CN1164171A - Microphone expansion for background noise reduction - Google Patents
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- CN1164171A CN1164171A CN 97102209 CN97102209A CN1164171A CN 1164171 A CN1164171 A CN 1164171A CN 97102209 CN97102209 CN 97102209 CN 97102209 A CN97102209 A CN 97102209A CN 1164171 A CN1164171 A CN 1164171A
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Abstract
Disclosed is an apparatus for reducing background noise in a telecommunications device. The apparatus of the present invention include an amplifier having an input for receiving the electrical signals from the microphone and an output, said amplifier operable to receive electrical signals at the first input and provide amplification to the electrical signals to produce amplified electrical signals. The amplifier is further operable to provide amplification at a first gain level and a second gain level, said first gain level exceeding the second gain level. The apparatus also includes a feedback device connected to the output of the amplifier and further operably connected to control the operation of the amplifier. The feedback device is operable to cause the amplifier to provide two amplifications in different cases.
Description
The present invention relates to telephone field, particularly control the technology that background noise reduces according to the detection of listened to the voice signal that the substation microphone is presented.
The intrinsic problem of phone is to present background noise.In general, the microphone of phone receives speech signals and two of the background noises that produce at the environment that is arranged in microphone aspect signal.Background noise not only disturbs the calling subscriber, but also by this background noise the callee is disturbed in the influence of the speech signals of called subscriber's reception.In conference call, each conferenced parties is subjected to the influence of the combination background noise of all conferenced parties, so the special disturbance of background noise.
Concerning the calling party, the problem of background noise also influences the feedback in the substation that is referred to as " sidetone ".Sidetone is the calling party's voice signal sub-fraction that feeds back to receiver, so that telephone set is avoided calling party's sounding " quiet ".Sidetone can also make loud speaker that desirable level adjusted in its speech.In this case, promptly tell people to carry out orders calling subscriber's a ear to shield to hang oneself the calling subscriber's that air receives voice signal, conversation sound still can normally be passed to the calling subscriber.Yet when the calling subscriber kept silence, sidetone fed back and can disturb the calling subscriber to remove the background noise from calling subscriber's environment of the ability of tin callee's voice signal.At this moment, the calling subscriber can cover his/her another ear to his/her hand very naturally, rather than is placed on the telephone bandset with the shielding background noise.This practice does not have effect, because sidetone makes background noise can transmit and import into the ear that the calling subscriber answers a call through the receiver of phone.
At present, research and development reduce or eliminate the various apparatus and method that relate to background noise problem.For example, disclose a kind of telephone set in the 3rd, 691, No. 311 patents of the U.S., the amplifying signal that it receives the substation microphone has adopted the variation level of decay (or gain).Specifically be exactly: when detecting voice signal, the decay of signal is with regard to low (high-gain); Go to suppress effectively under the situation of background noise at the shortage voice signal, when promptly the calling subscriber does not send into microphone to sound of speech, the decay of signal just high (low gain).The another kind of phone that is used to suppress background noise when the calling subscriber does not talk is disclosed in the 5th, 235, No. 637 patents of the U.S..
Another device is AT﹠amp; The general voice signal of T company is regulated chip, and model is LB1068AC/AW (" adjuster ").It uses for commercial speaker-phone, can regulate the amount of suppression of sidetone and background noise according to the intensity of microphone signal by the level that changes decay.This adjuster comprises variable gain amplifier, and this amplifier is according to the detected voice signal that presents of adjuster or background noise provides different gain levels.
At AT﹠amp; In the adjuster of T, testing circuit determines that whether input signal is the signal of speaking of simple background noise.This input signal is supplied with variable gain amplifier subsequently.Testing circuit is set the Amplifier Gain level.Because testing circuit is to input signal detection, thus testing circuit in advance amplification input signal to reach the level value that is suitable for detecting.For this purpose, this adjuster also comprises the preamplifier in the testing circuit path.
The time of the conversion from the high-gain to the low gain that adjuster is used is called additional period, is 14ms (millisecond).Although it is acceptable that this short relatively additional period is used commercial speaker-phone and other, it may suppress conversation at the inter-syllable of conversation.It should be noted as AT﹠amp; The such noise suppressor of T adjuster is referred to as decay time in the used time of conversion from the low gain to the high-gain, also is very important.If decay time is oversize, conversation is suppressed by unwanted inhibition noise elimination.Thereby need provide a kind of have can not cause conversing the reaction that suppresses and the noise suppressor of decay time.
United States Patent (USP) the 4th, 847,897 described phones are attempted to eliminate accidental conversation and are suppressed.United States Patent (USP) the 4th, 847,897 disclosed phones have noise monitor, expander and according to detected be conversation or the amplifier that the variable level value of amplification only is provided for background noise.Noise monitor is discerned background noise by feature average time of checking the signal of telecommunication that microphone sends from conversation signal.Expander reduces Amplifier Gain and increases Amplifier Gain according to the detection of background noise according to the detection of background noise.More particularly, United States Patent (USP) the 4th, 847, No. 897 described phone is attempted by comparison microphone signal short term average (being about 50 milliseconds) being provided and comparing microphone signal long-term average (being about 4 seconds) and avoid conversation to suppress, here suppose that continuous conversation generally is not more than 4 seconds, be interrupted generally being no more than 50 milliseconds.Yet, as AT﹠amp; The T adjuster is such, carries out noise measuring at signal by using microphone signal before the variable gain amplifier.And, average time technology except having introduced the expansion time of finishing average computation, also introduced extra-pay.So it can be in demand with the simple noise suppressor of implementing effectively that a kind of low cost of manufacture and noise restraint method are provided.
Noise stop device has that to can be used in all-environment structure also be needed.For example, this equipment should be able to suppress the noise of the business telephone as background noise is bothered callee's commercial speaker-phone especially.This equipment also may be applied to Home Telephone, i.e. black phone and cordless telephone.In addition, wish that also noise stop device can be used for cell phone.
The invention provides a kind of microphone expansion that whether occurs providing gain-adjusted according to voice signal.Particularly, according to the level that detects microphone signal signal is amplified by high gain levels or low gain levels, it is detected that the back appears in the microphone signal gain-adjusted, thus the circuit element of the need that reduced and hysteresis further is provided.
The preferred embodiments of the present invention are the equipment that is used to reduce the background noise of telecommunication path device, and this telecommunication path device comprises the microphone that receives voice signal and background noise.This microphone can change voice signal and background noise into the signal of telecommunication.This equipment comprises having the input that receives the signal of telecommunication and the amplifier of output, the signal of telecommunication that this amplifier can receive the signal of telecommunication and provide amplification to be exaggerated with generation to the signal of telecommunication at input.This amplifier can also provide amplification quantity with first gain level and second gain level, and wherein first gain level surpasses second gain level.This equipment also comprises a feedback device that is connected to amplifier out, by the work of the control amplifier that is operably connected.Feedback device is exercisable, provide amplification quantity so that amplifier provides amplification quantity with first gain when receiving the signal of telecommunication that is exaggerated on feedback device has greater than the output of the amplitude of predetermined threshold and amplifier is had at feedback device when receiving the signal of telecommunication that is exaggerated on the output of the amplitude that is lower than predetermined threshold with second yield value.
Characteristics discussed above and feature of the present invention and advantage will be more readily apparent from reference to following detailed description and accompanying drawing.
Fig. 1 shows the block diagram of the exemplary embodiment of telephone bandset of the present invention;
Fig. 2 shows the block diagram of the exemplary embodiment of microphone expansion of the present invention;
Fig. 3 shows the gain relationship of the operational amplifier of the exemplary microphone expansion circuit among Fig. 2;
Fig. 4 shows the circuit diagram of the exemplary microphone expansion among Fig. 2.
Fig. 1 shows the block diagram according to the exemplary embodiment of telephone bandset 10 of the present invention.In this embodiment, telephone bandset 10 comprises power supply words unit, base 11 cordless portable parts that use and be divided into microphone part 12 and receiver part 14 from function.Telephone bandset 10 comprises a traditional microphone 16, be used for receiving from the calling subscriber and be positioned at environment any background noise audible signal and produce its signal of telecommunication.The signal of telecommunication from microphone 16 is amplified by audio frequency amplifier 17, gives microphone expansion 18 then.Mobile phone 10 is used for and unit, base 11 co-operation, and this unit, base 11 is communicated with mobile phone 10 through rf frequency or RF signal.Unit, base 11 also is connected (not shown) with the telecommunication path net.
In general, microphone expansion 18 comprises amplifier 18a and feedback device 18b.Amplifier 18a is a variable gain amplifier, has the input and the output that is connected compressor reducer 20 that are used to receive the signal of telecommunication.Amplifier 18a of the present invention is used for to receive the signal of telecommunication and to provide amplification quantity with first gain level and second gain level to the signal of telecommunication that receives, and its first gain level surpasses second gain level.Feedback device 18b connects the output of amplifier and the control end of the control amplifier 18a work that is operably connected.Specifically, feedback device 18b has when receiving the signal of telecommunication that is exaggerated on the output of the amplitude that is higher than predetermined threshold in fact amplifier 18a and provides amplification quantity with first gain level at feedback device 18b.Equally, feedback device 18b has when receiving the signal of telecommunication that is exaggerated on the output of the amplitude that is lower than predetermined threshold in fact amplifier 18a and provides amplification quantity with second gain level at feedback device 18b.Can also know in the going through of contact Fig. 2 below and Fig. 3 that the feedback device 18b in the preferred embodiment further can make amplifier have at feedback device 18b when receiving the signal of telecommunication that is exaggerated on the output of the amplitude that is approximately equal to predetermined threshold and provide amplification quantity with the 3rd gain level.
Be exaggerated signal subsequently respectively by compressor reducer 20 and 22 compression and the shapings of frequency shaping device by what microphone expansion 18 produced, this compressor reducer and reshaper are known device and equipment.Be compressed with the signal of shaping and be sent to unit, base 11 by radiofrequency launcher 24 from the microphone part 12 of mobile phone 10 subsequently.Unit, base as known technology generally comprises radio frequency receiver, radiofrequency launcher, frequency shaping device, audio frequency amplifier and hybrid circuit.It is online that the unit, base is delivered to telecommunication path to the signal of emission, this signal is sent on another telephone set (not shown) again.
Unit, base 11 is through the signal of telecommunication path net reception from another phone.These signals are sent to the receiver part 14 of mobile phone 10.Receiver part 14 comprises the device of known technology.Specifically, the receiver part 14 of mobile phone 10 comprises antenna 26 and the radio frequency receiver 28 that is used to receive the radiofrequency signal that is produced by unit, base 11.Received signal is subsequently by frequency shaping device 30 and expander 32 shaping and expansion respectively.Delivered to the earphone 17 that is used for the calling subscriber is presented audio signal through audio frequency amplifier 34 by the signal of shaping and expansion in the receiving unit 14.
In addition, calling subscriber's his speech that can hear that microphone 16 produces by sidetone coupling.As mentioned above, the signal by calling subscriber's generation on the microphone part 12 is given unit, base 11 through radiofrequency launcher 24.Circuit in the unit, base 11 is above-mentioned part coupling and the anti-receiving unit 14 of giving that transmits, so that sidetone to be provided.
Referring now to Fig. 2, Fig. 2 shows the part schematic diagram according to the exemplary embodiment of microphone expansion 18 of the present invention.The primary element of amplifier 18a comprises resistance R A, RB and a RF and an operational amplifier (" op-amp ") 44.Feedback device 18 further comprises circuits for triggering 40, low pass filter and rectifier 42.Microphone expansion also comprises input IN and output OUT.Operational amplifier has first and second input stages 45 and 46 and public output stage 47 respectively.Usually, expander 18 is used for promptly reducing background noise between silence periods when the calling subscriber does not talk facing to microphone.
Low pass filter comprises resistance 51 and electric capacity 52, and it is attempted by between rectifier 42 and the circuits for triggering 40.Circuits for triggering 40 in the exemplary embodiment comprise two twin-stage junction transistors in the differential pair structure.Circuits for triggering 40 connect reference voltage V at input 54
REFAnd the operational amplifier 44 that is operably connected is so that with the startup between mode to be described in detail below conversion controllably first input stage and second input stage.In other words, circuits for triggering are operably connected, to control the gain that microphone expansion 18 applies.
First and second input stages 45 and 46 are in the inverted structure and the same output stage 47 of common use separately.Feedback resistance RF is connected between the inverting input IN1 of the output OUT and first input stage 45.The inverting input IN1 of first input stage 45 also connects resistance R B, connects input IN through another series resistor RA again.Between the inverting input IN2 of the intersection point of resistance R A and RB and second input stage 46, also has connecting line 49.Such connection has been arranged, and in this embodiment, first feedback loop is just determined by RF that second feedback loop is just determined by RF and RB.The gain of holding output OUT from input IN is decided by effective feedback resistance of feedback loop ratio divided by effective input resistance.According to the input stage 45 or 46 that circuits for triggering 40 are selected, gain can be by setting with the row relational expression:
Low gain: G=RF/ (RA+RB)
High-gain: G=(RF+RB)/RA
Here V
OUT=V
ING
In operation, microphone expansion 18 receives the electrical input signal V that comprises from the phone tone signal of microphone circuit at input IN
INWith the signal V that comprises the signal of telecommunication that is exaggerated in output OUT output
OUTIn order to produce the signal of telecommunication that is exaggerated, microphone expansion is by an amplification input signal V in two yield values
INThe selection of institute's using gain value is finished by circuits for triggering 40, promptly starts in two input stages 45 and 46 selectively, or its some combination.Operational amplifier 44 does not start and second input stage provides the low gain value when starting and start and second input stage 46 provides high-gain values when not starting in first input stage 45 in first input stage 45.Usually, microphone expansion 18 is at the detected output signal V of its output
OUTWhen surpassing predetermined threshold, i.e. when expression has speech or talk, provide high-gain values.On the contrary, when detecting output signal and be lower than threshold value, i.e. expression is not when speech or talk stop, and expander 18 provides the low gain value.
Input signal V
INSend into the IN1 of input separately and the IN2 of input stage 45 and 46 respectively.Suitable offset signal V
COMBe added to input stage 45 and 46 in-phase end separately.Operational amplifier 44 its output OUT provide by with the input stage 45 and 46 that is activated in the voice signal that amplifies of any relevant yield value.The high gain levels of present embodiment is 6dB, and low gain levels is 0dB.6dB difference between height and low gain provides than using the smooth transaudient conversion of big gain difference.Particularly, if gain difference is big especially, the conversion between 20dB for example, so high and low gain is with regard to highly significant.In addition, perhaps the use of big gain difference can make effective speech on the operational amplifier output terminal OUT and noise are differentiated the very difficulty that becomes.However, if expander 18 is set in speaker-phone, perhaps the 20dB gain difference can be fit to realize high inhibition level very much so.
The signal of telecommunication V that is exaggerated on the output OUT
OUTProvide feedback through rectifier 42, rectifier 42 is half-wave rectifiers here.The level and smooth subsequently rectified signal of low pass filter is to provide expression output OUT the signal V of output
OUTThe magnitude of voltage V that is essentially direct current of amplitude
RMSThis dc voltage value V
RMSBe added to this signal and reference voltage level V
REFThe input 53 of the circuits for triggering 40 of comparing.Half-wave rectifier provides reverse rectification output in the exemplary embodiment, like this, and amplitude V
OUTThe high more V of signal
RMSJust more little (more negative).So, if V
RMSBe lower than V in fact
REF, V so
OUTAmplitude greater than predetermined threshold is just arranged, thereby make circuits for triggering 40 that a signal that first input stage 45 is started is provided on circuit 56.Yet, if V
RMSIn fact greater than V
REF, circuits for triggering 40 just provide a signal to the input 56 of operational amplifier 44 so, first input stage 45 is not started and second input stage 46 is started.Yet, if V
RMSValue slightly near V
REFValue, circuits for triggering 40 are activated with regard to the combination that makes first and second input stages 45 and 46 so, thereby the yield value between high and the low gain value is provided effectively.Particularly, when first and second input stages 45 and 46 are activated, V
INA part accept low gain and amplify V
INA part accept high-gain and amplify, thereby all yield values between height and the low gain value are provided.
Suitable V
REFAnd V
COMThe selection of magnitude of voltage must be depended on information specific, comprises the measurement amplitude of the output signal of effective speech and background noise input signal.Those of ordinary skill in the art can easily be identified for the suitable numerical value of these means.
It should be noted that as the anti-phase rectifier of rectifier 42 only given by way of example.Those of ordinary skill in the art can easily use at circuits for triggering 40 and be designed to work as V
RMSGreater than V
REFHomophase rectifier under the situation of Shi Qidong first input stage 45.
Fig. 3 shows as V
RMSAnd V
REFBetween the gain of operational amplifier 44 of difference coefficient.Be positioned at V
RMS＜＜V
REFAnd V
RMSV
REFThe position between curve for using between low and the high-gain than smooth change.This smooth change causes than the micromutation gain conversions, otherwise will make the telephone talk can discontinuous sounding.Response curve shown in Figure 3 is to be produced by the output of the circuits for triggering 40 of Fig. 2 response.Hereinafter the circuits for triggering 40 of the exemplary embodiment that will further specify in conjunction with Fig. 4 comprise two common bipolar junction transistors that connect each self-electrode.The response characteristic of bipolar junction differential pair of transistors generally has shape shown in Figure 3.In another available embodiment, if do not use needed smooth transformation, 40 of circuits for triggering may have the ladder response.
The advantage that another is not represented in Fig. 3 of the present invention is the hysteresis that causes by the microphone signal intensity of measuring on the expander amplifier 18a output.Consider the expression permissible call signal significantly deliver to the situation that input amplifier provides high-gain, the downward startup of fluctuating or reducing can not cause second input stage 46 slightly of signal strength signal intensity (with reducing gain), this is because the signal that reduces is slightly still accepted high-gain, promptly keeps V with high numerical value
OUTSo that V
RMSEnough be lower than V
REFIf real low amplitude signal is delivered to IN, so V
RMSWill surpass V
REF, expander 18 will start second input stage 46.Like this, hysteresis just provides the service behaviour that is enhanced by the number of times that reduces variation accidental and that do not expect between height and low gain value.
Concerning any inhibition noise, noise suppression is used increases and also be die-away time important.In the embodiment of Fig. 2 and Fig. 3, attack time and die-away time all are 100 microseconds.Increase with die-away time and determine by the time constant of the low pass filter of resistance 51 and electric capacity 52 foundation.In experiment, determine best attack time and die-away time by user's knowledge and the resulting subjective judgement that the various times are used.It should be noted that microphone expansion 18 of the present invention has the attack time and the die-away time of the prior art of being significantly less than.For example, above-mentioned AT﹠amp; The adjuster of T company has 14 milliseconds attack time and 140 milliseconds die-away time.Resolution of the present invention is than good many of prior art, thereby the appearance that may cause the background noise in given call mode to suppress is howed a lot than prior art.
Fig. 4 has at length represented first embodiment of the microphone expansion 18 of the work according to the present invention.The suitable reference marker that Fig. 2 uses also is used for discerning the respective element of Fig. 4.Except as otherwise noted, the transistor that relates to below all is a bipolar junction transistor, and it has known base stage, collector and emitter.Element shown in Figure 4 can suitably be integrated on the monolithic semiconductor substrate.Yet, in available another embodiment, feedback resistance RA, RB and RF are not integrated on the substrate, but outside connection, so that allow yield value by the circuit designers adjustment.
Except following circuit element, expander 18 also comprise voltage bias point CC, FF (), COM and BA, signaling point IN1, IN2, RCT, RMS and REF.Expander 18 shown in Figure 4 also comprises first and second current mirror circuits 53 and 54.In the semiconductor embodiment of expander, bias point voltage for example all connects through plug to be provided from the outside directly or indirectly.In the following description, the voltage V of bias point or signaling point
xExpression, X is the reference marker that is used to discern bias point or signaling point here.For example, V
COMVoltage on the expression point COM.
Circuits for triggering 40 comprise transistor Q1 and the Q2 that its emitter joins.Circuits for triggering 40 further comprise the transistor Q4 that another its collector electrode is connected with the emitter of transistor Q1 and Q2.The grounded emitter of Q4.The base stage of transistor Q1 meets signaling point REF.
Point REF through R1 connect COM and through the resistance R 2A of transistor Q3 and series connection be connected with R2B FF ().The base stage of transistor Q3 connects reference voltage point BA.This connection makes forward voltage V
BABias transistor Q3 makes the resultant voltage through transistor Q3 emitter and resistance R 1A, R1B fall the current value of having set the current collection-emitter junction that flows through transistor Q3.This current value has determined to flow through the electric current of resistance R 1, thereby has determined the voltage drop of resistance R 1.So V
REF, equal to deduct the V of resistance R 1 voltage drop
COM, set by the resistance that changes resistance R 1.For example, increase the resistance of R1, the voltage drop of R1 just increases, and V
REFThen reduce.
In the present embodiment, resistance R 1, R2A and R2B are 25K Ω.In addition, the base stage of transistor Q3 is to the about 0.75V of voltage drop of emitter.In addition, V
COMAbout 1.8V, V
BAAbout 1.0V, they all provide from the outside.In this embodiment, flow through R2A, R2B and also flow through the electric current of R1 near 5 μ A simultaneously.So, V
REFEqual 1.8-(5 * 10
-6) (25K) or 1.675V.
The output of circuits for triggering 40 is combinations of transistor Q1 and Q2.The part of this output, promptly the collector electrode of transistor Q1 connects first current mirror circuit 53.Another part of this output, promptly the collector electrode of transistor Q2 connects second current mirror circuit 54.First current mirror circuit 53 connects first input stage, 45, the second current mirror circuits 54 and connects second input stage 46.
In more detail, first current mirror circuit 53 is made up of two PNP transistor Q5 and Q12, and its emitter all is connected to CC, and its each base stage links together.The collector electrode of transistor Q5 connects the output of differential pair, just connects the collector electrode of transistor Q1.Base stage and the collector electrode of transistor Q5 link together.Second current mirror circuit 54 also is made up of two PNP transistor Q6 and Q7, and two emitter also connects bias point CC respectively, and two base stage links together.Base stage and the collector electrode of transistor Q6 link together.In addition, the collector electrode of transistor Q4 connects the output of circuits for triggering 40,, connects the collector electrode of transistor Q2 that is.
First input stage 54 is made up of two transistor Q10 that connect with the differential pair form and Q11; Wherein, a differential pair input, promptly the base stage of transistor Q10 forms in-phase input end; Another differential pair input, promptly the base stage of transistor Q11 forms inverting input.In-phase input end connects COM, and inverting input connects IN1.Second input stage 46 comprises two transistor Q8, Q9 to be connected with first input stage, 45 similar modes, the inverting input of different just second input stages connect IN2.First and second input stages 45 and 46 each have the output of concatenation operation amplifier output stage 47.
The rectifier 42 of present embodiment has following array structure.This rectifier comprises the differential pair that PNP transistor QR2 and QR3 constitute, and their emitter interconnects.The base stage footpath resistance R R1 of transistor QR2 connects OUT.The base stage footpath resistance R R4 of QR3 connects COM, and is connected to RCT through resistance R R3.The collector electrode of QR2 and QR3 is connected respectively to the input of being made of current mirror circuit two NPN transistor QR4 and QR5.The collector electrode of transistor QR2 also connects the base stage of NPN transistor QX.The emitter of transistor QX connects ground FF, and its collector electrode connects the anode of voltage stabilizing didoe.Capacitor CCR is connected between the base stage and collector electrode of transistor QX.The negative electrode of voltage stabilizing didoe Z1 connects RCT.The emitter of QR2 and QR3 interconnects and is connected with the emitter of bias transistor QR1.
In a preferred embodiment of the invention, resistance R R1 is the resistance of 8.6K Ω, and resistance R R3 is the resistance of 45K Ω, and resistance R R4 is the resistance of 10K Ω.Capacitor C CR is the electric capacity of 2pf.
In operation, rectifier 42 receives the output signal of operational amplifier; Produce by the wave mode signal of rectification, i.e. V at its output
RCTBy the output signal of rectification basically by V
OUTNegative half period form.Low pass filter is smoothed to substantially dc voltage value to negative half period subsequently.This dc voltage value is represented mean value or perhaps V
OUTThe root-mean-square value of negative half period.This square root voltage V
RMSDeliver to an input of trigger 40 subsequently.Then, as the above, circuits for triggering 40 are according to V
RMSAnd V
REFBetween difference start in first input stage 45 and second input stage 46 one or both some parts.
Below, consider the corresponding effectively big output signal V of speech in more detail
OUTSituation.Big output signal will comprise the big negative variation of negative half period voltage.During these negative variations, the degree of QR2 trend conducting is greater than QR3.So, will cause the conducting of transistor QX through being emitted to of QR2-collector current.Because big electric current is by zener diode Z1, so voltage V
RCTReduce.Specifically, through the big voltage drop of electric current generation of voltage stabilizing didoe Z1, so V from COM to resistance R R3 and RR4
RCTCompare V
COMLow relatively.Low-voltage V
RCTDeliver to low pass filter, to produce with respect to V
COMLow V
RMSAs mentioned above because V
REFA little less than V
COMSo, the low V on the Q2 base stage
RMSTo cause transistor Q2 by and the conducting of transistor Q1.With this understanding, transistor Q1 makes electric current flow through transistor Q5, and then the transistor Q12 that flows through.The electric current that flows through transistor Q12 provides bias current to the transistor Q10 of the differential input that starts first input stage 45 and the emitter of Q11.And transistor Q2 does not allow to pass through from the electric current of Q6 collector electrode, thereby causes transistor Q6 and Q7 to end.Because transistor Q7 ends, thus the emitter of electric current inflow transistor Q7 and Q8 do not had, so that input stage 46 can not start.
As a result, the output V that has big negative voltage fluctuation
OUTOn large-signal cause to lead and start first input stage 45.When first input stage 45 is activated, be added to the input V of inverting input IN1
IN1Resistance R A, RB and the definite high-gain values of RF have been provided by Fig. 2.So always relevant with effective speech rather than relevant with background noise large-signal provides from being input to the high-gain values of output expander 18.
On output OUT than (when this situation perhaps appears at and only presents background noise) the small-signal, transistor QR2 is tending towards conducting with less degree.So transistor QR3 drags down the voltage on the transistor QX base stage thereby make by transistor QR4 and the definite current mirror circuit of QR5 to be tending towards conducting largely.With this understanding, transistor QX will be tending towards ending, or at least at very little degree conduction current.As a result, voltage stabilizing didoe Z1 flows through little electric current, causes voltage V
RCTBe elevated to V
COMHigh relatively V
RCTVoltage is delivered to low pass filter so that is provided near voltage V
COMThe voltage V of magnitude of voltage
RMSBecause V
RMSNear V
COMAnd V
REFBe slightly less than V
COM, so V
RMSCause turn-on transistor Q2 and cause making transistor Q1 to end.Transistor Q2 allows to flow through from the electric current of current mirror circuit 54, thereby has started second input 46.And transistor Q1 does not allow to flow through from the electric current of current mirror circuit, thereby can not start first input stage 45.Discuss like that in conjunction with Fig. 2 as top, because the annexation of resistance R A, RB and RF among Fig. 2, second input stage 36 provides from input IN2 to the low gain of exporting OUT.
Best is is transformed into the structure that the mode of dc voltage value is replaced exemplary rectification circuit 42 and low pass filter to output signal with another kind of.Specifically, can replace exemplary rectifier 42 and low pass filter shown in Figure 4 of the full-wave rectifier with electric current output of sum total parallel resistance one condenser network.The full-wave rectifier that is suitable for can be at compander available on the market (combination of compressor reducer and expander) integrated circuit, and for example the product of being made by Motorola and Signetics company obtains.
Although the embodiment of Fig. 1 comprises the residential cordless telephone machine, but those skilled in the art will know microphone expansion of the present invention and background noise compression method and can be used for any telephone set, no matter and whether this telephone set main application is used as dwelling house or commerce.Those of ordinary skill in the art can easily determine suitable attenuation value and be suitable for increasing and die-away time and their specific environment of special circuit.In case determined these suitable values, circuit just can be done suitable modification at an easy rate.
Those skilled in the art will know that also the microphone expansion 18 not necessarily such needs shown in the image pattern 1 is arranged in the telephone bandset.Although this set is best to cordless telephone, so that untreated mobile phone signal does not need to send on the Telephone set, microphone expansion is arranged in the mobile phone not necessarily.In addition, concerning have the phone that most of number electronic circuit is set in base, for example traditional cord telephone is preferably put into Telephone set to microphone expansion 18.Equally, all electronic devices that comprise microphone can be put into (being present in) telephone bandset, for example cell phone.
The technical staff also will know microphone expansion low cost of manufacture of the present invention and can be with effective and efficient manner work.Because noise suppression determines that in the output of expander do not need preamplifier between audio frequency amplifier that connects microphone and expander, prior art then needs preamplifier.The cancellation of preamplifier has not only reduced device cost, but also has eliminated the redundancy function as amplifying in the expander that appears at prior art in advance.In addition, the response of device is just as not needing the average time with the microphone received signal very effective.
Need to prove that the foregoing description is illustrative, those skilled in the art can easily imagine and develop other embodiment that embodies the principle of the invention and fall into the scope of the invention and spirit.
Claims (20)
1. equipment that is used for reducing telecommunication path device background noise, this telecommunication path device comprises the microphone that receives voice signal, this voice signal comprises voice signal and background noise, and this microphone can also be converted to the corresponding signal of telecommunication to voice signal, and this equipment comprises:
A) one has the input of the reception signal of telecommunication and the amplifier of output, described amplifier operationally receives from the corresponding electric signal of microphone and amplification quantity that corresponding electric signal is provided to produce the signal of telecommunication that amplifies at output at described input, described amplifier operationally provides amplification quantity with first yield value and second yield value, and described first yield value surpasses second yield value;
B) output and the feedback device that can be connected that is connected to amplifier with the work of control amplifier, this feedback device can make amplifier have at feedback device when receiving the signal of telecommunication that is exaggerated on the output of the amplitude that is higher than predetermined threshold to provide amplification quantity with first yield value and make amplifier to have at feedback device when receiving the signal of telecommunication that is exaggerated on the output of the amplitude that is lower than predetermined threshold and provide amplification quantity with second yield value.
2. equipment according to claim 1, it is characterized in that: described amplifier also comprises first input stage that is connected to input and second input stage that is connected to input, wherein, when first input stage be activated and second input stage when not starting amplifier provide first yield value and when second input stage be activated and first input stage when not being activated amplifier second yield value is provided.
3. equipment according to claim 2 is characterized in that: described amplifier comprises an operational amplifier, and its output connects first input stage through first feedback loop, and its output also connects second input stage through second feedback loop; Wherein first feedback loop influences first yield value, and second feedback loop influences second yield value.
4. equipment according to claim 1 is characterized in that: described feedback device comprises that converting electrical signal that a handle is exaggerated becomes the device of dc voltage value; Wherein, feedback device is exercisable, judges relatively whether the signal of telecommunication that amplifies is lower than predetermined predetermined threshold so that of selecting of amplifier provides amplification quantity by what use dc voltage value and reference voltage level from first yield value and second yield value.
5. equipment according to claim 4 is characterized in that: comprise a rectifier and a low pass filter being exaggerated the device that converting electrical signal becomes dc voltage value.
6. equipment according to claim 2 is characterized in that: above-mentioned feedback device comprises the device that the converting electrical signal that is exaggerated is become DC voltage level; Wherein, feedback device can make a startup of selecting in first input stage and second input stage by using dc voltage value and DC reference voltage value.
7. equipment according to claim 6 is characterized in that: described feedback device comprises the trigger that can be connected to first input stage, second input stage and be used for the converting electrical signal that is exaggerated is become the device of dc voltage value; Wherein, trigger depends on whether dc voltage value surpasses the DC reference voltage value and controllably and alternately start and do not start first input stage and second input stage.
8. equipment according to claim 7 is characterized in that: described circuits for triggering comprise first and second bipolar junction transistors (BJT), and each BJT has a base stage, a collector electrode and an emitter; Wherein the emitter of a BJT connects the emitter of the 2nd BJT, and the base stage of a BJT connects the DC reference voltage source, and the base stage of the 2nd BJT is operably connected and is used for being exaggerated the device that converting electrical signal becomes dc voltage value.
9. equipment according to claim 1 is characterized in that: first yield value surpasses the about 6dB of level of second yield value.
10. equipment according to claim 5 is characterized in that described low pass filter comprises resistance and electric capacity.
11. equipment according to claim 10 is characterized in that described low pass filter has the time constant that is approximately 100 microseconds.
12. equipment according to claim 3 is characterized in that operational amplifier and feedback device are integrated on the monolithic semiconductor device.
13. equipment according to claim 1 is characterized in that amplifier is integrated on the monolithic semiconductor device.
14. the method for the amplification quantity of the control signal of telecommunication in having the telecommunication path device of microphone, this method comprises:
A) provide the signal of telecommunication from the microphone to the amplifier;
B) utilize amplifier so that make one at least two yield values to come amplification signal, described at least two yield values comprise a high-gain values and a low gain value;
C) provide the signal of telecommunication that is exaggerated to feedback device;
D) use feedback device to determine the electrical signal amplitude that is exaggerated and the relation between the predetermined threshold;
E) be to make amplifier can use high-gain values to amplify continuous signal if the electrical signal amplitude that is exaggerated surpasses predetermined threshold.
15. method according to claim 14, this method comprises: if predetermined threshold surpasses the electrical signal amplitude that is exaggerated then makes amplifier can use low gain to amplify the step f) of continuous signal.
16. method according to claim 15, this method also comprises: make amplifier can use the combination of low gain value and high-gain values to amplify the step g) of continuous signal if the electrical signal amplitude that is exaggerated is approximately equal to predetermined threshold.
17. method according to claim 14 determines that wherein the step that is exaggerated the relation between the signal of telecommunication and the predetermined threshold comprises:
The converting electrical signal that is exaggerated is become the direct voltage of the electrical signal amplitude that expression is exaggerated;
Compare with the DC reference voltage value of representing predetermined threshold with dc voltage value.
18. equipment that is used to reduce the background noise of telecommunication path device, this telecommunication path device comprises the microphone that receives voice signal, this voice signal comprises voice signal and background noise, and this microphone can convert voice signal to the corresponding signal of telecommunication, and this equipment comprises:
A) operational amplifier, it has: one can be operationally connected to first input stage to receive the signal of telecommunication, one can be operationally connected to second input stage to receive the signal of telecommunication, with an output, this operational amplifier operationally provides amplification quantity to produce the signal of telecommunication that is exaggerated at its output to the signal of telecommunication, this operational amplifier is activated and second input stage operationally provides the amplification quantity of first yield value when not being activated and is activated and first input stage provides the amplification quantity of second yield value when not being activated when second input stage in first input stage;
B) rectifier that is connected to operational amplifier output terminal, rectifier operationally receive the signal of telecommunication that is exaggerated and produce by the signal of rectification;
C) low pass filter, it is operably connected rectifier to receive by the signal of rectification and operationally to produce dc voltage value, and this dc voltage value representative is exaggerated the amplitude of the signal of telecommunication; With
D) circuits for triggering, it connects low pass filter to receive dc voltage value, be also connected to control first input stage and second input stage startup and the control end of the operational amplifier of startup not separately, wherein, circuits for triggering depend on whether dc voltage value surpasses the DC reference voltage value and controllably and alternately start and do not start first input stage and second input stage.
19. equipment according to claim 18, it is characterized in that circuits for triggering comprise first and second bipolar junction transistors (BJT), each BJT has a base stage, a collector electrode and an emitter, wherein, the emitter of the one BJT connects the emitter of the 2nd BJT, the base stage of the one BJT connects the DC reference voltage source, the base stage of the 2nd BJT low pass filter that is operably connected.
20. an exercisable telecommunication path device that reduces background noise, this communicator comprises:
A) microphone that receives voice signal, this voice signal comprises voice signal and background noise, this microphone operationally converts voice signal to the corresponding signal of telecommunication;
B) one has the input of the reception signal of telecommunication and the amplifier of output, described amplifier operatively receives the corresponding electric signal and the signal of telecommunication of the amplification quantity that corresponding electric signal is provided to be exaggerated in the output generation from microphone therein, described amplifier operationally provides amplification quantity with first yield value and second yield value, and described first yield value surpasses second yield value;
C) one connects amplifier out and can be operatively connected feedback device with control amplifier work, when on feedback device has the output of the amplitude that is higher than predetermined threshold, receiving the signal of telecommunication that is exaggerated feedback device operationally make amplifier that the amplification quantity of first yield value is provided and when feedback device has the signal of telecommunication that reception is exaggerated on the output of the amplitude that is lower than predetermined threshold feedback device can make amplifier that the amplification quantity of second yield value is provided;
D) provide the device of the signal of telecommunication that is exaggerated to the telecommunication path net;
E) reception is from the device of the signal of telecommunication path net;
F) present the device of received signal in the audio signal.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 97102209 CN1164171A (en) | 1996-01-16 | 1997-01-10 | Microphone expansion for background noise reduction |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US585969 | 1996-01-16 | ||
| CN 97102209 CN1164171A (en) | 1996-01-16 | 1997-01-10 | Microphone expansion for background noise reduction |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN1164171A true CN1164171A (en) | 1997-11-05 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN 97102209 Pending CN1164171A (en) | 1996-01-16 | 1997-01-10 | Microphone expansion for background noise reduction |
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| Country | Link |
|---|---|
| CN (1) | CN1164171A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2021248350A1 (en) | 2020-06-10 | 2021-12-16 | Qualcomm Incorporated | Audio gain selection |
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1997
- 1997-01-10 CN CN 97102209 patent/CN1164171A/en active Pending
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2021248350A1 (en) | 2020-06-10 | 2021-12-16 | Qualcomm Incorporated | Audio gain selection |
| US11211910B1 (en) | 2020-06-10 | 2021-12-28 | Qualcomm Incorproated | Audio gain selection |
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