A method for monitoring and dynamically adjusting receiving gain of a high-frequency RFID system

Abstract

The present invention relates to a method for monitoring and dynamically adjusting the receiving gain of a high-frequency RFID system, and belongs to the field of radio frequency identification. The present invention is applicable to a high-frequency RFID system that adopts a dynamic Q-value ALOHA algorithm, such as a high-frequency RFID system that adopts the ISO18000‑3 protocol Mode 3 mode. The method mainly includes: (1) receiving gain monitoring, monitoring the current receiving gain in the anti-collision process, and judging whether the current receiving gain is appropriate. (2) receiving gain adjustment. The dynamic adjustment of the receiving gain is combined with the anti-collision algorithm process to ensure that each tag can be recognized by the reader when the receiving gain is appropriate during the multi-tag reading process, thereby improving the dynamic range of the reader. The method proposed in the present invention realizes the monitoring and dynamic adjustment of the receiving gain of the high-frequency RFID system, and can solve the problem that under a specific gain, the response signal of some tags is too strong, resulting in saturation of the receiving link or the receiving signal is too small to be correctly read by the reader, thereby effectively improving the reading accuracy of the high-frequency RFID system.

Description

Technical Field

[0001] The present invention belongs to the field of radio frequency identification, and in particular relates to a method for monitoring and dynamically adjusting receiving gain of a high-frequency RFID system. Background Art

[0002] Due to its operating frequency band and its working principle of magnetic field coupling, high-frequency RFID systems have advantages that other frequency band RFID systems do not have, such as insensitivity to liquids, controllable reading range, not easy to misread, and the ability to accurately read densely stacked RFID tags. They are widely used in industries such as archive management and smart warehousing.

[0003] However, in multi-tag reading applications, due to the principle of magnetic field coupling, the different spatial positions of each tag relative to the antenna, and the mutual coupling between tags, at a specific receive gain, after processing by the RF front-end circuit, the stronger tag response signal will experience saturation deformation, while the weaker tag signal will be difficult for the baseband circuit to process due to the low signal-to-noise ratio, making it difficult to maintain a good dynamic range. A simple approach is to set multiple gain levels, and the reader will cycle through each gain level during operation. The drawback of this method is that it does not comprehensively consider the relationship between receive gain and the anti-collision process, and simply performs multiple rounds of inventory at different gains, which is inefficient and difficult to guarantee the convergence of the method.

[0004] Therefore, there is an urgent need for a method that comprehensively considers the relationship between receiving gain and anti-collision process to improve the efficiency of tag inventory and meet the needs of RFID applications. The present invention is created to meet this practical need. Summary of the Invention

[0005] (1) Technical issues to be resolved

[0006] The technical problem to be solved by the present invention is how to provide a method for monitoring and dynamically adjusting the receiving gain of a high-frequency RFID system to solve the problem that stronger tag response signals will be saturated and deformed, while weaker tag signals will be difficult for the baseband circuit to process due to the low signal-to-noise ratio, making it difficult to ensure an excellent dynamic range.

[0007] (2) Technical solution

[0008] In order to solve the above technical problems, the present invention proposes a method for monitoring and dynamically adjusting the receiving gain of a high-frequency RFID system, which includes the following steps:

[0009] S1. Receiver gain monitoring: Determine the cause of communication failure based on the characteristics of the tag response signal received when decoding failure or verification failure occurs during the inventory process. If the communication failure is caused by saturation or a small signal, the gain is too large or too small. It is necessary to look up the gain adjustment table based on the characteristics of the tag response signal to obtain the appropriate receive gain.

[0010] S2, receiving gain adjustment, including the following sub-steps:

[0011] S21, setting initial gain;

[0012] S22. Construct a gain configuration table, which is obtained by measurement and stores appropriate gain adjustment values ​​corresponding to different saturation levels and different undersaturation levels of the tag signal;

[0013] S23, adjust the inventory strategy: In the anti-collision algorithm, the time slot counting parameter is represented by an integer Q value, Q fp It is a floating point representation of the Q value. When the tag response shows "decoding and verification failure", the received tag signal is detected. If the waveform does not appear "saturated or too small", it is processed according to the normal anti-collision process. Q fp Continue counting after the value increases; if the waveform appears "saturated or too small" and the algorithm does not converge to Q = 0, the two abnormal conditions of saturation and too small are regarded as no response, so that the algorithm converges quickly, and most of the tags that are suitable for inventory counting with the initial gain are counted so that they do not participate in subsequent inventory counting; if the waveform appears "saturated or too small" and the algorithm converges to Q = 0, then look up the gain configuration table, adjust the gain, and then increase Q fp The value increases by 1 and the inventory continues.

[0014] (3) Beneficial effects

[0015] The present invention proposes a method for monitoring and dynamically adjusting the receiving gain of a high-frequency RFID system. The method proposed in the present invention realizes the monitoring and dynamic adjustment of the receiving gain of the high-frequency RFID system. It can solve the problem that under a specific gain, the response signal of some tags is too strong, resulting in saturation of the receiving link or the received signal is too small to be correctly read by the reader, thereby effectively improving the reading accuracy of the high-frequency RFID system. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is the normal waveform of the Start Of Frame (SOF) part of the tag response after envelope detection and input to the reader baseband.

[0017] Figure 2 The present invention is a flowchart of a method for monitoring and dynamically adjusting receiving gain of a high-frequency RFID system. DETAILED DESCRIPTION

[0018] In order to make the purpose, content and advantages of the present invention more clear, the specific implementation methods of the present invention are further described in detail below with reference to the accompanying drawings and examples.

[0019] The present invention discloses a method for monitoring and dynamically adjusting the receiving gain of a high-frequency RFID system, which is applicable to a high-frequency RFID system using a dynamic Q-value ALOHA algorithm, such as a high-frequency RFID system using Mode 3 of the ISO 18000-3 protocol. The method mainly includes: (1) receiving gain monitoring, monitoring the current receiving gain in the anti-collision process, and judging whether the current receiving gain is appropriate. (2) receiving gain adjustment. The dynamic adjustment of the receiving gain is combined with the anti-collision algorithm process to ensure that each tag can be recognized by the reader when the receiving gain is appropriate during the multi-tag reading process, thereby improving the dynamic range of the reader.

[0020] This invention proposes a method that combines the anti-collision process with the monitoring and dynamic adjustment of the receiving gain, effectively improving the dynamic range of the high-frequency RFID system while ensuring inventory efficiency. The method includes:

[0021] S1. Receiver gain monitoring. The cause of communication failure (saturation, too low, or collision) is determined based on the characteristics of the tag response signal received when decoding or verification failure occurs during the inventory process. If the communication failure is caused by saturation or too low a signal, the gain is too high or too low. The appropriate receive gain needs to be determined by searching the gain adjustment table based on the characteristics of the tag response signal.

[0022] S2, receiving gain adjustment, including the following sub-steps:

[0023] S21. Set the initial gain. The initial gain is obtained through previous tests and is the gain that can accurately read most tags under actual working conditions.

[0024] S22. Construct a gain configuration table. Based on the RF front-end design, a gain configuration table is constructed based on actual measurements of tag signal saturation and signal undershoot. This table, derived from measurements, stores appropriate gain adjustments for different levels of tag signal saturation and signal undershoot. When a tag signal is saturated or undershooting, the table is used to determine the gain configuration required to correctly read the tag.

[0025] S23, adjust the inventory strategy. In the anti-collision algorithm, the slot counting parameter is represented by an integer Q value, Q fp It is a floating point representation of the Q value. The 18000-3 protocol Mode 3 mode specifies that the Q value range is [0,15]. When the tag response shows "decoding, verification failure", it is necessary to detect the received tag signal. If the waveform does not show "saturation or too small", it will be processed according to the normal anti-collision process. fpContinue counting after the value increases; if the waveform appears "saturated or too small" and the algorithm does not converge to Q = 0, the two abnormal conditions of saturation and too small are regarded as no response. The purpose of this is to make the algorithm converge quickly and count most of the tags that are suitable for inventory at the initial gain so that they do not participate in subsequent inventory; if the waveform appears "saturated or too small" and the algorithm converges to Q = 0, then look up the gain configuration table, adjust the gain, and then increase Q fp The value increases by 1 and the inventory continues.

[0026] Example 1:

[0027] The present invention proposes a method that combines the anti-collision process with the monitoring and dynamic adjustment of the receiving gain, effectively improving the dynamic range of the high-frequency RFID system while ensuring inventory efficiency.

[0028] The following uses reverse amplitude shift keying (ASK) modulation and Manchester encoding in Mode 3 of the ISO 18000-3 protocol as an example to illustrate a specific implementation method of the present invention, but does not limit the specific implementation method. The specific implementation process of the method is as follows.

[0029] (1) Receive gain monitoring.

[0030] The reader's RF front-end circuit usually demodulates the tag's response signal through envelope detection.

[0031] like Figure 1 As shown in the figure, the upper limit of the baseband waveform refers to the maximum value that the highest level of the waveform can reach when the waveform is not saturated. If the gain is too large, the waveform maximum value and the rest of the waveform will be higher than the upper limit of the baseband waveform. The part exceeding or equal to the upper limit of the baseband waveform will all become high level, and the pulse width will change, that is, deformation will occur. In addition, because the receiving gain increases, the low level part of the baseband waveform will move up, the difference between the high and low levels will become smaller, and the high and low levels will become difficult to distinguish, which will cause problems in baseband judgment.

[0032] Figure 1 The lower limit of the baseband waveform refers to the minimum value that the low level can reach when the baseband can be correctly decoded. The waveform below the lower limit of the baseband waveform is difficult to distinguish from the noise, and the signal-to-noise ratio is too small. Because the receiving gain is small at this time, the high level part of the baseband waveform will move downward, and the difference between the high and low levels will become smaller, making it difficult to judge the baseband.

[0033] The present invention determines three situations of excessive gain (baseband waveform saturation), excessive gain (baseband waveform too small), and normal gain by judging the characteristics of the baseband waveform.

[0034] (11) Saturation determination. The voltage difference between the upper limit of the baseband waveform and the low level of the SOF (Start Of Frame) baseband waveform is used as the saturation determination condition. When the voltage difference between the upper limit of the baseband waveform and the low level of the SOF baseband waveform is less than the threshold, it can be determined that the baseband waveform is saturated, that is, the current gain is too large for the current response label, and the voltage difference between the upper limit of the baseband waveform and the low level of the SOF baseband waveform is used as the basis for measuring the degree of saturation;

[0035] (12) Too small judgment. The voltage difference between the high level of the SOF baseband waveform and the lower limit of the baseband waveform is used as the judgment condition for the baseband waveform to be too small. When the voltage difference between the high level of the SOF baseband waveform and the lower limit of the baseband waveform is less than the threshold, it is judged that the current baseband waveform is too small, that is, the current gain is too small for the current response tag, and the voltage difference between the high level of the SOF baseband waveform and the lower limit of the baseband waveform is used as the basis for measuring the degree of the tag signal being too small;

[0036] (13) Determination of other situations. Excluding the above two situations, other decoding failures and verification errors are considered tag collisions.

[0037] (2) Receive gain adjustment. The specific implementation sub-process is as follows.

[0038] According to the present invention, the process of the dynamic Q value ALOHA algorithm in Mode 3 of the ISO18000-3 protocol is improved, and the implementation process obtained is as follows: Figure 2 shown.

[0039] (21) Set the initial Q fp and initial gain. The reader first sets the initial Q fp The receiving gain is configured to the initial value. The initial gain is obtained through testing and is the optimal gain for the reader to recognize most tags within the reading range when the reader is working in a normal multi-tag environment.

[0040] (22) Construct a gain configuration table. This table is obtained by measurement and stores the appropriate gain adjustment values ​​corresponding to different saturation levels and different undersaturation levels of the tag signal. The specific contents of this table are shown in Table 1. The saturation level ΔA in the waveform abnormality is the voltage difference between the upper limit of the baseband waveform and the low level of the SOF baseband waveform; the undersaturation level ΔB in the waveform abnormality is the voltage difference between the high level of the SOF baseband waveform and the lower limit of the baseband waveform; the gain adjustment value ΔG corresponds to the waveform abnormality and is the difference between the gain to be adjusted and the appropriate gain when the waveform is abnormal.

[0041] Table 1 Example of gain configuration table

[0042]

[0043] (23) Adjust inventory strategies.

[0044] S231, RFID reader with initial Q fp and initial gain opening inventory;

[0045] S232, the reader will Q fp Round to an integer value and indicate it as Q;

[0046] S233. During the first execution, the slot count parameter in the tag is set to Q by using the BeginRound(Q) command specified in Mode 3 of the 18000-3 protocol. In subsequent cycles, the value of Q in the tag is changed by using the ResizeRound(ΔQ) command specified in Mode 3 of the 18000-3 protocol, where ΔQ is the amount of change in the Q value in the tag.

[0047] S234. The reader determines whether the tag response is "successful identification", "no response" or "decoding and verification failure". In the case of "successful identification", step S235 is executed. In the case of "no response", step S236 is executed. In the case of "decoding and verification failure", step S237 is executed.

[0048] S235, Q fp No change, determine whether the inventory end condition is met, if not, return to step S232 to continue the inventory, if the inventory end condition is met, then end the inventory;

[0049] S236, through Q fp -C's operation realizes Q fp The value decreases. After the operation, if Q fp If it is less than 0, press Q fp =0 processing, determine whether the inventory end condition is met, if not, return to step S232 to continue the inventory, if the inventory end condition is met, then end the inventory; wherein the typical value of the C value given by the protocol 18000-3 protocol Mode3 mode is 0.1<C<0.5.

[0050] S237: Detect the received tag signal. If the waveform is not "saturated or too small", proceed to step S238 according to the normal anti-collision process; if the waveform is "saturated or too small", proceed to step S239;

[0051] S238, Q fp If Q increases the C value fp If the value is greater than 15, press Q fp =15 process, determine whether the inventory end condition is met, if not, return to step S232 to continue the inventory, if the inventory end condition is met, then end the inventory;

[0052] S239, if the waveform appears "saturated or too small", determine whether the algorithm has converged to Q = 0, if not, the two abnormal conditions of saturation and too small are regarded as no response, and step S236 is executed to make the algorithm converge quickly, and most of the tags that are suitable for inventory counting with the initial gain are counted so that they do not participate in the subsequent inventory; if yes, search the gain configuration table and adjust the gain, and then Q fp Increase by 1 and return to step S232 to continue inventory.

[0053] Example 2:

[0054] A method for monitoring and dynamically adjusting receiving gain of a high-frequency RFID system, comprising:

[0055] (1) Receiver gain monitoring. The cause of communication failure (saturation, too low, or collision) is determined based on the characteristics of the tag response signal received when decoding failure or verification failure occurs during the inventory process. In other words, whether the communication failure between the reader and the tag is caused by inappropriate gain, and if so, whether it is caused by excessive gain or insufficient gain, is determined.

[0056] (2) Receiver gain adjustment: Combining the anti-collision process with the dynamic adjustment of the receiver gain effectively improves the dynamic range of the high-frequency RFID system while ensuring inventory efficiency.

[0057] In step (1), the determination method is as follows:

[0058] (11) Saturation determination. The voltage difference between the upper bound of the baseband waveform and the low level of the SOF baseband waveform is used as the saturation determination condition. When the voltage difference between the upper bound of the baseband waveform and the low level of the SOF waveform is less than the threshold, it can be determined that the baseband waveform is saturated, that is, the current gain is too large for the current response label, and this voltage difference is used as the basis for measuring the degree of saturation;

[0059] (12) Too small judgment. The voltage difference between the high level of the SOF baseband waveform and the lower limit of the baseband waveform is used as the judgment condition for the baseband waveform to be too small. When the voltage difference between the high level of the SOF baseband waveform and the lower limit of the baseband waveform is less than the threshold, it is judged that the current baseband waveform is too small, that is, the current gain is too small for the current response tag, and this voltage difference is used as the basis for measuring the degree of the tag signal being too small.

[0060] In step (2), the gain adjustment step includes:

[0061] (21) Set the initial gain. The reader first configures the receiving gain to the initial value. The initial gain is obtained through testing and is the optimal gain for the reader to recognize most tags within the reading range under normal multi-tag conditions.

[0062] (22) Construct a gain configuration table. This table is obtained by measurement and stores the appropriate gain adjustment values ​​corresponding to different saturation levels and different undershoot levels of the tag signal.

[0063] (23) Adjust the inventory strategy. The RFID reader uses the initial gain and initial Q fp Start inventory. During the inventory process, if the tag response shows "decoding, verification failed", it is necessary to detect the received tag signal. If the waveform does not show "saturation or too small", it will be processed according to the normal anti-collision process. fp Continue counting after the value increases; if the waveform appears "saturated or too small" and the algorithm does not converge to Q = 0, the two abnormal conditions of saturation and too small are regarded as no response. The purpose of this is to make the algorithm converge quickly and count most of the tags that are suitable for inventory at the initial gain so that they do not participate in subsequent inventory; if the waveform appears "saturated or too small" and the algorithm converges to Q = 0, then look up the gain configuration table, adjust the gain, and then increase Q fp The value increases by 1 and the inventory continues.

[0064] The present invention discloses a method for monitoring and dynamically adjusting the receiving gain of a high-frequency RFID system, which is applicable to a high-frequency RFID system using a dynamic Q-value ALOHA algorithm, such as a high-frequency RFID system using Mode 3 of the ISO 18000-3 protocol. The method mainly includes: (1) receiving gain monitoring, monitoring the current receiving gain in the anti-collision process, and judging whether the current receiving gain is appropriate. (2) receiving gain adjustment. The dynamic adjustment of the receiving gain is combined with the anti-collision algorithm process to ensure that each tag can be recognized by the reader when the receiving gain is appropriate during the multi-tag reading process, thereby improving the dynamic range of the reader.

[0065] The method proposed in the present invention realizes the monitoring and dynamic adjustment of the receiving gain of the high-frequency RFID system. It can solve the problem that under a specific gain, the response signal of some tags is too strong, resulting in saturation of the receiving link or the received signal is too small to be correctly read by the reader, thereby effectively improving the reading accuracy of the high-frequency RFID system.

[0066] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for monitoring and dynamically adjusting the receiving gain of a high-frequency RFID system, characterized in that: The method comprises the following steps: S1. Receiver gain monitoring: Determine the cause of communication failure based on the characteristics of the tag response signal received when decoding failure or verification failure occurs during the inventory process. If the communication failure is caused by saturation or a small signal, the gain is too large or too small. It is necessary to look up the gain adjustment table based on the characteristics of the tag response signal to obtain the appropriate receive gain. S2, receiving gain adjustment; The following sub-steps are included: S21, setting initial gain; S22. Construct a gain configuration table, which is obtained by measurement and stores appropriate gain adjustment values ​​corresponding to different saturation levels and different undersaturation levels of the tag signal; S23, adjust the inventory strategy: In the anti-collision algorithm, the time slot counting parameter is represented by an integer Q value, Q fp It is a floating point representation of the Q value. When the tag response shows "decoding and verification failure", the received tag signal is detected. If the waveform does not appear "saturated or too small", it is processed according to the normal anti-collision process. Q fp Continue counting after the value increases; if the waveform appears "saturated or too small" and the algorithm does not converge to Q = 0, the two abnormal conditions of saturation and too small are regarded as no response, so that the algorithm converges quickly, and most of the tags that are suitable for inventory counting with the initial gain are counted so that they do not participate in subsequent inventory counting; if the waveform appears "saturated or too small" and the algorithm converges to Q = 0, then look up the gain configuration table, adjust the gain, and then increase Q fp The value increases by 1 and the inventory continues.

2. The method for monitoring and dynamically adjusting the receiving gain of a high-frequency RFID system according to claim 1, wherein: In step S1, the reader's RF front-end circuit demodulates the tag's response signal through envelope detection; The upper limit of the baseband waveform refers to the maximum value that the highest level of the waveform can reach when the waveform is not saturated. If the gain is too large, the waveform maximum value and the rest of the waveform will be higher than the upper limit of the baseband waveform. The part exceeding or equal to the upper limit of the baseband waveform will all become high level, and the pulse width will change, that is, deformation will occur. In addition, because the receiving gain increases, the low level part of the baseband waveform will move up, the difference between the high and low levels will become smaller, and the high and low levels will become difficult to distinguish, which will cause problems in baseband judgment. The lower limit of the baseband waveform refers to the minimum value that the low level can reach when the baseband can be correctly decoded. The waveform below the lower limit of the baseband waveform is difficult to distinguish from noise, and the signal-to-noise ratio is too small. Because the receiving gain is small at this time, the high-level part of the baseband waveform will move downward, and the difference between the high and low levels will become smaller, making it difficult to judge the baseband.

3. The method for monitoring and dynamically adjusting the receiving gain of a high-frequency RFID system according to claim 2, wherein: The following method is used to determine if the gain is too large: the voltage difference between the upper bound of the baseband waveform and the low level of the SOF (StartOfFrame) baseband waveform is used as the saturation determination condition. When the voltage difference between the upper bound of the baseband waveform and the low level of the SOF baseband waveform is less than the threshold, it can be determined that the baseband waveform is saturated, that is, the current gain is too large for the current response label, and the voltage difference between the upper bound of the baseband waveform and the low level of the SOF baseband waveform is used as the basis for measuring the degree of saturation.

4. The method for monitoring and dynamically adjusting the receiving gain of a high-frequency RFID system according to claim 2, wherein: The situation where the gain is too small is determined by the following method: the voltage difference between the high level of the SOF baseband waveform and the lower limit of the baseband waveform is used as the judgment condition for the baseband waveform to be too small. When the voltage difference between the high level of the SOF baseband waveform and the lower limit of the baseband waveform is less than the threshold, it is determined that the current baseband waveform is too small, that is, the current gain is too small for the current response tag, and the voltage difference between the high level of the SOF baseband waveform and the lower limit of the baseband waveform is used as the basis for measuring the degree of the tag signal being too small.

5. The method for monitoring and dynamically adjusting the receiving gain of a high-frequency RFID system according to claim 2, wherein: Except for situations where the gain is too large or too small, other decoding failures and verification errors are considered tag collisions.

6. The method for monitoring and dynamically adjusting the receiving gain of a high-frequency RFID system according to any one of claims 2 to 5, wherein: The step S21 specifically includes: setting the initial Q fp and initial gain; the reader first sets the initial Q fp The receiving gain is configured as an initial value, where the initial gain is obtained through testing and is the optimal gain for the reader to identify most tags within the reading range when working in a normal multi-tag situation.

7. The method for monitoring and dynamically adjusting the receiving gain of a high-frequency RFID system according to claim 6, wherein: The step S22 specifically includes: in the gain configuration table, the saturation degree ΔA in the waveform abnormality is the voltage difference between the upper limit of the baseband waveform and the low level of the SOF baseband waveform; the too small degree ΔB in the waveform abnormality is the voltage difference between the high level of the SOF baseband waveform and the lower limit of the baseband waveform; the gain adjustment amount ΔG corresponds to the waveform abnormality, which is the difference between the gain to be adjusted and the appropriate gain when the waveform is abnormal.

8. The method for monitoring and dynamically adjusting the receiving gain of a high-frequency RFID system according to claim 7, wherein: The step S23 specifically includes the following steps: S231, RFID reader with initial Q fp and initial gain opening inventory; S232, the reader will Q fp Round to an integer value and indicate it as Q; S233. During the first execution, the slot count parameter in the tag is set to Q by using the BeginRound(Q) command specified in Mode 3 of the 18000-3 protocol. In subsequent cycles, the value of Q in the tag is changed by using the ResizeRound(ΔQ) command specified in Mode 3 of the 18000-3 protocol, where ΔQ is the amount of change in the Q value in the tag. S234. The reader determines whether the tag response is "successful identification", "no response" or "decoding and verification failure". If "successful identification", the reader executes step S235; if "no response", the reader executes step S236; if "decoding and verification failure", the reader executes step S237. S235, Q fp No change, determine whether the inventory end condition is met, if not, return to step S232 to continue the inventory, if the inventory end condition is met, then end the inventory; S236, through Q fp -C's operation realizes Q fp The value decreases. After the operation, if Q fp If it is less than 0, press Q fp =0 processing, determine whether the inventory end condition is met, if not, return to step S232 to continue the inventory, if the inventory end condition is met, then end the inventory; S237: Detect the received tag signal. If the waveform is not "saturated or too small", proceed to step S238 according to the normal anti-collision process; if the waveform is "saturated or too small", proceed to step S239; S238, Q fp If Q increases the C value fp If the value is greater than 15, press Q fp =15 process, determine whether the inventory end condition is met, if not, return to step S232 to continue the inventory, if the inventory end condition is met, then end the inventory; S239, if the waveform appears "saturated or too small", determine whether the algorithm has converged to Q = 0. If not, the two abnormal conditions of saturation and too small are regarded as no response, and step S236 is executed to make the algorithm converge quickly, and the majority of tags that are suitable for inventory counting with the initial gain are counted so that they do not participate in the subsequent inventory counting; if yes, search the gain configuration table and adjust the gain, and then Q fp Increase by 1 and return to step S232 to continue inventory.

9. The method for monitoring and dynamically adjusting the receiving gain of a high-frequency RFID system according to claim 8, wherein: The C value is 0.1<C<0.

5.

10. The method for monitoring and dynamically adjusting the receiving gain of a high-frequency RFID system according to claim 1, wherein: This method is used in a high-frequency RFID system that adopts a dynamic Q-value ALOHA algorithm.

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