Ultra-low power consumption passive communication system based on backscattering

Abstract

The invention discloses an ultra-low power consumption passive communication system based on backscattering, relates to a communication technology, and provides a scheme for solving the problem that a passive communication network is difficult to form in the prior art. The comprehensive transmitter is used for providing radio frequency energy and radio frequency signals for the passive receiving subsystem, sending wake-up signals to the passive receiving subsystem according to application requirements, and collecting and processing backscattering data of the passive receiving subsystem; the passive receiving subsystem receives radio frequency energy and radio frequency signals; adaptive power processing is carried out on the radio frequency energy, and data processing is carried out on the radio frequency signal; if no task is processed currently, entering a low-power-consumption mode, and waiting for a wake-up signal; and when the wake-up signal is received, the system enters a working mode, and the radio frequency signal is backscattered. The method has the advantages that the problem that the passive receiving subsystem cannot demodulate information in a low-power-consumption mode is solved, so that the passive receiving subsystem can respond to the requirements of the comprehensive transmitter in real time in the low-power-consumption mode.

Description

Technical Field

[0001] The invention relates to communication technology, and in particular to an ultra-low power consumption passive communication system based on backscattering. Background Art

[0002] With the advent of the era of the Internet of Everything, the number of IoT devices has seen a spurt of growth; in the next few years, the number of IoT devices may reach hundreds of billions, but most devices cannot be powered by wires and can only be powered by batteries. Although with the development of semiconductor technology, the power consumption of many IoT devices has been significantly reduced, and the operating time of devices can reach 1 to 3 years when powered by batteries, the labor cost of replacing batteries for a huge number of IoT devices is unacceptable. Therefore, both the industry and academia hope to build a passive IoT. The passive IoT hopes to capture external energy (such as solar energy, wind energy, radio frequency energy, etc.) for its own use without the need for external batteries. Compared with the active IoT, the passive IoT saves the cost of the battery itself and the cost of battery replacement, and is also conducive to building an energy-saving and environmentally friendly society, because the production of batteries uses a large amount of metals and chemicals.

[0003] In view of the above situation, backscatter technology and signal-to-signal simultaneous transmission technology have huge application potential in passive Internet of Things scenarios.

[0004] Backscatter technology is an ultra-low power modulation and transmission technology designed based on the principle of backscattering of RF signals. When the RF signal reaches the antenna, if the antenna impedance matches the load impedance, the RF signal is absorbed. On the contrary, if the antenna impedance and the load impedance are mismatched, the RF signal is reflected. The passive receiving subsystem can adjust the load impedance and modulate its own stored data onto the reflected signal in an ultra-low power manner without the need for RF local oscillators, power amplifiers, high-precision crystal oscillators, high-precision filters and other devices, and without complex baseband processing. The integrated transmitter can process the reflected signal and demodulate the information fed back by the passive receiving subsystem. On the other hand, by utilizing the energy characteristics of the RF signal itself, when the RF signal is received by the antenna, in addition to the energy required for information demodulation, the RF signal energy is stored as much as possible through energy harvesting technology to provide energy for the passive receiving subsystem in the future.

[0005] At present, the technologies that use backscatter include radio frequency identification technology RFID and signal-to-single simultaneous interpretation technology. Among them, RFID passive tags are already very mature, but RFID passive tags can only return fixed data that they have stored, such as their own ID information, and cannot return real-time data obtained from the outside world, nor can they effectively control external devices. Therefore, most of the time, they can only be used for identity recognition, and cannot be used as an IoT device to handle other services. Signal-to-single simultaneous interpretation technology cannot effectively feedback signals to the outside world in a low-power manner. However, the demand in actual applications is that passive IoT devices need to be able to sense the external environment and send the data they obtain from the outside world to the terminal. With the development of the times, IoT devices also need to be able to interact with other IoT devices. Summary of the invention

[0006] The purpose of the present invention is to provide an ultra-low power consumption passive communication system based on backscattering to solve the problems existing in the above-mentioned prior art.

[0007] The ultra-low power consumption passive communication system based on backscattering described in the present invention comprises a passive receiving subsystem and an integrated transmitter connected in communication;

[0008] The integrated transmitter is used to provide radio frequency energy and radio frequency signals to the passive receiving subsystem, send a wake-up signal to the passive receiving subsystem according to application requirements, and collect and process backscattered data of the passive receiving subsystem;

[0009] The passive receiving subsystem receives the RF energy and RF signal; performs adaptive power processing on the RF energy and data processing on the RF signal; if there is no task processing at present, enters a low power consumption mode and waits for a wake-up signal; when a wake-up signal is received, enters a working mode and backscatters the RF signal.

[0010] The passive receiving subsystem includes a source coding module, a backscattering control circuit, a radio frequency front-end control circuit, a wake-up circuit, a sensor, a baseband signal processing module, a low-pass filter circuit, a rectifier circuit, a band-pass filter circuit, a power distribution circuit, an energy management circuit, a PID control unit, an energy storage element and an antenna;

[0011] The RF front-end control circuit acts as a RF feed line impedance. When the RF feed line impedance matches the antenna impedance, the antenna absorbs the RF signal, otherwise the antenna reflects the RF signal.

[0012] The energy management circuit and the energy storage element constitute a power supply system of the passive receiving subsystem, which is used to collect and store the radio frequency energy received by the antenna and to supply power to the passive receiving subsystem;

[0013] The power distribution circuit, baseband signal processing module, and PID control unit form an adaptive closed-loop control network of the passive receiving subsystem, and control the energy proportion of the power distribution circuit flowing into the power supply system and the bandpass filter circuit respectively;

[0014] The band-pass filter circuit, the rectifier circuit and the low-pass filter circuit are electrically connected in sequence to output a baseband signal;

[0015] The wake-up circuit uses a hardware circuit to identify the wake-up instruction sent by the integrated transmitter in the low power consumption mode, so that the passive receiving subsystem enters the working mode from the low power consumption mode;

[0016] The baseband signal processing module is used to demodulate the baseband signal output by the low-pass filter circuit, interact with external devices, and put the passive receiving subsystem into a low-power consumption mode when there is no task processing;

[0017] The baseband signal processing module, source coding module, backscatter control circuit and RF front-end control circuit constitute a feedback signal transmitter of a passive receiving subsystem, which is used to perform source coding on the sensor data, and then control the RF feed line impedance of the RF front-end control circuit through the backscatter control circuit, so that the antenna switches between absorbing RF signals and reflecting RF signals, thereby sending out bit 0 and bit 1 of the encoded data so that they can be collected and processed by the integrated transmitter.

[0018] The RF front-end control circuit includes an RF switch and two pure resistance impedances. The incident RF signal will produce different reflection amounts according to the impedance matching degree of the antenna port; the reflection coefficient z0 is the characteristic impedance of the antenna end, 50Ω, z L is the RF feed line impedance; when Γ=0, the impedance is matched and the incident signal is completely absorbed; when Γ=-1, the impedance is mismatched and the incident signal is completely reflected; the two pure resistance impedances are 50Ω and 0Ω respectively, and one of them is selected by controlling the RF switch.

[0019] In the feedback signal transmitter, the baseband signal processing module obtains the data of the sensor, and then adds the original data to the frame header and frame length to encapsulate it into a frame; then the frame is sent to the source coding module for source coding and redundant bits are added; the backscattering control circuit controls the switching frequency of the RF switch in the RF front-end control circuit according to each bit of the data output by the source coding module; when the data bit is bit 0, the switching frequency of the RF switch is f1; when the data bit is bit 1, the switching frequency of the RF switch is f2; by changing the frequency of the RF switch, the passive receiving subsystem modulates the frequency shift keying signal to send information to the integrated transmitter.

[0020] The power distribution circuit includes two programmable resistors, which are connected in parallel to divide the radio frequency power received by the antenna into two parts, one part flows to the power supply system, and the other part flows to the bandpass filter circuit.

[0021] In the adaptive closed-loop control network, the baseband signal processing module converts the analog baseband signal received from the low-pass filter circuit into a digital baseband signal, and then periodically converts the current average power value P of the digital baseband signal into a digital baseband signal. m [n] and the minimum target power value P of the demodulated baseband signal t The signal is sent to the PID control unit; the PID control unit outputs a control signal u[n] through a PID closed-loop control algorithm; the control signal u[n] controls the resistance of two programmable resistors in the power distribution circuit, and collects and stores all the remaining RF energy while being able to demodulate the baseband signal.

[0022] The steps of the PID control algorithm are:

[0023] S1. The baseband signal processing module obtains the current average power value P in real time m [n] as the input of the PID control unit;

[0024] S2.PID control unit according to the target power P t And the average power value P m [n] calculates the error e[n], e[n] = P t -P m [n];

[0025] S3. The PID control unit calculates the output control signal u[n] based on the error e[n], Where K p is the proportionality coefficient, K i is the integral coefficient, K d is the differential coefficient, n represents the current moment, and n-1 represents the previous moment;

[0026] S4. The power distribution circuit adjusts the resistance values ​​of the two programmable resistors according to the control signal u[n] calculated by the PID control unit to achieve the desired power output;

[0027] S5. Execute the loop and return to step S1.

[0028] The energy management circuit includes a boost circuit, a detection circuit, and a voltage stabilization circuit;

[0029] The boost circuit boosts the changing weak signal into a stable DC output signal;

[0030] The energy storage element stores the stable DC output signal;

[0031] The detection circuit detects the working state of the energy storage element in real time. When the working state of the energy storage element is normal, the voltage stabilizing circuit outputs the voltage of the energy storage element in a regulated manner to supply power to the passive receiving subsystem.

[0032] The wake-up circuit includes a voltage amplifier circuit, a single-channel Schmitt trigger and a counter which are electrically connected in sequence;

[0033] The voltage amplifying circuit performs voltage amplification on the baseband signal outputted from the low-pass filtering circuit to the wake-up circuit;

[0034] The single-channel Schmitt trigger converts the amplified baseband signal into a square wave signal, and the square wave signal is used as the clock signal of the counter. Whenever a falling edge appears in the square wave signal, the counter counts one more time. When the count reaches a threshold, the counter outputs a wake-up signal to the baseband signal processing module. After receiving the wake-up signal, the baseband signal processing module switches the passive receiving subsystem from the low power consumption mode to the working mode.

[0035] The communication process of the integrated transmitter and passive receiving subsystem is as follows:

[0036] S1. The integrated transmitter sends a wake-up command to wake up the passive receiving subsystem in low power mode and put it into working mode;

[0037] S2. The passive receiving subsystem entering the working mode responds to the request of the integrated transmitter in real time and uses its own feedback signal transmitter to make a real-time response to the integrated transmitter;

[0038] S3. When the passive receiving subsystem has no task to process, the passive receiving subsystem sends a sleep request instruction to the integrated transmitter;

[0039] S4. After the integrated transmitter receives the sleep command, if it has tasks that need to be processed by the passive receiving subsystem, it will send a rejection command to the passive receiving subsystem; otherwise, it will send an acceptance command to the passive receiving subsystem;

[0040] S5. If the passive receiving subsystem receives a rejection command, it will continue to wait for the request from the integrated transmitter and respond in time; if it receives an acceptance command, it will shut down all its peripheral functions, retain only the wake-up function and enter a low power consumption mode.

[0041] The ultra-low power consumption passive communication system based on backscattering described in the present invention has the following advantages:

[0042] 1) The passive receiving subsystem can switch freely between low power mode and working mode, and can respond to the wake-up command sent by the integrated transmitter in real time in low power mode. This solves the problem of excessive power consumption of the passive receiving subsystem in standby mode, further reduces the overall power consumption of the passive receiving subsystem, and the overall average power consumption of the system is at the microwatt level.

[0043] 2) The passive receiving subsystem can cleverly utilize the characteristics of the wake-up circuit in low-power mode, and decode the wake-up instruction at microwatt level power consumption by using the cooperation between hardware without complex demodulation algorithms. This solves the problem that the passive receiving subsystem cannot demodulate information in low-power mode, so that the passive receiving subsystem can respond to the needs of the integrated transmitter in real time even in low-power mode.

[0044] 3) The passive receiving subsystem can use the radio frequency energy obtained from the outside world to send the data obtained from the outside world in real time through backscattering technology in a passive state, and can also interact with external devices for communication or control. This solves the dilemma that the existing RFID technology can only send its own ID, and provides more possibilities for application in other scenarios.

[0045] 4) The adaptive closed-loop control network of the passive receiving subsystem can adaptively distribute the radio frequency signal with both information and energy received by the passive receiving subsystem from the antenna according to demand. Compared with open-loop control, under the control of the closed-loop control system, the utilization rate of radio frequency energy and the stability of the system in complex environments are improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 It is a structural schematic diagram of the ultra-low power consumption passive communication system.

[0047] Figure 2 Schematic diagram of the output signal waveform of the RF front-end control circuit.

[0048] Figure 3 Schematic diagram of the output signal waveform of the bandpass filter circuit.

[0049] Figure 4 Schematic diagram of the output signal waveform of the rectifier circuit.

[0050] Figure 5 Schematic diagram of the output signal waveform of the low-pass filtering circuit.

[0051] Figure 6 Schematic diagram of the output signal waveform of the backscatter control circuit.

[0052] Figure 7 is a schematic diagram of the output signal spectrum of the backscatter control circuit.

[0053] Figure 8 Schematic diagram of the circuit principle of the radio frequency front-end control circuit.

[0054] Fig. 9 Schematic diagram of the circuit principle of the power distribution circuit.

[0055] Fig.10 Schematic diagram of the circuit principle of the energy management circuit.

[0056] Fig.11 Schematic diagram of the circuit principle of the wake-up circuit.

[0057] Fig.12 It is a communication flow diagram of the ultra-low power consumption passive communication system.

[0058] Reference numerals:

[0059] Passive receiving subsystem 100: source coding module 101, backscattering control circuit 102, RF front-end control circuit 103, wake-up circuit 104, sensor 105, baseband signal processing module 106, low-pass filter circuit 107, rectifier circuit 108, band-pass filter circuit 109, power distribution circuit 110, energy management circuit 111, PID control unit 112, energy storage element 113, antenna 114;

[0060] Integrated transmitter 200. DETAILED DESCRIPTION

[0061] like Figure 1 As shown, the ultra-low power consumption passive communication system based on backscattering described in the present invention includes an integrated transmitter 200 and a passive receiving subsystem 100; wherein the passive receiving subsystem 100 includes a source coding module 101, a backscattering control circuit 102, a radio frequency front-end control circuit 103, a wake-up circuit 104, a sensor 105, a baseband signal processing module 106, a low-pass filter circuit 107, a rectifier circuit 108, a band-pass filter circuit 109, a power distribution circuit 110, an energy management circuit 111, a PID control unit 112, an energy storage element 113 and an antenna 114.

[0062] The integrated transmitter 200 sends an FSK RF signal with both energy and information to the passive receiving subsystem 100, which is transmitted to the passive receiving subsystem 100 through free space. The passive receiving subsystem 100 controls the antenna 114 to absorb or reflect the RF signal through the impedance matching network of the RF front-end control circuit 103.

[0063] The energy management circuit 111 and the energy storage element 113 constitute a power supply system.

[0064] After the RF signal is absorbed, the power distribution circuit 110 divides the RF signal into two parts according to the power distribution ratio, one part flows into the power supply system, and the other part flows into the bandpass filter circuit 109. The power supply system collects and stores the energy of the incoming RF signal, and provides an energy source for the passive receiving subsystem 100 when needed. The wake-up circuit 104 identifies whether the incoming baseband analog signal contains a wake-up instruction, and decides whether to wake up the passive receiving subsystem 100. The baseband signal processing module 106 processes the incoming baseband analog signal, including information demodulation and sending the power average value of the baseband analog signal to the PID control unit 112. The PID control unit 112 uses the power average value as the input of the PID closed-loop control algorithm, and uses the output of the PID closed-loop control algorithm to control the power distribution ratio of the power distribution circuit 110 to ensure that the energy of the RF signal is stored as much as possible under the premise of being able to demodulate the baseband analog signal. The baseband signal processing module 106 performs baseband processing on the data acquired from the sensor 105 , and then performs source coding to improve the anti-interference capability of the data, and then uses the backscatter control circuit 102 to modulate the data onto the reflected radio frequency signal.

[0065] The RF front-end control circuit 103 serves as the RF feed line impedance and forms an impedance matching unit with the antenna 114. When the RF feed line impedance matches the antenna 114 impedance, the antenna 114 absorbs the RF signal reaching the antenna 114. On the contrary, when the RF feed line impedance and the antenna 114 impedance are mismatched, the antenna 114 reflects the RF signal reaching the antenna 114. In this embodiment, the core IC of the RF front-end control circuit 103 can be an ADG902 RF isolation IC, such as Figure 8 As shown. CTRL is a digital control pin. When CTRL is high, RF1 is internally connected to RF2. When CTRL is low, RF1 is internally isolated from PF2. RF1 is directly connected to antenna 114 and antenna 114 is also connected to rectifier circuit 108. RF2 is grounded. When CTRL is high, it is equivalent to the RF feeder impedance being 0, the antenna 114 impedance and the feeder impedance are mismatched, and the antenna 114 reflects the arriving RF signal. When CTRL is low, RF1 is isolated from RF2, and the RF feeder impedance reflects the impedance of the rectifier circuit 108, and the impedance of the rectifier circuit 108 is designed to be 50Ω, so at this time the antenna 114 impedance and the RF feeder impedance match, the antenna 114 absorbs the arriving RF signal, and the RF signal is sent to the rectifier circuit 108.

[0066] The power distribution circuit 110 can distribute the radio frequency signal into two parts according to a specific power distribution ratio, one part flows into the power supply system as energy storage, and the other part flows into the bandpass filter circuit 109 as information demodulation. In this embodiment, the power distribution circuit 110 can use MCP4017T-104 as the preferred IC of the programmable resistor, such as Fig. 9 As shown. The power distribution circuit 110 is composed of two programmable resistors, and the resistance range of a single programmable resistor is 0 to 100KΩ. Specifically, the two ends of the resistor are port B and port W, so the connection resistance of each MCP4017T-104 in the circuit is R BW . R BW The resistance value can be controlled by the SCL and SDA ports, that is, the microprocessor can control R through the IIC protocol BW The resistance value of Figure 4 The resistance values ​​from top to bottom are R1 and R2, and the powers are P1 and P2, then P1: Therefore, the power distribution ratio of the power distribution circuit 110 can be controlled by the microprocessor to allow energy to flow into the energy management module as much as possible, thereby improving the energy collection efficiency.

[0067] The energy management circuit 111 can boost and collect the analog signal, and store the energy through the energy storage element 113. The energy management circuit 111 can also manage charging and discharging according to the state of the energy storage element 113. Fig.10As shown, in this embodiment, the core IC of the energy management circuit 111 can be selected from BQ25570, and the energy storage element 113 can be selected from supercapacitors. The baseband signal is connected to the VIN pin of the energy management circuit 111. The VIN pin has a BOOST boost circuit inside, which can boost the input baseband signal to meet the charging voltage of the energy storage element 113. The energy storage element 113 is connected to the VBAT pin. In this embodiment, the energy storage element 113 is a supercapacitor. The VBAT_OV pin is used to set overcharge protection. When the voltage of the energy storage element 113 is lower than the overcharge voltage value, the energy storage element 113 continues to store energy. When the voltage of the energy storage element 113 reaches the overcharge voltage value, the energy storage element 113 stops storing energy to prevent the energy storage element 113 from being damaged due to overcharging. OK_HYST and OK_PROG are used to set the working voltage range of the energy storage element 113. When the voltage of the energy storage element 113 is higher than OK_HYST, the VBAT_OK pin outputs a high level, indicating that the energy storage element 113 is working normally. When the voltage of the energy storage element 113 is lower than OK_PROG, the VBAT_OK pin outputs a low level, indicating that the energy storage element 113 is not working properly. VOUT is a programmable voltage-regulated output port, which can output the energy stored in the energy storage element 113 in a regulated voltage. The VOUT_SET pin is used to set the output voltage value of VOUT. The enable pin of the programmable voltage-regulated output of VOUT_EN is valid at a high level. In this embodiment, VOUT_EN and VBAT_OK are interconnected, that is, only when the energy storage element 113 is working properly, the energy of the energy storage element 113 is output in a regulated voltage and supplied to the passive receiving subsystem 100. The calculation formulas of VBAT_OV, OK_HYST, OK_PROG and VOUT are:

[0068]

[0069]

[0070]

[0071]

[0072] The typical value of VRDIV is 1.21 V. Therefore, the energy of the baseband analog signal can be stored through the energy management circuit 111, and the energy management circuit 111 can also automatically manage the charge and discharge of the energy storage element 113 according to OK_HYST and OK_PROG, and the energy management circuit 111 also improves the overcharge protection to prevent the energy storage element 113 from being damaged due to overcharge.

[0073] The wake-up circuit 104 can identify whether the baseband analog signal contains a wake-up instruction. When the baseband analog signal flowing into the wake-up circuit 104 contains a wake-up instruction, the wake-up circuit 104 wakes up the passive receiving subsystem 100 from the low power consumption mode to the working mode. Fig.11 As shown, in this embodiment, the operational amplifier of the wake-up circuit 104 can select TLV9041 as the preferred IC, the single-channel Schmitt trigger can select SN74AUP1T50 as the preferred IC, and the counter can select SN74LV393 as the preferred IC. The baseband analog signal is connected to the non-inverting input terminal of the operational amplifier for proportional amplification. In this embodiment, the amplification ratio is 23. Then, through the input terminal of the single-channel Schmitt trigger, the single-channel Schmitt trigger converts the input signal into a standard square wave signal output. The clock input signal of the counter is connected to the output signal of the single-channel Schmitt trigger. Whenever the square wave signal has a falling edge, the counter counts one more. When the count reaches 256, the 2QD pin outputs a high-level wake-up signal, allowing the passive receiving subsystem 100 to enter the working mode from the low-power mode.

[0074] In this embodiment, a microprocessor is selected to implement all functions of the backscatter control circuit 102, the source coding module 101, the baseband signal processing module 106 and the PID control unit 112. The microprocessor uses its own computing power to complete the demodulation of the analog baseband signal and the calculation of the PID closed-loop control algorithm. At the same time, the external data obtained from the sensor 105 is subjected to baseband signal processing and source coding, and then the output port of the microprocessor is used to control the RF front-end control circuit 103 to modulate the data onto the reflected signal. The microprocessor can select STM32 or MSP430 as the preferred MCU of this embodiment.

[0075] The communication process of the integrated transmitter 200 and the passive receiving subsystem 100 is as follows: Fig.12As shown, in order to reduce power consumption as much as possible, the passive receiving subsystem 100 is in low power consumption mode before receiving the wake-up command sent by the integrated transmitter 200, and the power consumed is at the microwatt level. After receiving the wake-up command sent by the integrated transmitter 200, it enters the working mode. In the working mode, the passive receiving subsystem 100 can process various task requirements sent by the integrated transmitter 200, and can send the sensor 105 data or task feedback signal obtained from the outside to the integrated transmitter 200 through its own feedback signal transmitter. When there is no task requirement, the passive receiving subsystem 100 sends a sleep command to the integrated transmitter 200, requesting to enter the low power consumption mode. After the integrated transmitter 200 receives the sleep command, if it has no task that needs to be processed by the passive receiving subsystem 100, it sends an acceptance command to the passive receiving subsystem 100. After receiving the acceptance command, the passive receiving subsystem 100 turns off all peripheral functions and enters the low power consumption mode. On the contrary, if the integrated transmitter 200 has tasks that need to be processed by the passive receiving subsystem 100, a rejection instruction is sent to the passive receiving subsystem 100, and the passive receiving subsystem 100 continues to operate in the working mode. It is ensured that the passive receiving subsystem 100 can process the request sent by the integrated transmitter 200 in real time while ensuring its own low power consumption, and the passive receiving subsystem 100 will not enter the low power consumption mode without authorization under the premise that the integrated transmitter 200 has task requirements, resulting in the request of the integrated transmitter 200 not being processed in time.

[0076] For those skilled in the art, various other corresponding changes and deformations can be made according to the technical solutions and concepts described above, and all of these changes and deformations should fall within the protection scope of the claims of the present invention.

Claims

1. An ultra-low power passive communication system based on backscattering, characterized in that: A passive receiving subsystem (100) and an integrated transmitter (200) are included in a communication connection; The integrated transmitter (200) is used to provide radio frequency energy and radio frequency signals to the passive receiving subsystem (100), send a wake-up signal to the passive receiving subsystem (100) according to application requirements, and collect and process backscattered data of the passive receiving subsystem (100); The passive receiving subsystem (100) receives the radio frequency energy and the radio frequency signal; performs adaptive power processing on the radio frequency energy and performs data processing on the radio frequency signal; if there is no task to be processed at present, enters a low power consumption mode and waits for a wake-up signal; and enters a working mode when a wake-up signal is received and performs backscattering of the radio frequency signal.

2. The ultra-low power consumption passive communication system based on backscattering according to claim 1, characterized in that: The passive receiving subsystem (100) comprises a source coding module (101), a backscattering control circuit (102), a radio frequency front-end control circuit (103), a wake-up circuit (104), a sensor (105), a baseband signal processing module (106), a low-pass filter circuit (107), a rectifier circuit (108), a band-pass filter circuit (109), a power distribution circuit (110), an energy management circuit (111), a PID control unit (112), an energy storage element (113) and an antenna (114); The RF front-end control circuit (103) serves as a RF feed line impedance. When the RF feed line impedance matches the antenna (114) impedance, the antenna (114) absorbs the RF signal. Otherwise, the antenna (114) reflects the RF signal. The energy management circuit (111) and the energy storage element (113) constitute a power supply system of the passive receiving subsystem (100), which is used to collect and store radio frequency energy received by the antenna (114) and to supply power to the passive receiving subsystem (100); The power distribution circuit (110), the baseband signal processing module (106), and the PID control unit (112) form an adaptive closed-loop control network of the passive receiving subsystem (100), and control the energy ratio of the power distribution circuit (110) flowing into the power supply system and the bandpass filter circuit (109) respectively; The bandpass filter circuit (109), the rectifier circuit (108) and the low-pass filter circuit (107) are electrically connected in sequence to output a baseband signal; The wake-up circuit (104) uses a hardware circuit to identify the wake-up instruction sent by the integrated transmitter (200) in the low power consumption mode, so as to enable the passive receiving subsystem (100) to enter the working mode from the low power consumption mode; The baseband signal processing module (106) is used to demodulate the baseband signal output by the low-pass filter circuit (107), interact with external devices, and allow the passive receiving subsystem (100) to enter a low power consumption mode when there is no task to be processed; The baseband signal processing module (106), the source coding module (101), the backscattering control circuit (102) and the radio frequency front-end control circuit (103) constitute a feedback signal transmitter of the passive receiving subsystem (100), which is used to perform source coding on the data of the sensor (105), and then control the radio frequency feed line impedance of the radio frequency front-end control circuit (103) through the backscattering control circuit (102), so that the antenna (114) switches between absorbing radio frequency signals and reflecting radio frequency signals, thereby sending out bit 0 and bit 1 of the encoded data, so that they can be collected and processed by the integrated transmitter (200).

3. The ultra-low power consumption passive communication system based on backscattering according to claim 2, characterized in that: The radio frequency front-end control circuit (103) comprises a radio frequency switch and two pure resistance impedances. The incident radio frequency signal will generate different reflection amounts according to the impedance matching degree of the antenna (114) port; the reflection coefficient z0 is the characteristic impedance of the antenna (114) end, 50Ω, z L is the RF feed line impedance; When Γ=0, the impedance is matched and the incident signal is completely absorbed; when Γ=-1, the impedance is mismatched and the incident signal is completely reflected; the two pure resistance impedances are 50Ω and 0Ω respectively, and one of them is selected by controlling the RF switch.

4. The ultra-low power consumption passive communication system based on backscattering according to claim 3, characterized in that: In the feedback signal transmitter, a baseband signal processing module (106) acquires data from a sensor (105), then adds a frame header and a frame length to the original data and encapsulates the data into a frame; the frame is then sent to a source coding module (101) for source coding and adding redundant bits; a backscattering control circuit (102) controls the switching frequency of a radio frequency switch in a radio frequency front-end control circuit (103) according to each bit of data output by the source coding module (101); when the data bit is bit 0, the switching frequency of the radio frequency switch is f1; when the data bit is bit 1, the switching frequency of the radio frequency switch is f2; by changing the frequency of the radio frequency switch, a passive receiving subsystem (100) modulates a frequency shift keying signal and sends information to an integrated transmitter (200).

5. The ultra-low power consumption passive communication system based on backscattering according to claim 2, characterized in that: The power distribution circuit (110) comprises two programmable resistors, and the radio frequency power received by the antenna (114) is divided into two parts by connecting the two programmable resistors in parallel, one part flows to the power supply system, and the other part flows to the bandpass filter circuit (109).

6. The ultra-low power consumption passive communication system based on backscattering according to claim 5, characterized in that: In the adaptive closed-loop control network, the baseband signal processing module (106) converts the analog baseband signal received from the low-pass filter circuit (107) into a digital baseband signal, and then periodically calculates the current average power value P of the digital baseband signal. m [n] and the minimum target power value P of the demodulated baseband signal t The PID control unit (112) outputs a control signal u[n] through a PID closed-loop control algorithm. The control signal u[n] controls the resistance values ​​of two programmable resistors in the power distribution circuit (110), thereby collecting and storing all the remaining radio frequency energy under the premise of being able to demodulate the baseband signal.

7. The ultra-low power consumption passive communication system based on backscattering according to claim 6, characterized in that: The steps of the PID control algorithm are: S1. The baseband signal processing module (106) obtains the current average power value P in real time m [n] as input to the PID control unit (112); S2.PID control unit (112) according to the target power P t And the average power value P m [n] calculates the error e[n], e[n] = P t -P m [n]; S3. The PID control unit (112) calculates the output control signal u[n] according to the error e[n], Where K p is the proportionality coefficient, K i is the integral coefficient, K d is the differential coefficient, n represents the current moment, and n-1 represents the previous moment; S4. The power distribution circuit (110) adjusts the resistance values ​​of the two programmable resistors according to the control signal u[n] calculated by the PID control unit (112) to achieve the desired power output; S5. Execute the loop and return to step S1.

8. The ultra-low power consumption passive communication system based on backscattering according to claim 2, characterized in that: The energy management circuit (111) comprises a voltage boost circuit, a detection circuit and a voltage stabilization circuit; The boost circuit boosts the changing weak signal into a stable DC output signal; The energy storage element (113) stores the stable DC output signal; The detection circuit detects the working state of the energy storage element (113) in real time. When the working state of the energy storage element (113) is normal, the voltage stabilization circuit outputs the voltage of the energy storage element (113) in a regulated manner to supply power to the passive receiving subsystem (100).

9. The ultra-low power consumption passive communication system based on backscattering according to claim 2, characterized in that: The wake-up circuit (104) comprises a voltage amplifier circuit, a single-channel Schmitt trigger and a counter which are electrically connected in sequence; The voltage amplifying circuit performs voltage amplification on the baseband signal outputted by the low-pass filtering circuit (107) to the wake-up circuit (104); The single-channel Schmitt trigger converts the amplified baseband signal into a square wave signal, and the square wave signal is used as a clock signal of the counter. Whenever a falling edge appears in the square wave signal, the counter counts one more time. When the count reaches a threshold, the counter outputs a wake-up signal to the baseband signal processing module (106). After receiving the wake-up signal, the baseband signal processing module (106) causes the passive receiving subsystem (100) to switch from a low power consumption mode to an operating mode.

10. An ultra-low power consumption passive communication system based on backscattering according to any one of claims 2 to 9, characterized in that: The communication process between the integrated transmitter (200) and the passive receiving subsystem (100) is as follows: S1. The integrated transmitter (200) sends a wake-up command to wake up the passive receiving subsystem (100) in the low power mode and enter the working mode; S2. The passive receiving subsystem (100) entering the working mode responds to the request of the integrated transmitter (200) in real time and uses its own feedback signal transmitter to make a real-time response to the integrated transmitter (200); S3. When the passive receiving subsystem (100) has no task to process, the passive receiving subsystem (100) issues a sleep request instruction to the integrated transmitter (200); S4. After the integrated transmitter (200) receives the sleep command, if it has tasks that need to be processed by the passive receiving subsystem (100), it will send a rejection command to the passive receiving subsystem (100); otherwise, it will send an acceptance command to the passive receiving subsystem (100); S5. If the passive receiving subsystem (100) receives a rejection instruction, it will continue to wait for the request of the integrated transmitter (200) and respond in time; if it receives an acceptance instruction, it will shut down all its peripheral functions, retain only the wake-up function and enter a low power consumption mode.

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