CN111325302B - Passive wireless magnetic field characteristic sensing label and sensing system - Google Patents
Passive wireless magnetic field characteristic sensing label and sensing system Download PDFInfo
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- CN111325302B CN111325302B CN202010127783.5A CN202010127783A CN111325302B CN 111325302 B CN111325302 B CN 111325302B CN 202010127783 A CN202010127783 A CN 202010127783A CN 111325302 B CN111325302 B CN 111325302B
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06K—GRAPHICAL DATA READING; PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS
- G06K19/00—Record carriers for use with machines and with at least a part designed to carry digital markings
- G06K19/06—Record carriers for use with machines and with at least a part designed to carry digital markings characterised by the kind of the digital marking, e.g. shape, nature, code
- G06K19/067—Record carriers with conductive marks, printed circuits or semiconductor circuit elements, e.g. credit or identity cards also with resonating or responding marks without active components
- G06K19/07—Record carriers with conductive marks, printed circuits or semiconductor circuit elements, e.g. credit or identity cards also with resonating or responding marks without active components with integrated circuit chips
- G06K19/077—Constructional details, e.g. mounting of circuits in the carrier
- G06K19/07749—Constructional details, e.g. mounting of circuits in the carrier the record carrier being capable of non-contact communication, e.g. constructional details of the antenna of a non-contact smart card
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06K—GRAPHICAL DATA READING; PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS
- G06K17/00—Methods or arrangements for effecting co-operative working between equipments covered by two or more of main groups G06K1/00 - G06K15/00, e.g. automatic card files incorporating conveying and reading operations
- G06K17/0022—Methods or arrangements for effecting co-operative working between equipments covered by two or more of main groups G06K1/00 - G06K15/00, e.g. automatic card files incorporating conveying and reading operations arrangements or provisious for transferring data to distant stations, e.g. from a sensing device
- G06K17/0029—Methods or arrangements for effecting co-operative working between equipments covered by two or more of main groups G06K1/00 - G06K15/00, e.g. automatic card files incorporating conveying and reading operations arrangements or provisious for transferring data to distant stations, e.g. from a sensing device the arrangement being specially adapted for wireless interrogation of grouped or bundled articles tagged with wireless record carriers
Abstract
The invention discloses a passive wireless magnetic field characteristic sensing label and a sensing system, and particularly relates to a passive resonance type magnetic field quantity sensor integrated in a board-level passive electronic label, which is matched with a reader-writer and an upper computer to build a magnetic field sensing system based on an RFID technology, so that high-precision and high-intelligent monitoring of magnetic field quantity is realized; through the design of the passive resonance type magnetic field sensing label with the single and double sensor acquisition modes compatible, the acquisition modes can be switched according to the control of a reader-writer, and the problems that the existing small-sized magnetic field sensing system based on the RFID technology has a single operation mode, small secondary development space, incapability of guaranteeing precision and sensitivity and the like are solved. The scheme of the invention can monitor a constant magnetic field and an alternating magnetic field, and is particularly suitable for monitoring the magnetic field of power transmission equipment in a large power transmission center.
Description
Technical Field
The invention belongs to the technical field of wireless sensor networks, and particularly relates to a magnetic field sensing technology.
Background
The magnetic field exists in the aspects of human life, and influences the survival and life of human beings. Human beings are dedicated to the utilization and monitoring of magnetic fields all the time, and in some special fields, such as military affairs, industrial production etc. it is especially important to the monitoring of magnetic field, therefore the emergence of many magnetic field intensity test equipment, these magnetic field intensity test equipment often have good measurement accuracy, but because its volume often is huge, the consumption is high, in addition need artifical intervention to accomplish the measurement, and be not suitable for in some special occasions to carry out high accuracy, high frequency, high intelligent monitoring activities to magnetic field volume.
Wireless Sensor Networks (WSNs) are considered the second largest network behind the internet, known as one of the most influential technologies in the 21 st century, and are distributed Sensor Networks whose tips are sensors that can sense the outside world. The sensors in the WSN communicate in a wireless mode, the network is flexibly set, the position of equipment can be changed at any time, and the equipment can be connected with the Internet in a wired or wireless mode. Therefore, the wireless sensor network is introduced into the field of magnetic field quantity monitoring, and a plurality of problems in the prior magnetic field quantity monitoring can be solved.
Radio Frequency Identification (RFID) technology is a traditional wireless communication Identification technology, can realize non-line-of-sight communication, and is widely applied to the fields of intelligent logistics, traffic, multi-target Identification, direction tracking and the like. The RFID technology is applied to the wireless sensing network, can have the technical characteristics of both the RFID and the wireless sensing network, automatically identifies the target through the RFID radio frequency signal, transmits the sensor signal at high frequency and in a long distance, and is a second choice for realizing intelligent magnetic field quantity monitoring.
The passive electronic tag, namely the passive radio frequency tag, adopts a frequency hopping working mode, has the anti-jamming capability, can self-define and read standard data by a user, and has the reading distance of more than ten meters. The passive radio frequency tag has a wide working frequency band, not only accords with relevant industry regulations, but also can be developed and applied flexibly, and a special reader-writer can read and write a plurality of tags simultaneously. Due to the passive working characteristic, a battery is not needed in the design of the tag, and the memory of the tag can be repeatedly erased and written for more than 100000 times. Because the passive electronic tag is not provided with a built-in battery, the electronic tag collects electric energy required by the work of the passive electronic tag from radio frequency energy emitted by the reader-writer within the communication identification range of the reader-writer. The passive electronic tag generally adopts a backscattering mode to complete the transmission of electronic tag information to a reader-writer, so the passive electronic tag can also be called as a passive tag and is an excellent carrier for realizing a wireless magnetic field quantity sensor network based on an RFID technology.
The existing magnetic field sensing technology mainly comprises two types, wherein the first type is medium-large conventional magnetic field monitoring equipment, mainly desktop equipment and actively working, such as a magnetometer and the like; the second type is a small magnetic field sensing system based on RFID technology, which works semi-actively or passively and is realized by a self-made or commercial magnetic field sensor chip.
The main defects of the existing magnetic field sensing technology generally comprise:
1) the medium and large conventional magnetic field quantity monitoring equipment generally has higher power consumption, basically adopts an active mode to operate, puts forward a certain requirement on a fixed power supply or a portable battery, increases the cost of periodic maintenance, and shows considerable limitation in some special environments where the power supply cannot be installed or the battery cannot be replaced.
2) The small magnetic field sensing system based on the RFID technology has the problems of single acquisition mode, small space for secondary development, incapability of guaranteeing precision and sensitivity and the like, and has fewer research results and lower popularity.
Disclosure of Invention
In order to solve the above problems in the prior art, the present invention provides a passive wireless magnetic field characteristic sensing tag.
The specific technical scheme of the invention is as follows: a passive wireless magnetic field property sensing tag, comprising: an antenna, an impedance matching network circuit and a power divider circuit, a rectification and energy management circuit, an LDO (linear regulator) set (No. 1 LDO and No. 2 LDO), a demodulation circuit, a processor, a magnetic field characteristic sensing circuit, a selection switch circuit and a backscattering circuit, wherein,
the magnetic field characteristic sensing circuit is used for sensing the magnetic field quantity of the position where the label is located;
the antenna, the impedance matching network circuit and the power divider circuit are used for receiving and distributing radio frequency signals and radio frequency energy sent by the reader-writer;
the rectification and energy management circuit is used for converting radio frequency energy into direct current electric energy available for the label, storing the direct current electric energy and intermittently supplying the direct current electric energy to the label for working and using;
the LDO group provides direct current voltage for each circuit module of the tag;
the demodulation circuit is used for demodulating a command signal sent by the reader-writer and converting the command signal into a baseband signal;
the processor is used for analyzing the reader-writer command and controlling the label to work according to the reader-writer command;
the selection switch circuit is a one-out-of-three channel selection switch and is connected with a signal channel required by a reader-writer command under the control of the processor;
and the backscattering circuit sends a signal to the reader-writer in a backscattering mode under the control of the modulation signal.
Further, the processor is specifically a single chip microcomputer.
The invention also provides a passive wireless magnetic field characteristic sensing system which comprises a plurality of passive wireless magnetic field characteristic sensing labels arranged in the magnetic field environment to be detected, a reader-writer for reading and writing the labels and an upper computer for controlling the reader-writer.
The invention has the beneficial effects that: the passive resonance type magnetic field quantity sensor is integrated in the board-level passive electronic tag, and a magnetic field sensing system based on the RFID technology is built by matching with a reader-writer and an upper computer, so that the high-precision and high-intelligent monitoring of the magnetic field quantity is realized; through the design of the passive resonance type magnetic field sensing label with the single and double sensor acquisition modes compatible, the acquisition modes can be switched according to the control of a reader-writer, and the problems that the existing small-sized magnetic field sensing system based on the RFID technology has a single operation mode, small secondary development space, incapability of guaranteeing precision and sensitivity and the like are solved. The scheme of the invention can be applied to various fields, can monitor a constant magnetic field and an alternating magnetic field, and is particularly suitable for monitoring the magnetic field of power transmission equipment in a large-scale power transmission center.
Drawings
Fig. 1 is a schematic structural diagram of a passive wireless magnetic field characteristic sensing tag based on an uhf RFID technology according to an embodiment of the present invention.
Fig. 2 is a schematic diagram of a magnetic field characteristic sensing circuit according to an embodiment of the present invention.
Fig. 3 is a schematic structural diagram of a resonant magnetic field quantity sensor according to an embodiment of the present invention.
Fig. 4 is a schematic diagram of an equivalent circuit of a resonant magnetic field quantity sensor according to an embodiment of the present invention.
Fig. 5 is a schematic structural diagram of a sensor excitation circuit according to an embodiment of the present invention.
Fig. 6 is a schematic diagram of a working flow of a sensing tag according to an embodiment of the present invention.
Fig. 7 is a schematic structural diagram of a sensing system according to an embodiment of the invention.
FIG. 8 is a schematic diagram of a working flow of a sensing system according to an embodiment of the present invention.
Detailed Description
The embodiments of the present invention will be further described with reference to the accompanying drawings.
The structure of the passive wireless magnetic field characteristic sensing tag provided by this embodiment is shown in fig. 1, and specifically includes: the device comprises an antenna, an impedance matching network circuit, a power divider circuit, a rectification and energy management circuit, an LDO group (No. 1 LDO and No. 2 LDO), a demodulation circuit, a processor, a magnetic field characteristic sensing circuit, a selection switch circuit and a backscattering circuit.
The magnetic field characteristic sensing circuit is used for sensing the magnetic field quantity of the position where the label is located; the antenna, the impedance matching network circuit and the power divider circuit are used for receiving and distributing radio frequency signals and radio frequency energy sent by the reader-writer; the rectification and energy management circuit is used for converting radio frequency energy into direct current electric energy available for the label, storing the direct current electric energy and intermittently supplying the direct current electric energy to the label for working and using; the LDO group provides high-precision direct current voltage for each circuit module of the tag; the demodulation circuit is used for demodulating the command signal sent by the reader-writer and converting the command signal into a baseband signal; the processor is used for analyzing the reader-writer command and controlling the label to work according to the reader-writer command; the selection switch circuit is a one-out-of-three channel selection switch and is connected with a signal channel required by a reader-writer command under the control of the processor; the backscattering circuit sends signals to the reader-writer in a backscattering mode under the control of the modulation signals.
In this embodiment, the processor is specifically a single chip microcomputer.
The magnetic field characteristic sensing circuit provided by the embodiment is of a single-sensor acquisition mode and a dual-sensor acquisition mode, and is shown in fig. 2 below. The circuit specifically includes: the sensor comprises a double-sensor acquisition mode switch, a sensor 1 exciting circuit, a sensor 2 exciting circuit, an exclusive OR gate circuit, a low-pass filter, an inverter and a buffer which are sequentially connected, wherein the sensor 1 and the sensor 1 exciting circuit independently operate and work in a single-sensor acquisition mode, and a signal output port of the single-sensor acquisition mode outputs a 37KHz-39KHz square wave signal. The dual-sensor acquisition mode switch is switched on in a dual-sensor acquisition mode, the sensor No. 1 exciting circuit, the sensor No. 2 exciting circuit, the XOR gate circuit, the low-pass filter, the inverter and the buffer operate and work after the dual-sensor acquisition mode switch is switched on, and a 300Hz-500Hz square wave signal is output through the dual-sensor acquisition mode output signal port.
The single sensor acquisition mode has the characteristics that: the power consumption is low (the total power consumption of the magnetic field characteristic sensing circuit is one third of that of a double-sensor acquisition mode), and the precision is slightly low (the single-sensor acquisition mode has temperature drift in an application environment with large temperature fluctuation and influences the measurement precision).
The double-sensor acquisition mode is characterized in that: the sensor has the advantages of high precision (common mode noise introduced by temperature drift can be inhibited in an application environment with large temperature fluctuation, the sensor is not influenced by the temperature drift in measurement precision), high power consumption (the total power consumption of the magnetic field characteristic sensing circuit is three times of that of a single sensor in a working mode), and low efficiency (the frequency of return signals is low, and the period is long). According to the omnibearing consideration of the requirements of precision, working efficiency, tag power consumption, tag working distance and the like in different application environments, the invention provides a method for coordinating the precision, efficiency and power consumption of a system by adopting a double-sensor and single-sensor cooperative work mode to meet different application requirements.
The single sensor acquisition mode is a default working mode of the magnetic field characteristic sensing circuit, after the single chip microcomputer analyzes a single sensor acquisition mode command sent by the reader-writer, the single chip microcomputer sends a magnetic field characteristic sensing circuit enabling signal to the No. 2 LDO, the No. 2 LDO provides high-precision direct current voltage for the magnetic field characteristic sensing circuit to operate, and at the moment, the magnetic field characteristic sensing circuit is only in the single sensor acquisition mode, namely only one sensor and an excitation circuit of the magnetic field characteristic sensing circuit are powered to operate. In the initial state of zero magnetic field, the output square wave signal of the magnetic field characteristic sensing circuit is 37kHz-39kHz, when the magnetic field quantity is sensed to change, such as the magnetic field intensity is enhanced, the output square wave signal changes along with the change (the frequency is higher) of the resonant frequency of the sensor, and vice versa. It should be noted that although the single sensor acquisition mode has low power consumption and high efficiency, and the communication time between the tag and the reader-writer after one-time charging is long, the single sensor is inevitably affected by temperature drift, and the measurement accuracy is easily affected in an application environment with large temperature fluctuation, so the single sensor acquisition mode is more suitable for application in an application environment with relatively constant temperature and long communication time between the tag and the reader-writer.
After the single chip microcomputer analyzes a double-sensor acquisition mode command sent by the reader-writer, the single chip microcomputer turns on a double-sensor acquisition mode switch in the magnetic field characteristic sensing circuit through an enabling signal, at the moment, the magnetic field characteristic sensing circuit is in a double-sensor acquisition mode, namely, the magnetic field characteristic sensing circuit is provided with two sensors, an exciting circuit of the sensors and a signal conditioning circuit (an exclusive-or gate circuit, a low-pass filter, an inverter and a buffer) for operating. The two sensor excitation circuits output square wave signals (both 37kHz-39kHz) which are connected to two input ports of the exclusive-OR gate, the output signals of the exclusive-OR gate are superposition of difference frequency signals of the two input signals and higher harmonic components, the output of the exclusive-OR gate is filtered by a low-pass filter to obtain difference frequency signals of two sensor resonance signals, the difference frequency signals are sine signals with the frequency of 300Hz-500Hz, the sine signals are converted into same-frequency square wave signals through an inverter, and the square wave signals are output after passing through a buffer. It should be noted that although the dual-sensor acquisition mode has high power consumption and low efficiency, and the communication time between the tag and the reader-writer after one-time charging is short, the dual-sensor acquisition mode can suppress common-mode interference caused by temperature drift, and can ensure measurement accuracy in an application environment with large temperature fluctuation, so that the dual-sensor acquisition mode is suitable for application in an application environment with large temperature fluctuation and no longer communication time between the tag and the reader-writer.
In this embodiment, the sensor used in the magnetic field characteristic sensing circuit is specifically a resonant magnetic field quantity sensor, which is made of a magnetostrictive material and has a high Q value (not less than 10)4) The quartz crystal resonator of (2) is composed as shown in fig. 3. The magnetostrictive material generates elongation or shortening deformation under the action of a magnetic field, and the deformation is transmitted to the quartz crystal resonator, so that the resonant frequency of the whole sensor is changed. Resonant frequency of the sensor: 37kHz-39 kHz; measuring range: + -50 Oe; sensitivity: 3.5Hz/Oe, the equivalent circuit of the resonant type magnetic field quantity sensor is shown in FIG. 4.
In this embodiment, the sensor excitation circuit is configured to excite the resonant magnetic field quantity sensor to operate using a gate oscillation circuit, and a typical circuit is shown in fig. 5. A Schmitt trigger chip and a gate circuit oscillation starting mode are adopted for exciting a sensitive element to generate oscillation output, and an output signal of the circuit is a square wave. The working principle is as follows: the oscillation circuit is composed of an amplifier, an inverter and a feedback network, when the closed loop gain of the loop is larger than or equal to 1, the total phase shift of the loop is zero or any integral multiple of 2 pi (360 degrees), the oscillation circuit can be ensured to be positioned at the resonance frequency of the resonance type magnetic field quantity sensor, the feedback resistor is used for ensuring that the first inverter works in the linear region of the oscillation circuit as the amplifier, the second inverter ensures that the total phase shift of the loop is 2 pi (360 degrees), the resonance type magnetic field quantity sensor is used as the feedback network of the oscillator and is used for determining the output signal frequency of the oscillation circuit, the output signal of the oscillator is a sine wave signal, the third inverter converts the sine wave signal into a square wave signal with the same frequency, and ensures that the signal amplitude is consistent with the power supply voltage.
When the system works, the reader-writer sends a radio frequency signal to the passive resonance type magnetic field quantity sensing tag according to an upper computer program, the radio frequency signal is divided into two parts through the antenna, the impedance matching network circuit and the power divider circuit, one part of the radio frequency signal enters the rectification and energy management circuit in the form of RF energy (radio frequency energy) to be used for converting the radio frequency energy into available direct current electric energy of the tag, the direct current electric energy is stored, and when the stored direct current electric energy reaches a certain threshold value, the rectification and energy management circuit provides direct current voltage for the LDO group (LDO No. 1 and LDO No. 2).
The LDO No. 1 is in a power-on state, namely in an on state, and does not need an additional enabling signal. After receiving the direct current electric energy provided by the rectification and energy management circuit, the high-precision direct current voltage is provided for the demodulation circuit, the single chip microcomputer and the selection switch circuit to operate, so that the passive resonance type magnetic field quantity sensing label is partially electrified at the moment and can receive a command signal sent by a reader-writer. When the reader-writer sends an RFID general command to the tag, a command signal is demodulated by the electrified demodulation circuit in the form of an RF signal through the antenna, the impedance matching network circuit and the power divider circuit and converted into a baseband signal to be sent to the single chip microcomputer, the single chip microcomputer sends a general command return signal (baseband signal) to the selection switch circuit through a specified channel after analyzing, the single chip microcomputer controls the selection switch to select a corresponding channel, the modulation signal output by the selection switch at the moment is the general command return signal, and the backscattering circuit sends an ASK type general command return signal to the reader-writer in a backscattering mode under the control of the modulation signal.
The LDO No. 2 is in a power-on unopened state and needs to be enabled to be opened. After the single-chip microcomputer analyzes a single-sensor acquisition mode command sent by the reader-writer, the single-chip microcomputer sends a magnetic field characteristic sensing circuit enabling signal to the LDO No. 2, the LDO No. 2 is started immediately, and high-precision direct-current voltage is provided for the magnetic field characteristic sensing circuit to operate. At the moment, the magnetic field characteristic sensing circuit is only in a single sensor acquisition mode, namely only one sensor and an excitation circuit thereof in the magnetic field characteristic sensing circuit operate, an output signal (37kHz-39kHz square wave signal) of the magnetic field characteristic sensing circuit in the single sensor acquisition mode is a magnetic field quantity parameter signal and is sent to the selection switch circuit through a specified channel, the single chip microcomputer controls the selection switch to select the corresponding channel, a modulation signal output by the selection switch at the moment is a magnetic field quantity parameter signal in the single sensor acquisition mode, and the backscattering circuit sends the magnetic field quantity parameter signal in the ASK type single sensor acquisition mode to the reader-writer in a backscattering mode under the control of the modulation signal.
After the single chip microcomputer analyzes a double-sensor acquisition mode command sent by the reader-writer, the single chip microcomputer turns on a double-sensor acquisition mode switch in the magnetic field characteristic sensing circuit through an enabling signal, at the moment, the magnetic field characteristic sensing circuit is in a double-sensor acquisition mode, namely, two sensors, an exciting circuit and a signal conditioning circuit in the magnetic field characteristic sensing circuit operate, the output signal (300Hz-500Hz square wave signal) of the magnetic field characteristic sensing circuit in a double-sensor acquisition mode is a magnetic field parameter signal, the magnetic field parameter signals under the ASK type dual-sensor acquisition mode are sent to the reader-writer by the backscattering circuit under the control of the modulation signals. The tag operates in a power-on state until the direct current electric energy stored in the rectification and energy management circuit is exhausted, namely the tag is powered off and stops working until the tag is powered on and activated again by the radio-frequency signal sent by the reader-writer next time, and thus the intermittent sensing of the magnetic field quantity of the environment to be detected is realized.
The passive resonance Type magnetic field sensing tag provided by the invention follows ISO/IEC 18000-6Type C standard, and the function of a read command is expanded on the basis of the passive resonance Type magnetic field sensing tag, and the work flow of the passive resonance Type magnetic field sensing tag is shown in FIG. 6. When the tag is powered on, the MCU executes initialization, and then enters a low power consumption mode to wait for the reader to send a command. After the tag receives the command of the reader-writer, if the command is a universal command, executing all commands according to ISO/IEC 18000-6Type C standard; when the tag receives a single-sensor acquisition mode command, the tag firstly starts a single sensor and an excitation circuit thereof, then selects the output of the magnetic field characteristic sensing circuit in the single-sensor acquisition mode as the output (outputs 37kHz-39kHz square waves) through a three-channel selection switch, and determines the duration Ta of returning square waves according to the number of read data in the read command; when the tag receives a double-sensor acquisition mode command, the tag firstly starts the double sensor and an excitation circuit thereof and a subsequent conditioning circuit, then selects the output of the magnetic field characteristic sensing circuit in the double-sensor acquisition mode as the output (outputs 300Hz-500Hz square waves) through a three-out-of-one channel selection switch, and determines the duration Tb of returning the square waves according to the number of read data in the read command.
Based on the tags of the above embodiments, this embodiment further provides a passive wireless magnetic field characteristic sensing system based on the ultrahigh frequency RFID technology, as shown in fig. 7, including a plurality of passive resonance type magnetic field sensing tags arranged in a magnetic field environment to be measured, a reader/writer for reading and writing the tags, and an upper computer for controlling the reader/writer.
The upper computer mainly controls the working state of the reader-writer and displays the parameter information of the magnetic field quantity returned by the label; the reader-writer is controlled by the upper computer to work, and sends a radio frequency signal to the tag group, wherein the radio frequency signal comprises radio frequency energy and a command, the passive resonance type magnetic field sensing tag is charged and activated in a wireless mode, the activated tag is controlled to work according to a working mode set by the upper computer (the working mode can be an RFID (radio frequency identification) general working mode, a double-sensor acquisition mode and a single-sensor acquisition mode), the magnetic field parameter of the environment where the tag is located is sensed by the tag and then is transmitted back to the reader-writer in a frequency signal mode, and the magnetic field parameter corresponding to the frequency signal is displayed in the upper computer; the passive resonance type magnetic field sensing tag is placed in an environment to be detected, a radio frequency signal sent by a reader-writer is received through an antenna and converted into direct current electric energy capable of working by the reader-writer and stored, when the stored direct current electric energy is enough for the tag to normally work, the tag is powered on, the reader-writer sends a command to be activated, a magnetic field characteristic sensing circuit in the tag is operated according to a working mode set by an upper computer, magnetic field quantity parameters of the environment are sensed and then transmitted back to the reader-writer in a frequency signal mode until the stored direct current electric energy is exhausted, the tag is powered off and stops working until the radio frequency signal sent by the reader-writer at the next time enables the tag to be powered on again and activated, and therefore intermittent monitoring on the magnetic field quantity of the environment to be detected is achieved. The method can ensure that the sensing range of the passive wireless magnetic field characteristic sensing system is large enough (namely, the effective communication distance between the reader and the tag is far enough, generally more than 4 meters). In a system with a plurality of passive resonance Type magnetic field sensing tags working, in order to solve the problem of collision, the invention provides the meaning of expanding the data number of reading commands of an ISO/IEC 18000-6Type C standard, so that the overall efficiency of the system is improved, and the anti-collision function of the plurality of tags is realized.
The passive wireless magnetic field characteristic sensing system can comprise a reader-writer and a plurality of tags, when the passive wireless magnetic field characteristic sensing system works, the reader-writer first stores the tags around the reader-writer and records all the stored tags (the repeated tags are recorded only once), and then the tags are selected to realize a general function or magnetic field quantity sensing (single-sensor acquisition or double-sensor acquisition). In order to be compatible with ISO/IEC 18000-6Type C standard, the read command is expanded, when a user storage area is read and the read address is 0x10, magnetic field quantity sensing is carried out by using a single sensor; when the user storage area is read and the read address is 0x12, it indicates that the dual sensor is used for magnetic field amount sensing.
Because the square wave frequency difference output by the magnetic field characteristic sensing circuit in the single sensor acquisition mode and the double sensor acquisition mode is large, in order to improve the system efficiency and avoid the collision phenomenon of multiple tags, the invention provides that the duration of the square wave returned by the tag is represented by the number of read data in a read command (when the highest bit is 1, the last 7 bits can be used for representing the duration of the square wave, and the specific duration represented by each bit is defined according to specific application), and the length of the duration can be selected according to application scenes. The longer the duration, the higher the accuracy of the frequency of the return signal measured by the reader/writer. The sensing system workflow is shown in fig. 8.
In conclusion, the passive resonance type sensor is integrated in the board-level electronic tag, so that the passive resonance type sensor has the advantages of low cost, low power consumption and convenience in maintenance, the sensing system has the effects of high precision and large sensing range, and the passive resonance type sensor has the following characteristics:
1. through the design of the passive resonance type magnetic field sensing label compatible with the single sensor acquisition mode and the double sensor acquisition mode, the acquisition modes can be switched according to the control of a reader-writer, and different application requirements can be met.
2. And detecting the system sensing of the corresponding environmental magnetic field quantity parameter through the frequency signal returned by the label.
3. On the basis of being compatible with ISO/IEC 18000-6Type C standard, the meaning of user storage area and address representation of an extended reading command is provided, so that a user-defined magnetic field quantity acquisition command is realized, and the function that a tag can select a single sensor or double sensor working mode according to the command is realized.
4. The integral efficiency of the system is improved by expanding the meaning of the number of data of the reading command of the ISO/IEC 18000-6Type C standard, the anti-collision function of multiple labels is realized, and the measurement precision of the reader-writer can be improved to a certain extent (the longer the duration of the label returning square wave is, the higher the frequency precision of the return signal measured by the reader-writer is).
Claims (8)
1. A passive wireless magnetic field property sensing tag, comprising: an antenna, an impedance matching network circuit and power divider circuit, a rectification and quantity management circuit, an LDO, a demodulation circuit, a processor, a magnetic field characteristic sensing circuit, a selection switch circuit and a back scattering circuit, wherein,
the magnetic field characteristic sensing circuit is used for sensing the magnetic field quantity of the position where the label is located;
the antenna, the impedance matching network circuit and the power divider circuit are used for receiving and distributing radio frequency signals and radio frequency energy sent by the reader-writer;
the rectification and energy management circuit is used for converting radio frequency energy into direct current electric energy available for the label, storing the direct current electric energy and intermittently supplying the direct current electric energy to the label for working and using;
the LDO group provides direct current voltage for each circuit module of the tag;
the demodulation circuit is used for demodulating a command signal sent by the reader-writer and converting the command signal into a baseband signal;
the processor is used for analyzing the reader-writer command and controlling the label to work according to the reader-writer command;
the selection switch circuit is a one-out-of-three channel selection switch and is connected with a signal channel required by a reader-writer command under the control of the processor;
the backscattering circuit sends a signal to the reader-writer in a backscattering mode under the control of the modulation signal;
the magnetic field characteristic sensing circuit is a single-sensor acquisition mode and double-sensor acquisition mode coexistence type sensing circuit, and comprises: a double-sensor acquisition mode switch, a sensor No. 1 exciting circuit, a sensor No. 2 exciting circuit, an exclusive OR gate circuit, a low-pass filter, an inverter and a buffer which are connected in sequence, wherein, the No. 1 sensor and the No. 1 sensor exciting circuit operate independently in a single sensor acquisition mode, the signal port of the single sensor acquisition mode outputs a 37KHz-39KHz square wave signal, the switch of the double sensor acquisition mode is conducted under the double sensor acquisition mode, the sensor No. 1 exciting circuit, the sensor No. 2 exciting circuit, the XOR gate circuit, the low-pass filter, the inverter and the buffer are operated after the switch of the double sensor acquisition mode is conducted, and outputting 300Hz-500Hz square wave signals through a dual-sensor acquisition mode output signal port.
2. A passive wireless magnetic field property sensing tag according to claim 1, wherein the processor is in particular a single chip.
3. A passive wireless magnetic field property sensing tag according to claim 1, wherein the sensor is a resonant type magnetic field quantity sensor, which is formed by combining a magnetostrictive material and a high-Q quartz crystal resonator.
4. A passive wireless magnetic field characteristic sensing system based on the passive wireless magnetic field characteristic sensing tag of any one of claims 1 to 3, comprising a plurality of passive wireless magnetic field characteristic sensing tags arranged in a magnetic field environment to be measured, a reader for reading and writing the tags, and an upper computer for controlling the reader.
5. A passive wireless magnetic field characteristic sensing system according to claim 4, characterized in that, in operation, the reader first inventories tags existing around the reader and records all the tags inventoried, and then selects tags to realize general functions or magnetic field quantity sensing.
6. The passive wireless magnetic field characteristic sensing system according to claim 5, wherein when the reader/writer reads the user storage area and the read address is 0x10, it indicates that the single sensor is used for magnetic field quantity sensing; when the user storage area is read and the read address is 0x12, it indicates that the dual sensor is used for magnetic field amount sensing.
7. The passive wireless magnetic field sensing system of claim 6, wherein the reader uses the number of read data in the read command to indicate the duration of the return square wave of the tag.
8. The passive wireless magnetic field sensing system according to claim 7, wherein the last 7 bits are used to represent the square wave duration when the highest bit of the read data is 1.
Priority Applications (3)
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