CN109447223B

CN109447223B - Method for enhancing reflected power of ultrahigh frequency RFID (radio frequency identification) tag

Info

Publication number: CN109447223B
Application number: CN201811283580.4A
Authority: CN
Inventors: 沈红伟
Original assignee: Huada Hengxin Technology Co ltd
Current assignee: Sichuan Huada Hengxin Technology Co., Ltd.
Priority date: 2018-10-31
Filing date: 2018-10-31
Publication date: 2021-09-14
Anticipated expiration: 2038-10-31
Also published as: CN109447223A

Abstract

The invention discloses a method for enhancing the reflected power of a label, which comprises the step of determining the impedance value Z of the absorption state of a label chip_absorb(ii) a Setting the antenna impedance Z_ant＝Z_absorbWherein Z_absorbIs the impedance value Z of the label chip in the absorption state_absorbThe impedance of the chip modulation circuit is changed, so that the reflected power P_reReaching a first value; thereby determining the reflecting state impedance value Z of the tag chip_reflect(ii) a Impedance Z of antenna_antIs set to the maximum value Z_{ant_max}So that the reflected power P_reThe maximum reflected power is reached; at the antenna impedance Z_ant＝Z_absorbIn the case of x, calculating the absolute values of the sensitivity loss and the reflection coefficient difference; at the antenna impedance Z_ant＝Z_{ant_max}In the case of (2), calculating the sensitivity loss and the absolute value of the reflection coefficient difference; and carrying out compromise between the maximum reflected power and the minimum sensitivity loss value so as to determine the reflected power of the tag chip.

Description

Method for enhancing reflected power of ultrahigh frequency RFID (radio frequency identification) tag

Technical Field

The invention relates to the field of ultrahigh frequency RFID (radio frequency identification) tags, in particular to a method capable of enhancing the reflected power of an ultrahigh frequency RFID tag.

Background

The RFID is a non-contact automatic identification technology, which automatically identifies a target object and obtains related data through a radio frequency signal, does not need manual intervention in identification work, and can work in various severe environments. The RFID technology can identify high-speed moving objects and can identify a plurality of electronic tags simultaneously, and the operation is quick and convenient. The ultra-high frequency RFID technology is widely applied to logistics, manufacturing, medical treatment, transportation, retail sale, national defense and the like. The ultra high frequency RFID is divided into a tag and a reader. The label is composed of a label antenna and a label chip.

The reflected power of the ultrahigh frequency tag is determined by the tag antenna and the tag chip together. Therefore, how to obtain higher reflected power of the tag and optimize other performances of the tag is a long-term pursuit goal in the field of ultrahigh frequency tags.

Disclosure of Invention

The invention provides a method for enhancing the reflected power of an ultrahigh frequency RFID (radio frequency identification) tag, which comprises the following steps:

determining an absorption state impedance value Z of a tag chip_absorb；

Setting the antenna impedance Z_ant＝Z_absorbWherein Z_absorbIs the impedance value Z of the label chip in the absorption state_absorbThe impedance of the chip modulation circuit is changed, so that the reflected power P_reReaching a first value; thereby determining the reflecting state impedance value Z of the tag chip_reflect；

Impedance Z of antenna_antIs set to the maximum value Z_{ant_max}So that the reflected power P_reThe maximum reflected power is reached;

at the antenna impedance Z_ant＝Z_absorbIn the case of x, calculating the absolute values of the sensitivity loss and the reflection coefficient difference;

at the antenna impedance Z_ant＝Z_{ant_max}In the case of (2), calculating the sensitivity loss and the absolute value of the reflection coefficient difference; and

and (4) carrying out compromise between the maximum reflected power and the minimum sensitivity loss value so as to determine the reflected power of the tag chip.

In one embodiment of the invention, when the power P is reflected_reWhen the first value is reached, the absolute value of the difference between the reflection coefficients is greater than 0.5 and less than 1.

In one embodiment of the invention, when the power P is reflected_reWhen the first value is reached, the absolute value of the difference between the reflection coefficients is 0.8.

In one embodiment of the invention, the compromise between maximum reflected power and minimum sensitivity loss value comprises: on the contour line where the sensitivity loss is the first threshold, a point where the reflection coefficient is maximum is found, and the antenna impedance is set to an impedance value corresponding to the reflection coefficient maximum.

In an embodiment of the invention, the changing the impedance of the chip modulation circuit includes changing an equivalent parallel capacitance and an equivalent parallel resistance value of the tag modulation circuit, so that the impedance value Z of the tag chip in the reflection state_reflectA change occurs.

In one embodiment of the invention, the impedance Z at the antenna_ant＝Z_{ant_max}When the temperature of the water is higher than the set temperature,

let Z_absorbZ1_ re + jz1_ im, where z1_ re isA real part, z1_ im being an imaginary part;

Z_reflectz2_ re + jz2_ im, where z2_ re is the real part and z2_ im is the imaginary part;

then Z_{ant_max＝}Zant _ re + jZant _ im is determined by the following formula:

Zant_re＝z1_re*z2_re*((z1_re+z2_re)^2+(z1_im-z2_im)^2))^(1/2)/(z1_re+z2_re)；

Zant_im＝-(z1_re*z2_im+z2_re*z1_im)/(z1_re+z2_re)；

where the symbol ^ represents the power exponent, e.g., z2_ im ^2 represents z2_ im to the power of 2.

In one embodiment of the invention, the impedance Z at the antenna_ant＝Z_{ant_max}In the case of (a) in (b),

loss of sensitivity M_lossComprises the following steps:

the absolute value of the reflection coefficient difference | Δ Γ | is:

in one embodiment of the invention, the impedance Z at the antenna_ant＝Z_absorbIn the case of the above-mentioned example,

loss of sensitivity M_lossComprises the following steps:

M_loss＝0；

the absolute value of the reflection coefficient difference | Δ Γ | is:

in one embodiment of the invention, an absorption state impedance value Z of the tag chip is determined_absorbThe method comprises the steps of switching off a tag chip modulation circuit switch to obtain integral impedance which is the impedance Z of the chip in the absorption state_absorb。

The method for enhancing the reflected power of the ultrahigh frequency RFID tag disclosed by the invention can maximally enhance the reflected power of the ultrahigh frequency RFID tag according to actual requirements under the condition of meeting the sensitivity requirement.

Drawings

To further clarify the above and other advantages and features of embodiments of the present invention, a more particular description of embodiments of the invention will be rendered by reference to the appended drawings. It is appreciated that these drawings depict only typical embodiments of the invention and are therefore not to be considered limiting of its scope. In the drawings, the same or corresponding parts will be denoted by the same or similar reference numerals for clarity.

Fig. 1 shows a flow diagram of a method of enhancing reflected power of an uhf RFID tag, according to one embodiment of the present invention.

Fig. 2 shows a schematic diagram of the absorption state of the tag chip.

Fig. 3 shows a schematic diagram of the reflection state of the tag chip.

Fig. 4 is a contour plot of absolute values of the difference in reflection coefficients of the tags.

Fig. 5 is a contour plot of the sensitivity loss of the tag.

Fig. 6 is a contour plot of the absolute value of the difference in the reflection coefficients of the tag and the loss in sensitivity of the tag.

Detailed Description

In the following description, the invention is described with reference to various embodiments. One skilled in the relevant art will recognize, however, that the embodiments may be practiced without one or more of the specific details, or with other alternative and/or additional methods, materials, or components. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of embodiments of the invention. Similarly, for purposes of explanation, specific numbers, materials and configurations are set forth in order to provide a thorough understanding of the embodiments of the invention. However, the invention may be practiced without specific details. Further, it should be understood that the embodiments shown in the figures are illustrative representations and are not necessarily drawn to scale.

Reference in the specification to "one embodiment" or "the embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. The appearances of the phrase "in one embodiment" in various places in the specification are not necessarily all referring to the same embodiment.

During the operation of the tag, the sensitivity of the tag and the reflected power of the tag are important parameters for measuring the performance of the tag. The invention provides a method for enhancing the reflected power of an ultrahigh frequency RFID (radio frequency identification) tag, which can adjust the sensitivity of the tag and the reflected power of the tag to optimal values, so that the performance of the tag is greatly improved.

First, the operation principle of the method for enhancing the reflected power of the tag disclosed by the present invention is described.

The frequency band has an influence on chip impedance, antenna impedance, sensitivity gradient maps, sensitivity contour lines, and the like. For RFID chips and antennas, essentially all electrical parameters are a function of frequency. However, the RFID chip and antenna typically operate in one frequency band, and the following calculations assume that the tag is in the operating frequency band, and therefore ignore this parameter of operating frequency.

In the working process of the tag, the impedance value Z of the tag chip in the reflection state_reflectAnd an absorption state impedance value Z_absorbTo switch between.

Reflected power P of tag_reComprises the following steps:

where P is_tIs the radio frequency power value received by the tag antenna, | DeltaGamma | is the absolute value of the reflection coefficient difference, Z_antIs the antenna impedance, Z_reflectIs the impedance value, Z, of the tag chip in the reflection state_absorbIs the impedance value of the absorption state of the tag chip, wherein the antenna impedance Z_antImpedance value Z of reflection state of tag chip_reflectAnd the impedance value Z of the absorption state of the tag chip_absorbIs a complex number, a symbol^*Representing the conjugate impedance of the complex impedance.

Impedance value Z in reflection state_reflectAnd an absorption state impedance value Z_absorbIn the case of certainty, P_reThe condition for reaching the maximum reflected power is the antenna impedance Z_ant＝Z_{ant_max}。

The loss in sensitivity of the tag is:

the minimum sensitivity loss condition is the antenna impedance Z_ant＝Z_absorb ^*。

Therefore, for the ultrahigh frequency RFID tag, the maximum reflected power condition and the minimum sensitivity loss condition are different, and a compromise needs to be made according to actual requirements. It is known that the minimum sensitivity loss condition is the maximum sensitivity condition of the tag.

According to the above implementation principle, the embodiment of the invention provides a method for enhancing the reflected power of the ultrahigh frequency RFID tag. Fig. 1 shows a flow diagram of a method of enhancing reflected power of an uhf RFID tag, according to one embodiment of the present invention. The method comprises three steps.

In step 101, the impedance value Z is in the absorption state_absorbIn the determined case, the antenna impedance Z is set_ant＝Z_absorbChanging the impedance of the chip modulation circuit to reflect power P_reReaching a larger value. In one embodiment of the present invention, the typical value is about 0.8. In other embodiments of the present invention, the value of | Δ Γ | should be greater than 0.5, less than 1.

Step 102, impedance value Z in reflection state_reflectAnd an absorption state impedance value Z_absorbUnder certain conditions, by setting the antenna impedance Z_ant＝Z_{ant_max}Value of obtaining maximum reflected power P_{re_max}。

Step 103, respectively calculating sensitivity loss M under the condition of maximum reflected power and the condition of minimum sensitivity loss_lossAnd the absolute value of the reflection coefficient difference | Δ Γ |. Adjusting the impedance value of the antenna to the maximum value according to actual requirementsA compromise is made between reflected power and minimum sensitivity loss value.

The following is a detailed description of the three steps.

In step 101, the tag chip absorbs the state impedance value Z_absorbDetermined by the chip as a whole. Closing the label chip modulation circuit to obtain the integral impedance which is the chip absorption state impedance Z_absorb. Impedance value Z of label chip in reflection state_reflectDetermined by the chip as a whole. Connecting a tag chip modulation circuit switch to obtain integral impedance which is the impedance Z of the chip in a reflection state_reflect。

In step 101, the antenna impedance Z_ant＝Z_absorbConjugate matching, so that the power reaching the tag antenna is transmitted into the tag chip maximally, that is, the tag has the farthest reading distance, and step 101 makes the tag have stronger reflected power under the condition of having the farthest reading distance.

At this time, the reflection coefficient in the absorption state is 0, and the label has the highest value of sensitivity.

Z_ant＝Z_absorb ^*Conjugate match, then reflected power P_reCan be simplified into:

when the modulation circuit of the tag is adjusted, the equivalent parallel capacitance and the equivalent parallel resistance value of the tag modulation circuit are changed. So that the impedance value Z of the tag chip in the reflection state_reflectA change occurs.

In the process of adjusting the modulation circuit of the tag, because the absorption state impedance value is obtained when the modulation circuit switch is switched off, the absorption state impedance value Z of the tag chip_absorbSubstantially unchanged.

Thus, in adjusting the modulation circuit of the tag, Z_ant＝Z_absorb ^*Does not change and the reflected power P_reA change occurs. Thereby making the adjustment process simple and effective.

In step 102, at the targetImpedance value Z of chip in reflection state_reflectAnd the impedance value Z of the absorption state of the tag chip_absorbIn the determined case, Z_ant＝Z_{ant_max}When is, P_reA maximum reflected power is reached.

Impedance value Z of label chip in reflection state_reflectAnd the impedance value Z of the absorption state of the tag chip_absorbTo a plurality of numbers, let:

Z_absorbz1_ re + jz1_ im, where z1_ re is the real part, z1_ im is the imaginary part,

Z_reflectz2_ re + jz2_ im, where z2_ re is the real part, z2_ im is the imaginary part,

Zant_re＝z1_re*z2_re*((z1_re+z2_re)^2+(z1_im-z2_im)^2))^(1/2)/(z1_re+z2_re)；

Zant_im＝-(z1_re*z2_im+z2_re*z1_im)/(z1_re+z2_re)；

Step 102 makes the tag antenna and the chip non-conjugate matched, so that the reflected power of the tag is strongest.

Note that step 102 results in a reflection coefficient for the absorption state of the chip that is not 0.

The sensitivity loss is:

M_loss＝-10log(1-|Γ_{absorb_max}|²)

step 103, respectively calculating sensitivity loss M under the condition of maximum reflected power and the condition of minimum sensitivity loss_lossAnd the absolute value of the reflection coefficient difference | Δ Γ |. The impedance value of the antenna is adjusted according to actual requirements, and compromise can be made between the maximum reflection power value and the minimum sensitivity loss value. For example, the tag sensitivity Loss needs to be less than the threshold Loss 1. In step 103, on the contour line with the tag sensitivity Loss of threshold Loss of Loss1, the maximum value of the reflection coefficient is found, andthe antenna impedance is set to an impedance value corresponding to the maximum value of the reflection coefficient.

Wherein the maximum reflected power condition is Z_ant＝Z_{ant_max}The minimum sensitivity loss condition is Z_ant＝Z_absorb*。

The sensitivity loss under the maximum reflected power condition is:

absolute value of difference of reflection coefficients

At minimum loss of sensitivity

The sensitivity loss is:

M_loss＝0

absolute value of difference of reflection coefficients

Where a typical practical requirement is that the tag sensitivity Loss needs to be less than the threshold Loss of pass 1. The compromise is to find the maximum reflection coefficient on the contour where the tag sensitivity Loss is the threshold Loss of Loss1 and set the antenna impedance to that value. The effect of the implementation is that the reflected power takes the maximum value on the contour line with equal tag sensitivity loss.

In an embodiment of the present invention, step 101 enables the tag to operate in a conjugate matching situation, with a considerable reflected power. Step 102 is to adjust the impedance of the tag antenna to make the tag non-conjugate match, so that the reflected power is strongest. And 103, carrying out compromise adjustment according to actual requirements. In a word, the embodiment of the invention realizes the enhancement of the reflected power of the ultrahigh frequency RFID label, and has advancement.

The process of the method for enhancing the reflected power of the UHF RFID tag according to the present invention is described in detail below with reference to specific tag antennas.

Fig. 2 shows a schematic diagram of the absorption state of the tag chip. As shown in fig. 2, a1 is the equivalent impedance value of other circuits of the tag chip, a2 is the equivalent parallel resistance value of the modulation circuit, a3 is the equivalent parallel capacitance value of the modulation circuit, a4 is the switch in the off state, and a5 is the RF port. Here, when the a4 switch is turned off, the impedance value viewed from the a5 port is Z_absorb0.61pF 4000 ohm. At frequency point 920MHz, there is Z_absorb＝20-j282ohm。

Next, step 101 is performed at Z_absorbIn the case of confirmation, set Z_ant＝Z_absorb ^*And changing the impedance of the chip modulation circuit. Therefore, Z is set at frequency point 920MHz_ant＝Z _absorb ^*20+ j282 ohm. I.e., setting the position of the five-pointed star c1 in fig. 4. Fig. 3 is a schematic diagram of the reflection state of the tag chip, and as shown in fig. 3, b1 is the equivalent impedance value of other circuits of the tag chip, b2 is the equivalent parallel resistance value of the modulation circuit, b3 is the equivalent parallel capacitance value of the modulation circuit, b4 is the switch in the on state, and b5 is the RF port. After the b4 switch is connected, the equivalent parallel resistance value of the modulation circuit and the equivalent parallel capacitance value of the modulation circuit are adjusted, so that the reflection is strong enough.

Here, the equivalent parallel resistance value of the modulation circuit is equal to 4000ohm, and the equivalent parallel capacitance value of the modulation circuit is equal to 0.23 pF. Adjusting the equivalent impedance value of the modulation circuit, i.e. adjusting the position of the square c2 in fig. 4, in the process of which the five-pointed star c1, Z in fig. 4_absorbThe value is not changed, let Z_reflect0.84pF 2000 ohm. At frequency point 920MHz, Z_reflect＝21-j203.8ohm。

In this case, according to

The absolute value of the reflection coefficient difference | Δ Γ | > is 0.89, and the reflected power P is obtained_re＝0.7921*P_t. At this time, the reflection coefficient in the absorption state is 0, and the label has the highest value of sensitivity. Step 101 is completed.

Next, step 102 is performed.

According to the following formula:

Zant_re＝(z1_re*z2_re*((z1_re+z2_re)^2+(z1_im-z2_im)^2))^(1/2)/(z1_re+z2_re)；

Zant_im＝-(z1_re*z2_im+z2_re*z1_im)/(z1_re+z2_re)；

can obtain Z_{ant_max}44.2+ j243.9, where the absolute value of the difference between the reflection coefficients is 1.21, and the maximum reflection power P_{re_max}＝1.4641*P_t

Fig. 4 is a contour plot of absolute values of the difference in reflection coefficients of the tags. The x axis is an antenna impedance real part, the y axis is an antenna impedance imaginary part, and the antenna impedance is traversed in a set range. Wherein, the five-pointed star c1 is the impedance conjugate Z of the chip in the absorption state_absorb ^*The square c2 is the conjugate Z of the chip reflection state impedance value_reflect ^*Triangle c3 is the calculated maximum reflected impedance value Z_{ant_max}. The contour line c4 is a contour line of the reflection coefficient difference absolute value | Δ Γ |. The absolute value of the reflection coefficient difference is a function of the chip impedance and the chip impedance. After the chip impedance is determined, the antenna impedance has an optimum position, i.e., the conjugate matching point, at which the reflection is zero. The contour line c4 is a circle surrounding the conjugate matching point, and is a point where the absolute values of the reflection coefficient differences are equal, and the contour line c4 is resolved by setting the absolute values of the reflection coefficient differences. The larger the circle, the stronger the reflection. The impedance seen at a5 in FIG. 2 is the conjugate of the five-pointed star c1, and the impedance seen at b5 in FIG. 3 is the conjugate of the square c 2.

It can be seen that the match state Z_ant＝Z_absorb ^*If the antenna impedance is set to the maximum reflected impedance value Z_ant＝Z_{ant_max}I.e. the antenna is arranged in the position of triangle c3, the reflected power is at the location of the centre of the contour, i.e. at the maximum, over the whole graph.

After step 102 is completed, step 103 is performed.

Fig. 5 is a contour plot of the sensitivity loss of the tag. Wherein the five-pointed star d1 is the impedance conjugate Z of the chip in the absorption state_absorb ^*The square d2 is the conjugate Z of the chip reflection state impedance value_reflect ^*Triangle d3 is the calculated maximum reflected impedance value Z_{ant_max}. Contour d4 is the loss of sensitivity M of the tag_lossThe contour lines of (a). The signature sensitivity loss is a function of chip impedance and chip impedance. After the chip impedance is determined, there is an optimum position for the antenna impedance, at which point the sensitivity loss is zero. The contour d4 is a circle surrounding a point where the sensitivity loss is zero, and is a point where the sensitivity loss is equal, and the contour d4 can be analyzed by setting the value of the sensitivity loss. As can be seen from FIG. 5, the maximum reflected power condition Z_ant＝Z_{ant_max}I.e. at the position of triangle d3, M_loss1.98dB, | Δ Γ | 1.21; minimum loss of sensitivity condition, Z_ant＝Z_absorb ^*I.e. in the position of the five-pointed star d1, M_loss0dB, | Δ Γ |, 0.89. Therefore, a compromise between the maximum reflected power and the maximum sensitivity can be made accordingly.

For example, in this embodiment, the sensitivity Loss threshold is set to lose 1 ═ 0.5dB, so that the antenna impedance can be adjusted to maximize the reflection power value on the 0.5dB sensitivity Loss contour.

Fig. 6 is a contour plot of the absolute value of the difference in the reflection coefficients of the tag and the loss in sensitivity of the tag. Wherein, the five-pointed star e1 is the impedance conjugate Z of the chip absorption state_absorb ^*The square e2 is the conjugate Z of the chip reflection state impedance value_reflect ^*Triangle e3 is the calculated maximum reflected impedance value Z_{ant_max}. Solid line contour e4 is the tag sensitivity loss M_lossThe contour lines of (a). A dashed line contour e5 is a contour of the absolute value of the tag reflection coefficient difference | Δ Γ |. Diamond e6 is the point of maximum reflected power on the Loss of sensitivity contour for the less 1-0.5 dB tag. The value of diamond e6 is Zant 34.36+ j278.8 ohm.

It can be seen from fig. 6 that the sensitivity requirement can be met at all points within the 0.5dB tag sensitivity Loss contour for Loss1, but the absolute value of the difference in reflectance is different at points within the 0.5dB tag sensitivity Loss contour for Loss1, with the absolute value of the difference in reflectance varying from 0.6122 to 1.112. According to step 103, the antenna impedance value should be diamond e6 with Zant being 34.36+ j278.8 ohm.

Without the method of the present disclosure, the antenna impedance design would randomly fall within the 0.5dB tag sensitivity Loss contour for Loss of Loss 1. If the lowest point and the highest point of the absolute value of the difference of the reflection coefficients are compared, the reflection power of the ultrahigh frequency RFID tag is improved by 20 log10(1.112/0.6122) to 5.18dB by the embodiment of the invention.

In some embodiments of the invention, the methods disclosed herein may be implemented by hardware means, software means, or any combination thereof. Examples of hardware devices may include processors, microprocessors, circuits, circuit elements (e.g., transistors, resistors, capacitors, inductors, and so forth), integrated circuits, Application Specific Integrated Circuits (ASIC), Programmable Logic Devices (PLD), Digital Signal Processors (DSP), Field Programmable Gate Array (FPGA), logic gates, registers, semiconductor device, chips, microchips, chip sets, and so forth.

Examples of software may include software components, programs, applications, computer programs, application programs, system programs, machine programs, operating system software, middleware, firmware, software modules, routines, subroutines, functions, methods, procedures, software interfaces, Application Program Interfaces (API), instruction sets, computing code, computer code, code segments, computer code segments, words, values, symbols, or any combination thereof.

Some embodiments may be implemented, for example, using a machine-readable storage medium or article. A storage medium may store an instruction or a set of instructions that, when executed by a machine, may cause the machine to perform a method and/or operations in accordance with the embodiments. Such a machine may include, for example, any suitable processing platform, computing device, processing device, computing system, processing system, computer, processor, or the like, and may be implemented using any suitable combination of hardware and/or software.

Embodiments may include a storage medium or a machine-readable article. For example, any suitable type of memory unit, memory device, memory article, memory medium, storage device, storage article, storage medium and/or storage unit may be included, such as, for example, memory, removable or non-removable media, erasable or non-erasable media, writeable or re-writeable media, digital or analog media, hard disk, floppy disk, compact disk read Only memory (CD-ROM), compact disk recordable (CD-R), compact disk Rewriteable (CD-RW), optical disk, magnetic media, magneto-optical media, removable memory cards or disks, various types of Digital Versatile Disk (DVD), a tape, a cassette, or the like. The instructions may include any suitable type of code, such as source code, assembly code, interpreted code, executable code, static code, dynamic code, encrypted code, and the like, implemented using any suitable high-level, low-level, object-oriented, visual, compiled and/or interpreted programming language.

While various embodiments of the present invention have been described above, it should be understood that they have been presented by way of example only, and not limitation. It will be apparent to persons skilled in the relevant art that various combinations, modifications, and changes can be made thereto without departing from the spirit and scope of the invention. Thus, the breadth and scope of the present invention disclosed herein should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.

Claims

1. A method of enhancing tag reflected power, comprising:

determining an absorption state impedance value Z of a tag chip_absorb；

Setting the antenna impedance Z_ant＝Z_absorb ^*Wherein Z is_absorb ^*Is the impedance value Z of the absorption state of the tag chip_absorbThe impedance of the chip modulation circuit is changed, so that the reflected power p_reReaching a first value; thereby determining the reflecting state impedance value Z of the tag chip_reflect；

Impedance Z of antenna_antIs set to the maximum value Z_{ant_max}So that the reflected power p_reThe maximum reflected power is reached; when the reflected power p_reWhen the absolute value of the reflection coefficient difference reaches a first value, the absolute value of the reflection coefficient difference is more than 0.5 and less than 1;

at the antenna impedance Z_ant＝Z_absorb ^*In the case of (2), calculating the sensitivity loss and the absolute value of the reflection coefficient difference;

carrying out compromise between the maximum reflected power and the minimum sensitivity loss value so as to determine the reflected power of the tag chip;

at the antenna impedance Z_ant＝Z_{ant_max}When is, let Z_absorbZ1_ re + jz1_ im, where z1_ re is the real part and z1_ im is the imaginary part; z_reflectZ2_ re + jz2_ im, where z2_ re is the real part and z2_ im is the imaginary part; then Z_{ant_max}Zant _ re + jZant _ im is determined by the following formula:

Zant_re＝z1_re*z2_re*((z1_re+z2_re)^2+(z1_im-z2_im)^2))^(1/2)/(z1_re+z2_re)；

Zant_im＝-(z1_re*z2_im+z2_re*z1_im)/(z1_re+z2_re)；

wherein the symbol ^ represents the power exponent, z2_ im ^2 represents z2_ im to the power of 2;

the impedance Z at the antenna_ant＝Z_{ant_max}In the case of (2), calculating the absolute values of the sensitivity loss and the reflection coefficient difference includes:

loss of sensitivity M_lossComprises the following steps:

the absolute value of the reflection coefficient difference | Δ Γ | is:

the impedance Z at the antenna_ant＝Z_absorb ^*In the case of (2), calculating the absolute values of the sensitivity loss and the reflection coefficient difference includes:

loss of sensitivity M_lossComprises the following steps:

M_loss＝0；

the absolute value of the reflection coefficient difference | Δ Γ | is:

2. the method of enhancing tag reflected power of claim 1, wherein the tradeoff between maximum reflected power and minimum sensitivity loss value comprises: on the contour line where the sensitivity loss is the first threshold, a point where the reflection coefficient is maximum is found, and the antenna impedance is set to an impedance value corresponding to the reflection coefficient maximum.

3. The method of claim 1, wherein the varying the chip modulation circuit impedance comprises varying an equivalent parallel capacitance and an equivalent parallel resistance of the tag modulation circuit, such that the tag chip reflection state impedance value Z_reflectA change occurs.

4. The method of enhancing tag reflected power of claim 1, wherein the absorption state impedance value Z of the tag chip is determined_absorbThe method comprises the steps of switching off a tag chip modulation circuit switch to obtain integral impedance which is the impedance Z of the chip in the absorption state_absorb。

5. A system for enhancing reflected power of a tag, comprising:

a memory storing machine executable instructions; and

a processor for performing the method of any one of claims 1 to 4.