Self-powered wireless sensing and communication device based on radio frequency energy capture

Abstract

The invention discloses a self-powered wireless sensing and communication device based on radio frequency energy capture, and the device achieves the functions of capturing radio frequency energy and a sensor through a double-layer microstrip patch antenna, and achieves the functions of capturing radio frequency energy and wireless communication through a double-frequency microstrip patch antenna. An upper-layer antenna of the double-layer microstrip patch antenna forms the top surface of the shell; the four side surfaces of the shell are formed by the double-frequency microstrip patch antennas and are fixedly connected to the periphery of the upper-layer antenna; the antenna supporting frame forms the bottom surface of the shell and can be limited in the shell in a sliding manner; the transition circuit is used for integrating the captured radio frequency energy to the radio frequency rectification circuit; the radio frequency rectifying circuit is used for converting radio frequency energy into direct current; the energy storage device is used for storing electric energy and supplying the electric energy to the control module. The device can efficiently capture radio frequency energy in all directions, monitor the change of physical quantity in the environment, and realize the integration of radio frequency energy capture and wireless communication.

Description

Technical Field

[0001] The present invention belongs to the technical field of Internet of Things, and in particular relates to a self-powered wireless sensing and communication device based on radio frequency energy capture. Background Art

[0002] With the continuous development of Internet of Things (IoT) technology, the demand for wireless sensor networks (WSN) in smart homes, smart factories, smart transportation and other fields is growing. While IoT devices are widely used, they also face huge challenges in energy supply. Traditional wireless sensors usually rely on batteries, which not only increases maintenance costs, but also restricts the long-term use and environmental sustainability of the equipment. Therefore, the development of wireless smart sensor devices with self-powered functions has become a hot research topic, and radio frequency (RF) energy harvesting technology is an ideal solution.

[0003] RF energy capture technology captures RF energy in the environment (such as Wi-Fi, Bluetooth, mobile communication signals, etc.) and converts it into direct current to provide energy for low-power devices. However, existing RF energy capture devices mostly rely on a single functional module, which has the limitation that energy collection, sensing, and communication functions are independent of each other.

[0004] In terms of sensing technology, the patch antenna itself can be used as a sensor with high integration and miniaturization, and its application prospects in the field of the Internet of Things are broad. Patch antennas can not only effectively capture radio frequency signals, but also be used as sensors to monitor environmental changes, especially through changes in the antenna's resonant frequency to sense changes in physical quantities such as temperature, humidity, gas concentration, vibration displacement, stress and strain. Since the resonant frequency of the patch antenna is very sensitive to changes in the environment, it has a unique advantage in wireless sensing.

[0005] However, the current research on combining RF energy capture and sensing functions in the same antenna system is not in-depth enough, especially how to achieve the multifunctional integration of patch antennas to simultaneously undertake the tasks of energy capture, environmental perception and information communication is still a technical difficulty. Most of the existing technologies focus on RF energy capture or a single sensing function, especially in the unified design of physical structure and functional modules, and have not yet achieved high integration and high efficiency. Summary of the invention

[0006] The present invention provides a self-powered wireless sensing and communication device based on radio frequency energy capture. The self-powered wireless sensing and communication device can efficiently and omnidirectionally capture radio frequency energy through a dual-frequency microstrip patch antenna and a double-layer microstrip patch antenna, monitor changes in physical quantities in the environment, and realize the integrated integration of radio frequency energy capture and wireless communication through time division multiplexing.

[0007] In order to achieve the above object, the present invention adopts the following specific technical solutions: A self-powered wireless sensing and communication device based on radio frequency energy capture, the self-powered wireless sensing and communication device comprising a housing, a dual-frequency microstrip patch antenna, a double-layer microstrip patch antenna, an antenna support frame, a transition circuit, a radio frequency switch, a radio frequency rectification circuit, an energy storage device and a control module; The shell is a hollow cubic structure; the double-layer microstrip patch antenna includes an upper antenna and a lower antenna that are completely separated and have an air gap, and are used to realize the function of capturing radio frequency energy and sensors; the upper antenna forms the top surface of the shell; the lower antenna is supported at the bottom end of the upper antenna through the antenna support frame; the four sides of the shell are formed by the dual-frequency microstrip patch antenna and are fixedly connected to the four sides of the upper antenna; the antenna support frame forms the bottom surface of the shell and can be slidably limited between the four sides of the shell in the vertical direction to change the height of the air gap; the dual-frequency microstrip patch antenna is used to realize the function of capturing radio frequency energy and wireless communication; the lower antenna and the dual-frequency microstrip patch antenna are both coaxially fed by back-feeding and are connected to the radio frequency rectification circuit; The transition circuit, the RF switch, the RF rectification circuit, the energy storage device and the control module are all located in the shell and fixedly mounted on the antenna support frame; the transition circuit is used to integrate the RF energy captured by the double-layer microstrip patch antenna and the dual-frequency microstrip patch antenna into the RF rectification circuit; the RF rectification circuit is used to convert the RF energy into direct current; the energy storage device is used to store the electric energy converted by the RF rectification circuit and supply the electric energy to the control module to realize self-powered operation; the control module controls the RF switch to realize the function switching of the dual-frequency microstrip patch antenna, and realizes RF energy capture and wireless communication in different time periods.

[0008] Furthermore, the dual-frequency microstrip patch antenna includes a radiating patch, a first dielectric substrate, a first metal ground layer and a first coaxial probe feeding structure; the radiating patch is formed on the outer side of the first dielectric substrate; the first metal ground layer is formed on the inner side of the first dielectric substrate; the first coaxial probe feeding structure is composed of an SMA adapter welded to the radiating patch, the first metal ground layer and the first coaxial feeding through hole of the first dielectric substrate, which is used to achieve resonance in different frequency bands so that the dual-frequency microstrip patch antenna operates in dual frequency bands.

[0009] Furthermore, the radiation patch and the first metal grounding layer are formed on the first dielectric substrate by deposition of metal copper; the radiation patch is subjected to anti-oxidation treatment by tin plating; the inner surface of the first metal grounding layer is provided with a solder resist layer for increasing isolation; the radiation patch and the first metal grounding layer are both rectangular, and the length and width of the radiation patch are both smaller than the first dielectric substrate; the first metal grounding layer covers the inner side surface of the first dielectric substrate; and the first dielectric substrate is made of high-strength insulating material.

[0010] Furthermore, the upper antenna is a parasitic patch antenna; the lower antenna is a main patch antenna; The parasitic patch antenna is fed by electromagnetic coupling.

[0011] Furthermore, the parasitic patch antenna includes a second dielectric substrate and a parasitic patch formed on a top surface of the second dielectric substrate; The parasitic patch serves as a parasitic coupling unit, increases the bandwidth of the antenna through electromagnetic coupling, and improves the overall radiation efficiency of the antenna; the shape of the parasitic patch is rectangular or circular.

[0012] Furthermore, the main patch antenna includes a main radiation patch, a third dielectric substrate, a second metal ground layer, and a second coaxial probe feeding structure; The main radiation patch is formed on the top surface of the third dielectric substrate; The second metal grounding layer is formed on the bottom surface of the third dielectric substrate; The second coaxial probe feeding structure is fixedly mounted on the main radiation patch, the third dielectric substrate and the second metal grounding layer; When the main patch antenna is electromagnetically excited, the induced electromagnetic field will excite surface current and generate resonance.

[0013] Furthermore, when the double-layer microstrip patch antenna is used as a sensor, changes in physical quantities in the environment cause changes in the height of the air gap, which causes changes in the antenna resonant frequency, resulting in changes in the efficiency of the RF rectifier circuit, thereby realizing monitoring of physical quantities in the environment.

[0014] Furthermore, the antenna support frame consists of a base plate and four support columns, and is made of a low dielectric constant, smooth and insulating material; the base plate forms the bottom surface of the shell, and can be slidably limited in the vertical direction between the four dual-band microstrip patch antennas; the bottom end of the support column is fixedly installed on the top surface of the base plate, and the top end is supported on the bottom surface of the lower antenna.

[0015] Furthermore, the transition circuit is a 4:1 type power divider connected by equal-length coaxial lines, having four first input ports and one first output port, each first input port is connected to one of the dual-band microstrip patch antennas, and the first output port is connected to the radio frequency switch; The RF switch has one second input port and two second output ports; the second input port is connected to the output end of the transition circuit, one second output port is connected to the RF rectifier circuit, and the other second output port is connected to the control module.

[0016] Furthermore, the radio frequency rectification circuit includes an impedance matching circuit and a voltage doubling rectification circuit; The energy storage device is a supercapacitor; The control module samples the DC output voltage of the radio frequency rectification circuit, calculates the rectification efficiency, and transmits the information to the dual-frequency microstrip patch antenna through data encoding; The control module controls the radio frequency switch in a time-division multiplexing manner to achieve switching between radio frequency energy capture and wireless communication functions.

[0017] Compared with the prior art, the technical solution of the present invention has the following beneficial effects: 1. The self-powered wireless sensing and communication device of the present invention is based on RF energy capture technology, and antennas are arranged in the X, Y, and Z directions respectively, so that the RF energy of different frequency bands widely existing in the free space can be captured omnidirectionally, and the capture efficiency and availability of RF energy can be improved, and power support can be provided for the control module and the antenna, and the maintenance cost of the wireless sensor node and the need for battery replacement can be reduced, thereby realizing the self-powered operation of the sensor node.

[0018] 2. The double-layer microstrip patch antenna on the top of the shell extends the bandwidth and improves the antenna gain on the basis of the traditional microstrip patch antenna. The double-layer microstrip patch antenna is divided into two layers, the upper antenna is a parasitic patch antenna, and the lower antenna is a main patch antenna. The parasitic patch antenna is placed above the main patch antenna. Due to the coupling of the electromagnetic field, an induced current will be excited on the parasitic patch to form a new resonance mode, which is equivalent to connecting multiple resonant loops in parallel in the equivalent circuit model of the antenna, thereby expanding the working bandwidth of the antenna. The presence of the parasitic patch is equivalent to increasing the radiation surface area, increasing the equivalent aperture of the antenna, and improving the gain. At the same time, the presence of the air gap effectively reduces the dielectric loss, improves the radiation efficiency, and thus improves the antenna gain. The above-mentioned parasitic patch coupling design is used to reduce physical connections, and the height of the air gap can be flexibly adjusted, avoiding problems such as poor contact and wear that may occur in the traditional coaxial feeding method. Therefore, the design of the double-layer microstrip patch antenna can enhance the capture effect of RF energy in the corresponding frequency band.

[0019] 3. The double-layer microstrip patch antenna on the top of the shell can also work as a sensor while capturing RF energy. When the entire device is placed on the monitored object, when the changes in physical quantities in the environment (such as pressure, stress strain, vibration displacement, etc.) are transmitted to the bottom of the device (i.e., the bottom plate of the antenna support frame), the air gap height between the double-layer microstrip patch antennas will change, resulting in changes in the antenna resonant frequency, which in turn affects the rectification efficiency of the entire device. By recording and monitoring changes in rectification efficiency, the changes in the corresponding physical quantities can be inferred without the need for additional independent sensors, reducing the size of the device and achieving a highly integrated sensing function.

[0020] 4. The four dual-frequency microstrip patch antennas arranged on the side of the shell can realize RF energy capture and wireless communication at the same time. By finding a suitable feeding point on a single-layer patch, the antenna can operate in two frequency ranges, improving the efficiency of RF energy capture. At the same time, the RF switch is controlled in a time-division multiplexing manner, so that the dual-frequency microstrip patch antenna can work in two modes, RF energy capture and wireless communication. The four dual-frequency microstrip patch antennas arranged orthogonally in the X and Y directions provide good omnidirectional coverage, reduce dependence on the incident direction, and improve the stability of RF energy capture and wireless communication. This design improves the versatility and system integration of the equipment, simplifies the circuit structure, reduces the system complexity, and realizes the self-powered operation of the wireless sensor node.

[0021] 5. The present invention combines RF energy capture, wireless sensing and communication technologies to achieve self-powered operation of wireless sensor nodes in the Internet of Things environment. The realization of the antenna sensing function does not rely on the expensive vector network analyzer in traditional technology, but combines RF energy capture technology to monitor the rectification efficiency of the rectifier circuit, thereby realizing the monitoring and sensing of physical quantities in the environment, greatly reducing the cost and complexity of the sensing system. In addition, the device adopts a time-division multiplexing control method, which can switch between RF energy capture and wireless communication, and flexibly allocate energy flow through RF switches and power dividers to achieve efficient energy management and communication functions. The invention does not require external power supply, has the advantages of miniaturization, low power consumption, long life, and high integration. It is particularly suitable for the Internet of Things fields such as smart homes and smart factories, and provides an integrated solution for self-powered wireless sensing and communication. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of the external overall structure of the self-powered wireless sensing and communication device of the present invention.

[0023] Figure 2 It is a schematic diagram of the exploded structure of the self-powered wireless sensing and communication device of the present invention.

[0024] Figure 3 Schematic diagram of the exploded structure of the dual-band microstrip patch antenna.

[0025] Figure 4 Schematic diagram of the exploded structure of the double-layer microstrip patch antenna.

[0026] Figure 5 Schematic diagram of the assembly structure of the antenna support frame and the double-layer microstrip patch antenna.

[0027] Figure 6 This is a block diagram of the working principle of the self-powered wireless sensing and communication device of the present invention.

[0028] Figure numerals: 1-first dielectric substrate, 2-radiation patch, 3-first coaxial feed hole, 4-parasitic patch, 5-second dielectric substrate, 6-main radiation patch, 7-third dielectric substrate, 8-second metal grounding layer, 9-second coaxial feed hole, 10-support column, 11-bottom plate, 12-transition circuit, 13-RF switch, 14-RF rectification circuit, 15-control module, 16-energy storage device, 17-SMA adapter, 18-first metal grounding layer. DETAILED DESCRIPTION

[0029] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] like Figure 1 , Figure 2 and Figure 6 As shown, this embodiment provides a self-powered wireless sensing and communication device based on radio frequency energy capture, the self-powered wireless sensing and communication device includes a housing, a dual-frequency microstrip patch antenna, a double-layer microstrip patch antenna, an antenna support frame, a transition circuit 12, a radio frequency switch 13, a radio frequency rectification circuit 14, an energy storage device 16 and a control module 15; wherein: The shell is a hollow cubic structure, which is not only used to support and protect the internal electronic components, but also serves as the dielectric substrate of the antenna. The specific size is optimized according to the application requirements. The transition circuit 12, the RF switch 13, the RF rectification circuit 14, the energy storage device 16 and the control module 15 are all installed in the shell. The shell can be composed of a double-layer microstrip patch antenna constituting the top surface, a dual-frequency microstrip patch antenna constituting the surrounding sides and an antenna support frame constituting the bottom surface, or it can be composed of a cubic frame. When a cubic frame is used, the double-layer microstrip patch antenna is embedded in the top of the frame, the dual-frequency microstrip patch antenna is embedded in the surroundings of the frame, and the antenna support frame can be slidably embedded in the bottom along the vertical direction. In this embodiment, an example is taken in which the top surface of the shell is composed of a double-layer microstrip patch antenna, the four sides of the shell are composed of four dual-frequency microstrip patch antennas, and the bottom surface of the shell is composed of a base plate 11 of an antenna support frame; the four dual-frequency microstrip patch antennas are respectively fixed on the four sides of the shell in the orthogonal directions of X and Y, and the four dual-frequency microstrip patch antennas all adopt the same structure and design; the dual-frequency microstrip patch antenna and the double-layer microstrip patch antenna both adopt coaxial feeding, and both use SMA adapters 17 of the same specifications, and there are five SMA adapters 17 in total.

[0031] The double-layer microstrip patch antenna includes an upper antenna and a lower antenna. The upper antenna is located on top of the lower antenna. The upper antenna is completely separated from the lower antenna and has an air gap of a predetermined height for realizing the function of capturing radio frequency energy and sensors. The upper antenna forms the top surface of the shell.

[0032] The four sides of the shell are formed by dual-frequency microstrip patch antennas and are fixedly connected to the four sides of the upper antenna; the dual-frequency microstrip patch antenna is used to realize the functions of capturing radio frequency energy and wireless communication; the lower antenna and the dual-frequency microstrip patch antenna are both coaxially fed by back feeding and are connected to the radio frequency rectification circuit 14; the antenna support frame forms the bottom surface of the shell and can be slidably limited in the vertical direction between the four sides of the shell, which is used to support the lower antenna and change the height of the air gap.

[0033] The transition circuit 12, the RF switch 13, the RF rectification circuit 14, the energy storage device 16 and the control module 15 are all located in the housing and fixedly mounted on the bottom surface of the housing, that is, fixedly mounted on the top surface of the bottom plate 11. The transition circuit 12 is used to integrate the RF energy captured by the double-layer microstrip patch antenna and the dual-frequency microstrip patch antenna into the RF rectification circuit 14; the RF rectification circuit 14 is used to convert the RF energy into direct current, and the RF rectification circuit 14 includes an impedance matching circuit and a voltage doubling rectification circuit, both of which adopt a microstrip line transmission mode; the impedance matching part realizes the conjugate matching of the input and output impedances, thereby reducing the loss of RF power; the rectification part adopts a circuit structure of voltage doubling rectification, thereby increasing the output voltage, which is suitable for low-power input conditions. In the process of designing the RF rectification circuit 14, a circuit topology suitable for different input powers can be designed for different application scenarios, and a low forward voltage drop and high-efficiency Schottky diode can be selected, such as the SMS7630 series and the HSMS286x series. Preferably, a filter circuit may be provided after the RF rectifier circuit 14 to smooth the rectified DC output, reduce ripples, and provide a stable DC power supply for the subsequent energy storage device 16 .

[0034] The energy storage device 16 is used to store the DC power converted by the RF rectification circuit 14 and supply the power to the control module 15 to achieve self-powered operation; the energy storage device 16 can be a supercapacitor.

[0035] The control module 15 controls the RF switch 13 to switch the functions of the dual-frequency microstrip patch antenna, and realizes RF energy capture and wireless communication in different time periods. The RF switch 13 needs to cover the frequency range of the dual-frequency microstrip patch antenna, and because the RF energy capture system is sensitive to power loss, a device with low insertion loss should be selected, and a high degree of isolation should be ensured between signal paths to ensure that the energy capture mode and the communication mode do not affect each other. The RF switch 13 can select a FET switch (MOSFET or pHEMT), such as SKY13350-385LF (0.3 dB insertion loss, 37 dB isolation), HMC544A (0.6 dB insertion loss, 34dB isolation, DC-8GHz applicable) or Peregrine PE4259 (0.4 dB insertion loss, 42 dB isolation, low power CMOS process) and other models.

[0036] The control module 15 samples the DC output voltage of the RF rectification circuit 14, calculates the rectification efficiency, and transmits the information to the dual-frequency microstrip patch antenna through data encoding; the control module 15 controls the RF switch 13 in a time-division multiplexing manner to realize the switching of the two functions of RF energy capture and wireless communication. In the process of encoding and modulating the data and realizing wireless transmission, the control module 15 can adopt the modulation mode of FSK (frequency shift keying) or QPSK (quadrature phase shift keying), and the control module 15 can use a low-power MCU (such as STM32L431) or a dedicated low-power RF chip (such as nRF24L01, CC2500, etc.).

[0037] like Figure 3 As shown, the dual-frequency microstrip patch antenna includes a radiation patch 2, a first dielectric substrate 1, a first metal grounding layer 18 and a first coaxial probe feeding structure; the radiation patch 2 is formed on the outer side of the first dielectric substrate 1, arranged in a rectangular shape, and the length and width generally satisfy the half-wavelength resonance; the first metal grounding layer 18 is formed on the inner side of the first dielectric substrate 1; the first coaxial probe feeding structure is composed of an SMA adapter 17 welded to the radiation patch 2, the first metal grounding layer 18 and the first coaxial feeding through hole 3 of the first dielectric substrate 1, which is used to achieve resonance in different frequency bands so that the dual-frequency microstrip patch antenna can operate in dual frequency bands. The radiation patch 2 and the first metal grounding layer 18 can be formed on the first dielectric substrate 1 by depositing metal copper through the PCB process, and the feeding point is selected at a suitable position according to the frequency band requirements and the impedance size of 50Ω, so as to realize the dual-band working mode of the antenna, so that the antenna can capture radio frequency energy of different frequency bands and improve the capture efficiency of radio frequency energy; the radiation patch 2 is tinned for anti-oxidation treatment; the inner surface of the first metal grounding layer 18 is provided with a solder mask layer for increasing isolation to prevent the first metal grounding layer 18 from affecting the electrical performance of the internal circuit of the shell; the radiation patch 2 and the first metal grounding layer 18 are both rectangular, and the length and width of the radiation patch 2 are both smaller than the first dielectric substrate 1; the first metal grounding layer 18 covers the inner side of the first dielectric substrate 1. The first dielectric substrate 1 is made of high-strength insulating material. After the dual-band microstrip patch antenna is manufactured, the first coaxial feeding through hole 3 is punched at the selected feeding point, and the SMA adapter 17 is used for welding, thereby completing the manufacture of the dual-band microstrip patch antenna.

[0038] like Figure 2 , Figure 4 and Figure 5As shown, the upper antenna is a parasitic patch 4 antenna; the lower antenna is a main patch antenna; the parasitic patch 4 antenna is fed by electromagnetic coupling. The parasitic patch 4 antenna includes a second dielectric substrate 5 and a parasitic patch 4 formed on the top surface of the second dielectric substrate 5; the parasitic patch 4 is a parasitic coupling unit, which increases the bandwidth of the antenna through electromagnetic coupling and improves the overall radiation efficiency of the antenna; the shape of the parasitic patch 4 is rectangular or circular, and the rectangle is used as an example for explanation in this embodiment. The main patch antenna includes a main radiating patch 6, a third dielectric substrate 7, a second metal grounding layer 8 and a second coaxial probe feeding structure; the main radiating patch 6 is formed on the top surface of the third dielectric substrate 7, and the second metal grounding layer 8 is formed on the bottom surface of the third dielectric substrate 7; corresponding second coaxial feeding through holes 9 are provided on the main radiating patch 6, the third dielectric substrate 7 and the second metal grounding layer 8, and the second coaxial probe feeding structure is fixedly mounted on the main radiating patch 6, the third dielectric substrate 7 and the second metal grounding layer 8 through the second coaxial feeding through hole 9. After the main patch antenna is electromagnetically excited, the induced electromagnetic field will excite the surface current and generate resonance. The manufacturing process of the main patch antenna is similar to that of the dual-band microstrip patch antenna, and the PCB process flow is also adopted. The size of the main radiation patch 6 and the position of the second coaxial feed through hole 9 are related to the working frequency band of the double-layer microstrip patch antenna. The lower main patch antenna is bonded to four antenna support columns 10 and supported by the antenna support frame. The parasitic patch 4 of the upper antenna is slightly smaller than the main radiation patch 6 of the lower antenna, and the second dielectric substrate 5 of the upper antenna and the shell can be made of the same material. The parasitic patch 4 of the upper antenna is suspended above the main patch antenna of the lower antenna, and an air gap of height h is formed between the two. The transmission of radio frequency power is achieved between the upper and lower antennas through the effect of electromagnetic coupling.

[0039] When the double-layer microstrip patch antenna is used as a sensor, when the change of physical quantities in the environment (such as pressure, stress strain, vibration displacement, etc.) causes the height h of the air gap to change, the resonant frequency of the antenna will change. At this time, if the power of the RF energy input by the external environment is constant, the RF energy received by the double-layer microstrip patch antenna will decrease, which will lead to a decrease in the rectification efficiency of the subsequent RF rectification circuit 14. By monitoring the change of the rectification efficiency through the control module 15, the change of the physical quantity of the external environment can be monitored, thereby playing the role of antenna sensing, thereby realizing the monitoring of the physical quantity in the environment.

[0040] like Figure 2 and Figure 5As shown, the antenna support frame is composed of a base plate 11 and four support columns 10, and is made of a low dielectric constant, smooth and insulating material, such as polytetrafluoroethylene Teflon; the base plate 11 forms the bottom surface of the shell, and can be slidably limited between four dual-frequency microstrip patch antennas in the vertical direction; the bottom end of the support column 10 is fixedly mounted on the top surface of the base plate 11, and the top end is supported on the bottom surface of the lower antenna. The four support columns 10 are vertically fixed to the upper surface of the base plate 11, while ensuring a certain mechanical stability. The antenna support frame and the lower antenna can slide smoothly synchronously, thereby changing the height h of the air gap to achieve the sensing function.

[0041] The above-mentioned transition circuit 12 is a 4:1 type Wilkinson power divider connected by equal-length coaxial lines. Based on the principle of quarter-wavelength impedance transformation, it has four equal-power first input ports and one first output port, and the output end is designed to have a standard impedance of 50Ω to achieve low-loss transmission of RF power; each first input port is connected to a dual-band microstrip patch antenna for integrating RF energy captured by different antennas; the first output port is connected to the RF switch 13; the RF switch 13 has one second input port and two second output ports; the second input port is connected to the output end of the transition circuit 12, one of the second output ports is connected to the RF rectifier circuit 14, and the other second output port is connected to the control module 15.

[0042] The first dielectric substrate 1, the second dielectric substrate 5, the third dielectric substrate 7 and the bottom plate 11 are all made of low-loss dielectric materials to ensure efficient electromagnetic performance when used as antenna substrates, and have sufficient mechanical strength to protect the internal circuits. They can also be made of high-strength insulating materials. The dielectric substrate and the bottom plate 11 constituting the shell can be made of FR4 material (dielectric constant 4.4, loss tangent 0.02) or Rogers series high-frequency boards, such as RO4350B (dielectric constant 3.48, loss tangent 0.0037) and RT5880 (dielectric constant 2.2, loss tangent 0.0009).

[0043] The self-powered wireless sensor and communication device can realize the RF energy capture and wireless communication functions simultaneously. The RF switch 13 is set between the transition circuit 12 and the RF rectifier circuit 14. The control module 15 controls the RF switch 13 in a time-division multiplexing manner to ensure that the RF energy capture and data transmission are performed alternately to avoid mutual interference. Figure 6 As shown, most of the time, the RF switch 13 works in the energy capture mode; when the change of the environmental physical quantity causes the change of the rectification efficiency of the RF rectification circuit 14, the control module 15 samples the DC output voltage of the RF rectification circuit 14, encodes and modulates the data, and controls the RF switch 13 to switch to the communication mode, and transmits the processed digital signal to the dual-frequency microstrip patch antenna for transmission, thereby realizing the function of wireless communication.

[0044] Obviously, those skilled in the art can make various changes and modifications to the embodiments of the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A self-powered wireless sensing and communication device based on radio frequency energy capture, characterized in that: It includes a housing, a dual-frequency microstrip patch antenna, a double-layer microstrip patch antenna, an antenna support frame, a transition circuit, a radio frequency switch, a radio frequency rectification circuit, an energy storage device and a control module; The shell is a hollow cubic structure; the double-layer microstrip patch antenna includes an upper antenna and a lower antenna that are completely separated and have an air gap, and are used to realize the function of capturing radio frequency energy and sensors; the upper antenna forms the top surface of the shell; the lower antenna is supported at the bottom end of the upper antenna through the antenna support frame; the four sides of the shell are formed by the dual-frequency microstrip patch antenna and are fixedly connected to the four sides of the upper antenna; the antenna support frame forms the bottom surface of the shell and can be slidably limited between the four sides of the shell in the vertical direction to change the height of the air gap; the dual-frequency microstrip patch antenna is used to realize the function of capturing radio frequency energy and wireless communication; the lower antenna and the dual-frequency microstrip patch antenna are both coaxially fed by back-feeding and are connected to the radio frequency rectification circuit; The transition circuit, the RF switch, the RF rectification circuit, the energy storage device and the control module are all located in the shell and fixedly mounted on the antenna support frame; the transition circuit is used to integrate the RF energy captured by the double-layer microstrip patch antenna and the dual-frequency microstrip patch antenna into the RF rectification circuit; the RF rectification circuit is used to convert the RF energy into direct current; the energy storage device is used to store the electric energy converted by the RF rectification circuit and supply the electric energy to the control module to realize self-powered operation; the control module controls the RF switch to realize the function switching of the dual-frequency microstrip patch antenna, and realizes RF energy capture and wireless communication in different time periods.

2. The self-powered wireless sensing and communication device according to claim 1, characterized in that: The dual-frequency microstrip patch antenna includes a radiating patch, a first dielectric substrate, a first metal grounding layer and a first coaxial probe feeding structure; the radiating patch is formed on the outer side of the first dielectric substrate; the first metal grounding layer is formed on the inner side of the first dielectric substrate; the first coaxial probe feeding structure is composed of an SMA adapter welded to the radiating patch, the first metal grounding layer and the first coaxial feeding through hole of the first dielectric substrate, and is used to achieve resonance in different frequency bands so that the dual-frequency microstrip patch antenna operates in dual frequency bands.

3. The self-powered wireless sensing and communication device according to claim 2, characterized in that: The radiation patch and the first metal grounding layer are formed on the first dielectric substrate by deposition of metal copper; the radiation patch is subjected to anti-oxidation treatment by tin plating; the inner surface of the first metal grounding layer is provided with a solder resist layer for increasing isolation; the radiation patch and the first metal grounding layer are both rectangular, and the length and width of the radiation patch are both smaller than the first dielectric substrate; the first metal grounding layer covers the inner side surface of the first dielectric substrate; The first dielectric substrate is made of high-strength insulating material.

4. The self-powered wireless sensing and communication device according to claim 1, characterized in that: The upper antenna is a parasitic patch antenna; the lower antenna is a main patch antenna; The parasitic patch antenna is fed by electromagnetic coupling.

5. The self-powered wireless sensing and communication device according to claim 4, characterized in that: The parasitic patch antenna includes a second dielectric substrate and a parasitic patch formed on the top surface of the second dielectric substrate; The parasitic patch serves as a parasitic coupling unit, increases the bandwidth of the antenna through electromagnetic coupling, and improves the overall radiation efficiency of the antenna; the shape of the parasitic patch is rectangular or circular.

6. The self-powered wireless sensing and communication device according to claim 4, characterized in that: The main patch antenna includes a main radiation patch, a third dielectric substrate, a second metal ground layer and a second coaxial probe feeding structure; The main radiation patch is formed on the top surface of the third dielectric substrate; The second metal grounding layer is formed on the bottom surface of the third dielectric substrate; The second coaxial probe feeding structure is fixedly mounted on the main radiation patch, the third dielectric substrate and the second metal grounding layer; When the main patch antenna is electromagnetically excited, the induced electromagnetic field will excite surface current and generate resonance.

7. The self-powered wireless sensing and communication device according to claim 1, characterized in that: When the double-layer microstrip patch antenna is used as a sensor, changes in physical quantities in the environment cause changes in the height of the air gap, which causes changes in the antenna resonant frequency, resulting in changes in the efficiency of the radio frequency rectification circuit, thereby realizing monitoring of physical quantities in the environment.

8. The self-powered wireless sensing and communication device according to any one of claims 1 to 7, characterized in that: The antenna support frame consists of a base plate and four support columns, and is made of a low dielectric constant, smooth and insulating material; the base plate forms the bottom surface of the shell, and can be slidably limited in the vertical direction between the four dual-band microstrip patch antennas; the bottom end of the support column is fixedly installed on the top surface of the base plate, and the top end is supported on the bottom surface of the lower antenna.

9. The self-powered wireless sensing and communication device according to any one of claims 1 to 7, characterized in that: The transition circuit is a 4:1 type power divider connected by equal-length coaxial lines, having four first input ports and one first output port, each first input port is connected to one of the dual-frequency microstrip patch antennas, and the first output port is connected to the radio frequency switch; The RF switch has one second input port and two second output ports; the second input port is connected to the output end of the transition circuit, one second output port is connected to the RF rectifier circuit, and the other second output port is connected to the control module.

10. The self-powered wireless sensing and communication device according to claim 9, characterized in that: The radio frequency rectification circuit includes an impedance matching circuit and a voltage doubling rectification circuit; The energy storage device is a supercapacitor; The control module samples the DC output voltage of the radio frequency rectification circuit, calculates the rectification efficiency, and transmits the information to the dual-frequency microstrip patch antenna through data encoding; The control module controls the radio frequency switch in a time-division multiplexing manner to achieve switching between radio frequency energy capture and wireless communication functions.

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