CN107516054A - Structure and system of radio frequency identification passive wireless resonant sensor that can be networked arbitrarily - Google Patents

Abstract

The present invention propose it is a kind of can arbitrary networking radio frequency identification passive and wireless resonant transducer structure and system, including requestor and sensor tag；In inquiry charge cycle T1, requestor transmitting radio-frequency queries signal, sensor tag receives the radio-frequency queries signal of requestor transmitting, and coupling inquiry signal energy is maximized under impedance matching condition, is charged, now retroreflective signs are minimum；In sensing output cycle T 2, sensor tag works comprehensively, modulator control modulation switch in label is turned off and closed according to the rule of encoded signal, matching and the mismatch of matching impedance and antenna impedance are realized respectively, so as to which reflected signal strength receives wireless sensing signal according to encoded signal rule and changing features, requestor.Present invention inquiry distance is remote, can wirelessly address inquiry.

Description

Structure and system of radio frequency identification passive wireless resonant sensor that can be networked arbitrarily

technical field

The invention belongs to the technical field of passive wireless sensors, and in particular relates to a radio frequency identification passive wireless resonant sensor tag and system.

Background technique

Passive wireless sensors are especially suitable for use in specific occasions where it is inconvenient to connect, inaccessible, and unable to replace the power supply. Passive wireless sensors generally use electromagnetic waves to query the sensor wirelessly, stimulate it to generate a sensor output signal and transmit it back to the query terminal wirelessly through electromagnetic waves, and the query terminal obtains sensor parameter information by analyzing the characteristics of the sensor output signal.

Current passive wireless sensors are mainly realized by surface acoustic wave sensors. The sensing query signal of the surface acoustic wave sensor (that is, the excitation signal wirelessly transmitted from the query terminal to the surface acoustic wave sensor) and the sensor output signal (that is, the signal returned by the surface acoustic wave sensor to the query terminal) are in the same frequency band and have the same frequency , or very close in frequency. If the wireless addressing function of the surface acoustic wave sensor is to be realized, the parameters of each surface acoustic wave sensor must be different. For example, for surface acoustic wave resonators, addressing can only be achieved through the difference in resonant frequency. The resonant frequency of each sensor is different, and the required design parameters are different, which not only increases the complexity of the sensor device, but also causes the sensor performance difference.

The acquisition of the wireless sensing signal of the surface acoustic wave sensor is realized through the following two processes: 1) Sensing query: the query terminal emits the query electric wave to stimulate the surface acoustic wave sensor to work, and the surface acoustic wave sensor accumulates a certain amount of oscillation energy in the form of mechanical energy ; 2) Sensing signal acquisition: At this time, the query signal is intermittent, that is, the query signal is zero, and the mechanical oscillation signal accumulated by the surface acoustic wave sensor is converted into an electromagnetic wave signal and sent back to the query terminal. At present, the wireless query distance of the existing passive wireless surface acoustic wave sensors is very limited, and it is difficult to greatly improve it. One important reason is that the current Q value of the surface acoustic wave resonator is only about 2000 at the highest.

UHF radio frequency identification (RFID) system also uses electromagnetic wave propagation coupling to realize non-contact information transmission. The reader provides radio frequency energy for the tag, and the tag antenna receives the radio frequency energy and sends the tag's electronic code information to the reader through backscatter debugging. The maximum reading and writing distance is greater than 1m, typically up to 3-8m. The data communication rate of the UHF RFID system can reach more than 600kbit/s, and thousands of tags can be read at one time. It has been applied in traffic control, logistics management, asset management and other fields. However, since there is no physical parameter sensitive unit inside the UHF RFID tag, the UHF RFID tag cannot be used as a sensor at present.

Contents of the invention

The object of the present invention is to provide a passive resonant sensor tag and sensor system with long query distance and wireless addressable query.

In order to solve the above technical problems, the present invention provides a radio frequency identification passive wireless resonant sensor tag that can be networked arbitrarily, including a sensor end antenna, a radio frequency front end, a power supply circuit, an oscillation circuit, a sensitive element, an encoder, a memory and a modulator; The oscillating circuit and sensitive components form an oscillator; the radio frequency front end includes a matching impedance and a load modulation switch; the load modulation switch controls the matching and mismatching between the matching impedance and the antenna impedance; the power supply circuit performs coupling signal Rectification and storage, when the energy stored in the power supply circuit exceeds the threshold, the oscillator, encoder and modulator in the sensor tag are triggered to work; the sensitive element senses the parameter to be measured, and the sensitive element acts as a part of the oscillation circuit. The characteristic change caused by the action will lead to the frequency change of the oscillation signal output by the oscillation circuit; the oscillation circuit sends the oscillation signal carrying the parameter information to be measured to the encoder as an encoding clock signal; the encoder reads the pre-stored signal from the memory The address or ID information of the sensor tag, and under the control of the coded clock signal, a coded signal is generated to control the modulator to work; the coded signal contains the sensor address or ID information and the frequency information of the oscillating signal; the modulator controls the modulation switch according to The coded signal is disconnected and closed according to the law to realize the matching (opening and disconnecting) and mismatching (switching closed) of the matching impedance and the antenna impedance respectively. When the impedance is matched, the energy received by the antenna at the sensor end is coupled to the maximum, and at this time the wireless signal reflected back to the sensor interrogator is the smallest; The signal is maximum. Thus, the opening and closing of the load modulation switch causes the wireless sensing signal received by the interrogator to have a strong (1) weak (0) state change.

Further, the working cycle includes the query charging cycle T1 and the sensing output cycle T2; the sensor tag receives the RF query signal emitted by the upstream queryer during the query charging cycle T1, and reflects the wireless sensing signal to the upstream queryer during the sensing output cycle T2; There is no interval between the query charging cycle T1 and the sensing output cycle T2.

Further, the power supply circuit is composed of a diode voltage multiplier circuit, a rectifier circuit, a storage capacitor and a power management circuit; in the query charging period T1, the power circuit converts the received RF query signal into DC power and stores it in the storage capacitor. When the voltage across the storage capacitor reaches a certain value, the oscillating circuit is triggered to work and supplies power to the oscillating circuit, frequency divider, encoder, modulator and memory.

Further, when the load modulation switch is turned off, the antenna impedance at the sensor end matches the input impedance of the interrogator; when the load modulation switch is closed, the antenna impedance at the sensor end does not match the input impedance of the interrogator.

Further, the oscillating circuit is one of a gate oscillating circuit, a Pierce oscillating circuit, a Miller oscillating circuit or an RLC oscillating circuit.

Further, the sensor tag further includes a frequency divider, and the frequency-divided oscillation signal output by the oscillator is used as an encoding clock signal.

The present invention also proposes a sensor system using the sensor tag networking, including a queryer and the sensor tag. During the query charging period T1, the queryer transmits a radio frequency query signal, and the sensor tag receives the radio frequency query signal emitted by the queryer. , in the state of impedance matching to maximize the coupling query signal energy, charging, at this time the echo signal is extremely small; in the sensing output period T2, the sensor tag is fully working, and the modulator in the tag controls the modulation switch according to the law of the encoded signal Opening and closing are performed to realize the matching (opening and disconnecting) and mismatching (opening and closing) of the matching impedance and antenna impedance respectively, so that the reflected signal strength changes according to the law and characteristics of the encoded signal, and the interrogator receives the wireless sensor signal.

Further, the interrogator is composed of a DSP, a microwave source, an interrogator-side antenna, a transceiver isolator, a receiving channel, an oscillator, a clock, and an external interface; the transceiver isolator is used for transceiver isolation of radio frequency query signals and wireless sensor signals ; The microwave source generates a microwave signal under the control of the DSP, which is transmitted through the antenna of the interrogator after passing through the transceiver isolator; the wireless sensor signal is sent to the receiving channel through the transceiver isolator, and the receiving channel is filtered, amplified, detected and demodulated After decoding and sending to DSP, the DSP obtains the ID information with the sensor tag and the frequency value of the oscillation signal output by the oscillator after extracting and processing the information.

Further, the receiving channel includes a filter circuit, an amplification circuit, a detection circuit, and a demodulation and decoding circuit.

Compared with the prior art, the present invention has significant advantages in that:

(1) The present invention can use a passive resonant sensor of any frequency to form a passive wireless sensor, that is, realize wireless inquiry of any passive resonant sensor. By selecting a passive resonant sensor with a high Q value, the wireless query performance of the passive wireless sensor can be greatly improved, thereby improving the actual sensing performance of the sensor; (2) the present invention can also use resistive, capacitive, inductive, etc. The sensitive components forming the RLC oscillating circuit form a resonant sensor, which realizes the wireless inquiry of any passive resonant sensor.

Description of drawings

Fig. 1 is the structural representation of the passive wireless resonant sensor system of the present invention;

Fig. 2 is a schematic diagram of the working cycle of the sensor label;

Fig. 3 is a schematic structural diagram of a sensor tag;

Fig. 4 is a schematic diagram of the principle of using a quartz resonator as a sensitive element in the passive wireless resonant sensor system of the present invention;

Fig. 5 is a schematic diagram of the encoding method and waveform relationship between the address of the wireless sensor tag and the resonant frequency of the oscillation signal.

detailed description

It is easy to understand that, according to the technical solution of the present invention, without changing the essence of the present invention, those skilled in the art can imagine a variety of radio frequency identification passive wireless resonant sensors and systems that can be arbitrarily networked in the present invention. implementation. Therefore, the following specific embodiments and drawings are only exemplary descriptions of the technical solution of the present invention, and should not be regarded as the entirety of the present invention or as a limitation or limitation on the technical solution of the present invention.

As shown in Figure 1 and Figure 2, the radio frequency identification wireless sensor system includes an interrogator and a sensor tag, which has two working cycles: the query charging cycle T1 and the sensing output cycle T2, the query charging cycle T1 comes first, and the sensing output cycle After T1, there is no interval between the two cycles. In the query charging period T1, the interrogator generates a radio frequency interrogation signal (including the energy supply signal), and the sensor tag receives the radio frequency interrogation signal emitted by the interrogator; in the sensing output period T2, the sensor tag reflects the wireless sensing signal, and the interrogator receives the radio frequency interrogation signal. The wireless sensor signal is demodulated to obtain the parameter information measured by the sensor.

The structure of the interrogator is similar to that of the existing RFID system, mainly composed of DSP, microwave source, antenna at interrogator end, transceiver isolator, receiving channel, oscillator, clock and external interface. In the query charging period T1, the microwave source generates microwave signals under the control of the DSP, and after passing through the transceiver isolator, it is transmitted to the outside through the antenna of the query device, which is the RF query signal. The microwave signal provides microwave energy and query signals for the sensor tag. In the sensing output period T2, the antenna at the interrogator end receives the echo signal of the sensor tag, that is, the wireless sensing signal, and sends it to the receiving channel through the transceiver isolator, and the receiving channel filters, amplifies, detects, demodulates and decodes and sends it to the DSP , DSP obtains the ID information with the sensor tag and the frequency value of the oscillation signal output by the oscillator after information extraction and processing. There is a one-to-one correspondence between the frequency value of the oscillating signal and the parameter to be measured.

The receiving channel includes a filter circuit, an amplification circuit, a wave detection circuit, and a demodulation and decoding circuit.

The DSP is the working core of the query device, and the software embedded in the DSP completes tasks such as sending and receiving control, data reading and processing, external communication and networking.

The transceiver isolator is used for transmitting and receiving isolation of radio frequency query signals and wireless sensor signals, and prevents the signal of the transmitting channel from leaking to the receiving channel. The transmitting and receiving isolator can be a circulator or a leak signal canceller.

As shown in Figure 3, the sensor tag is mainly composed of sensor-side antenna, RF front-end, power supply circuit, oscillation circuit, sensitive components, frequency divider, encoder, memory and modulator.

The radio frequency front-end mainly completes the impedance matching between the antenna of the sensor end and the load, and realizes the maximum coupling of energy, so that the power supply circuit can obtain enough microwave energy. The RF front-end is equipped with a load modulation switch. When the load modulation switch is turned off, the antenna impedance at the sensor end matches the input impedance of the interrogator completely, and the energy received by the antenna at the sensor end is coupled to the maximum, and the wireless sensing signal emitted at this time is the smallest; When the load modulation switch is closed, the antenna impedance of the sensor end does not match the input impedance of the interrogator, and the wireless sensing signal transmitted at this time is the largest. The opening and closing of the load modulation switch causes the wireless sensing signal received by the interrogator to have a strong (1) weak (0) state change.

The power supply circuit is mainly composed of a diode voltage multiplier circuit, a rectification circuit, a storage capacitor and a power management circuit. In the query charging period T1, the power circuit converts the microwave energy into DC energy and stores it in the storage capacitor. When the voltage across the storage capacitor reaches a certain value, the sensor tag is triggered to work, that is, the oscillation circuit is triggered to work and provides the oscillation circuit, the distribution The frequency converter, encoder, modulator and memory are powered, and the sensor tag enters the sensing output cycle T2 at this time.

The oscillating circuit and the sensitive component together constitute an oscillator. The frequency of the oscillating signal output by the oscillator is related to the sensitive component. When the sensitive component senses the change of the parameter to be measured, the frequency of the oscillating signal will change.

The sensitive element can be various sensitive elements that can be placed in the oscillating circuit, and the characteristic is that the sensitive element has the characteristics of resistance R, capacitance C or inductance L. When the parameter to be measured by the sensor changes, it can cause changes in the resistance R, capacitance C, and inductance L, or cause changes in the impedance formed by the R, L, C or RLC circuit, resulting in the frequency of the oscillation signal output by the oscillation circuit. Variety. In this case, there is a one-to-one correspondence between the frequency of the oscillating signal output by the oscillating circuit (ie, the resonant frequency of the oscillating circuit) and the parameter to be measured by the sensor. For example, the sensitive element may be a temperature sensor based on a quartz resonator, or various sensors based on a quartz crystal resonator such as a quartz crystal microbalance. The sensitive element can also be a magnetoresistive, magnetic impedance or capacitive humidity sensitive element (that is, the capacitance value of the sensitive element changes with humidity). Corresponding to the example of the above-mentioned sensitive components, the resonant frequency of the oscillator composed of the quartz crystal resonator and the oscillation circuit mainly depends on the quartz crystal resonator; if the magnetoresistance, magneto-impedance element and capacitance change element are used as the peripheral components of the oscillation circuit, then the oscillator The resonant frequency of the sensor is related to the values of these elements (such as the resistance value of the magnetoresistive element, the capacitance value of the capacitive element, etc.), and the values of these elements have a one-to-one correspondence with the parameters to be measured.

The oscillating circuit can be various low power oscillating circuits, such as gate oscillating circuit, Pierce oscillating circuit, Miller oscillating circuit and so on.

The oscillating signal output by the oscillator is used as the encoding clock signal after frequency division, or directly as the encoding clock signal without frequency division), the encoder reads the pre-stored address or ID information of the sensor label from the memory, and Under signal control, a coded signal is generated to control the modulator to work.

The memory stores the address or ID information of the sensor tag, which can be EEPROM (Electrically Erasable Read-Only Memory), read only and not write.

The output waveform of the encoder contains two parts of information, the first part is the address or ID information of the sensor label, and the second part is the frequency information of the oscillation signal. For example, the data code of this part is 0101010101010101, then the demodulated data The waveform is consistent with the clock waveform period/frequency.

The modulator is a load modulator, which is consistent with the load modulation principle and modulator composition in the existing RFID system. Add the encoded waveform sent by the encoder to the modulation tube (such as MOSFET) in the modulator, control the load modulation switch of the RF front end to "open" and "close" the beat of the encoded waveform, and make the antenna impedance of the interrogator end and the interrogator The input impedance of the interrogator changes between matching and mismatching, so that the microwave power emitted by the interrogator is absorbed by the maximum (corresponding to impedance matching) and the minimum (corresponding to impedance mismatch); correspondingly, the microwave power transmitted to the interrogator The sense signal is minimized (state 0, corresponding to impedance match) and maximized (state 1, corresponding to impedance mismatch). After receiving the wireless sensing signal returned by the sensor tag, the interrogator demodulates the data clock information of the coded data, so as to further obtain the corresponding sensor tag address and oscillation resonance frequency.

Example

In conjunction with Fig. 4, in the present embodiment, the oscillating circuit adopts a gate oscillating circuit, and the sensitive element adopts a quartz resonant sensor; the oscillator is composed of a gate oscillating circuit and a quartz resonant sensor; correspondingly matching impedance Z _L load modulation switch S constitutes a radio frequency front end; A rectifier circuit, an energy storage capacitor and a power management circuit form a power circuit. Suppose Z _A is the antenna impedance at the sensor end, and Z _L is the input impedance of the sensor tag.

In the query charging cycle T1, the load modulation switch S is turned off, the sensor antenna is in the load matching state, the microwave power transmitted by the query is absorbed to the maximum, the wireless sensing signal returned to the query is the smallest, and the sensor tag absorbs radio frequency Query signal, the signal is rectified by the rectifier circuit to charge the storage capacitor, and the voltage is sent to the power management circuit, when the voltage Vdd across the capacitor is large enough, the power management circuit triggers the oscillator to work, and the sensor label enters the sensing output cycle T2 , the power management circuit simultaneously outputs four voltages for the gate oscillation circuit, frequency divider, encoder and modulator respectively. In the sensing output period T2, the modulator controls the load modulation switch S to periodically open and close at the frequency of the oscillation signal or its frequency-divided signal. When the load modulation switch S is closed, the antenna load at the sensor end is short-circuited. At this time, the wireless sensing signal received by the interrogator is the strongest, and when the load modulation switch S is closed, as shown above, the wireless sensing signal received by the interrogator is the weakest. During the sensing output period T2, the working state of the sensor tag is a power consumption process, which causes the voltage Vdd across the storage capacitor to drop. When the voltage Vdd drops to a certain value and cannot maintain the working state, the charging process is restarted, and the system is maintained at working status.

Figure 5 shows an example of the encoding method of the sensor tag address and resonance frequency and the waveform relationship. In Fig. 5, the address and frequency code data are stored in the memory, the first four digits 1011 represent the address, and the following digits 0101010101... represent the frequency code. The frequency of the oscillation signal is fr, which is determined by the resonant frequency of the resonant sensor. After the frequency of the oscillation signal is divided by 4, it is used as the encoded data clock to control the encoder to output the corresponding encoded signal. The interrogator demodulates the coded signal to inversely calculate the value of the resonant frequency.

Claims (9)

1. it is a kind of can arbitrary networking radio frequency identification passive and wireless resonant transducer label, it is characterised in that including sensor side Antenna, radio-frequency front-end, power circuit, oscillating circuit, sensing element, encoder, memory and modulator；The oscillating circuit Oscillator is formed with sensing element；

The radio-frequency front-end includes matching impedance and load modulation switch；The load modulation switch control the matching impedance with The matching of antenna impedance and mismatch；

The power circuit carries out rectification and storage to coupled signal, when the energy of power circuit storage exceedes threshold value, triggering Oscillator, encoder and modulator work；

The sensing element senses parameter to be measured；

The oscillator signal for carrying parameter information to be measured is delivered to encoder as encoded clock signal by the oscillating circuit；

The encoder reads the sensor tag address prestored or id information from memory, and in encoded clock signal Control under produce encoded signal, control modulator work；The encoded signal includes sensor address or id information and shaken Swing the frequency information of signal；

After the modulator modulates encoded signal, launched under the control of load modulation switch by sensor side antenna Go.

2. as claimed in claim 1 can arbitrary networking radio frequency identification passive and wireless resonant transducer label, it is characterised in that work Make the cycle comprising inquiry charge cycle T1 and sense output cycle T 2；Sensor tag receives upstream in inquiry charge cycle T1 and looked into The radio-frequency queries signal for asking device transmitting is charged, and is exported cycle T 2 in sensing and reflected wireless sensing signal to upper stream queries Device；Inquire about between charge cycle T1 and sensing output cycle T 2 without interval.

3. as claimed in claim 2 can arbitrary networking radio frequency identification passive and wireless resonant transducer label, it is characterised in that institute Power circuit is stated to be made up of diode voltage multiple circuit, rectification circuit, storage capacitance and electric power management circuit；Filled in inquiry In electric cycle T 1, the radio-frequency queries signal of reception is converted to direct current energy and stored into storage capacitance by power circuit, when depositing When the voltage that storing up electricity holds both ends reaches certain numerical value, Triggered Oscillation circuit works and is oscillating circuit, frequency divider, encoder, tune Device and memory power supply processed.

4. as claimed in claim 2 can arbitrary networking radio frequency identification passive and wireless resonant transducer label, it is characterised in that when When loading modulation switch disconnection, the input resistant matching of sensor side antenna impedance and requestor；When load modulation switch closure When, the input impedance mismatch of sensor side antenna impedance and requestor.

5. as claimed in claim 2 can arbitrary networking radio frequency identification passive and wireless resonant transducer label, it is characterised in that institute Oscillating circuit is stated as one kind in door oscillating circuit, Pierce oscillator circuit, Miller oscillating circuit or RLC oscillating circuits.

6. as claimed in claim 2 can arbitrary networking radio frequency identification passive and wireless resonant transducer label, it is characterised in that also Including frequency divider, the oscillator signal of oscillator output is used as encoded clock signal after frequency dividing.

7. a kind of usage right requires the sensing system of sensor tag networking described in 1-6, it is characterised in that including requestor With the sensor tag；In inquiry charge cycle T1, requestor transmitting radio-frequency queries signal, sensor tag receives inquiry The radio-frequency queries signal of device transmitting and the energy that coupled RF inquiry signal is maximized under impedance matching condition；Exported in sensing In cycle T 2, the modulator control modulation switch in sensor tag is turned off and closed according to the changing rule of encoded signal Close, so as to the wireless sensing signal that reflected signal strength is changed according to encoded signal rule, requestor receives described wireless Transducing signal.

8. sensing system as claimed in claim 7, it is characterised in that the requestor is by DSP, microwave source, requestor end day Line, transceiver insulation device, receiving channel, oscillator, clock and external interface composition；The transceiver insulation device is used for radio-frequency queries The transceiver insulation of signal and wireless sensing signal；The microwave source produces microwave signal under DSP controls, passes through transceiver insulation device Externally launch by requestor end antenna；Wireless sensing signal delivers to DSP through transceiver insulation device and receiving channel, and DSP enters The frequency values with sensor tag information and oscillator signal are obtained after row information processing.

9. sensing system as claimed in claim 8, it is characterised in that the receiving channel include filter circuit, amplifying circuit, Detecting circuit and demodulation and decoding circuitry.