Remote communication sensing node based on low-power radio frequency energy collection

Abstract

The invention discloses a long-distance communication sensing node based on low-power radio frequency energy collection, and belongs to the field of radio frequency energy collection. The harmonic wave generating and rectifying circuit collects radio frequency energy emitted by a mobile base station and converts the radio frequency energy into direct current energy to generate second harmonic waves, and a harmonic wave amplifying circuit amplifies the second harmonic waves. And the voltage conversion circuit realizes control and storage of direct current energy. The data acquisition circuit acquires sensing data and sends the sensing data to the harmonic modulation circuit, and the harmonic modulation circuit modulates second harmonics by providing bias voltage containing sensing information for the rectification circuit and sends harmonic signals containing the sensing data to the mobile terminal, so that low-power-consumption long-distance harmonic communication is realized. The invention creatively combines low-power-consumption radio frequency energy collection and low-power-consumption harmonic communication technologies, and provides a design scheme of a self-powered long-distance communication sensing node under the condition of not depending on a traditional battery.

Description

Technical Field

[0001] The invention belongs to the field of radio frequency energy collection and relates to a long-distance communication sensor node based on low-power radio frequency energy collection. Background Art

[0002] In IoT applications, a large number of dispersed sensor nodes can effectively monitor environmental information in real time, thereby improving the communication capabilities of IoT. However, traditional sensor nodes usually rely on external batteries or wired cables for power supply, which not only increases the difficulty of maintenance and replacement frequency, but also may cause environmental pollution and other problems. In the literature [F.Amato and S.Hemour, "The Harmonic Tunneling Tag: a Dual-Band Approach to Backscattering Communications," 2019 IEEE Int.Conf.RFID Technol.Appl.(RFID-TA), Pisa, Italy, 2019.] and [K.Gumber, C.Dejous and S.Hemour, "Harmonic Reflection Amplifier for Widespread Backscatter Internet-of-Things," IEEE Trans.Microw.Theory Tech., vol.69, no.1, pp.774-785, Jan.2021.], the harmonic generation circuit constructed using nonlinear devices can realize the conversion of baseband to second harmonic, reducing the problem of self-interference of sensor nodes. However, these studies still require the use of external power supplies and external signal sources to provide voltage and input baseband signals. As an effective solution, RF energy harvesting technology collects RF energy emitted by base stations or dissipated in the environment, converts it into DC power, provides energy for sensor nodes, and achieves battery-free self-powering, thus solving the energy supply problem of nodes.

[0003] However, RF energy harvesting technology is limited by the limited input of electromagnetic waves in space and the low conversion efficiency, resulting in limited ability to rectify and output DC. To ensure the continuous operation of self-powered sensor nodes, existing sensor nodes usually rely on backscatter communication technology to achieve low power consumption characteristics. It activates the circuit by receiving the incident RF signal, modulates the information stored in the node onto the incident signal, and then reflects it to the receiving end. This method avoids complex active circuit design and has lower power consumption, but it also limits the communication distance, which is not conducive to the large-scale deployment of sensor nodes in IoT applications. Therefore, how to achieve long-distance communication in a low-energy collection environment is still an urgent problem. Summary of the invention

[0004] In view of the problems existing in the prior art, the present invention proposes a design method for a long-distance communication sensor node based on low-power radio frequency energy collection. The long-distance communication sensor node based on low-power radio frequency energy collection, by combining low-energy collection and low-power harmonic amplification technology, the proposed sensor node can realize self-powered long-distance communication. The designed sensor node collects weak radio frequency signals in space and converts them into direct current using Schottky diodes to realize system self-powering without the need for external power supply or battery. At the same time, the second harmonic is generated as the information carrier of harmonic communication. The harmonic amplification circuit utilizes the negative resistance characteristics of the tunnel diode to amplify the second harmonic to achieve low-power long-distance harmonic communication. Compared with the prior art, the communication distance of the sensor node can reach more than 40 meters at an input power as low as -20dBm, which solves the problem of limited communication distance of existing low-power nodes in low-energy collection scenarios.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] A long-distance communication sensor node based on low-power radio frequency energy collection. The present invention realizes system self-powering by collecting weak radio frequency signals in space and converting them into direct current, without the need for an external power supply or battery. The second harmonic generated by the long-distance communication sensor node during the energy collection process will be used as a carrier, and the signal will be amplified by an ultra-low power amplifier circuit, and the sensor information will be loaded to realize the long-distance transmission of the sensor information. The long-distance communication sensor node includes a rectifier circuit, a voltage conversion circuit, a data acquisition circuit and a harmonic modulation circuit. The rectifier circuit is composed of a harmonic generation rectifier circuit and a harmonic amplifier circuit: the harmonic generation rectifier circuit collects the radio frequency energy emitted by the mobile base station and converts it into direct current energy using a Schottky diode, and at the same time generates a second harmonic as an information carrier for harmonic communication; the harmonic amplifier circuit uses the negative resistance characteristics of the tunnel diode to amplify the second harmonic to realize low-power long-distance harmonic communication. The voltage conversion circuit realizes the control and storage of the collected and converted direct current energy, and realizes the effective power supply for the subsequent data acquisition circuit. The data acquisition circuit collects the sensor data of the environment and sends the sensor data to the harmonic modulation circuit. The harmonic modulation circuit realizes the modulation of the second harmonic by providing a bias voltage containing the sensing information to the rectifier circuit, and sends the harmonic signal containing the sensing data to the mobile terminal, thereby realizing low-power long-distance harmonic communication. Specifically:

[0007] The rectifier circuit includes a harmonic generating rectifier circuit and a harmonic amplifier circuit. The harmonic generating rectifier circuit uses SMS7630-005LF Schottky diode, collects radio frequency energy and converts it into DC energy input voltage conversion circuit, so as to realize effective power supply for subsequent data acquisition circuit. While completing DC energy collection, the nonlinear characteristics of Schottky diode are used to generate a certain amount of second harmonics to realize harmonic feedback without affecting the rectification efficiency. The harmonic amplifier circuit directly amplifies and modulates the second harmonic generated by the harmonic generating rectifier circuit. Specifically: the harmonic amplifier circuit uses the negative resistance characteristics of the tunnel diode, controls the tunnel diode through the bias voltage containing the sensing information, amplifies and modulates the second harmonic, and feeds back the second harmonic containing the sensing information to the mobile terminal to realize long-distance harmonic communication.

[0008] The voltage conversion circuit includes a voltage control module, an energy storage module and a boost module to realize the control, storage and improvement of the DC energy collected and converted by the rectifier circuit. The voltage control module adopts the BQ25504 chip made by TI, which has the maximum power point tracking function (MPPT), and can adaptively adjust its own input impedance according to the change of input power to control the output power of the rectifier circuit to reach the optimal; the input of the voltage control module is the output voltage of the rectifier circuit, and the output DC energy enters the energy storage module to charge the supercapacitor. After the DC energy stored in the energy storage module is output, the boost module realizes voltage boost, realizing effective power supply for the subsequent data acquisition circuit without any external power supply. The BQ25504 chip used in the voltage control module has an undervoltage protection function. When the DC voltage of the energy storage module drops below the threshold, the subsequent system stops working to save power consumption. The subsequent system will not be started until the rectifier circuit replenishes enough energy for the energy storage module. The threshold voltage of the undervoltage protection function can be controlled by controlling the voltage divider resistance value of the corresponding pin.

[0009] The data acquisition circuit includes an MCU control module and two sensor modules, which are powered by the output energy of the voltage conversion unit. The UART serial port of the MCU control module realizes the collection of temperature, humidity, and carbon dioxide concentration data, and the GPIO port of the MCU is used to control the working cycle of the sensor module. The collected sensor data is automatically sent to the harmonic modulation circuit through the PWM wave for subsequent harmonic modulation.

[0010] The harmonic modulation circuit includes a linear voltage regulator module and a two-choice analog switch module. The linear voltage regulator and the analog switch are powered by the MCU control module in the data acquisition circuit. The linear voltage regulator sets the output voltage to the bias voltage of the tunnel diode in the harmonic amplifier circuit, and the sensor data collected is input into the analog switch in the form of a PWM wave, so that the DC bias containing the sensor information is loaded on the tunnel diode. The tunnel diode amplifies and modulates the second harmonic generated by the rectifier circuit. The modulated OOK signal is fed back to the UAV launch platform and the mobile terminal.

[0011] Furthermore, the rectifier circuit is composed of a harmonic generation rectifier circuit and a harmonic amplifier circuit, including a radio frequency input port RF IN, a bias voltage input port BIAS, a DC voltage output terminal DC OUT of the rectifier circuit, and a second harmonic information output terminal 2 nd DATA OUT. The RF input port receives input RF energy, and the bias voltage input port receives a bias voltage containing sensor information to control the tunnel diode. The DC voltage output terminal DC OUT is connected to IN1 of the voltage control module to power the voltage control module. The second harmonic information output terminal 2 nd DATA OUT is connected to the antenna to realize the transmission of sensor information. The harmonic amplification circuit uses the AI201A model tunnel diode. After measurement, it has a negative resistance characteristic when the bias voltage is 0.247V, which can realize the amplification of the input second harmonic. The bias voltage input port BIAS is connected to the output port OUT4 of the analog switch, and receives the bias voltage containing the sensor information. The bias voltage controls the tunnel diode. At a high level, the tunnel diode is biased, and the tunnel diode amplifies the input second harmonic. At a low level, the tunnel diode does not work and will not amplify the input second harmonic, thereby realizing the amplitude modulation of the second harmonic output by the rectifier circuit. At the harmonic information output port 2 nd DATA OUT outputs the modulated second harmonic signal.

[0012] Furthermore, the voltage control module comprises an input terminal IN1 of the voltage control module, voltage control ports MPPT and R-DIV, voltage divider control resistors R1 and R2, a voltage output port VBAT, and an undervoltage protection port VBAT_OK. R1 and R2 are respectively connected to the MPPT and R-DIV ports to start the maximum power point tracking function of the voltage control module. The voltage control module can control the DC output voltage of the power supply module to maintain at 50% of the circuit open circuit voltage according to the resistance values ​​of R1 and R2. The voltage output port VBAT is connected to the input port IN of the energy storage module to supply power to the energy storage module. The undervoltage protection port VBAT_OK is adjusted according to the value of the DC voltage of the energy storage module. When the voltage of the energy storage module is higher than 3V, VBAT_OK outputs a high level; when the voltage of the energy storage module is lower than 3V, VBAT_OK outputs a low level. The VBAT_OK port is connected to the SHDN port of the boost module to control the opening or closing of the boost module.

[0013] Furthermore, the energy storage module comprises an input port IN of a super capacitor and an output port BATOUT of the super capacitor. The input port IN is connected to an output port VBAT of a voltage control module to charge the energy storage module.

[0014] Furthermore, the boost module comprises an input port BATIN of the boost module, an output port OUT2 of the boost module and a voltage divider port FB, voltage divider resistors R3 and R4, and a chip start port SHDN. The output port BATOUT of the energy storage module is connected to the input port BATIN of the boost module, and is used to supply power to the boost module and is boosted as an input voltage. The voltage divider resistors R3 and R4 are connected to the OUT2 and FB ports respectively, and their resistance values ​​can control the voltage value of the output port OUT2 of the boost module.

[0015] Furthermore, the MCU main control module comprises an input port IN2 of the MCU control module, three GPIO ports GPIO1, GPIO2 and GPIO3, a UART port TX1, RX1, and a sensor signal output port PWM. The output port OUT2 of the boost module is connected to the input port IN2 of the MCU control module as the power supply port of the MCU control module. The UART port is correspondingly connected to the UART port of the sensor module to transmit serial port information. The three GPIO ports are respectively connected to a linear regulator, a two-choice analog switch and a sensor. First, the required sensor is powered through the GPIO port. After the corresponding sensor information is obtained through the UART port, the MCU converts the sensor information into a binary PWM signal, and at the same time, the linear regulator and the analog switch are powered through the GPIO port. The PWM signal is output to the analog switch, and the analog switch outputs a bias voltage containing the sensor information to the tunnel diode to achieve harmonic modulation.

[0016] Further, the sensor module is composed of the required sensors, and only one sensor is used as an example here, including a sensor power port VCC1, a UART port TX2, and a RX2. The sensor UART port is connected to the UART port of the MCU main control module. The GPIO1 port of the MCU main control module supplies power to the sensor VCC1 port, and the sensor starts working. After completing data collection, data reporting is realized through the UART port.

[0017] Furthermore, the linear voltage regulator module is composed of a linear voltage regulator, specifically comprising a power supply port VCC2, a voltage regulator control port SET, and a voltage regulator output port OUT3. VCC2 is controlled by the GPIO2 port of the MCU main control module. After the sensor completes data reporting, the MCU will output a high level through the GPIO2 port to power VCC2. The voltage regulator control port SET is connected to R5 to realize the selection of the voltage regulator value, and the value of the voltage regulator output OUT3 can be controlled by the resistor R5. OUT3 is responsible for outputting the voltage after voltage regulation to the analog switch.

[0018] Furthermore, the analog switch module is mainly composed of a two-choice analog switch, including a power port VCC3, a voltage stabilization input port IN3, a selection signal port SEL, and an output port OUT4. VCC3 is connected to the GPIO3 port of the MCU main control module, and the MCU outputs a high level to turn on the analog switch after the sensor completes data transmission. The voltage stabilization input port IN3 is connected to the output port OUT3 of the linear voltage stabilization module to receive the signal after voltage stabilization. The selection signal port SEL is connected to the PWM port of the MCU main control module. After the sensor completes data reporting, the MCU converts the sensing data into a binary PWM signal and outputs it to the SEL port. The analog switch is selected according to the high and low levels of the signal input to the SEL port. When the level is high, the input signal of the voltage stabilization input port IN3, that is, the voltage stabilization signal, is directly output to the tunnel diode, and when the level is low, the GND low level is output, thereby realizing the output of the bias voltage containing the sensing information to the tunnel diode.

[0019] Beneficial effects of the present invention:

[0020] The present invention provides a long-distance communication sensor node based on low-power radio frequency energy collection. Through the designed rectifier circuit, it can not only realize the collection of environmental radio frequency energy and realize the battery-free self-powered operation of the sensor node, but also can generate second harmonics at an input power as low as -20dBm, and feedback the information of the harmonics. The designed rectifier circuit utilizes the low power consumption characteristics of the tunnel diode to amplify the generated second harmonics, and can achieve a maximum amplification gain of 27.3dB, while the power consumption is as low as 1mW. At the same time, a harmonic modulation circuit is designed, and the environmental data collected by the sensor can be loaded onto the second harmonic through the OOK amplitude modulation method. The proposed system does not need to use a power amplifier at the transmitting end, and can realize long-distance harmonic communication of more than 40m, which greatly reduces the power loss of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a structural block diagram of a long-distance communication sensor node based on low-power radio frequency energy collection provided by an embodiment of the present invention;

[0022] Figure 2 is a circuit structure diagram of a sensor node provided by an embodiment of the present invention;

[0023] Figure 3 is a circuit schematic diagram including a modulation module provided in an embodiment of the present invention;

[0024] Figure 4 It is a data diagram of rectification efficiency and original second harmonic power provided by an embodiment of the present invention.

[0025] Figure 5It is a data diagram of the amplified and modulated second harmonic power provided by an embodiment of the present invention.

[0026] Figure 6 This is a graph of harmonic information data received at a distance of 40 m provided by an embodiment of the present invention. Specific implementation plan

[0027] The present invention is further described in detail below with reference to specific embodiments, but the embodiments of the present invention are not limited thereto.

[0028] This embodiment provides a long-distance communication sensor node based on low-power RF energy collection. The designed rectifier circuit can not only collect environmental RF energy and realize battery-free self-powered operation of the sensor node, but also generate second harmonics and use the harmonics as carriers for information modulation. The designed rectifier circuit utilizes the low power consumption characteristics of the tunnel diode to amplify the generated second harmonics, which can achieve a maximum amplification gain of 27.3dB, while the power consumption is as low as 1mW. After the environmental data is collected, the tunnel diode is controlled by an analog switch, and the environmental data collected by the sensor can be loaded onto the second harmonic through the OOK amplitude modulation method, thereby sending the sensor information to the mobile terminal. The proposed system does not require any input RF signal as an energy carrier or information carrier, can realize system self-powering under low-power energy collection conditions, and realize the transmission of long-distance environmental data of more than 40 meters.

[0029] Example 1

[0030] This example designs a long-distance communication sensor node based on low-power RF energy harvesting.

[0031] Specifically, see Figure 1 , Figure 1 This is a structural block diagram of a long-distance communication sensor node based on low-power radio frequency energy collection provided by an embodiment of the present invention, including:

[0032] The rectifier circuit includes a harmonic generation rectifier circuit and a harmonic amplifier circuit. The harmonic generation rectifier circuit uses SMS7630-005LF Schottky diode, which collects radio frequency energy and converts it into DC energy input voltage conversion circuit to achieve effective power supply for subsequent data acquisition circuits. While completing DC energy collection, the Schottky diode nonlinearity is used to generate a certain amount of second harmonics to achieve harmonic feedback without affecting the rectification efficiency. The harmonic amplifier circuit uses the negative resistance characteristics of the tunnel diode AI201A, controls the tunnel diode through the bias voltage containing sensor information, amplifies and modulates the second harmonic, and feeds back the second harmonic containing sensor information to the mobile terminal to achieve long-distance harmonic communication.

[0033] The voltage conversion circuit includes a voltage control module, an energy storage module and a boost module to control, store and improve the DC energy collected and converted by the energy collection unit. The voltage control module has a maximum power point tracking function (MPPT), which can adaptively adjust its own input impedance according to the change of input power to control the output power of the rectifier circuit to achieve the optimal. The DC energy output by the voltage control module enters the energy storage module to charge the supercapacitor. After the DC energy stored in the energy storage module is output, the boost module realizes voltage boost, realizing effective power supply for the subsequent data acquisition circuit without the need for an external power supply. The voltage control module has an undervoltage protection function. When the DC voltage of the energy storage module drops below the threshold, the subsequent system stops working to save power consumption. The subsequent system will not be started until the rectifier circuit replenishes enough energy for the energy storage module.

[0034] The data acquisition circuit includes an MCU control module and two sensor modules, which are powered by the output energy of the voltage conversion unit. The UART serial port of the MCU control module is used to collect temperature, humidity, and carbon dioxide concentration data, and the GPIO port is used to control the sensor working cycle. The collected sensor data is automatically sent to the harmonic modulation circuit through the PWM wave for subsequent harmonic modulation.

[0035] The harmonic modulation circuit includes a linear voltage regulator module and a two-choice analog switch module. The linear regulator and the analog switch are powered by the MCU control module in the data acquisition circuit. The linear regulator sets the output voltage to the bias voltage of the tunnel diode, and the collected sensor data is input into the analog switch in the form of a PWM wave, so that the DC bias containing the sensor information is loaded on the tunnel diode. The tunnel diode amplifies and modulates the second harmonic generated by the rectifier circuit. The modulated OOK signal is fed back to the UAV launch platform and the mobile terminal.

[0036] The circuit of this embodiment will be described in detail.

[0037] The rectifier circuit is composed of a harmonic generation rectifier circuit and a harmonic amplifier circuit, including a radio frequency input port RF IN, a bias voltage input port BIAS, a DC voltage output terminal DC OUT of the rectifier circuit, and a second harmonic information output terminal 2 nd DATA OUT. The RF input port receives input RF energy, and the bias voltage input port receives the bias voltage containing the sensing information to control the tunnel diode. The output DC OUT of the rectifier circuit is connected to IN1 of the voltage control module to power the voltage control module. Harmonic output terminal 2 ndDATA OUT is connected to the antenna to realize the transmission of sensor information. The harmonic amplification circuit mainly uses the AI201A model tunnel diode. After measurement, it has a negative resistance characteristic when the bias voltage is 0.247V, which can realize the amplification of the input second harmonic. The harmonic amplification circuit directly amplifies and modulates the second harmonic generated by the harmonic generation rectifier circuit. The bias voltage port BIAS is connected to the output port OUT4 of the analog switch, and receives the bias voltage containing the sensor information. The bias voltage controls the tunnel diode. At a high level, the tunnel diode is biased, and the tunnel diode amplifies the input second harmonic. At a low level, the tunnel diode does not work and will not amplify the input second harmonic, thereby realizing the amplitude modulation of the second harmonic output by the rectifier circuit. At the harmonic information output port 2 nd DATAOUT outputs the modulated second harmonic signal.

[0038] The voltage control module includes an input terminal IN1 of the voltage control module; voltage control ports MPPT and R-DIV; voltage divider control resistors R1 and R2; voltage output port VBAT; and undervoltage protection port VBAT_OK. R1 and R2 are respectively connected to the MPPT and R-DIV ports to start the maximum power point tracking function of the voltage control module. The voltage control module can control the DC output voltage of the power supply module to maintain at 50% of the circuit open circuit voltage according to the resistance values ​​of R1 and R2. The VBAT port is connected to the input port IN of the energy storage module to supply power to the energy storage module. The undervoltage protection port VBAT_OK is adjusted according to the value of the DC voltage of the energy storage module. When the voltage of the energy storage module is higher than 3V, VBAT_OK outputs a high level; when the voltage of the energy storage module is lower than 3V, VBAT_OK outputs a low level. The VBAT_OK port is connected to the SHDN port of the boost module to control the on or off of the boost module.

[0039] The energy storage module comprises an input port IN of a super capacitor and an output port BATOUT of the super capacitor. The output port VBAT of the voltage control module is connected to IN to charge the energy storage module.

[0040] The boost module comprises an input port BATIN of the boost module; an output port OUT2 of the boost module and a voltage divider port FB; voltage divider resistors R3 and R4; and a chip start port SHDN. The output port BATOUT of the energy storage module is connected to the input port BATIN of the boost module, which supplies power to the boost module and is boosted as an input voltage. The voltage divider resistors R3 and R4 are connected to the OUT2 and FB ports respectively, and their resistance values ​​can control the voltage value of the output port OUT2 of the boost module.

[0041] The MCU main control module includes an input port IN2 of the MCU control module; three GPIO ports GPIO1, GPIO2 and GPIO3; a UART port TX1, RX1; and a sensor signal output port PWM. The output port OUT2 of the boost module is connected to the input port IN2 of the MCU control module as the power supply port of the MCU control module. The UART port is correspondingly connected to the UART port of the sensor module to transmit serial port information. The three GPIO ports are respectively connected to the linear regulator, the two-choice analog switch and the sensor. Through program control, the required sensor is first powered through the GPIO port. After the corresponding sensor information is obtained through the UART port, the MCU converts the sensor information into a binary PWM signal, and at the same time powers the linear regulator and the analog switch through the GPIO port. The PWM signal is output to the analog switch, and the analog switch outputs a bias voltage containing the sensor information to the tunnel diode to achieve harmonic modulation.

[0042] The sensor module can be composed of the required sensors. Here, only one sensor is used as an example, including a sensor power port VCC1, a UART port TX2, and a RX2. The sensor UART port is connected to the UART port of the MCU main control module. The GPIO1 port of the MCU main control module supplies power to the sensor VCC1 port, and the sensor starts working. After completing data collection, data reporting is realized through the UART port.

[0043] The linear voltage regulator module is composed of a linear voltage regulator, specifically including a power supply port VCC2, a voltage regulator control port SET, and a voltage regulator output port OUT3. VCC2 is controlled by the GPIO2 port of the MCU main control module. After the sensor completes data reporting, the MCU will output a high level through the GPIO2 port to power VCC2. The voltage regulator control port SET is connected to R5 to realize the selection of the voltage regulator value, and the value of the voltage regulator output OUT3 can be controlled by the resistor R5. OUT3 is responsible for outputting the voltage after voltage regulation to the analog switch.

[0044] The analog switch module is mainly composed of a two-choice analog switch, including a power supply port VCC3, a voltage stabilization input port IN3, a selection signal port SEL, and an output port OUT4. VCC3 is connected to the GPIO3 port of the MCU main control module, and the MCU outputs a high level to turn on the analog switch after the sensor completes data transmission. The voltage stabilization input port IN3 is connected to the output port OUT3 of the linear voltage stabilization module to receive the signal after voltage stabilization. The selection signal port SEL is connected to the PWM port of the MCU main control module. After the sensor completes data reporting, the MCU converts the sensing data into a binary PWM signal and outputs it to the SEL port. The analog switch is selected according to the high and low levels of the signal input by the SEL port. When the high level is high, the input signal of the voltage stabilization input port IN3, that is, the voltage stabilization signal, is directly output to the tunnel diode, and when the low level is low, the GND low level is output, thereby realizing the output of the bias voltage containing the sensing information to the tunnel diode.

[0045] Specifically, the circuit schematic diagram of the modulation module in this embodiment is as follows: Figure 3 As shown. The Schottky diode model selected for the harmonic generation rectifier circuit is SMS7630-005LF. The input impedance of the rectifier circuit is matched to 50Ω by the matching network. The capacitor connected after the matching network is 100pF, and the capacitor in parallel with the load is 300pF. The output end is divided into a DC branch and a harmonic branch. The DC branch is connected to the voltage conversion circuit, and the generated DC energy is collected for use by the data acquisition circuit. The harmonic branch is connected to the harmonic amplification circuit through a 1pF capacitor. The tunnel diode model used in the harmonic amplification circuit is AI201A, and its bias voltage is provided by the harmonic modulation circuit. The amplified and modulated harmonic signal generated by it is radiated and fed back to the mobile terminal. The proposed rectifier circuit can work stably at an input power as low as -20dBm. Figure 4 The figure is a data graph of the rectification efficiency and the original second harmonic power provided by the embodiment of the present invention. The proposed harmonic amplifier circuit based on the tunnel diode can achieve high gain amplification of the second harmonic, and the proposed harmonic modulation circuit can effectively modulate the second harmonic. Figure 5 It is a data diagram of the modulated and amplified second harmonic provided by an embodiment of the present invention.

[0046] In this embodiment, a long-distance communication sensor node based on low-power radio frequency energy collection is provided. Using wireless radio frequency energy collection technology, the rectifier circuit can feed back the second harmonic to the transmitter while completing energy collection, realize the calibration of the transceiver antenna, and reduce the link loss. The proposed rectifier circuit has a wide input power range and can operate at an input power as low as -20dBm. In order to achieve long-distance harmonic communication, a low-power harmonic amplifier circuit based on a tunnel diode is included in the rectifier circuit. By using the rectifier circuit for energy collection and providing a stable bias voltage for the tunnel diode, the second harmonic generated by the rectifier circuit can be amplified in time to achieve low-power long-distance harmonic communication. Finally, a self-powered sensor node is constructed to collect environmental data. Using an analog switch to control the tunnel diode, OOK modulation can be implemented on the second harmonic, and the sensor information can be fed back to the mobile terminal. The proposed system can realize environmental data collection under low power conditions. There is no need to use a power amplifier in the transmitter, and long-distance harmonic communication of more than 40 meters can be achieved. Figure 6 The harmonic information received by the mobile terminal at a distance of 40 meters from the proposed sensor node is shown. Clearer sensing data can be observed, indicating that the designed sensor node can achieve long-distance harmonic communication.

[0047] The above-described embodiments merely express the implementation methods of the present invention, but they should not be understood as limiting the scope of the present invention. It should be pointed out that for those skilled in the art, several modifications and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. A long-distance communication sensor node based on low-power radio frequency energy collection, characterized in that: The second harmonic generated by the long-distance communication sensor node in the energy collection process will be used as a carrier, and the signal will be amplified through an ultra-low power amplifier circuit, and the sensor information will be loaded to realize the long-distance transmission of the sensor information; the long-distance communication sensor node includes a rectifier circuit, a voltage conversion circuit, a data acquisition circuit and a harmonic modulation circuit; specifically: The rectifier circuit is composed of a harmonic generation rectifier circuit and a harmonic amplifier circuit: the harmonic generation rectifier circuit collects the radio frequency energy emitted by the mobile base station and converts it into DC energy using a Schottky diode, while generating a second harmonic as an information carrier for harmonic communication; the harmonic amplifier circuit utilizes the negative resistance characteristics of the tunnel diode to amplify the second harmonic, thereby realizing low-power long-distance harmonic communication; The voltage conversion circuit realizes the control and storage of the collected converted DC energy, and realizes the effective power supply for the subsequent data acquisition circuit; The data acquisition circuit collects sensor data of the environment and sends the sensor data to the harmonic modulation circuit; The harmonic modulation circuit realizes modulation of the second harmonic by providing a bias voltage containing sensing information to the rectifier circuit, and sends the harmonic signal containing the sensing data to the mobile terminal, thereby realizing low-power consumption long-distance harmonic communication.

2. A long-distance communication sensor node based on low-power radio frequency energy collection according to claim 1, characterized in that: The rectifier circuit includes a harmonic generating rectifier circuit and a harmonic amplifier circuit; the harmonic generating rectifier circuit uses SMS7630-005LF Schottky diode, collects radio frequency energy and converts it into direct current energy for input into a voltage conversion circuit; the harmonic amplifier circuit directly amplifies and modulates the second harmonic generated by the harmonic generating rectifier circuit, specifically: the harmonic amplifier circuit uses a tunnel diode to amplify and modulate the second harmonic, and feeds back the second harmonic containing sensing information to a mobile terminal to realize long-distance harmonic communication.

3. A long-distance communication sensor node based on low-power radio frequency energy collection according to claim 2, characterized in that: The voltage conversion circuit includes a voltage control module, an energy storage module and a boost module to achieve control, storage and improvement of the DC energy collected and converted by the rectifier circuit; specifically: The voltage control module adopts the BQ25504 chip, the input of the voltage control module is the output voltage of the rectifier circuit, and the output DC energy enters the energy storage module to charge the supercapacitor; the DC energy stored in the energy storage module is output and the voltage is increased by the boost module without any external power supply; the BQ25504 chip used in the voltage control module has an undervoltage protection function, and the threshold voltage of the undervoltage protection function is controlled by controlling the resistance value of the voltage divider resistor.

4. A long-distance communication sensor node based on low-power radio frequency energy collection according to claim 3, characterized in that: The data acquisition circuit includes an MCU control module and two sensor modules, which are powered by the output energy of the voltage conversion unit; the UART serial port of the MCU control module realizes the collection of temperature, humidity, and carbon dioxide concentration data, and uses the GPIO port of the MCU to control the working cycle of the sensor module; the collected sensor data is automatically sent to the harmonic modulation circuit through the PWM wave for subsequent harmonic modulation.

5. A long-distance communication sensor node based on low-power radio frequency energy collection according to claim 4, characterized in that: The harmonic modulation circuit includes a linear voltage regulator module and a two-choice analog switch module; the linear voltage regulator and the analog switch are powered by the MCU control module in the data acquisition circuit; the linear voltage regulator sets the output voltage as the bias voltage of the tunnel diode in the harmonic amplification circuit, and the collected sensor data is input into the analog switch in the form of a PWM wave, so that the DC bias containing the sensor information is loaded on the tunnel diode; the tunnel diode amplifies and modulates the second harmonic generated by the rectifier circuit; The modulated OOK signal is fed back to the UAV launch platform and mobile terminal.

6. A long-distance communication sensor node based on low-power radio frequency energy collection according to claim 5, characterized in that: The rectifier circuit comprises a radio frequency input port RF IN, a bias voltage input port BIAS, a DC voltage output terminal DC OUT of the rectifier circuit, and a second harmonic information output terminal 2 nd DATA OUT; the RF input port receives input RF energy, and the bias voltage input port receives a bias voltage containing sensor information to control the tunnel diode; the DC voltage output terminal DC OUT is connected to IN1 of the voltage control module to power the voltage control module; the second harmonic information output terminal 2 nd DATA OUT is connected to the antenna to realize the transmission of sensor information; the harmonic amplification circuit uses the AI201A model tunnel diode; the bias voltage input port BIAS is connected to the output port OUT4 of the analog switch to receive the bias voltage containing the sensor information, and the bias voltage controls the tunnel diode. When the level is high, the tunnel diode is biased, and the tunnel diode amplifies the input second harmonic. When the level is low, the tunnel diode does not work, and the amplitude modulation of the second harmonic output by the rectifier circuit is realized; at the harmonic information output port 2 nd DATA OUT outputs the modulated second harmonic signal; The voltage control module comprises an input terminal IN1 of the voltage control module, voltage control ports MPPT and R-DIV, voltage divider control resistors R1 and R2, a voltage output port VBAT, and an undervoltage protection port VBAT_OK; wherein R1 and R2 are respectively connected to the MPPT and R-DIV ports to start the maximum power point tracking function of the voltage control module; the voltage control module controls the DC output voltage of the power supply module to be maintained at 50% of the circuit open circuit voltage according to the resistance values ​​of R1 and R2; the voltage output port VBAT is connected to the input port IN of the energy storage module to supply power to the energy storage module; the undervoltage protection port VBAT_OK is adjusted according to the value of the DC voltage of the energy storage module; when the voltage of the energy storage module is higher than 3V, VBAT_OK outputs a high level; when the voltage of the energy storage module is lower than 3V, VBAT_OK outputs a low level; the VBAT_OK port is connected to the SHDN port of the boost module to control the on or off of the boost module; The energy storage module comprises an input port IN of a supercapacitor and an output port BATOUT of the supercapacitor; the input port IN is connected to the output port VBAT of the voltage control module to charge the energy storage module; The boost module comprises an input port BATIN of the boost module, an output port OUT2 of the boost module and a voltage dividing port FB, voltage dividing resistors R3 and R4, and a chip opening port SHDN; the output port BATOUT of the energy storage module is connected to the input port BATIN of the boost module; the voltage dividing resistors R3 and R4 are respectively connected to the OUT2 and FB ports, and their resistance values ​​control the voltage value of the output port OUT2 of the boost module; The MCU main control module comprises an input port IN2 of the MCU control module, three GPIO ports GPIO1, GPIO2 and GPIO3, a UART port TX1, RX1, and a sensor signal output port PWM; the output port OUT2 of the boost module is connected to the input port IN2 of the MCU control module as the power supply port of the MCU control module; the UART port is correspondingly connected to the UART port of the sensor module to transmit serial port information; the three GPIO ports are respectively connected to a linear regulator, a two-choice analog switch and a sensor; firstly, the required sensor is powered through the GPIO port, and after the corresponding sensor information is obtained through the UART port, the MCU converts the sensor information into a binary PWM signal, and at the same time powers the linear regulator and the analog switch through the GPIO port; the PWM signal is output to the analog switch, and the analog switch outputs a bias voltage containing the sensor information to the tunnel diode to realize harmonic modulation; The sensor module is composed of the required sensors, and is described as a sensor, including a sensor power port VCC1, a UART port TX2, and a RX2; the sensor UART port is connected to the UART port of the MCU main control module; the GPIO1 port of the MCU main control module supplies power to the sensor VCC1 port, the sensor starts working, and after completing data collection, data reporting is realized through the UART port; The linear voltage regulator module is composed of a linear voltage regulator, including a power supply port VCC2, a voltage regulator control port SET, and a voltage regulator output port OUT3; wherein VCC2 is controlled by the GPIO2 port of the MCU main control module. After the sensor completes data reporting, the MCU outputs a high level through the GPIO2 port to power VCC2; the voltage regulator control port SET is connected to R5 to realize the selection of the voltage regulator value, and the value of the voltage regulator output OUT3 is controlled by the resistor R5; OUT3 is responsible for outputting the voltage after voltage regulation to the analog switch; The analog switch module is mainly composed of a two-choice analog switch, including a power port VCC3, a voltage stabilization input port IN3, a selection signal port SEL and an output port OUT4; wherein VCC3 is connected to the GPIO3 port of the MCU main control module, and the MCU outputs a high level to turn on the analog switch after the sensor completes data transmission; the voltage stabilization input port IN3 is connected to the output port OUT3 of the linear voltage stabilization module to receive the signal after voltage stabilization; the selection signal port SEL is connected to the PWM port of the MCU main control module, and after the sensor completes data reporting, the MCU converts the sensing data into a binary PWM signal and outputs it to the SEL port, and the analog switch is selected according to the high and low levels of the signal input to the SEL port, and when the level is high, the input signal of the voltage stabilization input port IN3, that is, the voltage stabilization signal, is directly output to the tunnel diode, and when the level is low, the GND low level is output, thereby realizing the output of the bias voltage containing the sensing information to the tunnel diode.

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