RFID reader-writer tag reading method

Abstract

The invention belongs to the technical field of radio frequency identification, and particularly relates to an RFID reader-writer tag reading method, which comprises the following steps of: selecting an initial transmitting frequency point and an initial impedance matcher; transmitting a signal to the to-be-read tag at fixed power; detecting an intensity value of a label return signal; comparing the intensity value of the return signal with a preset threshold value; selecting a final impedance matcher which keeps an optimal matching state with the initial transmitting frequency point from the plurality of impedance matchers according to a comparison result; and the selected final impedance matcher is used for carrying out subsequent tag reading work. By detecting the RSSI value returned by the tag and combining the switching mode of the impedance matcher, a proper frequency band range can be quickly selected, and proper frequency points can be further optimized and selected for different scenes, so that the reading performance of the reader-writer is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of radio frequency identification, and in particular to a method for reading a tag of an RFID reader / writer. Background Art

[0002] RFID (Radio Frequency Identification) is a non-contact automatic identification technology. RFID has a wide range of application scenarios. In practical applications, the length of the reading distance and the number of tags identified per unit time are often the key factors that reflect the performance of the reader.

[0003] In order to adapt to a wider range of application scenarios, multiple impedance matchers are set in the reader / writer. In the current application scenario, the impedance matcher is switched by the switch to achieve the impedance transformation of the current frequency point. Finally, the power detection is used to determine the effect of antenna matching. If the effect is not good, the switch continues to switch to the next impedance matcher until all impedance adapters are switched. The impedance matcher with the smallest standing wave ratio is selected for antenna adaptation, thereby achieving the effect of improving antenna matching. In this way, useful signals can be radiated and received to the greatest extent possible, reducing path loss, improving antenna radiation efficiency, and achieving the purpose of improving reading and writing performance.

[0004] However, switching the impedance matchers one by one by switching to select the impedance matcher with the smallest standing wave ratio will further increase the reading time and also increase the power consumption. Moreover, as the working time increases, the reader / writer needs to further reduce the power consumption while ensuring that the reading and writing work can be completed. For example, the transmission frequency and transmission power can be optimized according to the usage scenario. However, when the transmission frequency is changed, the impedance matcher must be reselected, which adds trouble invisibly. Summary of the invention

[0005] The present invention provides an RFID reader / writer tag reading method, which is used to solve the problem in the prior art that switching impedance matchers one by one through a switch to select an impedance matcher with the smallest standing wave ratio will further increase the reading time and also increase the power consumption.

[0006] The present invention provides a RFID reader / writer tag reading method, comprising:

[0007] Selecting the initial transmitting frequency point and the initial impedance matcher;

[0008] Transmitting a signal to the tag to be read at a fixed power;

[0009] Detect the strength value of the signal returned by the tag;

[0010] Compare the strength value of the returned signal with a preset threshold;

[0011] Selecting a final impedance matcher that maintains the best matching state with the initial transmission frequency point from the plurality of impedance matchers according to the comparison result;

[0012] The selected final impedance matcher is used for subsequent tag reading.

[0013] According to an RFID reader / writer tag reading method provided by the present invention, the number of multiple impedance matchers is N, each impedance matcher corresponds to a unique frequency band range, and the frequency band ranges corresponding to the first impedance matcher to the Nth impedance matcher gradually increase.

[0014] According to an RFID reader / writer tag reading method provided by the present invention, N is an odd number greater than or equal to 5.

[0015] According to an RFID reader / writer tag reading method provided by the present invention, the initial impedance matcher is an impedance matcher located in the middle.

[0016] According to an RFID reader / writer tag reading method provided by the present invention, the center frequency point within the frequency band corresponding to each impedance matcher is recorded as F0, the highest frequency point is recorded as FH, and the lowest frequency point is recorded as FL;

[0017] The tag reading operation is performed with the initial transmitting frequency point and the initial impedance matching device F0, FH, and FL respectively, and the strength value RSSI of the tag return signal is detected;

[0018] The RSSI values ​​corresponding to F0, FH, and FL of the initial impedance matcher are compared with the preset thresholds respectively, and the final impedance matcher is selected according to the comparison results.

[0019] According to an RFID reader / writer tag reading method provided by the present invention, if the RSSI values ​​corresponding to F0, FH, and FL of the initial impedance matcher are all greater than or equal to a preset threshold, the initial impedance matcher is selected as the final impedance matcher.

[0020] According to an RFID reader / writer tag reading method provided by the present invention, if the RSSI values ​​corresponding to F0, FH, and FL of the initial impedance matcher are all less than a preset threshold, the initial impedance matcher is switched to the first impedance matcher or the Nth impedance matcher farthest from it for further judgment.

[0021] According to an RFID reader / writer tag reading method provided by the present invention, if the difference between the RSSI values ​​corresponding to F0, FH, and FL of the initial impedance matcher and the preset threshold value has a positive value or a negative value, the RSSI values ​​corresponding to F0, FH, and FL of the initial impedance matcher are compared:

[0022] If the RSSI values ​​corresponding to FH, F0, and FL of the initial impedance matcher decrease in sequence, the initial impedance matcher is switched to the next impedance matcher adjacent thereto; if the RSSI values ​​corresponding to FL, F0, and FH of the next impedance matcher decrease in sequence, the initial impedance matcher or the next impedance matcher adjacent to the initial impedance matcher is arbitrarily selected as the final impedance matcher; if the RSSI values ​​corresponding to FL, F0, and FH of the next impedance matcher do not decrease in sequence, the initial impedance matcher is switched to the first impedance matcher farthest from it for judgment;

[0023] If the RSSI values ​​corresponding to FL, F0, and FH of the initial impedance matcher decrease in sequence, the initial impedance matcher is switched to the previous impedance matcher adjacent to it; if the RSSI values ​​corresponding to FH, F0, and FL of the previous impedance matcher decrease in sequence, the initial impedance matcher or the previous impedance matcher adjacent to the initial impedance matcher is arbitrarily selected as the final impedance matcher; if the RSSI values ​​corresponding to FH, F0, and FL of the previous impedance matcher do not decrease in sequence, the initial impedance matcher is switched to the Nth impedance matcher farthest from it for judgment.

[0024] According to an RFID reader / writer tag reading method provided by the present invention, when the initial impedance matcher is switched to the impedance matcher farthest from it for judgment, if the RSSI values ​​corresponding to FL, F0, and FH of the farthest impedance matcher are not in a state of increasing or decreasing in sequence, the farthest impedance matcher is switched to an impedance matcher whose RSSI value has not been detected, and the impedance matcher corresponding to the largest RSSI value is selected as the final impedance matcher.

[0025] According to an RFID reader / writer tag reading method provided by the present invention, selecting an impedance matcher corresponding to a maximum RSSI value includes:

[0026] Calculate the average value of RSSI values ​​corresponding to FL, F0, and FH of the impedance matcher;

[0027] The impedance matcher with the largest average RSSI value is selected as the final impedance matcher.

[0028] The RFID reader / writer tag reading method provided by the present invention can quickly select a suitable frequency band range by detecting the RSSI value returned by the tag and combining the switching method of the impedance matcher. For different scenarios, the suitable frequency point can be further optimized to improve the reading performance of the reader / writer. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0030] Figure 1 It is a flowchart of the RFID reader-writer tag reading method provided by the present invention;

[0031] Figure 2 This is one of the flow charts of the RFID reader / writer tag reading method provided by the present invention;

[0032] Figure 3 This is the second flow chart of the RFID reader / writer tag reading method provided by the present invention;

[0033] Figure 4 It is a structural schematic diagram of the RFID reader / writer provided by the present invention. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0035] Combine the following Figure 1-Figure 3 A RFID reader / writer tag reading method of the present invention is described, comprising:

[0036] Select the initial transmission frequency point and the initial impedance matcher; it should be understood that the initial transmission frequency point is set manually according to the actual situation;

[0037] The signal is transmitted to the tag to be read at a fixed power. It is worth noting that the fixed power here is not fixed, but only remains fixed during the reading process. When the reading work is not in progress, it can be adjusted according to the actual situation.

[0038] Detect the strength value of the signal returned by the tag;

[0039] Compare the strength value of the returned signal with a preset threshold;

[0040] Selecting a final impedance matcher that maintains the best matching state with the initial transmission frequency point from the multiple impedance matchers according to the comparison result;

[0041] The selected final impedance matcher is used for subsequent tag reading.

[0042] Among them, the number of multiple impedance matchers is N, each impedance matcher corresponds to a unique frequency band range, and the frequency band ranges corresponding to the first impedance matcher to the Nth impedance matcher gradually increase, and N is an odd number greater than or equal to 5; the initial impedance matcher is the impedance matcher located in the middle.

[0043] The larger the number of N, the larger the total frequency band range covered by multiple impedance matchers, and the wider the adaptation to application scenarios; at the same time, the narrower the frequency band range covered by each impedance matcher, the higher the accuracy; the total frequency band range and the frequency band range of a single impedance matcher need to be reasonably matched. N can of course also be an even number, but it is only for the convenience of the subsequent limitation of the initial impedance to the impedance in the middle, so it is easier to understand with an odd number. For example, assuming that the total frequency band range is 902MHz-937MHz, N=5, then the frequency band range corresponding to the first impedance matcher can be set to 902MHz-909MHz, the frequency band range corresponding to the second impedance matcher is 909MHz-916MHz, the frequency band range corresponding to the third impedance matcher is 916MHz-923MHz, the frequency band range corresponding to the fourth impedance matcher is 923MHz-930MHz, and the frequency band range corresponding to the fifth impedance matcher is 930MHz-937MHz. Of course, the above settings are not limited, and other reasonable data can be set according to needs.

[0044] For the convenience of comparison, the center frequency point within the frequency band of each impedance matcher is recorded as F0, the highest frequency point is recorded as FH, and the lowest frequency point is recorded as FL.

[0045] The tag reading operation is performed with the initial transmitting frequency point and the initial impedance matching device F0, FH, and FL respectively, and the strength value RSSI of the tag return signal is detected;

[0046] The RSSI values ​​corresponding to F0, FH, and FL of the initial impedance matcher are compared with the preset thresholds respectively, and the final impedance matcher is selected according to the comparison results.

[0047] The specific comparison results are as follows:

[0048] If the RSSI values ​​corresponding to F0, FH, and FL of the initial impedance matcher are all greater than or equal to the preset threshold, the initial impedance matcher is selected as the final impedance matcher. The preset threshold here can be reasonably set according to the above-mentioned total frequency band range and the specific number of N. According to the above example, assuming that the total frequency band range is 902MHz-937MHz, N=5, then the preset threshold is 60. The RSSI values ​​corresponding to F0, FH, and FL of the initial impedance matcher are all greater than or equal to the preset threshold, indicating that the tag reading effect is better in this frequency band range, and there is no need to switch the frequency band. This frequency band can be selected.

[0049] If the RSSI values ​​corresponding to F0, FH, and FL of the initial impedance matcher are all less than the preset threshold, the initial impedance matcher is switched to the 1st impedance matcher or the Nth impedance matcher farthest from it for further judgment. If the RSSI values ​​corresponding to F0, FH, and FL of the initial impedance matcher are all less than the preset threshold, it means that the tag reading effect is very poor in this frequency band range and the frequency band needs to be switched immediately. It also means that the frequency points near this frequency band are all poor. When operating, switch to the frequency band 1 or N farthest from this frequency band.

[0050] If the difference between the RSSI values ​​corresponding to F0, FH, and FL of the initial impedance matcher and the preset threshold is both positive and negative, that is, the statistical RSSI values ​​are relatively scattered, with both large and small values, then it is necessary to compare the frequency points corresponding to the large and small values ​​for analysis, that is, to compare the RSSI values ​​corresponding to F0, FH, and FL of the initial impedance matcher:

[0051] If the RSSI values ​​corresponding to FH, F0, and FL of the initial impedance matcher decrease in sequence (that is, the RSSI values ​​of the three points are: FH≥F0≥FL), the initial impedance matcher is switched to the next impedance matcher adjacent to it; if the RSSI values ​​corresponding to FL, F0, and FH of the next impedance matcher decrease in sequence (that is, the RSSI values ​​of the three points are: FL≥F0≥FH), the initial impedance matcher or the next impedance matcher adjacent to the initial impedance matcher is arbitrarily selected as the final impedance matcher (that is, the corresponding two frequency bands are acceptable); if the RSSI values ​​corresponding to FL, F0, and FH of the next impedance matcher do not decrease in sequence, indicating that the RSSI values ​​in the next frequency band are irregular, the initial impedance matcher is switched to the first impedance matcher farthest from it for judgment;

[0052] If the RSSI values ​​corresponding to FL, F0, and FH of the initial impedance matcher decrease in sequence (that is, the RSSI values ​​of the three points are: FL≥F0≥FH), the initial impedance matcher is switched to the previous impedance matcher adjacent to it; if the RSSI values ​​corresponding to FH, F0, and FL of the previous impedance matcher decrease in sequence (that is, the RSSI values ​​of the three points are: FH≥F0≥FL), the initial impedance matcher or the previous impedance matcher adjacent to the initial impedance matcher is arbitrarily selected as the final impedance matcher (that is, the corresponding two frequency bands are both acceptable); if the RSSI values ​​corresponding to FH, F0, and FL of the previous impedance matcher do not decrease in sequence, indicating that the RSSI values ​​in the previous frequency band are irregular, the initial impedance matcher is switched to the Nth impedance matcher farthest from it for judgment.

[0053] When the initial impedance matcher is switched to the impedance matcher farthest from it for judgment (at this time, the farthest impedance matcher is the first or the Nth), if the RSSI values ​​corresponding to FL, F0, and FH of the farthest impedance matcher are not in a state of increasing or decreasing in sequence (that is, the RSSI values ​​of the three frequency points of the first impedance matcher are not FL≥F0≥FH, and the RSSI values ​​of the three frequency points of the Nth impedance matcher are not FH≥F0≥FL), it means that the RSSI value distribution within the corresponding frequency band of the farthest impedance matcher is relatively scattered and irregular, then the farthest impedance matcher is switched to an impedance matcher whose RSSI value has not been detected, and the corresponding impedance matcher with the largest RSSI value is selected as the final impedance matcher. The reason for this operation is that if the farthest impedance matcher is the first impedance matcher, and the RSSI values ​​of the three frequency points of the first impedance matcher are FL≥F0≥FH, it means that the first frequency band is already the optimal frequency band, and the first impedance matcher is selected as the final impedance matcher; if the farthest impedance matcher is the Nth impedance matcher, and the RSSI values ​​of the three frequency points of the Nth impedance matcher are FH≥F0≥FL, it means that the Nth frequency band is already the optimal frequency band, and the Nth impedance matcher is selected as the final impedance matcher; if none of the above situations is the case, according to the above process logic, it is proved that the overall RSSI value distribution has no logic, and can only be detected one by one. Of course, this situation is an extreme case and will occur less frequently.

[0054] Further, the impedance matching device corresponding to the largest RSSI value is selected, including:

[0055] Calculate the average value of RSSI values ​​corresponding to FL, F0, and FH of the impedance matcher;

[0056] The impedance matcher with the largest average RSSI value is selected as the final impedance matcher.

[0057] After the above operations, the final impedance matcher has been selected. Further, the optimal frequency point can be selected within the optimal frequency band corresponding to the final impedance matcher. At this time, a second threshold can be set. Assuming that the preset threshold mentioned above is the first threshold (the first threshold is 60), in order to select the optimal frequency point here, the second threshold can be set to be higher than the first threshold (the second threshold is set to 70). Therefore, the frequency point can be switched point by point or at intervals within the optimal frequency band to detect the RSSI value, and the frequency point with an RSSI value greater than or equal to the second threshold is selected as the optimal frequency point. There can be one or more optimal frequencies, and the subsequent tag reading work is performed with the selected optimal frequency point.

[0058] The above scheme is suitable for quickly switching to the optimal frequency band (or frequency point) in different scenarios and under the remaining power status of different readers and writers. When it is necessary to adjust the transmission frequency point and transmission power according to the actual usage conditions (such as usage scenarios, remaining power of the reader and writer, reading and writing distance, etc.) to find the impedance matcher that best matches the transmission frequency point, the above scheme can be used to quickly find it, so as to improve the reading and writing performance (including reading and writing distance and reading and writing efficiency) of the reader and writer in the current state, and ensure that the reader and writer can further reduce the overall power consumption and increase the battery life on the basis of normal operation.

[0059] The present invention also provides an RFID reader / writer, which is adapted to the above RFID reader / writer tag reading method through innovative circuit design.

[0060] like Figure 4As shown, the RFID reader / writer includes the following parts: an RFID main chip, a PA (power amplifier), a directional coupler, a COMP (comparator), a processor, a switch, a plurality of impedance matchers and an ANT (antenna). The RFID main chip is mainly used for modulation and demodulation of radio frequency signals; the power amplifier PA is used to amplify the input radio frequency signal, convert the DC power provided by the DC power supply into radio frequency power and transmit it out; the directional coupler is used to isolate the signal of the power amplifier from the signal received by the antenna, and the transmission and reception can be realized at the same time through the directional coupler; the comparator COMP is used to compare the forward power output from the coupling end of the directional coupler with the backward power output from the isolation end, so as to detect the matching degree of the antenna; the processor is used for processing and control of baseband signals; the switch is used to open and close the path between the antenna and the impedance matcher to achieve the purpose of switching the impedance matcher (the switch is switched to the final impedance matcher in the above manner); the impedance matcher is a device with a selectable specific frequency range, which achieves the minimum or maximum impedance within a specific frequency band through a combination of inductance, capacitance and microstrip line, so as to achieve the purpose of changing the impedance of the radio frequency link; the antenna is used to radiate the signal amplified by the power amplifier into the air, and at the same time receive the weak useful signal in the air into the circuit, and finally enter the receiving circuit through the directional coupler.

[0061] When the RFID reader changes the transmission frequency point and selects the optimal final impedance matcher from multiple impedance matchers, it adopts the RFID reader tag reading method mentioned above. The rest of the work flow is roughly consistent with the existing technology and will not be repeated here.

[0062] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for reading a tag using an RFID reader / writer, characterized in that: include: Selecting the initial transmitting frequency point and the initial impedance matcher; Transmitting a signal to the tag to be read at a fixed power; Detect the strength value of the signal returned by the tag; Compare the strength value of the returned signal with a preset threshold; Selecting a final impedance matcher that maintains the best matching state with the initial transmission frequency point from the multiple impedance matchers according to the comparison result; The selected final impedance matcher is used for subsequent tag reading.

2. The RFID reader / writer tag reading method according to claim 1, characterized in that: The number of the multiple impedance matchers is N, each impedance matcher corresponds to a unique frequency band range, and the frequency band ranges corresponding to the first impedance matcher to the Nth impedance matcher gradually increase.

3. The RFID reader / writer tag reading method according to claim 2, characterized in that: N is an odd number greater than or equal to 5.

4. The RFID reader / writer tag reading method according to claim 3, characterized in that: The initial impedance matcher is the impedance matcher located in the middle.

5. The RFID reader / writer tag reading method according to claim 4, characterized in that: The center frequency point within the frequency band of each impedance matcher is recorded as F0, the highest frequency point is recorded as FH, and the lowest frequency point is recorded as FL; The tag reading operation is performed with the initial transmitting frequency point and the initial impedance matching device F0, FH, and FL respectively, and the strength value RSSI of the tag return signal is detected; The RSSI values ​​corresponding to F0, FH, and FL of the initial impedance matcher are compared with the preset thresholds respectively, and the final impedance matcher is selected according to the comparison results.

6. The RFID reader / writer tag reading method according to claim 5, characterized in that: If the RSSI values ​​corresponding to F0, FH, and FL of the initial impedance matcher are all greater than or equal to the preset threshold, the initial impedance matcher is selected as the final impedance matcher.

7. The RFID reader / writer tag reading method according to claim 5, characterized in that: If the RSSI values ​​corresponding to F0, FH, and FL of the initial impedance matcher are all less than the preset threshold, the initial impedance matcher is switched to the first impedance matcher or the Nth impedance matcher farthest from it and then the judgment is performed.

8. The RFID reader / writer tag reading method according to claim 5, characterized in that: If the difference between the RSSI values ​​corresponding to F0, FH, and FL of the initial impedance matcher and the preset threshold is positive or negative, then the RSSI values ​​corresponding to F0, FH, and FL of the initial impedance matcher are compared: If the RSSI values ​​corresponding to FH, F0, and FL of the initial impedance matcher decrease in sequence, the initial impedance matcher is switched to the next impedance matcher adjacent thereto; if the RSSI values ​​corresponding to FL, F0, and FH of the next impedance matcher decrease in sequence, the initial impedance matcher or the next impedance matcher adjacent to the initial impedance matcher is arbitrarily selected as the final impedance matcher; if the RSSI values ​​corresponding to FL, F0, and FH of the next impedance matcher do not decrease in sequence, the initial impedance matcher is switched to the first impedance matcher farthest from it for judgment; If the RSSI values ​​corresponding to FL, F0, and FH of the initial impedance matcher decrease in sequence, the initial impedance matcher is switched to the previous impedance matcher adjacent to it; if the RSSI values ​​corresponding to FH, F0, and FL of the previous impedance matcher decrease in sequence, the initial impedance matcher or the previous impedance matcher adjacent to the initial impedance matcher is arbitrarily selected as the final impedance matcher; if the RSSI values ​​corresponding to FH, F0, and FL of the previous impedance matcher do not decrease in sequence, the initial impedance matcher is switched to the Nth impedance matcher farthest from it for judgment.

9. The RFID reader / writer tag reading method according to claim 7 or 8, characterized in that: When the initial impedance matcher is switched to the impedance matcher farthest from it for judgment, if the RSSI values ​​corresponding to FL, F0, and FH of the farthest impedance matcher are not in a state of increasing or decreasing successively, the farthest impedance matcher is switched to an impedance matcher whose RSSI value has not been detected, and the impedance matcher corresponding to the largest RSSI value is selected as the final impedance matcher.

10. The RFID reader / writer tag reading method according to claim 9, characterized in that: Select the impedance matcher with the largest RSSI value, including: Calculate the average value of RSSI values ​​corresponding to FL, F0, and FH of the impedance matcher; The impedance matcher with the largest average RSSI value is selected as the final impedance matcher.

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