A long-distance communication sensor node based on low-power radio frequency energy harvesting

Abstract

A long-distance communication sensor node based on low-power radio frequency energy collection belongs to the field of radio frequency energy collection. It is composed of a harmonic generation rectifier circuit, a voltage conversion circuit, a data acquisition circuit and a harmonic modulation circuit: the harmonic generation rectifier circuit collects the radio frequency energy emitted by the mobile base station and converts it into DC energy to generate second harmonics, which are amplified by the harmonic amplifier circuit. The voltage conversion circuit realizes the control and storage of DC energy. The data acquisition circuit collects the sensing data and sends it 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. The present invention innovatively combines low-power radio frequency energy collection and low-power harmonic communication technology to provide a design scheme for a self-powered long-distance communication sensor node without relying on traditional batteries.

Description

Technical Field

[0001] The present 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 enhancing IoT communication capabilities. However, traditional sensor nodes typically rely on external batteries or wired cables for power, which not only increases maintenance difficulty 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.], harmonic generation circuits constructed using nonlinear devices can achieve conversion from fundamental frequency to second harmonic, reducing the problem of self-interference in sensor nodes. However, these studies still require an external power supply and external signal source to provide voltage and input fundamental frequency signal. 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 from space and low conversion efficiency, resulting in a limited ability to rectify and output DC. To ensure the continuous operation of self-powered sensor nodes, existing sensor nodes typically rely on backscatter communication technology to achieve low power consumption. This technology activates the circuit by receiving an 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 low 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 harvesting environment remains an urgent problem. Summary of the Invention

[0004] In response to 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 achieve 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 achieve system self-powering without the need for an external power supply or battery. At the same time, the second harmonic is generated as the information carrier for harmonic communication. The harmonic amplification circuit uses the negative resistance characteristics of the tunnel diode to amplify the second harmonic to achieve low-power long-distance harmonic communication. Compared with the existing technology, the communication distance of the sensor node can reach more than 40 meters at an input power as low as -20dBm, solving 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 RF energy harvesting is described. This invention collects weak RF signals in space and converts them into DC, achieving self-powered operation without the need for an external power supply or battery. The second harmonic generated by the energy harvesting process in the long-distance communication sensor node serves as a carrier wave. This signal is amplified by an ultra-low-power amplifier circuit and loaded with sensor information, enabling long-distance transmission of this sensor information. The long-distance communication sensor node comprises a rectifier circuit, a voltage conversion circuit, a data acquisition circuit, and a harmonic modulation circuit. The rectifier circuit consists of a harmonic generation rectifier circuit and a harmonic amplifier circuit. The harmonic generation rectifier circuit collects RF energy transmitted by a mobile base station and converts it into DC energy using a Schottky diode, simultaneously generating a second harmonic that serves as the information carrier for harmonic communication. The harmonic amplifier circuit utilizes the negative resistance of a tunnel diode to amplify the second harmonic, thereby achieving low-power long-distance harmonic communication. The voltage conversion circuit controls and stores the collected and converted DC energy, effectively powering the subsequent data acquisition circuit. The data acquisition circuit collects sensor data of the environment and transmits this data to the harmonic modulation circuit. The harmonic modulation circuit modulates 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 long-distance harmonic communication. Specifically:

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

[0008] The voltage conversion circuit comprises a voltage control module, an energy storage module, and a boost module, which control, store, and boost the DC energy collected and converted by the rectifier circuit. The voltage control module utilizes the BQ25504 chip manufactured by TI, which features maximum power point tracking (MPPT). This chip adaptively adjusts its input impedance based on changes in input power, thereby optimizing the output power of the rectifier circuit. The voltage control module receives 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 then boosted by the boost module, effectively powering the subsequent data acquisition circuit without the need for an external power supply. The BQ25504 chip used in the voltage control module features an undervoltage protection function. When the DC voltage of the energy storage module drops below a threshold, the subsequent system stops operating to save power. The subsequent system will not start until the rectifier circuit has replenished sufficient energy for the energy storage module. The threshold voltage of the undervoltage protection function can be controlled by controlling the value of the voltage divider resistor on the corresponding pin.

[0009] The data acquisition circuit includes an MCU control module and two sensor modules, powered by the output energy of a voltage conversion unit. The MCU control module's UART serial port collects temperature, humidity, and carbon dioxide concentration data, and the MCU's GPIO port controls the sensor module's duty cycle. The collected sensor data is automatically transmitted to a harmonic modulation circuit via PWM waves for subsequent harmonic modulation.

[0010] The harmonic modulation circuit includes a linear voltage regulator module and a two-choice analog switch module. The linear regulator and analog switch are powered by the MCU control module in the data acquisition circuit. The linear regulator sets its output voltage to the bias voltage of the tunnel diode in the harmonic amplification circuit. Simultaneously, the collected sensor data is input into the analog switch in the form of a PWM wave, applying a DC bias containing the sensor information to the tunnel diode. The tunnel diode amplifies and modulates the second harmonic generated by the rectifier circuit. The resulting OOK signal is fed back to the drone launch platform and 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 sensing 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 of 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 includes 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 connected to the MPPT and R-DIV ports, respectively, to activate 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 it at 50% of the open-circuit voltage based on 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 based on the DC voltage value of the energy storage module. When the energy storage module voltage is higher than 3V, VBAT_OK outputs a high level; when the energy storage module voltage 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 whether the boost module is on or off.

[0013] Furthermore, 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.

[0014] Furthermore, the boost module includes a boost module input port BATIN, a boost module output port OUT2, a voltage divider port FB, voltage divider resistors R3 and R4, and a chip enable port SHDN. The energy storage module output port BATOUT is connected to the boost module input port BATIN, providing power to the boost module and boosting its 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 at the boost module output port OUT2.

[0015] Furthermore, 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, serving as the power supply port of the MCU control module. The UART port and the UART port of the sensor module are correspondingly connected 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 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.

[0016] Furthermore, the sensor module is composed of the required sensors. Here, using only one sensor as an example, it includes a sensor power port VCC1 and two UART ports, TX2 and RX2. The sensor UART port is connected to the UART port of the MCU main control module. The MCU main control module's GPIO1 port powers the sensor VCC1 port, and the sensor starts operating. After completing data acquisition, the data is reported via the UART port.

[0017] Furthermore, the linear voltage regulator module comprises 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 MCU's GPIO2 port. After the sensor completes data reporting, the MCU outputs a high level through GPIO2 to power VCC2. The voltage regulator control port SET is connected to R5 to select the regulated voltage value. Resistor R5 controls the value of the regulated voltage output OUT3. OUT3 outputs the regulated voltage to the analog switch.

[0018] Furthermore, the analog switch module is mainly composed of a two-choice analog switch, including a power supply port VCC3, a voltage regulator input port IN3, a selection signal port SEL and an output port OUT4. Among them, 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 regulator input port IN3 is connected to the output port OUT3 of the linear voltage regulator module to receive the signal after voltage regulation. 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 level is high, the input signal of the voltage regulator input port IN3, that is, the voltage regulator signal, is directly output to the tunnel diode. When the level is low, the GND low level is output, thereby outputting 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 generate second harmonics at an input power as low as -20dBm, and use the harmonics to feedback information. 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. At the same time, a harmonic modulation circuit is designed, which can load the environmental data collected by the sensor onto the second harmonic through the OOK amplitude modulation method. The proposed system does not require a power amplifier at the transmitting end to achieve long-distance harmonic communication of more than 40m, greatly reducing the power loss of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] 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;

[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 schematic diagram of a circuit including a modulation module provided in an embodiment of the present invention;

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

[0025] Figure 5This 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 diagram 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 will be further described in detail below with reference to specific examples, 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 radio frequency energy collection. The designed rectifier circuit 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 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 sensing information to the mobile terminal. The proposed system does not require any input radio frequency signal as an energy carrier or information carrier, can realize system self-powering under low-power energy collection conditions, and can 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 block diagram of a long-distance communication sensor node based on low-power radio frequency energy harvesting provided by an embodiment of the present invention, including:

[0032] The rectifier circuit consists of a harmonic generation rectifier circuit and a harmonic amplifier circuit. The harmonic generation rectifier circuit uses an SMS7630-005LF Schottky diode to collect RF energy and convert it into DC energy for input into the voltage conversion circuit, effectively powering the subsequent data acquisition circuit. While simultaneously collecting DC energy, the Schottky diode's nonlinearity generates a certain amount of second harmonics for harmonic feedback without affecting rectification efficiency. The harmonic amplifier circuit exploits the negative resistance of the AI201A tunnel diode. It controls the tunnel diode with a bias voltage containing sensor information, amplifying and modulating the second harmonics. This second harmonic, containing sensor information, is then fed back to the mobile terminal, enabling long-distance harmonic communication.

[0033] The voltage conversion circuit comprises a voltage control module, an energy storage module, and a boost module, which control, store, and enhance the DC energy collected and converted by the energy harvesting unit. The voltage control module features maximum power point tracking (MPPT), adaptively adjusting its input impedance based on changes in input power to optimize the output power of the rectifier circuit. The DC energy output by the voltage control module enters the energy storage module to charge the supercapacitor. The DC energy stored in the energy storage module is then boosted by the boost module, effectively powering the subsequent data acquisition circuits without the need for an external power supply. The voltage control module features undervoltage protection. When the DC voltage of the energy storage module drops below a threshold, the subsequent systems are shut down to save power. Subsequent systems will not start until the rectifier circuit has replenished sufficient energy for the energy storage module.

[0034] The data acquisition circuit comprises an MCU control module and two sensor modules, powered by the output energy of a voltage conversion unit. The MCU's UART serial port is used to collect temperature, humidity, and carbon dioxide concentration data, while the GPIO port controls the sensor's duty cycle. The collected sensor data is automatically transmitted to the harmonic modulation circuit via PWM waves 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 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. Simultaneously, the collected sensor data is input into the analog switch in the form of a PWM wave, applying a DC bias containing the sensor information to the tunnel diode. The tunnel diode amplifies and modulates the second harmonic generated by the rectifier circuit. The resulting OOK signal is fed back to the drone launch platform and 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 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 port 2 ndDATA OUT is connected to the antenna to realize the transmission of sensor information. The harmonic amplifier 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 amplifier 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 of 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; a voltage output port VBAT; and an undervoltage protection port VBAT_OK. R1 and R2 are connected to the MPPT and R-DIV ports, respectively, to activate 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 it at 50% of the circuit open-circuit voltage based on 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 DC voltage value 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 / off of the boost module.

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

[0040] The boost module comprises a boost module input port (BATIN); a boost module output port (OUT2) and a voltage divider port (FB); voltage divider resistors R3 and R4; and a chip enable port (SHDN). The energy storage module output port (BATOUT) is connected to the boost module input port (BATIN), providing power to the boost module and boosting its input voltage. Voltage divider resistors R3 and R4 are connected to ports OUT2 and FB, respectively, and their resistance values ​​control the voltage at the boost module output port (OUT2).

[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, serving 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. 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 any desired sensors. Here, a single sensor is used as an example. It includes a sensor power port (VCC1) and two UART ports (TX2 and RX2). The sensor's UART port is connected to the UART port of the MCU main control module. The MCU's GPIO1 port supplies power to the sensor's VCC1 port, activating the sensor. After data acquisition is complete, the sensor reports the data via the UART port.

[0043] The linear voltage regulator module comprises a linear voltage regulator, specifically a power supply port VCC2, a voltage regulator control port SET, and a voltage regulator output port OUT3. VCC2 is controlled by the MCU's GPIO2 port. After the sensor completes data reporting, the MCU outputs a high level through GPIO2 to power VCC2. The voltage regulator control port SET is connected to R5 to select the regulated voltage value. Resistor R5 controls the value of the regulated output OUT3. OUT3 outputs the regulated voltage 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 regulator input port IN3, a selection signal port SEL, and an output port OUT4. Among them, VCC3 is connected to the GPIO3 port of the MCU main control module. After the sensor completes data transmission, the MCU outputs a high level to turn on the analog switch. The voltage regulator input port IN3 is connected to the output port OUT3 of the linear voltage regulator module to receive the signal after voltage regulation. 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 from the SEL port. When the level is high, the input signal of the voltage regulator input port IN3, that is, the voltage regulator signal, is directly output to the tunnel diode. When the level is low, the GND low level is output, thereby outputting the bias voltage containing the sensing information to the tunnel diode.

[0045] Specifically, the circuit schematic diagram including the modulation module of 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 operate stably at an input power as low as -20dBm. Figure 4 This is a data graph of the rectification efficiency and original second harmonic power provided by the embodiment of the present invention. The proposed harmonic amplifier circuit based on 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 This 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 RF energy harvesting is provided. Leveraging wireless RF energy harvesting technology, a rectifier circuit simultaneously feeds back the second harmonic to the transmitter, enabling transceiver antenna calibration and reducing link loss. The proposed rectifier circuit has a wide input power range and can operate at input powers as low as -20 dBm. To enable long-distance harmonic communication, a low-power harmonic amplifier circuit based on a tunnel diode is incorporated into the rectifier circuit. By utilizing the rectifier circuit for energy harvesting and providing a stable bias voltage for the tunnel diode, the second harmonic generated by the rectifier circuit can be periodically amplified, enabling low-power, long-distance harmonic communication. Finally, a self-powered sensor node is constructed that can collect environmental data. Using analog switches to control the tunnel diode, OOK modulation can be implemented on the second harmonic, feeding the sensor information back to a mobile terminal. The proposed system enables environmental data acquisition at low power. It eliminates the need for a power amplifier in the transmitter and enables long-distance harmonic communication exceeding 40 meters. Figure 6 The harmonic information received by the proposed sensor node at a distance of 40 meters from the mobile terminal is shown. Clear 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 should not be understood as limiting the scope of the present invention. It should be pointed out that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention, which all fall within the scope of protection of the present invention.

Claims

1. A long-distance communication sensor node based on low-power radio frequency energy harvesting, characterized in that: 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 loaded with sensing information to achieve long-distance transmission of sensing 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 radio frequency energy transmitted 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 characteristic 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, thereby realizing 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 modulates 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 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 generation rectifier circuit and a harmonic amplifier circuit; the harmonic generation rectifier circuit uses an SMS7630-005LF Schottky diode to collect radio frequency energy and convert 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 generation 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 achieve 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 control, store and improve the DC energy collected and converted by the rectifier circuit; specifically: The voltage control module uses the BQ25504 chip. The input of the voltage control module is the output voltage of the rectifier circuit. 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 a voltage conversion unit. The UART serial port of the MCU control module collects temperature, humidity, and carbon dioxide concentration data, and uses the MCU's GPIO port to control the working cycle of the sensor module. The collected sensor data is automatically sent to the harmonic modulation circuit through PWM waves for subsequent harmonic modulation.

5. The 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. The long-distance communication sensor node based on low-power radio frequency energy harvesting 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 the bias voltage containing the sensing 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, and receives the bias voltage containing the sensor information. The bias voltage controls the tunnel diode. When the voltage is high, the tunnel diode is biased, and the tunnel diode amplifies the input second harmonic. When the voltage 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 includes 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 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 includes 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 includes a boost module input port BATIN, a boost module output port OUT2 and a voltage divider port FB, voltage divider resistors R3 and R4, and a chip enable port SHDN; the energy storage module output port BATOUT is connected to the boost module input port BATIN; the voltage divider resistors R3 and R4 are connected to the OUT2 and FB ports respectively, and their resistance values ​​control the voltage value of the boost module output port OUT2; 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, serving as the power supply port of the MCU control module; the UART port is correspondingly connected to the UART port of the sensor module for transmitting serial port information; the three GPIO ports are respectively connected to a linear regulator, a two-choice analog switch and a sensor; first, power is supplied to the required sensor 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 simultaneously 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; The sensor module is composed of the required sensors. For example, one sensor is used as an example, and includes a sensor power port VCC1 and two UART ports TX2 and 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 reports data through the UART port after completing data collection. The linear voltage regulator module is composed of a linear voltage regulator, including a power supply port VCC2, a voltage regulation control port SET, and a voltage regulation 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 regulation control port SET is connected to R5 to realize the selection of the voltage regulation value, and the value of the voltage regulation output OUT3 is controlled by the resistor R5; OUT3 is responsible for outputting the regulated voltage to the analog switch; The analog switch module is mainly composed of a two-choice analog switch, including a power port VCC3, a voltage regulator 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 after the sensor completes data transmission, the MCU outputs a high level to turn on the analog switch; the voltage regulator input port IN3 is connected to the output port OUT3 of the linear voltage regulator module to receive the voltage-regulated signal; 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 sensor 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 regulator input port IN3, i.e., the voltage regulator signal, is directly output to the tunnel diode, and when the level is low, the GND low level is output, thereby outputting a bias voltage containing sensor information to the tunnel diode.

Images