US 2008/0291338 A1 · Television receiver

Abstract

The present invention discloses that it enhances efficiency in detecting the color burst signal under low-power input and enables color display after confirming the presence of the color burst signal even under low-power input. The configuration includes firstly the electric field intensity judgment unit M1 which determines the electric field intensity as normal if the intensity of the inputted video signal is over a predetermined threshold value and as weak if equal to or below the same threshold; secondly the electric field intensity judging unit which, if the electric field is judged weak, starts pulsing from the latter half of the horizontal synchronization signal and generates the first burst gate pulse with the pulse width inclusive of the inserting position of the color burst signal as specified by the broadcasting signal protocol and, if judged normal, generates the second burst gate pulse with the pulse width inclusive of the standard inserting position and being narrower than the first burst gate pulse; and thirdly the burst gate unit which determines whether or not the color burst signal is detected within the extent of the first burst gate pulse or the second burst gate pulse.

Claims7

Dependent claims

A television receiver that detects presence or absence of a color burst signal in a video signal input, and that determines the video signal input is a color video signal if said color burst signal is present, and determines the video signal input is a black-and-white video signal if said color burst signal is absent, said television receiver comprising:

an electric field intensity determining unit determines that the electric field is normal intensity if the intensity of the video signal is higher than a predetermined threshold value, and that the electric field is weak intensity if the intensity of the video signal is equal to or lower than the predetermined threshold value;
a burst gate unit generates a first gate pulse that have a pulse width inclusive of a standard position of the color burst signal specified by the broadcasting signal protocol and starting from the latter half of horizontal synchronization signal when the electric field intensity determining unit determines the electric field is normal intensity;
the burst gate unit generates a second gate pulse that have a pulse width narrower than the first burst gate pulse and inclusive of the standard position when the electric field intensity determining unit determines the electric field is weak intensity;
the burst gate unit that detects the color burst signal within a range of one of a first burst gate pulse or a second burst gate pulse.

1 more element

A television receiver, comprising:

a tuner that selects a carrier frequency of a certain channel from video signal input through an antenna and converts the video signal to an output of intermediate frequency (IF),
an IF signal amplifier circuit that amplifies the IF signal to a necessary intensity at an amplification factor corresponding to IF-automatic gain control (AGC) voltage, and outputs the amplified signal,
a video detection circuit that extracts a decoding video signal from the IF signal and outputs the decoding video signal,
an automatic gain control (AGC) circuit that obtains a composite video signal from said video detection circuit and generates an IF-AGC voltage corresponding to the intensity of a synchronization signal of said decoding video signal,
a video signal processing circuit that performs amplification of the composite video signal output from said video detection circuit, carries out brightness/chroma (Y/C) separation to output brightness signal and carrier chrominance signal, and conducts synchronizing separation to output synchronizing signal,
a chrominance demodulation circuit that demodulates said carrier chrominance signal into a color-difference signal and outputs the color-difference signal by utilizing the frequency of a color burst signal when there is input of the color burst signal,
a matrix circuit that creates red-green-blue (RGB) signal as picture data by performing matrix conversion processing based on said brightness signal and said color-difference signal,
a liquid crystal driver circuit that displays pictures by driving a liquid crystal module based on said RGB signal, and
a microcomputer that controls said tuner, said IF signal amplifier circuit, said video detection circuit, said AGC circuit, said video signal processing circuit, said chrominance demodulation circuit, said matrix circuit, and said liquid crystal driver circuit, said television receiver further comprising:
a first register to store preset values of burst gate pulse (BGP) that starts pulsing in the latter half part of horizontal synchronization signal and has a pulse width inclusive of an inserting position of the color burst signal as specified in a broadcasting signal protocol, and
a second register to store preset values of BGP a width of which is narrower than the preset values stored in said first register, that is, the time from a start of the horizontal synchronization signal to an end of BGP being 7.559 to 8.500 microseconds and the time from the start of horizontal synchronization signal to a start of BGP being 4.500 to 4.596 microseconds,
said microcomputer
(i) receives input of the decoding video signal from said video detection circuit along with the IF-AGC voltage from said AGC circuit,
is in oscillation in the frequency of chrominance subcarrier, and
measures electric field intensity of airwaves incoming to the antenna according to said IF-AGC voltage,
(ii) if said electric field intensity is higher than a threshold value in terms of voltage, determines that the electric field is normal, and acquires the preset values of the BGP for normal electric field intensity from said first register,
if said electric field intensity is equal to or lower than the threshold value in terms of voltage, determines that the electric field is weak, and acquires the preset values of the BGP for weak electric field intensity from said second register,
(iii) generates the BGP in accordance with the preset value thus acquired,
applies synchronous detection to a portion covered within a range of the BGP of the video detection output,
detects if any frequency signal synchronous with the frequency of said chrominance subcarrier is contained continuously for a preset number of cycles or more,
determines if any color burst signal is present within the range of the BGP,
when the synchronous detection proves affirmative, the detected color burst signal is output to said chrominance demodulation circuit,
if the detected color burst signal is not output to said chrominance demodulation circuit, the synchronous detection proves negative.

20 more elements

Dependencies are inferred from the claim text.

Television receiver

Life of this patent

Television receiver

Life of this patent

Abstract

Claims7