CN111275147B - RFID (radio frequency identification) tag sensing system and method without calibration - Google Patents

RFID (radio frequency identification) tag sensing system and method without calibration Download PDF

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CN111275147B
CN111275147B CN202010063581.9A CN202010063581A CN111275147B CN 111275147 B CN111275147 B CN 111275147B CN 202010063581 A CN202010063581 A CN 202010063581A CN 111275147 B CN111275147 B CN 111275147B
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sensing
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rfid tag
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reader
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CN111275147A (en
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李涵雄
张旭
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Central South University
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    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06K—GRAPHICAL DATA READING; PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS
    • G06K17/00—Methods or arrangements for effecting co-operative working between equipments covered by two or more of main groups G06K1/00 - G06K15/00, e.g. automatic card files incorporating conveying and reading operations
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06K—GRAPHICAL DATA READING; PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS
    • G06K19/00—Record carriers for use with machines and with at least a part designed to carry digital markings
    • G06K19/06—Record carriers for use with machines and with at least a part designed to carry digital markings characterised by the kind of the digital marking, e.g. shape, nature, code
    • G06K19/067—Record carriers with conductive marks, printed circuits or semiconductor circuit elements, e.g. credit or identity cards also with resonating or responding marks without active components
    • G06K19/07—Record carriers with conductive marks, printed circuits or semiconductor circuit elements, e.g. credit or identity cards also with resonating or responding marks without active components with integrated circuit chips
    • G06K19/0723—Record carriers with conductive marks, printed circuits or semiconductor circuit elements, e.g. credit or identity cards also with resonating or responding marks without active components with integrated circuit chips the record carrier comprising an arrangement for non-contact communication, e.g. wireless communication circuits on transponder cards, non-contact smart cards or RFIDs
    • G06K19/0726—Record carriers with conductive marks, printed circuits or semiconductor circuit elements, e.g. credit or identity cards also with resonating or responding marks without active components with integrated circuit chips the record carrier comprising an arrangement for non-contact communication, e.g. wireless communication circuits on transponder cards, non-contact smart cards or RFIDs the arrangement including a circuit for tuning the resonance frequency of an antenna on the record carrier
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06K—GRAPHICAL DATA READING; PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS
    • G06K7/00—Methods or arrangements for sensing record carriers, e.g. for reading patterns
    • G06K7/10—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation
    • G06K7/10009—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation sensing by radiation using wavelengths larger than 0.1 mm, e.g. radio-waves or microwaves
    • G06K7/10118—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation sensing by radiation using wavelengths larger than 0.1 mm, e.g. radio-waves or microwaves the sensing being preceded by at least one preliminary step

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Abstract

The invention discloses a RFID label sensing system and a method without calibration, wherein the system comprises: the system comprises a control terminal, a reader-writer and an RFID label with an Auto Tune; the reader-writer is used for sending an Auto Tune closing and opening instruction to the RFID tag, receiving first sensing information and second sensing information reflected by the RFID tag under the Auto Tune closing state and the Auto Tune opening state respectively, and acquiring a Memory value of the RFID tag; the control terminal is used for dividing the plurality of sensing states according to the input parallel capacitance values corresponding to different Memory value values and acquiring the sensing states according to the first sensing information, the second sensing information and the Memory value values. According to the system and the method provided by the invention, a fixed position is not required between the reader-writer and the RFID label, and the control terminal can acquire the corresponding sensing state through the sensing information such as the phase, the amplitude and the like returned by the RFID label and the Memory value.

Description

RFID (radio frequency identification) tag sensing system and method without calibration
Technical Field
The invention relates to the technical field of RFID, in particular to an RFID label sensing system and method without calibration.
Background
In the past decades, passive ultra high frequency radio frequency identification (UHF RFID) technology has been widely used for real-time inventory, industrial automation, and identification requiring only an identification function. Over the past few years, a great deal of work has been attempted to add sensing functionality to RFID, passive RFID sensing being achieved primarily through two different architectures, digital and analog, respectively, as shown in table 1 below:
Figure BDA0002375269880000011
TABLE 1
In an analog RFID sensor, the impedance (Z) of the antennaant) Will vary with the electromagnetic conditions (permittivity, permeability, conductivity) and environment (antenna structure changes due to stretching, compression, bending, expansion, etc.) in the vicinity of the tag. To date, RFID sensor tags have been prototyped for temperature sensing, displacement sensing, fill level sensing, strain and crack sensing, bend sensing, and skin sensing. The basic analog mode RFID sensor operates as shown in fig. 1.
Taking temperature sensing as an example, fig. 2 shows an environment where the RFID analog sensor is attached to a temperature change, and the reader/writer obtains corresponding temperature information according to amplitude, phase, and frequency offset information of a reflected signal, thereby implementing temperature sensing.
Although analog-mode RFID sensors have proven to be viable in many areas, the problem of requiring additional calibration has greatly limited the wide range of applications for analog-mode RFID sensors.
When the phase of the reflected signal is used as sensing, let the environment variable be Ψ, then the phase of the reflected signal acquired by the reader/writer is:
Figure BDA0002375269880000021
wherein the content of the first and second substances,
Figure BDA0002375269880000022
indicating that the reader acquires the phase value of the signal when the environment is psi, -2k0r represents the distance of the reader from the tag resulting in a phase value,
Figure BDA0002375269880000023
indicating the phase value resulting from the polarization matching of the reader antenna and the tag antenna,
Figure BDA0002375269880000024
due to the antenna impedance ZA[Ψ]The resulting phase value.
From
Figure BDA0002375269880000025
It can be seen that in order to realize sensing, the distance and relative position between the reader-writer and the tag need to be fixed, that is, the reader-writer and the tag need to be fixed
Figure BDA0002375269880000026
Can be connected with
Figure BDA0002375269880000027
To Ψ one by oneThe corresponding relationship realizes sensing. When the relative position of the reader-writer and the label changes, extra calibration is needed to obtain a correct sensing value.
When the amplitude of the reflected signal is taken as a sensing index:
Figure BDA0002375269880000028
wherein, PR←T[Ψ]Amplitude, P, of reflected signal received by reader/writer when environment is psiavDenotes the power taken by the antenna, d denotes the distance of the reader from the tag, GR(theta, phi) represents the antenna gain of the reader/writer, GT(theta, phi) represents the gain of the tag antenna, etapRepresenting the polarization mismatch coefficient, τ [ psi ]]Representing the energy transfer coefficient of the antenna and the chip. For the same phase sensing, the relative position of the reader/writer and the tag needs to be fixed.
τ[Ψ]＝1-|Schip[Ψ]|2
Figure BDA0002375269880000029
The chip usually has two impedances, respectively an absorption impedance ZabsAnd a reflection impedance ZrefThe corresponding reflection coefficients are:
Figure BDA0002375269880000031
Figure BDA0002375269880000032
since RFID tags are typically attached to different objects, item tracking is achieved. Therefore, when designing an RFID tag antenna, developers often design the size of the antenna according to physical characteristics (dielectric constant, magnetic permeability, electrical conductivity, etc.) of a target object, so that impedance when the antenna is attached to the target object is conjugate-matched with impedance of a chip. This limits the versatility of the tag to some extent. Therefore, an RFID chip manufacturer adds an AutoTune function to the chip, so that the RFID tag can adapt to different attached objects, and the RFID tag can achieve a better reading distance under the condition of different attached objects; the AutoTune function is mainly used for adjusting the impedance of the chip, increasing the impedance matching degree of the chip and the antenna, improving the energy obtained by the chip, reducing the energy reflection and finally improving the adaptability of the RFID chip.
At present, when the variation of external non-sensing variables occurs (namely the variation of the relative distance and the relative angle between a reader-writer and a tag occurs), the application of the RFID analog sensor is greatly limited by the limiting condition of needing additional calibration.
Disclosure of Invention
The present invention is directed to solve at least one of the technical problems of the prior art, and provides a calibration-free RFID tag sensing system and method, which can obtain a corresponding sensing state when an external non-sensing variable changes, without calibration.
The embodiment of the invention provides an RFID label sensing system and method without calibration.
According to an embodiment of the first aspect of the invention, the calibration-free RFID tag sensing system comprises: the system comprises a control terminal, a reader-writer and an RFID label with an Auto Tune; the reader-writer is used for sending Auto Tune closing and opening instructions to the RFID tag, receiving first sensing information and second sensing information reflected by the RFID tag under the Auto Tune closing state and the Auto Tune opening state respectively, and acquiring a Memory value of the RFID tag; the control terminal is used for dividing a plurality of sensing states according to input parallel capacitance values corresponding to different Memory value values and acquiring the sensing states according to the first sensing information, the second sensing information and the Memory value values.
Compared with the prior art, the calibration-free RFID tag sensing system disclosed by the embodiment of the disclosure has at least the following beneficial effects:
according to the system provided by the invention, the opening state and the closing state are generated according to the function of the RFID tag AutoTune, and when the external non-sensing variable changes, the AutoTune actively adjusts the input parallel capacitance value of the AutoTune so as to adjust the conjugate matching in the RFID tag.
According to some embodiments of the present invention, the control terminal divides a plurality of sensing states into three regions, at most one sensing state is set in a first region, and the sensing state in the first region corresponds to a Memory value with an input parallel capacitance value of 0; the sensing state in the second area corresponds to a Memory value with an input parallel capacitance value smaller than 0; the sensing state in the third area corresponds to a Memory value with an input parallel capacitance value larger than 0; and the control terminal acquires the sensing states in the second area and the third area according to the first sensing information and the second sensing information.
According to some embodiments of the invention, the first sensing information comprises a first amplitude value and a first phase value; the second sensing information includes a second amplitude value and a second phase value.
According to the second aspect of the invention, the calibration-free RFID label sensing method comprises the following steps:
the method comprises the steps that a reader-writer sends an Auto Tune closing instruction to an RFID label with an Auto Tune function, and first sensing information reflected by the RFID label is received;
the reader-writer sends an Auto Tune opening instruction to the RFID tag and receives second sensing information reflected by the RFID tag;
the reader-writer sends a reading instruction to the RFID tag to acquire a Memory value in the Auto Tune;
and the control terminal acquires a sensing state according to the first sensing information, the second sensing information and the Memory value.
Compared with the prior art, the method for sensing the RFID tag without calibration disclosed by the embodiment of the disclosure has at least the following beneficial effects:
according to the method provided by the invention, two states of opening and closing are generated according to the function of the RFID tag AutoTune, and when the external non-sensing variable changes, the AutoTune actively adjusts the input parallel capacitance value of the AutoTune, so that the conjugate matching in the RFID tag is adjusted; therefore, the method can realize sensing of the reader-writer and the RFID label under the conditions of different relative distances or different relative angles, namely, the reader-writer and the RFID label do not need to be fixed, and the control terminal can obtain the corresponding sensing state through sensing information such as phase, amplitude and the like returned by the RFID label and the Memory value.
According to some embodiments of the present invention, the method for acquiring, by the control terminal, the sensing state according to the first sensing information, the second sensing information, and the Memory value includes:
if the input parallel capacitance value corresponding to the Memory value is 0, the control terminal acquires a corresponding sensing state according to the Memory value;
and if the input parallel capacitance value corresponding to the Memory value is not 0, the control terminal acquires a corresponding sensing state according to the first sensing information and the second sensing information.
According to some embodiments of the invention, the first sensing information comprises a first amplitude value and a first phase value; the second sensing information includes a second amplitude value and a second phase value.
Further features and advantages realized by the embodiments of the present disclosure will be set forth in the detailed description or may be learned by the practice of the embodiments.
Drawings
The invention is further described below with reference to the accompanying drawings and examples;
FIG. 1 is a schematic diagram of the operation of an analog RFID tag provided in the prior art;
FIG. 2 is a schematic diagram of a working flow of an RFID analog temperature sensor provided in the prior art;
FIG. 3 is a schematic structural diagram of an RFID tag sensing system without calibration according to an embodiment of the present invention;
FIG. 4 is a schematic diagram of a sensing process of an RFID tag sensing system without calibration according to an embodiment of the present invention;
FIG. 5 is a flow chart of a method for sensing an RFID tag without calibration according to an embodiment of the present invention;
FIG. 6 is a schematic diagram of a T-match antenna topology according to an embodiment of the present invention;
fig. 7 is a schematic diagram illustrating a relationship between an RFID tag and a reader/writer according to an embodiment of the present invention.
Detailed Description
The technical solutions of the embodiments of the present disclosure will be described clearly and completely with reference to the accompanying drawings, and it is to be understood that the described embodiments are only a part of the embodiments of the present disclosure, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the disclosure without making any creative effort, shall fall within the protection scope of the disclosure. It should be noted that the features of the embodiments and examples of the present disclosure may be combined with each other without conflict. In addition, the purpose of the drawings is to graphically supplement the description in the written portion of the specification so that a person can intuitively and visually understand each technical feature and the whole technical solution of the present disclosure, but it should not be construed as limiting the scope of the present disclosure.
For ease of understanding, the Auto Tune function of the RFID tag is described below:
RFID chip manufacturers have developed Auto Tune functional chips, such as Monza R6 chip, SL3S1205_15UCODE 8/8m chip, and the like, in order to improve the chip adaptability. Here, taking the Monza R6 chip as an example, the chip has the following three typical characteristics:
(1) the AutoTune can send an opening instruction or a closing instruction by a reader-writer and enter an opening state or a closing state;
(2) the AutoTune can automatically adjust and record the RFID Input parallel capacitance value (Input capacitance value);
(3) a Memory value is arranged in the AutoTune. When the Auto Tune is in the on state, the chip will automatically adjust input capacitance value, and the parallel capacitance variation value is one-to-one corresponding to the Memory value. For example, as shown in table 2 below: the reader/writer can send an instruction to read the Memory value. When the Memory value is 0002, it indicates that the parallel capacitance is not changed, and when the Memory value is 0000, it indicates that the parallel capacitance is reduced by 100 ff; when Memory value is 0003, it indicates that the parallel capacitance is increased by 40 ff. It should be noted that the current R6 chip only supports these 5 values, and there are differences between different chips.
Memory value Input capacitance value difference(ff)
0000 -100
0001 -40
0002 0
0003 40
0004 100
TABLE 2
In the prior art, the introduction of the AutoTune function is a micro-power consumption circuit for improving the impedance matching between an antenna and a chip; therefore, if perfect conjugate matching is realized between the antenna impedance and the chip impedance of the RFID tag, the capacitance value will not change after the AutoTune is turned on; if the antenna impedance and the chip impedance do not achieve perfect conjugate matching, the capacitance will be automatically adjusted to obtain better conjugate matching after the AutoTune is turned on, i.e. τ (energy transmission coefficient of the antenna and the chip) will be increased after the AutoTune is turned on.
The AutoTune adjusts the absorption impedance Z when the current environmental variable is ΨabsThe value of (1), i.e. AutoTune yields Z in the open state and the closed state, respectivelyabs_o[Ψ]，Zabs_n[Ψ]The corresponding reflection coefficients are respectively: zA[Ψ]Representing the impedance, Z, of the antenna when the ambient variable is ΨA *[Ψ]Representing the conjugate impedance of the antenna when the environment variable is Ψ.
Due to the fact that
Figure BDA0002375269880000071
Thus τn[Ψ]＝1-|Sabs_n[Ψ]|2，τo[Ψ]＝1-|Sabs_o[Ψ]|2
Post-modulation of Δ τ [ psi ]]＝τn[Ψ]-τo[Ψ]，Δτ[Ψ]Not less than 0; from table 2 above, it can be seen that:
when Δ τ [ Ψ ] ═ 0, which indicates that the capacitance value of the AutoTune is not changed when it is turned on and off, then Memory value equals 0002, and the corresponding input parallel capacitance value equals 0.
When [ Delta ] t [ psi ]]>0, indicating that the capacitance has changed when the AutoTune is turned on and off, and Z is the sameabs_n！＝Zabs_oThe Memory value is equal to one of 0000, 0001, 0003, or 0004; and according to the formula of the amplitude difference and the phase difference, the following can be calculated:
ΔRSSI＝10log10ΔPR←T[Ψ]＝10log10Δτ[Ψ]dBm
Figure BDA0002375269880000081
therefore, based on Memory value, Δ RSSI (amplitude difference),
Figure BDA0002375269880000082
The sensing state can be effectively distinguished.
Without loss of generality, assume sensing states are Ψ1，Ψ2，Ψ3，Ψ4In order to realize the RFID tag sensing without calibration, the following design is only required when the antenna of the RFID tag is designed:
the antenna impedance of at most one sensing state Ψ is such that Δ τ [ Ψ ] ═ 0, that is, when the Memory value is 0002, at most one sensing state is matched;
when the impedance of the antenna is such that Δ τ [ Ψ ]]>When 0, the two groups of Memory values 0000 and 0001 are divided into one group, the two groups of Memory values 0003 and 0004 are divided into one group, and the two groups respectively contain a plurality of sensing states, so that the Δ RSSI sum can be used as the basis
Figure BDA0002375269880000083
The different sensing states in each group are distinguished.
Referring to fig. 3 and 4, one embodiment of the present invention provides an RFID tag sensing system without calibration, including: the system comprises a control terminal, a reader-writer and an RFID label with an Auto Tune; the reader-writer is used for sending an Auto Tune closing and opening instruction to the RFID tag, receiving first sensing information and second sensing information reflected by the RFID tag under the Auto Tune closing state and the Auto Tune opening state respectively, and acquiring a Memory value of the RFID tag; the control terminal is used for dividing the plurality of sensing states according to input parallel capacitance values corresponding to different Memory value values and obtaining the sensing states according to the first sensing information, the second sensing information and the Memory value values.
The control terminal can be a computer or a mobile terminal; the RFID tag comprises an RFID chip and an antenna, wherein the RFID chip can be a Monza R6 chip or a SL3S1205_15UCODE 8/8m chip with Auto Tune function.
As one possible implementation, the first sensing information includes a first amplitude value and a first phase value; the second sensing information comprises a second amplitude value and a second phase value; and subtracting the second amplitude value from the first amplitude value to obtain an amplitude difference, and subtracting the second phase value from the first phase value to obtain a phase difference. Of course, the sensing information may also include a frequency offset value, etc., but here, the amplitude value and the phase value can be applied to most application scenarios.
As an implementable manner, the control terminal divides a plurality of sensing states into three regions, at most one sensing state is set in a first region, and the sensing state in the first region corresponds to a Memory value with an input parallel capacitance value of 0; the sensing state in the second area corresponds to a Memory value with an input parallel capacitance value smaller than 0; the sensing state in the third area corresponds to a Memory value with an input parallel capacitance value larger than 0; and the control terminal acquires the sensing states in the second area and the third area according to the amplitude difference and the phase difference. Of course, it may also be divided in other ways, for example: dividing Memory value into 0000, 0001, 0002, 0003 and 0004 respectively; it should be noted that more than one sensing state can be matched in the area partitioned by taking the Memory value as 0002, and if the Memory value acquired by the reader-writer is equal to 0002, that is, the input parallel capacitance value is 0, the control terminal can directly acquire the corresponding sensing state; if the Memory value obtained by the reader-writer is not equal to 0002, that is, the input parallel capacitance value is not 0, the control terminal needs to further distinguish different sensing states in each region according to the amplitude difference and the phase difference information.
According to the conclusion, the system provided by the embodiment generates the opening state and the closing state according to the function of the RFID tag AutoTune, and when the external non-sensing variable changes, the AutoTune actively adjusts the input parallel capacitance value, so as to adjust the conjugate matching in the RFID tag; therefore, by the system, a fixed position is not needed between the reader-writer and the RFID label, and the control terminal can obtain the corresponding sensing state through the amplitude difference, the phase difference and the Memory value returned by the RFID label.
Referring to fig. 5, according to the above conclusion, an embodiment of the present invention provides a method for sensing an RFID tag without calibration, including the following steps:
s100, the reader-writer sends an Auto Tune closing instruction to the RFID label with the Auto Tune function, and receives a first amplitude value and a first phase value reflected by the RFID label;
s200, the reader-writer sends an Auto Tune opening instruction to the RFID tag, and receives a second amplitude value and a second phase value reflected by the RFID tag;
s300, the reader-writer sends a reading instruction to the RFID tag to obtain a Memory value in the Auto Tune;
s400, the control terminal calculates the amplitude difference and the phase difference, and obtains the sensing state according to the amplitude difference, the phase difference and the Memory value:
if the input parallel capacitance value corresponding to the Memory value is 0, acquiring a corresponding sensing state according to the Memory value;
and if the input parallel capacitance value corresponding to the Memory value is not 0, acquiring the corresponding sensing state according to the amplitude difference and the phase difference.
It should be noted that the interval between S100 and S200 is short, and it can be considered that neither the channel nor the relative position has changed at this time.
According to the method provided by the embodiment, the opening state and the closing state are generated according to the function of the RFID tag AutoTune, when the external non-sensing variable changes, the AutoTune actively adjusts and inputs the parallel capacitance value, so that the conjugate matching in the RFID tag is adjusted, and therefore, the sensing of the reader-writer and the RFID tag under the conditions of different relative distances or different relative angles can be achieved through the method, namely, no fixed position is needed between the reader-writer and the RFID tag, and the sensing state can be obtained through the amplitude difference, the phase difference and the Memory value returned by the RFID tag by the control terminal.
It should be noted that: since the calibration-free RFID tag sensing method in this embodiment is based on the same inventive concept as the calibration-free RFID tag sensing system in the above embodiment, the corresponding contents in the system embodiment are also applicable to this method embodiment, and will not be described in detail here.
Referring to fig. 6 and 7, for convenience of understanding, the following is an implementation flow of temperature measurement according to an embodiment of the system of the present invention:
the RFID tag takes a T-match antenna and a Monza R6 chip as an example, and FIG. 6 shows a T-match antenna topology;
the first step is as follows: selecting a dielectric material;
selecting Rogers RT/duroid6006 material, wherein the parameters comprise: the coefficient of thermal expansion was 47/34/117 ppm/deg.C in x/y/z. Dielectric constant-410 ppm/. degree.C
The second step is that: optimizing antenna parameters;
the impedance conditions of the antenna under different temperature conditions are obtained through commercial electromagnetic simulation software, wherein f is the working frequency, the antenna size and the working frequency result are shown in the following table 3, and the units are mm and GHz respectively:
χ1 χ2 χ3 χ4 χ5 χ6 f
92.4 4.8 25.75 2.7 7.5 0.292 0.8762
TABLE 3
The third step: the sensing state information mapped by the method of the above embodiment is shown in table 4 below:
Figure BDA0002375269880000111
TABLE 4
The fourth step: acquiring sensing information;
as shown in fig. 7, in the transmissible distance, in the prior art manner, the reader/writer needs to be respectively calibrated with the RFID tag at the positions S1, S2, and S3, and then accurate sensing can be realized. By the implementation method, the reader-writer can move randomly among the positions S1, S2 and S3, and sensing can be realized without extra calibration; the specific acquired sensing state process is as follows:
when the Memory value returned by the RFID tag received by the reader-writer is 0002, that is, the input probability value is 0ff, the control terminal obtains the sensing state as follows: the temperature T is 40 degrees.
When the Memory value returned by the RFID tag received by the reader-writer is 0000, namely the input probability value is +100ff, the control terminal controls the RFID tag to read and write according to the difference between the delta RSSI (amplitude difference) and the delta RSSI (amplitude difference) 1,
Figure BDA0002375269880000112
The sensing state is acquired as follows: the temperature T is 30 degrees;
when the Memory value returned by the RFID tag received by the reader-writer is 0000, namely the input probability value is-100 ff, the control terminal controls the RFID tag to read and write according to the difference between the delta RSSI (amplitude difference) and the delta RSSI,
Figure BDA0002375269880000113
The sensing state is acquired as follows: the temperature T is 50 degrees; according to the delta RSSI (amplitude difference) 1,
Figure BDA0002375269880000114
The sensing state is acquired as follows: the temperature T is 60 degrees.
The embodiments of the present invention have been described in detail with reference to the accompanying drawings, but the present invention is not limited to the above embodiments, and various changes can be made within the knowledge of those skilled in the art without departing from the gist of the present invention.

Claims (2)

1. An RFID tag sensing system that does not require calibration, comprising: the system comprises a control terminal, a reader-writer and an RFID label with an Auto Tune; the reader-writer is used for sending Auto Tune closing and opening instructions to the RFID tag, receiving first sensing information and second sensing information reflected by the RFID tag under the Auto Tune closing state and the Auto Tune opening state respectively, and acquiring a Memory value of the RFID tag, wherein the first sensing information comprises a first amplitude value and a first phase value; the second sensing information comprises a second amplitude value and a second phase value; the control terminal is used for dividing a plurality of sensing states into three regions, at most one sensing state is arranged in a first region, and the sensing state in the first region corresponds to a Memory value with an input parallel capacitance change value of 0; the sensing state in the second area corresponds to a Memory value of which the input parallel capacitance change value is less than 0; the sensing state in the third region corresponds to a Memory value at which an input parallel capacitance change value is greater than 0, and is used for acquiring the sensing state located in the first region according to the Memory value, and acquiring the sensing states located in the second region and the third region according to an amplitude difference and a phase difference calculated from the first sensing information and the second sensing information.
2. A method of RFID tag sensing without calibration, comprising the steps of:
the method comprises the steps that a reader-writer sends an Auto Tune closing instruction to an RFID label with an Auto Tune function, and first sensing information reflected by the RFID label is received, wherein the first sensing information comprises a first amplitude value and a first phase value;
the reader-writer sends an Auto Tune opening instruction to the RFID tag, and receives second sensing information reflected by the RFID tag, wherein the second sensing information comprises a second amplitude value and a second phase value;
the reader-writer sends a reading instruction to the RFID tag to acquire a Memory value in the Auto Tune;
the control terminal obtains the sensing state according to the amplitude difference and the phase difference calculated by the first sensing information and the second sensing information and the Memory value:
if the input parallel capacitance change value corresponding to the Memory value is 0, the control terminal acquires a corresponding sensing state according to the Memory value;
and if the input parallel capacitance change value corresponding to the Memory value is not 0, the control terminal acquires a corresponding sensing state according to the amplitude difference and the phase difference.
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