CN102750571B - RFID label tag, rfid system and the stress detection method of a kind of band force sensitive device - Google Patents

Abstract

The invention provides an RFID tag with a force sensitive device, an RFID system and a force detection method. The force sensitive device and the antenna of the RFID tag form a parallel structure, and there are A logic circuit that controls on-off, the connected line and the logic circuit that controls on-off are part of the chip: when the logic circuit is disconnected, the force-sensitive device is not connected in parallel with the antenna, and if the sensitive device is under pressure, the first part of the antenna The resonance frequency and signal strength remain unchanged; when the logic circuit is connected, the force-sensitive device is connected in parallel with the antenna, and if the sensitive device is under pressure, 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 the pressure by comparing the difference between the signal strengths of different frequencies from the antenna. The present invention can detect the change of the received pressure at a lower cost.

Description

An RFID tag with a force-sensitive device, an RFID system, and a force 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 force sensitive device, an RFID system and a force 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 speaking, 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 installations, RFID systems with force-sensitive devices have been used to monitor when the force in the product's environment exceeds acceptable levels. Typically these devices require a continuous power source for the sensing device to detect changes in applied pressure, 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 changes in applied pressure 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 force-sensitive device, an RFID system, and a force detection method to detect changes in pressure at a lower cost.

On the one hand, the embodiment of the present invention provides an RFID tag with a force-sensitive device. There are two pins on the chip of the RFID tag; the force-sensitive device is connected to these two pins and connected to the The antenna of the RFID tag forms a parallel structure, and changes in the external force will cause changes in the resistance of the force-sensitive device itself. There is a logic circuit for controlling on-off on the line connecting the force-sensitive device and the chip of the RFID tag. The connected line and the logic circuit for controlling on-off are part of the chip. The on-off of the logic circuit determines whether the force-sensitive device is connected in parallel with the antenna: when the logic circuit is disconnected, the force-sensitive device is not connected in parallel with the antenna. When the device is under pressure, the first resonant frequency and signal strength of the antenna remain unchanged; when the logic circuit is connected, the force-sensitive device is connected in parallel with the antenna, and if the sensitive device is under pressure, at least one of the characteristic frequency and signal strength of the antenna will occur At this time, the antenna works at the second resonant frequency; the RFID tag receives instructions sent by the RFID reader to control the on-off of the logic circuit, thereby realizing the detection by comparing the difference between the signal strengths of different frequencies from the antenna Changes in stress.

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 force sensitive device forms a parallel structure with one of the antennas; or the force sensitive device forms a parallel structure with two antennas At the same time, a parallel structure is formed.

Optionally, in an embodiment of the present invention, the force-sensitive device is a resistive force-sensitive device, and the force-sensitive device includes: a strain-type force-sensitive device, a capacitive force-sensitive device, a capacitive Load sensitive device, differential capacitive pressure sensitive device, differential capacitive acceleration sensitive device, ADXL50 capacitive integrated acceleration sensitive device, pressure sensitive conductive rubber sensitive device.

On the other hand, the embodiment of the present invention provides an RFID tag with a force-sensitive device. There is a pin on the chip of the RFID tag; one end of the force-sensitive device is connected to the pin, and the other end is connected to the pin. On the antenna of the RFID tag, and form a parallel structure with the antenna, the change of the external force will cause the change of the resistance of the force sensitive device itself, and there is a circuit connecting the force sensitive device and the chip of the RFID tag The logic circuit that controls on-off, the connected line and the logic circuit that controls on-off are part of the chip. The on-off of the logic circuit determines whether the force-sensitive device is connected in parallel with the antenna: when the logic circuit is disconnected, the force-sensitive device Not connected in parallel with the antenna, if the sensitive device is under pressure, the first resonant frequency and signal strength of the antenna remain unchanged; when the logic circuit is connected, the force sensitive device is connected in parallel with the antenna, if the sensitive device is under pressure, the characteristic frequency and At least one of the signal strengths will change, and at this time the antenna works at the second resonant frequency; the RFID tag receives instructions sent by the RFID reader to control the on-off of the logic circuit, thereby achieving The difference between the intensities is used to detect changes in the applied pressure.

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 force sensitive device forms a parallel structure with one of the antennas; or the force sensitive device forms a parallel structure with two antennas At the same time, a parallel structure is formed.

Optionally, in an embodiment of the present invention, the force sensitive device is a resistive force sensitive device, and the resistive force sensitive device includes: a strain type force sensitive device, a capacitive force sensitive device, Capacitive load sensor, differential capacitive pressure sensor, differential capacitive acceleration sensor, ADXL50 capacitive integrated acceleration sensor, pressure-sensitive conductive rubber sensor.

In yet another aspect, an embodiment of the present invention provides an RFID tag with a force-sensitive device. The force-sensitive device is connected to the antenna of the RFID tag and forms a parallel structure with the antenna. Changes in external force will The change of the resistance of the force-sensitive device itself is caused. There is a logic circuit for controlling on-off on the line connecting the force-sensitive device and the antenna. The connected line and the logic circuit for controlling on-off are part of the chip. The logic circuit The on-off of the force-sensitive device determines whether the force-sensitive device is connected in parallel with the antenna: when the logic circuit is disconnected, the force-sensitive device is not connected in parallel with the antenna, and if the sensitive device is under pressure, the first resonant frequency and signal strength of the antenna remain unchanged; when When the logic circuit is connected, the force-sensitive device is connected in parallel with the antenna. If the sensitive device is under pressure, 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 RFID tag receives The instructions sent by the RFID reader are used to control the on-off of the logic circuit, so as to detect the change of the pressure 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 force sensitive device forms a parallel structure with one of the antennas; or the force sensitive device forms a parallel structure with two antennas At the same time, a parallel structure is formed.

Optionally, in an embodiment of the present invention, the force sensitive device is a resistive force sensitive device, and the resistive force sensitive device includes: a strain type force sensitive device, a capacitive force sensitive device, Capacitive load sensor, differential capacitive pressure sensor, differential capacitive acceleration sensor, ADXL50 capacitive integrated acceleration sensor, pressure-sensitive conductive rubber sensor.

In another aspect, an embodiment of the present invention provides an RFID system with a force-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 force-sensitive device; The RFID reader sends commands to control the on-off of the logic circuit of the RFID tag, thereby detecting the change of the pressure 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 force detection method for an RFID system with a force-sensitive device. The force detection method is applied to the above-mentioned RFID system with a force-sensitive device, including: using the RFID The reader sends instructions to control the on-off of the logic circuit of the RFID tag; the instruction sent by the RFID reader is received through the RFID tag to control the on-off of the logic circuit: when the logic circuit is disconnected, the force-sensitive device is not connected in parallel with the antenna, this When placed under a certain force intensity, the first resonant frequency and signal strength of the antenna remain unchanged; when the logic circuit is connected, the force sensitive device is connected in parallel with the antenna, and is placed under a certain force Intensity, at least one of the characteristic frequency and signal strength of the antenna will change, and now the antenna works at the second resonance frequency; use the RFID reader to compare the difference between the signal strengths of different frequencies from the antenna to detect the Change under pressure.

The above technical solution has the following beneficial effects: because the force-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 on the circuit connecting the force-sensitive device and the chip of the RFID tag, and the connected circuit The logic circuit that controls on-off is a part of the chip: when the logic circuit is disconnected, the force-sensitive device is not connected in parallel with the antenna, and if the sensitive device is under pressure, the first resonant frequency and signal strength of the antenna remain unchanged; when the logic circuit When turned on, the force-sensitive device is connected in parallel with the antenna. If the sensitive device is under pressure, 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, thereby realizing The difference between the signal strength of different frequencies from the antenna is used to detect the change of the pressure, so the technical effect of detecting the change of the pressure is achieved at a lower cost, and the energy obtained by RFID is used to solve the problem. The power supply problem of force detection.

Description of drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in 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 force 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 a schematic diagram of the connection between the force-sensitive device and the logical switch and the equivalent circuit of the internal antenna of the RFID tag chip according to the embodiment of the present invention;

4 is a schematic diagram of the direct connection between the force-sensitive device and the RFID tag antenna according to the embodiment of the present invention;

Fig. 5 is a structural explanatory diagram of a force-sensitive device according to an embodiment of the present invention;

FIG. 6 is a flow chart of a method for detecting stress based on signal strength according to an embodiment of the present invention.

detailed description

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 force-sensitive device in the embodiment of the present invention is connected to the chip of the RFID tag:

Two-pin structure:

Embodiments of the present invention are a device, system and technique for detecting changes in applied pressure. The system consists of an RFID tag with two pins on a chip. The force-sensitive device is connected with these two pins and forms a parallel structure with the antenna. Changes in external force will cause changes in the resistance of the force-sensitive device itself. There is a logic circuit for controlling on-off on the line connecting the pin and the chip, and the connected line and the logic circuit for controlling on-off are part of the chip. The on-off of the logic circuit determines whether the force-sensitive device is connected in parallel with the antenna.

When the logic circuit is disconnected, the force sensitive device is not connected in parallel with the antenna, and if the sensitive device is under pressure, the first resonant frequency and signal strength of the antenna remain unchanged. When the logic circuit is connected, the force-sensitive device is connected in parallel with the antenna. If the sensitive device is under pressure, 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 RFID reader can send instructions to the tag to control the on-off of the logic circuit. When the logic circuit is turned on, it can detect the change of the pressure by comparing the difference between the signal strengths of different frequencies from the antenna.

As an example, the system includes an RFID tag with only one antenna. There are two pins on the chip of this tag. The force-sensitive device is connected to these two pins and forms a parallel structure with this antenna. There is a logic circuit for controlling on-off on the line connecting the pin and the chip, and the connected line and the logic circuit for controlling on-off are part of the chip. Changes in external force will cause changes in the resistance of the force-sensitive device itself.

When the logic circuit is turned on and placed under a certain force for a period of time, 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 reader can send instructions to the tag, and can detect the change of the pressure by comparing the difference between the signal strength of different frequencies when the logic circuit is turned on and off. More precisely, the force-sensitive device should have a lower resistance, and its specific examples include: strain-type force-sensitive device, capacitive force-sensitive device, capacitive load-sensitive device, differential capacitive pressure-sensitive device, Differential capacitive acceleration sensor, ADXL50 capacitive integrated acceleration sensor, pressure-sensitive conductive rubber sensor, etc.

As another example, the system includes an RFID tag with two antennas on it. There are two situations at this point. In the first case, the force-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 on the line connecting the pin and the chip, and the connected line and the logic circuit for controlling on-off are part of the chip. Changes in external force will cause changes in the resistance of the force-sensitive device itself. However, the second antenna always communicates normally at the first resonant frequency.

When the logic circuit is turned on, at least one of the characteristic frequency and signal strength of the first antenna will change after being placed under a certain force for a period of time, and it works at the second resonance frequency. The RFID reader can send commands to the tag and detect the change in pressure by comparing the difference between the signal strength of the first and second antenna at different frequencies when the logic circuit is turned on. Changes in stress can also be detected by comparing the difference in signal strength at different frequencies when the second antenna's own logic circuit is switched on and off.

In the second case, the force-sensitive device is connected to the two pins, and forms a parallel structure with the two antennas at the same time. There is a logic circuit for controlling on-off on the line connecting the pin and the chip, and the connected line and the logic circuit for controlling on-off are part of the chip. Changes in external force will cause changes in the resistance of the force-sensitive device itself. This is similar to the case where the tag has only one antenna.

When the logic circuit is turned on and placed under a certain force for a period of time, 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 reader can send instructions to the tag, and can detect the change of the pressure 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 force-sensitive device should have a lower resistance, and its specific examples include: strain-type force-sensitive device, capacitive force-sensitive device, capacitive load-sensitive device, differential capacitive pressure-sensitive device, Differential capacitive acceleration sensor, ADXL50 capacitive integrated acceleration sensor, pressure-sensitive conductive rubber sensor, etc.

One pin structure:

The chip of the tag may have only one pin, and this pin is outwardly connected to one end of the force-sensitive device, and the other end of the force-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.

When the logic circuit is disconnected, the force sensitive device is not connected in parallel with the antenna, and if the sensitive device is under pressure, the first resonant frequency and signal strength of the antenna remain unchanged. When the logic circuit is connected, the force-sensitive device is connected in parallel with the antenna. If the sensitive device is under pressure, 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 reader can send instructions to the tag to control the on-off of the logic circuit. When the logic circuit is turned on, it can detect the change of the pressure by comparing the difference between the signal strengths of different frequencies from the antenna.

As an example, the system includes an RFID tag with only one antenna. This tag has a pin on the chip. The force-sensitive device is connected to this pin, and the other end of the force-sensitive device is directly connected to the antenna, forming a parallel structure with the antenna. There is a logic circuit for controlling on-off on the line connecting the pin and the chip, and the connected line and the logic circuit for controlling on-off are part of the chip. Changes in external force will cause changes in the resistance of the force-sensitive device itself.

When the logic circuit is turned on and placed under a certain force for a period of time, the antenna works at the second resonance frequency, and at least one of its characteristic frequency and signal strength will change. The RFID reader can send instructions to the tag, and can detect the change of the pressure by comparing the difference between the signal strength of different frequencies when the logic circuit is turned on and off. More precisely, the force-sensitive device should have a lower resistance, and its specific examples include: strain-type force-sensitive device, capacitive force-sensitive device, capacitive load-sensitive device, differential capacitive pressure-sensitive device, Differential capacitive acceleration sensor, ADXL50 capacitive integrated acceleration sensor, pressure-sensitive conductive rubber sensor, etc.

As another example, the system includes an RFID tag with two antennas on it. This tag has a pin on the chip. The force sensitive device is connected to this pin, and the other end of the force 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 on the line connecting the pin and the chip, and the connected line and the logic circuit for controlling on-off are part of the chip. Changes in external force will cause changes in the resistance of the force-sensitive device itself. The second antenna, however, always communicates at the first resonant frequency.

When the logic circuit is turned on, after being placed under a certain force for a period of time, the first antenna works at the second resonance frequency, and at least one of its characteristic frequency and signal strength will change. The RFID reader can send commands to the tag and detect the change in pressure by comparing the difference between the signal strength of the first and second antenna at different frequencies when the logic circuit is turned on. Changes in stress can also be detected by comparing the difference in signal strength at different frequencies when the logic circuit of the first antenna itself is on and off. More precisely, the force-sensitive device should have a lower resistance, and its specific examples include: strain-type force-sensitive device, capacitive force-sensitive device, capacitive load-sensitive device, differential capacitive pressure-sensitive device, Differential capacitive acceleration sensor, ADXL50 capacitive integrated acceleration sensor, pressure-sensitive conductive rubber sensor, etc.

No lead structure:

When there are no pins on the chip of the RFID tag, the force-sensitive device can be directly connected to the antenna. In this case, the antenna connected to the force-sensitive device cannot communicate with the normal frequency without detaching from the force-sensitive device. When placed under a certain force for a period of time, at least one of the characteristic frequency and signal strength of the antenna will change. The RFID reader can send instructions to the tag device to detect the change in the pressure by comparing the difference between the signal strength of different frequencies from the antenna.

As an example, the system includes an RFID tag with two antennas. The force-sensitive device is directly connected to the first antenna, while the second antenna is not connected to the force-sensitive device and always communicates normally at the first resonance frequency. When placed under a certain force for a period of time, the first antenna works at the second resonance frequency, at least one of its characteristic frequency and signal strength will change, while the characteristic frequency and signal strength of the second antenna constant. The RFID reader can send commands to the tag and can detect the change in pressure by comparing the difference between the signal strength of the first and second antennas at different frequencies. More precisely, the force-sensitive device should have a lower resistance, and its specific examples include: strain-type force-sensitive device, capacitive force-sensitive device, capacitive load-sensitive device, differential capacitive pressure-sensitive device, Differential capacitive acceleration sensor, ADXL50 capacitive integrated acceleration sensor, pressure-sensitive conductive rubber sensor, etc.

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 force-sensitive devices can also be connected, and the models of the force-sensitive devices can be the same or different. As for a specific example of the device, at least one of the characteristic frequency and signal strength of the antenna connected to the force-sensitive device will change when it is placed under a certain force for a period of time. The RFID reader can send instructions to the tag device to detect the change in the pressure by comparing the difference between the signal strength of different frequencies from the antenna.

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

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 force.

In one example, the antenna of the RFID tag is connected to the force-sensitive device, and there is a logic circuit for controlling on-off on this connecting line. In the two cases of whether the logic circuit is on or off, there will be two different frequencies corresponding to the antenna. When the logic circuit is switched on and the tag device is placed under a certain force for a period of time, two signal strength values are produced due to the change in the resonant frequency.

In one example, the RFID tag device includes first and second antennas. In a better situation, the first antenna is connected to the force-sensitive device. When the tag device is placed under a certain force for a period of time, due to the change of the resonance frequency, the second signal strength value and The difference of the first signal strength value.

In another aspect, an embodiment of the present invention provides an RFID system with a force-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 force-sensitive device; The RFID reader sends commands to control the on-off of the logic circuit of the RFID tag, thereby detecting the change of the pressure 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 force detection method for an RFID system with a force-sensitive device. The force detection method is applied to the above-mentioned RFID system with a force-sensitive device, including: using the RFID The reader sends instructions to control the on-off of the logic circuit of the RFID tag; the instruction sent by the RFID reader is received through the RFID tag to control the on-off of the logic circuit: when the logic circuit is disconnected, the force-sensitive device is not connected in parallel with the antenna, this When placed under a certain force intensity, the first resonant frequency and signal strength of the antenna remain unchanged; when the logic circuit is connected, the force sensitive device is connected in parallel with the antenna, and is placed under a certain force Intensity, at least one of the characteristic frequency and signal strength of the antenna will change, and now the antenna works at the second resonance frequency; use the RFID reader to compare the difference between the signal strengths of different frequencies from the antenna to detect the Change under pressure.

As shown in FIG. 1 , it is a schematic diagram of a force-sensitive tag 10 in which a force-sensitive device and an RFID tag chip are connected according to an embodiment of the present invention. 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 . Two pins 16 and 17 are arranged on the integrated circuit board 13, and these two pins are outwardly connected with the force-sensitive device 14, 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. Whether the force-sensitive module 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 and placed under a certain force for a period of time, the antenna works at the second resonance frequency, and at least one of its characteristic frequency and signal strength will change.

In one example, the emitters 11, 12 are made of one or more different low-resistance materials with high electrical conductivity, such as copper, silver, and aluminum, which are sensitive to the force mentioned above. The device is connected to the antennas 11 and 12 through two pins 16 and 17. When the antennas 11 and 12 are placed under a certain force for a period of time, the force-sensitive device will cause one or more transmitters to have resonance frequencies Variety. The frequency of this change is not the same as the frequency of reception and transmission. For example, after the force-sensitive device is placed under a certain force for a period of time, at least one of the sending frequency and the receiving frequency will change.

In another example, the antenna frequency value will initially be set higher than the antenna frequency at a certain force environment, and then when a certain force is reached, it will be lowered. In another example, the antenna frequency is initially set lower than the antenna frequency at a certain stress, and it is raised when a certain stress is reached. Such force-sensitive devices that can be used in the present invention include: strain-type force-sensitive devices, capacitive force-sensitive devices, capacitive load-sensitive devices, differential capacitive pressure-sensitive devices, differential capacitive acceleration-sensitive devices, ADXL50 capacitive integrated acceleration sensor, pressure-sensitive conductive rubber sensor, etc.

Depending on the type of the force-sensitive device, the force that causes the change may be a specific force value or a selective force value range. 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 force 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 (C _p ) and parallel capacitance (C ₂ ) of the tag antenna, and its resonant frequency is In the formula, C is the parallel equivalent capacitance of C _p and C ₂ , R ₁ and R ₂ 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.

As shown in FIG. 3 , it is a schematic diagram of the connection between the force-sensitive device, the logic circuit for controlling on-off and the equivalent circuit of the RFID tag antenna according to the embodiment of the present invention. The resonant circuit formed by the tag antenna is shown in the figure, including the coil inductance (L), parasitic capacitance (C _p ) and parallel capacitance (C ₂ ) of the tag antenna, and its resonant frequency is Formula C is the parallel equivalent capacitance of C _p and C ₂ , R ₁ and R ₂ are the equivalent resistance of the inductance coil and other devices in the circuit. M is a variable resistor representing a force-sensitive device, and S is a logic circuit for controlling on-off. When the logic circuit is disconnected, the force sensitive device is not connected in parallel with the antenna, and if the sensitive device is under pressure, the first resonant frequency and signal strength of the antenna remain unchanged. When the logic circuit is connected, the force-sensitive device is connected in parallel with the antenna. If the sensitive device is under pressure, the antenna works at the second resonance frequency, and at least one of its characteristic frequency and signal strength will change.

As shown in FIG. 4 , it is a schematic diagram of a passive RFID tag device 40 that can detect changes in pressure according to an embodiment of the present invention. As shown in FIG. 4 , the tag device 40 includes a base 45 , an integrated circuit 43 and a double dipole antenna 41 , 42 . The force sensitive device 44 connected to the antenna 42 will affect the resistance of the antenna 42 . The material used for the force sensitive device 44 can control the frequency of 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 double dipole antennas 41, 42 are made of one or more different low-resistance materials with higher conductivity, such as copper, silver, and aluminum, which are similar to those mentioned above. When the antennas 41, 42 are placed under a certain force for a period of time, the force-sensitive device will cause a change in the resonant frequency of one or more transmitting ends, resulting in a different frequency. The change in this frequency is not the same as the received and transmitted frequency. For example, after the force-sensitive device is placed under a certain force for a period of time, at least one of the sending frequency and the receiving frequency will change.

In another example, the antenna frequency value will initially be set higher than the antenna frequency at a certain force environment, and then when a certain force is reached, it will be lowered. In another example, the antenna frequency is initially set lower than the antenna frequency at a certain stress, and it is raised when a certain stress is reached. Such force-sensitive devices that can be used in the present invention include: strain-type force-sensitive devices, capacitive force-sensitive devices, capacitive load-sensitive devices, differential capacitive pressure-sensitive devices, differential capacitive acceleration-sensitive devices , ADXL50 capacitive integrated acceleration sensitive device, pressure-sensitive conductive rubber sensitive device, etc.

Depending on the type of the force-sensitive device, the force that causes the change may be a specific force value or a selective force value range. 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 force sensitive device on the antenna can affect how long it takes to change the resonant frequency of the antenna.

As shown in FIG. 5 , an example of the force-sensitive device includes electrodes 51 and 52 , a pressure-sensitive conductive rubber 53 , an insulating film 54 and a force F. Pressure-sensitive conductive rubber is a pressure-sensitive elastic material. Its characteristic is that the resistance value of the rubber material changes with the pressure, so it is also a pressure-sensitive element with a switch function. When the pressure F is applied, the pressure-sensitive conductive rubber 53 forms a path between the two electrodes 51, 52, and when the applied force F disappears, the gap between the two electrodes 51, 52 is prevented from increasing.

As shown in FIG. 6 , it is a flowchart of a method for detecting force changes by using a multi-antenna tag device according to an embodiment of 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 force-sensitive device. 54. The tag device converts the electromagnetic wave carrying energy into a 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 the antenna not connected to the force-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 force-sensitive device. 64. The reader measures the energy strength of the received signal. 66. The reader calculates a comparison value of the response signal strength. 68. The reader converts the comparison value into different force 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 force sensitive device as a reference value and compares it with the signal strength value from the tag antenna connected to the force sensitive device. By receiving signals from transmitters connected to the force-sensitive device and not connected to the force-sensitive device, the reader collects comparison values representing different signal intensities. The RFID reader then converts such a comparison value into the force situation in which the tag is placed. For a specific example, the RFID reader is configured to convert the difference in received RF signal strength from an antenna connected or not connected to a force sensitive device to a force value by using stored reference data.

In the best case, use the antenna without the force sensitive device as a reference to filter out variations due to coupling between the tag and the reader. Additionally, as mentioned previously, a force-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 placed under a particular force. For example, positioning the force sensitive device on only one antenna allows the signal from the RFID tag device to vary over a range as a function of the force the antenna is placed under A function that is only available after time. As above, by using the present invention, under the passive condition of the RFID tag, the RFID reader can detect whether the tag device has been placed under a certain force and whether the force is within an acceptable range.

Various RFID tags that do not use two antennas can also use force-sensitive devices to sense changes in force. The change in perceived force 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 force-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 this force-sensitive device and An antenna connected to a logic circuit.

For example, in a specific example, the tag antenna can be set like this. Before being exposed to a certain force environment, the resonant frequency of the antenna is 902-928MHZ, but once the tag is exposed to a certain force environment, due to the influence of force, The resonant frequency of the antenna 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 advantage of this kind of hopping of the reader 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 force-sensitive device, as long as the force exceeds the preset value range, the working frequency of the antenna tag antenna will drop to the frequency range of (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 force 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 Working in this frequency range, when the reader sends instructions to the tag at the frequency of channel n, the resonant frequency of the tag antenna has dropped to 899.5-927.5MHZ because of the change in the force on the tag and no longer reaches 928MHZ, so the tag is no longer React, passing information back to the reader.

Advantageously, changes in the operating frequency of the antenna due to forces beyond a predetermined 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 change of the force causes the working frequency of the tag antenna to drift up and down and the current invention is not limited to dividing the frequency band into n channels equally.

The embodiments of the present invention can detect the change of the pressure at a lower cost, and use the energy obtained by the RFID to solve the power supply problem of the force 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 (illustrativelogical 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 (8)

1. A kind of RFID tag with force-sensitive device, it is characterized in that, two pins are arranged on the chip of described RFID tag; Described force-sensitive device links to each other with these two pins, and with described RFID tag The antenna forms a parallel structure, and the change of external force will cause the change of the resistance of the force-sensitive device itself. There is a logic circuit for controlling on-off on the line connecting the force-sensitive device and the chip of the RFID tag. The circuit and the logic circuit that controls on-off are part of the chip. The on-off of the logic circuit determines whether the force-sensitive device is connected in parallel with the antenna: when the logic circuit is disconnected, the force-sensitive device is not connected in parallel with the antenna. If the sensitive device is under pressure , the first resonant frequency and signal strength of the antenna remain unchanged; when the logic circuit is connected, the force-sensitive device is connected in parallel with the antenna, and if the sensitive device is under pressure, at least one of the characteristic frequency and signal strength of the antenna will change. When the antenna works at the second resonant frequency; the RFID tag receives the instructions sent by the RFID reader to control the on-off of the logic circuit, thereby realizing the detection of the pressure by comparing the difference between the signal strengths of different frequencies from the antenna change; Wherein, the antenna of the RFID tag is a double dipole antenna; The force-sensitive device is a pressure-sensitive conductive rubber sensitive device, and the pressure-sensitive conductive rubber sensitive device includes a first electrode, a second electrode, a pressure-sensitive conductive rubber and an insulating film, and the pressure-sensitive conductive rubber sensitive device has a switch Functional pressure-sensitive element, when pressure is applied, the pressure-sensitive conductive rubber forms a path between the first electrode and the second electrode, and when the pressure disappears, the resistance between the first electrode and the second electrode increases; When the antenna of the RFID tag enters the alternating magnetic field generated by the RFID reader, a transformer is formed between the antenna of the RFID tag and the antenna of the RFID reader to provide an energy source for the force-sensitive device, and the antenna of the RFID tag The antenna of the RFID reader is the primary coil and the secondary coil of the transformer respectively, and the force-sensitive device converts the electromagnetic wave received by the antenna of the RFID tag into a DC voltage through the interconnected charge pump and rectifier circuit to provide the The RFID tag executes the instructions sent by the RFID reader to provide the energy source. 2. The RFID tag with the force-sensitive device as claimed in claim 1, wherein when the antenna of the RFID tag is a double dipole antenna: the force-sensitive device and one of the antennas form a parallel structure; or The force-sensitive device and the two antennas simultaneously form a parallel structure. 3. An RFID tag with a force-sensitive device, characterized in that, a pin is arranged on the chip of the RFID tag; one end of the force-sensitive device is connected to this pin, and the other end is connected to the RFID tag. On the antenna of the tag, and form a parallel structure with the antenna, the change of external force will cause the change of the resistance of the force-sensitive device itself, and there is a control switch on the line connecting the force-sensitive device and the chip of the RFID tag Logic circuit, the connected line and the logic circuit that controls on-off are part of the chip. The on-off of the logic circuit determines whether the force-sensitive device is connected in parallel with the antenna: when the logic circuit is disconnected, the force-sensitive device is not connected in parallel with the antenna , if the sensitive device is under pressure, the first resonant frequency and signal strength of the antenna remain unchanged; when the logic circuit is connected, the force sensitive device is connected in parallel with the antenna, and if the sensitive device is under pressure, the characteristic frequency and signal strength of the antenna will be at least There is a change, at this time 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 realize the comparison between the signal strengths of different frequencies from the antenna. difference to detect changes in stress; Wherein, the antenna of the RFID tag is a double dipole antenna; The force-sensitive device is a pressure-sensitive conductive rubber sensitive device, and the pressure-sensitive conductive rubber sensitive device includes a first electrode, a second electrode, a pressure-sensitive conductive rubber and an insulating film, and the pressure-sensitive conductive rubber sensitive device has a switch Functional pressure-sensitive element, when pressure is applied, the pressure-sensitive conductive rubber forms a path between the first electrode and the second electrode, and when the pressure disappears, the resistance between the first electrode and the second electrode increases; When the antenna of the RFID tag enters the alternating magnetic field generated by the RFID reader, a transformer is formed between the antenna of the RFID tag and the antenna of the RFID reader to provide an energy source for the force-sensitive device, and the antenna of the RFID tag The antenna of the RFID reader is the primary coil and the secondary coil of the transformer respectively, and the force-sensitive device converts the electromagnetic wave received by the antenna of the RFID tag into a DC voltage through the interconnected charge pump and rectifier circuit to provide the The RFID tag executes the instructions sent by the RFID reader to provide the energy source. 4. The RFID tag with the force-sensitive device as claimed in claim 3, wherein when the antenna of the RFID tag is a double dipole antenna: the force-sensitive device and one of the antennas form a parallel structure; or The force-sensitive device and the two antennas simultaneously form a parallel structure. 5. An RFID tag with a force-sensitive device, characterized in that the force-sensitive device is connected to the antenna of the RFID tag, and forms a parallel structure with the antenna, and changes in external force will cause force-sensitive Changes in the resistance of the device itself, there is a logic circuit for controlling on-off on the line connecting the force-sensitive device and the antenna, the connected line and the logic circuit for controlling on-off are part of the chip, and the on-off of the logic circuit determines Whether the force-sensitive device is connected in parallel with the antenna: When the logic circuit is disconnected, the force-sensitive device is not connected in parallel with the antenna. If the sensitive device is under pressure, the first resonant frequency and signal strength of the antenna remain unchanged; when the logic circuit is connected When the force-sensitive device is connected in parallel with the antenna, if the sensitive device is under pressure, 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 signal sent by the RFID reader. Instructions to control the on and off of the logic circuit, so as to detect the change of the pressure by comparing the difference between the signal strengths of different frequencies from the antenna; Wherein, the antenna of the RFID tag is a double dipole antenna; The force-sensitive device is a pressure-sensitive conductive rubber sensitive device, and the pressure-sensitive conductive rubber sensitive device includes a first electrode, a second electrode, a pressure-sensitive conductive rubber and an insulating film, and the pressure-sensitive conductive rubber sensitive device has a switch Functional pressure-sensitive element, when pressure is applied, the pressure-sensitive conductive rubber forms a path between the first electrode and the second electrode, and when the pressure disappears, the resistance between the first electrode and the second electrode increases; When the antenna of the RFID tag enters the alternating magnetic field generated by the RFID reader, a transformer is formed between the antenna of the RFID tag and the antenna of the RFID reader to provide an energy source for the force-sensitive device, and the antenna of the RFID tag The antenna of the RFID reader is the primary coil and the secondary coil of the transformer respectively, and the force-sensitive device converts the electromagnetic wave received by the antenna of the RFID tag into a DC voltage through the interconnected charge pump and rectifier circuit to provide the The RFID tag executes the instructions sent by the RFID reader to provide the energy source. 6. The RFID tag with a force-sensitive device as claimed in claim 5, wherein when the antenna of the RFID tag is a double dipole antenna: the force-sensitive device and one of the antennas form a parallel structure; or The force-sensitive device and the two antennas simultaneously form a parallel structure. 7. A kind of RFID system with force-sensitive device, described RFID system comprises RFID label and RFID reader, it is characterized in that, The RFID tag comprises the RFID tag with a force-sensitive device described in any one of claims 1-2, or the RFID tag with a force-sensitive device described in any one of claims 3-4, or claim 5 - RFID tags with force-sensitive devices as described in any one of 6; The RFID reader sends instructions to control the on-off of the logic circuit of the RFID tag, so as to detect the change of the applied pressure by comparing the difference between the signal strengths of different frequencies from the antenna. 8. A force detection method of an RFID system with a force-sensitive device, wherein the force detection method is applied to the RFID system with a force-sensitive device as claimed in claim 7, 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 force-sensitive device is not connected in parallel with the antenna, and at this time it is placed under a certain force intensity, the first part of the antenna 1. The resonant frequency and signal strength remain unchanged; when the logic circuit is connected, the force-sensitive device is connected in parallel with the antenna. At this time, it is placed under a certain force strength, and at least one of the characteristic frequency and signal strength of the antenna will occur. change, the antenna works at the second resonant frequency; The RFID reader is used to compare the difference between the signal strengths of the different frequencies from the antenna to detect changes in the applied pressure.