CN102722747A - RFID label with thermosensitive device, RFID system and temperature detection method - Google Patents

Abstract

The invention provides an RFID (radio frequency identification card) label with a thermosensitive device, an RFID system and a temperature detection method. The thermosensitive device and an antenna of the RFID label form a parallel connection structure, a logic circuit for controlling connection/disconnection and a voltage-resistance conversion device are arranged on a line where the thermosensitive device is connected with a chip of the RFID label, the connected line, the logic circuit for controlling connection/disconnection, and the voltage-resistance conversion device are one part of the chip; when the logic circuit is disconnected, the thermosensitive device is not connected with the antenna in parallel, and both a first resonant frequency and the signal strength of the antenna are kept unchanged when the antenna is placed at a certain temperature; when the logic circuit is connected, the thermosensitive device is connected with the antenna in parallel, at this time, the antenna is placed at the certain temperature and works at a second resonant frequency; the RFID label receives an instruction sent by an RFID reader to control the connection/disconnection of the logic circuit, so that the temperature change is detected by comparing differences of strengths of signals from the antennas at different frequencies at lower cost.

Description

An RFID tag with a temperature-sensitive device, an RFID system, and a temperature detection method

technical field

The invention relates to the technical field of RFID (Radio Frequency Identification, radio frequency identification), in particular to an RFID tag with a temperature sensitive device, an RFID system and a temperature detection method.

Background technique

In recent years, RFID systems have become increasingly common. RFID systems are mainly used for the identification of people and objects. Generally, the system includes at least one RFID reader, which can transmit and receive radio frequency signals from one or more RFID tags within a set range. The RFID tag is usually encapsulated and can be attached to an object, and it includes a microchip that communicates with the antenna. The microchip is generally an integrated circuit that stores and processes information, modulates and demodulates radio frequency signals, and performs other specialized functions. An RFID tag's antenna is used to receive and transmit radio frequency signals, and is usually adapted to a specific frequency.

In some facilities, RFID systems with temperature-sensitive devices have been used to monitor when the temperature of the product's environment exceeds acceptable temperatures. Typically these devices require a continuous power source for the sensing device to detect temperature changes, but this adds to the cost of the device. In addition, some devices require the sensing device to be connected with a comparator circuit to detect the degree of deviation from the reference voltage, which greatly increases the cost of the device. In summary, there is a need for improved RFID systems that can detect temperature changes without using a continuous energy source or using a low-cost additional circuit.

Contents of the invention

Embodiments of the present invention provide an RFID tag with a temperature sensitive device, an RFID system, and a temperature detection method to detect temperature changes at a relatively low cost.

On the one hand, the embodiment of the present invention provides an RFID tag with a temperature-sensitive device. There are two pins on the chip of the RFID tag; The antenna of the tag forms a parallel structure, and changes in the external temperature will cause changes in the voltage or current at both ends of the temperature-sensitive device. There is a logic circuit for controlling on-off and a voltage on the line connecting the temperature-sensitive device to the chip of the RFID tag. - resistance conversion means, the connecting line, the logic circuit and the voltage-resistance conversion means are part of the chip, the voltage-resistance conversion means is used to convert the change of voltage or current across the temperature sensitive device into a change of resistance, logic The on-off of the circuit determines whether the temperature-sensitive device is connected in parallel with the antenna: when the logic circuit is disconnected, the temperature-sensitive device is not connected in parallel with the antenna. At this time, it is placed at a certain temperature, and the first resonant frequency and signal strength of the antenna remain the same. change; when the logic circuit is connected, the temperature-sensitive device is connected in parallel with the antenna, and at this time it is placed at a certain temperature, at least one of the characteristic frequency and signal strength of the antenna will change, and the antenna works at the second resonance frequency. ; The RFID tag receives the instructions sent by the RFID reader to control the on-off of the logic circuit, so as to detect the change of temperature by comparing the difference between the signal strengths of different frequencies from the antenna.

Optionally, in an embodiment of the present invention, the antenna of the RFID tag is a monopole antenna.

Optionally, in an embodiment of the present invention, the antenna of the RFID tag is a double dipole antenna: the temperature-sensitive device and the voltage-resistance conversion device connected to the temperature-sensitive device form a parallel structure with one of the antennas ; or the temperature sensitive device and the voltage-resistance conversion device connected to the temperature sensitive device form a parallel structure with two antennas at the same time.

Optionally, in an embodiment of the present invention, the voltage-resistance conversion device includes: a device for converting a variable voltage into a variable resistance, or a trench type field effect transistor, or an equivalent circuit of a field effect transistor, The temperature-sensitive device includes: a thermocouple temperature-sensitive device, a semiconductor temperature-sensitive device, a PN crystal temperature-sensitive device, a transistor temperature-sensitive device, a thyristor temperature-sensitive device, and an integrated temperature-sensitive device.

On the other hand, the embodiment of the present invention provides an RFID tag with a temperature-sensitive device. There is a pin on the chip of the RFID tag; one end of the temperature-sensitive device is connected to the pin, and the other end is connected to the pin. On the antenna of the above-mentioned RFID tag, and form a parallel structure with the antenna, the change of the external temperature will cause the change of the voltage or current at both ends of the temperature-sensitive device. The disconnected logic circuit and a voltage-resistance conversion device, the connected circuit, the logic circuit and the voltage-resistance conversion device are part of the chip, and the voltage-resistance conversion device is used to convert the change of voltage or current across the temperature-sensitive device Converted into a change in resistance, the on-off of the logic circuit determines whether the temperature-sensitive device is connected in parallel with the antenna: when the logic circuit is disconnected, the temperature-sensitive device is not connected in parallel with the antenna. The resonant frequency and signal strength remain unchanged; when the logic circuit is connected, the temperature-sensitive device is connected in parallel with the antenna, and at this time it is placed at a certain temperature, at least one of the characteristic frequency and signal strength of the antenna will change. At this time, the antenna Working at the second resonance frequency; the RFID tag receives instructions sent by the RFID reader to control the on-off of the logic circuit, so as to detect the change of temperature by comparing the difference between the signal strengths of different frequencies from the antenna.

Optionally, in an embodiment of the present invention, the antenna of the RFID tag is a monopole antenna.

Optionally, in an embodiment of the present invention, the antenna of the RFID tag is a double dipole antenna: the temperature-sensitive device and the voltage-resistance conversion device connected to the temperature-sensitive device form a parallel structure with one of the antennas ; or the temperature sensitive device and the voltage-resistance conversion device connected to the temperature sensitive device form a parallel structure with two antennas at the same time.

Optionally, in an embodiment of the present invention, the voltage-resistance conversion device includes: a device for converting a variable voltage into a variable resistance, or a trench type field effect transistor, or an equivalent circuit of a field effect transistor, The temperature-sensitive device includes: a thermocouple temperature-sensitive device, a semiconductor temperature-sensitive device, a PN crystal temperature-sensitive device, a transistor temperature-sensitive device, a thyristor temperature-sensitive device, and an integrated temperature-sensitive device.

In yet another aspect, an embodiment of the present invention provides an RFID tag with a temperature-sensitive device. The temperature-sensitive device is connected to the antenna of the RFID tag and forms a parallel structure with the antenna. Changes in the external temperature will cause temperature-sensitive The change of the voltage or current at both ends of the device, there is a logic circuit for controlling on-off and a voltage-resistance conversion device on the line connecting the temperature-sensitive device and the antenna, the connected line, the logic circuit and the voltage-resistance The conversion device is a part of the chip. The voltage-resistance conversion device is used to convert the change of voltage or current across the temperature sensitive device into a change of resistance. The on-off of the logic circuit determines whether the temperature-sensitive device is connected in parallel with the antenna: when the logic circuit is off When it is turned on, the temperature sensitive device is not connected in parallel with the antenna. At this time, it is placed at a certain temperature, and the first resonant frequency and signal strength of the antenna remain unchanged; when the logic circuit is connected, the temperature sensitive device is connected in parallel with the antenna. At this time Placed at a certain temperature, at least one of the characteristic frequency and signal strength of the antenna will change, and the antenna works at the second resonance frequency; the RFID tag receives instructions sent by the RFID reader to control the communication of the logic circuit. This enables detection of changes in temperature by comparing the difference between the signal strengths of different frequencies from the antenna.

Optionally, in an embodiment of the present invention, the antenna of the RFID tag is a monopole antenna.

Optionally, in an embodiment of the present invention, the antenna of the RFID tag is a double dipole antenna: the temperature-sensitive device and the voltage-resistance conversion device connected to the temperature-sensitive device form a parallel structure with one of the antennas ; or the temperature sensitive device and the voltage-resistance conversion device connected to the temperature sensitive device form a parallel structure with two antennas at the same time.

Optionally, in an embodiment of the present invention, the voltage-resistance conversion device includes: a device for converting a variable voltage into a variable resistance, or a trench type field effect transistor, or an equivalent circuit of a field effect transistor, The temperature-sensitive device includes: a thermocouple temperature-sensitive device, a semiconductor temperature-sensitive device, a PN crystal temperature-sensitive device, a transistor temperature-sensitive device, a thyristor temperature-sensitive device, and an integrated temperature-sensitive device.

In yet another aspect, an embodiment of the present invention provides an RFID system with a temperature-sensitive device, the RFID system includes an RFID tag and an RFID reader, and the RFID tag includes the above-mentioned RFID tag with a temperature-sensitive device; the RFID reader The controller sends instructions to control the on-off of the logic circuit of the RFID tag, thereby detecting the change of temperature by comparing the difference between the signal strengths of different frequencies from the antenna.

In yet another aspect, an embodiment of the present invention provides a temperature detection method for an RFID system with a temperature-sensitive device. The temperature detection method is applied to the above-mentioned RFID system with a temperature-sensitive device, including: sending instructions through the RFID reader To control the on-off of the logic circuit of the RFID tag; receive the instructions sent by the RFID reader through the RFID tag to control the on-off of the logic circuit: when the logic circuit is disconnected, the temperature-sensitive device is not connected in parallel with the antenna, and is placed at a certain At a certain temperature, the first resonant frequency and signal strength of the antenna remain unchanged; when the logic circuit is connected, the temperature-sensitive device is connected in parallel with the antenna. At this time, it is placed at a certain temperature, and the characteristic frequency and signal strength of the antenna are at least There will be a change where the antenna is operating at a second resonant frequency; the change in temperature is detected by comparing the difference between the signal strengths of different frequencies from the antenna with the RFID reader.

The above-mentioned technical scheme has the following beneficial effects: because the temperature-sensitive device and the antenna of the RFID tag are used to form a parallel structure, there is a logic circuit for controlling on-off and a voltage-resistance conversion device on the circuit connecting the temperature-sensitive device and the chip of the RFID tag , the connected line, the logic circuit and the voltage-resistance conversion device are part of the chip: when the logic circuit is disconnected, the temperature-sensitive device is not connected in parallel with the antenna, and it is placed at a certain temperature at this time, and the first part of the antenna The resonant frequency and signal strength remain unchanged; when the logic circuit is connected, the temperature sensitive device is connected in parallel with the antenna, and is placed at a certain temperature at this time, and the antenna works at the second resonant frequency; the RFID tag receives the RFID reader The instruction sent is to control the on-off of the logic circuit, so as to realize the technical means of detecting the change of temperature by comparing the difference between the signal strengths of different frequencies from the antenna, so it can achieve the technical effect of detecting temperature change at a lower cost , and use the energy obtained by RFID to solve the power supply problem of temperature detection.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only These are some embodiments of the present invention. Those skilled in the art can also obtain other drawings based on these drawings without creative work.

Fig. 1 is the schematic diagram that the temperature sensitive device of the embodiment of the present invention is connected with RFID label chip;

Fig. 2 is the equivalent circuit diagram of the internal antenna of the RFID tag chip;

Fig. 3 is the schematic diagram that the temperature sensitive device of the embodiment of the present invention, logical switch and voltage-resistance conversion device are connected with the antenna equivalent circuit inside RFID tag chip;

Fig. 4 is the schematic diagram that the temperature sensitive device of the embodiment of the present invention is directly connected with the RFID tag antenna;

Figure 5.1-Figure 5.2 is a structural illustration of the temperature-sensitive device of the embodiment of the present invention;

FIG. 6 is a flowchart of a temperature detection method based on signal strength according to an embodiment of the present invention.

Detailed ways

The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some, not all, embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

There are at least three situations in which the temperature-sensitive device in the embodiment of the present invention is connected to the chip of the RFID tag:

Two-pin structure:

The present invention is a device, system and technique for detecting temperature changes. The system consists of a tag with two pins on the chip. The temperature sensitive device is connected to these two pins, forming a parallel structure with the antenna. Changes in external temperature will cause changes in voltage or current across the temperature-sensitive device. There is a logic circuit for controlling on-off and a voltage-resistance conversion device on the circuit connecting the pin and the chip, and the connected circuit, the logic circuit for controlling on-off and the voltage-resistance conversion device are part of the chip. The function of the voltage-resistance conversion device is to convert the change of voltage or current across the temperature-sensitive device into a change of resistance.

The on-off of the logic circuit determines whether the temperature-sensitive device is connected in parallel with the antenna. When the logic circuit is disconnected, the temperature sensitive device is not connected in parallel with the antenna. At this time, the temperature-sensitive device is placed at a certain temperature, and the first resonant frequency and signal strength of the antenna remain unchanged. When the logic circuit is turned on, the temperature-sensitive device is connected in parallel with the antenna. At this time, it is placed at a certain temperature. At least one of the characteristic frequency and signal strength of the antenna will change. At this time, the antenna works at the second resonance frequency. The reader can send instructions to the tag to control the on-off of the logic circuit. When the logic circuit is turned on, the temperature change can be detected by comparing the difference between the signal strengths of different frequencies from the antenna.

As an example, the system consists of a tag with only one antenna (monopole antenna). There are two pins on the chip of this tag. The temperature sensitive device is connected to these two pins, forming a parallel structure with the antenna. There is a logic circuit for controlling on-off and a voltage-resistance conversion device on the circuit connecting the pin and the chip, and the connected circuit, the logic circuit for controlling on-off and the voltage-resistance conversion device are part of the chip. The function of the voltage-resistance conversion device is to convert the change of voltage or current across the temperature-sensitive device into a change of resistance.

When the logic circuit is turned on and the temperature sensitive device is placed at a certain temperature, at least one of the characteristic frequency and signal strength of the antenna will change, and it works at the second resonance frequency. The reader can send commands to the tag, and can detect the temperature change by comparing the difference between the signal strength of different frequencies when the logic circuit is turned on and off. More precisely, the voltage-resistance conversion device may be a device for converting a variable voltage into a variable resistance, a trench field effect transistor or an equivalent circuit of a field effect transistor. Specific examples of temperature-sensitive devices include: thermocouple temperature-sensitive devices, semiconductor temperature-sensitive devices, PN crystal temperature-sensitive devices, transistor temperature-sensitive devices, thyristor temperature-sensitive devices, integrated temperature-sensitive devices, and the like.

As another example, the system includes a tag with two antennas (dual dipole antenna). There are two situations at this point. In the first case, the temperature sensitive device is connected to these two pins, forming a parallel structure with the first antenna. There is a logic circuit for controlling on-off and a voltage-resistance conversion device on the circuit connecting the pin and the chip, and the connected circuit, the logic circuit for controlling on-off and the voltage-resistance conversion device are part of the chip. The function of the voltage-resistance conversion device is to convert the change of voltage or current across the temperature-sensitive device into a change of resistance. At this time, the voltage-resistance conversion device connected to the temperature sensitive device is also connected in parallel with the first antenna, while the second antenna always communicates normally at the first resonance frequency.

When the logic circuit is turned on and placed at a certain temperature, at least one of the characteristic frequency and signal strength of the first antenna will change, and the first antenna works at the second resonance frequency. The reader is able to send commands to the tag and detect the change in temperature by comparing the difference between the signal strengths of the different frequencies of the first and second antennas when the logic circuit is switched on. Changes in temperature can also be detected by comparing the difference in signal strength at different frequencies when the logic circuit of the second antenna itself is switched on and off.

In the second case, the temperature-sensitive device is connected to these two pins, forming a parallel structure with the two antennas at the same time. There is a logic circuit for controlling on-off and a voltage-resistance conversion device on the circuit connecting the pin and the chip, and the connected circuit, the logic circuit for controlling on-off and the voltage-resistance conversion device are part of the chip. The function of the voltage-resistance conversion device is to convert the change of voltage or current across the temperature-sensitive device into a change of resistance. At this time, the voltage-resistance conversion device connected to the temperature-sensitive device is also connected in parallel with the two antennas, which is similar to the case where the tag only has one antenna.

When the logic circuit is turned on and placed at a certain temperature, at least one of the characteristic frequency and the signal strength of the antenna will change, and the antenna works at the second resonant frequency. The reader can send commands to the tag, and can detect the temperature change by comparing the difference between the signal strength of different frequencies when the logic circuit is turned on and off. In the first case, the circuit connection is relatively simple, and the resonant frequencies of the two antennas may be different during operation, which will affect the measurement accuracy. In the second case, the circuit connection is more complicated, but the resonant frequency of the two antennas is the same during operation, and the measurement accuracy is higher. More precisely, the voltage-resistance conversion device may be a device for converting a variable voltage into a variable resistance, a trench field effect transistor or an equivalent circuit of a field effect transistor. Specific examples of temperature-sensitive devices include: thermocouple temperature-sensitive devices, semiconductor temperature-sensitive devices, PN crystal temperature-sensitive devices, transistor temperature-sensitive devices, thyristor temperature-sensitive devices, integrated temperature-sensitive devices, and the like.

One pin structure:

The chip of the tag may have only one pin, and this pin is externally connected to one end of the temperature-sensitive device, and the other end of the temperature-sensitive device is directly connected to the antenna. The connection point of the pin inside the chip is similar to that of the two pins, and the purpose of parallel connection with the antenna is still to be achieved in the end. At the same time, there is a logic circuit for controlling on-off on the line connecting the pins to the internal circuit of the chip. In addition, a voltage-resistance conversion device is connected in parallel to the circuit of the antenna, and the voltage-resistance conversion device has lines connected to the temperature-sensitive device and the two ends of the logic circuit.

When the logic circuit is disconnected, the temperature-sensitive device is not connected in parallel with the antenna, and it is placed at a certain temperature at this time, and the first resonant frequency and signal strength of the antenna remain unchanged. When the logic circuit is turned on, the temperature-sensitive device is connected in parallel with the antenna. At this time, it is placed at a certain temperature. At least one of the characteristic frequency and signal strength of the antenna will change, and it works at the second resonance frequency. The reader can send instructions to the tag to control the on-off of the logic circuit. When the logic circuit is turned on, the temperature change can be detected by comparing the difference between the signal strengths of different frequencies from the antenna.

As an example, the system consists of a tag with only one antenna (monopole antenna). The temperature-sensitive device is connected to this pin, and the other end of the temperature-sensitive device is directly connected to the antenna, forming a parallel structure with the antenna. There is a logic circuit for controlling on-off and a voltage-resistance conversion device on the circuit connecting the pin and the chip, and the connected circuit, the logic circuit for controlling on-off and the voltage-resistance conversion device are part of the chip. The function of the voltage-resistance conversion device is to convert the change of voltage or current across the temperature-sensitive device into a change of resistance.

When the logic circuit is turned on and placed at a certain temperature, at least one of the characteristic frequency and the signal strength of the antenna will change, and the antenna works at the second resonant frequency. The reader can send commands to the tag, and can detect the temperature change by comparing the difference between the signal strength of different frequencies when the logic circuit is turned on and off. More precisely, the voltage-resistance conversion device may be a device for converting a variable voltage into a variable resistance, a trench field effect transistor or an equivalent circuit of a field effect transistor. Specific examples of temperature-sensitive devices include: thermocouple temperature-sensitive devices, semiconductor temperature-sensitive devices, PN crystal temperature-sensitive devices, transistor temperature-sensitive devices, thyristor temperature-sensitive devices, integrated temperature-sensitive devices, and the like.

As another example, the system includes a tag with two antennas (dual dipole antenna). The temperature-sensitive device is connected to each pin, and the other end of the temperature-sensitive device is directly connected to the antenna, forming a parallel structure with the first antenna. There is a logic circuit for controlling on-off and a voltage-resistance conversion device on the circuit connecting the pin and the chip, and the connected circuit, the logic circuit for controlling on-off and the voltage-resistance conversion device are part of the chip. The function of the voltage-resistance conversion device is to convert the change of voltage or current across the temperature-sensitive device into a change of resistance. At this time, the voltage-resistance conversion device connected to the temperature sensitive device is also connected in parallel with the first antenna, while the second antenna always communicates normally at the first resonance frequency.

When the logic circuit is turned on, placed at a certain temperature, and the first antenna operates at the second resonance frequency, at least one of its characteristic frequency and signal strength will change. The reader is able to send commands to the tag and detect the change in temperature by comparing the difference between the signal strengths of the different frequencies of the first and second antennas when the logic circuit is switched on. Changes in temperature can also be detected by comparing the difference between the signal strengths of different frequencies when the logic circuit of the first antenna itself is turned on and off. More precisely, the voltage-resistance conversion device may be a device for converting a variable voltage into a variable resistance, a trench field effect transistor or an equivalent circuit of a field effect transistor. Specific examples of temperature-sensitive devices include: thermocouple temperature-sensitive devices, semiconductor temperature-sensitive devices, PN crystal temperature-sensitive devices, transistor temperature-sensitive devices, thyristor temperature-sensitive devices, integrated temperature-sensitive devices, and the like.

No lead structure:

When there are no pins on the chip of the RFID tag, the temperature sensitive device can be directly connected to the antenna. The temperature sensitive device and the antenna form a parallel structure. There is a logic circuit for controlling on-off and a voltage-resistance conversion device on the circuit connecting the antenna and the chip, and the connected circuit, the logic circuit for controlling on-off and the voltage-resistance conversion device are part of the chip. The function of the voltage-resistance conversion device is to convert the change of voltage or current across the temperature-sensitive device into a change of resistance. In this case, the antenna connected to the temperature sensitive device cannot communicate at the first resonant frequency apart from the temperature sensitive device. When placed at a certain temperature, at least one of the antenna's second resonant frequency and signal strength changes. The reader can send commands to the tag device to detect changes in temperature by comparing the difference between the signal strengths of different frequencies from the antenna.

As an example, the system consists of a tag with two antennas (dual dipole antenna). The temperature sensitive device is directly connected to the first antenna. The temperature sensitive device and the antenna form a parallel structure. There is a logic circuit for controlling on-off and a voltage-resistance conversion device on the circuit connecting the antenna and the chip, and the connected circuit, the logic circuit for controlling on-off and the voltage-resistance conversion device are part of the chip. The function of the voltage-resistance conversion device is to convert the change of voltage or current across the temperature-sensitive device into a change of resistance. However, the second antenna always communicates normally at the first resonance frequency when it is not connected with the temperature-sensitive device. When placed at a certain temperature, at least one of the characteristic frequency and signal strength of the first antenna will change, and it works at the second resonance frequency, while the characteristic frequency and signal strength of the second antenna will not change. The reader is able to send commands to the tag and detect temperature changes by comparing the difference between the signal strengths of the first and second antennas at different frequencies. More precisely, the voltage-resistance conversion device may be a device for converting a variable voltage into a variable resistance, a trench field effect transistor or an equivalent circuit of a field effect transistor. Specific examples of temperature-sensitive devices include: thermocouple temperature-sensitive devices, semiconductor temperature-sensitive devices, PN crystal temperature-sensitive devices, transistor temperature-sensitive devices, thyristor temperature-sensitive devices, integrated temperature-sensitive devices, and the like.

By extension, the antenna chip may or may not have pins, and may have one pin or multiple pins. The number of antennas can be one, two or even multiple. Correspondingly, one or more temperature-sensitive devices can also be connected, and the models of the temperature-sensitive devices can be the same or different. In addition, the voltage-to-resistance conversion device connected thereto can also have many variations. In one embodiment of the device, at least one of the resonant frequency and the signal strength of the antenna associated with the temperature sensitive device changes when placed at a certain temperature. The reader can send commands to the tag device to detect changes in temperature by comparing the difference between the signal strengths of different frequencies from the antenna.

For an embodiment of a temperature sensitive device, the method of simultaneously comparing values includes comparing the compared values to a majority signal strength value. These signal strength values belong to different frequencies and are related to most temperatures, while the strength of the temperature can be detected based on the above-mentioned comparison.

However, in another aspect, an RFID system includes an RFID tag device and an RFID reader device. This RFID tag device is used to transmit two kinds of signals, namely the signal when the logic circuit is off and the signal when the logic circuit is on, at least one of these two signals will respond to the received request. The RFID reader device is configured to send at least one request to the RFID tag device. The reading device is installed to receive comparison values from the tag between the signal strength values when the logic circuit is on and the signal strength values when the logic circuit is off, and convert these comparison values into different levels of temperature.

In one example, the antenna of the RFID tag is connected to the temperature-sensitive device, and there is a logic circuit for controlling on-off on this connecting line. The temperature sensitive device and the antenna form a parallel structure. There is a logic circuit for controlling on-off and a voltage-resistance conversion device on the circuit connecting the antenna and the chip, and the connected circuit, the logic circuit for controlling on-off and the voltage-resistance conversion device are part of the chip. The function of the voltage-resistance conversion device is to convert the change of voltage or current across the temperature-sensitive device into a change of resistance. In the two situations of whether the logic circuit is on or off, the antenna has two different frequencies corresponding thereto, that is, the first resonant frequency and the second resonant frequency. When the logic circuit is switched on and the tag device is placed at a certain temperature, different signal strength values will be generated due to the change of the resonant frequency.

In one example, the RFID tag device includes first and second antennas. Even better, the first antenna is connected to the temperature sensitive device and the voltage-resistance conversion device. When this tag device is placed at a certain temperature, due to the change of the resonance frequency, the second signal strength value and The difference of the first signal strength value.

In yet another aspect, an embodiment of the present invention provides an RFID system with a temperature-sensitive device, the RFID system includes an RFID tag and an RFID reader, and the RFID tag includes the above-mentioned RFID tag with a temperature-sensitive device; the RFID reader The controller sends instructions to control the on-off of the logic circuit of the RFID tag, thereby detecting the change of temperature by comparing the difference between the signal strengths of different frequencies from the antenna.

In yet another aspect, an embodiment of the present invention provides a temperature detection method for an RFID system with a temperature-sensitive device. The temperature detection method is applied to the above-mentioned RFID system with a temperature-sensitive device, including: sending instructions through the RFID reader To control the on-off of the logic circuit of the RFID tag; receive the instructions sent by the RFID reader through the RFID tag to control the on-off of the logic circuit: when the logic circuit is disconnected, the temperature-sensitive device is not connected in parallel with the antenna, and is placed at a certain At a certain temperature, the first resonant frequency and signal strength of the antenna remain unchanged; when the logic circuit is connected, the temperature-sensitive device is connected in parallel with the antenna. At this time, it is placed at a certain temperature, and the characteristic frequency and signal strength of the antenna are at least There will be a change where the antenna is operating at a second resonant frequency; the change in temperature is detected by comparing the difference between the signal strengths of different frequencies from the antenna with the RFID reader.

As shown in FIG. 1 , it is a schematic diagram of a temperature-sensitive label 10 in which a temperature-sensitive device is connected to an RFID label chip according to an embodiment of the present invention. As shown in FIG. 1 , the tag device 10 includes a base 15 , an integrated circuit board 13 , two pins 16 , 17 and a double dipole antenna 11 , 12 . There are two pins 16 and 17 on the integrated circuit board 13, and these two pins are connected to the temperature sensitive device 14 outwardly, and these two pins are connected in parallel with the equivalent circuit of the antenna inside the chip, and on the connected circuit There is a logic circuit that controls on-off. The temperature sensitive device and the antenna form a parallel structure. There is a logic circuit for controlling on-off and a voltage-resistance conversion device on the circuit connecting the antenna and the chip, and the connected circuit, the logic circuit for controlling on-off and the voltage-resistance conversion device are part of the chip. The function of the voltage-resistance conversion device is to convert the change of voltage or current across the temperature-sensitive device into a change of resistance. Whether the temperature-sensitive device is connected to the chip circuit can be controlled through the on-off of the logic circuit, thereby affecting the frequency of the antenna connected to the radio frequency module. When the logic circuit is off, the tag antenna communicates at the first resonant frequency. When the logic circuit is turned on, placed at a certain temperature, and the antenna works at the second resonance frequency, at least one of its characteristic frequency and signal strength will change.

In one example, the transmitter antennas 11, 12 are made of one or more different low-resistance materials with high conductivity, such as copper, silver, and aluminum, which are similar to the above-mentioned temperature-sensitive The device is connected to the antennas 11 and 12 through two pins 16 and 17. When the antennas 11 and 12 are placed at a certain temperature, the temperature-sensitive device will cause the resonance frequency of one or more transmitting ends to change. The frequency of this change is not the same as the frequency of reception and transmission. For example, when the logic circuit is turned on and the temperature sensitive device is placed at a certain temperature, at least one of the transmitting frequency and the receiving frequency will change.

In another example, the antenna frequency value is initially set higher than the antenna frequency at a certain temperature environment, and then when a certain temperature is reached, it is lowered. In another example, the antenna frequency is initially set lower than the antenna frequency at a certain temperature, and it is increased when a certain temperature is reached. Such temperature-sensitive devices that can be used in the present invention include: thermocouple temperature-sensitive devices, semiconductor temperature-sensitive devices, PN crystal temperature-sensitive devices, transistor temperature-sensitive devices, thyristor temperature-sensitive devices, integrated temperature-sensitive devices, and the like.

Depending on the type of the temperature sensitive device, the resulting temperature change may be a specific temperature value or a selective range of temperature values. The length of time will inevitably lead to changes in the resonant frequency of the antenna, and the quality of the antenna will also cause different changes. For example, the type of temperature sensitive device on the antenna can affect how long it takes to change the resonant frequency of the antenna.

As shown in Figure 2, it is an equivalent circuit diagram of the RFID tag antenna. When the tag coil antenna enters the alternating magnetic field generated by the reader, the interaction between the tag antenna and the reader antenna is similar to a transformer. The coils of both are equivalent to the primary and secondary coils of the transformer. The resonant circuit formed by the tag antenna is shown in Figure 2, including the coil inductance (L), parasitic capacitance (Cp) and parallel capacitance (C2) of the tag antenna, and its resonant frequency is In the formula, C is the parallel equivalent capacitance of Cp and C2, and R1 and R2 are the equivalent resistance of the inductance coil and other devices in the circuit. The carrier frequency used for two-way communication between the tag and the reader is f. When the tag antenna coil is required to have a small shape, that is, a small area, and a certain working distance is required, the mutual inductance of the antenna coil between the RFID tag and the reader obviously cannot meet the actual needs, and a high magnetic permeability can be inserted inside the tag antenna coil. The ferrite material is used to increase the mutual inductance, thereby compensating the problem of small cross-section of the coil.

式C为Cp和C2的并联等效电容，R1，R2为电路内电感线圈及其他装置的等效电阻。M为代表温敏装置的可变电阻，S为控制通断的逻辑电路，R3为与温敏装置串联的等效电阻，F为电压-电阻转换装置。当逻辑电路断开时，温敏装置不与天线并联，此时被放置在一定的温度下，天线的第一共振频率和信号强度保持不变。当逻辑电路接通时，温敏装置与天线并联，此时被放置在一定的温度下，天线特征频率和信号强度至少会有一个发生变化，此时天线工作在第二共振频率下。As shown in FIG. 3 , it is a schematic diagram of the connection between the temperature sensitive device, the logic circuit for controlling on-off and the voltage-resistance conversion device of the embodiment of the present invention and the equivalent circuit of the RFID tag antenna. The resonant circuit formed by the tag antenna is shown in the figure, including the coil inductance (L), parasitic capacitance (Cp) and parallel capacitance (C2) of the tag antenna, and its resonant frequency is

Formula C is the parallel equivalent capacitance of Cp and C2, and R1 and R2 are the equivalent resistance of the inductance coil and other devices in the circuit. M is a variable resistor representing a temperature-sensitive device, S is a logic circuit for controlling on-off, R3 is an equivalent resistance connected in series with the temperature-sensitive device, and F is a voltage-resistance conversion device. When the logic circuit is disconnected, the temperature-sensitive device is not connected in parallel with the antenna, and it is placed at a certain temperature at this time, and the first resonant frequency and signal strength of the antenna remain unchanged. When the logic circuit is turned on, the temperature-sensitive device is connected in parallel with the antenna. At this time, it is placed at a certain temperature. At least one of the characteristic frequency and signal strength of the antenna will change. At this time, the antenna works at the second resonance frequency.

As shown in FIG. 4 , it is a schematic diagram of a temperature-sensitive device directly connected to an RFID tag antenna according to an embodiment of the present invention, that is, a schematic diagram of a passive RFID tag device 40 that can detect temperature changes. As shown in FIG. 4 , the tag device 40 includes a base 45 , an integrated circuit 43 and a double dipole antenna 41 , 42 . A temperature sensitive device 44 connected to the antenna 42 will affect the resistance of the antenna 42 . The material used for the temperature sensitive device 44 can control the frequency at any given point according to the current voltage of any one of the antennas 41,42. As an example, the antennas 41, 42 are mounted so that they resonate at the same frequency. As another example, antennas 41, 42 may be installed to resonate at different frequencies.

In one example, the transmitting antennas 41, 42 are made of one or more different low-resistance materials with high conductivity, such as copper, silver, and aluminum, which are similar to the above-mentioned temperature-sensitive The devices are connected, and when the antennas 41, 42 are placed at a certain temperature, the temperature-sensitive device will cause a change in the resonant frequency of one or more transmitters, resulting in a different frequency. The change in this frequency is not the same as the received and transmitted frequency. For example, placing the temperature sensitive device at a certain temperature will cause at least one of the transmitting frequency and the receiving frequency to change.

In another example, the antenna frequency value is initially set higher than the antenna frequency at a certain temperature environment, and then when a certain temperature is reached, it is lowered. In another example, the antenna frequency is initially set lower than the antenna frequency at a certain temperature, and it is increased when a certain temperature is reached. Such temperature-sensitive devices that can be used in the present invention include: thermocouple temperature-sensitive devices, semiconductor temperature-sensitive devices, PN crystal temperature-sensitive devices, transistor temperature-sensitive devices, thyristor temperature-sensitive devices, integrated temperature-sensitive devices, and the like.

Depending on the type of the temperature sensitive device, the resulting temperature change may be a specific temperature value or a selective range of temperature values. The length of time will inevitably lead to changes in the resonant frequency of the antenna, and the quality of the antenna will also cause different changes. For example, the type of temperature sensitive device on the antenna can affect how long it takes to change the resonant frequency of the antenna.

An example configuration of a thermocouple includes thermodes 511, 512, platinum-rhodium wire 513, pure platinum wire 514, protective sheath 515, and weld 516, as shown in Figure 5.1. The thermocouple has the advantages of fast action response, small heat capacity at the measuring end, good flexibility, high strength, and many types.

As shown in Figure 5.2, it is a PN junction temperature-sensitive device. When the measurement range is 0~150°C, using the voltage and temperature characteristics of the PN junction of the diode, a PN junction temperature-sensitive device can be made. Not only is the linearity better than that of a thermocouple, but the sensitivity can reach 2mV/°C. Since the hole and electron concentrations in semiconductors are greatly affected by temperature, temperature sensors made according to the temperature characteristics of semiconductors are widely used in medical devices. The accuracy of a thermometer made of a PN junction is mainly determined by the reading accuracy of the display instrument, and its sensitivity is also difficult to achieve with other types of sensors.

As shown in FIG. 6 , it is a flowchart of a method for detecting temperature changes by using a multi-antenna tag device according to the present invention. It should be taken into consideration that the aforementioned devices use a single tag IC to communicate with multiple antennas.

As shown in Figure 6, 50, the RFID reader sends energy and commands to the tag device. 52. The logic circuit is in the disconnected state at the initial time, and the tag device receives energy and instructions through the antenna not connected to the temperature-sensitive device. 54. The tag device converts the electromagnetic wave carrying energy into DC (direct current) voltage, so that the tag can execute the instruction. And this conversion needs to use a charge pump, a rectifier circuit, or connect them to each other, or use other energy conversion devices. 56. The tag device sends a signal to the reader through an antenna not connected to the temperature-sensitive device. 58. The reader measures and records the energy intensity of the received signal. 60. The reader sends an instruction to turn on the logic circuit to the tag device. 62. The tag device sends data through the antenna connected to the temperature-sensitive device. 64. The reader measures the energy strength of the received signal. 66. The reader calculates a comparison value reflecting the signal strength. 68. The reader converts the comparison value into different temperature values. As an example, the reader will set a time period to receive the signal of the tag, if no signal is received, the reader will record the signal strength as 0.

In this system, the reader uses the signal strength value from the antenna not connected to the temperature sensitive device as a reference value and compares it with the signal strength value from the tag antenna connected to the temperature sensitive device. By receiving signals from transmitters connected to the temperature-sensitive device and not connected to the temperature-sensitive device, the reader collects comparison values representing different signal intensities. The RFID reader then converts such a comparison value into the temperature at which the tag is located. For a specific example, the RFID reader is configured to convert the difference in strength of the received RF signal from an antenna connected or not connected to a temperature sensitive device into a temperature value by using stored reference data.

In the best case, use the antenna without the temperature-sensitive device as a reference to filter out variations due to coupling between the tag and the reader. Additionally, as mentioned earlier, a temperature-sensitive device is incorporated into the design so that its impedance changes in a one-to-one relationship with the amount of time the tag is held at a particular temperature. For example, positioning the temperature sensitive device on only one antenna allows the signal from the RFID tag device to vary over a certain range as a function of the time the antenna is placed at a certain temperature. Only function. As above, by using the present invention, under the condition that the RFID tag is passive, the RFID reader can detect whether the tag device has been placed at a certain temperature and whether the temperature is within an acceptable range.

Various RFID tags that do not use two antennas can also use temperature-sensitive devices to sense changes in temperature. The change in perceived temperature is based on changes in the resonant frequency of the antennas and can also identify changes in signals received by the antennas.

For example, through the design of the antenna connected to the temperature-sensitive device, the frequency of the antenna can be changed in the ISM (Industrial Scientific Medical, industrial, scientific, medical) frequency band, and the standard label can be connected to the temperature-sensitive device and logic. Antenna connected to the circuit.

For example, in a specific example, the tag antenna can be set as follows. Before being exposed to a certain temperature environment, the resonant frequency of the antenna is 902-928MHZ, but once the tag is exposed to a certain temperature environment, due to the influence of temperature, the resonance frequency of the antenna The frequency is reduced to 899.5-927.5MHZ. In the US RFID frequency band (902-928MHZ) is divided into 52 channels. In these 52 channels, the reader can randomly skip the channels that cannot be received. The benefit of this jump is that it can effectively prevent conflicts caused by multiple readers trying to use the same frequency in the same physical space.

For example, in one example, the RFID frequency band (902-928MHZ) is not divided into 52 channels but divided into n channel labels evenly. The antenna of the label is set to work in this frequency band (902-928MHZ). Since the tag antenna is connected to the temperature sensitive device, as long as the temperature exceeds the preset value range, the working frequency of the antenna tag antenna will drop to the frequency range (899.5-927.5MHZ). Therefore, compared with the original frequency band, channel n is excluded from the frequency range, so the changed frequency band (899.5-927.5MHZ) no longer allows the tag to communicate with channel n.

In a specific example, if the environment where the tag is located exceeds the expected temperature range, the reader can only send instructions to the tag through channels 1 to n-1, and the tag can also respond, because the antenna in the tag can only be in the Working in this frequency range, when the reader sends instructions to the tag at the frequency of channel n, the tag antenna’s resonance frequency has dropped to 899.5-927.5MHZ due to the change of the tag’s temperature, and it will no longer reach 928MHZ, so the tag will no longer do it. Responds and transmits the information back to the reader.

An advantageous aspect is that changes in the operating frequency of the antenna due to temperature exceeding a preset value are reflected by the loss of this communication.

In the model, the reader can send a command between channel n-1 and channel n to the tag to further confirm that the working frequency range of the tag antenna has drifted, because the tag can receive the signal sent through channel n-1 command, and can feed back information to the reader through channel n-1, because the tag cannot receive commands sent through channel n, and cannot feed back information to the reader through channel n, thus determining the tag antenna The operating frequency range has drifted.

The temperature change causes the working frequency of the tag antenna to drift up and down and the present invention is not limited to dividing the frequency band into n channels equally.

The embodiments of the present invention can detect temperature changes at a relatively low cost, and use energy obtained by RFID to solve the problem of power supply for temperature detection.

The implementation of each feature of this system may involve software, and the hardware may also involve a combination of software and hardware. For example, the implementation of many advantages of the system is achieved through programming with a high-level processing and object-oriented programming language and computer It is realized by means of mutual communication with other equipment and machines. Each of these functional programs may be stored in a storage medium such as a read-only memory and read by a computer and processor to implement the above-mentioned functions.

Those skilled in the art can also understand that various illustrative logical blocks, units, and steps listed in the embodiments of the present invention can be implemented by electronic hardware, computer software, or a combination of both. To clearly demonstrate the interchangeability of hardware and software, the various illustrative components, units and steps above have generically described their functions. Whether such functions are implemented by hardware or software depends on the specific application and overall system design requirements. Those skilled in the art may use various methods to implement the described functions for each specific application, but such implementation should not be understood as exceeding the protection scope of the embodiments of the present invention.

The various illustrative logic blocks or units described in the embodiments of the present invention can be implemented by general-purpose processors, digital signal processors, application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs) or other programmable logic devices, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to implement or operate the described functions. The general-purpose processor may be a microprocessor, and optionally, the general-purpose processor may also be any conventional processor, controller, microcontroller or state machine. A processor may also be implemented by a combination of computing devices, such as a digital signal processor and a microprocessor, multiple microprocessors, one or more microprocessors combined with a digital signal processor core, or any other similar configuration to accomplish.

The steps of the method or algorithm described in the embodiments of the present invention may be directly embedded in hardware, a software module executed by a processor, or a combination of both. The software modules may be stored in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, removable disk, CD-ROM or any other storage medium in the art. Exemplarily, the storage medium can be connected to the processor, so that the processor can read information from the storage medium, and can write information to the storage medium. Optionally, the storage medium can also be integrated into the processor. The processor and the storage medium can be set in the ASIC, and the ASIC can be set in the user terminal. Optionally, the processor and the storage medium may also be set in different components in the user terminal.

In one or more exemplary designs, the above functions described in the embodiments of the present invention may be implemented in hardware, software, firmware or any combination of the three. If implemented in software, the functions can be stored on or transmitted over as one or more instructions or code on a computer-readable medium. Computer-readable media includes computer storage media and communication media that facilitate transfer of a computer program from one place to another. Storage media may be any available media that can be accessed by a general purpose or special computer. For example, such computer-readable media may include, but are not limited to, RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other device that can be used to carry or store instructions or data structures and Other medium of program code in a form readable by a general-purpose or special-purpose computer, or a general-purpose or special-purpose processor. In addition, any connection is properly defined as a computer-readable medium, for example, if the software is transmitted from a web site, server, or other remote source via a coaxial cable, fiber optic computer, twisted pair, digital subscriber line (DSL) Or transmitted by wireless means such as infrared, wireless and microwave are also included in the definition of computer readable media. Disks and discs include compact discs, laser discs, optical discs, DVDs, floppy discs, and Blu-ray discs. Disks usually reproduce data magnetically, while discs usually reproduce data optically with lasers. Combinations of the above can also be contained on a computer readable medium.

The specific embodiments described above have further described the purpose, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above descriptions are only specific embodiments of the present invention and are not intended to limit the scope of the present invention. Protection scope, within the spirit and principles of the present invention, any modification, equivalent replacement, improvement, etc., shall be included in the protection scope of the present invention.

Claims (14)

1. a kind of RFID tag with temperature-sensitive device, it is characterized in that, two pins are arranged on the chip of described RFID tag; Described temperature-sensitive device links to each other with these two pins, and with the antenna of described RFID tag A parallel structure is formed, and changes in the external temperature will cause changes in the voltage or current at both ends of the temperature-sensitive device. There is a logic circuit for controlling on-off and a voltage-resistance conversion on the line connecting the temperature-sensitive device to the chip of the RFID tag. device, the connected circuit, the logic circuit and the voltage-resistance conversion device are part of the chip, the voltage-resistance conversion device is used to convert the change of voltage or current across the temperature-sensitive device into a change of resistance, the logic circuit through The disconnection determines whether the temperature-sensitive device is connected in parallel with the antenna: when the logic circuit is disconnected, the temperature-sensitive device is not connected in parallel with the antenna. At this time, it is placed at a certain temperature, and the first resonant frequency and signal strength of the antenna remain unchanged; when When the logic circuit is turned on, the temperature-sensitive device is connected in parallel with the antenna, and at this time it is placed at a certain temperature, at least one of the characteristic frequency and signal strength of the antenna will change, and the antenna works at the second resonance frequency at this time; The RFID tag receives the instructions sent by the RFID reader to control the on-off of the logic circuit, so as to detect the change of temperature by comparing the difference between the signal strengths of different frequencies from the antenna. 2. The RFID tag with a temperature sensitive device according to claim 1, wherein the antenna of the RFID tag is a monopole antenna. 3. the RFID tag with temperature-sensitive device as claimed in claim 1, is characterized in that, the antenna of described RFID tag is a double dipole antenna: described temperature-sensitive device and the voltage-resistance conversion device that links to each other with this temperature-sensitive device A parallel structure is formed with one of the antennas; or the temperature-sensitive device and the voltage-resistance conversion device connected to the temperature-sensitive device form a parallel structure with two antennas at the same time. 4. The RFID tag with temperature sensitive device as claimed in claim 1, is characterized in that, described voltage-resistance conversion device comprises: a variable voltage is converted into the device of variable resistance, or a groove type field effect transistor, or An equivalent circuit of a field effect transistor, the temperature sensitive device includes: a thermocouple temperature sensitive device, a semiconductor temperature sensitive device, a PN crystal temperature sensitive device, a transistor temperature sensitive device, a thyristor temperature sensitive device, and an integrated temperature sensitive device. 5. A kind of RFID tag with temperature-sensitive device, it is characterized in that, a pin is arranged on the chip of described RFID tag; One end of described temperature-sensitive device is connected with this pin, and the other end is connected with the pin of described RFID tag On the antenna, and form a parallel structure with the antenna, the change of the external temperature will cause the change of the voltage or current at both ends of the temperature-sensitive device, and there is a logic circuit for controlling on-off on the line connecting the temperature-sensitive device and the chip of the RFID tag and a voltage-resistance conversion device, the connected circuit, the logic circuit and the voltage-resistance conversion device are part of the chip, and the voltage-resistance conversion device is used to convert the change of voltage or current across the temperature-sensitive device into resistance The on-off of the logic circuit determines whether the temperature-sensitive device is connected in parallel with the antenna: when the logic circuit is disconnected, the temperature-sensitive device is not connected in parallel with the antenna. At this time, it is placed at a certain temperature, and the first resonant frequency of the antenna and the signal The strength remains unchanged; when the logic circuit is connected, the temperature-sensitive device is connected in parallel with the antenna, and at this time it is placed at a certain temperature, at least one of the characteristic frequency and signal strength of the antenna will change, and the antenna works at the second At the resonant frequency: the RFID tag receives instructions sent by the RFID reader to control the on-off of the logic circuit, so as to detect the change of temperature by comparing the difference between the signal strengths of different frequencies from the antenna. 6. The RFID tag with a temperature sensitive device according to claim 5, wherein the antenna of the RFID tag is a monopole antenna. 7. the RFID tag with temperature-sensitive device as claimed in claim 5, is characterized in that, the antenna of described RFID tag is a double dipole antenna: described temperature-sensitive device and the voltage-resistance conversion device that links to each other with this temperature-sensitive device A parallel structure is formed with one of the antennas; or the temperature-sensitive device and the voltage-resistance conversion device connected to the temperature-sensitive device form a parallel structure with two antennas at the same time. 8. The RFID tag with a temperature sensitive device as claimed in claim 5, wherein the voltage-resistance conversion device comprises: a device for converting a variable voltage into a variable resistance, or a trench field effect transistor, or An equivalent circuit of a field effect transistor, the temperature sensitive device includes: a thermocouple temperature sensitive device, a semiconductor temperature sensitive device, a PN crystal temperature sensitive device, a transistor temperature sensitive device, a thyristor temperature sensitive device, and an integrated temperature sensitive device. 9. An RFID tag with a temperature-sensitive device, characterized in that, the temperature-sensitive device is connected to the antenna of the RFID tag, and forms a parallel structure with the antenna, and changes in the external temperature will cause voltage across the temperature-sensitive device. or current changes, there is a logic circuit for controlling on-off and a voltage-resistance conversion device on the circuit connecting the temperature-sensitive device and the antenna, and the connected circuit, the logic circuit and the voltage-resistance conversion device are chips Part of the voltage-resistance conversion device is used to convert the change of voltage or current across the temperature-sensitive device into a change of resistance. The on-off of the logic circuit determines whether the temperature-sensitive device is connected in parallel with the antenna: when the logic circuit is disconnected, the temperature The sensitive device is not connected in parallel with the antenna. At this time, it is placed at a certain temperature, and the first resonance frequency and signal strength of the antenna remain unchanged; when the logic circuit is connected, the temperature sensitive device is connected in parallel with the antenna. At this time, it is placed at a certain temperature. At least one of the characteristic frequency and signal strength of the antenna will change at a certain temperature. At this time, the antenna works at the second resonance frequency; the RFID tag receives instructions sent by the RFID reader to control the on-off of the logic circuit, thereby realizing Changes in temperature are detected by comparing the difference between the signal strengths of different frequencies from the antenna. 10. The RFID tag with a temperature sensitive device according to claim 9, wherein the antenna of the RFID tag is a monopole antenna. 11. the RFID tag with temperature-sensitive device as claimed in claim 9, is characterized in that, the antenna of described RFID tag is a double dipole antenna: described temperature-sensitive device and the voltage-resistance conversion device that links to each other with this temperature-sensitive device A parallel structure is formed with one of the antennas; or the temperature-sensitive device and the voltage-resistance conversion device connected to the temperature-sensitive device form a parallel structure with two antennas at the same time. 12. The RFID tag with a temperature sensitive device as claimed in claim 9, wherein the voltage-resistance conversion device comprises: a device for converting a variable voltage into a variable resistance, or a trench field effect transistor, or An equivalent circuit of a field effect transistor, the temperature sensitive device includes: a thermocouple temperature sensitive device, a semiconductor temperature sensitive device, a PN crystal temperature sensitive device, a transistor temperature sensitive device, a thyristor temperature sensitive device, and an integrated temperature sensitive device. 13. A kind of RFID system with temperature-sensitive device, described RFID system comprises RFID label and RFID reader, it is characterized in that, The RFID tag comprises the RFID tag with the temperature-sensitive device described in any one of claims 1-4, or the RFID tag with the temperature-sensitive device described in any one of claims 5-8, or the RFID tag with the temperature-sensitive device described in any one of claims 9-12 The RFID tag with temperature-sensitive device described in any one; The RFID reader sends instructions to control the on-off of the logic circuit of the RFID tag, thereby detecting the change of temperature by comparing the difference between the signal strengths of different frequencies from the antenna. 14. A temperature detection method of an RFID system with a temperature-sensitive device, wherein the temperature detection method is applied to the RFID system with a temperature-sensitive device according to claim 13, comprising: Sending instructions through the RFID reader to control the on-off of the logic circuit of the RFID tag; Receive the instructions sent by the RFID reader through the RFID tag to control the on-off of the logic circuit: when the logic circuit is disconnected, the temperature-sensitive device is not connected in parallel with the antenna. At this time, it is placed at a certain temperature, and the first resonant frequency of the antenna and The signal strength remains unchanged; when the logic circuit is connected, the temperature-sensitive device is connected in parallel with the antenna, and at this time it is placed at a certain temperature, at least one of the characteristic frequency and signal strength of the antenna will change, and the antenna works at this time. At the second resonance frequency; A change in temperature is detected using the RFID reader to compare the difference between the signal strengths of different frequencies from the antenna.

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