CN104461194A - Spread spectrum capacitance type touch sensor - Google Patents
Spread spectrum capacitance type touch sensor Download PDFInfo
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- CN104461194A CN104461194A CN201410590526.XA CN201410590526A CN104461194A CN 104461194 A CN104461194 A CN 104461194A CN 201410590526 A CN201410590526 A CN 201410590526A CN 104461194 A CN104461194 A CN 104461194A
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- signal
- spread spectrum
- touch sensor
- noise
- capacitance type
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F3/00—Input arrangements for transferring data to be processed into a form capable of being handled by the computer; Output arrangements for transferring data from processing unit to output unit, e.g. interface arrangements
- G06F3/01—Input arrangements or combined input and output arrangements for interaction between user and computer
- G06F3/03—Arrangements for converting the position or the displacement of a member into a coded form
- G06F3/041—Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means
- G06F3/044—Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means by capacitive means
Abstract
A spread spectrum capacitance type touch sensor comprises a signal generator, a first multiplying unit, a touch screen, an amplifier, a second multiplying unit and a filter which are connected in sequence. One input end of the first multiplying unit and one input end of the second multiplying unit are connected with the random signal generator. The spread spectrum capacitance type touch sensor has the advantages that under the condition that an original capacitance type touch sensor is influenced by a noise signal with components the same as a driving frequency, the signal-to-noise ratio is greatly reduced, and the performance of the touch sensor may be reduced. However, by the adoption of the spread spectrum mode recommended in the spread spectrum capacitance type touch sensor, even if the noise signal with components the same as the D(t) frequency is received, the immunity to the noise signal can be greatly improved due to that fact that the loss of the signal-to-noise ratio is not large.
Description
Technical field
The present invention relates to a kind of spread spectrum capacitive touch sensors.
Background technology
The mode that current common touch sensor (touch sensor) adopts has resistance-type, condenser type, surface acoustic wave type, infrared-type etc.Although often kind of a mode has relative merits, and use of mobile product can multiple point touching more, the capacitive touch sensors that permanance is good again.
Capacitive touch sensors generally adopts the structure in Fig. 1.Optional frequency signal (drive singal) is sent by signal generator and to be received by sensor (touch panel) afterwards.Capacitive touch panel has according to having no touch, the characteristic that electric capacity changes.Thereupon, the change of electric capacity formed at touch-screen is by amplifier amplification, and increment signal becomes digital signal by A/D converter.Utilize the numerical data converted, judge that each coordinate has no touch according to touch sensible algorithm.
Because of capacitive reasons in structure, if when flowing into the noise with drive singal same frequency, the signal sent because of very difficult resoluting signal generator and noise signal, have the danger of malfunction.So, in order to solve problems generally adopt select the method for optimum frequency in sensor Received signal strength, send the signal of multiple frequency simultaneously after to be reduced the method etc. of noise by signal procedure.But these methods all belong to avoids noise frequency, selects the method for driving frequency, still there is the danger of malfunction from the frequency domain that noise is relatively few.
The touch sensor that capacitive touch sensors compares other modes has the shortcoming to noise signal weakness.As Fig. 2 (a) sends drive singal, and when sensor receives the noise signal in Fig. 2 (b) simultaneously, should the difference of noise signal the same as Fig. 2 (c) and drive singal need enough large.Now, the amplitude variations just by responding to drive singal determines whether touch.But if noise signal is the same with the frequency of drive singal, because of relative to noise, drive singal is large not fully, so be difficult to the signal to noise ratio (S/N ratio) (signal-to-noise ratio, SNR) meeting system requirements.Therefore, by the frequency domain that induced noise is very little, select the method for driving frequency many by what use.But, due to precision measurement noise grade at any time cannot be accomplished, so after selecting several frequency, maximum by what use by the method measuring these frequency band noise grades.But noise circumstance can continue along with the time to change, even if therefore use the danger of this method fault action also can only exist always.
Summary of the invention
The invention provides and a kind of adopt spread spectrum (spred spectrum) mode to improve method to noise signal immunity to capacitive touch sensors.
Technical scheme of the present invention is: a kind of spread spectrum capacitive touch sensors, comprise the signal generator, touch-screen, amplifier and the wave filter that connect successively, it is characterized in that, also comprise random signal generator, the first multiplier and the second multiplier, first multiplier is connected between this signal generator and described touch-screen, second multiplier is connected between amplifier and low-pass filter, and the output terminal of random signal generator is connected with an input end of the first multiplier and the second multiplier.
Described wave filter is that low pass is or/and Hi-pass filter.
The invention has the beneficial effects as follows: original capacitive touch sensors is when being subject to having the affecting of noise signal with driving frequency with sample ingredient, signal to noise ratio (S/N ratio) (signal-to-noise ratio, SNR) greatly will reduce, the performance of touch sensor may be reduced.But, adopt spread spectrum (spread spectrum) mode as suggested in the present invention, even if receive the noise signal of same D (t) frequency content, the immunity that the loss because of signal to noise ratio (S/N ratio) not quite will improve noise signal greatly.
Accompanying drawing explanation
Fig. 1 is the structural representation of conventional capacitive formula touch sensor;
Fig. 2 is the spectrogram of sensor shown in Fig. 1, wherein: (a) figure is sensor Received signal strength (drive singal) frequency spectrum, b () figure is frequency spectrum of noise signals, (c) figure is drive singal and noise spectrum schematic diagram;
Fig. 3 is the formation block diagram that the present invention adopts the capacitive touch sensors of spread spectrum (spread spectrum) mode;
Fig. 4 is spectrogram of the present invention, wherein (a) figure drive singal (X (t)), b () figure comprises the sensor of noise signal and the power (Y (t)) of amplifier, (c) figure final signal restores (Z (t)).
Embodiment
See Fig. 3 and Fig. 4, the invention relates to and spread spectrum mode is used for capacitive touch sensors and improves the method to noise signal immunity.
Spread spectrum (spred spectrum) certain signal message is distributed to wideband farmland and transmits the transmission mode making it periphery undesired signal (interference) to be produced to strong immunity.
The present invention can be used for capacitive touch sensors according to Fig. 3 structure.Signal generator sends the signal (D (t)) having optional frequency, and random signal generator sends the random signal (R (t)) that comparatively D (t) frequency has high bandwidth.D (t) takes advantage of the X (t) (drive singal) produced in R (t) to be dealt into touch panel.Fig. 4 (a) is the diagram of D (t), R (t) and X (t) frequency domain.The product of D (t) and R (t) becomes the convolution (convolution) of frequency domain.X (t) comprises D (t) signal message, and this information exists with the energy modalities of dispersion in wideband farmland.The change of the electric capacity that the amplitude of X (t) produces according to there being no touch according to sensor and modulating (modulation).Formed by signal (Y (t)) such as the conjunction of Fig. 4 (b) amplitude-modulated drive singal (α k X (t)) and noise signal (k N (t)) according to the change of electric capacity of sensor and amplifier.Y (t) takes advantage of the frequency content in R (t), D (t) to be restored again, and the noise signal that sensor receives will be distributed to wideband farmland.By low-pass filter (low pass filter, or Hi-pass filter (band pass filter LPF), BPF) remove the noise information part except D (t) frequency-portions in Z (t), D (t) amplitude variations can not be detected by noise information affects according to electric capacitance change.
Claims (2)
1. a spread spectrum capacitive touch sensors, comprise the signal generator, touch-screen, amplifier and the wave filter that connect successively, it is characterized in that, also comprise random signal generator, the first multiplier and the second multiplier, first multiplier is connected between this signal generator and described touch-screen, second multiplier is connected between amplifier and low-pass filter, and the output terminal of random signal generator is connected with an input end of the first multiplier and the second multiplier.
2. spread spectrum capacitive touch sensors according to claim 1, is characterized in that, described wave filter is that low pass is or/and Hi-pass filter.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201410590526.XA CN104461194A (en) | 2014-10-29 | 2014-10-29 | Spread spectrum capacitance type touch sensor |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201410590526.XA CN104461194A (en) | 2014-10-29 | 2014-10-29 | Spread spectrum capacitance type touch sensor |
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| CN104461194A true CN104461194A (en) | 2015-03-25 |
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| CN201410590526.XA Pending CN104461194A (en) | 2014-10-29 | 2014-10-29 | Spread spectrum capacitance type touch sensor |
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Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101310246A (en) * | 2005-11-15 | 2008-11-19 | 辛纳普蒂克斯公司 | Methods and systems for detecting a position-based attribute of an object using digital codes |
| CN101847068A (en) * | 2009-02-23 | 2010-09-29 | 晶门科技有限公司 | Method and apparatus for operating touch panel |
| CN102455815A (en) * | 2010-11-03 | 2012-05-16 | 矽统科技股份有限公司 | Touch sensing device and method thereof |
| CN102707855A (en) * | 2011-01-13 | 2012-10-03 | 三星电子株式会社 | Apparatus and method of identifying touch area |
| CN102736774A (en) * | 2011-04-08 | 2012-10-17 | 瑞鼎科技股份有限公司 | Driving and sensing method of touch input device and module thereof |
-
2014
- 2014-10-29 CN CN201410590526.XA patent/CN104461194A/en active Pending
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101310246A (en) * | 2005-11-15 | 2008-11-19 | 辛纳普蒂克斯公司 | Methods and systems for detecting a position-based attribute of an object using digital codes |
| CN101847068A (en) * | 2009-02-23 | 2010-09-29 | 晶门科技有限公司 | Method and apparatus for operating touch panel |
| CN102455815A (en) * | 2010-11-03 | 2012-05-16 | 矽统科技股份有限公司 | Touch sensing device and method thereof |
| CN102707855A (en) * | 2011-01-13 | 2012-10-03 | 三星电子株式会社 | Apparatus and method of identifying touch area |
| CN102736774A (en) * | 2011-04-08 | 2012-10-17 | 瑞鼎科技股份有限公司 | Driving and sensing method of touch input device and module thereof |
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Application publication date: 20150325 |
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