Wireless electric energy transmission system based on honeycomb metamaterial and externally-square internally-circular coil

Abstract

The invention discloses a wireless electric energy transmission system based on a honeycomb metamaterial and a coil with a square outer part and a round inner part. The wireless electric energy transmission system comprises a transmitting coil, a receiving coil and a honeycomb metamaterial structure arranged between the transmitting coil and the receiving coil, wherein each of the transmitting coil and the receiving coil comprises a dielectric plate and a square-outside and round-inside coil arranged on the dielectric plate; the coil with the square outside and the round inside comprises a square spiral coil and a round spiral coil arranged in the square spiral coil; and the square spiral coil is connected with the circular spiral coil. The wireless electric energy transmission system is simple in structure, small in occupied space and convenient to install, and meanwhile the transmission efficiency and the transmission distance of the wireless electric energy transmission system can be effectively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of wireless energy transmission, and in particular to a wireless energy transmission system based on a honeycomb metamaterial and an outer square inner circle coil. Background Art

[0002] Wireless power transfer (WPT) has attracted great attention in various applications such as wireless charging of electronic products, medical devices and electric vehicles. Compared with traditional wired power supply methods, the emerging wireless power transfer technology is safer, more reliable and more convenient. In the near-field wireless power transfer technology, it is generally divided into two modes: inductive coupling and magnetic coupling. The transmission distance of inductive coupling WPT is very short, usually only a few centimeters. Unlike inductive coupling WPT, magnetic coupling WPT requires a compensation capacitor to make the system resonate at a certain frequency. The capacitive reactance cancels the inductive reactance, and the capacitor does not consume active power. Due to the resonance, energy can be transmitted to the receiving coil over a longer transmission distance. The two main factors to judge the performance of wireless power transfer schemes are power transfer efficiency (PTE) and transmission distance (d). Wireless power transfer (PTE) refers to the ratio of the power received by the charging device to the power transmitted by the transmitter; while the transmission distance (d) refers to the maximum distance between the transmitter (Tx) and the receiver (Rx) at which the receiver can receive power with acceptable power transfer efficiency (PTE);

[0003] In a wireless power transmission system, when the transmitting coil is designed to generate a uniform magnetic field distribution, the receiving coil can be freed in position and the receiving power and transmission efficiency can be stabilized. In fact, in order to achieve a uniform magnetic field, the prior art has proposed a variety of transmitting coils and receiving coils. The coupler is an important part of wireless power transmission technology. The high-performance coupling coil has a crucial impact on the transmission performance of the wireless power transmission system. Its design and optimization have a direct impact on the transmission efficiency, power, transmission distance, etc. of the wireless power transmission system. For a wireless power transmission system, there is a large air gap between the transmitting and receiving parts of the coupling coil during actual operation. Higher leakage magnetic flux will lead to a decrease in coupling performance, thereby greatly reducing the transmission efficiency of the entire wireless power transmission system. This phenomenon is particularly evident in the application of high-power power transmission systems. In order to improve the transmission efficiency of the wireless power transmission system, it is particularly important to design and optimize the shape of the coupling coil.

[0004] In wireless power transmission systems, the prior art is to increase the mutual inductance between the transmitting and receiving coils as an important measure to improve the efficiency of the wireless power transmission system. However, in practical applications, the load coil that receives the transmitted power inevitably has the problem of spatial position offset from the transmitting coil, which will lead to a decrease in the mutual inductance between the coils, and then reduce the transmission efficiency and output power. In the prior art, magnetizing materials such as ferrite are used to enhance the mutual inductance and coupling coefficient between the coils. Although the above method can improve the misalignment performance to a certain extent, the magnetizing materials such as ferrite used are heavy, large in size and space, and easily induce excessive current, which causes the temperature of the entire wireless power transmission system to rise, thereby causing the components to burn out. While improving performance, these shortcomings also bring additional system complexity and inconvenience in application. Summary of the invention

[0005] The purpose of the present invention is to overcome the above-mentioned problems and provide a wireless power transmission system based on honeycomb metamaterials and outer square inner circle coils. The wireless power transmission system is not only simple in structure, occupies a small space, and is easy to install, but also can effectively improve the transmission efficiency and transmission distance of the wireless power transmission system.

[0006] The purpose of the present invention is achieved through the following technical solutions:

[0007] A wireless power transmission system based on honeycomb metamaterial and outer square inner circle coil comprises a transmitting coil, a receiving coil and a honeycomb metamaterial structure arranged between the transmitting coil and the receiving coil; wherein:

[0008] The transmitting coil and the receiving coil both include a dielectric plate and an outer square inner circle coil arranged on the dielectric plate; the outer square inner circle coil includes a square spiral coil and a circular spiral coil arranged inside the square spiral coil; the square spiral coil is connected to the circular spiral coil.

[0009] The working principle of the wireless power transmission system based on the honeycomb metamaterial and the outer square inner circle coil is:

[0010] The alternating current is converted from the transmitting coil into electromagnetic waves and emitted into the air. The honeycomb metamaterial structure can converge the electromagnetic waves emitted by the transmitting coil, and the receiving coil receives the electromagnetic waves converged by the honeycomb metamaterial structure. The honeycomb metamaterial structure can effectively cover the transmitting coil and the receiving coil, improving the problem of low power transmission efficiency (PTE) due to the increase in transmission distance or lateral misalignment between square spiral coils. By adopting an outer square inner circle coil, it has the characteristics of generating a uniform and strong magnetic field at the transmitting end, and the radiation area is large. The honeycomb metamaterial structure is a near-zero or negative permeability electromagnetic metamaterial, which can improve the transmission distance and transmission efficiency of the wireless power transmission system. The near-zero and negative permeability electromagnetic structure has the characteristics of amplifying evanescent waves and improving the coupling characteristics of the resonant coil. It can not only focus more energy of the transmitting coil on the receiving coil, improve the transmission efficiency and transmission distance of wireless power transmission, but also has low cost and is easy to industrialize.

[0011] In a preferred embodiment of the present invention, the transmitting coil and the receiving coil are of a printed circuit board structure, the outer square inner circle coil is a copper layer printed on a dielectric board, and the thickness of the copper layer is 1 ounce; the material of the dielectric board is FR-4; the number of turns of the square spiral coil and the circular spiral coil are both 6. In the above structure, the inductance value (L) is adjusted by adjusting the line width and turn spacing of the square spiral coil and the circular spiral coil; the line width is the line width of the copper layer, and the turn spacing is the distance between the spiral lines of the square spiral coil or the distance between the spiral lines of the circular spiral coil.

[0012] Preferably, the outer square inner circle coil is arranged on the front of the dielectric plate, and a copper clad layer is arranged on the back of the dielectric plate. The two ends of the outer square inner circle coil are respectively connected to the copper clad layer through metallized vias arranged on the dielectric plate; and a compensation patch capacitor is arranged on the copper clad layer. By setting the above structure, the structure of the transmitting coil and the receiving coil is very compact, and the required frequency selection is achieved by setting the compensation patch capacitor, and the capacitance of the external compensation patch capacitor is 19.4pF.

[0013] Preferably, the copper clad layer includes a first microstrip line, a second microstrip line and a metal ground; the compensation patch capacitor is connected between the first microstrip line and the second microstrip line, the first microstrip line is connected to one end of the outer square inner circle coil; the other end of the outer square inner circle coil is connected to the metal ground; a radio frequency coaxial connector is provided on the side of the dielectric plate, the ground end of the radio frequency coaxial connector is welded to the metal ground, and the excitation end of the radio frequency coaxial connector is connected to the second microstrip line. In the above structure, a radio frequency coaxial connector (SMA for short) is provided on the side of the dielectric plate; side feeding is performed to introduce excitation, and the compensation patch capacitor is a tuning capacitor, and the resonant frequency can be adjusted by changing its capacitance, so that the transmitting coil and the receiving coil can resonate within the set working frequency.

[0014] Preferably, the honeycomb metamaterial structure is formed by a plurality of regular hexagonal metamaterial unit arrays. The honeycomb metamaterial structure is formed by a regular hexagonal metamaterial unit array, which is more compact. Compared with the 3×3, 4×4 and other matrix arrangements in the prior art, the honeycomb metamaterial structure has a lower cost and achieves higher power transmission efficiency.

[0015] Preferably, the metamaterial unit includes a regular hexagonal substrate, a regular hexagonal split ring arranged on and concentric with the substrate, and a circular open spiral coil arranged inside the split ring; the split opening on the split ring is connected to a tuning capacitor. In the above structure, the tuning capacitor of the metamaterial unit is used to adjust the real part of its relative magnetic permeability to be negative or near zero at an operating frequency of 13.56 MHz. The metamaterial unit with a negative real part of magnetic permeability can gather the magnetic field energy diverging from the edge, while the metamaterial unit with a near-zero real part of magnetic permeability can strengthen the center strength of the magnetic field. The metamaterial unit array of the present invention has both near-zero and negative magnetic permeability metamaterials, so it can be called a hybrid metamaterial.

[0016] Preferably, the number of metamaterial units is 7, one metamaterial unit is used as the central metamaterial unit, and the remaining six metamaterial units are peripheral metamaterial units, and the six peripheral metamaterial units are distributed around the central metamaterial unit. In the above structure, 7 metamaterial units can be arrayed to form a honeycomb metamaterial structure. The size of the entire honeycomb metamaterial structure is relatively small. A metamaterial array with too large size and area (such as 3×3, 4×4 matrix arrangement, etc.) will cause the metamaterial unit to have excessive internal resistance loss caused by induced current, thereby causing the entire wireless power transmission (WPT) system to have a reduced efficiency. A honeycomb arrangement is used as the optimal array structure for metamaterials.

[0017] Preferably, the capacitance of the tuning capacitor in the peripheral metamaterial unit is different from that of the tuning capacitor in the central metamaterial unit. By adding two tuning capacitors with different capacitances, a metamaterial unit with negative and near-zero magnetic permeability is realized.

[0018] Preferably, the capacitance of the tuning capacitor in the peripheral metamaterial unit is 560pF, and the capacitance of the tuning capacitor in the central metamaterial unit is 680pF. The capacitance of the tuning capacitors in the six peripheral metamaterial units is 560pF, which makes the resonant frequency of the metamaterial unit lower than the operating frequency, achieving the effect that the real part of the magnetic permeability is -2.13 and the imaginary part is 0; the capacitance of the tuning capacitor in the central metamaterial unit is 680pF, which makes the resonant frequency of the metamaterial unit lower than the operating frequency, achieving the effect that the real part of the magnetic permeability is close to 0 and the imaginary part is 0.

[0019] Preferably, the substrate is made of FR-4, and the split ring and the circular open spiral coil are arranged on the front side of the substrate.

[0020] Preferably, the honeycomb metamaterial structure is placed in the middle of the transmitting coil and the receiving coil. Its function is that the honeycomb metamaterial structure placed in the middle can completely cover the entire transmitting coil and the receiving coil, so as to ensure that all the electromagnetic energy generated by the transmitting coil passes through the honeycomb metamaterial structure, and the magnetic field energy is gathered to the receiving coil.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1. The wireless power transmission system of the present invention adopts a honeycomb metamaterial structure, which has a small overall size, a simple structure, and occupies a small space.

[0023] 2. In the wireless power transmission system of the present invention, the honeycomb metamaterial structure can effectively cover the transmitting coil and the receiving coil, improving the problem of low power transmission efficiency (PTE) due to the increase in transmission distance or lateral misalignment distance between square spiral coils; it has anti-misalignment performance.

[0024] 3. The wireless power transmission system of the present invention has the characteristic of being able to generate a uniform and strong magnetic field at the transmitting end by adopting an outer square and inner circle coil. The radiation area is large, and combined with the honeycomb metamaterial structure, the transmission efficiency and transmission distance of the wireless power transmission system can be effectively improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of the three-dimensional structure of a wireless power transmission system based on a honeycomb metamaterial and an outer square inner circle coil in the present invention.

[0026] Figure 2 It is a schematic diagram of the three-dimensional structure of the transmitting coil or the receiving coil in the present invention.

[0027] Figure 3 It is a schematic structural diagram of the front side of the transmitting coil or the receiving coil in the present invention.

[0028] Figure 4 It is a structural schematic diagram of the back side of the transmitting coil or the receiving coil in the present invention.

[0029] Figure 5 It is a schematic diagram of the structure of a square spiral coil in the prior art.

[0030] Figure 6 It is a schematic diagram of the three-dimensional structure of the honeycomb metamaterial structure in the present invention.

[0031] Figure 7 It is a schematic diagram of the three-dimensional structure of the metamaterial unit in the present invention.

[0032] Figure 8It is a schematic structural diagram of the front side of the metamaterial unit in the present invention.

[0033] Fig. 9 Schematic diagram of magnetic field strength of a square spiral coil in the prior art.

[0034] Fig.10 Schematic diagram of the magnetic field strength of the outer square inner circle coil in the present invention.

[0035] Fig.11 Schematic diagram of the relative magnetic permeability of the negative magnetic permeability metamaterial unit in the present invention.

[0036] Fig.12 Schematic diagram of the relative magnetic permeability of the near-zero metamaterial unit in the present invention.

[0037] Fig.13 This is a transmission efficiency diagram of the wireless power transmission system in the present invention when the transmission distance is 70MM.

[0038] Fig.14 Schematic diagram of magnetic field strength of a WPT system without a metamaterial unit array in the prior art.

[0039] Fig.15 Schematic diagram of magnetic field strength of the WPT system with metamaterial unit array (honeycomb metamaterial structure) in the present invention.

[0040] Fig.16 The figure is a comparison of the transmission efficiency with and without the metamaterial unit array as a function of the coil transmission distance.

[0041] Fig.17 The figure shows the comparison of the WPT transmission efficiency with and without the metamaterial unit array as a function of the horizontal offset distance of the coil.

[0042] Fig.18 is an equivalent circuit diagram of the wireless power transmission system in the present invention. DETAILED DESCRIPTION

[0043] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is further described below in conjunction with embodiments and drawings, but the embodiments of the present invention are not limited thereto.

[0044] See also Figure 1-Figure 2This embodiment discloses a wireless power transmission system based on a honeycomb metamaterial and an outer square inner circle coil, comprising a transmitting coil 1, a receiving coil 2 and a honeycomb metamaterial structure 3 arranged between the transmitting coil 1 and the receiving coil 2; wherein the structures of the transmitting coil 1 and the receiving coil 2 are exactly the same, and the transmitting coil 1 and the receiving coil 2 both comprise a dielectric plate 4 and an outer square inner circle coil arranged on the dielectric plate 4; the outer square inner circle coil is a concentric outer square inner circle spiral resonator coil, and the outer square inner circle coil comprises a square spiral coil 5 and a circular spiral coil 6 arranged inside the square spiral coil 5; the square spiral coil 5 is connected to the circular spiral coil 6.

[0045] See also Figure 1-Figure 5 and Figure 9-10 , the transmitting coil 1 and the receiving coil 2 are of printed circuit board structure, the outer square inner circle coil is a copper layer printed on the dielectric plate 4, and the thickness of the copper layer is 1 ounce; the material of the dielectric plate 4 is FR-4; the number of turns of the square spiral coil 5 and the circular spiral coil 6 are both 6. In the above structure, the inductance value (L) is adjusted by adjusting the line width W1 and the turn spacing S1 of the square spiral coil 5 and the circular spiral coil 6; the line width is the line width of the copper layer, and the turn spacing S1 is the distance between the spiral lines of the square spiral coil 5 or the distance between the spiral lines of the circular spiral coil 6. Fig. 9 and Fig.10 As shown, compared with the magnetic field strength generated by a conventional square spiral coil of the same size (square spiral coil of the prior art), the uniformity of the magnetic field strength and the radiation area generated by the outer square inner circle coil of this embodiment are better than those of the square spiral coil of the prior art.

[0046] See also Figure 2-Figure 3 In this embodiment, the dielectric plate 4 is square, and the specific physical dimensions of the outer square inner circle coil are: the side length L of the dielectric plate 4 is 100 mm, the thickness of the dielectric plate 4 is 1.6 mm, the thickness of the copper layer is 35 um, the outer side length L1 of the square spiral coil 5 is 86 mm, the line width W1 of the square spiral coil 5 and the circular spiral coil 6 (i.e., the line width of the outer square inner circle coil) is 2 mm, the turn spacing S1 of the square spiral coil 5 and the circular spiral coil 6 is 1 mm, and the inner diameter d of the circular spiral coil 6 is 10 mm.

[0047] See also Figure 2-Figure 4The dielectric board 4 is also called PCB. The outer square inner circle coil is arranged on the front of the dielectric board 4. The back of the dielectric board 4 is provided with a copper clad layer. The two ends (i.e., the two end joints) of the outer square inner circle coil are respectively connected to the copper clad layer through metallized vias arranged on the dielectric board 4. The copper clad layer is provided with a compensation patch capacitor 7. By setting the above structure, the transmitting coil 1 and the receiving coil 2 are very compact. By setting the compensation patch capacitor 7, the required frequency selection is achieved. The capacitance of the external compensation patch capacitor 7 is 19.4pF.

[0048] See also Figure 2-Figure 4 , the copper clad layer includes a first microstrip line 8, a second microstrip line 9 and a metal ground 10; the compensation patch capacitor 7 is connected between the first microstrip line 8 and the second microstrip line 9, the first microstrip line 8 is connected to one end of the outer square inner circle coil through a metallized via; the other end of the outer square inner circle coil is connected to the metal ground 10 through a metallized via; a radio frequency coaxial connector is provided on the side of the dielectric plate 4, the ground end of the radio frequency coaxial connector is welded to the metal ground 10, and the excitation end of the radio frequency coaxial connector is connected to the second microstrip line 9. In the above structure, a radio frequency coaxial connector (SMA for short) is provided on the side of the dielectric plate 4; side feeding is performed to introduce excitation, and the compensation patch capacitor 7 is a tuning capacitor, and the resonant frequency can be adjusted by changing its capacitance, so that the transmitting coil 1 and the receiving coil 2 can resonate within the set working frequency.

[0049] See also Figure 1 and Figure 6-Figure 8 The honeycomb metamaterial structure 3 is formed by an array of multiple regular hexagonal metamaterial units 11. The honeycomb metamaterial structure 3 is formed by an array of regular hexagonal metamaterial units 11, and the structure is more compact. Compared with the 3×3, 4×4 and other matrix arrangements in the prior art, the honeycomb metamaterial structure 3 has a lower cost and achieves higher power transmission efficiency.

[0050] See also Figure 1 and Figure 6-Figure 8 , the metamaterial unit 11 includes a regular hexagonal substrate 11-1, a regular hexagonal split ring 11-2 arranged on the substrate 11-1 and concentrically arranged with the substrate 11-1, and a circular open spiral coil 11-3 arranged inside the split ring 11-2; the split opening on the split ring 11-2 is connected to a tuning capacitor 11-4. In the above structure, the tuning capacitor 11-4 of the metamaterial unit 11 is used to adjust the real part of its relative magnetic permeability to be negative or near zero at an operating frequency of 13.56MHz. The metamaterial unit 11 with a negative real part of magnetic permeability can gather the magnetic field energy diverging from the edge, while the metamaterial unit 11 with a near-zero real part of magnetic permeability can strengthen the center strength of the magnetic field. The metamaterial unit 11 array of this embodiment has both near-zero and negative magnetic permeability metamaterials, so it can be called a hybrid metamaterial.

[0051] See also Figure 1 and Figure 6-Figure 8 , the split ring 11-2 can be a copper foil. According to the theory of equivalent circuit, in the resonant ring metamaterial structure, the size of the metal ring determines the size of the equivalent inductance, and the size of the opening of the metal ring determines the opening equivalent capacitance of the split ring 11-2 in the equivalent circuit. In addition, the line width, turn spacing and number of turns of the circular open spiral coil 11-3 also affect the inductance value and parasitic capacitance value of the metal coil. The split ring 11-2 and the circular open spiral coil 11-3 are in a parallel relationship in the equivalent circuit. Therefore, by changing the size of the metamaterial unit 11, the metamaterial unit 11 can achieve the effect of negative or near-zero magnetic permeability at the operating frequency of the wireless power transmission system. In order to increase the magnetic response, the metamaterial unit 11 of this embodiment is a hybrid metamaterial, such as Figure 11-Figure 12 As shown, at an operating frequency of 13.56 MHz (the gray vertical reference line in the figure), when the capacitance of the tuning capacitor 11-4 is 560 pF, the relative magnetic permeability is designed as a negative magnetic permeability metamaterial with a real part of -2.13 and an imaginary part of 0; when the capacitance of the tuning capacitor 11-4 is 680 pF, it is designed as a near-zero metamaterial with a real part of -0.06 and an imaginary part of 0.

[0052] See also Figure 1 , Figure 6-Figure 8 and Figure 11-Figure 12 , the real part of the relative magnetic permeability of the metamaterial represents the refractive index of electromagnetic energy, and the imaginary part represents the loss of electromagnetic waves. Compared with the metamaterials in the prior art, the real part of the magnetic permeability of this embodiment is less than -1 at an operating frequency of 13.56MHz, and has strong refractive properties for electromagnetic energy diverged from the edge. The real part of the magnetic permeability is close to zero, which strengthens the central magnetic field strength. The imaginary part is 0, indicating that its loss is small. After multiple optimizations, the physical size parameters of the final structure of the metamaterial unit 11 are as follows: the circumscribed circle radius LM of the substrate 11-1 is 35mm, that is, the horizontal length is 70mm, the side length AM of the substrate 11-1 is 34mm, the thickness of the substrate 11-1 is 1.6mm, the inner diameter dM of the circular open spiral coil 11-3 is 12mm, the line width W2 of the circular open spiral coil 11-3 is 2mm, the turn spacing S2 of the circular open spiral coil 11-3 is 1mm, and the number of turns of the circular open spiral coil 11-3 is 7.

[0053] See also Figure 6, the number of the metamaterial units 11 is 7, one metamaterial unit 11 is used as the central metamaterial unit, and the other six metamaterial units 11 are peripheral metamaterial units, and the six peripheral metamaterial units are distributed around the central metamaterial unit. In the above structure, 7 metamaterial units 11 can be used to form an array of honeycomb metamaterial structure 3. The size of the entire honeycomb metamaterial structure 3 is relatively small. A metamaterial array with too large size and area (such as 3×3, 4×4 matrix arrangement, etc.) will cause the internal resistance loss of the metamaterial unit 11 due to the induced current to be too large, which will lead to a decrease in the efficiency of the entire wireless power transmission (WPT) system. The honeycomb arrangement is used as the optimal array structure of the metamaterial.

[0054] See also Figure 6-Figure 7 The capacitance of the tuning capacitor 11-4 in the peripheral metamaterial unit is different from that of the tuning capacitor 11-4 in the central metamaterial unit. By adding two tuning capacitors 11-4 with different capacitances, a metamaterial unit 11 with negative and near-zero magnetic permeability is realized.

[0055] See also Figure 6 , the capacitance of the tuning capacitor 11-4 in the peripheral metamaterial unit is 560pF, and the capacitance of the tuning capacitor 11-4 in the central metamaterial unit is 680pF. The capacitance of the tuning capacitors 11-4 in the six peripheral metamaterial units is 560pF, which makes the resonant frequency of the metamaterial unit 11 lower than the operating frequency, achieving the effect that the real part of the magnetic permeability is -2.13 and the imaginary part is 0; the capacitance of the tuning capacitor 11-4 in the central metamaterial unit is 680pF, which makes the resonant frequency of the metamaterial unit 11 lower than the operating frequency, achieving the effect that the real part of the magnetic permeability is close to 0 and the imaginary part is 0.

[0056] See also Figure 1 and Figure 6-Figure 8 The substrate 11-1 is made of FR-4, and the split ring 11-2 and the circular open spiral coil 11-3 are arranged on the front of the substrate 11-1. The honeycomb metamaterial structure 3 is placed in the middle of the transmitting coil 1 and the receiving coil 2. Its function is: the honeycomb metamaterial structure 3 placed in the middle can completely cover the entire transmitting coil 1 and the receiving coil 2, so as to ensure that all the electromagnetic energy generated by the transmitting coil 1 passes through the honeycomb metamaterial structure 3, and the magnetic field energy is gathered to the receiving coil 2.

[0057] See also Fig.13 , the wireless power transmission system in the embodiment is simulated and analyzed using HFSS electromagnetic simulation software. When the transmitting coil 1 and the receiving coil 2 are 70 mm apart in a facing position, an optimal transmission efficiency of 87.34% is obtained at the operating frequency point = 13.56 MHz.

[0058] See also Figure 14-15The finite element simulation software was used to simulate the magnetic field intensity distribution from the transmitting coil 1 to the receiving coil 2 with and without the metamaterial unit 11 array. Figure 14-15 It can be seen that when the coil is at an operating frequency of 13.56MHz, the magnetic field intensity distribution near the receiver of the WPT system with the metamaterial unit 11 array (honeycomb metamaterial structure 3) is better than that of the WPT system without the metamaterial unit 11 array. Therefore, the addition of the honeycomb metamaterial structure 3 can aggregate the magnetic field energy, thereby generating a higher transmission efficiency.

[0059] See also Fig.16 , the change of transmission performance when the transmitting coil 1 and the receiving coil 2 move in position distance under this structure is explored, Fig.16 The data in the paper uses HFSS simulation software to simulate the transmission coil 1 and the receiving coil 2 as the transmission distance changes, and the honeycomb metamaterial structure 3 is always placed in the middle of the transmitting coil 1 and the receiving coil 2. The transmission efficiency between the transmitting coil 1 and the receiving coil 2 is obtained when the transmission distance is 40-140mm.

[0060] Depend on Fig.16 It can be seen that when the transmission distance between the transmitting coil 1 and the receiving coil 2 shifts from 70mm to 140mm, the transmission efficiency of the WPT system with or without the metamaterial unit 11 array decreases as the transmission distance increases. The transmission efficiency of the WPT with the addition of the metamaterial unit 11 array is significantly better than that without the metamaterial unit 11 array as the distance changes. At a transmission distance of 90mm, the difference in power transmission efficiency between the two reaches a maximum difference of 23.66%. It can be seen that the addition of the hybrid metamaterial unit 11 array (honeycomb metamaterial structure 3) in this embodiment can maintain a higher transmission efficiency at a longer transmission distance.

[0061] See also Fig.17 , the transmission distance between the transmitting coil 1 and the receiving coil 2 is fixed at 90mm. After adding the honeycomb metamaterial structure 3, the transmission efficiency of the WPT system has been above 50% when the horizontal offset range is: -30mm-30mm. And the average transmission efficiency is kept stable at 66.07% in the offset distance range of: -20mm to 20mm. Compared with the WPT system without the honeycomb metamaterial structure 3, the transmission efficiency of the WPT system with the honeycomb metamaterial structure 3 is much higher than the former.

[0062] See also Fig.18 The wireless power transmission system of this embodiment has an operating frequency of 13.56 MHz. The equivalent circuit diagram of the wireless power transmission system includes a transmitting coil circuit, a receiving coil circuit corresponding to the transmitting coil 1, and a load series circuit. Among them, V S is the operating frequency f s=13.56MHz power supply voltage, R L is the load, L 1 is the total inductance of the transmitting coil 1; L 2 is the total inductance of the receiving coil 2; C 1 , C 2 is the resonant capacitance of the transmitting coil 1 and the receiving coil 2, R 1 , R 2 are the resistances of the outer square and inner circle coils of the transmitting coil 1 and the receiving coil 2, respectively. The dotted box is the circuit of the honeycomb metamaterial structure 3, and each metamaterial unit 11 can be equivalent to a closed loop. S1 , L S2 , L S3 , L S4 , L S5 , L S6 , L S7 are the inductance of the metamaterial unit 11. S1 , C S2 , C S3 , C S4 , C S5 , C S6 , C S7 are the resonant capacitances corresponding to the metamaterial units 11. S1 , R S2 , R S3 , R S4 , R S5 , R S6 , R S7 They correspond to the internal resistance of the circular open spiral coil 11-3 respectively. The resonant frequency of the transmitting coil 1 and the receiving coil 2 is expressed as: M 12 is the mutual inductance between the transmitting coil 1 and the receiving coil 2, M 1Si(i＝1…7) represents the mutual inductance between the transmitting coil 1 and each metamaterial unit 11, M 2Si(i＝1…7) represents the mutual inductance between the receiving coil 2 and each metamaterial unit 11, is the mutual inductance between each metamaterial unit 11.

[0063] See also Figure 1-Figure 2 The working principle of the wireless power transmission system based on the honeycomb metamaterial and the outer square inner circle coil is:

[0064] The alternating current is converted from the transmitting coil 1 into electromagnetic waves and emitted to the air. The honeycomb metamaterial structure 3 can converge the electromagnetic waves emitted by the transmitting coil 1, and the receiving coil 2 receives the electromagnetic waves converged by the honeycomb metamaterial structure 3; the honeycomb metamaterial structure 3 can effectively cover the transmitting coil 1 and the receiving coil 2, improving the problem of low power transmission efficiency (PTE) due to the increase in transmission distance or lateral misalignment distance between the square spiral coil 5; by adopting an outer square inner circle coil, it has the characteristic of generating a uniform and strong magnetic field at the transmitting end, and the radiation area is large. The honeycomb metamaterial structure 3 is a near-zero or negative permeability electromagnetic metamaterial, which can improve the transmission distance and transmission efficiency of the wireless power transmission system. The near-zero and negative permeability electromagnetic structure has the characteristics of amplifying evanescent waves and improving the coupling characteristics of the resonant coil. It can not only make the energy of the transmitting coil 1 more focused on the receiving coil 2, improve the transmission efficiency and transmission distance of the wireless power transmission, but also has low cost and is easy to industrialize. The transmission distance is the distance between the transmitting coil 1 and the receiving coil 2.

[0065] See also Figure 1-Figure 2 and Figure 6-Figure 7 This embodiment adopts a spiral resonator coil with an outer square and an inner circular shape and a honeycomb array structure of a regular hexagonal metamaterial unit 11. Compared with the traditional planar square spiral coil 5, it can perform power transmission with very high transmission efficiency within a transmission distance of 60-100mm, and achieve a high power transmission efficiency of 87.34% at an operating frequency of 13.56MHz (the international RFID communication standard protocol frequency band) and a transmission distance of 70mm.

[0066] The wireless power transmission system of this embodiment has anti-misalignment performance, and its transmission efficiency can be kept above 50% when the transmission distance is fixed at 90mm and the horizontal misalignment range is between -30mm and 30mm. And the average transmission efficiency is kept stable at 66.07% in the misalignment distance range of -20mm to 20mm, achieving the characteristic of keeping the transmission efficiency fluctuating and stable. This anti-misalignment performance can be applied to real life.

[0067] The coil structure of the wireless power transmission system is simple and small in size. It is easy to install, convenient and flexible. It is suitable for practical applications and meets the requirements of the working frequency band specified by international standards. At the same time, the coil size and the added lumped capacitor can be adjusted to achieve the optimal performance of the entire wireless power transmission system. In the prior art, the metamaterial array arrangement mostly adopts a 3×3, 4×4 matrix arrangement, while the honeycomb metamaterial unit 11 array arrangement of this embodiment only requires 7 metamaterial units 11, so it has a lower cost to achieve higher power transmission efficiency.

[0068] The dielectric plate 4 of this embodiment can be a magnetizing material (such as ferrite or superconductor, etc.), which can gather the magnetic field energy diverged near the transmitting and receiving coils 2, increase the mutual inductance between the transmitting coil 1 and the receiving coil 2, and thus significantly improve the transmission efficiency of the system.

[0069] The above is a preferred embodiment of the present invention, but the embodiment of the present invention is not limited to the above content. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A wireless power transmission system based on honeycomb metamaterial and outer square inner circle coil, characterized in that: It includes a transmitting coil, a receiving coil and a honeycomb metamaterial structure arranged between the transmitting coil and the receiving coil; wherein, The transmitting coil and the receiving coil both include a dielectric plate and an outer square inner circle coil arranged on the dielectric plate; the outer square inner circle coil includes a square spiral coil and a circular spiral coil arranged inside the square spiral coil; the square spiral coil is connected to the circular spiral coil.

2. According to claim 1, a wireless power transmission system based on honeycomb metamaterial and outer square inner circle coil is characterized in that: The transmitting coil and the receiving coil are of printed circuit board structure. The outer square inner circle coil is a copper layer printed on a dielectric board, and the thickness of the copper layer is 1 ounce. The material of the dielectric board is FR-4. The number of turns of the square spiral coil and the circular spiral coil are both 6.

3. According to claim 1, a wireless power transmission system based on honeycomb metamaterial and outer square inner circle coil is characterized in that: The outer square inner circle coil is arranged on the front side of the dielectric plate, a copper clad layer is arranged on the back side of the dielectric plate, and two ends of the outer square inner circle coil are respectively connected to the copper clad layer through metallized vias arranged on the dielectric plate; a compensation chip capacitor is arranged on the copper clad layer.

4. The wireless power transmission system based on honeycomb metamaterial and outer square inner circle coil according to claim 3 is characterized in that: The copper clad layer includes a first microstrip line, a second microstrip line and a metal ground; the compensation patch capacitor is connected between the first microstrip line and the second microstrip line, the first microstrip line is connected to one end of the outer square inner circle coil; the other end of the outer square inner circle coil is connected to the metal ground; a radio frequency coaxial connector is provided on the side of the dielectric board, the ground end of the radio frequency coaxial connector is welded to the metal ground, and the excitation end of the radio frequency coaxial connector is connected to the second microstrip line.

5. The wireless power transmission system based on honeycomb metamaterial and outer square inner circle coil according to claim 1 is characterized in that: The honeycomb metamaterial structure is formed by a plurality of regular hexagonal metamaterial unit arrays.

6. A wireless power transmission system based on honeycomb metamaterial and outer square inner circle coil according to claim 5, characterized in that: The metamaterial unit comprises a regular hexagonal substrate, a regular hexagonal split ring arranged on the substrate and concentrically arranged with the substrate, and a circular open spiral coil arranged inside the split ring; the split opening on the split ring is connected to a tuning capacitor.

7. A wireless power transmission system based on honeycomb metamaterial and outer square inner circle coil according to claim 6, characterized in that: The number of the metamaterial units is 7, one metamaterial unit serves as a central metamaterial unit, and the remaining six metamaterial units serve as peripheral metamaterial units, and the six peripheral metamaterial units are distributed around the central metamaterial unit.

8. The wireless power transmission system based on honeycomb metamaterial and outer square inner circle coil according to claim 7, characterized in that: The capacitance of the tuning capacitor in the peripheral metamaterial unit is different from the capacitance of the tuning capacitor in the central metamaterial unit.

9. A wireless power transmission system based on honeycomb metamaterial and outer square inner circle coil according to claim 8, characterized in that: The capacitance of the tuning capacitor in the peripheral metamaterial unit is 560 pF, and the capacitance of the tuning capacitor in the central metamaterial unit is 680 pF.

10. The wireless power transmission system based on honeycomb metamaterial and outer square inner circle coil according to claim 1, characterized in that: The honeycomb metamaterial structure is placed right between the transmitting coil and the receiving coil.

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