A temperature measurement system and method based on an RFID temperature measurement tag

Abstract

The application relates to the field of RFID technology, in particular to a temperature measuring system and method based on an RFID temperature measuring label, which comprises the following steps: when the RFID temperature measuring label receives radio frequency energy generated by a reader, an impedance automatic matching circuit controls a digital baseband circuit to generate a disable signal according to the energy distance and / or radio frequency energy between the detected reader and the RFID temperature measuring label, so as to control and adjust the impedance value or turn off the automatic impedance matching work of the digital baseband circuit based on the disable signal, and to make the impedance automatic matching circuit switch from an optimal impedance matching working state to a non-optimal impedance matching working state. Compared with the prior art, the temperature measuring system changes the impedance matching network or turns off the impedance matching network, so that the temperature measuring label impedance matching network works in a non-optimal matching state, the energy obtained from the reader end of the temperature measuring label is reduced, and the accuracy of the temperature measuring label is improved by reducing the heat energy generated by the temperature measuring label itself.

Description

Technical Field

[0001] This invention relates to the field of RFID technology, and in particular to a temperature measurement system and method based on RFID temperature measurement tags. Background Technology

[0002] With the continuous development of science and technology, radio frequency identification (RFID) technology has been widely used in various fields. RFID technology realizes automatic identification of items and data transmission through wireless communication, and has the characteristics of wireless transmission, non-contact identification, high efficiency and large capacity storage.

[0003] RFID-based temperature measurement tags, as a novel temperature measurement method, combine sensor and RFID technologies to monitor and transmit temperature data. In practical applications, users can place a reader near the temperature tag, activate it, and establish a wireless communication connection with the RFID chip. The reader sends instructions to the RFID chip and receives the temperature data stored within it. Figure 1 For existing label temperature measurement devices, an analog-to-digital converter and a temperature sensor are added to the original label structure. Figure 1 It is known that the entire temperature measurement tag has only two antenna pads facing outwards. Its internal circuitry mainly consists of an LC impedance matching circuit, a rectifier circuit, a voltage regulator circuit, an energy storage circuit, a modulation / demodulation and clock circuit, a digital circuit and data storage circuit, an analog-to-digital converter, and a temperature sensor. In existing temperature measurement tag devices, the tag continuously receives carrier signals from the reader, storing energy in the energy storage element and radiating it into the surrounding space as heat. Due to the limitations imposed by many application scenarios, higher requirements are placed on the tag's packaging, requiring it to be as small and thin as possible. This results in less than ideal heat dissipation. When the reader's transmission power is higher and it is closer to the tag, the small size of the RFID chip and relatively poor heat dissipation lead to increased operating temperature of the tag. The operating voltage rises rapidly, generating a large amount of heat, which greatly increases the energy received by the temperature tag. This causes the local temperature of the temperature tag to become excessively high, resulting in a large error between the temperature measured by the tag and the actual temperature, significantly reducing the temperature measurement accuracy of the tag. The existing patent CN109711517A only improves the temperature measurement accuracy of the temperature tag from the perspective of analyzing measurement data, ignoring the impact of the temperature tag's own characteristics. Under the same external conditions, when the reader sends different power signals to access the temperature tag at close range, the received power and heat generation of the temperature tag are different. Since the chip size is small and the heat dissipation is relatively poor, this will cause the local temperature of the temperature tag to be significantly higher than the actual ambient temperature, which leads to a significant reduction in the accuracy of the temperature measured by the temperature tag. Summary of the Invention

[0004] This invention provides a temperature measurement system and method based on RFID temperature measurement tags. The technical problem it solves is that existing tag temperature measurement devices generate a lot of heat when the reader transmits a high-power signal at close range, which leads to a decrease in the temperature measurement accuracy of the temperature measurement chip.

[0005] To address the above technical problems, this invention provides a temperature measurement system and method based on RFID temperature measurement tags.

[0006] In a first aspect, the present invention provides a temperature measurement system based on an RFID temperature measurement tag, the temperature measurement system comprising: a digital baseband circuit and an automatic impedance matching circuit disposed inside the RFID temperature measurement tag;

[0007] The automatic impedance matching circuit is used to, when the RFID temperature measuring tag receives radio frequency energy generated by the reader, obtain the current actual operating voltage of the RFID temperature measuring tag based on a preset potential disability threshold, the energy distance between the reader and the RFID temperature measuring tag, and / or the radio frequency energy; generate a sample-and-hold output signal based on the current actual operating voltage of the tag; and send the sample-and-hold output signal to the digital baseband circuit so that the digital baseband circuit generates a disability signal based on the sample-and-hold output signal; the preset potential disability threshold includes a potential distance disability threshold and a potential energy disability threshold;

[0008] In response to the disability signal, the impedance value of the circuit is adjusted or its automatic impedance matching operation is turned off according to the disability signal, so that the automatic impedance matching circuit switches from the optimal impedance matching operation state to the non-optimal impedance matching operation state.

[0009] In a further embodiment, the automatic impedance matching circuit includes a clock divider module, an adjustable capacitor array module, a unidirectional tuning module, and a sample-and-hold circuit. The unidirectional tuning module is connected to the adjustable capacitor array module, the clock divider module, and the sample-and-hold circuit. The sample-and-hold circuit includes an optimal impedance matching sample-and-hold circuit and a non-optimal impedance matching sample-and-hold circuit.

[0010] The clock divider module is used to divide the acquired external clock to generate the real-time clock required by the automatic impedance matching circuit during the automatic impedance matching process.

[0011] The sample-and-hold circuit is used to obtain the current actual operating voltage of the RFID temperature measuring tag based on the detected energy distance between the reader and the RFID temperature measuring tag and / or the radio frequency energy, and to process the current actual operating voltage of the tag using the optimal impedance matching sample-and-hold circuit or the non-optimal impedance matching sample-and-hold circuit to generate a sample-and-hold output signal. The sample-and-hold output signal is then input to the digital baseband circuit or the unidirectional tuning module, so that the digital baseband circuit or the unidirectional tuning module controls the adjustable capacitor array module to adjust the impedance value at both ends of the RFID temperature measuring tag antenna or to turn off the automatic impedance matching operation of the automatic impedance matching circuit according to the sample-and-hold output signal.

[0012] In a further embodiment, the optimal impedance matching sample-and-hold circuit includes a first comparator, a first NMOS transistor, a second NMOS transistor, a third NMOS transistor, a first PMOS transistor, a second PMOS transistor, a third PMOS transistor, a first diode, and a second diode;

[0013] In this circuit, the output of the first comparator is connected to the gate of the first NMOS transistor and the gate of the first PMOS transistor. The drain of the first NMOS transistor is connected to the drain of the second NMOS transistor, the gate of the third NMOS transistor, the drain of the second PMOS transistor, and the gate of the third PMOS transistor. The source of the first NMOS transistor is connected to the source of the second NMOS transistor and the source of the third NMOS transistor. The gate of the second NMOS transistor is connected to the gate of the second PMOS transistor. The common terminal of the drain of the third NMOS transistor and the drain of the third PMOS transistor is connected to the positive terminal of the first diode. The sources of the first PMOS transistor and the third PMOS transistor are used to input the current actual operating voltage of the RFID temperature measurement tag. The drain of the first PMOS transistor is connected to the source of the second PMOS transistor. The negative terminal of the first diode is connected to the output of the optimal impedance matching sample-and-hold circuit through the second diode.

[0014] In a further embodiment, the optimal impedance matching sample-and-hold circuit is used to detect the energy distance between the reader and the RFID temperature measuring tag and / or the radio frequency energy according to the preset potential disability threshold when the RFID temperature measuring tag receives radio frequency energy generated by the reader, obtain a potential disability detection result, and obtain the current actual operating voltage of the RFID temperature measuring tag according to the energy distance and / or the radio frequency energy based on the potential disability detection result, compare the current actual operating voltage of the tag with the actual operating voltage of the tag in the previous round, generate an optimal impedance voltage comparison result, and input the optimal impedance voltage comparison result as a sample-and-hold output signal into the unidirectional tuning module.

[0015] The unidirectional tuning module is used to determine whether the preset optimal impedance matching adjustment condition is met based on the optimal impedance voltage comparison result. If it is met, a tuning signal is generated based on the optimal impedance voltage comparison result.

[0016] The adjustable capacitor array module is used to receive the tuning signal generated by the unidirectional tuning module, and adjust the impedance value of the impedance automatic matching circuit according to the tuning signal, repeating the cycle until the unidirectional tuning module generates a target lock flag signal according to the optimal impedance voltage comparison result.

[0017] In a further embodiment, the conditions for generating the locking flag signal include:

[0018] When the optimal impedance voltage comparison result does not meet the preset optimal impedance matching adjustment condition, the current value of the tuning signal output by the unidirectional tuning module is incremented by one until the optimal impedance voltage comparison result meets the optimal matching condition or the current value of the tuning signal is a preset locking value. Then, the unidirectional tuning module generates a target locking flag signal and a target locking control signal, and sends the target locking control signal to the digital baseband circuit.

[0019] In a further embodiment, the non-optimal impedance matching sample-and-hold circuit includes a first matching module and a second matching module. The first matching module includes a second comparator, a fourth NMOS transistor NM3, a fifth NMOS transistor NM4, a sixth NMOS transistor NM5, a fourth PMOS transistor PM3, a fifth PMOS transistor PM4, a sixth PMOS transistor PM5, a third diode, and a fourth diode. The output terminal of the second comparator is connected to the gate of the fourth NMOS transistor and the gate of the fourth PMOS transistor. The drain of the fourth NMOS transistor is connected to the drain of the fifth NMOS transistor, the gate of the sixth NMOS transistor, the drain of the fifth PMOS transistor, and the gate of the sixth PMOS transistor. The sources of the fourth NMOS transistor are connected to the sources of the fifth and sixth NMOS transistors. The gate of the fifth NMOS transistor is connected to the gate of the fifth PMOS transistor. The common terminal of the drain of the sixth NMOS transistor and the drain of the sixth PMOS transistor is connected to the positive terminal of the third diode. The sources of the fourth and sixth PMOS transistors are used to input the current actual operating voltage of the RFID temperature measurement tag. The drain of the fourth PMOS transistor is connected to the source of the fifth PMOS transistor. The negative terminal of the third diode is connected to the output terminal of the optimal impedance matching sample-and-hold circuit through the fourth diode.

[0020] The second matching module includes a third comparator, a seventh NMOS transistor (NM6), an eighth NMOS transistor, a ninth NMOS transistor, a seventh PMOS transistor, an eighth PMOS transistor, a ninth PMOS transistor, a fifth diode, and a sixth diode. The output of the third comparator is connected to the gates of the seventh NMOS transistor and the seventh PMOS transistor. The drain of the seventh NMOS transistor is connected to the drains of the eighth NMOS transistor, the gates of the ninth NMOS transistor, the drains of the eighth PMOS transistor, and the gates of the ninth PMOS transistor. The source of the seventh NMOS transistor is connected to the source of the eighth NMOS transistor. The fifth diode is connected to the source of the ninth NMOS transistor, the gate of the eighth NMOS transistor is connected to the gate of the eighth PMOS transistor, the common terminal of the drain of the ninth NMOS transistor and the drain of the ninth PMOS transistor is connected to the positive terminal of the fifth diode, the source of the seventh PMOS transistor and the source of the ninth PMOS transistor are used to input the current actual operating voltage of the RFID temperature measurement tag, the drain of the seventh PMOS transistor is connected to the source of the eighth PMOS transistor, and the negative terminal of the fifth diode is connected to the output terminal of the optimal impedance matching sample and hold circuit through the sixth diode.

[0021] In a further embodiment, the non-optimal impedance matching operating state is used to detect the energy distance between the reader and the RFID temperature measurement tag and / or the radio frequency energy according to the preset potential disability threshold when the RFID temperature measurement tag receives radio frequency energy generated by the reader, obtain a potential disability detection result, and obtain the current actual operating voltage of the RFID temperature measurement tag according to the energy distance and / or the radio frequency energy based on the potential disability detection result, compare the current actual operating voltage of the tag with the upper limit value and the lower limit value of the external reference voltage respectively, obtain a reference voltage comparison result, and input the reference voltage comparison result as a sample-and-hold output signal into the digital baseband circuit;

[0022] The digital baseband circuit is used to determine whether the preset non-optimal impedance matching condition is met based on the comparison result of the reference voltage. If it is met, a disabling signal is generated; otherwise, the optimal impedance matching working state continues until the impedance value reaches the optimal matching value.

[0023] The adjustable capacitor array module is used to receive a disabling signal generated by the digital baseband circuit when the automatic impedance matching circuit switches from the optimal impedance matching operating state to the non-optimal impedance matching operating state, and adjust the impedance value of the automatic impedance matching circuit or turn off the automatic impedance matching operation of the automatic impedance matching circuit according to the disabling signal.

[0024] In a further implementation, the step of obtaining the potential disability detection result based on the energy distance between the reader and the RFID temperature measurement tag and / or the radio frequency energy according to the preset potential disability threshold is specifically as follows:

[0025] If the detected energy distance is lower than the potential distance disabling threshold and / or the radio frequency energy is higher than the potential energy disabling threshold, it is determined that there is a potential switch of the automatic impedance matching circuit from the optimal impedance matching working state to the non-optimal impedance matching working state, and a corresponding potential disabling detection result is generated; otherwise, it is determined that there is no potential switch of the automatic impedance matching circuit from the optimal impedance matching working state to the non-optimal impedance matching working state.

[0026] Secondly, the present invention provides a temperature measurement method based on RFID temperature measurement tags, using the temperature measurement system based on RFID temperature measurement tags as described above. The temperature measurement method includes the following steps:

[0027] When the RFID temperature measurement tag receives radio frequency energy generated by the reader, based on a preset potential disability threshold, and according to the energy distance between the reader and the RFID temperature measurement tag and / or the radio frequency energy, the current actual operating voltage of the RFID temperature measurement tag is obtained, and a sample-and-hold output signal is generated based on the current actual operating voltage of the tag; the preset potential disability threshold includes a potential distance disability threshold and a potential energy disability threshold;

[0028] A disabling signal is generated based on the sample-and-hold output signal;

[0029] In response to the disability signal, the impedance value is adjusted or the automatic impedance matching operation is turned off according to the disability signal, so that the automatic impedance matching circuit switches from the optimal impedance matching operation state to the non-optimal impedance matching operation state.

[0030] This invention provides a temperature measurement system and method based on RFID temperature measurement tags. The temperature measurement system includes a digital baseband circuit and an automatic impedance matching circuit disposed inside the RFID temperature measurement tag. The automatic impedance matching circuit generates a sample-and-hold output signal based on a preset energy disabling threshold and the detected energy distance and / or radio frequency energy between the reader and the RFID temperature measurement tag when the RFID temperature measurement tag receives radio frequency energy from the reader. This signal enables the digital baseband circuit to generate a disabling signal. In response to the disabling signal, the circuit adjusts its impedance value or shuts down its automatic impedance matching operation, switching the automatic impedance matching circuit from an optimal impedance matching state to a non-optimal impedance matching state. Compared with existing technologies, this temperature measurement system, while ensuring the normal operation of the temperature measurement tag, reduces the energy obtained by the RFID temperature measurement tag from the reader by changing or shutting down the impedance matching network. This improves the accuracy of the temperature measurement tag by reducing the heat generated by the tag itself, reducing its energy consumption, and significantly minimizing the impact of heat generation on temperature measurement accuracy. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the structure of a conventional label temperature measuring device provided in an embodiment of the present invention;

[0032] Figure 2 This is an equivalent circuit model diagram of the interface between the conjugate matched loop antenna and the capacitive load rectifier provided in an embodiment of the present invention;

[0033] Figure 3 This is a block diagram of a temperature measurement system based on RFID temperature measurement tags provided in an embodiment of the present invention;

[0034] Figure 4 This is a circuit diagram of the clock divider module provided in an embodiment of the present invention;

[0035] Figure 5 This is a circuit diagram of the adjustable capacitor array module provided in an embodiment of the present invention;

[0036] Figure 6 This is a schematic diagram of the optimal impedance matching sample-and-hold circuit provided in an embodiment of the present invention;

[0037] Figure 7 This is a schematic diagram of a non-optimal impedance matching sample-and-hold circuit provided in an embodiment of the present invention;

[0038] Figure 8 This is a schematic diagram of the signal flow of the impedance automatic matching circuit provided in the embodiment of the present invention;

[0039] Figure 9This is a schematic diagram of the communication frame between the temperature measuring tag and the reader / writer provided in an embodiment of the present invention;

[0040] Figure 10 This is a schematic diagram of the switching process of the LC impedance matching network provided in the embodiment of the present invention;

[0041] Figure 11 This is a schematic diagram of the temperature measurement method based on RFID temperature measurement tags provided in an embodiment of the present invention. Detailed Implementation

[0042] The embodiments of the present invention are described in detail below with reference to the accompanying drawings. The embodiments are given for illustrative purposes only and should not be construed as limiting the present invention. The accompanying drawings are for reference and illustration only and do not constitute a limitation on the scope of patent protection of the present invention, because many changes can be made to the present invention without departing from the spirit and scope of the present invention.

[0043] When a reader transmits a high-power signal at close range, the temperature-sensing tag chip receives milliwatts or higher of power, generating a significant amount of heat and consequently reducing its temperature measurement accuracy. Reducing the radio frequency energy received by the temperature-sensing tag from the reader can greatly mitigate the impact of this heat generation on measurement accuracy. For example, by… Figure 2 As shown in the equivalent circuit model diagram of the interface between the conjugate matched loop antenna and the capacitive load rectifier, when At this time, the radio frequency energy acquired by the temperature tag chip is at its maximum, and changing the configuration of the impedance matching network can change Z. in The value of the tag can be adjusted to change the energy received by the entire temperature measurement tag chip. Therefore, to minimize the impact of the temperature measurement tag itself on the temperature measurement results and improve measurement accuracy while ensuring the appearance of the temperature measurement tag remains unchanged and it maintains normal operation, this invention provides a temperature measurement system based on an RFID temperature measurement tag. This system can be applied to all products equipped with RFID temperature measurement tags, such as... Figure 3 As shown, the temperature measurement system includes a digital baseband circuit 101 and an automatic impedance matching circuit 102 disposed inside the RFID temperature measurement tag. In this embodiment, the automatic impedance matching circuit includes a clock divider module, an adjustable capacitor array module, a unidirectional tuning module, and a sample-and-hold circuit. The unidirectional tuning module is connected to the adjustable capacitor array module, the clock divider module, and the sample-and-hold circuit.

[0044] The automatic impedance matching circuit is configured to, when the RFID temperature measuring tag receives radio frequency energy generated by the reader, obtain the current actual operating voltage of the RFID temperature measuring tag based on a preset potential disability threshold, the energy distance between the reader and the RFID temperature measuring tag, and / or the radio frequency energy; generate a sample-and-hold output signal based on the current actual operating voltage; and send the sample-and-hold output signal to the digital baseband circuit, so that the digital baseband circuit generates a disability signal based on the sample-and-hold output signal; the preset potential disability threshold includes a potential distance disability threshold and a potential energy disability threshold; and, in response to the disability signal, control the adjustment of its impedance value or the shutdown of its automatic impedance matching operation based on the disability signal, so that the automatic impedance matching circuit switches from the optimal impedance matching operation state to a non-optimal impedance matching operation state.

[0045] Figure 4 This is a circuit diagram of a clock divider module. The clock divider module is used to divide the acquired external clock to generate the real-time clock required by the automatic impedance matching circuit during automatic impedance matching. The sample-and-hold circuit is used to obtain the current actual operating voltage of the RFID temperature measuring tag based on the detected energy distance between the reader and the RFID temperature measuring tag and / or the radio frequency energy. It then processes the current actual operating voltage using either the optimal impedance matching sample-and-hold circuit or the non-optimal impedance matching sample-and-hold circuit to generate a sample-and-hold output signal. This signal is input to the digital baseband circuit or the unidirectional tuning module, so that the digital baseband circuit or the unidirectional tuning module controls the adjustable capacitor array module to adjust the impedance value at both ends of the RFID temperature measuring tag antenna or to turn off the automatic impedance matching operation of the automatic impedance matching circuit based on the sample-and-hold output signal. The main function of the adjustable capacitor array module is to adjust the impedance at both ends of the antenna. Based on the result obtained from the automatic impedance matching circuit, the impedance at both ends of the antenna is adjusted. This embodiment of the invention provides three adjustment bits CO<2:0> for adjusting the impedance from 001 to 111. Figure 5 This is a circuit diagram of an adjustable capacitor array module.

[0046] In this embodiment, the sample-and-hold circuit includes an optimal impedance-matched sample-and-hold circuit and a non-optimal impedance-matched sample-and-hold circuit, such as... Figure 6As shown, the optimal impedance matching sample-and-hold circuit includes a first comparator OP1, a first NMOS transistor NM0, a second NMOS transistor NM1, a third NMOS transistor NM2, a first PMOS transistor PM0, a second PMOS transistor PM1, a third PMOS transistor PM2, a first diode D1, and a second diode D2; wherein, the output terminal of the first comparator OP1 is connected to the gate of the first NMOS transistor and the gate of the first PMOS transistor, and the drain of the first NMOS transistor is connected to the drain of the second NMOS transistor, the gate of the third NMOS transistor, the drain of the second PMOS transistor, and the gate of the third PMOS transistor. The source of an NMOS transistor is connected to the source of the second NMOS transistor and the source of the third NMOS transistor. The gate of the second NMOS transistor is connected to the gate of the second PMOS transistor. The common terminal of the drain of the third NMOS transistor and the drain of the third PMOS transistor is connected to the positive terminal of the first diode. The source of the first PMOS transistor and the source of the third PMOS transistor are used to connect to the actual operating voltage of the current tag. The drain of the first PMOS transistor is connected to the source of the second PMOS transistor. The negative terminal of the first diode is connected to the output terminal of the optimal impedance matching sample-and-hold circuit through the second diode.

[0047] The optimal impedance matching sample-and-hold circuit is used to detect the energy distance between the reader and the RFID temperature measurement tag and / or the radio frequency energy according to the preset potential disability threshold when the RFID temperature measurement tag receives radio frequency energy generated by the reader, obtain a potential disability detection result, and obtain the current actual operating voltage of the RFID temperature measurement tag according to the energy distance and / or the radio frequency energy based on the potential disability detection result. The current actual operating voltage of the tag is compared with the actual operating voltage of the tag in the previous round to generate an optimal impedance voltage comparison result, and the optimal impedance voltage comparison result is used as a sample-and-hold output signal input to the unidirectional tuning module. When the unidirectional tuning module receives the optimal impedance voltage comparison result, it determines whether the preset optimal impedance matching adjustment condition is met according to the optimal impedance voltage comparison result and / or the energy distance. If it is met, a tuning signal is generated according to the optimal impedance voltage comparison result.

[0048] The adjustable capacitor array module is used to receive the tuning signal generated by the unidirectional tuning module and adjust the impedance value of the automatic impedance matching circuit according to the tuning signal. This process is repeated until the unidirectional tuning module generates a target lock flag signal based on the optimal impedance voltage comparison result. The generation conditions of the lock flag signal include: when the optimal impedance voltage comparison result does not meet the preset optimal impedance matching adjustment condition, the current value of the tuning signal output by the unidirectional tuning module is incremented by one until the optimal impedance voltage comparison result meets the optimal matching condition or the current value of the tuning signal is a preset lock value. Then, the unidirectional tuning module generates a target lock flag signal and a target lock control signal, and sends the target lock control signal to the digital baseband circuit.

[0049] like Figure 7 As shown, the non-optimal impedance matching sample-and-hold circuit includes a first matching module and a second matching module. The first matching module includes a second comparator OP2, a fourth NMOS transistor NM3, a fifth NMOS transistor NM4, a sixth NMOS transistor NM5, a fourth PMOS transistor PM3, a fifth PMOS transistor PM4, a sixth PMOS transistor PM5, a third diode D3, and a fourth diode D4. The output of the second comparator is connected to the gate of the fourth NMOS transistor and the gate of the fourth PMOS transistor. The drain of the fourth NMOS transistor is connected to the drain of the fifth NMOS transistor, the gate of the sixth NMOS transistor, the drain of the fifth PMOS transistor, and the sixth PMOS transistor PM5. The gate of the S-channel MOSFET is connected. The source of the fourth NMOS transistor is connected to the source of the fifth NMOS transistor and the source of the sixth NMOS transistor. The gate of the fifth NMOS transistor is connected to the gate of the fifth PMOS transistor. The common terminal of the drain of the sixth NMOS transistor and the drain of the sixth PMOS transistor is connected to the positive terminal of the third diode. The sources of the fourth PMOS transistor and the sixth PMOS transistor are used to input the actual operating voltage of the current tag. The drain of the fourth PMOS transistor is connected to the source of the fifth PMOS transistor. The negative terminal of the third diode is connected to the output terminal of the optimal impedance matching sample-and-hold circuit through the fourth diode.

[0050] The second matching module includes a third comparator OP3, a seventh NMOS transistor NM6, an eighth NMOS transistor NM7, a ninth NMOS transistor NM8, a seventh PMOS transistor PM6, an eighth PMOS transistor PM7, a ninth PMOS transistor PM8, a fifth diode D5, and a sixth diode D6. The output of the third comparator OP3 is connected to the gates of the seventh NMOS transistor and the seventh PMOS transistor. The drain of the seventh NMOS transistor is connected to the drains of the eighth NMOS transistor, the gates of the ninth NMOS transistor, the drains of the eighth PMOS transistor, and the gates of the ninth PMOS transistor. The source of the S-channel MOSFET is connected to the sources of the eighth and ninth NMOS transistors. The gate of the eighth NMOS transistor is connected to the gate of the eighth PMOS transistor. The common terminal of the drain of the ninth NMOS transistor and the drain of the ninth PMOS transistor is connected to the positive terminal of the fifth diode. The sources of the seventh and ninth PMOS transistors are used to connect to the actual operating voltage of the current tag. The drain of the seventh PMOS transistor is connected to the source of the eighth PMOS transistor. The negative terminal of the fifth diode is connected to the output terminal of the optimal impedance matching sample-and-hold circuit through the sixth diode.

[0051] The non-optimal impedance matching operating state is used to detect the energy distance between the reader and the RFID temperature measurement tag and / or the radio frequency energy according to the preset potential disability threshold when the RFID temperature measurement tag receives radio frequency energy generated by the reader, obtain a potential disability detection result, and obtain the current actual operating voltage of the RFID temperature measurement tag according to the energy distance and / or the radio frequency energy based on the potential disability detection result. The current actual operating voltage of the tag is compared with the upper limit and lower limit of the external reference voltage to obtain a reference voltage comparison result, and the reference voltage comparison result is input as a sample-and-hold output signal to the digital baseband circuit. When the digital baseband circuit receives the reference voltage comparison result, it determines whether the preset non-optimal impedance matching condition is met according to the reference voltage comparison result and / or the energy distance. If it is met, a disability signal is generated; otherwise, the optimal impedance matching operating state continues until the impedance value reaches the optimal matching value.

[0052] The adjustable capacitor array module is used to receive a disabling signal generated by the digital baseband circuit when the automatic impedance matching circuit switches from the optimal impedance matching operating state to the non-optimal impedance matching operating state, and adjust the impedance value of the automatic impedance matching circuit or turn off the automatic impedance matching operation of the automatic impedance matching circuit according to the disabling signal.

[0053] In this embodiment, the step of obtaining the potential disability detection result based on the energy distance between the reader and the RFID temperature measurement tag and / or the radio frequency energy according to the preset potential disability threshold is specifically as follows:

[0054] If the detected energy distance is lower than the potential distance disabling threshold and / or the radio frequency energy is higher than the potential energy disabling threshold, it is determined that there is a potential switch of the automatic impedance matching circuit from the optimal impedance matching working state to the non-optimal impedance matching working state, and a corresponding potential disabling detection result is generated; otherwise, it is determined that there is no potential switch of the automatic impedance matching circuit from the optimal impedance matching working state to the non-optimal impedance matching working state.

[0055] When there is a potential switching of the automatic impedance matching circuit from the optimal impedance matching operating state to the non-optimal impedance matching operating state, this embodiment will process the theoretical operating voltage of the RFID temperature measuring tag based on the energy distance between the reader and the RFID temperature measuring tag and / or the radio frequency energy to generate the current actual operating voltage of the RFID temperature measuring tag. For example: when only the energy distance is detected to be lower than the potential distance disabling threshold, the energy distance between the reader and the RFID temperature measuring tag is incorporated as a stability influencing factor into the current theoretical operating voltage of the RFID temperature measuring tag to calculate the current actual operating voltage of the RFID temperature measuring tag; similarly, when only the radio frequency energy is detected to be higher than the potential energy disabling threshold, the radio frequency energy is incorporated as a stability influencing factor into the current theoretical operating voltage of the RFID temperature measuring tag to calculate the current actual operating voltage of the RFID temperature measuring tag; when the energy distance is detected to be lower than the potential distance disabling threshold and the radio frequency energy is higher than the potential energy disabling threshold, the energy distance between the reader and the RFID temperature measuring tag and the radio frequency energy are both incorporated as stability influencing factors into the current theoretical operating voltage of the RFID temperature measuring tag to calculate the current actual operating voltage of the RFID temperature measuring tag.

[0056] To facilitate understanding of the temperature measurement system based on RFID temperature measurement tags proposed in this embodiment, the implementation process will be described in detail below:

[0057] The antenna of the RFID temperature tag receives radio frequency energy generated by the reader. When the received radio frequency energy is sufficient to enable the digital baseband circuit to operate normally, the digital baseband circuit generates enable signals AT_EN and COM_EN to enable the unidirectional tuning module and sample-and-hold circuit to operate normally. The impedance matching circuit receives the enable signals AT_EN and COM_EN from the digital baseband circuit, enabling the entire impedance matching circuit to start working. The clock divider module divides the externally input reference clock to generate a real-time clock for the entire impedance matching network. The clock divider module uses the externally input frequency signal to convert it into the specific frequency required for unidirectional tuning. In this embodiment, the externally input frequency signal is 1.3MHz. The clock divider module uses a D-type flip-flop to perform nine frequency divisions on the line. The subsequent workflow is divided into optimal impedance matching adjustment and non-optimal impedance matching adjustment processes, such as... Figure 8 As shown, the specific working processes of adjusting for optimal impedance matching and non-optimal impedance matching are as follows:

[0058] In the automatic impedance matching circuit, the optimal impedance matching sample-and-hold circuit compares the current tag operating voltage VDDH (operating voltage) with the tag operating voltage collected in the previous round to obtain the optimal impedance voltage comparison result Compout. This optimal impedance voltage comparison result is then used as a sample-and-hold output signal and input to the unidirectional tuning module. The unidirectional tuning module then controls the MOSFETs in the adjustable capacitor array module according to the sample-and-hold output signal, thereby changing the impedance value of the automatic impedance matching circuit. When the optimal impedance voltage comparison result Compout = 1, the current value (default value 001) of the tuning signal CO<2:0> output by the unidirectional tuning module is incremented by one, thus turning on the corresponding MOSFET of the adjustable capacitor array module and adjusting the impedance value of the adjustable capacitor array module. This cycle continues until the optimal impedance voltage comparison result Compout = 0 or the value of the tuning signal CO<2:0> is 111, indicating that the impedance value has reached optimal matching. The unidirectional tuning module generates a target lock flag signal (locked), stopping the automatic impedance matching circuit. Simultaneously, the unidirectional tuning module generates a target lock control signal AT_LOCKED = 1 via the lock signal module and outputs it to the digital baseband circuit. The digital baseband circuit, based on the target lock control signal AT_LOCKED = 1, disables the enable signal AT_EN, ending the automatic impedance matching process. This process is the optimal impedance matching adjustment process. For example, when the optimal impedance voltage comparison result Compout = 1 and the tuning signal CO<2:0> = 111, the unidirectional tuning module outputs the locked signal, making AT_LOCKED become 1, ending the automatic impedance matching. When the optimal impedance voltage comparison result Compout = 0, the value of the tuning signal CO<2:0> remains unchanged, and the unidirectional tuning module outputs the locked signal, making AT_LOCKED become 1, ending the automatic impedance matching. Figure 8 In the diagram, the solid line represents the tuning signal CO<0:2> generated by the unidirectional tuning module, and the dashed line represents the tuning signal generated by the digital baseband circuit.

[0059] In the automatic impedance matching circuit, the adjustment process for non-optimal impedance matching and the adjustment process for optimal impedance matching are performed simultaneously. The non-optimal impedance matching sample-and-hold circuit compares the current tag's actual operating voltage VDDH with the external reference voltage upper limit VH and reference voltage lower limit VL, respectively, to obtain the corresponding reference voltage comparison results Compout1 and Compout2. These reference voltage comparison results are then input as sample-and-hold output signals to the digital baseband circuit. The digital baseband circuit controls the MOS transistors in the adjustable capacitor array module based on the sample-and-hold output signal and / or the energy distance. When Compout1 = 0 and Compout2 = 0, the automatic impedance matching process for optimal impedance matching continues until the optimal matching value is reached. When Compout1 = 0 and Compout2 = 0 changes to Compout1 = 1 and Compout2 = 0, the automatic impedance matching process for optimal impedance matching continues. The automatic impedance matching process of the impedance matching adjustment process continues until the optimal matching value is reached. When the values ​​change from Compout1=1 and Compout2=0 to Compout1=1 and Compout2=1, the digital baseband circuit generates a disabling signal to disable the enable signal AT_EN and lock the target lock control signal AT_LOCKED, thus stopping the automatic impedance matching process of the optimal impedance matching adjustment process. At the same time, the value of the tuning signal CO<2:0> is reduced, which turns on the MOS transistor corresponding to the adjustable capacitor array module and adjusts the impedance value of the automatic impedance matching circuit. The range of the tuning signal CO<2:0> is (001, 111), thereby realizing the adjustment process of non-optimal impedance matching. During the adjustment process of non-optimal impedance matching, the radio frequency energy received by the corresponding temperature tag is reduced and the local temperature does not change much, so it will not have a significant impact on the temperature measurement accuracy of the temperature tag, thus achieving the goal of improving the temperature measurement accuracy of the temperature tag.

[0060] Based on the above two adjustment processes—optimal impedance matching and non-optimal impedance matching—it can be seen that when the reader transmits a relatively large power to the temperature tag at close range, both the optimal and non-optimal impedance matching adjustment processes of the impedance matching network are involved. The non-optimal impedance matching adjustment process involves adjusting the impedance value of the impedance matching network. When it is not working at the optimal matching value, the energy received by the temperature tag is reduced, and the local temperature does not change significantly, thus achieving the goal of improving the temperature measurement accuracy of the temperature tag. When the reader transmits a relatively small power to the temperature tag at a long distance, the adjustment of the impedance matching network may only involve the optimal impedance matching adjustment process. This process will not have a significant impact on the local temperature of the temperature tag, so it remains in the optimal matching process.

[0061] To verify that the temperature measurement system proposed in this embodiment can improve the temperature measurement accuracy of the temperature measurement tag, this embodiment will describe in detail the entire process of the temperature measurement tag from the first entry into the radio frequency field generated by the reader to the first exit from the radio frequency field generated by the reader through an LC impedance matching network. Figure 9 This diagram illustrates the communication frame between the temperature tag and the reader. Assuming the physical positions of the reader and the temperature tag remain unchanged, the reader's transmission power P0 remains constant (i.e., the transmitted energy E0 per unit time is fixed). Under an optimal LC impedance matching network, the temperature tag acquires energy E1 and power P1 per unit time. Changing the impedance matching network, the power acquired becomes P2, making P2 much smaller than P1. Simultaneously, the reader's transmission power is also changed. It should be noted that the reader's transmitted energy E0 per unit time is positively correlated with its transmission power, and the temperature tag's energy E1 per unit time under the same optimal LC impedance matching network is also positively correlated with E0. When the reader operates at its maximum transmission power, the maximum operating voltage generated by the corresponding temperature tag is V1. When the reader operates at the temperature tag's critical operating transmission power, the minimum operating voltage generated by the corresponding temperature tag is V2.

[0062] Regardless of the changes in the position of the temperature tag and the reader, or the changes in the reader's transmission power, the workflow should be as follows: the reader emits radio frequency energy to form a radio frequency field. When the temperature tag is not within the radio frequency field range, its operating voltage is zero. When the temperature tag enters the radio frequency field range, it acquires radio frequency energy through the antenna. At this time, the operating voltage of the temperature tag drops from 0 to its minimum operating voltage, and the temperature tag begins to work normally. At the same time, since the temperature tag has an upper limit operating voltage value, it protects the entire circuit from working normally. When the reader stops emitting radio frequency energy, the operating voltage of the temperature tag will continuously decrease from the current value until it reaches zero.

[0063] Therefore, in this embodiment, two reference voltage points, V3 and V4, are selected between the minimum operating voltage V2 and the maximum operating voltage V1 generated by the temperature measuring tag, such that V1>V3>V4>V2. The selection of V3 needs to ensure that the temperature measuring tag experiences rapid localized heating within a certain timeframe. The value of V4 can be based on the minimum operating voltage. Whether the operating voltage of the temperature measuring tag can reach V3 depends on the amount of radio frequency energy emitted by the reader and the distance between the reader and the temperature measuring tag. If the operating voltage of the temperature measuring tag will never reach V3, this situation does not need to be considered, and the original impedance matching control method is maintained. However, in reality, the operating voltage of the temperature measuring tag easily reaches V3. Therefore, if... Figure 10 As shown, the following LC impedance matching network switching workflow is adopted:

[0064] Step 1: When the reader's transmission power causes the voltage generated by the temperature tag to rise from 0 to V3, record the corresponding time as T1. Reduce the temperature tag's acquisition of radio frequency energy by changing or turning off the LC impedance matching network. At this time, when the temperature tag's operating voltage drops from V3 to V4, record the corresponding time as T2. Then switch the LC impedance matching network back to the optimal LC impedance matching working state and continue to acquire radio frequency energy from the reader.

[0065] Step 2: The working voltage of the temperature tag increases from V4 to V3, and the corresponding time is recorded as T3. Then, the LC impedance matching network is changed or turned off. At this time, the working voltage of the temperature tag drops from V3 to V4, and the corresponding time is recorded as T4. Then, the LC impedance matching network is switched back to the optimal matching network.

[0066] Step 3: Repeat step 2 until the previous cycle ends, when the voltage rises from V4 to V3, and record the corresponding time as T(n-1). When the voltage drops from V3 to V4, record the corresponding time as Tn.

[0067] Therefore, in the above process, when the LC impedance matching network is not switched or turned off, the radio frequency energy obtained by the normal temperature measurement tag is:

[0068] E1=P1*(T1+T2+T3+T4+...+T(n-1)+Tn)

[0069] When the above-described method of switching or turning off the LC impedance matching network is used, the radio frequency energy acquired by the temperature measurement tag in this embodiment is:

[0070] E1 * =P1*(T2+T4+...+Tn)+P2*(T1+T3+...+T(n-1))

[0071] From the two formulas above, we can see that:

[0072] ΔE=E1-E1 * =(P1-P2)*(T1+T3+......+T(n-1))

[0073] As can be clearly seen from the formula for calculating ΔE, when the reader and the temperature tag are close together and the transmission power is relatively high (i.e., the operating voltage of the temperature tag increases rapidly), the local temperature of the temperature tag will rise rapidly without the method proposed in this invention, leading to a decrease in the temperature measurement accuracy. However, by incorporating the method proposed in this embodiment, i.e., the temperature tag switches or turns off the LC impedance matching network as proposed in this embodiment, it can at least reduce the energy of the reader to obtain the ΔE value, that is, reduce the heat energy radiated by the chip itself, thereby improving the temperature measurement accuracy of the temperature tag. At the same time, it can be seen from the formula for calculating ΔE that the energy absorbed by the chip is reduced differently when the impedance matching circuit is adjusted to different values. Among them, directly turning off the impedance matching circuit, i.e., P2=0, reduces the energy absorbed by the chip the most and its own heat dissipation is relatively the least. It should be noted that when the reader and the temperature tag are far apart and the transmission power is relatively low (i.e., the operating voltage of the temperature tag is relatively low and can maintain normal operation), it will not have a significant impact on the local temperature of the temperature tag; it is sufficient to keep the temperature tag working normally.

[0074] The above mainly describes the situation where the reader and the temperature tag are close together and emitting high-power radio frequency energy. This avoids the operating voltage of the temperature tag from reaching a value that would cause a rapid local temperature rise, thereby improving the temperature measurement accuracy of the temperature tag. In the other case mentioned above, the operating voltage of the temperature tag will not reach V3, but will exceed V4. In this case, it is not necessary to adjust the impedance value of the impedance matching network. This situation often occurs when the distance between the temperature tag and the reader is far, and the radio frequency energy emitted by the reader is small enough to meet the normal operation of the temperature tag. In this case, the temperature tag will not cause a rapid local temperature rise, thus affecting the temperature measurement accuracy of the temperature tag.

[0075] Another factor affecting the amount of radio frequency energy acquired by the temperature tag is the distance between the reader and the temperature tag. The position of the reader and the temperature tag also affects the energy acquired by the tag. With a fixed power output from the reader in the same direction, the closer the reader and the temperature tag are, the greater the energy acquired by the tag, resulting in a higher operating voltage and greater localized heat generation, which has a relatively larger impact on the temperature measurement accuracy. Conversely, the farther the reader and the temperature tag are, the less energy acquired by the tag, resulting in a lower operating voltage and less localized heat generation, which has a relatively smaller impact on the temperature measurement accuracy. Based on the above analysis, the distance between the reader and the temperature tag... The distance problem can also be transformed into the problem of the temperature tag's local temperature rising due to the increase or decrease of its operating voltage. The solution can also use the method described above. When the distance between the two is smaller, the operating voltage of the temperature tag is higher. At this time, the impedance matching network of the temperature tag is working in a non-optimal matching state. When the distance is larger, the operating voltage of the temperature tag is lower. At this time, the impedance matching network of the temperature tag is working in an optimal matching state. The workflow is exactly the same as the above process. The above algorithm is based on the fact that when the reader transmits a relatively large power to the temperature tag at close range, the operating voltage of the temperature tag will rise rapidly, and the local temperature of the temperature chip will rise rapidly. This can more vividly illustrate that the temperature tag's local temperature is too high due to receiving too much radio frequency energy, which affects the temperature measurement accuracy of the temperature tag.

[0076] This invention provides a temperature measurement system based on an RFID temperature measurement tag. The system utilizes a digital baseband circuit and an automatic impedance matching circuit within the RFID temperature measurement tag. When the RFID temperature measurement tag receives radio frequency energy generated by a reader, the system controls the digital baseband circuit to generate a disabling signal based on the energy distance between the reader and the RFID temperature measurement tag and / or the radio frequency energy. In response to the disabling signal, the system adjusts its impedance value or shuts down its automatic impedance matching operation, thereby switching the automatic impedance matching circuit from an optimal impedance matching state to a non-optimal impedance matching state. Compared with existing technologies, this temperature measurement system, while ensuring the normal operation of the temperature measurement tag, integrates the influence of energy distance and radio frequency energy between the reader and the RFID temperature measurement tag on the tag's temperature. By adjusting impedance matching, it controls the automatic impedance matching circuit to switch between optimal and non-optimal impedance matching operating states, reducing the radio frequency energy received by the RFID temperature measurement tag from the reader. This significantly reduces the impact of rapid local temperature rise of the temperature measurement tag caused by increased operating voltage due to distance and / or radio frequency energy, which leads to poor temperature measurement accuracy. It solves the problem of excessive local temperature caused by excessive radio frequency energy and / or distance affecting the temperature measurement accuracy of the temperature measurement tag.

[0077] In one embodiment, such as Figure 11 As shown, this embodiment of the invention provides a temperature measurement method based on RFID temperature tags, using the RFID temperature tag-based temperature measurement system described above. The temperature measurement method includes the following steps:

[0078] S1. When the RFID temperature measuring tag receives radio frequency energy generated by the reader, based on a preset potential disability threshold, and according to the energy distance between the reader and the RFID temperature measuring tag and / or the radio frequency energy, the current actual operating voltage of the RFID temperature measuring tag is obtained, and a sample-and-hold output signal is generated based on the current actual operating voltage of the tag; the preset potential disability threshold includes a potential distance disability threshold and a potential energy disability threshold;

[0079] S2. Generate a disabling signal based on the sample-and-hold output signal;

[0080] S3. In response to the disability signal, adjust its impedance value or shut down its automatic impedance matching operation according to the disability signal, so that the automatic impedance matching circuit switches from the optimal impedance matching operation state to the non-optimal impedance matching operation state.

[0081] It should be noted that the sequence number of each process does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0082] For specific limitations regarding the temperature measurement method based on RFID temperature tags, please refer to the above-described limitations regarding the temperature measurement system based on RFID temperature tags, which will not be repeated here. Those skilled in the art will recognize that the various modules and steps described in conjunction with the embodiments disclosed in this application can be implemented in hardware, software, or a combination of both. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0083] This invention provides a temperature measurement method based on an RFID temperature tag. The method comprehensively considers the energy distance and radio frequency energy between the reader and the RFID temperature tag, obtains the current actual operating voltage of the RFID temperature tag, and adjusts its impedance value or disables its automatic impedance matching based on the current actual operating voltage, thereby switching the automatic impedance matching circuit from an optimal impedance matching state to a non-optimal impedance matching state. Compared with existing technologies, this application, while ensuring the normal operation of the temperature tag, comprehensively considers the impact of both the energy distance and radio frequency energy between the reader and the RFID temperature tag on the temperature measurement accuracy. By integrating energy distance and radio frequency energy to adjust the impedance matching state, it reduces the radio frequency energy obtained by the RFID temperature tag from the reader, significantly reducing the impact of the heat generated by the temperature tag itself on the temperature measurement accuracy, and improving the temperature measurement accuracy of the temperature tag when the reader transmits high power at close range.

[0084] The embodiments described above are merely preferred embodiments of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various improvements and substitutions without departing from the technical principles of this invention, and these improvements and substitutions should also be considered within the scope of protection of this application. Therefore, the scope of protection of this patent application should be determined by the scope of the claims.

Claims

1. A temperature measurement system based on RFID temperature measurement tags, characterized in that, include: The digital baseband circuit and automatic impedance matching circuit are installed inside the RFID temperature measurement tag; The automatic impedance matching circuit is used to, when the RFID temperature measuring tag receives radio frequency energy generated by the reader, obtain the current actual operating voltage of the RFID temperature measuring tag based on a preset potential disability threshold, the energy distance between the reader and the RFID temperature measuring tag, and / or the radio frequency energy; generate a sample-and-hold output signal based on the current actual operating voltage of the tag; and send the sample-and-hold output signal to the digital baseband circuit so that the digital baseband circuit generates a disability signal based on the sample-and-hold output signal; the preset potential disability threshold includes a potential distance disability threshold and a potential energy disability threshold; In response to the disability signal, the impedance value is adjusted or the automatic impedance matching operation is turned off according to the disability signal, so that the automatic impedance matching circuit switches from the optimal impedance matching operation state to the non-optimal impedance matching operation state. The automatic impedance matching circuit includes a clock divider module, an adjustable capacitor array module, a unidirectional tuning module, and a sample-and-hold circuit. The unidirectional tuning module is connected to the adjustable capacitor array module, the clock divider module, and the sample-and-hold circuit. The sample-and-hold circuit includes an optimal impedance matching sample-and-hold circuit and a non-optimal impedance matching sample-and-hold circuit. The clock divider module is used to divide the acquired external clock to generate the real-time clock required by the automatic impedance matching circuit during the automatic impedance matching process. The sample-and-hold circuit is used to obtain the current actual operating voltage of the RFID temperature measuring tag based on the detected energy distance between the reader and the RFID temperature measuring tag and / or the radio frequency energy, and to process the current actual operating voltage of the tag using the optimal impedance matching sample-and-hold circuit or the non-optimal impedance matching sample-and-hold circuit to generate a sample-and-hold output signal. The sample-and-hold output signal is then input to the digital baseband circuit or the unidirectional tuning module, so that the digital baseband circuit or the unidirectional tuning module controls the adjustable capacitor array module to adjust the impedance value at both ends of the RFID temperature measuring tag antenna or to turn off the automatic impedance matching operation of the automatic impedance matching circuit according to the sample-and-hold output signal.

2. The temperature measurement system based on RFID temperature measurement tags as described in claim 1, characterized in that: The optimal impedance matching sample-and-hold circuit includes a first comparator, a first NMOS transistor, a second NMOS transistor, a third NMOS transistor, a first PMOS transistor, a second PMOS transistor, a third PMOS transistor, a first diode, and a second diode; In this circuit, the output of the first comparator is connected to the gate of the first NMOS transistor and the gate of the first PMOS transistor. The drain of the first NMOS transistor is connected to the drain of the second NMOS transistor, the gate of the third NMOS transistor, the drain of the second PMOS transistor, and the gate of the third PMOS transistor. The source of the first NMOS transistor is connected to the source of the second NMOS transistor and the source of the third NMOS transistor. The gate of the second NMOS transistor is connected to the gate of the second PMOS transistor. The common terminal of the drain of the third NMOS transistor and the drain of the third PMOS transistor is connected to the positive terminal of the first diode. The sources of the first PMOS transistor and the third PMOS transistor are used to input the current actual operating voltage of the RFID temperature measurement tag. The drain of the first PMOS transistor is connected to the source of the second PMOS transistor. The negative terminal of the first diode is connected to the output of the optimal impedance matching sample-and-hold circuit through the second diode.

3. The temperature measurement system based on RFID temperature measurement tags as described in claim 2, characterized in that: The optimal impedance matching sample-and-hold circuit is used to detect the energy distance between the reader and the RFID temperature measurement tag and / or the radio frequency energy according to the preset potential disability threshold when the RFID temperature measurement tag receives radio frequency energy generated by the reader, obtain a potential disability detection result, and obtain the current actual operating voltage of the RFID temperature measurement tag according to the energy distance and / or the radio frequency energy based on the potential disability detection result. The current actual operating voltage of the tag is compared with the actual operating voltage of the tag in the previous round to generate an optimal impedance voltage comparison result, and the optimal impedance voltage comparison result is input as a sample-and-hold output signal into the unidirectional tuning module. The unidirectional tuning module is used to determine whether the preset optimal impedance matching adjustment condition is met based on the optimal impedance voltage comparison result. If it is met, a tuning signal is generated based on the optimal impedance voltage comparison result. The adjustable capacitor array module is used to receive the tuning signal generated by the unidirectional tuning module, and adjust the impedance value of the automatic impedance matching circuit according to the tuning signal, repeating the cycle until the unidirectional tuning module generates a target lock flag signal according to the optimal impedance voltage comparison result.

4. The temperature measurement system based on RFID temperature measurement tags as described in claim 3, characterized in that, The conditions for generating the target lock signal include: When the optimal impedance voltage comparison result does not meet the preset optimal impedance matching adjustment condition, the current value of the tuning signal output by the unidirectional tuning module is incremented by one until the optimal impedance voltage comparison result meets the optimal matching condition or the current value of the tuning signal is a preset locking value. Then, the unidirectional tuning module generates a target locking flag signal and a target locking control signal, and sends the target locking control signal to the digital baseband circuit.

5. The temperature measurement system based on RFID temperature measurement tags as described in claim 1, characterized in that: The non-optimal impedance matching sample-and-hold circuit includes a first matching module and a second matching module. The first matching module includes a second comparator, a fourth NMOS transistor NM3, a fifth NMOS transistor NM4, a sixth NMOS transistor NM5, a fourth PMOS transistor PM3, a fifth PMOS transistor PM4, a sixth PMOS transistor PM5, a third diode, and a fourth diode. The output of the second comparator is connected to the gates of the fourth NMOS transistor and the fourth PMOS transistor. The drain of the fourth NMOS transistor is connected to the drains of the fifth NMOS transistor, the gates of the sixth NMOS transistor, the drains of the fifth PMOS transistor, and the gates of the sixth PMOS transistor. The source of the fourth NMOS transistor is connected to the source of the fifth NMOS transistor and the source of the sixth NMOS transistor. The gate of the fifth NMOS transistor is connected to the gate of the fifth PMOS transistor. The common terminal of the drain of the sixth NMOS transistor and the drain of the sixth PMOS transistor is connected to the positive terminal of the third diode. The source of the fourth PMOS transistor and the source of the sixth PMOS transistor are used to input the current actual operating voltage of the RFID temperature measurement tag. The drain of the fourth PMOS transistor is connected to the source of the fifth PMOS transistor. The negative terminal of the third diode is connected to the output terminal of the optimal impedance matching sample and hold circuit through the fourth diode. The second matching module includes a third comparator, a seventh NMOS transistor (NM6), an eighth NMOS transistor, a ninth NMOS transistor, a seventh PMOS transistor, an eighth PMOS transistor, a ninth PMOS transistor, a fifth diode, and a sixth diode. The output of the third comparator is connected to the gates of the seventh NMOS transistor and the seventh PMOS transistor. The drain of the seventh NMOS transistor is connected to the drains of the eighth NMOS transistor, the gates of the ninth NMOS transistor, the drains of the eighth PMOS transistor, and the gates of the ninth PMOS transistor. The source of the seventh NMOS transistor is connected to the source of the eighth NMOS transistor. The fifth diode is connected to the source of the ninth NMOS transistor, the gate of the eighth NMOS transistor is connected to the gate of the eighth PMOS transistor, the common terminal of the drain of the ninth NMOS transistor and the drain of the ninth PMOS transistor is connected to the positive terminal of the fifth diode, the source of the seventh PMOS transistor and the source of the ninth PMOS transistor are used to input the current actual operating voltage of the RFID temperature measurement tag, the drain of the seventh PMOS transistor is connected to the source of the eighth PMOS transistor, and the negative terminal of the fifth diode is connected to the output terminal of the optimal impedance matching sample and hold circuit through the sixth diode.

6. The temperature measurement system based on RFID temperature measurement tags as described in claim 5, characterized in that: The non-optimal impedance matching operating state is used to detect the energy distance between the reader and the RFID temperature measurement tag and / or the radio frequency energy according to the preset potential disability threshold when the RFID temperature measurement tag receives radio frequency energy generated by the reader, obtain a potential disability detection result, and obtain the current actual operating voltage of the RFID temperature measurement tag according to the energy distance and / or the radio frequency energy based on the potential disability detection result. The current actual operating voltage of the tag is compared with the upper limit value and the lower limit value of the external reference voltage to obtain the reference voltage comparison result, and the reference voltage comparison result is input into the digital baseband circuit as a sample and hold output signal. The digital baseband circuit is used to determine whether the preset non-optimal impedance matching condition is met based on the comparison result of the reference voltage. If it is met, a disabling signal is generated; otherwise, the optimal impedance matching working state continues until the impedance value reaches the optimal matching value. The adjustable capacitor array module is used to receive a disabling signal generated by the digital baseband circuit when the automatic impedance matching circuit switches from the optimal impedance matching operating state to the non-optimal impedance matching operating state, and adjust the impedance value of the automatic impedance matching circuit or turn off the automatic impedance matching operation of the automatic impedance matching circuit according to the disabling signal.

7. A temperature measurement system based on an RFID temperature tag as described in claim 3 or 6, characterized in that, The step of obtaining the potential disability detection result based on the energy distance between the reader and the RFID temperature measurement tag and / or the radio frequency energy according to the preset potential disability threshold is as follows: If the detected energy distance is lower than the potential distance disabling threshold and / or the radio frequency energy is higher than the potential energy disabling threshold, it is determined that there is a potential switch of the automatic impedance matching circuit from the optimal impedance matching working state to the non-optimal impedance matching working state, and a corresponding potential disabling detection result is generated; otherwise, it is determined that there is no potential switch of the automatic impedance matching circuit from the optimal impedance matching working state to the non-optimal impedance matching working state.

8. A temperature measurement method based on RFID temperature measurement tags, characterized in that, The method of using the temperature measurement system based on RFID temperature measurement tags as described in any one of claims 1 to 7 includes the following steps: When the RFID temperature measurement tag receives radio frequency energy generated by the reader, based on a preset potential disability threshold, and according to the energy distance between the reader and the RFID temperature measurement tag and / or the radio frequency energy, the current actual operating voltage of the RFID temperature measurement tag is obtained, and a sample-and-hold output signal is generated based on the current actual operating voltage of the tag; the preset potential disability threshold includes a potential distance disability threshold and a potential energy disability threshold; A disabling signal is generated based on the sample-and-hold output signal; In response to the disability signal, the impedance value is adjusted or the automatic impedance matching operation is turned off according to the disability signal, so that the automatic impedance matching circuit switches from the optimal impedance matching operation state to the non-optimal impedance matching operation state.

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