An ultra-low power passive communication system based on backscattering

Abstract

The application discloses a kind of ultra-low power passive communication systems based on backscattering, it is related to communication technology, the present technical problems that passive communication network is difficult to constitute are proposed in this scheme.Integrated transmitter is used to provide radio frequency energy and radio frequency signal to passive receiving subsystem, according to application needs to send wake-up signal to passive receiving subsystem, and collect and process the backscattering data of passive receiving subsystem;Passive receiving subsystem receives radio frequency energy and radio frequency signal;Radio frequency energy is adaptively powered, and data processing is carried out on radio frequency signal;If there is no task processing currently, enter low-power mode, and wait for wake-up signal;When receiving wake-up signal, enter working mode, and make radio frequency signal backscattering.The advantage is that the problem that passive receiving subsystem cannot demodulate information in low-power mode is solved, so that passive receiving subsystem can also respond to the demand of integrated transmitter in low-power mode in real time.

Description

TECHNICAL FIELD

[0001] The present application relates to the communication technology, specifically relates to a kind of ultra-low power passive communication system based on backscattering. BACKGROUND

[0002] With the advent of the Internet of Things era, the number of Internet of Things devices has experienced explosive growth; In the next few years, the number of Internet of Things devices can reach hundreds of billions, but most devices cannot be powered by wire, but only by battery. Although with the development of semiconductor technology, the power consumption of many Internet of Things devices has been significantly reduced, and the running time of the device can be 1-3 years using battery power, but the human cost of replacing the batteries of a large number of Internet of Things devices is unacceptable, so the industry and academia hope to build a passive Internet of Things. Passive Internet of Things hopes to use its own captured external energy (such as solar energy, wind energy, radio frequency energy, etc.) for its own use without external battery. Compared with active Internet of Things, passive Internet of Things saves the cost of 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 metal and chemicals.

[0003] In view of the above situation, backscattering technology and signal-energy co-transmission technology have great application potential in passive Internet of Things scenarios.

[0004] Backscattering technology is a kind of ultra-low power modulation and transmission technology designed by using the principle of radio frequency signal backscattering. When the radio frequency signal reaches the antenna, if the antenna impedance and load impedance match, the radio frequency signal is absorbed. On the contrary, if the antenna impedance and load impedance are mismatched, the radio frequency signal is reflected. The passive receiving subsystem can modulate the data stored in itself to the reflected signal in an ultra-low power consumption manner by adjusting the load impedance without the need for radio frequency local oscillator, power amplifier, high-precision crystal oscillator and high-precision filter, etc. and without the need for complex baseband processing. The comprehensive transmitter can process the reflected signal and demodulate the information fed back by the passive receiving subsystem. On the other hand, the radio frequency signal itself has energy characteristics, and when the radio frequency signal is received by the antenna, in addition to the energy needed for information demodulation, the radio frequency signal energy is stored as much as possible through energy harvesting technology to provide energy for the passive receiving subsystem subsequently.

[0005] Current technologies utilizing backscatter include radio frequency identification (RFID) and telemetry simultaneous interpretation (TIE) technology. RFID passive tags are already well-established, but they can only return fixed, stored data, such as their ID information, and cannot return real-time data from the outside world, nor effectively control external devices. Therefore, they are mostly limited to identity recognition and cannot function as IoT devices to handle other tasks. TIE technology, on the other hand, cannot effectively and efficiently transmit signals to the outside world in a low-power manner. However, practical applications require that passive IoT devices be able to sense the external environment and transmit data to terminals. As time goes by, there is also a need for IoT devices to interact with other IoT devices. Summary of the Invention

[0006] The present invention aims 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 includes 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 needs, 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 to be processed 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 signal source coding module, a backscatter 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 the 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 power the passive receiving subsystem;

[0013] The power distribution circuit, the baseband signal processing module and the 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 band-pass filter circuit respectively;

[0014] The band-pass filter circuit, the rectifier circuit and the low-pass filter circuit are sequentially electrically connected, and are used for outputting the baseband signal.

[0015] The wake-up circuit identifies the wake-up instruction sent by the integrated transmitter by using a hardware circuit in the low-power mode, so that the passive receiving subsystem enters the working mode from the low-power mode.

[0016] The baseband signal processing module is used for demodulating the baseband signal output by the low-pass filter circuit, interacting with an external device, and entering the low-power mode when there is no task processing.

[0017] The baseband signal processing module, the source coding module, the backscatter control circuit and the radio frequency front-end control circuit form a feedback signal transmitter of the passive receiving subsystem, which is used for source coding the data of the sensor, and then controlling the radio frequency feed line impedance of the radio frequency front-end control circuit by the backscatter control circuit, so that the antenna switches between absorbing the radio frequency signal and reflecting the radio frequency signal, so as to send the coded data bit 0 and bit 1, so as to be collected and processed by the integrated transmitter.

[0018] The radio frequency front-end control circuit includes a radio frequency switch and two pure resistance impedances, and the incident radio frequency 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 port, 50Ω, z L is the radio frequency 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 the radio frequency switch is selected by controlling the switch frequency.

[0019] In the feedback signal transmitter, the baseband signal processing module obtains the data of the sensor, then adds the original data to the frame header and the frame length, and encapsulates the frame; then the frame is sent to the source coding module for source coding and adding redundant bits; the backscatter control circuit controls the switch frequency of the radio frequency switch in the radio frequency 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 switch frequency of the radio frequency switch is f1; when the data bit is bit 1, the switch frequency of the radio frequency switch is f2; by changing the frequency of the radio frequency 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, and the received radio frequency power is divided into two parts by the parallel connection of the two programmable resistors, one part flows to the power supply system, and the other part flows to the band-pass 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 inputs the current average power value P m [n] of the digital baseband signal and the minimum target power value P t of the demodulated baseband signal into the PID control unit; the PID control unit outputs a control signal u[n] through a PID closed-loop control algorithm, and the control signal u[n] controls the resistance values of the two programmable resistors in the power distribution circuit, so as to collect and store all the remaining radio frequency energy under the premise of demodulating the baseband signal.

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

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

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

[0025] S3. The PID control unit calculates the output control signal u[n] according to the error e[n], where K p is the proportional coefficient, K i is the integral coefficient, K d is the differential coefficient, n represents the current time, and n-1 represents the last time;

[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, so as to realize the expected power output;

[0027] S5. The loop is executed, and returns to step S1.

[0028] The energy management circuit includes a boost circuit, a detection circuit, and a voltage stabilizing circuit.

[0029] The boost circuit boosts the varying weak signal into a stable direct current output signal.

[0030] The energy storage element stores the stable direct current output signal.

[0031] The detection circuit detects the working state of the energy storage element in real time, and when the working state of the energy storage element is normal, the voltage of the energy storage element is stabilized and output by the voltage stabilizing circuit to supply power for the passive receiving subsystem.

[0032] The wake-up circuit comprises a voltage amplification circuit, a single-channel Schmitt trigger and a counter connected in sequence.

[0033] The voltage amplification circuit amplifies the baseband signal output by the low-pass filter 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 a clock signal of the counter.

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

[0036] S1. The integrated transmitter sends a wake-up instruction to wake up the passive receiving subsystem in the low-power mode to enter the working mode.

[0037] S2. The passive receiving subsystem in the working mode responds to the request of the integrated transmitter in real time and uses the feedback signal transmitter to make 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 receiving the sleep instruction, if the integrated transmitter has a task to be processed by the passive receiving subsystem, the integrated transmitter sends a rejection instruction to the passive receiving subsystem; otherwise, the integrated transmitter sends an acceptance instruction to the passive receiving subsystem.

[0040] S5. If the passive receiving subsystem receives the rejection instruction, the passive receiving subsystem continues to wait for the request of the integrated transmitter and responds in time; if the passive receiving subsystem receives the acceptance instruction, the passive receiving subsystem closes all external device functions and only keeps the wake-up function and enters the low-power mode.

[0041] The ultra-low-power passive communication system based on the backscattering has the following advantages:

[0042] 1) The passive receiving subsystem can freely switch between low-power mode and working mode, and can respond to wake-up instructions from the integrated transmitter in real time in low-power mode. The problem of high power consumption of the passive receiving subsystem in standby state is solved, further reducing the overall power consumption of the passive receiving subsystem, and the overall average power consumption of the system is in the level of microwatt.

[0043] 2) The passive receiving subsystem can cleverly use the characteristics of the wake-up circuit in low-power mode, without complex demodulation algorithm, using the cooperation between hardware to decode the wake-up instruction with microwatt-level power consumption. The problem that the passive receiving subsystem cannot demodulate information in low-power mode is solved, so that the passive receiving subsystem in low-power mode can also respond to the needs of the integrated transmitter in real time.

[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 backscatter technology, and also can interact with external devices for communication or control. The problem that the existing RFID technology can only send its own ID is solved, providing more possibilities for other scene applications.

[0045] 4) The adaptive closed-loop control network of the passive receiving subsystem can adaptively distribute the radio frequency signals with information and energy received from the antenna according to the 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 environment are improved. BRIEF DESCRIPTION OF DRAWINGS

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

[0047] Figure 2 is an output signal waveform diagram of the radio frequency front-end control circuit.

[0048] Figure 3 is an output signal waveform diagram of the band-pass filter circuit.

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

[0050] Figure 5 is an output signal waveform diagram of the low-pass filter circuit.

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

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

[0053] Figure 8 2 is a schematic diagram of the circuit principle of the radio frequency front-end control circuit.

[0054] Figure 9 2 is a schematic diagram of the circuit principle of the power distribution circuit.

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

[0056] Figure 11 2 is a schematic diagram of the circuit principle of the wake-up circuit.

[0057] Figure 12 Schematic diagram of the communication process of the ultra-low power passive communication system.

[0058] Reference numerals:

[0059] Passive receiving subsystem 100: source coding module 101, backscatter 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 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 filtering circuit 107, a rectifier circuit 108, a band-pass filtering 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 containing both energy and information to the passive receiving subsystem 100, which is transmitted through free space to the passive receiving subsystem 100. The passive receiving subsystem 100 controls whether the antenna 114 absorbs or reflects 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 incoming RF signal energy, providing 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 uses this to decide 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 average power value of the baseband analog signal to the PID control unit 112. The PID control unit 112 uses the average power 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, ensuring that the RF signal energy is stored as much as possible while still 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. The backscatter control circuit 102 is then used to modulate the data onto the reflected radio frequency signal.

[0065] The RF front-end control circuit 103 acts 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. Conversely, 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 impedance of antenna 114 and the feeder impedance are mismatched, and antenna 114 reflects the incoming RF signal. When CTRL is low, RF1 is isolated from RF2, and the RF feeder impedance reflects the impedance of rectifier circuit 108. The impedance of rectifier circuit 108 is designed to be 50Ω. Therefore, at this time, the impedance of antenna 114 and the RF feeder impedance match, antenna 114 absorbs the incoming RF signal, and the RF signal is sent to rectifier circuit 108.

[0066] The power distribution circuit 110 can divide 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 for programmable resistors. Figure 9 As shown. The power distribution circuit 110 consists of two programmable resistors. 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 respectively, so the 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. Figure 4 The resistance values ​​from top to bottom are R1 and R2, and the power is P1 and P2 respectively, 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 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. Figure 10As shown, in the embodiment, the core IC of the energy management circuit 111 can be selected as BQ25570, and the energy storage element 113 can be selected as a super capacitor. The baseband signal is connected to the VIN pin of the energy management circuit 111, and the VIN pin has a BOOST voltage boosting 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, and in the embodiment, the energy storage element 113 is a super capacitor. The VBAT_OV pin is used to set the overcharge protection, and 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 overcharge. OK_HYST and OK_PROG are used to set the working voltage range of the energy storage element 113, and when the voltage of the energy storage element 113 is higher than OK_HYST, the VBAT_OK pin outputs a high level to indicate 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 to indicate that the energy storage element 113 is not working normally. VOUT is a programmable stable voltage output port, which can output the energy stored in the energy storage element 113 after voltage stabilization, and the VOUT_SET pin is used to set the output voltage value of VOUT. VOUT_EN is the enable pin of the programmable stable voltage output, which is high active, and in the embodiment, VOUT_EN and VBAT_OK are interconnected, that is, only when the energy storage element 113 is working normally, the energy of the energy storage element 113 is output after voltage stabilization to supply the passive receiving subsystem 100. The calculation formulas of VBAT_OV, OK_HYST, OK_PROG and VOUT are as follows:

[0068]

[0069]

[0070]

[0071]

[0072] wherein the typical value of VRDIV is 1.21V. Therefore, through the energy management circuit 111, the energy of the baseband analog signal can be stored, and the energy management circuit 111 can also automatically charge and discharge the energy 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 mode to the working mode. As shown in Figure 11 In the embodiment, the operational amplifier of the wake-up circuit 104 can be selected as a preferred IC, the single Schmidt trigger can be selected as a preferred IC, and the counter can be selected as a preferred IC. The baseband analog signal is connected to the in-phase input terminal of the operational amplifier for equal proportion amplification. In the embodiment, the amplification proportion is 23. Then the input signal is converted into a standard square wave signal by the single Schmidt trigger. The clock input signal of the counter is connected to the output signal of the single Schmidt trigger. When the square wave signal appears a falling edge, the counter counts one time. When the count times reach 256, the 2QD pin outputs a high-level wake-up signal to make the passive receiving subsystem 100 from the low-power mode to the working mode.

[0074] In the embodiment, the microprocessor is selected to realize all functions of the backscattering control circuit 102, the source encoding 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 processed by the baseband signal and the source encoding. Then the output port of the microprocessor is used to control the radio frequency front-end control circuit 103 to modulate the data onto the reflected signal. The microprocessor can be selected as a preferred MCU in the embodiment.

[0075] The communication flow of the integrated transmitter 200 and the passive receiving subsystem 100 is as shown in Figure 12As shown, the passive receiving subsystem 100 is in low-power mode to reduce power consumption as much as possible before receiving the wake-up instruction sent by the integrated transmitter 200. When receiving the wake-up instruction sent by the integrated transmitter 200, the passive receiving subsystem 100 enters working mode. In 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 signals obtained from the outside to the integrated transmitter 200 through the feedback signal transmitter. When there is no task requirement, the passive receiving subsystem 100 sends a sleep instruction to the integrated transmitter 200 to request entering low-power mode. After receiving the sleep instruction, if the integrated transmitter 200 has no task to be processed by the passive receiving subsystem 100, the integrated transmitter 200 sends an acceptance instruction to the passive receiving subsystem 100. After receiving the acceptance instruction, the passive receiving subsystem 100 turns off all external functions and enters low-power mode. Otherwise, if the integrated transmitter 200 has a task to be processed by the passive receiving subsystem 100, the integrated transmitter 200 sends a rejection instruction to the passive receiving subsystem 100, and the passive receiving subsystem 100 continues to run in working mode. In this way, the passive receiving subsystem 100 can process the request sent by the integrated transmitter 200 in real time while keeping low power consumption. Moreover, the passive receiving subsystem 100 will not enter low-power mode without the permission of the integrated transmitter 200, so that the request of the integrated transmitter 200 can be processed in time.

[0076] For those skilled in the art, various corresponding changes and modifications can be made to the technical solutions and concepts described above, and all these changes and modifications shall fall within the protection scope of the present application.

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; when the wake-up signal is received, enters a working mode and performs backscattering on the radio frequency signal; The passive receiving subsystem (100) includes a signal 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 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). The power distribution circuit (110) includes two programmable resistors, and the two programmable resistors are connected in parallel to divide the radio frequency power received by the antenna (114) into two parts, one part flows to the power supply system, and the other part flows to the bandpass filter circuit (109); 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 while being able to demodulate the baseband signal.

2. The ultra-low power passive communication system based on backscattering according to claim 1, characterized in that: The radio frequency front-end control circuit (103) serves as a radio frequency feed line impedance. When the radio frequency feed line impedance matches the antenna (114) impedance, the antenna (114) absorbs radio frequency signals, and conversely, the antenna (114) reflects radio frequency signals. 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 band-pass 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 a wake-up instruction sent by the integrated transmitter (200) in the low-power mode, so as to enable the passive receiving subsystem (100) to enter the working mode from the low-power 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 bits 0 and 1 of the encoded data so that they can be collected and processed by the integrated transmitter (200).

3. The ultra-low power passive communication system based on backscattering according to claim 2, characterized in that: The radio frequency front-end control circuit (103) includes 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 feeder 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 passive communication system based on backscattering according to claim 3, characterized in that: In the feedback signal transmitter, a baseband signal processing module (106) obtains 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 backscatter 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 passive communication system based on backscattering according to claim 1, characterized in that: The steps of the PID closed-loop 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] based on the error e[n], where K p is the proportional 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.

6. The ultra-low power passive communication system based on backscattering according to claim 1, characterized in that: The energy management circuit (111) comprises a 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 stabilizing circuit outputs the voltage of the energy storage element (113) in a regulated manner to supply power to the passive receiving subsystem (100).

7. The ultra-low power passive communication system based on backscattering according to claim 1, characterized in that: The wake-up circuit (104) comprises a voltage amplifier circuit, a single-channel Schmitt trigger and a counter electrically connected in sequence; The voltage amplifying circuit performs voltage amplification on the baseband signal outputted from 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 serves as a clock signal of the counter. Whenever a falling edge appears on 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) switches the passive receiving subsystem (100) from a low power consumption mode to an operating mode.

8. The ultra-low power passive communication system based on backscattering according to any one of claims 1 to 7, 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 low-power mode and put it into working mode; S2. The passive receiving subsystem (100) enters the working mode and 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 instruction, if it has tasks that need to be processed by the passive receiving subsystem (100), it will send a rejection instruction to the passive receiving subsystem (100); otherwise, it will send an acceptance instruction 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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