal components including chroma, picture and sound information on a selected television channel to an intermediate frequency signal by the action of a mixer and a variable frequency voltage-controlled local oscillator, and having an intermediate frequency amplifier which exhibits a predetermined frequency bandpass characteristic in which each of said signal components is assigned a predetermined location for weighted amplification thereof, an automatic fine tuning and modulation detection system for accurately positioning the signal components of a converted carrier within the frequency bandpass of the intermediate frequency amplifier while eliminating quadrature distortion and intercarrier buzz, comprising in combination: a phase-locked control loop, including phase comparator means receiving the converted intermediate frequency signal from the intermediate frequency amplifier, and low pass filtering means, coupled to the tuner local oscillator for selectively controlling the output frequency thereof; a synchronous detector receiving the converted intermediate frequency signal from the intermediate frequency amplifier; a reference oscillator coupled to the phase comparator means and to the synchronous detector for supplying each with a reference oscillator signal at a predetermined video frequency; and phase shift means for shifting the relative phase of the reference oscillator signal and the intermediate frequency signal by 90* so as to establish a substantially zero degree phase difference between the reference oscillator and intermediate frequency signal inputs to the synchronous detector, the frequency of the reference oscillator signal being selected to cause the phase comparator means to achieve a condition of phase lock such that said oscillator and intermediate signal inputs thereto have a relative phase difference of substantially 90* and such that the local oscillator causes the converted chroma, picture and sound signal components to be accurately positioned at their predetermined frequency locations in the frequency bandpass of the intermediate frequency amplifier.

Claim 5

An automatic fine tuning and modulation detection arrangement in accordance with claim 2 wherein said low pass filtering means exhibits an essentially dual frequency response characteristic comprising a first, extended range of a given response level and a second, substantially narrower range having an increased response with respect to said given response level.

Claim 6

An automatic fine tuning and modulation detection arrangement in accordance with claim 3 wherein said second narrower range of increased response comprises the low frequency portion of the overall frequency response characteristic of said low pass filtering means.

Claim 7

An automatic fine tuning and modulation detection arrangement in accordance with claim 4 wherein the overall response range of said low pass filtering means is approximately 750 kHz with said narrow range exhibiting said increased response characteristic encompassing less than one-tenth said overall response range.

Claim 8

An automatic fine tuning and modulation detection arrangement in accordance with claim 2 wherein an error signal is generated at the output of said phase comparator on detected differences between the applied intermediate frequency carrier signal and the signal applied from the reference oscillator, and further wherein said error signal is in the form of an alternating current non-sinusoidal beatnote having a direct current component at frequencies removed from said desired video frequency, with said error signal changing to one of essentially direct current when said phase-locked loop is operating at or near lock-up at said desired video frequency.

Claim 9

In a television receiver having a tuner for converting a selected radio frequency carrier signal modulated with luminance signal information, processing signal information and fortuitous noise components to one of an intermediate frequency, said television receiver including a luminance signal information channel and a signal processing channel which includes sync separator means and automatic gain control means, a video detection and noise suppression system comprising: a synchronous detector having an input circuit for receiving said intermediate frequency signal and an output circuit, said synchronous detector demodulating all of said information and noise components; noise suppression means coupled between the output circuit of the synchronous detector and said luminance signal information channel for reducing the noise components presented to said luminance signal information channel; and means connecting the output of the synchronous detector to said signal processing channel, thus providing the sync separator means and automatic gain control means with a demodulated video signal containing unsuppressed noise components while the luminance signal information channel receives the video signal with the noise components suppressed.

Claim 10

In a television receiver having a tuner for converting a selected radio frequency carrier signal modulated with luminance signal information, processing signal information and fortuitous noise components to one of an intermediate frequency, said television receiver including a luminance signal information channel and a signal processing channel which includes sync separator means and automatic gain control means, a video detection and noise suppression system comprising: a synchronous detector having an input circuit for receiving said intermediate frequency signal and an output circuit, said synchronous detector demodulating all of said information and noise components; noise suppression means coupled between the output circuit of the synchronous detector and said luminance signal information channel for reducing the noise components presented to said luminance signal information channel; and means connecting the output of the synchronous detector to said signal processing channel, thus providing the sync separator means and automatic gain control means with a demodulated video signal containing unsuppressed noise components while the luminance signal information channel receives the video signal with the noise components suppressed.

Claim 11

In a television receiver as set forth in claim 7 wherein said noise signal information in the output of said synchronous detector is bipolar, and wherein said noise signal reducing means passes noise information of substantially one polarity only.

Claim 12

In a television receiver as set forth in claim 8 wherein said noise signal reducing means comprises a zener diode coupled across said luminance signal information channel.

Claim 13

In a color television receiver apparatus having a tuner for amplifying and converting a radio frequency carrier signal modulated by signal components including chroma, picture and sound information on a selected television channel to an intermediate frequency signal by the action of a mixer and a variable frequency, voltage-controlled local oscillator, and having an intermediate frequency amplifier which exhibits a predetermined frequency bandpass characteristic in which each of said signal components is assigned a predetermined location for weighted amplification thereof, an automatic fine tuning, synchronous detection and white noise suppression system for accurately positioning the signal components of a converted carrier within the frequency bandpass of the intermediate amplifier while eliminating quadrature distortion and intercarrier buzz and providing a noise-suppressed video signal for use in a video processing channel, comprising in combination: a phase-locked control loop, including phase comparator means receiving the converted intermediate frequency signal from the intermediate frequency amplifier, and low pass filtering means, coupled to the tuner local oscillator for selectively controlling the output frequency thereof; a synchronous detector receiving the converted intermediate frequency signal from the intermediate frequency amplifier; a reference oscillator coupled to the phase comparator means and to the synchronous detector for supplying each with a reference oscillator signal at a predetermined video frequency; phase shift means for shifting the relative phase of the reference oscillator signal and the intermediate frequency signal by 90* so as to establish a substantially zero degree phase difference between the reference oscillator and intermediate frequency signal inputs to the synchronous detector, the frequency of the reference oscillator signal being selected to cause the phase comparator means to achieve a condition of phase lock such that said oscillator and intermediate signal inputs thereto have a relative phase difference of substantially 90* and such that the local oscillator causes the converted chroma, picture, and sound signal components to be accurately positioned at their predetermined frequency locations in the frequency bandpass of the intermediate frequency amplifier; a video processing channel; a sync separation and processing channel; noise suppressing means for suppressing whiter-than-white noise above a predetermined reference level; means for coupling the output of said synchronous detector to said sync separation and processing channel and also to said noise suppressing means; and means for coupling the output of said noise suppressing means with whiter-than-white noise suppressed to said video processing channel.

Claim 14

In a color television receiver apparatus having a tuner for amplifying and converting a radio frequency carrier signal modulated by signal components including chroma, picture and sound information on a selected television channel to an intermediate frequency signal by the action of a mixer and a variable frequency, voltage-controlled local oscillator, and having an intermediate frequency amplifier which exhibits a predetermined frequency bandpass characteristic in which each of said signal components is assigned a predetermined location for weighted amplification thereof, an automatic fine tuning, synchronous detection and white noise suppression system for accurately positioning the signal components of a converted carrier within the frequency bandpass of the intermediate amplifier while eliminating quadrature distortion and intercarrier buzz and providing a noise-suppressed video signal for use in a video processing channel, comprising in combination: a phase-locked control loop, including phase comparator means receiving the converted intermediate frequency signal from the intermediate frequency amplifier, and low pass filtering means, coupled to the tuner local oscillator for selectively controlling the output frequency thereof; a synchronous detector receiving the converted intermediate frequency signal from the intermediate frequency amplifier; a reference oscillator coupled to the phase comparator means and to the synchronous detector for supplying each with a reference oscillator signal at a predetermined video frequency; phase shift means for shifting the relative phase of the reference oscillator signal and the intermediate frequency signal by 90* so as to establish a substantially zero degree phase difference between the reference oscillator and intermediate frequency signal inputs to the synchronous detector, the frequency of the reference oscillator signal being selected to cause the phase comparator means to achieve a condition of phase lock such that said oscillator and intermediate signal inputs thereto have a relative phase difference of substantially 90* and such that the local oscillator causes the converted chroma, picture, and sound signal components to be accurately positioned at their predetermined frequency locations in the frequency bandpass of the intermediate frequency amplifier; a video processing channel; a sync separation and processing channel; noise suppressing means for suppressing whiter-than-white noise above a predetermined reference level; means for coupling the output of said synchronous detector to said sync separation and processing channel and also to said noise suppressing means; and means for coupling the output of said noise suppressing means with whiter-than-white noise suppressed to said video processing channel.

Claim 15

Automatic fine tuning, synchronous detection and white noise suppression arrangement in accordance with claim 10 wherein said phase-locked control loop further includes a limiter coupled between the selected intermediate frequency amplifier and saiD phase comparator means, and further wherein a phase shifter network is coupled between said reference oscillator and said synchronous detector.

Claim 16

Automatic fine tuning, synchronous detection and white noise suppression arrangement in accordance with claim 11 wherein said phase comparator means, limiter, reference oscillator, synchronous detector, phase shifter and noise clipper are designed in integrated circuit form for inclusion on a single, monolithic substrate chip.

Claim 17

Automatic fine tuning, synchronous detection and white noise suppression arrangement in accordance with claim 10 wherein said control means of said noise clipper is in the form of a zener diode means having a conduction level corresponding to maximum white level in the composite video signal as processed by said synchronous detector.