CN105136334B - A kind of SAW delay line type wireless sensor system with anti-collision - Google Patents

Abstract

The present invention provides a kind of SAW delay line type wireless sensor system with anti-collision.Transponder sensing chip input transducer is using coding interdigital transducer (associated transducer), and it is encoded to the compatible code for belonging to same compatible code character, using the transponder of same compatible code coding chip, referred to as similar transponder.On transponder sensing chip, at least two same frequency output interdigital transducers arranged along sound channel.Similar transponder chips, the initial delay distance of first output transducer and input transducer, each chip are different from each other；The spacing of each output transducer is consistent；Design it is above-mentioned respectively apart from when, should make to measure in the range of examination in nominal sensing, after similar transponder is with caused electromagnetic echoes superposition, all echo peaks should be able to all be differentiated by reader, know its source and heat transfer agent.Reader has the addressable part of compatible code.The anti-collision of the system is multiplied by sequential capacity equal to inhomogeneity transponder species number.

Description

A kind of SAW delay line type wireless sensor system with anti-collision

【Technical field】

The present invention relates to surface acoustic wave wireless sensor, more particularly to a kind of saw delay with anti-collision Line style wireless sensor system.

【Background technology】

Power network device temperature monitors in real time, is the basic means of intelligent grid, and the market demand is urgent.Due to power network Particular surroundings, conventional temperature sensor can not be applied, and be internationally recognized more excellent using surface acoustic wave wireless transducer telemetry technology Scheme.

Surface acoustic wave (Surface Acoustic Wave, the SAW) wireless sensing based on Principles of Radar developed in recent years Device, extraneous power supply is not required to, strong antijamming capability can be in various adverse circumstances (such as high temperature, strong electromagnetic and nuclear radiation etc.) Middle reliably working, it is the supplement of conventional IC sensors, the base components of Internet of Things will be turned into, in modern industry, agricultural, traffic Its unique effect is played with the field such as environmental protection.

The operation principle of SAW wireless sensers is：Probe (transponder) the surrounding environment physical quantity of sensor, chemical quantity and The change of biomass can cause the skew of wherein SAW sensing chips electrical characteristic, and surrounding can be just monitored by detecting these skews The parameters such as environmental physicses amount, chemical quantity and biomass, will in individual identification (label), physics, chemistry, bio-sensor system There is very big application prospect.

For example, National Power System direct economic loss caused by snow disaster is about 40,000,000,000 yuan at the beginning of 2008, national snow is accounted for The 22.3% of disaster loss mistake.If power network overhead transmission line temperature can directly be monitored using SAW radio temperature sensors, and take Strong precautionary measures, so that it may greatly reduce these losses.Particularly nuclear power station in Japan accident in 2011, make it was recognized that disliking The sensor of energy normal work is how important in bad environment.If nuclear power station arrangement SAW wireless sensers, in real time at any time Danger zone temperature is detected, just can make nuclear power station effective operation and safety, promote the extensive use of following nuclear power source.

Unless stated otherwise, when that will not misunderstand, this specification will save " wireless " Liang Zi in " wireless senser " Slightly.

Without loss of generality, we illustrate concerns of the present invention by taking commonly used temperature sensor as an example.

Now, surface acoustic wave sensor system, using Principles of Radar, by reader, transponder and background process three It is grouped into, Fig. 1 illustrates its fundamental block diagram.Transponder is sensor probe, only by surface acoustic wave sensing chip, miniature antenna and It is applicable packaging part to form, is passive and wireless part.Reader produces transmitting, echo signal reception processing, backstage by driving pulse The circuit such as interface and control and dual-mode antenna composition.Background process is system application layer.At present, the interrogation pulse of reader transmitting It is rectangle single frequency carrier pulse, the transducer that electro-acoustic-electric translation function is realized on chip is the interdigital transducing of corresponding conventional uniform Device, its length coordinate pulse width.

The operation principle of sensing system is as follows：Reader actively launches interrogation pulse, by the miniature reception antenna of transponder After reception, the input interdigital transducer of feed to surface acoustic wave sensing chip.When interrogation pulse parameter and input interdigital transducer During parameter similar, due to (inverse) piezo-electric effect, high frequency echo can be produced, and reading is sent back to by the miniature transmitting antenna of transponder Device.Because echoing characteristics (frequency, phase, delay etc.) is easily influenceed by sensing chip local environment, therefore returned by what reader received Ripple has carried sensor probe local environment feature, such as temperature etc..So processing echoing characteristics, you can reach real-time telemetry Purpose.

The mechanism of echo is produced according to surface acoustic wave sensing chip, surface acoustic wave wireless sensor chip can be divided into three kinds：

The first is SAW resonator type (Fig. 2), and its transponder chips is exactly the sound for having proper temperature characteristic Surface resonator, it make use of the high Q resonance characteristic of SAW resonator, now transponder miniature antenna transmit-receive sharing.

Resonance cake core, by with its resonant frequency similar in interrogation pulse be forced to excitation when, acoustic energy can be accumulated interdigital In the acoustic resonance structure that transducer forms with reflecting grating array.After interrogation pulse stopping, the acoustic energy accumulated can be converted to electromagnetism Ripple, and outwards launch decay high frequency echo.The frequency of this decay high frequency echo, it is the natural resonance frequency of SAW resonator Rate, it is relevant with resonator chip local environment feature, its temperature characterisitic is compared by the frequency received, you can realize telethermograph Function.

Other two kinds are saw delay types, because the velocity of sound is more much lower than velocity of electromagnetic waves, the sensing that reader receives Electromagnetic echoes, than interrogation pulse delay long period (being more than 1us) of transmitting, hence it is evident that improve the interference free performance of reader (Fig. 1).

First, i.e. second, it is saw delay reflection-type (Fig. 3), its transponder chips is by an interdigital transducer Formed with multiple distant bonding jumper battle array reflecting gratings (reflecting grating group).Interdigital transducer is used as input/output acoustic-electric simultaneously Inverting element, and bonding jumper battle array reflecting grating radical is seldom, reflectivity is also small, is that sound echo produces structure.Reader transmitting inquiry Pulse, after being received by transponder reception antenna, encourage caused ping after chip interdigital transducer, delay transit to bonding jumper At battle array, after reflecting, multiple sound echo impulses are produced, and returns to interdigital transducer and is changed into high-frequency electromagnetic echo again, are beamed back Reader.Now dual-mode antenna is shared that echo is multiple reflection peak strings.Because chip can be influenceed by local environment, instead Penetrating characteristic (such as reflection peak spacing) can change therewith, the reflection characteristic change of reader analysis echo, so that it may realize remote measurement work( Energy.

It is SAW delay line type (Fig. 4, Fig. 5), its transponder chips is interdigital by an input second, being the third Transducer and multiple distant short output interdigital transducers (output transducer group) form multi output delay line.Reader is sent out Interrogation pulse is penetrated, after being received by transponder reception antenna, ping caused by excitation input interdigital transducer, delay transit is to respectively Output transducer, high-frequency electromagnetic echo is produced, reader is beamed back by transponder transmitting antenna.Transponder can use transmitting-receiving altogether With single antenna construction (Fig. 4), transmitting-receiving separate antenna structures (Fig. 5) can be also used.It is short interdigital transducing to sense echo and produce structure Device group, electromagnetic echoes are multimodal string.Because chip can be influenceed by local environment, echo transmission characteristic (such as peak-to-peak away from) can be with Change, reader analysis echoing characteristics change, so that it may realize telemetry function.

By the effort of nearly more than ten years, though many producers have developed multiple pilot systems both at home and abroad, because scene is dry Disturbing to solve, and cause popularization and application to be obstructed.For example, in power grid cabinet real time temperature measurement, because multiple electric power cabinets connect Afterwards, power bus-bar makes the undamped propagation of wireless sensing high-frequency signal, and reader reception signal is that multiple sensing echoes are overlapped mutually, Need system that there is anti-collision.For example, an electric power cabinet group typically has twenty or thirty, such as each electric power cabinet installs nine should Device is answered, the anticollision number of system is at least wanted to reach sufficient real requirement 200 more.

Anticollision surface acoustic wave sensor, just refer in reader effective range, even if there are multiple sensors while depositing Also some sensor senses information can accurately obtained.Surface acoustic wave sensor now, the essential anti-collision of transponder It is weaker.

When using SAW resonator type transponder, the nearly 1MHz bandwidth of each transponder needs, and radio frequency band Resource is less than 10MHz, i.e. anticollision number is up to ten.

Saw delay type sensor, existing goods typically produce structure (reflecting grating group or output interdigital using echo Transducer group) initial delay time difference, i.e. time division mechanism, to realize anti-collision.Allow to place on sensing chip and sense The when base location number of echo generation mechanism, referred to as sequential capacity, illustrate chip essence anti-collision, with chip size, read It is relevant to read device performance and electrode lay-out etc., general most tens.Such as German Ai Dikelai Merck diagnostic companies (LDIC) frame The RITHERM wireless and passive SAW temperature-sensing systems that empty line temperature monitors in real time, anticollision number are only 5 (Fig. 6 A and figures 6B)。

Expand the anti-collision of surface acoustic wave sensor using software algorithm, though getting along with, practical prospect is uncertain.

【The content of the invention】

We in granted patent ZL2010101761425 " acoustic surface wave passive radio frequency identification tag and sensor ", A kind of label chip that conventional uniform interdigital transducer is replaced using coding interdigital transducer (associated transducer) is disclosed, to carry The technology of high SAW ID-tag capacity, it is substantially exactly the distinctive code selectivity of associated transducer using compatible code coding, Code division mechanism is realized, to obtain the anti-collision of chip.

We are public in " a kind of saw delay reflection-type wireless senser with anti-collision " is applied for a patent A kind of saw delay reflection-type wireless sensor system that anti-collision is realized using code division time division way is opened, it is led It is that the conventional uniform interdigital transducer on existing saw delay reflection sensor chip is changed into correlation to change to want innovative point Energy device, the code selectivity using associated transducer to coded pulse, realizes anti-collision.

Due to the delayed reflex type wireless senser, reflecting grating group is employed as sensing echo generation mechanism.Though tool There is the characteristics of antijamming capability is good, but echo amplitude is small, and modulated by associated transducer, add the complexity of reader. Thus, we are improved the patent.

A kind of SAW delay line type wireless sensor system with anti-collision is proposed in the present invention, including should Device, reader and background processing unit are answered, the surface acoustic wave sensing chip that transponder uses, it inputs acoustic-electric and changes usable routine Uniform interdigital transducer is encoded interdigital transducer (associated transducer) replacement.

The coding of associated transducer, to belong to the compatible code of same compatible code character, using the sound table of same compatible code coding The transponder of face ripple sensing chip, forms similar transponder.Belong to the compatible number of codes of same code character, be referred to as the compatible code character Degree, that is, the species number of inhomogeneity transponder.

The surface acoustic wave sensing chip that transponder uses, it is output transducer group that it, which senses electromagnetic echoes generation mechanism, extremely Few same frequency output interdigital transducer arranged by two (generally three) along sound channel is formed.

To similar transponder chips, its initial delay distance, i.e. first output transducer and input associated transducer Distance, each chip are different from each other；Spacing between each output transducer is consistent；Design it is above-mentioned respectively apart from when, should make nominally sensing Measuring in the range of examination, after similar transponder is with caused electromagnetic echoes superposition, all echo peaks should be able to all be differentiated by reader, Know its source and heat transfer agent.

The reader of SAW delay line type wireless sensor system, there is the generating means of compatible code.

The present invention, the degree (i.e. inhomogeneity transponder species number) that its anti-collision is equal to compatible code character are multiplied by sequential appearance Amount.For example, the degree of compatible code character is 8, sequential capacity is 40, and institute's citing sensor anticollision number is 8*40=320, meets big portion Divide real requirement.

Compared with prior art, beneficial effects of the present invention：

The present invention than applying for a patent " a kind of saw delay reflection-type wireless senser with anti-collision ", The sensing electromagnetic echoes amplitude of its transponder is big, is advantageous to improve sensor performance.

Technical solution of the present invention also has following excellent in addition to all features with SAW delaying types wireless senser now Point：

1. sensor anti-collision is excellent.One 13 compatible code characters are such as used, its compatible code character degree is 8, sensor Anti-collision is 8.As long as being designed in conjunction with 13 initial delays, the anti-collision of sensor has met just more than 100 Overwhelming majority application.

Reader performance, and the compatible code character using Du Genggao, present invention sensing are such as improved using phase-detection mode Device anti-collision can nearly more than 1,000.

2. the inquiry ping obtained on sensing chip is extremely narrow, echo electric pulse is also narrow, improves the detection essence of sensing amount Degree.

3. the inquiry ping obtained on sensing chip is extremely narrow, the spacing of output transducer can also diminish, sensor core Chip size shortens, and sensor is smaller, and cost is also low.

4. the coding techniques of the technical program, belonging to spread spectrum application, there is the advantages of all spread spectrum technics：It is anti- Interference, actual transmission radio-frequency power are small.

【Brief description of the drawings】

Figure 1A surface acoustic wave wireless transducer telemetries principle is illustrated：Delayed reflex type；

The echo of Figure 1B delaying type wireless sensers；

The echo time domain photo of Fig. 1 C delaying type wireless sensers；

Fig. 2 SAW resonator type wireless sensings chip is illustrated；

Fig. 3 saw delay reflection-type wireless sensings chip is illustrated；

Fig. 4 single antenna SAW delay line type wireless sensings chip is illustrated；

Fig. 5 double antenna SAW delay line type wireless sensings chip is illustrated；

The SAW delayed reflex type sensing chips of Fig. 6 A Germany Ai Dikelai Merck diagnostic companies, anticollision number is only 5, Reflecting grating group is laid out using time-division series system；

The sensor echo of the SAW delayed reflex type sensing chips of Fig. 6 B Germany Ai Dikelai Merck diagnostic companies.

Fig. 7 is encoded to H0D seven digit pulse polarity coding SAW associated transducer signals；

The simulation of Fig. 8 A SAW associated transducers autocorrelation performance is illustrated with code H0357 inversion codes carrier wave；

The simulation of Fig. 8 B SAW associated transducers autocorrelation performance is illustrated with coding H0357 correlations interdigital transducer；

Fig. 8 C SAW associated transducer autocorrelation performance simulation drawings；

The simulation of Fig. 9 A SAW associated transducers cross correlation is illustrated with code H046D inverting carrier wave；

The simulation of Fig. 9 B SAW associated transducers cross correlation is illustrated with coding H0357 correlations interdigital transducer；

Fig. 9 C SAW associated transducer cross correlation simulation drawings；

The supporting reader transmitting terminal block diagrams of the invention of Figure 10

Figure 11 delay line type wireless sensing chip-in series time division mechanism output transducers group layout signal (double antenna)

Figure 12 delay line type wireless sensing chip parallel connection time division mechanism output transducers group layout signal (single antenna)

Figure 13 delay line type wireless sensing chip parallel connection time division mechanism output transducers group layout signal (double antenna)

Figure 14 embodiment of the present invention：Shown using code division with the SAW delay line type sensing chip of time division mechanism in parallel Anticipate (single antenna)

Figure 15 embodiment of the present invention：Illustrated using code division with the SAW delay line type sensing chip of time division mechanism in parallel (double antenna)

Figure 16 embodiment of the present invention：Illustrated using code division with the SAW delay line type sensing chip for time division mechanism of connecting (single antenna)

Figure 17 embodiment of the present invention：Illustrated using code division with the SAW delay line type sensing chip for time division mechanism of connecting (double antenna)

【Embodiment】

Premier Wen Jiabao proposes in August, 2009, Expedite the application " perceiving China ", the i.e. industry of " intelligent sensing net " Change.In this year, center starts implementation, and " made in China 2025 " and " internet+", this is the great deployment of China's economic development, is to carry High national power, realize the powerful support of " Chinese dream ".Intelligent sensing net, its basic characteristics are：Ubiquitous sensing node, at any time Environmental change is perceived simultaneously to be pooled to information centre's processing by Radio Link and inform user, can the sensor of Wireless Networking be intelligence The basis of energy Sensor Network.

Surface acoustic wave (SAW) wireless senser based on Principles of Radar developed in recent years, is not required to extraneous power supply, anti-interference Ability is strong, can in various adverse circumstances (such as high temperature, strong electromagnetic and nuclear radiation etc.) reliably working, be conventional IC sensings The supplement of device, the base components of Internet of Things will be turned into, played in the fields such as modern industry, agricultural, traffic and environmental protection Its unique effect.

Without loss of generality, we illustrate the specific embodiment of the invention by taking commonly used temperature sensor as an example.

First, surface acoustic wave sensor brief introduction

1.1 SAW device features

SAW device is the passive miniature electronic part made on piezoelectric chip, and it utilizes and is deposited on piezoelectric chip The metal thin film structure such as interdigital transducer and reflecting grating array, based on (inverse) piezo-electric effect, realize the energy of electromagnetic wave-surface acoustic wave Mutually conversion, produce, conversion and control surface acoustic wave, to complete the functions such as frequency stabilization, filtering, delay and sensing, in radar, logical It is used widely in the fields such as news, audio frequency and video, remote control, sensing.

The energy conversion of SAW device is not related to electron-hole process, and external electromagnetic radiation will not have an impact to it, institute It can be applied with SAW device in strong electromagnetic radiation environment.

The basic characteristics of SAW device are：

Radioresistance, high-low temperature resistant, strong environmental adaptability, can in harsh and unforgiving environments reliably working；

Device volume is small, in light weight, and reliability is high, is produced in batches using microelectric technique, uniformity is good；

Surface wave is propagated in wafer surface, is easily controlled its transmission performance, is realized signal transacting and sensing function.

Surface acoustic wave electromechanical transducing process does not have electric load to participate in, and does not have energy conversion threshold value, is passive device；

1.2 SAW sensor

SAW technologies also show the advantage of brilliance in terms of information sensing, and the operation principle of SAW sensor is：Device week The change of collarette border physical quantity, chemical quantity and biomass can cause the skew of SAW device electrical characteristic, by detecting these skews With regard to the parameters such as surrounding environment physical quantity, chemical quantity and biomass can be monitored, passed in individual identification (label), physics, chemistry, biology There to be very big application prospect in sensor system.

SAW sensor high sensitivity, stable performance and compatible with semiconductor technology, main feature has：

Surface wave is propagated in wafer surface, easily by external environmental interference, there is direct pick-up function；

Sonic transmissions surface loads sensitive membrane, easily its surface wave is implemented to transform, realizes chemical-biological Application in Sensing；

Interdigital transducer has frequency selectivity, the quasi- digitlization of output signal；

The sensor mechanism of SAW sensor mainly has two kinds：Only utilize the physical sensors of piezoelectric substrate autosensitization performance With the chemical biosensor of additional external sensitive membrane.Physical sensors key is sensitive structure design, and chemical-biological senses The key of device is selection and the growing method of sensitive membrane.

The application mode of SAW sensor can be divided into two major classes：Wired sensor and wireless senser.

SAW wired sensors refer to the passive element using SAW sensor as detection circuit, such as the feedback of oscillating circuit Delay line, frequency stabilization resonator etc..Due to SAW sensor, its performance changes under the influence of environment parameter, causes detection electricity Some electrical parameter on road changes therewith, and obtains ambient parameter value.This kind of SAW wired sensors, it is practical for many years.

SAW wireless sensers are One function elements, when extraneous specific radio signal encourages, can transmit wirelessly go back to institute Locate the sensing responsive information of environment parameter.SAW device essence is passive, i.e., extraneous need not provide power supply can work, according to Document report, SAW tag is compared with IC tag, and in same request signal power, operating distance wants big thirtyfold or so.And SAW wireless sensers can be in reliably working under harsh and unforgiving environments, therefore SAW wireless sensers in recent years paid attention to by pole.

1.3 SAW wireless sensers

As described above, SAW wireless sensers obtain being that there is other types sensor not possess for it the reason for attention wireless Telemetry function.

In one SAW device, electro-acoustic energy conversion is realized at least with an interdigital transducer.Interdigital transducer is One is deposited on piezoelectric substrate, by certain regular cross arrangement, the bonding jumper battle array membrane structure shaped like two hand finger cross-likes, There are two opposed polarities to conflux outer electrode, the ability with frequency selectivity and direct-connected antenna transmitting/receiving wireless electric wave.High frequency is pitched After finger transducer is directly connected to antenna, SAW chip can just receive inquiry resonance electromagnetic ripple, and beam back the electromagnetism for carrying heat transfer agent Echo, reach wireless sensing function.

SAW wireless sensor systems are that the backscattering radio frequency identification mode based on Principles of Radar works, and it is by three Divide and form：Reader, transponder and information processing (containing database).Transponder is exactly one only by SAW wireless sensings chip, small The component that type antenna and adaptation sensed environmental are formed with shell, it is the artificial reflectance target with steerable retroreflective echoing characteristics. Reader sends high frequency interrogation pulse, and transponder produces the electromagnetism for being modulated (frequency, phase or time delay) by sensitive parameter to be measured Echo impulse, laggard row information is received by reader and handled, obtains the change of parameter to be measured, completes once sensing detection in real time.

It is divided into two types again by transponder Cleaning Principle：Delaying type and mode of resonance.

Mode of resonance SAW sensor system, the SAW sensing elements in transponder are a SAW resonators (Fig. 2), and it is utilized The resonant frequency of SAW resonator can be affected by the external environment the characteristic to change, if it is humorous to measure the SAW at environment to be measured The change for device resonant frequency of shaking, you can deduce the change of environment parameter, realize wireless sensing function.

Delaying type sensor, SAW tapped delay cable architectures are employed, it is more much lower than electromagnetic wave using SAW spread speeds Feature, make backscattered echo than reader pumping signal delay (Initial Echo time delay) microsecond more than, avoid sharp The influence to effective information echo such as signal and the interference of environment low coverage is encouraged, compares the application environment for being adapted to have strong electromagnetic.

1.4 SAW delaying type wireless sensers

The echo producing method of SAW delaying type wireless sensers has two kinds：Using interdigital transducer delay line type and adopt With the delayed reflex type of sound reflector.

SAW delayed reflex type sensor system principle of work is as shown in Figure 1.Made on piezoelectric chip in transponder There are input interdigital transducer and acoustic wave reflector (also referred to as reflecting grating group), acoustic wave reflector is by mutual disjunct multiple reflecting gratings Composition, as the reflectance target with characteristic value.When the radio-frequency queries pulse that reader is sent is received by the antenna of transponder Afterwards, the input interdigital transducer being joined directly together with antenna is converted to the electric pulse received in the sound table propagated on piezoelectric substrate Face wave impulse, and sound echo impulse string is thus reflected to form by acoustic wave reflector.Because on substrate acoustic wave reflector state with it is outer Boundary's environmental stress is relevant, then will carry heat transfer agent by the sound echo impulse string that reflector reflects.Sound echo impulse string is again by defeated Enter interdigital transducer and be converted to radio-frequency electromagnetic train of pulse, and gone back from antenna transmitting.Reader receives electromagnetic echoes train of pulse Afterwards, amplify and decode, entering computer database, reach sensing purpose.Fig. 3 is that delayed reflex type senses transponder chips signal Figure.

It is with short output fork that is multiple and connecing that delay line type sensor (Fig. 4, Fig. 5) does not exist together with delayed reflex type sensor Finger transducer replaces reflecting grating group, the source as echo electromagnetic pulse：It is defeated in the surface acoustic wave ping that chip surface transmits Go out transducer and be transformed to electromagnetic pulse, the transmitting antenna through being joined returns to reader.Obviously, to the senser element of same design, The delay of echo impulse string is more half as large than reflection-type, but its amplitude is big many.This sensor construction, it is anti-with foregoing SAW Emitting wireless senser only has an antenna difference, can use the two kinds of designs of single antenna and double antenna.(figure in single antenna construction 4), the output transducer as echo source is connected to request signal input transducer, common antenna.And double-antenna structure (Fig. 5), both separate, and are each connected with antenna, and transmitting-receiving interference is small.

Delaying type sensor is to carry out heat transfer agent survey using change of the echo-signal in the time delay or phase of time shaft Amount, when external environment parameter changes, the time delay (phase) between echo will be influenceed, detect the time delay, so that it may feel Know the change of environment parameter.The reflecting grating (or output interdigital transducer) of SAW wireless sensers is generally three, to improve sensing Measure accuracy of detection.

For physical sensor, appropriate substrate sensitive structure is designed, makes echo time delay parameter by environmental stress to be measured Influence stable and very big.And for chemical-biological type sensor, it is quick in the deposit one of piezoelectric substrate sound pulse transit path position Feel film, the sensitiveness by sensitive membrane to chemical-biological amount to be measured, sensitive film character is changed, and then influence sound wave pulse Transmission performance, detectable change occurs for time delay between causing echo impulse string, you can reaches sensing purpose.

The anti-collision of 1.5 SAW delaying type wireless sensers

Anticollision refers in the detectable range of reader, it is allowed to which multiple sensors exist simultaneously, without influenceing to pass Feel the reception of information.Sensor not specially designed at present, when its echo waveform is all the simple repetition of request signal pulse Domain arranges, after the echoes of different sensors is overlapping, it is difficult to distinguish, i.e., sensor does not have anti-collision capacity.

SAW sensor anticollision technology mainly has three kinds now：Chip design, software algorithm and individual isolation.Individual every From being exactly to reduce reader effective range, ensure that reader receives only a sensor echo；Software algorithm is exactly using each The difference of sensor echo-signal, each sensor information is isolated by algorithm, have many discussions, practicality is indefinite.

Chip design method has essential anticollision feature, designs the Initial Echo time delay difference of different sensors and makes Its echo sequence is spaced apart, referred to as time division way, to obtain anti-collision.Such as German Ai Dikelai Merck diagnosis public affairs The RITHERM wireless and passive SAW temperature-sensing systems that department's (LDIC) overhead transmission line temperature monitors in real time, anti-collision are Five, as shown in Figure 6 A and 6 B.

From the above mentioned, the anti-collision of SAW delaying types wireless senser is not met by functional need at present.

2nd, the SAW delay line type wireless sensers of chip-scale anti-collision are realized using code division mechanism

This section will be based on patent of invention：Acoustic surface wave passive radio frequency identification tag and sensor (ZL2010101761425), Illustrate the operation principle that chip-scale anticollision SAW delay line type wireless sensers are realized using code division mechanism.

The input interdigital transducer of 2.1 SAW delay line type transponders

The input transducer of transponder chips receives radio-frequency queries pulse excitation, obtains inquiring surface acoustic wave arteries and veins on chip Punching, inputted as heat transfer agent driving source.

The input interdigital transducer of SAW delay line type wireless sensers now is mostly the cycle uniform transducing such as conventional Device, encouraged using single frequency carrier burst pulse, obtained inquiry ping is the convolution of carrier pulse and input transducer, is width Slightly larger than the approximate rectangular pulse of transducer time domain length.Ping is advanced along sound channel, and its characteristic is modulated by sensing amount, finally quilt Again after acoustic-electric conversion, the electromagnetic echoes train of pulse of formation, its width will be expanded output interdigital transducer group again.

Many document reports in recent years, transducer designs are inputted by changing, the potentiality of SAW device can be played.Such as：

United States Patent (USP) US005469170 and United States Patent (USP) US006788204 are proposed：Using Dispersion Transducer as SAW The input transducing unit of label chip, and chirped modulation carrier pulse is received, extremely narrow inquiry sound can be formed in chip Pulse.Because inquiry ping is narrow, be advantageous to electromagnetic echoes accuracy of detection.

2.2 SAW associated transducers

Interdigital transducer realizes the distinctive electro-mechanical of SAW device-electric passive energy transformation mechanism in SAW device, by right The design of interdigital transducer parameter, the complicated Electric signal processing function such as real-time implementation correlation, convolution can be made it have, is needing height In the application that speed is handled in real time, there is not replaceable application.The wide variety of SAW phases in radar and Detection of Weak Signals Device is closed, just make use of the modulation pulse choice of coding interdigital transducer, the hereinafter referred to as interdigital transducer with this class feature is Associated transducer.

W.Buff in 1998 etc. has reported OCC technologies：Using being encoded to S1 (t) associated transducer as surface acoustic wave mark Label input transducing unit, modulates carrier wave source forcing with its time inversion codes S1 (- t), extremely narrow inquiry sound is obtained in chip Pulse.

At present, the coded system that SAW associated transducers use also has two kinds：Pulse polarity encodes and orthogonal frequency coding. For simple meter, this paper only discusses the characteristic of associated transducer with regard to former mode.

2.2.1 pulse polarity coding SAW associated transducers

Fig. 7 is that seven digit pulse polarity encode SAW interdigital transducer structures, and transducer is the different sub- transducer of multiple polarity Combination, by sub- transducer electrode conflux it is different realize polar modulation, it is to encode that it, which arranges sequence, sub- transducer time domain length etc. In the chip lengths of coding electric pulse.In Fig. 7, every sub- transducer length is 4 wavelength, and transducer is encoded (with hexadecimal Represent) it is seven bit code H0D=(0001101).

2.2.2 correlation of the SAW associated transducers to input coding pulse

After a coding electric pulse is inputted to SAW associated transducers, export and rolled up for input coding pulse and coded transducer The acoustical signal of generation is accumulated, now the parameter of input pulse will match with the parameter of associated transducer：Carrier frequency corresponds to transducing In the device cycle, coding digit is identical with sub- transducer number, and pulse chip lengths correspond to sub- transducer time domain length.Work as input coding When the coding of electric pulse is the time domain inversion of this SAW associated transducer coding, it exports convolution signal and is referred to as autocorrelation signal, such as Shown in Fig. 8 A, Fig. 8 B and Fig. 8 C, it has very big amplitude central peak, and peak width is about input pulse chip lengths, and secondary lobe is smaller, Its time domain length is about twice of input pulse.In input coding electric pulse when being encoded to other situations, it exports convolution letter Be known as cross-correlated signal, as shown in figure 9, for amplitude scintillation but without obvious main peak and time domain length it is also about defeated Enter the stray wave of twice of pulse.

If we choose one group of code, the cross correlation between them is fine, that is to say, that：Compiled using one of code The SAW associated transducers of code, such as input an interrogation pulse for being encoded to its time reversal, then it is caused after its excitation Auto-correlation response is an extremely narrow significantly ping, and as heat transfer agent driving source, thus obtained transponder senses back Ripple is obvious；And by after the interrogation pulse excitation of other yards of codings, caused cross-correlated signal, the simply less stray wave of amplitude, Thus obtained transponder echo is minimum.We are referred to as this group code and form a compatible code character, and each member is referred to as compatible code, Its number is called the degree of compatible code character.Thus, code character member is compiled using the SAW associated transducers of compatible code character member coding The input electric pulse of code has that good code is selective, therefore referred to as code division mechanism.

Fig. 8 A, Fig. 8 B and the correlation properties that Fig. 8 C are SAW associated transducers are simulated, and represent thirteen bits H0357= (0001101010111) auto-correlation output characteristics, its auto-correlation peak height is about its code length 13, and autocorrelation sidelobe value maximum is only For 4, autocorrelation performance is good.Fig. 9 A, Fig. 9 B and Fig. 9 C represent the code and code H046D=(0010001101101) cross-correlation Output characteristics, its cross-correlation extreme value are also 4, only the 30% of peak value.It is believed that code H0357 and code H046D composition code lengths 13 One compatible code character.

2.3 compatible code characters

SAW associated transducers, which encode, belongs to the pseudo noise code of spread spectrum technic, but now puppet of wide variety of cycle with The aperiodic code sequence such as machine code sequence and Barker code, does not account for intersymbol cross correlation.For with anti-collision, Wo Menyao Ask system to use one group determines code length spreading code, is the set that need to meet following requirements：

A. the autocorrelation performance side lobe levels of each member are as far as possible small；

B. the cross correlation value between member is as far as possible small；

C. number of members is tried one's best more；

D. each member is approximately balanced code；

Meet one group of code of above-mentioned requirements, a compatible code character referred to as with regulation performance.The performance of compatible code character by Following parameters determine：Code length n, the maximum permissible value ph of each code equilibrium valve, the maximum appearance of each code autocorrelation performance secondary lobe maximum Perhaps value PSL, the maximum permissible value FXG of intersymbol cross correlation maximum, and represent compatible code character with (code length, ph, PSL, FXG) Class.Such as the compatible code character of foregoing 13 bit code can be labeled as (13, Isosorbide-5-Nitrae, 4).

Compatible code character membership is referred to as it and spends m, i.e., during using the compatible code character as system spread-spectrum code, after some time it is possible to reach The number of essential anticollision, distinguishable inhomogeneity sensor.

Computer search method can be used, finds compatible code character.After practical operation, find：Requirement to compatible code character is got over Height, more it is difficult to obtain available compatible code character；Code length is longer, and the degree of compatible code character is possible to increase, but not same with code length Walk relation with increase.

The compatible code character for being characterized as (13,5,4,5) is searched, its maximal degree m is 8.

2.4 realize anti-collision using code division mechanism

Using input transducing unit of the SAW associated transducers as SAW wireless senser transponder chips, and reader The electric interrogation pulse (referred to as matching interrogation pulse) modulated using the time domain inversion code of the compatible code is inquired to this transponder. Due to the correlation properties of same compatible code character, this transponder only produces extremely narrow inquiry sound arteries and veins in chip by its matching inquiry electric pulse Peak is rushed, and other non-matching inquiry electric pulses are not obvious responsed to.Had using the chip of same compatible code character coding good Good interrogation pulse selectivity, that is, have code selective, thus achieve chip-scale anti-collision.

If we are preferred one group of compatible code, spend for m, and designed and produced m kind sensing chips, then we are prevented Collision performance is the m SAW wireless sensers using code division mechanism.

The requirement of 2.5 readers

As a result of transducing head of the associated transducer as sensor chip, the interrogation pulse that reader is sent, Must be coded pulse, and can transition coding match transponder.So the transmitting terminal of reader need to increase code generation and modulation Part, such as Figure 10.

3rd, the SAW delay line type wireless sensers of chip-scale anti-collision are realized using time division mechanism

Chip-scale anti-collision is realized using time division mechanism, existing practical application, such as foregoing German Ai Di Wayne Kramers The RITHERM wireless and passive SAW temperature-sensing systems that gram diagnostic companies (LDIC) overhead transmission line temperature monitors in real time.Fig. 6 A are Its chip is illustrated, and employs delayed reflex type structure, reflecting grating group on different chips, and distance input interdigital transducer distance (rises Beginning delay distance) it is different, anticollision number is only 5 (Fig. 6 A and Fig. 6 B).

3.1 antenna

It has been observed that the antenna of delay line type sensing chip can have two ways：Transmit-receive sharing single antenna and transmitting-receiving separate Double antenna form.

Transmit-receive sharing single antenna form, input interdigital transducer and the bus electrode of output interdigital transducer group are connected in one Rise, as shown in Figure 4.Due to common antenna, in addition to main electromagnetic echoes string caused by output transducer group, because output transducer is anti- Be emitted back towards come and be transfused to transducer reconvert secondary electromagnetic echoes string can also be attached to above-mentioned main electromagnetic echoes string after.It is if defeated It is longer to go out transducer group, main echo rear portion can significantly interfere with the anterior superposition of second trip echo, formation.Certainly, second trip echo amplitude More small than main echo, disturbing effect influences little.

Separate antenna double antenna form is received and dispatched, interdigital transducer is inputted and the bus electrode of output interdigital transducer group does not connect Together, an antenna is each connect, as shown in Figure 5.Which overcome the deficiency of above-mentioned duplexer form, but cost is paid Cost.

3.2 chip layout

In addition to interdigital transducer is inputted, difference is laid out by output transducer group on chip, there can be two ways：Series connection and Parallel connection, referred to as connect time division mechanism and time division mechanism in parallel.

Figure 11 illustrates for series connection time division mechanism, i.e., the output transducer group on different chips is as entirety, along sound channel direction It is arranged in order.So, the echo of different chips, when obtaining at the same time, and show in groups.If each chip is with initial delay time Short long mark 1,2,3,..., n, market transducer table is a, b, c on chip.It is 1a, 1b, 1c successively that then echo, which is shown,；2a, 2b, 2c；…；Na, nb, nc.

Figure 11 is single antenna construction, and output transducer group layout is identical during double-antenna structure.

Figure 12, Figure 13 are time division mechanism in parallel, i.e., the output transducer group on different chips is to intersect to arrange along sound channel direction Row, thus, the echo of different chips, when obtaining at the same time, and intersect display.

In Figure 12, four row from top to bottom, represent with the time division mechanism chip of different Initial Echo time delay differentiations, With 1,2,3 ..., n represents different chips；As seen from the figure, the anti-collision n=9 of this example, during practical application, can reach several Ten, or even 100.

The output transducer group of each chip is made up of three output transducers, is represented with a, b, c, is arranged sequentially chip In surface wave sound channel.

Figure 12 most figure below, represent that the echo impulse when all transponders are received simultaneously is shown, respectively should clearly identify Answer returning for device and be followed successively by 1a, 2a, 3a ..., na；1b, 2b, 3b ..., nb；1c, 2c, 3c ..., nc.

Figure 12 is single antenna construction, and Figure 13 is double-antenna structure, and its output transducer layout is identical.

Pay attention to, most figure below is different from the content of each subgraph thereon in Figure 11, Figure 12, and Figure 13, the abscissa of most figure below It is echo time-domain representation, and each subgraph represents that both only have corresponding relation for the geometric position of chip output transducer group thereon.

3.3 output interdigital transducer groups design

The Cleaning Principle of delay line type sensor is：During biography sensitivity changes to be measured, surface acoustic wave echo separation also becomes Change, detect its change, just obtain heat transfer agent to be measured.

Input the distance of transducer and first output transducer, be designated as L0, represent the chip Initial Echo postpone away from From.To delay line type structure, actual Initial Echo time delay (setting Vs as surface acoustic wave speed) is：

T0=L0/Vs

Generally higher than 1us, to ensure reader antijamming capability.It is obvious, than delayed reflex type sensing chip delay when Prolong half small, that is to say, that to reach the same anti-jamming effectiveness of delayed reflex type cake core, L0 will lengthen one times so that Chip length increase is obvious.

In theory, the echo of an output transducer, it is possible to obtain heat transfer agent.But due to：

The relative motion state of transponder and reader, cause the error of Initial Echo time delay；

The temperature characterisitic of chip, T0 change can be caused；

Chip fabrication technique tolerance, cause different batches chip variant,

So as sensing chip, at least two output interdigital transducers form an output transducer group, Initial Echo Away from respectively as transponder differentiation and heat transfer agent detection data when between time delay and echo.If L1 is between two output transducers Away from, then between echo when away from for：

T1=L1/Vs

Under first approximation, it is believed that T1 and the wired sexual intercourse of information content s to be sensed, linear coefficient alpha：

T1 (s)=T1 (s0) * { 1+alpha* [s-s0] }

In formula, T1 (s0) is echo time when information reference value to be measured is s0 away from and T1 (s) is in the value of information to be measured For s when, the measured echo time away from.When transponder is in s0 state calibrations, alpha and T1 (s0) value are can obtain, thus may be used Obtain heat transfer agent s to be measured：

S=[T1 (s)-T1 (s0)]/[alpha*T1 (s0)]+s0

From above formula, output transducer spacing L1 is longer, and the precision of heat transfer agent measurement is higher.So use parallel connection side Formula is laid out output transducer group, and the precision of heat transfer agent measurement is higher.

Recently when positive development reader is used between phase-detection echo away from technology, heat transfer agent can be made to obtain precision significantly Improve.But in only two output transducers, phase reference problem is faced, easily produces phase test error more than 360 ° Mistake.Thus, practical delaying type sensor all forms output transducer group using three output transducers now：It is defeated using three Go out between transducer when away from comparing, determine phase test true value.Related description refers to the " High that L.Reindl etc. is delivered Precision Wireless Measurement of Temperature by Using Surface Acoustic Waves Sensors"(Sensor 2003,Numberg,May,2003)。

Certainly, in design, it should ensure that transponder is measured in the range of examination in nominal sensing, the echo of all chips can expire In meaning resolution, such as Figure 11, Figure 12 and Figure 13 shown in bottom.

Anti-collision energy under 3.4 time division mechanisms

By foregoing, under time division mechanism, chip anti-collision function is equal in certain period of time, the echo impulse that can be differentiated Radix mesh during initial delay, i.e., in sequential area when radix mesh n, referred to as sequential capacity.

Because chip length is limited, it is relevant with package dimension, production technology and cost performance.

It is determined that chip length when, reflecting grating number is more, and effective sequential area is shorter.

Reader performance plays a major role to anti-collision.

4th, it is of the invention：The SAW delay line type wireless sensers of chip-scale anti-collision are realized using code division time division mechanism

The present invention essence be：The chip of time division mechanism described in prosthomere will be used, before it inputs uniform interdigital transducer use State associated transducer replacement, you can obtain realizing that the saw delay reflection-type of anti-collision passes using code division time division mechanism Sense chip.

Using code division and the technical scheme of time division mechanism in parallel as shown in Figure 14 and Figure 15, respectively single antenna and double antenna Structure；And use code division and the technical scheme for time division mechanism of connecting as shown in Figure 16 and Figure 17, respectively single antenna and double antenna Structure.

4.1 chip

Without loss of generality, the saw delay that anti-collision is realized using code division time division mechanism is illustrated with Figure 14 Reflection-type sensing chip.Chip identification is Xx, and capital X represents chip coding specification, and lowercase x represents time-division sequence number 1, 2 ..., n.

Figure 14 chip is divided into three classes：A, B and C, the interdigital transducer of all kinds of chips is the related transducing of same code length Device, it is encoded to the compatible code for belonging to same compatible code character (10,0,3,4)；A：H16C=(0101101100), B:H1CA= And C (0111001010):H11D=(0100011101).

Figure 14 gives three classes five chips：A1, B1 and C1 are inhomogeneity but initial delay distance L0 (being herein minimum) Identical chip；C1, C2 and Cn are same class but the different chips of initial delay distance L0.

If the coding of the request signal that reader is sent such as Figure 14 lower lefts (compile by C classes chip coding H11D time domain inversion Code) carrier pulse, after being received by transponder antenna, feed arrives chip associated transducer, related ping is produced, such as Figure 14 tops Shown in middle row：To matching chip (C classes chip in Figure 14), typical auto-correlation ping will be obtained, amplitude is big, and main peak is narrow (only One symbol width), and secondary lobe is low (1/3 less than)；And to non-matching chip (A, B class chip in Figure 14), it can only obtain amplitude Spuious cross-correlation ping less than 40%.

The ping, is the source of heat transfer agent electromagnetic echoes, and its characteristic significantly affects echoing characteristics.Due to using related Transducer and matching interrogation pulse, the ping amplitude of generation is big, and main peak is narrow, is thus output the echo electricity of transducer group formation Magnetic field impulse, it may have amplitude is big, main peak is narrow, and good basis is laid to improve the sequential capacity of time division mechanism.

When all transponders is are detected in Figure 14 bottom rights simultaneously, the electromagnetic echoes that reader obtains are illustrated.Below Figure 14 when Domain characteristic, it is followed successively by C1a, C2a ..., Cna；C1b, C2b ..., Cnb；C1d, C2d ..., Cnd echo, wherein exporting transducing Device is labeled as a, b, d.And the echo of A, B class chip is submerged in background clutter.This shows to a specific interrogation signal, only There is matched transponder to have sensor echo response, and the sensor of the transponder of different Initial Echo lag characteristics returns Ripple is also clearly separated, that is, realizes code division time-division anti-collision.

As shown in Figure 14, the degree for the compatible code character (10,0,3,4) that this example uses is 3, and the number per class chip is up to 9 (sequential capacity), therefore the anti-collision of this example is 3*9=27.

It is above-mentioned that the present invention is illustrated with code division and time-division chip in parallel (Figure 14, Figure 15), only show the preferred scheme of the present invention One of.The chip (Figure 16, Figure 17) and another embodiment of the invention that code division and series connection time-division combine, not repeat specification .

4.2 advantages of the present invention

Technical solution of the present invention also has following excellent in addition to all features with SAW delaying types wireless senser now Point：

1. sensor anti-collision is excellent.One 13 compatible code characters are such as used, its compatible code character degree is 8, sensor Anti-collision is 8.As long as being designed in conjunction with 13 initial delays, the anti-collision of sensor has met just more than 100 Overwhelming majority application.

Reader performance, and the compatible code character using Du Genggao, present invention sensing are such as improved using phase-detection mode Device anti-collision can nearly more than 1,000.

2. the inquiry ping obtained on sensing chip is extremely narrow, echo electric pulse is also narrow, improves the detection essence of sensing amount Degree.

3. the inquiry ping obtained on sensing chip is extremely narrow, the spacing of output transducer can also diminish, sensor core Chip size shortens, and sensor is smaller, and cost is also low.

4. the coding techniques of the technical program, belonging to spread spectrum application, there is the advantages of all spread spectrum technics：It is anti- Interference, actual transmission radio-frequency power are small.

Though illustrating the present invention above with temperature sensor, the present invention can be used for the wireless anti-collision of other environment sensitive amounts Hit sensor application.

Although the present invention is described by embodiment, embodiment is not used for limiting the present invention.Art technology Personnel can make various modifications and improvement in the scope of the spirit of the present invention, but equally protection scope of the present invention it It is interior.What therefore protection scope of the present invention should be defined by claims hereof protection domain is defined.

Claims (1)

1. a kind of SAW delay line type wireless sensor system with anti-collision, by transponder, reader and after Platform processing unit forms, it is characterised in that：

Surface acoustic wave sensing chip is used in the transponder；

The input interdigital transducer of the surface acoustic wave sensing chip is coding interdigital transducer；

At least two same frequency output interdigital transducers arranged along sound channel of the surface acoustic wave sensing chip, the output interdigital Transducer is the conventional uniform interdigital transducer with frequency with input interdigital transducer；

The input interdigital transducer of surface acoustic wave sensing chip in the transponder, it is encoded to compatible code；

Similar transponder is formed by multiple transponders of the surface acoustic wave sensing chip using same compatible code coding；

Initial delay distance, i.e. the first of surface acoustic wave sensing chip output interdigital transducer input interdigital transducer with it Distance, different surface acoustic wave sensing chips are different from each other in similar transponder；

The spacing of each output interdigital transducer in similar transponder on different surface acoustic wave sensing chips is consistent；

When designing above-mentioned each output interdigital transducer spacing, it should make to measure in the range of examination in nominal sensing, similar transponder is same After caused electromagnetic echoes superposition, all echo peaks should be able to all be differentiated by reader, know its source and heat transfer agent；

The reader has compatible code generating means.