CN102254209B - Low and high frequency high sensitivity RFID passive label and batch production method thereof - Google Patents

Abstract

The invention provides a low and high frequency high sensitivity RFID passive label and a batch production method thereof. The passive label comprises tapped coil composing a label double sensing circuit, a tuning capacitor C12, a RFID chip, wherein, with a given card area and external coupling environment, common coil is substituted by the tapped coil, a label circuit is a double sensing circuit; connection topology relations of the tapped coil, the RFID chip and the tuning capacitor C12 are that: the RFID chip connects an initiating terminal of the coil and intermediate tap, and the tuning capacitor C12 connects the initiating terminal of the coil and a termination terminal of the coil. According to the invention, sensitivity and read-write distance of the label are raised.

Description

The method of a kind of low high frequency high sensitivity RFID passive label and batch process thereof

Technical field

The present invention relates to the RFID field, particularly the method for a kind of low high frequency high sensitivity RFID passive label and batch process thereof.

Background technology

(Radio Frequency Identification RFID), is that a kind of read-write equipment utilizes the automatic identification of radiofrequency signal to be attached to the Echo Tag of destination object, and obtains the technology of relevant information radio-frequency (RF) identification, is with a wide range of applications.The RFID technology can be widely applicable for fields such as asset management, production line, commercial distribution, warehouse logistics (can be widely used in land transportation, water transport, aviation), intelligent transportation, commodity counterfeit prevention, tracing and positioning, the RFID technology becomes one of the core technology of " Internet of Things " at present, has huge economy and social effect.

Basic rfid system is made of electronic tag (Tag) and read write line (Reader), often need the support of back-end data base (Back-end DB) in practical application, interconnected by with all kinds of special uses or all purpose communication network can become the organic component of Internet of Things, as shown in Figure 1.Wherein, the working frequency range of rfid system mainly is divided into: low frequency LF, high frequency HF, ultrahigh frequency UHF, microwave M W, and its exemplary operation frequency is respectively: 125KHz/134KHz, 13.56MHz, 433/860-960MHz, 2.45GHz/5.8GHz, as shown in table 1.Low high frequency rfid system is realized the transmission of energy, data based on the principle of work of magnetic field, near field coupling; Ultrahigh frequency and microwave rfid system carry out label to the data transmission of read write line based on the principle of work of far field electromagnetic ripple backscattering coupling.

Table 1

Frequency	Bandwidth	Far, near field boundary	λ/2	International standard
					125KHz/134KHz	N/A	356m	1119m	ISO 18000-2
13.56MHz	±7KHz	3.52m	11.1m	ISO 18000-3/15693，ISO14443
					433.92MHz	±870KHz	11.0cm	34.6cm	ISO 18000-7

860-960MHz	±13MHz(915MHz)	5.2cm	16.4cm	ISO 18000-6
					2.45GHz	±50KHz	1.9cm	6.12cm	ISO 18000-4
5.8GHz	±75KHz	8.22mm	2.59cm	ISO 18000-5

The RFID label can be divided into two types of passive label (Passive tag) and active labels (Active tag).The energy of passive RFID tags is from the radio-frequency (RF) energy of read write line emission, need not built-in power, and have that volume is little, in light weight, cost is low, almost do not have advantage such as restriction in serviceable life, but the more powerful read write line of needs; The energy of active RFID tag is from its built-in power, have long distance identification, the emissive power of read write line is relied on advantages such as little, but cost height, serviceable life is limited.What account for main factor in the cost of rfid system is a large amount of RFID labels that use, and RFID market significantly growth needs function admirable, cheap RFID label promotes just might finish.

Research work about the RFID passive label both at home and abroad has a lot, the difference of different labels mainly is: sensitivity (decipherment distance), label cost, chip type, technology, frequency range, power consumption etc., common low high-frequency RF ID passive label principle schematic is referring to figure (2).

At present low high-frequency RF ID passive label still is faced with the problem of aspects such as sensitivity (decipherment distance) is limited, label cost height, and mainly contain three classes at the gordian technique of hanging down high-frequency RF ID passive label: (one) is about the technology of chip; (2) about the technology of antenna; (3) about the optimization matching technique of antenna and chip.The sensitivity of this three types of technology and passive RFID tags (decipherment distance) and cost are all closely bound up.Wherein (one) class technology mainly comprises four aspects: 1) nucleus module; 2) secure authentication technology; 3) sensor integrated technology; 4) on-chip antenna technology.(2), (three) class key problem in technology is to solve two problems: the 1) optimal design of antenna.In low high-frequency band, the form of RFID label antenna is the multiturn one-turn coil that various technologies are made, the hundreds of circles of low frequency, about high frequency ten circles, the outer stand-alone antenna Q value of general sheet is high, can independently make, cost is moderate, volume is big, coupling is difficult, consistance difficult control, and the achievement of sheet outside antenna can be used for reference in the design of on-chip antenna; 2) passive RFID tags chip energy obtains.Low high-frequency RF ID label is made up of antenna (coil), rf analog front-end, digitial controller and three nucleus modules of storer, antenna (coil), radio-frequency front-end obtain the RF energy to label chip power supply, recovery data and produce clock etc., be the key of steady operation, comprise gordian techniquies such as power match, the RF energy in the radio-frequency front-end obtains, energy conversion efficiency simultaneously.

Summary of the invention

The objective of the invention is to, a kind of low high frequency high sensitivity RFID passive label is provided.

Another object of the present invention is to, a kind of method of batch process of low high frequency high sensitivity RFID passive label is provided.

Low high frequency high sensitivity RFID passive label of the present invention, comprise tapped coil, tuning capacitor C 12, the RFID chip of forming the two sense of label loop, wherein, under given card area, coupled outside environment, replace normal coil with tapped coil, tag circuit is two senses loops; Wherein, tapped coil with the topological relation that is connected of RFID chip and tuning capacitor C 12 is: connect the RFID chip between coil initiating terminal and the centre tap, connect tuning capacitor C 12 between coil initiating terminal and the clearing end.

Wherein, the RFID chip self has resonant capacitance CIC, and wherein, described resonant capacitance CIC gets minimum value.

Wherein, described C12 adopts tunable capacitor Cv of an appearance value fixed capacity C0 to be in parallel.

The method of the above-mentioned low high frequency high sensitivity RFID passive label of batch of the present invention, wherein, RFID label for arbitrary batch, the parameter of the parameter of its tapped coil and RFID chip is at random, for a certain batch coil and RFID chip thereof, the appearance value of the tuning capacitor C 12 that is complementary with it also has random character, C12 is carried out Sampling Estimation, obtain C12 fiducial interval (Cmin, Cmax), degree of confidence is 1-α, wherein, 0＜α＜1, Cmin is confidence lower limit, Cmax is confidence upper limit, the electric capacity nominal value of selected C0 is Cp=Cmin/ (1+ δ), appearance value adjustable extent is more than or equal to the arest neighbors person of (Cmax-Cmin* (1-δ)/(1+ δ)) in the Cv selection STC3Mx-T1 series, and wherein 0＜δ＜1 is the appearance value error of the selected model of fixed capacity C0.

Wherein, numerical control device automatic fine tuning Cv and the reading/writing distance of on-line automatic observing and controlling RFID label on the standard read-write equipment make it reach optimal value maxD, simultaneously according to application demand, label reading/writing distance threshold value DT is set, with maxD＞DT as the qualified condition of batch label.

The invention has the beneficial effects as follows: according to the method for low high frequency high sensitivity RFID passive label of the present invention and batch process thereof, can not need to redesign under the prerequisite of chip, not obvious increase label area, do not increase cost, do not change sourceless characteristic, do not reduce reliability, improved label sensitivity, improved the reading/writing distance of label, but tangible complicacy is not introduced in the making for label, according to test result, sensitivity raising amount＞3dB; Capacitor C 12 appearance values only are 1/4～1/5 of common low high-frequency label matching capacitance under identical frequency of operation, even and the coiling of coil exist under the situation of big consistance difference, the optimal value of matching capacitance C12 still has less fluctuation range; Capacitor C 12 fixed capacity C0 of employing and a tunable capacitor Cv are in parallel and have reduced the label cost, production line of batch adds " RFID label reading/writing distance automatic selection of optimal " node makes label have bigger " coil winding consistance " tolerance ability, has improved qualification rate and production efficiency.

Description of drawings

Fig. 1 is the synoptic diagram of low high frequency (LF, HF) radio-frequency recognition system;

Fig. 2 is common low high frequency passive tag circuit figure;

Fig. 3 is common low high frequency passive label topological diagram;

Fig. 4 is RFID tag circuit figure of the present invention;

Fig. 5 connects topological diagram for RFID label of the present invention is inner;

Circuit diagram model when Fig. 6 is in the read write line coil magnetic field for RFID label of the present invention;

When Fig. 7 is in read-write magnetic field for RFID label of the present invention, the equivalent circuit diagram of read write line coiler part;

When Fig. 8 is in read-write magnetic field for RFID label of the present invention, the equivalent circuit diagram in tag coil " a-c " and loop thereof;

When Fig. 9 is in read-write magnetic field for RFID label of the present invention, the equivalent circuit diagram in tag coil " a-b " and loop thereof;

Figure 10 is the thevenin equivalent circuit figure of Fig. 9;

Figure 11 is for reading and writing coil and RFID tag distances to the synoptic diagram that influences of mutual coupling;

Figure 12 is RFID label automatic batch preferred flow charts.

Embodiment

Below, 1～12 method of describing low high frequency high sensitivity RFID passive label of the present invention and batch process thereof in detail with reference to the accompanying drawings.

Design outline requirement according to the RFID passive label, determine the inside and outside length of side, rounding, the thickness of coil, make mould, for example: standard card requires card length and width size to be respectively: 85mm, 54mm, because the cause of the automatic card dispenser that card management is used, card thickness is necessary＜3mm also, and the allowance of deduction encapsulation is coil full-size permissible range again.The coil initiating terminal is labeled as that " a ", clearing end are labeled as " c ", centre tap is labeled as " b ", determine coil " a-b " number of turn N2, coil " b-c " number of turn N1, coil " a-c " number of turn Ns=N1+N2 according to electrical property (L2, Ls, R2, Rs, M) and every composite request again, select the line footpath of enameled wire.

Be illustrated in figure 5 as radially loose winding structure synoptic diagram, coil is the most inboard to be initiating terminal " a ", around being designated as tap " b " to N2 circle place, the straight IC that connects represents the RFID chip between " a ", " b ", if need add matching capacitance Ca, then Ca is in parallel with IC among the figure, because this label is got Ca=0pf usually, so do not draw; Continuation with rotation direction increase around N1 enclose to the coil outermost be clearing end " c ", connect capacitor C 12 between " a " of coil 1-N1, " c ".Wherein, in two senses loop, a, c are initiating terminal and the clearing end of enameled wire coil, b is tap, and IC represents the RFID chip, because this label is got Ca=0pf usually, the Ca so do not draw, C2=CIC, C0 is in parallel with Cv, C12=C0+Cv, take all factors into consideration the factor that reduces cost and reduce the original paper size, as using demonstration, C0 elects CC41-0805 series fixed capacity as, and Cv elects STC3Mx-T1 series appearance value variable capacitance as.

Figure 5 shows that the coil winding mode that adopts enameled wire radially loose, according to using needs, also can adopt loosen mode, enameled wire of enameled wire normal direction to mix the radially loose mode of loose mode, printed board, the loose mode of printed board normal direction, printed board and mix the mode of loosening and wait to make tapped coil.

As previously mentioned, when getting minimum value owing to C2, be beneficial to the RFID chip and obtain ceiling voltage, label reaches optimum sensitivity, therefore, selects Ca=0pf, C2=CIC, and select the little RFID chip of CIC as far as possible, for example EM4305 (RIC＞100kohm, CIC=330pf), EM4450 (RIC＞100kohm, CIC=170pf) etc., from the CIC angle, chip EM4450 is better than EM4305.

So, C12 serves as the task of control label resonance frequency, for more accurate control capacitance C12 appearance value, to reach optimum tuning-points, do not adopt high-accuracy capacitor simultaneously in order to control cost, C12 adopts a fixed capacity C0 and a tunable capacitor Cv to be in parallel, i.e. C12=C0+Cv.Appearance value fixed capacity C0 adopts CC41-0805 (the appearance value error %5) series that cost is lower, three-dimensional dimension is less, the appearance value variable capacitance STC3Mx-T1 series (STC3M03-T1, STC3M06-T1, STC3M010-T1, STC3M020-T1, STC3M030-T1) that the Cv alternative costs are lower, three-dimensional dimension is less.

For the RFID label of arbitrary batch, the parameter of the parameter of its tapped coil and RFID chip IC all is at random, and the appearance value of the matching capacitance C12 that is complementary with it also has random character, obeys certain distribution.This batch C12 is carried out Sampling Estimation, obtain C12 fiducial interval (Cmin, Cmax), degree of confidence (1-α), 0＜α＜1, Cmin is confidence lower limit, Cmax is confidence upper limit.

Consider that there is δ=5% appearance value error in the CC41-0805 capacitor's capacity, the electric capacity nominal value of selected C0 is Cp=Cmin/ (1+0.05), and so, the confidence lower limit of the actual appearance value of C0 is Cmin* (1-0.05)/(1+0.05), and confidence upper limit is Cmin; The confidence lower limit of Cmax-Cp is Cmax-Cmin simultaneously, and confidence upper limit is Cmax-Cmin* (1-0.05)/(1+0.05); Cv appearance value adjustable extent must be greater than the confidence upper limit of Cmax-Cp, so select in the STC3Mx-T1 series appearance value adjustable extent more than or equal to the arest neighbors person of (Cmax-Cmin* (1-0.05)/(1+0.05)).

So, and the whole fiducial interval of C0+Cv appearance value adjustable extent covering C12 (Cmin, Cmax), thus can be so that the C12 capacitance of each label reaches comparatively ideal requirement in the label in enormous quantities; Simultaneously again can be so that C0 have the electric capacity nominal value of the maximum that all labels all can be allowed in the label in enormous quantities, namely Cv has the range of adjustment of the minimum that this batch label can allow, is beneficial to and improves batch product efficient; This embodiment can tolerate that there is bigger consistance difference in the coiling of coil, has reliability preferably.

Aforementioned " RFID label reading/writing distance automatic selection of optimal " node main flow course of work brief overview is as follows:

1) carries out " Cv regulates sub-process ";

2) carry out " Dmax measures sub-process ", obtain the Dmax of current C v value;

3) record Dmax determines the regulating command of Cv with the variation relation of Cv, sends " Cv regulates sub-process " to;

4) measure the interior maxD=max (Dmax) of Cv variation range;

5) magnitude relationship between judgement maxD and the DT.

Detail flowchart is referring to figure (12).

For RFID label " Dmax measures sub-process ", following basic demands are arranged:

The read write line primary control program can be sent out read write command continuously;

Label wanting and to regulate automatically apart from d above read write line, regulate d by read write line primary control program control actuator, the input parameter of regulating is that can label be read and write, can then increase d, can not then reduce d, the step-length that changes is wanted and can adaptively be regulated, and up to the lucky ultimate range that can read, is Dmax;

Read the numerical value Dmax of maximum reading/writing distance, record sends main flow to;

Whole process time is 1 second-time.

For " Cv regulates sub-process ", following basic demands are arranged:

Cv regulates the reference position that actuator requires to search fast according to the instruction of primary control program Cv=0pf;

According to the order of main flow, increase the Cv value by regulating actuator, perhaps reduce the Cv value, the step-length of variation can be set as required flexibly, also can adaptively regulate;

Whole process time is 1 second-time.

So, can so that the time of reading/writing distance automatic selection of optimal process in 10 second-times of each RFID label finish.

Its course of work is as follows:

Because passive label self charged pool not, need effectively from the LF of reading and writing device antenna coil radiation or HF alternating magnetic field, to obtain enough energy and power to tag circuit so the most important condition that it can operate as normal is exactly the coil of label; Next is that information in the label is carried in the alternating magnetic field that tag coil produces, and the Energy Efficient of being returned by tag reflection is coupled in the read write line coil, and read write line could be separated the information of scale label transmission, and it below is described in detail in detail:

1, obtaining of tag energy and information: when the alleged RFID passive label of the present invention is in the magnetic field of read write line coil, shown in figure (6), the tapped coil induced voltage is as follows: coil " a-b ", coil " a-c " are respectively to produce induced voltage in mutual coupling M02, the M0s alternating magnetic field by the read write line coil

With

Coil " a-b " also can produce induced voltage with mutual coupling M simultaneously from the alternating magnetic field of coil " a-c " Its combined action can cause obtaining on the label chip voltage of more energy and Geng Gao,

${\stackrel{\·}{V}}_L=-\mathrm{j\ω}\·\frac{M_{02}{\stackrel{\·}{I}}_0+M{\stackrel{\·}{I}}_s}{1+(R_2+\mathrm{j\ω}{L}_2)(1/R_{\mathrm{IC}}+\mathrm{j\ω}{C}_2)}$

Can only obtain on the common RFID label chip

${{\stackrel{\·}{V}}^{\′}}_L=-\mathrm{j\ω}\·\frac{M_{02}{\stackrel{\·}{I}}_0}{1+(R_2+\mathrm{j\ω}{L}_2)(1/R_{\mathrm{IC}}+\mathrm{j\ω}{C}_2)}$

The voltage of size.Thereby RFID label of the present invention can obtain more sufficient energy supply, loads on simultaneously

In information be easier to be extracted by chip.

2, label is to the reflection of the energy of load information: this reflection process refers to that in the coupling model of magnetic field the read write line coil is to the coupling of tag coil; For chip and tag coil, refer to that then chip reflexes to the energy of coil, this energy the inside is loaded with the information that needs transmission.For the alleged RFID passive label of the present invention, the energy that reflects from chip at first enters coil " a-b ", there is the transformation relation of boosting in coil " a-b " with coil " a-c ", these two coils produce alternating magnetic field and mutual superposition simultaneously, thereby cause the read write line coil to produce more coupled voltages

Common RFID tag read-write equipment coil can only be coupled to The voltage of size, thus RFID label of the present invention can strengthen the intensity of the information of being extracted by read write line.

With reference to figure 6～Figure 10, above two sensitivity that process all helps to improve the RFID label as can be seen, the reading/writing distance of increase RFID label.

(1) be in the magnetic field of read write line coil when passive label, shown in figure (6), the tapped coil induced voltage is as follows: coil " a-b ", coil " a-c " are respectively to produce induced voltage in mutual coupling M02, the M0s alternating magnetic field by the read write line coil

With

Coil " a-b " also can produce induced voltage with mutual coupling M simultaneously from the alternating magnetic field of coil " a-c " Its combined action can cause obtaining on the label chip voltage of more energy and Geng Gao

Reference diagram (6), figure (6) is made the decoupling equivalent process, obtain figure (7), figure (8), figure (9), consider that mutual coupling is less between read write line coil (belonging to primary return) and the label tapped coil (belonging to the secondary loop), reflected impedance between the two is ignored when doing equivalence, and relational expression is as follows in detail:

$(Z_S+\mathrm{j\ω}{L}_0+R_0){\stackrel{\·}{I}}_s+{\stackrel{\·}{U}}_{\mathrm{SS}}={\stackrel{\·}{V}}_s$

$(\frac{1}{\mathrm{j\ω}{C}_{12}}+\mathrm{j\ω}{L}_s+R_s){\stackrel{\·}{I}}_s+{\stackrel{\·}{U}}_{\mathrm{AS}}=0$

$(\frac{1}{\mathrm{j\ω}{C}_2+\frac{1}{R_{\mathrm{IC}}}}+\mathrm{j\ω}{L}_2+R_2){\stackrel{\·}{I}}_2+{\stackrel{\·}{U}}_{\mathrm{BS}}=0$

${\stackrel{\·}{U}}_{\mathrm{SS}}=\mathrm{j\ω}{M}_{0s}{\stackrel{\·}{I}}_S+\mathrm{j\ω}{M}_{02}{\stackrel{\·}{I}}_2$

${\stackrel{\·}{U}}_{\mathrm{AS}}=\mathrm{j\ω}{M}_{0s}{\stackrel{\·}{I}}_0+\mathrm{j\ω}M{\stackrel{\·}{I}}_2$

${\stackrel{\·}{U}}_{\mathrm{BS}}=\mathrm{j\ω}{M}_{02}{\stackrel{\·}{I}}_0+\mathrm{j\ωM}{\stackrel{\·}{I}}_S$

Z _AS＝R _S+jω(L _S-1/ω ₁₂)

$Z_{f2}=\frac{{\mathrm{\ω}}^2{M}^2}{Z_{\mathrm{AS}}}$

$Z_{\mathrm{BS}}=R_2+\mathrm{j\ω}{L}_2+\frac{1}{1/R_{\mathrm{IC}}+\mathrm{j\ω}{C}_2}$

$Z_{\mathrm{fS}}=\frac{{\mathrm{\ω}}^2{M}^2}{Z_{\mathrm{BS}}}$

Quality factor are all higher when elementary secondary loop, a little less than the elementary secondary loop mutual inductance coupling, like this when the electric current of the elementary secondary loop of estimation, just needn't consider reflection loss resistance Zf2 and Zfs between elementary and secondary.

${\stackrel{\·}{I}}_2=-\frac{\mathrm{j\ω}{M}_{02}{\stackrel{\·}{I}}_0+\mathrm{j\ωM}{\stackrel{\·}{I}}_s}{\frac{1}{\mathrm{j\ω}{C}_2+\frac{1}{R_{\mathrm{IC}}}}+R_2+\mathrm{j\ω}{L}_2}$

${\stackrel{\·}{I}}_s=-\frac{\mathrm{j\ω}{M}_{0s}{\stackrel{\·}{I}}_0+\mathrm{j\ωM}{\stackrel{\·}{I}}_2}{(\frac{1}{\mathrm{j\ω}{C}_{12}}+\mathrm{j\ω}{L}_s+R_s)}$

${\stackrel{\·}{V}}_L=-\mathrm{j\ω}\·\frac{M_{02}{\stackrel{\·}{I}}_0+M{\stackrel{\·}{I}}_s}{1+(R_2+j{\mathrm{\ωL}}_2)(1/R_{\mathrm{IC}}+\mathrm{j\ω}{C}_2)}$

When each loop resonance was worked, each stack item was with superimposed.

As a comparison, common low high frequency passive label shown in figure (2), the figure (3), under equal conditions, the voltage that the RFID chip IC obtains is:

${{\stackrel{\·}{V}}^{\′}}_L=-\mathrm{j\ω}\·\frac{M_{02}{\stackrel{\·}{I}}_0}{1+(R_2+j{\mathrm{\ωL}}_2)(1/R_{\mathrm{IC}}+\mathrm{j\ω}{C}_2)}$

Obviously, ${\stackrel{\·}{V}}_L>{{\stackrel{\·}{V}}^{\′}}_L$

According to Thevenin theorem, figure (9) can equivalence be (10), and:

${\stackrel{\·}{U}}_{\mathrm{oc}}=\frac{\frac{1}{\mathrm{j\ω}{C}_2}}{R_2+\mathrm{j\ω}{L}_2+Z_{f2}+1/\mathrm{j\ω}{C}_2}\·{\stackrel{\·}{U}}_{\mathrm{BS}}$

$Z_{\mathrm{OC}}=R_{\mathrm{OC}}+j{X}_{\mathrm{OC}}=\frac{1}{\frac{1}{R_2+\mathrm{j\ω}{L}_2+\frac{{\mathrm{\ω}}^2{M}^2}{R_S+\mathrm{j\ω}{L}_S+1/\mathrm{j\ω}{C}_{12}}}+\mathrm{j\ω}{C}_2}$

When Xoc=0, the RFID label reaches simple harmonic, can obtain C12 accordingly.

Meanwhile, when Roc=RIC, conjugate impedance match, the RFID chip obtains peak power:

$P_{L\max }=\frac{{\stackrel{\·}{U}}_{\mathrm{oc}}^2}{4R_{\mathrm{OC}}}$

Above-listed various in, M depends on the RFID label preparing technology, fixes for a label M who completes, M02, M0s then depend on relative position and the distance of RFID label and read-write equipment coil, for the position relation of figure shown in (11), have:

$M_{0s}=k\·\sqrt{L_0\·L_s}$

$M_{02}=k\·\sqrt{L_0\·L_2}$

$k=\frac{r_R^2\·r_T^2\·\cos \left(\mathrm{\θ}\right)}{\sqrt{r_R\·r_T}\·{(r_R^2+x^2)}^{3/2}}$

For the RFID label of identical attitude, the parameter that influences M02 and M0s has only x, for identical x,

Mean that namely RFID label of the present invention has higher sensitivity; When

The time RFID label of the present invention have bigger x, namely mean farther reading/writing distance under identical read-write condition.

As shown in figure 11, the alternating magnetic field intensity that B produces for the read write line coil among the figure,

$B=\frac{\mathrm{\μ}\·I_R\·N_R\·r_R^2}{2{(r_R^2+x^2)}^{3/2}}$

I in the formula _R, N _RBe respectively electric current and the number of turn of read write line coil, x is read-write coil and RFID tag distances, B with the Changing Pattern of x be reflected in the coupling coefficient k that reads and writes coil and RFID tag coil in,

$k=\frac{r_R^2\·r_T^2\·\cos \left(\mathrm{\θ}\right)}{\sqrt{r_R\·r_T}\·{(r_R^2+x^2)}^{3/2}}$

So mutual coupling

With mutual coupling

Changing Pattern with x has also reflected the Changing Pattern of B with x simultaneously.

(2) from

And Z _OCExpression formula as can be seen, when satisfying condition of resonance, when C2 gets minimum value

Reach maximal value, Z _OCReach minimum value, be beneficial to the RFID chip and obtain ceiling voltage, label reaches optimum sensitivity.

When C2 gets possible minimum value, regulate the task of resonance and just finish by C12, therefore C12 is had higher accuracy requirement, in order to control cost, C12 adopts a fixed capacity C0 and a tunable capacitor Cv to be in parallel, i.e. C12=C0+Cv.

(3) criticizing of RFID label originated from " RFID label reading/writing distance automatic selection of optimal " as described below node of increase on the moving production line: numerical control device is regulated Cv and the reading/writing distance of on-line automatic observing and controlling RFID label on the standard read-write equipment automatically, makes it reach optimum.Concrete, according to application demand, label reading/writing distance threshold value DT is set, before label encapsulates fully, allows standard RFID label read-write equipment be in maximum reading/writing distance automatic measuring and controlling mode of operation, regulate Cv and the simultaneously automatic current maximum reading/writing distance Dmax of measure R FID label, get the maximum maxD among all Dmax, Cv gets corresponding with it value, if maxD＞DT, then label is qualified, and flow process is referring to figure (12).

In sum, method according to low high frequency high sensitivity RFID passive label of the present invention and batch process thereof, can not need to redesign under the prerequisite of chip, not obvious increase label area, do not increase cost, do not change sourceless characteristic, do not reduce reliability, improved label sensitivity, improved the reading/writing distance of label, but tangible complicacy is not introduced in the making for label, according to test result, and sensitivity raising amount＞3dB; Capacitor C 12 appearance values only are 1/4～1/5 of common low high-frequency label matching capacitance under identical frequency of operation, even and the coiling of coil exist under the situation of big consistance difference, the optimal value of matching capacitance C12 still has less fluctuation range; Capacitor C 12 fixed capacity C0 of employing and a tunable capacitor Cv are in parallel and have reduced the label cost, production line of batch adds " RFID label reading/writing distance automatic selection of optimal " node makes label have bigger " coil winding consistance " tolerance ability, has improved qualification rate and production efficiency.

More than be in order to make those of ordinary skills understand the present invention; and the detailed description that the present invention is carried out; but can expect; in not breaking away from the scope that claim of the present invention contains, can also make other variation and modification, these variations and revising all in protection scope of the present invention.

Claims (5)

1. one kind low high frequency high sensitivity RFID passive label comprises tapped coil, tuning capacitor C 12, the RFID chip of forming the two sense of label loop, it is characterized in that:

Under given card area, coupled outside environment, replace normal coil with tapped coil, tag circuit is two senses loops; Wherein, tapped coil with the topological relation that is connected of RFID chip and tuning capacitor C 12 is: connect the RFID chip between coil initiating terminal and the centre tap, connect tuning capacitor C 12 between coil initiating terminal and the clearing end.

2. low high frequency high sensitivity RFID passive label as claimed in claim 1 is characterized in that:

The RFID chip self has resonant capacitance CIC, and wherein, described resonant capacitance CIC gets minimum value.

3. low high frequency high sensitivity RFID passive label as claimed in claim 1 is characterized in that:

Described C12 adopts an appearance value fixed capacity C0 and a tunable capacitor Cv to be in parallel.

4. a batch process is characterized in that as the method for low high frequency high sensitivity RFID passive label as described in the claim 3:

RFID label for arbitrary batch, the parameter of the parameter of its tapped coil and RFID chip is at random, for a certain batch coil and RFID chip thereof, the appearance value of the tuning capacitor C 12 that is complementary with it also has random character, C12 is carried out Sampling Estimation, obtain the fiducial interval (Cmin of C12, Cmax), degree of confidence is 1-α, wherein, 0＜α＜1, Cmin is confidence lower limit, Cmax is confidence upper limit, the electric capacity nominal value of selected C0 is Cp=Cmin/ (1+ δ), appearance value adjustable extent is more than or equal to the arest neighbors person of (Cmax-Cmin* (1-δ)/(1+ δ)) in the Cv selection STC3Mx-T1 series, and wherein 0＜δ＜1 is the appearance value error of the selected model of fixed capacity C0.

5. method as claimed in claim 4 is characterized in that, comprises the following steps:

Numerical control device automatic fine tuning Cv and the reading/writing distance of on-line automatic observing and controlling RFID label on the standard read-write equipment, make it reach optimal value maxD, simultaneously according to application demand, label reading/writing distance threshold value DT being set, with maxD〉DT is as the qualified condition of batch label.

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