A cross-polarizer for microwave wireless energy transfer

Abstract

The application discloses a cross polarizer for microwave wireless energy transmission, which comprises a dielectric substrate and upper and lower metal layers respectively located on the top and bottom of the dielectric substrate, the upper and lower metal layers are connected through a plurality of metal vias; the upper and lower metal layers are etched with topological structures, and the topological structure of the lower metal layer is obtained by horizontally rotating the topological structure of the upper metal layer by 90 degrees; the topological structure comprises a dumbbell-shaped structure, the dumbbell-shaped structure is composed of two transverse grooves and a longitudinal groove, and the two transverse grooves are respectively located at two ends of the longitudinal groove, two symmetrical T-shaped metal stubs are arranged in the dumbbell-shaped structure; a square via hole is formed in the middle of the dielectric substrate and is used for compressing the flowing space of the surface current in the longitudinal groove; the cross polarizer can guarantee the transmission efficiency of the energy transmission system, and has the advantages of simple structure, low cost, small thickness and high polarization conversion rate.

Description

Technical Field

[0001] This invention relates to the field of electromagnetic technology, and more specifically to a cross-polarizer for microwave wireless power transmission. Background Technology

[0002] Microwave wireless power transmission technology, as a novel wireless power transmission technology with long transmission distance and mobile power transmission characteristics, has attracted attention and research in many energy fields. In microwave wireless power transmission systems, energy is transmitted between transceivers in the form of microwaves. To better receive microwave energy, the polarization of the receivers usually needs to be the same. However, in mobile power transmission scenarios (such as power transmission from drones), the attitude of the receivers is constantly changing, causing the polarization of the transceivers to become mismatched, which greatly reduces the system's energy transmission efficiency. Especially when the polarization is cross-polarized, the system efficiency may plummet to 0, causing the receiver to receive no energy. To solve this special problem, cross-polarizers, as electromagnetic wave polarization correctors, can purposefully manipulate the electromagnetic wave polarization, ultimately achieving a perfect match between the polarization of the transceivers.

[0003] At present, although some cross-polarization converters designed with special materials (such as graphene) have shown significant polarization operation capabilities, these materials are relatively expensive and difficult to design and manufacture, making them impractical in conventional engineering applications. Therefore, designing a low-profile, high-efficiency cross-polarizer using common materials is an urgent need in the field of microwave wireless power transmission. Summary of the Invention

[0004] To address the aforementioned shortcomings of existing technologies, this invention provides a cross-polarizer for microwave wireless power transmission, which solves the problems of high cost and difficult fabrication of existing graphene cross-polarizers.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A cross-polarizer for microwave wireless power transmission is provided, comprising a dielectric substrate and an upper metal layer and a lower metal layer located at the top and bottom of the dielectric substrate, respectively, connected by a plurality of metal vias; both the upper and lower metal layers are etched with a topology, and the topology of the lower metal layer is obtained by horizontally rotating the topology of the upper metal layer by 90 degrees; the topology includes a dumbbell-shaped structure, which consists of two transverse trenches and one longitudinal trench, with the two transverse trenches located at the two ends of the longitudinal trench, and two symmetrical T-shaped metal branches disposed within the dumbbell-shaped structure; a square via is provided in the middle of the dielectric substrate to compress the space for surface current flow within the longitudinal trench.

[0007] Furthermore, the T-shaped metal branch includes longitudinal and transverse segments that are perpendicular to each other, with both longitudinal segments parallel to the extension direction of the longitudinal groove, and the two transverse segments located at the ends of the two longitudinal segments that are close to each other.

[0008] Furthermore, the projection of the square via on the upper metal layer is located in the middle of the longitudinal trench in the upper metal layer and between the two transverse sections, and the projection of the square via on the lower metal layer is located in the middle of the longitudinal trench in the lower metal layer and between the two transverse sections.

[0009] Furthermore, the length of the transverse section is less than the width of the longitudinal groove.

[0010] Furthermore, the dielectric substrate, the upper metal layer, and the lower metal layer are all square thin plate structures, and there are two metal vias, which are located at two opposite corners of the dielectric substrate, the upper metal layer, and the lower metal layer.

[0011] Furthermore, the transverse grooves and longitudinal grooves are smoothly connected.

[0012] Furthermore, the dielectric substrate is made of F4B dielectric material, which has a dielectric constant of 2.65 and a loss tangent of 0.002.

[0013] Furthermore, the upper metal layer, the lower metal layer, and the metal vias are made of copper.

[0014] Furthermore, the microwave power transmission frequency range of the cross-polarizer is 5.53 GHz to 6.12 GHz.

[0015] Furthermore, the microwave transmission frequency with the lowest cross-polarizer energy loss ratio is 5.8 GHz.

[0016] The beneficial effects of this invention are as follows:

[0017] 1. The cross-polarizer in this scheme is used for polarization matching between the transceiver and receiver in a microwave wireless power transmission system. This ensures the transmission efficiency of the power transmission system even when the transceiver and receiver exhibit cross-polarization. It has a simple structure, low cost, small thickness, and high polarization conversion rate.

[0018] 2. This solution uses a dumbbell-shaped structure design to make the transition between the transverse and longitudinal grooves smoother, which is conducive to collecting more surface current from the longitudinal groove to the transverse groove; the square via design can effectively compress the flow space of surface current in the longitudinal groove, so that a stronger current intensity is formed in the transverse groove, which can lay the foundation for generating more directional polarized electromagnetic waves.

[0019] 3. This scheme further compresses the non-metallic area of ​​the longitudinal trench through two symmetrical T-shaped metal branches, thereby reducing the area for surface current flow and increasing the current density. This leads to more current flowing into the transverse trench, enhancing the current intensity in its vicinity and thus improving the polarization conversion ratio of the cross-polarizer.

[0020] 4. Under cross-polarization, this solution can improve the transmission efficiency of microwave wireless power transmission systems to 85.0%~92.5% of that under the same polarization, solving the problem of sharp drop in energy transmission efficiency caused by polarization mismatch in mobile power transmission scenarios. At the same time, the cross-polarizer of this solution is suitable for microwave wireless power transmission systems and can also be extended to other communication and radar systems that require polarization matching, which has high practicality and flexibility. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the layered structure of the cross-polarizer in this scheme.

[0022] Figure 2 for Figure 1 Top view.

[0023] Figure 3 (a) A material and dimensioning diagram for the cross-polarizer layer in this scheme.

[0024] Figure 3 (b) is a top view of the dimensions of the upper metal layer.

[0025] Figure 3 (c) is a top view of the lower metal layer with dimension annotations.

[0026] Figure 4 The diagram shows the surface current distribution on I-shaped and dumbbell-shaped structures.

[0027] Figure 5 This diagram shows the surface current distribution of a cross-polarizer with and without T-shaped metal stubs.

[0028] Figure 6 The graph shows the polarization conversion ratio curves for the cross-polarizer with and without T-shaped metal stubs.

[0029] Figure 7 The simulation curves show the transmission coefficient and polarization conversion ratio of the cross-polarizer.

[0030] Figure 8 This diagram shows the distribution of current on the upper surface of the cross-polarizer and the electric field on both sides.

[0031] Figure 9 The simulation curves show the reflection coefficient of the cross-polarizer and the microwave energy power loss ratio.

[0032] Figure 10 A diagram of the reflection and transmission coefficient measurement system built for this scheme.

[0033] Figure 11(a) shows the transmission coefficient of the cross-polarizer. T yy The test curve graph.

[0034] Figure 11(b) shows the transmission coefficient of the cross-polarizer. T xy The test curve graph.

[0035] Figure 11(c) shows the reflection coefficient of the cross-polarizer. R yy The test curve graph.

[0036] Figure 11(d) shows the reflection coefficient of the cross-polarizer. R xy The test curve graph.

[0037] Figure 11(e) is a test curve of the polarization conversion ratio of the cross-polarizer.

[0038] Figure 11(f) is a test curve of microwave energy power loss ratio of cross-polarizer.

[0039] Figure 12 Diagram of the microwave wireless power transmission system built for this solution.

[0040] Figure 13 The graph shows the test curves of microwave energy power captured by the receiver under different conditions.

[0041] Among them, 1. dielectric substrate, 2. upper metal layer, 3. lower metal layer, 4. metal via, 5. dumbbell-shaped structure, 51. transverse trench, 52. longitudinal trench, 6. T-shaped metal branch, 61. longitudinal section, 62. transverse section, 7. square via. Detailed Implementation

[0042] The specific embodiments of the present invention are described below to enable those skilled in the art to understand the present invention. However, it should be understood that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, various changes are obvious as long as they are within the spirit and scope of the present invention as defined and determined by the appended claims. All inventions utilizing the concept of the present invention are protected.

[0043] In order to achieve electromagnetic wave polarization state switching when cross-polarization occurs between the transceiver and receiver, it is essential to use a high-efficiency cross-polarizer to control the electromagnetic field.

[0044] like Figure 1 and Figure 2As shown, this scheme uses F4B dielectric material with relatively stable electrical parameters as dielectric substrate 1, with a dielectric constant of 2.65 and a loss tangent of 0.002. The upper metal layer 2 and the lower metal layer 3 of the dielectric substrate 1 have the same topology, and the topology of the lower metal layer 3 is obtained by rotating the topology of the upper metal layer 2 by 90 degrees. The upper metal layer 2 and the lower metal layer 3 are connected by metal vias 4.

[0045] At the top of the dielectric layer, compared with the traditional method of etching an I-shaped structure on the metal layer, this solution proposes a dumbbell-shaped structure 5 design, which consists of two transverse trenches 51 and one longitudinal trench 52. The two transverse trenches 51 are located at the two ends of the longitudinal trench 52, and the transverse trenches 51 and the longitudinal trench 52 are smoothly connected, which is conducive to collecting more surface current from the longitudinal trench 52 onto the transverse trenches 51. This solution has a square via 7 in the middle of the dielectric substrate 1, which can effectively compress the surface current flow space in the longitudinal trench, so that a stronger current intensity is formed on the transverse trenches 51, which can lay the foundation for generating more directional polarized electromagnetic waves.

[0046] like Figure 3 As shown, this scheme presents the structural dimensions of the cross-polarizer, wherein, Figure 3 (a) is a schematic diagram of the layered structure of the cross-polarizer. Figure 3 (b) is a top view of the cross-polarizer. Figure 3 (c) is a bottom view of the cross-polarizer; its corresponding dimensional parameters are as follows: p = 19.7 mm, l = 18.2 mm, l 1 = 5.4 mm, l 2 = 8.0 mm, l 3 = 2.8 mm w = 1.7mm, w 2 = 0.8 mm, w 3 = 0.3 mm, r = 0.5 mm, r 1 = 1.4 mm, h = 2.9 mm, h 1 = 0.035 mm, p x = 6.5 mm, p y = 6.5 mm.

[0047] like Figure 4 As shown, it illustrates the surface current distribution on the 2×2 I-shaped structure and the dumbbell-shaped structure 5, respectively.

[0048] To improve the polarization conversion ratio (PCR) of the cross-polarizer, two symmetrical T-shaped metal branches 6 are placed inside the dumbbell-shaped structure 5. The T-shaped metal branches 6 include mutually perpendicular longitudinal sections 61 and transverse sections 62. Both longitudinal sections 61 are parallel to the extension direction of the longitudinal trench 52, and the two transverse sections 62 are located at the ends of the two longitudinal sections 61 that are close to each other. Due to the design of the T-shaped metal branches 6, the non-metallic area of ​​the longitudinal trench 52 is further compressed, which reduces the area for surface current flow and thus increases the current density. This causes more current to flow to the transverse trench 51, thereby enhancing the current intensity in its vicinity.

[0049] like Figure 5 As shown, it illustrates the surface current distribution on the dumbbell-shaped structure 5 with 2×2 dumbbell-shaped structures 5 and with the addition of T-shaped metal branches 6, respectively; Figure 6 As shown, it illustrates the results of the polarization conversion ratio in two cases, from Figure 3 It can be observed that the T-shaped metal stub 6 significantly enhances the polarization ratio in most frequency ranges (5.3GHz~6.8GHz), thus the T-shaped metal stub 6 has a significant effect on optimizing the polarization ratio.

[0050] In the electromagnetic simulation software CST Studio Suite 2021, the proposed cross-polarizer was simulated and verified using periodic boundary conditions and Floquent ports. Its corresponding transmission coefficient was obtained, and the corresponding polarization conversion ratio was calculated. The simulation results are as follows: Figure 7 As shown.

[0051] exist Figure 7 The results are shown when the incident wave is y-polarized. It can be observed that in the frequency range of 5.53 GHz to 6.12 GHz, the transmission coefficient corresponding to the transformation of the y-polarized incident wave into the x-polarized outgoing wave is ( T xy All are greater than 0.9, and T xy The maximum value can reach 0.975; at the same time, the transmission coefficient corresponding to the transformation of the y-polarized incident wave into the y-polarized outgoing wave ( T yy The corresponding value is only 0.017; in most of the simulation frequency range (5.2GHz~6.8GHz), the corresponding PCR exceeds 0.985, and the maximum value exceeds 0.99.

[0052] To observe the effect of the cross-polarizer on electromagnetic wave conversion, the current on the surface of the cross-polarizer and the electric field on both sides nearby were extracted and plotted. The corresponding results are as follows: Figure 8 As shown.

[0053] Generally, a change in the direction of surface current flow is a prerequisite for a change in polarization. Figure 8 In (a), it can be observed that the current mainly flows along the y-axis. When the electromagnetic wave passes through the cross-polarizer, the current changes to flow along the x-axis, as shown in 8(b). The current direction rotates by 90°, indicating that the incident wave may have undergone a cross-polarization transition as it passes through the cross-polarizer. Furthermore, the metal via 4 allows more current to flow from the incident side to the emitting side of the electromagnetic wave, increasing the polarization conversion rate of the cross-polarizer. In addition, at a microwave transmission frequency of 5.8 GHz, the electric fields on both sides of the cross-polarizer were simulated and extracted, as shown in... Figure 8 As shown in (c) and 8(d), it can be found that the vector electric fields on both sides of the cross-polarizer exhibit a 90° angle; therefore, based on the changes in surface current and spatial electric field, it can be confirmed that the designed cross-polarizer has the function of cross-polarization conversion.

[0054] To verify that the proposed cross-polarizer can be applied to microwave wireless power transmission, the reflection coefficient of the cross-polarizer can be simulated, and the microwave energy loss in the cross-polarizer in all frequency bands can be calculated. P loss Percentage, corresponding results are as follows Figure 9 As shown.

[0055] from Figure 9 It can be observed that across all simulation frequency ranges, the y-polarized incident wave is converted into an x-polarized wave, and the reflection coefficient at the incident side of the cross-polarizer is ( R xy The values ​​of ) and the reflection coefficients of the y-polarized incident wave converted into x-polarized waves on the incident side of the cross-polarizer ( R yy The values ​​are very small, indicating that only a small portion of the y-polarized incident wave is converted into an x-polarized wave on the incident side of the cross-polarizer; furthermore, according to calculations... P loss The curves show that the maximum energy loss in the cross-polarizer is only 5.12%, and at the power transmission frequency of 5.8 GHz, the corresponding energy loss ratio is only 4.31%, while 94.98% of the energy passes through the cross-polarizer.

[0056] To verify the polarization control capability of the designed cross-polarizer in a real-world wireless power transmission environment, a polarization converter sample measuring 98.5mm*137.9mm*2.9mm was fabricated. To verify the sample's reflection and transmission coefficients, two linearly polarized antennas were used as the transmitter and receiver, respectively, and the antenna parameters were recorded using a vector network analyzer. Furthermore, a large amount of absorbing material was used during the measurement to reduce the impact of the environment on the test results. The test environment included... Figure 10 As shown in Figure 11, the measured transmittance, reflectance, PCR, and energy loss ratio were calculated and recorded.

[0057] In Figure 11, all the test results are very close to the simulation results. As shown in Figures 11(a) and 11(b), the transmission coefficients show that the measured results are valid across all test frequencies. T yy Very small, at the same time T xy The values ​​are very high, with some values ​​exceeding 99.0%, indicating that the vast majority of the y-polarized incident waves have been converted into x-polarized outgoing waves. Figure 11(e) shows PCR at different frequencies, revealing that the samples designed across all test frequencies exhibit strong polarization conversion capabilities, with the smallest PCR exceeding 98.5% and the largest reaching 99.95%. All these measurements and calculations demonstrate that the cross-polarizer in this design can be used for cross-polarization conversion.

[0058] Furthermore, Figures 11(c), 11(d), and 11(f) record the reflection parameters and the calculated microwave energy loss ratio in the sample, respectively; it can be found that at a frequency of 5.8 GHz, R yy A value less than 0.1 means that only a small portion of the y-polarized incident wave is reflected; additionally, R xy The energy loss is extremely low; almost no y-polarized waves are converted into x-polarized waves on the incident side of the surface. Based on the measured data, it can be calculated that the microwave energy loss ratio in the sample is only 6.6% at a frequency of 5.8 GHz. The measured and calculated data prove that the cross-polarizer of this scheme can be applied to microwave wireless power supply.

[0059] To verify the polarization conversion function of the design sample under wireless power transmission conditions, this scheme can build a wireless power transmission system, such as... Figure 12 As shown.

[0060] In a microwave power transfer (MPT) system, two horn antennas serve as the power transmitter and receiver, respectively; the collected power is recorded by a power meter. Typically, when there is cross-polarization between the transmitter and receiver, the power output from the transmitter is almost impossible to collect effectively by the receiver. To address this issue and improve the power transfer efficiency (PTE) between the two ends, we embedded a cross-polarizer from this scheme at the transmitter, ensuring that the polarization direction of the generated electromagnetic wave is aligned with that of the receiving horn antenna. The final measurement results are as follows: Figure 13 As shown.

[0061] exist Figure 13 middle, P co represents the received power under the same polarization terminal condition. P cr represents the capture power during inter-terminal cross-polarization. P cr_cpc corresponds to the power measurement value and efficiency index of a sample with cross-polarization but an integrated cross-polarizer at the emitter. η Defined as P cr_cpc and P The ratio of co.

[0062] Experimental results clearly show that co-polarization between terminals yields the maximum power collection, while cross-polarization results in the minimum power. Notably, even with two horn antennas in cross-polarization, the cross-polarizer sample still enables the receiver to achieve near-maximum power collection, reaching 85.0%–92.5% of the transmission power under co-polarization between terminals. Measurement results indicate that the cross-polarizer proposed in this scheme has the potential to improve the PTE of the MPT system, maintaining good performance even when cross-polarization exists between the transmitter and receiver.

Claims

1. A cross-polarizer for microwave wireless power transfer, characterized in that, It includes a dielectric substrate and an upper metal layer and a lower metal layer located at the top and bottom of the dielectric substrate, respectively, wherein the upper metal layer and the lower metal layer are connected by a plurality of metal vias; Both the upper and lower metal layers are etched with topological structures, and the topological structure of the lower metal layer is obtained by rotating the topological structure of the upper metal layer horizontally by 90 degrees. The topology includes a dumbbell-shaped structure, which consists of two transverse grooves and one longitudinal groove, with the two transverse grooves located at the two ends of the longitudinal groove, and two symmetrical T-shaped metal branches disposed within the dumbbell-shaped structure. A square via is provided in the middle of the dielectric substrate to compress the space for surface current to flow in the longitudinal trench. The T-shaped metal branch includes longitudinal and transverse segments that are perpendicular to each other, with both longitudinal segments parallel to the extension direction of the longitudinal groove and the two transverse segments located at the ends of the two longitudinal segments that are close to each other. The projection of the square via on the upper metal layer is located in the middle of the longitudinal trench in the upper metal layer and between two transverse sections. The projection of the square via on the lower metal layer is located in the middle of the longitudinal trench in the lower metal layer and between two transverse sections.

2. The cross-polarizer for microwave wireless power transmission according to claim 1, characterized in that, The length of the transverse section is less than the width of the longitudinal groove.

3. The cross-polarizer for microwave wireless power transmission according to claim 1, characterized in that, The dielectric substrate, upper metal layer, and lower metal layer are all square thin plate structures. There are two metal vias, and the two metal vias are located at two opposite corners of the dielectric substrate, upper metal layer, and lower metal layer.

4. The cross-polarizer for microwave wireless power transmission according to claim 1, characterized in that, The transverse grooves and longitudinal grooves are smoothly connected.

5. The cross-polarizer for microwave wireless power transfer according to claim 1, characterized in that, The dielectric substrate is made of F4B dielectric material, which has a dielectric constant of 2.65 and a loss tangent of 0.

002.

6. The cross-polarizer for microwave wireless power transfer according to claim 1, characterized in that, The upper metal layer, lower metal layer, and metal vias are made of copper.

7. The cross-polarizer for microwave wireless power transfer according to claim 1, characterized in that, The microwave power transmission frequency range of the cross-polarizer is 5.53 GHz to 6.12 GHz.

8. The cross-polarizer for microwave wireless power transfer according to claim 7, characterized in that, The microwave transmission frequency with the lowest energy loss ratio of the cross-polarizer is 5.8 GHz.

Images