CN2120413U

CN2120413U - Video signal processor

Info

Publication number: CN2120413U
Application number: CN 92207178
Authority: CN
Inventors: 唐薇娟; 刘光明
Original assignee: Xidian University
Current assignee: Xidian University
Priority date: 1992-04-13
Filing date: 1992-04-13
Publication date: 1992-10-28

Abstract

The utility model relates to a background noise and towing point interference suppressing circuit of a television, which solves the problems of high frequency noises formed by white noises of video signals or brightness and color mutual mix, and poor towing point interference cleaning effect. The background noise and towing point interference suppressing circuit of a television is composed of an amplifier, a comb filter, limiters, an integrator and a brightness and noise suppression device. Color and brightness passages are respectively connected with a noise suppression circuit which is composed of two groups of threshold limiters and can suppress brightness and color background noises. Mix brightness interference signals can be taken out from the brightness and noise suppression circuit by low pass, reversed phase limiting and comparison. Interference signals which are higher than a reference voltage adopt a connecting mode of output a control signal with a door, and the towing point interference can be cleaned.

Description

Video signal processor

The utility model relates to electronic applications, particularly a kind of background noise that suppresses television set with drag an interfered circuit.

The family expenses PAL of the existing homemade or import of China _D(line-by-line inversion quadrature amplitude balance system, and adopt comb filter to separate two components of carrier chrominance signal) band that generally uses of broadcast television receiver logical with trap Y/C partition method, caused bright, look to scurry mutually, aggravated the background noise of brightness and chrominance channel, signal to noise ratio is descended; If use comb filtering Y/C partition method, though can suppress interference bright, that look is scurried formation mutually, in some distinguishingly square interference of dragging that has become horizontal direction.

1, about background noise.Owing to just the big impulse disturbances in the intermediate-frequency channel is suppressed in the prior art, and white noise in the vision signal or high-frequency noise bright, that look is scurried formation is not mutually taked braking measure, thereby make its video screen background images that variegated punctate sensibility be arranged.Especially on the large-area colour image, the colour noise point of scurrying look formation is particularly serious, even causes tonal distortion.When contrast increases, during the saturation enriching, more than this phenomenon more obvious.Simple 2H comb filtering is bright, the look partition method can not suppress this phenomenon very effectively even adopted.Though Coring or " baselineclipper " circuit of eliminating this background noise abroad arranged, but because the general processing signals on the zero level baseline all of these relevant circuit, need add positive and negative two kinds of power supplys, simultaneously because these circuit mostly adopt the pressure drop of diode PN junction as the noise suppression threshold level, thereby cause threshold level too high again, can not debug, and small-signal is caused problems such as distortion.U.S. Pat .4268864(1981 for example) be exactly sort circuit.U.S. Pat .4179705(1979) " Coring " circuit that adopts the NPN double-triode valve to do, but need to use phase inverter, thereby just inevitably to produce the phase shift problem.

2, about dragging an interference.Existing television set adopt comb filter to videoblankingsync bright, when look separates, when, look bright when existing between the signal adjacent lines suddenlys change or tone suddenlys change, will be on the horizontal edge of TV image, exist the chequered with black and white point-like of two row carrier frequencies to disturb, this interference is called drags an interference.External claim " Hanging dog ".The existence of this interference will make vertical resolution reduce.PAL _DSystem is than NTSC(quadrature amplitude balance system) dragging of system a little many delegation, and effect is more serious.At present, solve the interference of dragging in the TSC-system abroad, most adopt combed colourity and comb luminance signal earlier through detection again the output signal after thresholding is controlled mutually " with " as logic control signal.But this method not only can not well be eliminated and drag an interference for the comb filter of ultrasonic delay line, and can bring when luminance signal medium-high frequency component more for a long time (for example multi-burst signal) with the also corresponding problem that eliminates of this high fdrequency component.US.4240105(1980 for example) just there is this problem in patent.In addition, adopt delay 1H to detect the formed control signal of non-correlation in the ranks in this patent, also can only eliminate PAL _DDrag an interference during the 1H of system, drag an interference, also increased low pass type 1H delay line simultaneously, make its price higher and can not eliminate second row.

The purpose of this utility model is to provide a kind of noise suppression effective at above-mentioned the deficiencies in the prior art, and circuit is simple, and the noise suppression level is adjustable, and can eliminate major part and drag an interference, and is suitable for PAL _DSystem with the noise of TSC-system, drag the inhibition circuit of an interference.

Realize that the utility model purpose technical scheme is that noise suppression circuit is connected in TV chrominance channel and the high frequency luminance passage, soon combed the brightness high fdrequency component and combed carrier chrominance signal and be connected respectively in two identical background noise suppression circuits, to eliminate vision signal white noise or high-frequency noise bright, that look is scurried formation mutually.

The utility model eliminate the scheme drag an interference be the rectification high fdrequency component from the brightness noise suppression circuit be connected to low pass filter through anti-phase amplitude limiter to comparator, from comparator divide again two-way one tunnel directly to door, a passing point device arrives another comparator again.Composite video signal to inverting amplifier, again is divided into comb filter and to wave detector two-way, signal its output of entering wave detector be connected to another comparator from the signal of this inverting amplifier output by high pass filter.When vision signal when the vertical direction of picture has bright, look sudden change or tone sudden change, the high level phase of three comparator outputs " with " control signal of back output, drag an interference with elimination.When vision signal is multi-burst signal or details composition when many, the comparator output low level is arranged, with the door no-output, can guarantee that then the brightness radio-frequency component of having combed all exports.

Noise suppression circuit of the present utility model constitutes the differential type thresholding amplitude limiter formed of pipe and peripheral cell and emitter follower by two groups.Its noise suppression level is a noise signal that needs are suppressed and adjustable dc voltage is superimposed direct current difference after subtracting each other with reference voltage as the relative threshold level of noise suppression, and the general the AC signal of noise suppression output to the video channel of television set.

Followingly describe structure of the present utility model and operation principle in detail with reference to accompanying drawing.

Fig. 1 is a theory diagram of the present utility model

Fig. 2 is that the utility model suppresses the background noise first embodiment circuit diagram

Fig. 3 is the second embodiment circuit diagram that the utility model suppresses background noise

With reference to Fig. 1, the utility model comprises high pass filter, inverting amplifier, comb filter, low pass filter, anti-phase amplitude limiter, comparator and integrator.Behind the composite video signal process high pass filter (1) in the video channel, wherein brightness high fdrequency component and chromatic component are added in the inverting amplifier (2), after amplifying, paraphase divide two-way to connect, one the road is connected to comb filter (3), one the road is connected to wave detector (12), from the brightness of the comb high fdrequency component Y of this comb filter output _hComb carrier chrominance signal C and be connected respectively to noise suppression device (4) and (5).Bright, the look AC signal of noise suppression are exported in two noise suppression devices (4) and (5).

From noise suppression device (4), take out the rectified brightness high fdrequency component Y that combed _hSignal is connected to low pass filter (6), is connected to comparator (8) by anti-phase amplitude limiter (7), and the output of comparator (8) is divided into two-way, and one the tunnel is input to and door (11), and one the tunnel is input to integrator (9) enters comparator (10) again.When the cross luma interference magnitude surpasses reference level E ₁The time, comparator (8) is just exported a high level, this high level one tunnel is directly connected to and door (11), one passing point relatively back is also exported high level from comparator (10), when vision signal is that multi-burst signal or details composition are when many, comparator (10) output low level with the door no-output, is all exported to guarantee the brightness high frequency composition that TV has been combed.Become the video channel that total luminance signal enters into television set after the high frequency composition of this output and the addition of brightness low frequency composition.In order to guarantee that inverting amplifier (2) output hour, export with door (11) also no signal, wave detector (12) and comparator (13) have been set up in the circuit again, be that composite video signal is passed through high pass filter (1) and is connected to inverting amplifier (2), the output of inverting amplifier (2) is divided into two-way, one the tunnel enters comb filter (3), and one the road is connected to wave detector (12), enters comparator (13) by detection.In the vertical direction of picture, when sudden change of bright, look or tone sudden change, three comparators are all exported high level through dragging an interference with door (11) and control signal control logic switch elimination of back output.

Noise suppression circuit shown in Figure 2 is to pipe Q by triode ₁Q ₂And Q ₃Q ₄Two groups of differential type thresholding amplitude limiters forming and peripheral element and emitter follower formation.To pipe Q ₁Q ₂And Q ₃Q ₄One side base stage be connected with coupling capacitance C respectively ₁, C ₂With biasing resistor R ₂, R ₁₀And thresholding is regulated resistance R ₁, R ₉, the another side base stage is connected with fixed voltage E ₀To pipe Q ₁Q ₂And Q ₃Q ₄Emitter be connected with the buffer resistance R that improves output waveform respectively ₄, R ₅, R ₆, R ₇And load resistance R ₃With R ₈Pass through capacitor C from the brightness high frequency ac signal of comb and the colourity AC signal of comb filter output ₁, C ₂Be connected respectively to Q ₁Q ₂And Q ₃Q ₄The A of two thresholding amplitude limiters, B 2 points are superimposed with this adjustable dc voltage of 2, more respectively with fixed voltage E ₀Subtract each other, its DC potential difference can be used as the relative threshold level of noise suppression.By subtracting each other for being lower than fixed voltage E ₀Superposed signal then pass through resistance R ₃Through E _CCTo ground, and be higher than fixed voltage E ₀Superposed signal then pass through resistance R ₈To ground.The AC signal of noise suppression is passed through isolation resistance R from M, N at 2 respectively ₁₁, R ₁₂Be connected to emitter follower Q ₅The base stage addition, from Q ₅Emitter output.

Whole noise suppression circuit uses single supply, and upper and lower thresholding is regulated resistance R ₉, R ₁0 to (E ₀Adjustable in the scope of)/2.

Noise suppression circuit shown in Figure 3 is to regulate resistance R with two ₁And R ₉Be connected to two groups to pipe Q ₁Q ₂With Q ₃Q ₄Base stage.Regulate resistance R ₁The Lower Threshold level of scalable noise suppression circuit is regulated resistance R ₉The Upper threshold level of scalable noise suppression circuit.

The utility model is owing to be connected its noise suppression circuit in the chrominance channel and high frequency luminance passage of television set, thereby can improve the separation ratio of comb filter, effectively eliminates the white noise or the high-frequency noise bright, that look is scurried formation mutually of vision signal; Because taking out rectification high fdrequency component from the brightness noise suppression device, the utility model employing passes through low pass simultaneously, anti-phase amplitude limit and the high level of relatively afterwards exporting with reference voltage, there are being high level bright, output when look suddenlys change or tone suddenlys change and back to export the connected mode of control signal with other two comparators (10) and (13), therefore, both can effectively eliminate and drag an interference, can guarantee again when vision signal be multi-burst signal or details composition when many, the brightness high frequency composition of having combed is all exported; In addition because, noise suppression circuit of the present utility model adopts single supply and with two groups of differential type thresholding amplitude limiter structures to the pipe composition, and the noise suppression threshold level is a relative value, its adjustable range can be from 0 volt to supply voltage half, both can handle large-signal, also can handle small-signal, do not produce any time delay or phase shift,, not only can be used for the TV video camera so be with a wide range of applications, the analog composite video signal of TV receiver, the noise suppression of luminance video and carrier chrominance signal, and can be used for other analog signal, as AM(amplitude modulation), DSB(double-side band) and the noise suppression of speech signal the monolateral band of SSB().

Claims

1, a kind of background noise with drag point interference suppressing circuit, include high pass filter, inverting amplifier, comb filter, low pass filter, anti-phase amplitude limiter, comparator, integrator is characterized in that:

A, at the output of comb filter, promptly in brightness and chrominance channel, be connected with two respectively and suppress the vision signal white noises or bright, look is scurried noise suppression circuit (4) and (5) that form high-frequency noise mutually;

B, from brightness noise suppression device (4), draw rectified bright frequency component be connected to low pass filter (6) through anti-phase amplitude limit (7) after, be connected to negative terminal and its reference level E of amplitude comparator (8) ₁Compare, export a high level signal and be connected to and door (11) and integrator (9);

C, the signal of exporting from integrator (9) are connected to comparator (10) and reference level E ₂Compare, its output signal is connected to and door (11);

D, composite video signal are connected to inverting amplifier (2) by high pass filter (1), and the output of inverting amplifier is connected respectively to comb filter (2) and wave detector (12), and comparator (13) is received in the output of wave detector (12) repeatedly; The high level of the high level of comparator (13) and comparator (10) output and comparator (8) output mutually " with " after, export the control signal that an interference is dragged in a controllable logic switch removing.

2, circuit according to claim 1 is characterized in that noise suppression circuit (4) and (5) are to pipe Q by two groups ₁Q ₂And Q ₃Q ₄Differential type thresholding amplitude limiter of forming and peripheral cell and emitter follower constitute, to pipe Q ₁Q ₂And Q ₃Q ₄One side base stage be connected with coupling capacitance C respectively ₁, C ₂With biasing resistor R ₂, R ₁₀And go up Lower Threshold and regulate resistance R ₁, R ₉, the another side base stage is connected with fixed voltage E ₀, to pipe Q ₁Q ₂And Q ₃Q ₄Emitter be connected with the buffer resistance R that improves output waveform respectively ₄, R ₅, R ₆, R ₇And load resistance R ₃, R ₈

3, inhibition circuit according to claim 1 and 2 is characterized in that, look AC signal bright from the comb of comb filter output pass through capacitor C ₁, C ₂Be connected respectively to A, B 2 points of thresholding amplitude limiter, be superimposed with this adjustable dc voltage of 2, more respectively with fixed voltage E ₀Subtract each other, its DC potential difference is as the relative threshold level of noise suppression, and is lower than fixed voltage E ₀Superposed signal pass through resistance R ₃Through power supply E _CCThe back is to ground.Output to emitter follower Q ₅Collector electrode, be higher than fixed voltage E ₀Superposed signal pass through resistance R ₈Ground connection, the AC signal of noise suppression is passed through isolation resistance R from M, N at 2 respectively ₁₁, R ₁₂Be connected to emitter follower Q ₅The base stage addition, from Q ₅Emitter output.

4,, it is characterized in that upper and lower thresholding adjusting resistance R according to the inhibition circuit shown in the claim 2 ₉, R ₁Also can be connected to Q ₁Q ₂And Q ₃Q ₄Between two groups of base stages to pipe.