Radio frequency energy collector based on metasurface

Abstract

The invention discloses a radio frequency energy collector based on a metasurface, and belongs to the field of radio frequency energy collection, the radio frequency energy collector is formed by arranging a plurality of periodic metasurface units, each periodic metasurface unit comprises a metal resonance structure, a dielectric layer and a metal bottom plate, the dielectric layer is located between the metal resonance structure and the metal bottom plate, and the metal bottom plate is located between the dielectric layer and the metal resonance structure. The metal resonance structure is a double-ring resonance ring structure, a through hole is formed in the double-ring resonance ring structure, the through hole penetrates through the dielectric layer and the metal bottom plate, an open hole is formed in the metal bottom plate, the open hole and the through hole are concentric, the radius of the open hole is larger than that of the through hole, and the open hole is communicated with the through hole; an annular metal sheet is arranged in the open hole, the annular metal sheet is connected with the bottom of the through hole, and a load is arranged between the open hole and the annular metal sheet. The problems that dual-band energy cannot be independently extracted when radio frequency energy is collected in the prior art, and the energy capture efficiency is low when an incident angle deviates can be solved.

Description

Technical Field

[0001] The present invention relates to the field of radio frequency energy collection, and in particular to a radio frequency energy collector based on a metasurface. Background Art

[0002] With the rapid development of the Internet of Things and wireless sensor technology, wireless sensor networks for micro-UAVs have been widely used due to the convenience of not requiring wiring. However, traditional battery-powered methods have defects such as large size, short life, and high replacement cost, which makes it difficult to meet the application requirements of lightweight and long-endurance micro-UAVs. RF energy harvesting technology captures environmental electromagnetic wave energy to power sensors, making it an ideal solution to replace or supplement batteries. Current RF energy harvesting systems mostly use antennas as energy receiving front ends, but their performance is limited by single-band collection capabilities and polarization sensitivity.

[0003] Although existing studies have achieved dual-frequency energy collection through a double-open diamond-shaped nested metal ring structure, there are still problems such as the inability to extract dual-frequency energy independently and the lack of efficient rectification circuit design, which limits the energy conversion efficiency in practical applications. In addition, existing solutions are sensitive to the incident angle of electromagnetic waves. The energy capture efficiency drops significantly when the incident angle is large, while the RF energy in the environment is often distributed in multiple frequency bands and has a low energy density. Single-frequency or narrow-band collection is difficult to meet actual power supply needs. In recent years, metasurfaces have shown the potential to replace traditional antennas due to their advantages such as miniaturization, high efficiency, and ease of sharing, but their design still faces challenges in multi-band collaborative collection and wide-angle incident stability.

[0004] Therefore, how to develop a metasurface energy harvester that is multi-band compatible and angle-insensitive has become the key to breaking through the application bottleneck of RF energy harvesting technology. Summary of the invention

[0005] The purpose of the present invention is to provide a RF energy collector based on a metasurface to solve the problem that dual-band energy cannot be extracted independently when collecting RF energy in the prior art, and the energy capture efficiency is low when the incident angle is offset.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions: In a first aspect, a metasurface-based RF energy collector is composed of a plurality of periodic metasurface units, each of which includes: a metal resonant structure, a dielectric layer and a metal base plate, wherein the dielectric layer is located between the metal resonant structure and the metal base plate, the metal resonant structure is a double-annular resonant ring structure, a through hole is arranged on the double-annular resonant ring structure, and the through hole passes through the dielectric layer and the metal base plate, an opening is arranged on the metal base plate, the opening is concentric with the through hole and the radius of the opening is larger than the radius of the through hole, the opening is connected to the through hole, an annular metal sheet is arranged inside the opening, the annular metal sheet is connected to the bottom of the through hole, and a load is arranged between the opening and the annular metal sheet.

[0007] In some embodiments, the metal resonant structure includes a first square resonant ring and a second square resonant ring, the first square resonant ring and the second square resonant ring are concentric, and a side length of the first square resonant ring is greater than a side length of the second square resonant ring.

[0008] In some embodiments, the first square resonant ring has a side length of 12.2 mm and a line width of 1.55 mm, and the second square resonant ring has a side length of 6.4 mm and a line width of 2 mm.

[0009] In some embodiments, a first through hole is set on the first square resonant ring, a second through hole is set on the second square resonant ring, a first opening and a second opening are respectively set at positions corresponding to the first through hole and the second through hole on the metal base plate, a first annular metal sheet is set inside the first opening, a second annular metal sheet is set inside the second opening, the first annular metal sheet is connected to the bottom of the first through hole, and the second annular metal sheet is connected to the bottom of the second through hole.

[0010] In some embodiments, a first load is disposed between the first opening and the first annular metal sheet, and a second load is disposed between the second opening and the second annular metal sheet.

[0011] In some implementations, the first load and the second load are both pure resistors, the resistance of the first load is 918Ω, and the resistance of the second load is 915Ω.

[0012] In some embodiments, the radius of the through hole is 0.25 mm, and the radius of the opening is 0.5 mm.

[0013] In some embodiments, the projection of the periodic metasurface unit is a square, and the side length of the projection of the periodic metasurface unit is 14 mm.

[0014] In some embodiments, the metal base plate and the metal resonant structure have a thickness of 0.035 mm and are made of copper.

[0015] In some embodiments, the dielectric layer has a thickness of 2 mm and is made of Roger TMM 10i, with a relative dielectric constant of 10.2 and a loss tangent of 0.002.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The present invention adopts a dual-annular resonant ring structure to form dual resonance points, and excites electromagnetic resonances in different frequency bands through size differences, thereby realizing independent capture of dual-frequency energy of 2.45GHz and 5.8GHz, and can cover the main frequency bands of ambient radio frequency energy, solve the problem of insufficient power supply for single-frequency collection in the prior art, and realize independent capture of dual-band energy; in addition, a through hole is arranged on the dual-annular resonant ring structure, an opening is arranged on the metal bottom plate, the opening is connected to the through hole, an annular metal sheet is arranged inside the opening, the annular metal sheet is connected to the bottom of the through hole, a load is arranged between the opening and the annular metal sheet, and independent transmission and matching of dual-frequency energy are realized through physical isolation, thereby avoiding mutual interference of dual-frequency signals; the present invention adopts periodically arranged metasurface units to enhance the capture capability of oblique incident waves through phase regulation, and enhances the energy capture efficiency when the incident angle is offset.

[0017] Furthermore, the metal resonant structure includes a first square resonant ring and a second square resonant ring, and the first square resonant ring and the second square resonant ring are concentric, which can reduce the sensitivity of the polarization direction of the electromagnetic wave, maintain efficient energy collection within a wide range of incident angles, and break through the limitation of traditional structures on the sudden drop in efficiency at large angles of incidence.

[0018] Furthermore, the first square resonant ring and the second square resonant ring correspond to independent through holes, openings and loads respectively, which can achieve independent transmission and matching of dual-frequency energy through physical isolation, avoid mutual interference of dual-frequency signals, improve energy extraction efficiency, and provide a physical basis for subsequent multi-frequency rectification circuit design.

[0019] Furthermore, both the first load and the second load are pure resistors, the resistance of the first load is 918Ω, and the resistance of the second load is 915Ω, which matches the impedance characteristics of the resonant ring, ensuring maximum power transmission to the back-end circuit and providing stable input for subsequent high-efficiency rectifier circuit design.

[0020] Furthermore, the radius of the through hole is 0.25 mm, the radius of the opening is 0.5 mm, and the through hole penetrates the dielectric layer to connect the annular metal sheet and connect the opening, which can expand the electromagnetic field coupling area, form a low-loss energy transmission path, reduce energy reflection and dielectric loss, and improve energy transmission efficiency.

[0021] Furthermore, the dielectric layer uses the Roger TMM 10i dielectric board with high dielectric constant and low loss, which can suppress heat loss while reducing the size of the resonant structure, and achieve strong field confinement within the 2mm dielectric layer, which can meet the lightweight requirements of micro-UAVs. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 A schematic diagram of the 3D structure of a periodic metasurface unit of a radio frequency energy harvester provided in Example 1; Figure 2 A schematic diagram of a metal resonant structure of a periodic metasurface unit provided in Example 1; Figure 3 A schematic diagram of the connection between the openings on the metal bottom plate of the periodic metasurface unit provided in Example 1 and the load; Figure 4 The reflection coefficient of the periodic metasurface unit provided in Example 1; Figure 5 The energy collection efficiency of the periodic metasurface unit provided in Example 1 at vertical incidence; Figure 6 The energy collection efficiency of each port of the periodic metasurface unit provided in Example 1, wherein (a) is the energy collection efficiency of the first square resonant ring, and (b) is the energy collection efficiency of the second square resonant ring; Figure 7 The energy collection efficiency of the periodic metasurface unit provided in Example 1 at oblique incidence, wherein (a) and (b) are the energy collection efficiencies at oblique incidence at different angles, respectively.

[0023] In the figure, 1, metal resonant structure; 2, dielectric layer; 3, metal base plate; 4, first square resonant ring; 5, second square resonant ring; 6, second through hole; 7, first through hole; 8, second annular metal sheet; 9, first annular metal sheet; 10, second load; 11, first load. DETAILED DESCRIPTION

[0024] The exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the specific embodiments set forth herein. On the contrary, these embodiments are provided in order to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

[0025] In the following description, a large number of details are given to provide a more thorough understanding of the present disclosure. However, it is obvious to those skilled in the art that the present disclosure can be implemented without one or more of these details. In other examples, in order to avoid confusion with the present disclosure, some technical features known in the art are not described; that is, all features of actual embodiments are not described here, and well-known functions and structures are not described in detail.

[0026] It should be understood that when an element or layer is referred to as "on ...", "adjacent to ...", "connected to" or "coupled to" other elements or layers, it can be directly on, adjacent to, connected to or coupled to other elements or layers, or there can be intervening elements or layers. On the contrary, when an element is referred to as "directly on ...", "directly adjacent to ...", "directly connected to" or "directly coupled to" other elements or layers, there is no intervening element or layer. It should be understood that although the terms first, second, third, etc. can be used to describe various elements, components, regions, layers and / or parts, these elements, components, regions, layers and / or parts should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or part from another element, component, region, layer or part. Therefore, without departing from the teachings of the present disclosure, the first element, component, region, layer or part discussed below can be represented as the second element, component, region, layer or part. And when the second element, component, region, layer or part is discussed, it does not indicate that the present disclosure necessarily has the first element, component, region, layer or part.

[0027] The purpose of the terms used herein is only to describe specific embodiments and is not intended to be a limitation of the present disclosure. When used herein, the singular forms "one", "an" and "said / the" are also intended to include plural forms, unless the context clearly indicates otherwise. It should also be understood that the terms "consisting of" and / or "comprising", when used in this specification, determine the presence of the features, integers, steps, operations, elements and / or parts, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, parts and / or groups. When used herein, the term "and / or" includes any and all combinations of the relevant listed items.

[0028] Embodiment 1 like Figure 1 As shown, this embodiment provides a RF energy collector based on a metasurface, which is composed of a plurality of periodic metasurface units, each of which includes: a metal resonant structure 1, a dielectric layer 2 and a metal bottom plate 3, wherein the dielectric layer 2 is located between the metal resonant structure 1 and the metal bottom plate 3, and the metal resonant structure 1 is a double annular resonant ring structure, wherein a through hole is arranged on the double annular resonant ring structure, and the through hole passes through the dielectric layer 2 and the metal bottom plate 3; like Figure 2 As shown, the metal structure 1 adopts a dual-ring resonant ring structure, using two concentric closed first square resonant rings 4 and second square resonant rings 5; each of the two rings has a through hole, which passes through the dielectric layer and the metal floor, and is used to export the RF energy collected by the resonator.

[0029] Preferably, if Figure 3As shown, a circular hole, i.e., an opening, which is concentric with the two through holes and has a radius larger than the through holes is opened on the metal base plate 3, a first through hole 7 is arranged on the first square resonant ring 4, a second through hole 6 is arranged on the second square resonant ring, and a first opening and a second opening are arranged on the metal base plate 3 at positions corresponding to the first through hole 7 and the second through hole 6, respectively, a first annular metal sheet 9 is arranged inside the first opening, and a second annular metal sheet 8 is arranged inside the second opening, the first annular metal sheet 9 is connected to the bottom of the first through hole 7, and the second annular metal sheet 8 is connected to the bottom of the second through hole 6, to ensure that the annular metal sheets are inside the openings.

[0030] Preferably, a first load 11 is connected between the inner wall of the first opening of the metal base plate 3 and the first annular metal sheet 9, and a second load 10 is connected between the second opening and the second annular metal sheet 8. The first load 11 and the second load 10 are both pure resistors, and the resistance of the first load 11 is 918Ω, and the resistance of the second load 10 is 915Ω.

[0031] Preferably, the structure of the periodic hypersurface unit is a square structure, and the side length of the periodic hypersurface unit is 14 mm.

[0032] Preferably, the first square resonant ring 4 has a side length of 12.2 mm and a line width of 1.55 mm, and the second square resonant ring 5 has a side length of 6.4 mm and a line width of 2 mm.

[0033] Preferably, the thickness of the metal bottom plate 3 and the metal resonant structure 1 is 0.035 mm, and the material is copper.

[0034] Preferably, the radius of the first through hole 7 and the second through hole 6 are both 0.25 mm, and the radius of the first opening and the second opening are both 0.5 mm.

[0035] Preferably, the dielectric layer 2 is a low-loss dielectric, the material selected is Roger TMM 10i, the relative dielectric constant is 10.2, the loss tangent is 0.002, and the thickness of the dielectric layer 2 is 2 mm.

[0036] like Figure 4 As shown, in the CST electromagnetic simulation software, a 1W plane wave is used to excite the energy collection metasurface. The periodic metasurface unit structure of the RF energy collector provided in this embodiment has two absorption peaks at 2.45GHz and 5.8GHz. Since the bottom layer of the RF energy collector is metal copper, the transmission coefficient of the RF energy collector is 0. Therefore, the absorption rates of the periodic metasurface unit at 2.45GHz and 5.8GHz are 0.99 and 0.97 respectively, indicating that the periodic metasurface unit can achieve good electromagnetic wave absorption at two resonant frequencies.

[0037] like Figure 5As shown, the energy collection efficiency of the RF energy harvester provided in this embodiment in the 2.45 GHz and 5.8 GHz frequency bands is 85.1% and 85.3% respectively, which has good engineering application value.

[0038] like Figure 6 As shown, low-frequency energy is collected by port 4 of the first square resonant ring of the outer ring, and high-frequency energy is collected by port 5 of the second square resonant ring of the inner ring, indicating that the RF energy collector provided in this embodiment basically does not affect each other when collecting dual-frequency energy, and can absorb energy of 2.45 GHz and 5.8 GHz at the same time.

[0039] like Figure 7 As shown, when the electromagnetic wave is incident at an angle, the RF energy collector provided in this embodiment can still maintain a relatively high transmission efficiency. As the incident angle increases, a certain frequency offset will occur. This is due to the change in the wave path and can be adjusted by the back-end adaptive rectifier circuit.

[0040] In summary, the RF energy harvester based on a metasurface provided in this embodiment has the following advantages: (1) The periodic metasurface unit has a simple structure and a small size, and can achieve energy collection in the 5.8 GHz and 2.45 GHz frequency bands. The energy collection efficiencies are 85.3% and 85.1% respectively, which has good engineering application value.

[0041] (2) The low-frequency 2.45 GHz energy is collected by the first square resonant ring 4, and the high-frequency 5.8 GHz energy is collected by the second square resonant ring 5. Therefore, the above-mentioned dual-ring resonant ring structure does not affect each other when collecting dual-frequency energy, which is conducive to simplifying the back-end energy processing circuit.

[0042] (3) The energy collection efficiency can be maintained at both transverse electric mode (TE) oblique incidence and transverse magnetic mode (TM) oblique incidence, with good incident angle stability and polarization angle stability.

[0043] Embodiment 2 This embodiment provides a RF energy collector based on a metasurface on the basis of the first embodiment, which is composed of a plurality of periodic metasurface units, each of which includes: a metal resonant structure 1, a dielectric layer 2 and a metal bottom plate 3, wherein the dielectric layer 2 is located between the metal resonant structure 1 and the metal bottom plate 3; The metal resonant structure 1 includes three concentric square resonant rings from the outside to the inside. The first square resonant ring 4 has a side length of 12.2mm and a line width of 1.55mm, capturing 2.45GHz energy; the second square resonant ring 5 has a side length of 5.6mm and a line width of 2.2mm, capturing 5.8GHz energy; the third square resonant ring has a side length of 16.8mm and a line width of 1.2mm, capturing 900MHz low-frequency energy. The three square resonant rings are optimized through electromagnetic field coupling to avoid frequency band interference.

[0044] A circular hole, i.e., an opening, which is concentric with the three through holes and has a radius larger than the through holes is opened on the metal base plate 3. The size parameters of the through holes on the first square resonant ring 4 and the second square resonant ring 5 are consistent with those in the first embodiment. A third through hole is arranged on the third square resonant ring. A third opening is arranged at a position corresponding to the third through hole on the metal base plate 3. A third annular metal sheet is arranged inside the third opening. The third annular metal sheet is connected to the bottom of the third through hole to ensure that the third annular metal sheet is inside the opening. The inner walls of the three through holes are silver-plated to reduce transmission loss. The sawtooth structure at the edge of the opening enhances field coupling.

[0045] An air cavity is embedded in the dielectric layer and arranged below the third-party triangular resonant ring to reduce dielectric loss in the 900 MHz frequency band.

[0046] The periodic metasurface units are arranged in a hexagonal shape to improve the spatial coverage of oblique incident waves.

[0047] This embodiment designs a metal resonant structure including three concentric square resonant rings on the basis of the first embodiment. The collector can simultaneously capture RF energy in three different frequency bands of 2.45 GHz, 5.8 GHz and 900 MHz. This multi-band design improves the efficiency and flexibility of energy collection, enabling it to adapt to more diverse RF environments. The inner wall of the through hole on the metal bottom plate is silver-plated to reduce transmission loss and improve energy transmission efficiency. At the same time, an air cavity is embedded in the dielectric layer, especially under the third rectangular resonant ring, which significantly reduces the dielectric loss in the 900 MHz frequency band and further improves the energy collection efficiency. The serrated structure design of the edge of the opening enhances field coupling and helps to capture RF energy more effectively. Although this optimization in design details seems small, it plays a key role in improving overall performance. The hexagonal arrangement between the periodic metasurface units is compared with the traditional rectangular or square arrangement. The hexagonal arrangement can fill the space more tightly, thereby improving the spatial coverage of the oblique incident wave.

[0048] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A radio frequency energy harvester based on a metasurface, characterized in that: The invention is composed of a plurality of periodic metasurface units arranged in an arrangement, each of the periodic metasurface units comprising: a metal resonance structure (1), a dielectric layer (2) and a metal base plate (3), wherein the dielectric layer (2) is located between the metal resonance structure (1) and the metal base plate (3), the metal resonance structure (1) is a double annular resonance ring structure, a through hole is arranged on the double annular resonance ring structure, and the through hole penetrates the dielectric layer (2) and the metal base plate (3), an opening is arranged on the metal base plate (3), the opening is concentric with the through hole and the radius of the opening is larger than the radius of the through hole, the opening is connected to the through hole, an annular metal sheet is arranged inside the opening, the annular metal sheet is connected to the bottom of the through hole, and a load is arranged between the opening and the annular metal sheet.

2. The RF energy harvester based on a metasurface according to claim 1, characterized in that: The metal resonance structure (1) comprises a first square resonance ring (4) and a second square resonance ring (5); the first square resonance ring (4) and the second square resonance ring (5) are concentric; and the side length of the first square resonance ring (4) is greater than the side length of the second square resonance ring (5).

3. The RF energy harvester based on a metasurface according to claim 2, characterized in that: The first square resonant ring (4) has a side length of 12.2 mm and a line width of 1.55 mm, and the second square resonant ring (5) has a side length of 6.4 mm and a line width of 2 mm.

4. The RF energy harvester based on a metasurface according to claim 2, characterized in that: A first through hole (7) is provided on the first square resonant ring (4), a second through hole (6) is provided on the second square resonant ring, a first opening and a second opening are provided on the metal base plate (3) at positions corresponding to the first through hole (7) and the second through hole (6), a first annular metal sheet (9) is provided inside the first opening, a second annular metal sheet (8) is provided inside the second opening, the first annular metal sheet (9) is connected to the bottom of the first through hole (7), and the second annular metal sheet (8) is connected to the bottom of the second through hole (6).

5. The RF energy harvester based on a metasurface according to claim 4, characterized in that: A first load (11) is arranged between the first opening and the first annular metal sheet (9), and a second load (10) is arranged between the second opening and the second annular metal sheet (8).

6. The RF energy harvester based on a metasurface according to claim 5, characterized in that: The first load (11) and the second load (10) are both pure resistors, the resistance value of the first load (11) is 918Ω, and the resistance value of the second load (10) is 915Ω.

7. The RF energy harvester based on a metasurface according to claim 1, characterized in that: The radius of the through hole is 0.25 mm, and the radius of the opening is 0.5 mm.

8. The RF energy harvester based on a metasurface according to claim 1, characterized in that: The projection of the periodic hypersurface unit is a square, and the side length of the projection of the periodic hypersurface unit is 14 mm.

9. The RF energy harvester based on a metasurface according to claim 1, characterized in that: The thickness of the metal base plate (3) and the metal resonant structure (1) is 0.035 mm, and the material is copper.

10. The RF energy harvester based on a metasurface according to claim 1, characterized in that: The thickness of the dielectric layer (2) is 2 mm, and the material is Roger TMM 10i, with a relative dielectric constant of 10.2 and a loss tangent of 0.002.

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