A method for estimating tag count using the quality factor of reader antenna and coupling system

Abstract

This invention relates to a method for estimating the number of tags using the quality factor of a reader antenna and a coupling system, belonging to the field of radio frequency identification (RFID). The method includes: measuring the correspondence between different tag quantities and the quality factor of the coupling system under a certain reader transmission power; measuring the quality factor of the coupling system corresponding to the number of tags to be inventoried; then, estimating the number of tags to be inventoried based on the correspondence between the tag quantity and the coupling system quality factor; setting an initial Q value for the anti-collision algorithm based on the estimated number of tags; optimizing the anti-collision algorithm; and realizing tag inventory. This invention solves the problem of improper initial Q value setting in the anti-collision algorithm, effectively improving the reading efficiency of high-frequency RFID systems.

Description

Technical Field

[0001] This invention belongs to the field of radio frequency identification, specifically relating to a method for estimating the number of tags using the quality factor of the reader antenna and coupling system. Background Technology

[0002] High-frequency RFID systems have advantages that other frequency band RFID systems do not have due to their working frequency band and magnetic field coupling principle. These advantages include insensitivity to liquids, controllable reading range, low misreading, and accurate reading of densely stacked RFID tags. As a result, they are widely used in industries such as document management and smart warehousing.

[0003] However, in multi-tag recognition applications, simultaneous responses from multiple tags can lead to collisions. Taking the ISO 18000-3 protocol Mode 3 as an example, this protocol employs the Dynamic Frame Slotted Algorithm (DFSA) based on dynamic Q-values. It improves inventory efficiency by dynamically adjusting the number of slots, and the number of dynamic slots is highly dependent on the initial Q-value. In the DFSA algorithm, the initial Q-value is related to the number of tags; generally, the tag inventory efficiency is highest when the number of tags equals 2Q. If the initial Q-value of the anti-collision algorithm is set too high, it will result in too many idle slots, reducing inventory efficiency; if the initial Q-value is set too low, it will increase the collision probability, resulting in too many collision slots and reducing inventory efficiency.

[0004] Therefore, there is an urgent need for a method to optimize the initial Q value in anti-collision algorithms, improve time slot utilization and tag inventory efficiency, and adapt to the needs of RFID applications. This invention is precisely designed to meet this practical need. Summary of the Invention

[0005] (a) Technical problems to be solved

[0006] The technical problem to be solved by this invention is how to provide a method for estimating the number of tags using the quality factor of the reader antenna and coupling system, so as to solve the problem of setting the initial Q value in the anti-collision algorithm.

[0007] (II) Technical Solution

[0008] To address the aforementioned technical problems, this invention proposes a method for estimating the number of tags using the quality factor of a reader antenna and coupling system. This method includes the following steps:

[0009] S1. Coupled System Quality Factor Measurement: Measure the correspondence between different numbers of tags in the coupled system and the quality factor of the coupled system;

[0010] S2. Estimation of the number of tags to be inventoried: First, measure the quality factor of the coupling system corresponding to the tags to be inventoried, and then estimate the number of tags N to be inventoried based on the correspondence between the quality factor of the coupling system and the number of tags.

[0011] S3. Tag Inventory: Based on the estimated number of tags N, estimate the initial Q value of the anti-collision algorithm.

[0012] Furthermore, in step S3, Q = round(log2N).

[0013] Furthermore, the coupling system includes a high-frequency RFID tag and a reader, and the communication between the high-frequency RFID tag and the reader is achieved through magnetic field coupling of the antenna coils of both parties.

[0014] Furthermore, the tag enters the electromagnetic field of the reader, and the tag coil enters a resonant state, thereby coupling and obtaining energy to activate and operate the tag, while extracting the clock signal from the carrier signal of the reader antenna.

[0015] Furthermore, the high-frequency RFID tag adopts a load modulation method based on a subcarrier. The tag antenna is coupled to the reader antenna, which is equivalent to the load of the reader antenna. Switching the load resistor on the tag antenna changes the load of the reader antenna, thereby changing the voltage on the reader antenna and realizing data transmission. When these tags are densely stacked, a coupling relationship is formed between each tag and the antenna, and the quality factor of the coupling system measured at the reader changes.

[0016] Further, in step S1, the reader uses the analog-to-digital converter (ADC) module in the reader to collect the voltage value of the received signal after being divided by a voltage divider resistor, and compares it with the voltage divider resistor converted by the ADC module in the reader to obtain the instantaneous power of the reader. Then, the instantaneous power of the received signal is integrated over time to obtain the received energy W of the reader. R The known emission energy (W) of the reader / writer T With the reader's received energy W R The difference is the energy consumed by the circuit (W). C The quality factor A of the coupled system is calculated as follows:

[0017]

[0018] In the formula, W R W represents the energy stored in the circuit at resonance, i.e., the energy received by the reader. T Indicates the energy emitted by the reader, W C This indicates the energy consumed by the circuit.

[0019] Furthermore, the number of tags is negatively correlated with the quality factor of the coupled system.

[0020] Further, step S1 specifically includes: under a certain reader antenna transmission power, testing the quality factor A of the coupling system corresponding to different numbers of tags, and constructing a comparison table of the number of tags and the quality factor A of the coupling system under a certain reader antenna transmission power.

[0021] Further, step S2 specifically includes: determining the reader antenna transmit power W. T Next, the quality factor A of the coupling system corresponding to the tag to be inventoried is measured, and the number N of tags to be inventoried is estimated based on the quality factor A of the coupling system of the reader antenna and the lookup table in S1.

[0022] Furthermore, the reader operates in ISO 18000-3 protocol Mode 3 mode.

[0023] (III) Beneficial Effects

[0024] This invention proposes a method for estimating the number of tags using the quality factor of a reader antenna and a coupling system. For simplicity, the reader antenna and tag coupling system is hereinafter referred to as the coupling system. The method includes: (1) Measurement of the coupling system quality factor. Under a certain reader transmission power, the correspondence between different tag numbers and the coupling system quality factor is measured; (2) Estimation of the number of tags to be inventoried. First, the quality factor of the coupling system corresponding to the number of tags to be inventoried is measured. Then, based on the correspondence between the number of tags and the coupling system quality factor, the number of tags to be inventoried is estimated; (3) Tag inventory. Based on the estimated number of tags, an initial Q value for the anti-collision algorithm is set, the anti-collision algorithm is optimized, and tag inventory is achieved.

[0025] The method proposed in this invention pre-collects the quality factors of the coupling system corresponding to different numbers of tags under a certain reader transmission power, and designs an initial Q-value prediction for a high-frequency RFID system anti-collision algorithm based on the prior value. This can solve the problem of improper initial Q-value setting of the anti-collision algorithm and effectively improve the reading efficiency of the high-frequency RFID system.

[0026] This invention estimates the approximate range of the number of tags to be inventoried by coupling the system quality factor, thereby setting an appropriate initial Q value for the anti-collision algorithm and optimizing the anti-collision algorithm, which will play an important role in RFID applications. Attached Figure Description

[0027] Figure 1 This is a schematic diagram illustrating the principle of a method for estimating the number of tags using the quality factor of a reader antenna and coupling system, where L represents the inductance of the antenna coil; R... L Z represents the antenna resistance; Z represents the equivalent impedance matching network; C represents the equivalent capacitance of the chip capacitance and coil capacitance.

[0028] Figure 2 This is a flowchart of a method for estimating the number of tags using the quality factor of the reader antenna and coupling system. Detailed Implementation

[0029] To make the objectives, contents, and advantages of the present invention clearer, the specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples.

[0030] This invention relates to the field of radio frequency identification, specifically to a method for estimating the number of RFID tags and optimizing tag inventory efficiency using a coupling quality factor.

[0031] This invention discloses a method for estimating the number of tags using the quality factor of the reader antenna coupled with the tag. For simplicity, the reader antenna and tag coupling system is hereinafter referred to as the coupling system. The method includes: (1) Measurement of the quality factor of the coupling system. Under a certain reader transmission power, the correspondence between different tag numbers and the quality factor of the coupling system is measured; (2) Estimation of the number of tags to be inventoried. First, the quality factor of the coupling system corresponding to the number of tags to be inventoried is measured, and then the number of tags to be inventoried is estimated based on the correspondence between the number of tags and the quality factor of the coupling system; (3) Tag inventory. Based on the estimated number of tags, the initial Q value of the anti-collision algorithm is set, the anti-collision algorithm is optimized, and the tag inventory is realized.

[0032] The method proposed in this invention pre-collects the quality factors of the coupling system corresponding to different numbers of tags under a certain reader transmission power, and designs an initial Q-value prediction for a high-frequency RFID system anti-collision algorithm based on the prior value. This can solve the problem of improper initial Q-value setting of the anti-collision algorithm and effectively improve the reading efficiency of the high-frequency RFID system.

[0033] This invention proposes a method for estimating tag quantity using the quality factor of the reader antenna coupled with the tag. This method combines the anti-collision process with the measurement of the quality factor of the coupling system, effectively ensuring the efficiency of tag inventory. The method includes:

[0034] S1. Measurement of the quality factor of the coupled system. This involves measuring the correspondence between different numbers of tags in the coupled system and the quality factor of the coupled system.

[0035] S2. Estimation of the number of tags to be inventoried. First, measure the quality factor of the coupling system corresponding to the tags to be inventoried. Then, based on the correspondence between the quality factor of the coupling system and the number of tags, estimate the number N of tags to be inventoried.

[0036] S3. Tag Inventory. Based on the estimated number of tags N, estimate the initial Q value of the anti-collision algorithm, where Q = round(log2N), and implement tag inventory based on the anti-collision optimization algorithm.

[0037] This invention estimates the approximate range of the number of tags to be inventoried by coupling the system quality factor, thereby setting an appropriate initial Q value for the anti-collision algorithm and optimizing the anti-collision algorithm, which will play an important role in RFID applications.

[0038] Example 1:

[0039] The following uses the ISO 18000-3 protocol Mode 3 as an example to illustrate the specific implementation of the present invention, but it is not intended to limit the specific implementation method.

[0040] Figure 1 This is a schematic diagram illustrating the principle of a method for estimating the number of tags by utilizing the quality factor of the coupling between the reader antenna and the tag. For example... Figure 1 As shown, the coupling system includes a high-frequency RFID tag and a reader. Communication between the high-frequency RFID tag and the reader is achieved through magnetic field coupling of their respective antenna coils, where the inductance of the antenna coil is L and the resistance of the antenna is R. L The equivalent impedance of the matching network and back-end chip is Z, and the mutual inductance between the reader and tag coils, and between different tag coils, is denoted by M. When a tag enters the electromagnetic field of the reader, the tag coil enters a resonant state, thereby coupling and obtaining energy to activate and operate the tag. Simultaneously, a clock signal is extracted from the carrier signal of the reader antenna. High-frequency RFID tags employ a load modulation method based on a subcarrier. The tag antenna is coupled to the reader antenna, which can be considered equivalent to the load of the reader antenna. Switching the load resistor on the tag antenna changes the load of the reader antenna, thereby changing the voltage on the reader antenna and enabling data transmission. When these tags are densely stacked, a coupling relationship is formed between each tag and the antenna, and the quality factor of the coupling system measured at the reader will change.

[0041] Figure 2 This is a flowchart illustrating a method for estimating the number of tags by utilizing the quality factor of the coupling between the reader antenna and the tag. (Example:) Figure 2 As shown, the specific implementation process of this method is as follows.

[0042] S1. Measurement of the quality factor of the coupling system. The instantaneous received power of the reader is obtained by combining the voltage value of the received signal after being divided by a voltage divider resistor with the voltage value of the voltage divider resistor converted by the ADC module in the reader. Then, integrating the instantaneous received power over time yields the received energy W of the reader. R The known emission energy (W) of the reader / writer T With the reader's received energy W R The difference is the energy consumed by the circuit (W). C The quality factor A of the coupled system is calculated as follows:

[0043]

[0044] In the formula, W R W represents the energy stored in the circuit at resonance, i.e., the energy received by the reader. T Indicates the energy emitted by the reader, W C This indicates the energy consumed by the circuit.

[0045] At the reader's transmit power W T With the number of tags remaining constant, the more tags there are, the greater the energy loss (W) will be. C The decrease in the coupling system quality factor A indicates that the number of tags is negatively correlated with the coupling system quality factor.

[0046] Based on the negative correlation between the number of tags and the quality factor of the coupling system, under a certain reader antenna transmit power, the quality factor A of the coupling system corresponding to different numbers of tags, such as N, is tested. 11 The quality factor of the coupled system corresponding to each label is A. 11 N 12 The quality factor of the coupled system corresponding to each label is A. 12 Similarly, a table is constructed to compare the number of tags with the quality factor A of the coupling system under a given reader antenna transmit power. This table, obtained through measurement, stores the quality factor of the coupling system corresponding to different numbers of tags at a given reader antenna transmit power. The specific contents of this table are shown in Table 1. Where W... T This refers to the power value transmitted by the reader's antenna, such as 5.5W, 6W, 6.5W, 7W, etc.; at a given power, the number of tags is represented by N, and the number of different tag counts is represented by n, such as W. T At a power of 7W, N can take the values ​​N=32, N=64, and N=128, in which case n=3; under a certain reader antenna transmission power W T In the following, the quality factor measurement value of the coupled system corresponding to the number of tags N is represented by A.

[0047] Table 1. Example of a comparison between the number of tags and the quality factor A of the coupled system.

[0048]

[0049] S2. Estimated number of tags to be inventoried. Determine the reader antenna transmit power W. T Next, the quality factor A of the coupling system corresponding to the tag to be inventoried is measured, and the number N of the tags to be inventoried is estimated based on the quality factor A of the coupling system of the reader antenna and the lookup table in S1.

[0050] S3. Actual Tag Inventory. Based on the estimated number of tags N, estimate the initial Q value of the anti-collision algorithm, where Q = round(log2N), and implement tag inventory based on the anti-collision optimization algorithm.

[0051] Example 2:

[0052] A method for estimating the number of tags using the quality factor of the coupling between the reader antenna and the tag, comprising:

[0053] (1) Measurement of the quality factor of the coupled system. This involves measuring the correlation between different numbers of tags and the quality factor of the coupled system.

[0054] (2) Estimation of the number of tags to be inventoried. Measure the quality factor of the coupling system corresponding to the tags to be inventoried, and estimate the number of tags N to be inventoried based on the correspondence between the number of tags and the quality factor of the coupling system;

[0055] (3) Tag inventory. Based on the estimated number of tags N, set the initial Q value of the anti-collision algorithm and optimize the anti-collision algorithm.

[0056] Furthermore, in step (1):

[0057] Multiple reader / writer transmit power (W) is required T Below, record the quality factor A of the coupled system corresponding to different numbers of labels N.

[0058] Furthermore, in step (2):

[0059] At a certain reader antenna transmission power W T First, measure the coupling system quality factor A corresponding to the number of tags to be inventoried. Then, based on this coupling system quality factor A, estimate the number of tags N to be inventoried.

[0060] Furthermore, in step (3):

[0061] Based on the estimated number of tags N, the initial Q value of the anti-collision algorithm is estimated, where Q = round(log2N), to realize tag inventory based on the anti-collision optimization algorithm.

[0062] This invention discloses a method for estimating the number of tags using the quality factor of the reader antenna coupled with the tag. For simplicity, the reader antenna and tag coupling system is hereinafter referred to as the coupling system. The method includes: (1) Measurement of the quality factor of the coupling system. Under a certain reader transmission power, the correspondence between different tag numbers and the quality factor of the coupling system is measured; (2) Estimation of the number of tags to be inventoried. First, the quality factor of the coupling system corresponding to the number of tags to be inventoried is measured, and then the number of tags to be inventoried is estimated based on the correspondence between the number of tags and the quality factor of the coupling system; (3) Tag inventory. Based on the estimated number of tags, the initial Q value of the anti-collision algorithm is set, the anti-collision algorithm is optimized, and the tag inventory is realized.

[0063] The method proposed in this invention pre-collects the quality factors of the coupling system corresponding to different numbers of tags under a certain reader transmission power, and designs an initial Q-value prediction for a high-frequency RFID system anti-collision algorithm based on the prior value. This can solve the problem of improper initial Q-value setting of the anti-collision algorithm and effectively improve the reading efficiency of the high-frequency RFID system.

[0064] This invention estimates the approximate range of the number of tags to be inventoried by coupling the system quality factor, thereby setting an appropriate initial Q value for the anti-collision algorithm and optimizing the anti-collision algorithm, which will play an important role in RFID applications.

[0065] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for estimating the number of tags using the quality factor of a reader antenna and coupling system, characterized in that, The method includes the following steps: S1. Measurement of quality factor of coupling system: Measure the correspondence between different numbers of tags in the coupling system and the quality factor of the coupling system; wherein, the coupling system includes high-frequency RFID tags and readers, and the communication between the high-frequency RFID tags and readers is achieved through the magnetic field coupling of the antenna coils of both parties; S2. Estimation of the number of tags to be inventoried: First, measure the quality factor of the coupled system corresponding to the tags to be inventoried. Then, based on the correspondence between the quality factor of the coupled system and the number of tags, estimate the number of tags to be inventoried. N ; S3. Tag Inventory: Based on the estimated number of tags. N Estimate the initial Q value of the collision avoidance algorithm; in, In step S1, the voltage value of the received signal after being divided by a voltage divider resistor is collected by the analog-to-digital converter (ADC) module in the reader, and the voltage value converted by the ADC module in the reader is used to obtain the instantaneous power of the reader. Then, the instantaneous power of the received signal is integrated over time to obtain the received energy of the reader. The known emission energy of the reader / writer With the energy received by the reader The difference lies in the energy consumed by the circuit. The quality factor of the coupled system A The calculation is as follows: （1） In the formula, This represents the energy stored in the circuit at resonance, i.e., the energy received by the reader / writer. This indicates that the reader emits energy. This indicates the energy consumed by the circuit; Step S1 specifically includes: under a certain reader antenna transmission power, testing the quality factor A of the coupling system corresponding to different numbers of tags, and constructing a comparison table of the number of tags and the quality factor A of the coupling system under a certain reader antenna transmission power.

2. The method for estimating the number of tags using the quality factor of the reader antenna and coupling system as described in claim 1, characterized in that, In step S3 .

3. The method for estimating the number of tags using the quality factor of the reader antenna and coupling system as described in claim 1, characterized in that, When the tag enters the electromagnetic field of the reader, the tag coil enters a resonant state, thereby coupling and obtaining energy to activate and operate the tag. At the same time, the clock signal is extracted from the carrier signal of the reader antenna.

4. The method for estimating the number of tags using the quality factor of the reader antenna and coupling system as described in claim 1, characterized in that, High-frequency RFID tags use a load modulation method based on a subcarrier. The tag antenna is coupled to the reader antenna, which is equivalent to the load of the reader antenna. Switching the load resistor on the tag antenna changes the load of the reader antenna, thereby changing the voltage on the reader antenna and realizing data transmission. When these tags are densely stacked, a coupling relationship is formed between each tag and the antenna, and the quality factor of the coupling system measured at the reader changes.

5. The method for estimating the number of tags using the quality factor of the reader antenna and coupling system as described in claim 1, characterized in that, The number of tags is negatively correlated with the quality factor of the coupled system.

6. The method for estimating the number of tags using the quality factor of the reader antenna and coupling system as described in claim 1, characterized in that, Step S2 specifically includes: determining the reader antenna transmit power. Next, the quality factor of the coupled system corresponding to the label to be inventoried is measured. A Based on the quality factor of the reader antenna coupling system A And the comparison table in S1 to estimate the number of labels to be inventoried. N .

7. The method for estimating the number of tags using the quality factor of the reader antenna and coupling system as described in claim 1, characterized in that, The reader operates in ISO 18000-3 protocol Mode 3.

Images