A metasurface-based band reconfigurable radio frequency energy harvester unit

Abstract

This invention discloses a band-reconfigurable radio frequency energy harvester unit based on metasurfaces, comprising a first dielectric substrate and a second dielectric substrate, with an air layer between them; a top-layer metal structure is disposed on the upper surface of the first dielectric substrate; a lower microstrip metal structure is disposed on the upper surface of the second dielectric substrate, and a bottom-layer ground metal layer is disposed on the lower surface of the second dielectric substrate; the top-layer metal structure and the lower microstrip metal structure are connected by a conductive metal pillar structure; a metallized via is also disposed in the middle of the second dielectric substrate, penetrating the second dielectric substrate and the bottom-layer ground metal layer. This invention enables the radio frequency energy harvester unit to cover the environmental radio frequency resources as much as possible, improving its radio frequency resource utilization per unit area, enhancing its practicality and robustness, while also having a compact design that meets the self-powering requirements of wireless sensor networks.

Description

Technical Field

[0001] This invention relates to the field of radio frequency energy harvesting, and in particular to a band-reconfigurable radio frequency energy harvester unit based on metasurfaces. Background Technology

[0002] In recent years, the emergence of concepts such as 5G communication and the Internet of Things, along with the gradual reduction in the power consumption of electronic components, has driven the development of various low-power wireless sensors. Wireless sensors can communicate with each other and collect different data, such as temperature, pressure, and humidity, and are widely used in various scenarios. Currently, most sensors are powered by batteries. Although significant progress has been made in micro-battery research, battery life is limited, replacement costs are high, and environmental pollution caused by discarded batteries is a significant problem. Therefore, researchers have begun to explore harvesting energy from the environment surrounding wireless sensors to power them. Radio frequency (RF) energy harvesting technology is a technique that harvests energy from radio frequency radiation emitted by environmental radio frequency signal sources (such as WiFi, cellular networks, and broadcast television systems) to power low-power sensors, and it has become a hot topic in micro-energy harvesting research in recent years. Unlike most energy sources (such as heat, mechanical vibration energy, and light energy), RF energy is ubiquitous in our daily lives, continuously available, and not easily affected by natural factors such as temperature, rain, and fog. Therefore, RF energy harvesting technology holds the promise of reducing the need for battery replacement or charging for the billions of micro-wireless sensors in wireless sensor networks.

[0003] A typical radio frequency (RF) energy harvesting system mainly includes an RF energy harvesting front-end that collects ambient electromagnetic energy, an impedance matching network between the RF energy harvesting front-end and the rectifier circuit, the rectifier circuit, a boost converter circuit, and an energy storage module. Among these, the RF energy harvesting front-end is the key component determining the performance of the RF energy harvesting system. Because the power density of harvestable RF energy in the environment is low, the spectrum distribution is relatively dispersed, and the direction of arrival and polarization state of ambient RF energy are uncertain, the RF energy harvesting front-end must possess characteristics such as high conversion efficiency, wide bandwidth / multi-frequency operation, wide incident angle, and polarization insensitivity. In recent years, researchers have proposed two main types of RF energy harvesting front-ends: one is a rectifier antenna composed of traditional antennas, and the other is a metasurface energy harvester based on subwavelength electromagnetic metamaterial units or arrays. Traditional rectifier antennas, because their size is comparable to the operating wavelength, suffer from large size and a single operating frequency band. In contrast, metasurface-based RF energy harvesters generally possess compact, miniaturized, and rotationally symmetric structural characteristics and multimode resonance effects. Compared to traditional rectifier antennas, they have higher harvesting efficiency per unit area, making them more suitable for integrated applications of RF energy harvesting systems and offering significant advantages. However, existing metasurface radio frequency energy harvesters generally suffer from a limited number of receivable frequency bands, are scattered, and have narrow bandwidths in each operating frequency band. On the one hand, with the development and commercial deployment of technologies such as 5G and 6G, the frequency bands of available radio frequency resources in the environment are gradually increasing (such as 1.8GHz, 2.1GHz, 2.6GHz, and 3.5GHz), while existing radio frequency energy harvesters are mainly concentrated on a few common ISM frequencies such as 900MHz, 2.45GHz, and 5.85Hz, making it difficult to fully cover the available radio frequency resources in the environment. On the other hand, existing metasurface radio frequency energy harvesters generally have narrow operating bandwidths at their operating frequencies, making them prone to frequency deviation and failure when faced with processing errors and environmental disturbances (such as rust and rain), resulting in poor robustness.In 2020, Fan Yu et al. proposed a metasurface energy harvesting unit based on a rotationally centrosymmetric bowtie structure in their paper "Polarization-insensitive wide-angle-reception metasurface with simplified structure for harvesting electromagnetic energy". This unit features polarization insensitivity and a wide incident angle, and uses only one lumped port. It achieves a maximum harvesting efficiency of 88% at the center frequency of 5.8 GHz. However, this design can only operate at a single frequency. In 2017, Xuan-Ming Zhang et al. proposed a tri-band (0.9 GHz, 2.6 GHz, 5.7 GHz) metasurface energy harvesting unit based on a butterfly-shaped closed-loop structure in their paper "Tri-band miniaturized wide-angle and polarization-insensitive metasurface for ambient energy harvesting". This unit also features polarization insensitivity and a wide incident angle, and uses only one lumped port. However, this design still has a limited number of operating frequencies and an extremely narrow operating bandwidth at each frequency. In addition, the load impedance of the lumped port is as high as 2776 ohms, which is not conducive to practical applications.

[0004] Furthermore, while some metasurface radio frequency energy harvester designs achieve multiple operating frequencies or wide operating bandwidths, they use more than one lumped port in each unit and do not consider subsequent power combining, increasing the difficulty and complexity of subsequent circuit design and system integration. In 2017, Hui-Teng Zhong et al. proposed a wideband metasurface energy harvesting array in their paper "Wideband metamaterial array with polarization-independent and wide incident angle for harvesting ambient electromagnetic energy and wireless power transfer". The array unit consists of a square closed loop and four metal arms, achieving 110% half-power bandwidth in the 6.2 GHz to 21.4 GHz band. However, each unit uses four lumped ports, greatly increasing the complexity of subsequent system integration.

[0005] Therefore, there is an urgent need to design a metasurface RF energy harvesting unit with a wide operating bandwidth and a single load port to cover as many environmental RF resource frequencies as possible, improve its RF resource utilization per unit area, and enhance its practicality and robustness. This is of great significance for promoting the development of wireless sensor networks. Summary of the Invention

[0006] The purpose of this invention is to provide a band-reconfigurable radio frequency energy harvester unit based on metasurfaces. This invention reconfigures the operating frequency bands of the radio frequency energy harvester unit to cover the environmental radio frequency resources as much as possible, thereby improving its radio frequency resource utilization per unit area, enhancing its practicality and robustness. Simultaneously, the design is compact and meets the self-powering requirements of wireless sensor networks.

[0007] The technical solution of the present invention is as follows: A band-reconfigurable radio frequency energy harvester unit based on metasurfaces includes a first dielectric substrate and a second dielectric substrate, with an air layer between the first dielectric substrate and the second dielectric substrate; a top metal structure is disposed on the upper surface of the first dielectric substrate; a lower microstrip metal structure is disposed on the upper surface of the second dielectric substrate, and a bottom ground metal layer is disposed on the lower surface of the second dielectric substrate; the top metal structure and the lower microstrip metal structure are connected by a conductive metal pillar structure; a metallized via is also disposed in the middle of the second dielectric substrate, the metallized via penetrating the second dielectric substrate and the bottom ground metal layer.

[0008] In the aforementioned metasurface-based band-reconfigurable radio frequency energy harvester unit, the first dielectric substrate and the second dielectric substrate are both square substrates of the same size and aligned vertically; the top metal structure is aligned with the center of the first dielectric substrate and the second dielectric substrate.

[0009] The aforementioned metasurface-based band-reconfigurable radio frequency energy harvester unit includes a top-layer metal structure comprising four identical artificial localized surface plasmon resonance rings arranged symmetrically at the center, namely, a first resonance ring, a second resonance ring, a third resonance ring, and a fourth resonance ring; each artificial localized surface plasmon resonance ring includes an outer metal ring and toothed metal segments arranged periodically at fixed intervals, wherein one end of each periodic toothed metal segment is connected to the outer metal ring, and the extension line of the other end points to the center of the outer metal ring.

[0010] The aforementioned metasurface-based band-reconfigurable radio frequency energy harvester unit includes a conductive metal pillar structure comprising four centrally symmetrically arranged vertical conductive metal pillars, namely, a first conductive metal pillar, a second conductive metal pillar, a third conductive metal pillar, and a fourth conductive metal pillar; the top ends of the first, second, third, and fourth conductive metal pillars are respectively connected to the end of a toothed metal segment on the first, second, third, and fourth resonant rings.

[0011] The aforementioned metasurface-based band-reconfigurable radio frequency energy harvester unit includes a lower microstrip metal structure comprising a first microstrip line, a second microstrip line, a third microstrip line, a fourth microstrip line, a first impedance matching stub, a second impedance matching stub, a third impedance matching stub, and a fourth impedance matching stub. The first, second, third, and fourth microstrip lines are connected end-to-end sequentially, wherein the lengths of the first, second, and third microstrip lines are equal, and their linewidths increase sequentially. The beginnings of the first, second, third, and fourth impedance matching stubs are respectively connected to the ends of the first, second, third, and fourth microstrip lines. The ends of the first, second, third, and fourth impedance matching stubs are respectively connected to the bottoms of the first, second, third, and fourth conductive metal pillars.

[0012] In the aforementioned metasurface-based band-reconfigurable radio frequency energy harvester unit, the top end of the metallized via is connected to the beginning end of the fourth microstrip line; the bottom metal ground layer has a hole aligned with the center of the metallized via, and the hole and the bottom end of the metallized via constitute a wireless radio frequency energy harvesting port.

[0013] The aforementioned metasurface-based band-reconfigurable radio frequency energy harvester unit uses FR4 dielectric substrates with a dielectric constant of 4.3 and a loss tangent of 0.02 for both the first and second dielectric substrates. The thickness of the substrates is... and All are 0.4–1.5 mm; the thickness of the air layer It is 5-15mm.

[0014] In the aforementioned metasurface-based band-reconfigurable radio frequency energy harvester unit, the first resonant ring, the second resonant ring, the third resonant ring, and the fourth resonant ring do not overlap; in the periodic toothed metal segments, except for the segments connected to the conductive metal pillars, the remaining segments have the same length and do not overlap.

[0015] In the aforementioned metasurface-based band-reconfigurable radio frequency energy harvester unit, the first, second, and third microstrip lines are all annular rings with an opening angle of 270 degrees and the same radius, with their centers aligned with the center of the second dielectric substrate; the center of the metallized via is aligned with the center of the second dielectric substrate; and the first, second, third, and fourth impedance matching segments are all formed by connecting two segments of different widths in series.

[0016] In the aforementioned metasurface-based band-reconfigurable radio frequency energy harvester unit, the first conductive metal pillar, the second conductive metal pillar, the third conductive metal pillar, and the fourth conductive metal pillar are all solid copper pillars.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] 1. This invention reconstructs the operating frequency bands of different polarization directions, so that the operating frequency band of the radio frequency energy harvesting unit covers the environmental radio frequency resource band as much as possible, thereby improving the utilization rate of radio frequency resources per unit area, enhancing its practicality and robustness. At the same time, the design structure is compact and meets the self-powering requirements of wireless sensor networks.

[0019] 2. This invention uses four centrally rotationally symmetric artificial local surface plasmon resonance rings as the top-level resonator. The artificial local surface plasmon resonance ring is a subwavelength electromagnetic metamaterial unit with compact, miniaturized, and rotationally symmetric structural features and multimode resonance effect.

[0020] 3. In this invention, each resonant ring in the top layer is connected to the sequentially rotating microstrip structure below via a conductive metal pillar. When an electromagnetic wave with a specific polarization angle irradiates the surface of the unit, it excites the self-resonance of the specific resonant ring and the tight coupling effect between adjacent resonant rings. The surface current generated by the resonance flows to the lower microstrip structure through the conductive metal pillar, converges along a specific path, and is collected at the load impedance. The resonance effects and frequency bands excited by electromagnetic waves with different polarization directions are different. By rationally designing the resonant structure and the length of the lower microstrip path, the metasurface unit can flexibly receive electromagnetic waves of different frequency bands at different polarization angles, greatly expanding the environmental radio frequency resource frequency band that can be covered.

[0021] 4. This invention uses a sequentially rotating microstrip structure to gather the radio frequency energy collected by the upper resonant structure into the same lumped port, resulting in a compact layout. On the other hand, it has a certain degree of impedance matching effect, allowing the metasurface unit to use only one port with a load impedance of 50 ohms, which reduces costs, enhances practicality, and is beneficial for subsequent circuit design and system integration design. Attached Figure Description

[0022] Figure 1This is a side view of the radio frequency energy harvester unit of the present invention;

[0023] Figure 2 This is a top view of the radio frequency energy harvester unit of the present invention;

[0024] Figure 3 This is a schematic diagram of the lower-layer sequential rotating microstrip structure of the radio frequency energy harvester unit of the present invention;

[0025] Figure 4 The simulation results are for the radio frequency energy harvester unit of this invention.

[0026] Figure label:

[0027] 1. Top-layer metal structure; 2. First dielectric substrate; 3. Conductive metal pillar structure; 4. Lower-layer microstrip metal structure; 5. Second dielectric substrate; 6. Metallized via; 7. Bottom-layer metal grounding layer; 11. First resonant ring; 12. Second resonant ring; 13. Third resonant ring; 14. Fourth resonant ring; 31. First conductive metal pillar; 32. Second conductive metal pillar; 33. Third conductive metal pillar; 34. Fourth conductive metal pillar; 41. First microstrip line; 42. Second microstrip line; 43. Third microstrip line; 44. Fourth microstrip line; 45. First impedance matching branch; 46. Second impedance matching branch; 47. Third impedance matching branch; 48. Fourth impedance matching branch. Detailed Implementation

[0028] The present invention will be further described below with reference to the accompanying drawings and embodiments, but this should not be construed as limiting the present invention.

[0029] Example: A band-reconfigurable radio frequency energy harvester unit based on metasurfaces, see [link / reference]. Figure 1 The first dielectric substrate 2 and the second dielectric substrate 5 are provided with an air layer between them. A top metal structure 1 is provided on the upper surface of the first dielectric substrate 2. A lower microstrip metal structure 4 is provided on the upper surface of the second dielectric substrate 5, and a bottom ground metal layer 7 is provided on the lower surface of the second dielectric substrate 5. The top metal structure 1 and the lower microstrip metal structure 4 are connected by a conductive metal pillar structure 3. A metallized through-hole 6 is also provided in the middle of the second dielectric substrate 5, and the metallized through-hole 6 penetrates the second dielectric substrate 5 and the bottom ground metal layer 7.

[0030] Specifically, both the first dielectric substrate 2 and the second dielectric substrate 5 are square substrates of the same size, aligned vertically, and the thickness of the first dielectric substrate is... The thickness of the second dielectric substrate is 0.8 mm. =1mm, all using FR4 substrate with a dielectric constant of 4.3 and a loss tangent of 0.02. An air layer is provided between the first dielectric substrate 2 and the second dielectric substrate 5 to reduce the equivalent dielectric constant of the metasurface unit dielectric substrate, thereby improving bandwidth and collection efficiency. Its thickness is set to It is 13mm.

[0031] The conductive metal pillar structure 3 comprises four centrally symmetrically arranged vertical conductive metal pillars, namely the first conductive metal pillar 31, the second conductive metal pillar 32, the third conductive metal pillar 33, and the fourth conductive metal pillar 34, which penetrate the first dielectric substrate 2 and the air layer. They are all solid copper pillars with a radius of 0.5 mm. Their function is to conduct the surface current generated by the electromagnetic wave excitation of the top metal structure to the lower microstrip structure.

[0032] See Figure 2 The top-layer metal structure 1 comprises four identical artificial localized surface plasmon resonant rings arranged with central rotational symmetry, namely, the first resonant ring 11, the second resonant ring 12, the third resonant ring 13, and the fourth resonant ring 14 in a counterclockwise order, with the spacing between adjacent resonant rings... =2mm. The artificial localized surface plasmon resonance ring contains a width of =2mm, radius The system consists of a 4.7mm outer metal ring and 36 equally spaced, periodically arranged toothed metal segments. One end of each periodic toothed metal segment is connected to the outer metal ring, and the extension of the other end points towards the outer metal ring. Diagonally, each of the first resonant ring 11, second resonant ring 12, third resonant ring 13, and fourth resonant ring 14 has a toothed metal segment whose end is fixed to the top of the first conductive metal post 31, second conductive metal post 32, third conductive metal post 33, and fourth conductive metal post 34, respectively. The length of these four segments is determined by the position of the conductive metal posts. The remaining segments have equal lengths. =3.9mm. Distance between the outer perimeter of the resonant ring and the unit boundary. =4.5mm.

[0033] See attached document Figure 3 The lower microstrip metal structure 4 includes a first microstrip line 41, a second microstrip line 42, a third microstrip line 43, a fourth microstrip line 44, a first impedance matching branch 45, a second impedance matching branch 46, a third impedance matching branch 47, and a fourth impedance matching branch 48. The first microstrip line 41, the second microstrip line 42, the third microstrip line 43, and the fourth microstrip line 44 are connected end-to-end in sequence. The first microstrip line 41, the second microstrip line 42, and the third microstrip line 43 are all open circular rings with an opening angle of 270 degrees and the same radius, their centers aligned with the center of the second dielectric substrate 5. The linewidths increase sequentially. =0.2mm, =1.5mm, =1.8mm. The first impedance matching stub 45, the second impedance matching stub 46, the third impedance matching stub 47, and the fourth impedance matching stub 48 are respectively connected to the ends of the first microstrip line 41, the second microstrip line 42, the third microstrip line 43, and the fourth microstrip line 44. Their ends are respectively connected to the bottom ends of the first conductive metal pillar 31, the second conductive metal pillar 32, the third conductive metal pillar 33, and the fourth conductive metal pillar 34. Each stub is composed of two stubs of different widths connected in series. Its function is to achieve a certain degree of impedance matching by adjusting the line width and length, thereby reducing impedance mismatch loss during energy transmission. The metallized via 6 is located at the center of the second dielectric substrate 5, penetrating the second dielectric substrate 5 and the metal ground layer 7. Its top end is connected to the first end of the fourth microstrip line 44, and its bottom end is connected to the hole in the metal ground layer 7 to form a wireless radio frequency energy harvesting port. The impedance value of the terminated load is set to 50 ohms. In this invention, metal layers 1, 4 and 7 are all made of copper, and the copper coating thickness is 0.035 mm.

[0034] Through the above-described unit structure design, this invention can reconstruct a new frequency band near the original frequency band by horizontal rotation, thereby obtaining a wide operating frequency band: when an electromagnetic wave with a specific polarization angle is incident, the radio frequency energy received by the top-layer centrally symmetrical metasurface resonant structure can be transmitted to the load through a specific path. Different polarization angles correspond to different resonance effects and different path lengths. Therefore, the operating frequency band will shift to a new frequency band as the polarization angle of the incident wave changes. Furthermore, due to the gradually changing line impedance, the new frequency band can still have a collection efficiency comparable to the original frequency band. Therefore, for any frequency electromagnetic wave within a relatively wide frequency band, this invention can always collect it by horizontal rotation at a certain angle, and the optimal collection efficiency of each frequency band remains stable.

[0035] Finite element analysis (FEM) was performed on the radio frequency energy harvester unit in this embodiment using the commercial full-wave electromagnetic simulation software Ansoft HFSS. Periodic boundary conditions were used to simulate an infinitely large metasurface energy harvesting array. A Floquet port was placed at a certain distance directly above the unit as the excitation source to simulate plane electromagnetic wave incidence. The load port Port1 was set to a 50-ohm impedance. (See attached...) Figure 2 and attached Figure 3 Assume that the angle between the polarization direction of the incident electromagnetic wave's electric field and the clockwise direction of the x-axis is... Simulate respectively The radio frequency (RF) energy harvesting efficiency of an infinitely large periodic metasurface array at 0°, 45°, 90°, and 135°. RF energy harvesting efficiency refers to the percentage of incident electromagnetic wave power received by a resistive load, which can be expressed using scattering parameters. The simulation results are shown in the appendix. Figure 4 ,when The operating frequency band of this embodiment gradually shifts to higher frequencies with stable collection efficiency and bandwidth, gradually increasing from 0° to 135°. It can achieve a collection efficiency of over 50% in a wide frequency range of 1.68GHz to 2.7GHz, covering multiple mainstream environmental radio frequency resources such as 1.8GHz, 1.9GHz, 2.1GHz, 2.3GHz, 2.6GHz, and 2.7GHz. It is applicable to multiple indoor and outdoor scenarios, and is convenient to use and low in cost, thus having high practical value.

[0036] In summary, this invention reconstructs the operating frequency bands of different polarization directions, enabling the operating frequency band of the radio frequency energy harvesting unit to cover the environmental radio frequency resources as much as possible, thereby improving its radio frequency resource utilization per unit area, enhancing its practicality and robustness. At the same time, the design is compact and meets the self-powering requirements of wireless sensor networks.

Claims

1. A band-reconfigurable radio frequency energy harvester unit based on metasurfaces, characterized in that: The substrate includes a first dielectric substrate (2) and a second dielectric substrate (5), with an air layer between the first dielectric substrate (2) and the second dielectric substrate (5); a top metal structure (1) is provided on the upper surface of the first dielectric substrate (2); a lower microstrip metal structure (4) is provided on the upper surface of the second dielectric substrate (5), and a bottom ground metal layer (7) is provided on the lower surface of the second dielectric substrate (5); the top metal structure (1) and the lower microstrip metal structure (4) are connected by a conductive metal pillar structure (3); a metallized via (6) is also provided in the middle of the second dielectric substrate (5), and the metallized via (6) penetrates the second dielectric substrate (5) and the bottom ground metal layer (7); The top metal structure (1) includes four artificial local surface plasmon resonance rings with identical structures and arranged in a centrally symmetrical manner, namely the first resonance ring (11), the second resonance ring (12), the third resonance ring (13), and the fourth resonance ring (14); the artificial local surface plasmon resonance ring includes an outer metal ring and toothed metal segments arranged periodically at fixed intervals, wherein one end of the periodic toothed metal segments is connected to the outer metal ring, and the extension line of the other end points to the center of the outer metal ring; The conductive metal pillar structure (3) includes four centrally symmetrically arranged vertical conductive metal pillars, namely the first conductive metal pillar (31), the second conductive metal pillar (32), the third conductive metal pillar (33), and the fourth conductive metal pillar (34); the top ends of the first conductive metal pillar (31), the second conductive metal pillar (32), the third conductive metal pillar (33), and the fourth conductive metal pillar (34) are respectively connected to the end of a toothed metal segment on the first resonant ring (11), the second resonant ring (12), the third resonant ring (13), and the fourth resonant ring (14); The lower microstrip metal structure (4) includes a first microstrip line (41), a second microstrip line (42), a third microstrip line (43), a fourth microstrip line (44), a first impedance matching branch (45), a second impedance matching branch (46), a third impedance matching branch (47), and a fourth impedance matching branch (48); the first microstrip line (41), the second microstrip line (42), the third microstrip line (43), and the fourth microstrip line (44) are connected end to end in sequence, wherein the lengths of the first microstrip line (41), the second microstrip line (42), and the third microstrip line (43) are equal, and the line widths increase sequentially; the first impedance matching branch... The first ends of the first impedance matching branch (45), the second impedance matching branch (46), the third impedance matching branch (47), and the fourth impedance matching branch (48) are respectively connected to the ends of the first microstrip line (41), the second microstrip line (42), the third microstrip line (43), and the fourth microstrip line (44); the ends of the first impedance matching branch (45), the second impedance matching branch (46), the third impedance matching branch (47), and the fourth impedance matching branch (48) are respectively connected to the bottom ends of the first conductive metal pillar (31), the second conductive metal pillar (32), the third conductive metal pillar (33), and the fourth conductive metal pillar (34).

2. The band-reconfigurable radio frequency energy harvester unit based on metasurfaces according to claim 1, characterized in that: The first dielectric substrate (2) and the second dielectric substrate (5) are both square substrates of the same size and are aligned vertically; the top metal structure (1) is aligned with the center of the first dielectric substrate (2) and the second dielectric substrate (5).

3. The band-reconfigurable radio frequency energy harvester unit based on metasurfaces according to claim 1, characterized in that: The top end of the metallized via (6) is connected to the beginning end of the fourth microstrip line (44); the bottom metal ground layer (7) has a hole aligned with the center of the metallized via (6), and the hole and the bottom end of the metallized via (6) form a wireless radio frequency energy harvesting port.

4. The band-reconfigurable radio frequency energy harvester unit based on metasurfaces according to claim 1, characterized in that: The first dielectric substrate (2) and the second dielectric substrate (5) are both made of FR4 dielectric material with a dielectric constant of 4.3 and a loss tangent of 0.02, and their thicknesses are both 0.4 to 1.5 mm; the thickness of the air layer is 5 to 15 mm.

5. The band-reconfigurable radio frequency energy harvester unit based on metasurfaces according to claim 1, characterized in that: The first resonant ring (11), the second resonant ring (12), the third resonant ring (13) and the fourth resonant ring (14) do not overlap; among the periodic toothed metal branches, except for the branches connected to the conductive metal pillars, the other branches have the same length and do not overlap.

6. The band-reconfigurable radio frequency energy harvester unit based on metasurfaces according to claim 1, characterized in that: The first microstrip line (41), the second microstrip line (42) and the third microstrip line (43) are all circular rings with an opening angle of 270 degrees and the same radius, and their centers are aligned with the center of the second dielectric substrate (5); the center of the metallized via (6) is aligned with the center of the second dielectric substrate (5); the first impedance matching stub (45), the second impedance matching stub (46), the third impedance matching stub (47) and the fourth impedance matching stub (48) are all formed by connecting two stubs of different widths in series.

7. The band-reconfigurable radio frequency energy harvester unit based on metasurface according to claim 1, characterized in that: The first conductive metal pillar (31), the second conductive metal pillar (32), the third conductive metal pillar (33) and the fourth conductive metal pillar (34) are all solid copper pillars.

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