CN103020675A - Ultrahigh-frequency RFID (radio frequency identification device) reading and writing module based on self-adaptive tuning technology of antenna - Google Patents
Ultrahigh-frequency RFID (radio frequency identification device) reading and writing module based on self-adaptive tuning technology of antenna Download PDFInfo
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Abstract
The invention relates to an RFID (radio frequency identification device) reading and writing module, and particularly relates to an ultrahigh-frequency RFID reading and writing module based on a self-adaptive tuning technology of an antenna. The ultrahigh-frequency RFID reading and writing module comprises a central processor, a self-adaptive impedance tuning network, a power management circuit, a connector, a radio frequency connector, a crystal oscillator I and a crystal oscillator II, wherein the crystal oscillator I and the connector are connected with the central processor; the central processor is connected with the self-adaptive impedance tuning network; the self-adaptive impedance tuning network is connected with the radio frequency connector; the power management circuit is connected with the connector, the central processor, the crystal oscillator II and the self-adaptive impedance tuning network; and the radio frequency connector is connected with an external antenna. The ultrahigh-frequency RFID reading and writing module has the beneficial effects of solving the problem that a reflected wave of the antenna is deteriorated because of external factors so as to cause degeneration of receiving sensitivity, having stable radio frequency characteristics when the cost is reduced, and being stronger in multi-label processing capacity, higher in counting efficiency and more suitable for application of a handheld reader-writer.
Description
Technical field
[0001] the present invention relates to the RFID module for reading and writing, relate in particular to the ultrahigh frequency RFID module for reading and writing based on the antenna self-adaptive tunable technology.
Background technology
The ultrahigh frequency RFID module for reading and writing partly is comprised of transmitter, receiver, circulator (or coupling mechanism), wave detector and CPU etc. usually as the core component in the total solution hardware composition of RFID.Because ultrahigh frequency radio frequency identification (RFID) reader is a transmit-receive cofrequency, equipment simultaneously, TDD, fdd mode unlike the mobile communication mobile phone radio-frequency front-end, the RFID read-write equipment is a kind of self-interference system: except the emissive power and sensitivity index of hardware self, because the size of the emissive power reflection wave that the standing wave of antenna end causes also directly affects the distance of reading/writing distance, and the undesired signal energy that enters into receiver is stronger, and the sensitivity of receiver is poorer.This is because the reflected energy of transmitter power when running into antenna mismatch directly has been fed into receiver end as a kind of harmful interfering energy, has caused the degeneration of receiver sensitivity, and then has reduced the actual range of read-write equipment identification label.Shown in Figure 1, be the radio frequency operation schematic diagram of traditional ultrahigh frequency RFID module for reading and writing, show the relation between module for reading and writing front end emission power and antenna standing wave and receive-transmit isolation, several persons of receiving sensitivity among the figure.As can be seen from the figure, emissive power 30dB is owing to exist (the corresponding standing-wave ratio (SWR) 1.3 of the return loss of 17dB) of antenna standing wave, have the reflection wave of 13dB to be fed into receiver by coupling mechanism, transmitted wave also enters into receiver from the also feed-in part energy of isolation end of coupling mechanism in addition; The two stack has formed the undesired signal to receiver.
Therefore, want to promote the performance of module for reading and writing, be down to the undesired signal energy that is fed into receiver minimum.In the hand ultra-high frequency rfid interrogator, antenna size is smaller, and What is more, built-in antenna is in casing, this moment, human body, components and parts on every side, structural member be as the influence factor of antenna, can have influence on to some extent the actual antennas standing-wave ratio (SWR), and reading/writing distance is also influenced to become unstable; When fixed type reader-writer faces many labels and makes an inventory, often label can be nearer apart from antenna, and when label itself was exactly anti-metal tag, the echo of read-write antenna also may be owing to the impact that is subject to label self physical characteristics worsens, and causing the receiving sensitivity variation, the skip probability increases.
Generally speaking, antenna echo can badly influence the serviceability of read write line self.
Summary of the invention
The present invention overcomes above-mentioned weak point, purpose is on the basis of traditional ultrahigh frequency RFID module for reading and writing RF front end structure, a kind of deficiency that can overcome the anti-antenna mismatch ability of traditional ultrahigh frequency module for reading and writing radio architectures is provided, and can effectively weakens the ultrahigh frequency RFID module for reading and writing of the antenna self-adaptive tunable technology of the return loss energy that antenna mismatch causes.
The present invention achieves the above object by the following technical programs: the ultrahigh frequency RFID module for reading and writing based on the antenna self-adaptive tunable technology comprises: central processing unit, the impedance-tumed network of self-adaptation, electric power management circuit, connector, radio-frequency joint, crystal oscillator I, crystal oscillator II; Described crystal oscillator I, connector are connected with central processing unit, the impedance-tumed network connection of central processing unit and self-adaptation, the impedance-tumed network of self-adaptation is connected with radio-frequency joint, described electric power management circuit and connector, central processing unit, crystal oscillator II, the impedance-tumed network connection of self-adaptation, radio-frequency joint links to each other with exterior antenna.
As preferably, the impedance-tumed network of described self-adaptation comprises: rf chip, power amplifier, coupling mechanism, wave detector, antenna tuning matching network; Described rf chip is connected with central processing unit, crystal oscillator II, power amplifier, power amplifier is connected with coupling mechanism, coupling mechanism is connected with antenna tuning matching network, wave detector, wave detector is connected with central processing unit, the antenna tuning matching network is connected with radio-frequency joint, central processing unit, and electric power management circuit provides power supply for rf chip, power amplifier, antenna tuning matching network.
As preferably, central processing unit, rf chip, power amplifier, coupling mechanism, wave detector, antenna tuning matching network form sealing and detect in real time feedback circuit.
As preferably, also include heat radiator based on the ultrahigh frequency RFID module for reading and writing of antenna self-adaptive tunable technology.
As preferably, the topological network of antenna tuning matching network can be series, parallel even multi-stage cascade, and network progression is more, and the tunable scope of the impedance-tumed network of self-adaptation is just wider.
As preferably, the communication interface mode of the impedance-tumed network of self-adaptation and central processing unit is SPI or I
2C.
As preferably, radio-frequency joint can expand to by radio-frequency (RF) switch a plurality of.
As preferably, described electric power management circuit provides 3.3 ~ 5V supply voltage.
Beneficial effect of the present invention is: thereby 1, the present invention has overcome traditional module for reading and writing because the antenna-reflected ripple that causes of extraneous factor worsens the problem that receiving sensitivity is degenerated that has influence on; 2, this module for reading and writing is in the intensive scene that reads of many labels, overcome because the impact that the physical characteristics of magnanimity label self causes the read-write antenna, and its radiofrequency characteristics is comparatively stable, and many tag processes ability is stronger, and the efficient of making an inventory is higher; 3, no matter the module for reading and writing with the self-adapting tuning network is reliably reading distance, and all there is larger improvement make an inventory time and many tag processes ability aspect of many labels than the module for reading and writing of conventional architectures; 4, the present invention realizes real-time testing calibration by communication modes such as SPI or I2C, and cost is relatively low; 5, this module for reading and writing is fit to the application of hand-held read-write more.
Description of drawings
Fig. 1 is the radio frequency operation schematic diagram of traditional ultrahigh frequency RFID module for reading and writing;
Fig. 2 is based on the structural representation of the ultrahigh frequency RFID module for reading and writing of antenna self-adaptive tunable technology;
Fig. 3 is the circuit theory diagrams of adaptive antenna resonance matching network;
Fig. 4 is the locus of impedance schematic diagram of the described antenna standing wave of the specific embodiment of the invention on the smith circle diagram.
Embodiment
The present invention is described further below in conjunction with specific embodiment, but protection scope of the present invention is not limited in this:
Embodiment 1: as shown in Figure 2, ultrahigh frequency RFID module for reading and writing based on the antenna self-adaptive tunable technology comprises: central processing unit, rf chip, power amplifier, coupling mechanism, wave detector, antenna tuning matching network, electric power management circuit, connector, radio-frequency joint, crystal oscillator I, crystal oscillator II; Described crystal oscillator I, connector, rf chip is connected with central processing unit, rf chip and crystal oscillator II, power amplifier connects, power amplifier is connected with coupling mechanism, coupling mechanism and antenna tuning matching network, wave detector connects, coupling mechanism also is connected with rf chip, wave detector is connected with central processing unit, antenna tuning matching network and radio-frequency joint, central processing unit connects, radio-frequency joint links to each other with exterior antenna, and electric power management circuit is connector, central processing unit, rf chip, power amplifier, the antenna tuning matching network, the crystal oscillator II provides power supply; The output power of power amplifier finally arrives exterior antenna through coupling mechanism and via the antenna tuning matching network during work of ultrahigh frequency RFID module for reading and writing, because the outwardness of antenna standing wave, the portion of energy of transmitted power is because mismatch feeds back to the coupled end of coupling mechanism with the form of reflection wave, and radiofrequency signal is transformed to d. c. voltage signal and delivers to central processing unit and carry out the A/D sampling processing by wave detector, when standing-wave ratio (SWR) surpasses the standing wave thresholding, central processing unit is by the adjustable element in the SPI interface control antenna resonance matching network, revise standing-wave ratio (SWR), until suitable threshold value.
As can be seen from Figure 2, also include heat radiator based on the ultrahigh frequency RFID module for reading and writing of antenna self-adaptive tunable technology, electromagnetic shielding action and thermolysis have been brought into play in the installation of heat radiator, have played safety protection function.
The principle of work of each critical piece is as follows:
Central processing unit realized by a ARM7 chip, and ARM7 has also realized the buffer memory application except the carrier of bearing whole module firmware: central processing unit is externally realized the input/output communication of USB, serial communication and relevant I/O mouth; The internally work order of control rf chip and to the closed-loop control of the impedance-tumed network of self-adaptation.The impedance-tumed network of described self-adaptation is comprised of rf chip, power amplifier, coupling mechanism, wave detector, antenna tuning matching network, forms sealing with central processing unit and detects in real time feedback circuit;
Rf chip is integrated frequency synthesizer, frequency mixer, drive and put and LNA; The effect of power amplifier is the further linear effective decipherment distance that amplifies in order to the read write line that extends of emission signal; The coupling mechanism Main Function is for realizing the isolation of receiving-transmitting chain, simultaneously the energy of forward emitted link detected, and change radiofrequency signal into voltage signal by wave detector and send to central processing unit, central processing unit carries out the A/D sampling processing, thereby realizes the real-time detection of forward emitted link power, backward receiver power;
Crystal oscillator in the present embodiment is divided into crystal oscillator I, crystal oscillator II, and the crystal oscillator I is a passive crystal oscillator, is connected with central processing unit, for central processing unit provides clock reference; The crystal oscillator II is active TCXO, is connected with rf chip, for rf chip provides accurately clock signal;
Electric power management circuit is realized the needed various voltages of each active circuit, and electric power management circuit can also be connected with the external control device simultaneously, accepts the dormant state that external signal controls to realize module for reading and writing, enters low-power consumption mode.
Fig. 3 is the circuit theory diagrams of the impedance-tumed network of self-adaptation, and the antenna tuning matching network adopts a string topological mode in the lump among the figure, adjustable element is controlled in real time by central processing unit by spi bus; U923, U924 are the adjustable element in the antenna tuning matching network, and U303 is wave detector, and U900 is coupling mechanism, and U901 is power amplifier, and J301 is radio-frequency joint, and radio-frequency joint adopts the MMCX radio frequency connector; Wherein, SCL is clock signal, Low level effective, when SCL is in low level, central processing unit is by adjusting the value of adjustable element U923, U924, change the matching status between coupling mechanism and the exterior antenna, and by wave detector the size of reflection wave is carried out closed loop and detect, until standing-wave ratio (SWR) reaches the optimum gate limit value under a certain frequency.
Fig. 4 is the smith circle diagram that simulates by circuit modeling shown in Figure 3, and the solid black line is illustrated in initial resistance value corresponding to standing-wave ratio (SWR) in the 800-1000MHZ band limits, and the almost fan zone that is covered by round dot is the virtual impedance scope of self-adapting tuning network.M2 is desirable resistance value, and this moment, standing-wave ratio (SWR) was similar to 1, and resistance value is 50 ohm, and in side circuit, antenna echo can be enhanced but can not eliminate.Resistance value when m1 is 915MHZ, this moment, resistance value was 40 ohm, and complex impedance is 36.858+j10.762 ohm, and return loss corresponding to standing-wave ratio (SWR) is approximately-14dB, and with the return loss 17dB comparison of traditional ultrahigh frequency RFID module for reading and writing, antenna echo improves 3dB.
According to the Friis transmission formula:
Wherein,
The emissive power of transmitter,
The received signal strength of receiver,
With
Respectively the radiation efficiency of receiving antenna, emitting antenna,
Be that the working electromagnet wave-wave is long, R is two distances between the equipment,
With
It is respectively the directive gain of receiving antenna, emitting antenna.
Can get formula by formula (1) conversion:
（2）
Can find out by formula (2): if the antenna gain of read write line and label antenna gain are constant, this moment is because the self-adapting tuning network has improved the standing-wave ratio (SWR) of power amplifier output impedance, and then the leakage energy that enters into receiver obtained largely improving, and known receiving sensitivity is improved 3 dB
Be 30dBm,
(dB) and
(dB) because above-mentioned hypothesis is constant, and
Owing to having improved 3dB, so since equation set up, unique change be exactly
, R=1.4125 then
, R is the requirement between the equipment behind the adding self-adapting tuning network, can get thus conclusion and be: tag read distance improves about 40%.
According to above principle take the R2000 chip as example, in identical antenna, label and test environment, test traditional ultrahigh frequency RFID module for reading and writing with based on the reading/writing distance of the ultrahigh frequency RFID module for reading and writing of antenna self-adaptive tunable technology, make an inventory time and the number of labels of making an inventory, ultrahigh frequency RFID module for reading and writing based on the antenna self-adaptive tunable technology is compared with traditional ultrahigh frequency RFID module for reading and writing, increase the self-adapting tuning network, as shown in Figure 3.Table 1 is experimental result:
Table 1: the Data Comparison that has or not the ultrahigh frequency RFID module for reading and writing of self-adapting tuning network
| The contrast project | Read distance | Make an inventory the time | Number of labels |
| The tradition module for reading and writing | 2.5 rice | 7s | 90 |
| The self-adapting tuning module for reading and writing | 3.5 rice | 3s | 120 |
As can be seen from Table 1, tradition ultrahigh frequency RFID module for reading and writing is compared with the ultrahigh frequency RFID module for reading and writing based on the antenna self-adaptive tunable technology, reading/writing distance improves 40%, the time decreased of making an inventory is more than one times, the number of labels of making an inventory also improves about 30%, can get conclusion thus: read write line sensitivity is enough high, can guarantee that just the label that is in the edge can in time meet with a response, and the skip probability reduces.
Above described be specific embodiments of the invention and the know-why used, if the change of doing according to conception of the present invention when its function that produces does not exceed spiritual that instructions and accompanying drawing contain yet, must belong to protection scope of the present invention.
Claims (8)
1. based on the ultrahigh frequency RFID module for reading and writing of antenna self-adaptive tunable technology, it is characterized in that comprising: central processing unit, the impedance-tumed network of self-adaptation, electric power management circuit, connector, radio-frequency joint, crystal oscillator I, crystal oscillator II; Described crystal oscillator I, connector are connected with central processing unit, the impedance-tumed network connection of central processing unit and self-adaptation, the impedance-tumed network of self-adaptation is connected with radio-frequency joint, described electric power management circuit and connector, central processing unit, crystal oscillator II, the impedance-tumed network connection of self-adaptation, radio-frequency joint links to each other with exterior antenna.
2. the ultrahigh frequency RFID module for reading and writing based on the antenna self-adaptive tunable technology according to claim 1 is characterized in that the impedance-tumed network of self-adaptation comprises: rf chip, power amplifier, coupling mechanism, wave detector, antenna tuning matching network; Described rf chip is connected with central processing unit, crystal oscillator II, power amplifier, power amplifier is connected with coupling mechanism, coupling mechanism is connected with antenna tuning matching network, wave detector, wave detector is connected with central processing unit, the antenna tuning matching network is connected with radio-frequency joint, central processing unit, and electric power management circuit provides power supply for rf chip, power amplifier, antenna tuning matching network.
3. the ultrahigh frequency RFID module for reading and writing based on the antenna self-adaptive tunable technology according to claim 2 is characterized in that central processing unit, rf chip, power amplifier, coupling mechanism, wave detector, antenna tuning matching network form sealing and detect in real time feedback circuit.
4. the ultrahigh frequency RFID module for reading and writing based on the antenna self-adaptive tunable technology according to claim 1 characterized by further comprising heat radiator.
5. the ultrahigh frequency RFID module for reading and writing based on the antenna self-adaptive tunable technology according to claim 3, the topological network that it is characterized in that the antenna tuning matching network can be series, parallel even multi-stage cascade, network progression is more, and the tunable scope of the impedance-tumed network of self-adaptation is just wider.
6. the ultrahigh frequency RFID module for reading and writing based on the antenna self-adaptive tunable technology according to claim 1, the communication interface mode that it is characterized in that the impedance-tumed network of self-adaptation and central processing unit is SPI or I
2C.
7. the ultrahigh frequency RFID module for reading and writing based on the antenna self-adaptive tunable technology according to claim 1 is characterized in that by radio-frequency (RF) switch, can expand to radio-frequency joint a plurality of.
8. the ultrahigh frequency RFID module for reading and writing based on the antenna self-adaptive tunable technology according to claim 1 is characterized in that described electric power management circuit provides 3.3 ~ 5V supply voltage.
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| CN103546188A (en) * | 2013-10-30 | 2014-01-29 | 西安乾易企业管理咨询有限公司 | Wireless mobile terminal of self-tuning antenna and adjusting method of self-tuning antenna |
| CN103606003A (en) * | 2013-12-05 | 2014-02-26 | 上海坤锐电子科技有限公司 | Automatic detuning voltage stabilizing circuit for radio frequency identification tag chip |
| CN103716064A (en) * | 2013-10-21 | 2014-04-09 | 香港应用科技研究院有限公司 | Antenna circuit and optimization method |
| CN105760798A (en) * | 2016-02-04 | 2016-07-13 | 广东小天才科技有限公司 | Improvement method for identification of coil tag installed on three-dimensional device |
| CN106203584A (en) * | 2016-06-27 | 2016-12-07 | 华中科技大学 | RFID antenna impedance self-adaptive control method under a kind of bad working environments |
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| CN103716064A (en) * | 2013-10-21 | 2014-04-09 | 香港应用科技研究院有限公司 | Antenna circuit and optimization method |
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| CN103546188A (en) * | 2013-10-30 | 2014-01-29 | 西安乾易企业管理咨询有限公司 | Wireless mobile terminal of self-tuning antenna and adjusting method of self-tuning antenna |
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| CN105760798A (en) * | 2016-02-04 | 2016-07-13 | 广东小天才科技有限公司 | Improvement method for identification of coil tag installed on three-dimensional device |
| CN106203584A (en) * | 2016-06-27 | 2016-12-07 | 华中科技大学 | RFID antenna impedance self-adaptive control method under a kind of bad working environments |
| CN109660271A (en) * | 2018-12-13 | 2019-04-19 | 电子科技大学 | A kind of the self-interference simulation cancellation system and method for circular polarized antenna |
| CN109660271B (en) * | 2018-12-13 | 2020-04-07 | 电子科技大学 | Self-interference simulation cancellation system and method for circularly polarized antenna |
| WO2021142876A1 (en) * | 2020-01-16 | 2021-07-22 | 惠州Tcl移动通信有限公司 | Radio frequency structure and mobile terminal |
| CN112580376A (en) * | 2020-12-14 | 2021-03-30 | 广东工业大学 | RFID tag antenna impedance tuning method and system based on software and hardware cooperation |
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Application publication date: 20130403 |