CN85103122A - Reduce the noise device - Google Patents

Abstract

The present invention is one and reduces the noise device.Its means are with the modulated wave used of regeneration voice signal, are demodulated to voice signal, allow this voice signal by making it to change the phase shifter of phase place again, thereby obtain dephased binary signal.Meanwhile, with what had in the device, in two paths of this binary signal, when switching the regeneration track successively, synchronous with this switching, and in the modulated wave of regeneration, in case drop-out is arranged, the holding circuit of just devoting oneself to work is exported the sum signal of the output signal of these two holding circuits, to scheme to reach the purpose that reduces noise.

Description

Reduce the noise device

The invention relates to the gyromagnetic head dummy magnetic recorder/reproducer of spiral scan mode.This device is along the rotary track that is contained in (at least one) magnetic head on the right cylinder, the tape spiral fashion is twined, rotate given angle, with said head voice signal is write down successively, regenerates to the recording track unit that becomes vergence direction with the tape longitudinal direction.

During with spiral scan mode magnetic recorder/reproducer record, regeneration voice signal,, when making regeneration track Qie Change, in sinusoidal wave voice signal, produce noise to the track of vicinity though regenerate down successively with the recording track unit that tape vertically becomes.In addition, in the signal of magnetic head regeneration, drop-out is arranged, also produce noise.This is owing to during the recording voice signal, adopt warbled cause.In order to reduce this noise, the method that adopts of past is: when drop-out occurring when Qie Change regeneration track or in the regenerated signal, produce noise during this period of time in, make the voice signal voltage of demodulation keep sinusoidal wave.Though the noise of result's spike pulse shape has been lowered like this, but brought the disadvantage that keeps the waveform generation difference of position and original sound signal.

The object of the present invention is to provide one to reduce the noise device.Wish to accomplish that Ji does not make original wave form distortion, the noise that drop-out produces occurs in noise that produces in the time of reducing owing to reproduce head track Qie Change again and the regenerated signal.

In order to achieve the above object, the present invention has adopted following technological means:

The present invention includes first holding circuit that keeps applied signal voltage, make this input signal produce phase shift phase-shift circuit, keep second holding circuit of the output signal voltage of phase shifter, detecting device that the walkaway that produces in the input signal is come out and the parts such as totalizer of the output signal addition of above-mentioned first, second holding circuit, and make it to have during above-mentioned sensors work the function that first, second holding circuit keeps.

Adopt above-mentioned technological means, its effect is as follows:

In above-mentioned technological means, in case produce noise in the input signal, detecting device just detects the noise of generation, makes first, second holding circuit keep noise to produce voltage before.Meanwhile, because phase shifter makes the phase place of these voltages produce skew, so that magnitude of voltage has produced difference.After adding these signals, make and obtain revising between the noise range of output signal, do not had the signal Suo Zhi Change that is similar to original waveform of noise.

As mentioned above, when in the demodulation of detuner output, producing noise, allow holding circuit work.Because with not having the Xin Zhi Change, the regeneration that are similar to original waveform of noise, so that the present invention reduces anti noise is very big.And, when the drop-out time of modulated wave that should demodulation is elongated, owing to manage to export certain voltage, so can eliminate the noise that is produced with detuner.

The description of the drawings:

First figure is a circuit block diagram that reduces noise device concrete instance of the present invention.Second figure, the 3rd figure are the movement oscillograms of the first figure each several part.The 4th figure is the circuit block diagram of another concrete instance.The 5th figure, the 6th figure are the working waveform figures of the each several part of the 4th figure.

Concrete instance:

According to figure one an explanation concrete instance of the present invention.

The 1st, the input end of the modulated wave of regeneration.The 2nd, detecting device, it can detect the size of the modulated signals that is input to input end 1.The 3rd, detuner.4, the 6th, amplifier.5, the 10th, switch, when detecting device 2 one work, they just are (of) state that cut-offs.7, the 11st, keep electric capacity.The 8th, output terminal.The 9th, receive all pass circuit of the output terminal of amplifier 4.It is by operational amplifier 9a and receive resistance 9b, the 9c of the feedback of operational amplifier 9a, non-feedback input end respectively, and the output terminal of concatenation operation amplifier 9a and the resistance 9d of feedback input end and the non-feedback input end and the electric capacity 9e between the ground that receive operational amplifier 9a form.The 10th, switch, it is corresponding actions with detecting device 2 work, and the output F of all pass circuit 9 is passed to the input end of amplifier 6.The 11st, capacitor, its is connected to the input end of amplifier 6, other end ground connection.The 12nd, resistance, it connects the output terminal of switch 5 and the input end of amplifier 6, and, the 12nd, work as the totalizer that capacitor 7 and 11 two end-point voltages are added up mutually.In addition, form holding circuit respectively by switch 5 and capacitor 7 and switch 10 and capacitor 11.

The waveform of each several part of first figure has drawn among second figure.The following describes routine working condition.

At first, the modulated wave D from the recording medium of video tape and so on is come by the detecting device 2 of input end 1 and detection signal size, is become signals such as sound or music by detuner 3 demodulation ， Bian Change.Zoomed into signal E by the signal of demodulation by amplifier 4, through all pass circuit 9 become in the audible frequency range, the high frequency phase delay time is the signal F of P.Signal F becomes signal H by being in closure (on) state of switch 10, after amplifier 6 further amplifies, passes to output terminal 8 again.Can the driving electric amplifier at output terminal 8 output signal H ', make the loudspeaker sounding.Input end at amplifier 6 is connected to the capacitor 11 that keeps usefulness, though by being in closure (on) state of switch 5 and potentiometer 12, be superimposed upon on the output signal E of amplifier 4, but because the output impedance of all pass circuit 9 designs very lowly, so in audible frequency range, can not exert an influence to frequency characteristic.

Usually just can regenerate like this, hear and be recorded the signal that medium write down., when in recording medium scar being arranged, just produce drop-out in the regeneration modulated wave, detuner 3 just produces noise at the drop-out position.Describe the course of work of this situation below in detail.

Be added among the modulated wave D of input end 1, produce drop-out and the level of modulated wave when very little, make detecting device 2 work, switch 5 and 10 is (of) state that cut-offs.Therefore, the noise that produces in detuner 3 just can not pass to output terminal 8.Become this point when cut-offfing (of) state at switch 5 and 10, make the capacitor 7 of the output terminal of receiving switch 5 keep producing the output voltage of the amplifier 4 before the noises; Make capacitor 11 keep the output voltage of all pass circuit 9.Because the output signal F of all pass circuit 9, than input signal also Calipering be amplifier 4 output signal E time delay P, so the voltage that keeps on the capacitor 7 equals the magnitude of voltage that all pass circuit 9 is exported behind time P.Yet because follow potentiometer 12 between capacitor 7 and 11, so the difference of capacitor 7 and 11 voltages that keep diminishes gradually.Also Calipering is the input voltage of the amplifier 6 that connected of capacitor 11, switch 10 be cut-off (of) state after, the change in voltage that after output voltage P time delay of all pass circuit 9, is reached.Second there is shown this course of work.Symbol D～H ' among second figure represents the symbol D～H ' of each several part among first figure.Shown in second figure, if the time of drop-out is short, can reproduces and be similar to original signal, it is big to reduce anti noise than the past.And time of drop-out when long, shown in the 3rd figure, that voltage after at this moment keeping two end-point voltages of capacitor 7 and 11 to equate, thus reduced noise.Symbol D～H ' among the 3rd figure has identical meaning with second figure.Moreover by noise and restituted signal ratio that drop-out produces, high fdrequency component is many, and by all pass circuit 9, time delay is also little, obtains the waveform as second figure.

Though above be illustrated about the situation that produces drop-out, equally also can reduce because during the discontinuous magnetic track of regenerating in turn that video tape write down the modulating wave of generation discontinuous and the noise of the demodulation output that causes.In this case, during Zai Qie Change regenerative track, with detuner 3 produce noises during, for example the magnetic track Qie Change signal of 10 microseconds is corresponding, switch 5 and 10 is for cut-offfing (of) state for well.

According to the 4th figure another concrete instance is described below.The part identical with first figure in the 4th figure gives jack per line, just illustrates and omitted.

The 13rd, capacitor, one terminate to the output terminal of amplifier 6.The 14th, with capacitor 13 parallel resistor.The 15th, amplifier links to each other with the other end of capacitor 13.Form differentiator by amplifier 15 and capacitor 13.

To be added to input end 1 from the frequency modulated signal J after the next regeneration of recording mediums such as video tape with regenerative loop (not drawing among the figure).This signal J, by the detecting device 2 of detection signal size, after detuner 3 demodulation, Bei Bian Change becomes signals such as sound or music.Signal after the demodulation zooms into signal K by amplifier 4, by being in closure (on) state of switch 5, behind amplifier 6 further amplifications, passes to output terminal 8.Can the driving electric amplifier in output terminal 8 output, make the signal L of loudspeaker sounding.Though the input end of amplifier 6 is connected to electric capacity 7 and the potentiometer 12 that keeps usefulness, because the output impedance of amplifier 4 designs very lowly, so in audible frequency range, frequency characteristic is not exerted an influence.Usually just can regenerate and hear the signals that recording medium write down such as video tape like this., adopted revolution to change the spiral scan mode magnetic recorder/reproducer of magnetic head and since the magnetic track of record do not connect around, so modulated wave is just discontinuous during regeneration, and when on the tape scar is arranged, in the modulated wave of regenerating, just produce drop-out.In the time of this, in the discontinuous position of modulated wave and drop-out position detuner 3, produce noise.Working condition when below describe in detail producing this drop-out.

Before producing drop-out, as mentioned above, can obtain demodulation output at output terminal 8.Then, make demodulation output be added to amplifier 15 by capacitor 13 and potentiometer 14, capacitor 13 and amplifier 15 combine and use as differentiator, can obtain at the output terminal of amplifier 15 demodulation output and demodulation output differential value and.The output of amplifier 15 by being in closure (on) state of switch 10, is added on the capacitor 10, by after the potentiometer 12, is added to the input end of amplifier 6 again.When the level that produces drop-out, modulated wave diminishes, make detecting device 2 work, switch 5 and 10 become (of) state that cut-offs.The noise of detuner 3 generations just can not pass to output terminal 8 like this.Become point when cut-offfing (of) state at switch 5 and 10, make capacitor 7 keep producing the output voltage of the amplifier 4 before the noises, the output voltage of capacitor 11 hold amplifiers 15.The output voltage of amplifier 15 is owing to the differential value that includes the output of amplifier 6, so when the output voltage of amplifier 6 increased, the output voltage of amplifier 15 was than the input voltage height of amplifier 6; When the output voltage of amplifier 6 reduced, the output voltage of amplifier 15 was lower than the input voltage of amplifier 6.Also Calipering is when producing drop-out, and switch 5 and 10 becomes when cut-offfing (of) state, and the voltage difference of capacitor 7 and two end points of 11 has just represented to produce the change direction of the demodulation output voltage before the drop-out.And this magnitude of voltage is owing to being connected on the resistance 12, so fade away.At this moment the voltage at the two ends of capacitor 7 and switch 5 and 10 are when cut-offfing (of) state and compare, and the direction that changes to the demodulation output voltage changes.This course of work is illustrated on the 5th figure.Symbol J, K among the 5th figure, L represent each several part signal J, K, the L among the 4th figure.Working condition when the expression drop-out time is long among the 6th figure.As seeing among the 5th figure, the 6th figure, when the drop-out time in short-term, can reproduce approximate original signal, so it is bigger than passing by to reduce anti noise; When time of drop-out is long, have any problem though differentiate original signal waveform, can keep the both end voltage of capacitor 7 and 11 to become that magnitude of voltage after equating, thereby also reduce noise.At this moment from the input end of amplifier 6, supply with capacitor 7 electric currents, the voltage at capacitor 7 two ends when making demodulation output approach no signal is for well.

Though be to be illustrated above with regard to the situation that produces drop-out,, equally also can reduce since successively regenerative recording on the tape do not connect around magnetic track the time, the noise of the caused modulation of the uncontinuity of the modulated wave of generation output.During ， Qie Change regenerative track, corresponding in this case with magnetic track Qie Change signal, make switch 5 and 10 in modulated wave is in the discontinuous time for example in 10 microseconds, be in and cut-off (of) state for well.

Above though what talk is an end of capacitor 13 and potentiometer 14, receive the example of the output terminal of amplifier 6, an end of capacitor 13 and potentiometer 14, receive the output terminal of amplifier 4 and can work too.Just because the enlargement factor of amplifier 6 is not enough, so must increase the enlargement factor of amplifier 15.

Claims (4)

1, reduce the noise device: this apparatus features is: by first holding circuit that keeps applied signal voltage and make above-mentioned input signal phase shift phase shifter, keep this phase shifter output signal voltage second holding circuit, can detect the detecting device of the noise that produces in the input signal and the totalizer etc. of the output signal addition of above-mentioned first, second holding circuit is partly formed, and has during sensors work the function that above-mentioned first, second holding circuit is kept.

2, phase shifter is made of differentiator, is the reduction noise device that is documented in the claim 1.

3, phase shifter is made of all pass circuit, is the reduction noise device that is documented in the claim 1.

4, the input signal of differentiator become holding circuit output signal be documented in reduction noise device in the claim 2.

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