CN109088484B - Spatial Matching Method for Wireless Energy Transmission - Google Patents

Abstract

The invention relates to the field of microwave energy transmission, aiming at obtaining the maximum total energy transmission efficiency of a microwave energy transmission system, and a space matching method for energy transmission, comprising a transmitting antenna, a receiving antenna and a rectifying circuit; field matching, impedance matching and power matching are performed in sequence; The field matching includes polarization matching and aperture field matching. The energy transmission space matching technology provided by the invention improves the space electromagnetic wave transmission efficiency and the DC conversion efficiency of the rectenna by improving the field matching, impedance matching and power matching, and improves the overall energy transmission efficiency of the microwave energy transmission system; the field matching of the invention By matching the antenna aperture field distribution and the mutual coupling between the transmitting antenna and the receiving antenna, the problem of difficult full-scale simulation of complex and huge systems is solved.

Description

Spatial Matching Method for Wireless Energy Transmission

technical field

The invention relates to the field of microwave energy transmission, in particular to a space matching method for microwave wireless energy transmission.

Background technique

At present, energy transmission is mainly realized by erecting wires or cables, which requires a lot of manpower and material resources. During the transportation process, due to the loss of wires or cables, there is still a lot of energy waste. The microwave energy transmission technology converts electrical energy into microwaves for transmission, which reduces the erection of transmission lines, eliminates complicated wires, and makes living space tidy and has broad application prospects.

Microwave energy transmission (MPT) can realize long-distance transmission of energy and is an important wireless energy transmission method. In the wireless energy transmission method of microwave energy transmission, the transmitting antenna transmits energy into space in the form of microwaves, and at the receiving end, the rectenna receives and converts the microwave energy into DC energy. The microwave energy transmission system usually consists of three parts, the first part is the microwave source, including the microwave generator and the transmitting antenna, the second part is the free space of microwave propagation, and the third part is the rectifying antenna (Rectifying Antenna, or rectenna), which contains The receiving antenna and rectifier circuit, which can receive electromagnetic waves and convert them into direct current, are indispensable and important components in the microwave energy transmission system, and their performance has an important impact on the entire MPT system.

In the microwave energy transmission system, the overall efficiency of energy transmission is an important index to evaluate the quality of the microwave energy transmission system. The total efficiency of energy transmission, that is, the ratio of the DC output power to the transmitting power of the transmitting antenna, includes the space transmission efficiency and the DC conversion efficiency of the rectenna. For a radio frequency circuit, in order to obtain the maximum power for the circuit load, the impedance conjugate matching theorem needs to be satisfied, that is, the load impedance is equal to the conjugate value of the internal impedance of the excitation source. However, in the microwave energy transmission system, not only the impedance conjugate matching theorem in the rectenna needs to be considered, but also the propagation of microwaves in free space. Therefore, in order to improve the performance of the microwave energy transmission system, on the one hand, it is necessary to make the transmitted microwave energy reach the receiving antenna as much as possible; on the other hand, it is necessary to improve the performance of the rectifier antenna so that the load can output more DC energy.

In the entire microwave energy transmission system, the propagation of microwaves in free space is complex, and the propagation characteristics of the electromagnetic field, including the polarization, amplitude and phase distribution of the electromagnetic field, need to be considered to ensure that the receiving antenna can receive more energy. Furthermore, the receiving antenna is a rectifier antenna, followed by a radio frequency circuit with a rectifier diode, and the rectifier diode is a nonlinear device, so it is necessary to fully consider the working characteristics of the rectifier diode to ensure that the load can output maximum DC power.

Li Gang and Hu Xu's paper "Application of Generalized Scattering Parameters in Impedance Matching" proposes that in the RF circuit system, it is necessary to perform impedance matching on the load impedance to ensure that the maximum power is transmitted to the load impedance. The reference impedance in the scattering parameters corresponding to the traditional impedance matching theory is a real impedance, which can only adapt to the "equal resistance" matching condition. However, the reference impedance in the actual RF circuit system is generally a complex impedance, and the traditional matching theory of scattering parameters cannot be applied. In view of the above problems, the prior art solution 1 introduces the concept of generalized scattering parameters under conjugate matching conditions, compares the physical meanings of traditional scattering parameters and generalized scattering parameters, and explains the application of generalized scattering parameters through a two-port matching network example. There are 1) only considering the RF circuit impedance matching technology; 2) the circuit does not consider the operating characteristics of nonlinear devices;

In Georg Goubau and Felix Schweering, "Free space beam transmission" in Microwave Power Engineering, the spatial transmission characteristics of microwave energy with two apertures are theoretically derived. It is found that when the electromagnetic field of the transceiver antenna is in a conjugate distribution, the receiving antenna obtains the maximum RF power. There are 1) only the ideal aperture field of the transceiver antenna is considered, but the actual antenna situation and the mutual coupling relationship between the two antennas are not considered; 2) the circuit problem with a rectifier diode behind the rectifier antenna is not considered;

J.Xu,and D.S.Ricketts,"An efficient,watt-level microwave rectifier using an impedance compression network(ICN)with applications in outphasingenergy recovery systems", using impedance compression network technology, compared with traditional resistance compression network technology, can not only achieve The compression of the resistance can also realize the compression of the impedance, ensuring that the rectenna can achieve high-efficiency DC output under a wider range of input power. There are 1) only the power matching problem of the rectifier antenna is considered, and the matching problem of the free space of the transceiver antenna is not considered.

There is an urgent need for a new microwave wireless energy transmission technology to effectively solve the above problems.

SUMMARY OF THE INVENTION

The invention proposes a microwave wireless energy transmission space matching method, aiming at obtaining the maximum energy transmission total efficiency of the microwave energy transmission system. Based on the impedance conjugate matching, considering the matching situation of each part of the whole microwave energy transmission system, a spatial matching method is proposed. technology.

The technical scheme of the present invention is achieved as follows: a method for spatial matching of microwave wireless energy transmission, including a transmitting antenna, a receiving antenna and a rectifying circuit; it is characterized in that: field matching, power matching and impedance matching are performed in sequence; the field matching includes: Polarization matching and aperture field size and phase distribution matching.

Further, the field matching is performed by the aperture field distribution iterative method; the iterative method includes two steps: A transmits a microwave energy from the transmitting antenna, extracts the field distribution reaching the receiving antenna in the beam propagation direction, and takes the conjugate , calculate and obtain the target conjugate field to be achieved by the receiving antenna; B takes the conjugate field as the target, and adopts optimization algorithms (such as genetic algorithm, particle swarm algorithm, holographic method and neural network method, etc.) to optimize the surface structure or antenna of a single antenna The feeding amplitude and phase of the array make the field generated by the receiving antenna approach the target conjugate field to achieve field matching;

Further, the transmitting antenna and the receiving antenna adopt different polarizations, such as linear polarization, circular polarization, etc., to perform polarization matching.

Further, the power matching matches the received power of the receiving antenna through the input power of the optimal operating point of the rectifier circuit, that is, P _in =P _s , where Pin is the input power of the optimal operating point of the rectifier circuit; P _s is the receiving power of the receiving antenna _. The received power of the antenna.

Further, the impedance matching satisfies the impedance conjugate matching between the receiving antenna and the rectifier circuit:

其中，Z_in为整流电路的输入阻抗；Z_s为天线的源阻抗；Z_out为整流电路的输出阻抗；Z_L为负载阻抗。which is

Among them, Z _in is the input impedance of the rectifier circuit; Z _s is the source impedance of the antenna; Z _out is the output impedance of the rectifier circuit; Z _L is the load impedance.

Further, the aperture field matching includes the aperture field size, phase and power density distribution generated by the transmitting antenna and the receiving antenna. The transmitting antenna is composed of various forms of antennas or antenna arrays.

The invention provides a microwave wireless energy transmission space matching method, which improves the space electromagnetic wave transmission efficiency and the rectenna DC conversion efficiency by realizing field matching, power matching and impedance matching, thereby improving the overall energy transmission efficiency of the entire microwave energy transmission system, namely Energy transmission-conversion efficiency; the field matching of the present invention takes into account the mutual coupling effect of the transmitting antenna and the receiving antenna, and solves the difficulty of full-scale simulation of complex and huge systems by matching the polarization and aperture field distribution of the receiving antenna and the transmitting antenna. The problem.

Description of drawings

In order to explain the embodiments of the present invention or the technical solutions in the prior art more clearly, the following briefly introduces the accompanying drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only These are some embodiments of the present invention, and for those of ordinary skill in the art, other drawings can also be obtained from these drawings without any creative effort.

Figure 1: Schematic diagram of the simplified circuit of the rectenna;

Figure 2: Schematic diagram of the transceiver antenna of the microwave system;

Figure 3: Linear polarization/circular polarization receiving antenna array distribution;

Figure 4: Schematic diagram of the conversion efficiency of the rectifier circuit;

Figure 5: Axial ratio diagram of a circularly polarized antenna;

Figure 6: Rectifier circuit diagram;

Figure 7: Side view of linearly polarized receiving antenna unit structure;

Figure 8: The upper surface patch of the linearly polarized receiving antenna;

Figure 9: Linearly polarized receiving antenna floor;

Figure 10: Linear polarization receiving antenna feeder;

Figure 11: Side view of the structure of the circularly polarized receiving antenna unit;

Figure 12: Top surface patch of circularly polarized antenna;

Figure 13: Transmitting Antenna;

Figure 14: Artifact material diagram of the transmit antenna.

Among them: 1, patch; 2, dielectric board; 3, floor; 4, feeder; 5, horn antenna; 6, artificial material.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

The invention discloses a space matching method for microwave wireless energy transmission, comprising a transmitting antenna, a receiving antenna and a rectifying circuit; it is characterized in that: field matching, power matching and impedance matching are performed in sequence; the field matching includes polarization matching and aperture field matching .

Further, the field matching is performed by an iterative method of aperture field distribution; the iterative method includes two steps:

A: A microwave energy is emitted by the transmitting antenna, and the field distribution reaching the receiving antenna is extracted in the beam propagation direction, and the conjugate is taken, and the target conjugate field to be achieved by the receiving antenna is calculated and obtained;

B takes the conjugate field as the target, and adopts optimization algorithms, such as genetic algorithm, particle swarm algorithm, holography method and neural network method, etc., to optimize the surface structure of a single antenna or the feeding amplitude and phase of the antenna array, so that the field generated by the receiving antenna can be optimized. Approach the target conjugate field to achieve field matching;

Further, the transmitting antenna and the receiving antenna adopt different polarizations, such as linear polarization, circular polarization, etc., to perform polarization matching.

Further, the power matching matches the received power of the receiving antenna through the input power of the optimal operating point of the rectifier circuit, that is, P _in =P _s , where Pin is the input power of the optimal operating point of the rectifier circuit; P _s is the receiving power of the receiving antenna _. The received power of the antenna; the input power of the best operating point of the rectifier circuit mainly depends on the rectifier diode. By designing the corresponding matching branches to meet the power matching, the load can obtain the highest rectification conversion efficiency under the best power.

Further, as shown in the simplified schematic diagram of the rectifier circuit in FIG. 1 , the impedance matching satisfies the impedance conjugate matching between the receiving antenna and the rectifier circuit:

其中，Z_in为整流电路的输入阻抗；Z_s为天线的源阻抗；Z_out为整流电路的输出阻抗；Z_L为负载阻抗，其中整流二极管的非线性工作特性简化为Z阻抗矩阵。which is

Among them, Z _in is the input impedance of the rectifier circuit; Z _s is the source impedance of the antenna; _{Z out} is the output impedance of the rectifier circuit;

Further, the aperture field matching includes the aperture field size, phase and power density distribution generated by the transmitting antenna and the receiving antenna. The transmitting antenna is composed of various forms of antennas or antenna arrays.

Example 1:

A microwave energy transmission system, the operating frequency of the system is 2.45GHz. It consists of a transmitting antenna and a receiving antenna array. The diameter of the transmitting antenna array is 35 wavelengths, the diameter of the receiving antenna array is 50 wavelengths, and the distance is 980.4 wavelengths. The transmitting antenna array is linearly polarized. In order to achieve polarization Matching, the receiving antenna array in the corresponding rectenna is also linearly polarized.

As shown in the schematic diagram of the transceiver antenna of the microwave system in Fig. 2 and the schematic diagram of the transmitting antenna in Fig. 13, both the transmitting antenna and the receiving antenna adopt the linear polarization in the Y-axis direction. The transmitting antenna array emits a high-energy incoming wave from the horn antenna 5. 5. Two layers of artificial materials 6 are placed in front of them. As shown in Figure 14, each layer of artificial materials 6 is composed of a square frame structure. The distance between the two layers of artificial materials 6 is 46.25mm, and the distance from the bell mouth surface is 6mm. Uniformly distributed field of 74.23V/m.

Figure 3 Linear polarization/circular polarization receiving antenna array distribution, Figure 7 Linear polarization receiving antenna unit structure side view, Figure 8 Linear polarization receiving antenna upper surface patch, Figure 9 Linear polarization receiving antenna floor and Figure 10 As shown in the linearly polarized receiving antenna feed line, the receiving antenna unit is composed of two layers of dielectric plates 2, the relative permittivity of the upper and lower dielectric plates 2 is 2.65, and the thicknesses thereof are both 1 mm. The middle of the two-layer dielectric board 2 is a floor 3 with a "one"-shaped slot, the upper surface is a square patch 1, and there is a feeding branch behind it. Coupled to the upper patch 1, radiated out. The rectenna array is arranged according to the power density distribution of the transmitting antenna radiation at the receiving antenna aperture, and its aperture surface is non-uniformly distributed. ) to form an array whose array arrangement matches the distribution of the power density field; five types of units of different sizes are implemented by patch 1 antennas with different numbers and a spacing between antenna units of half a wavelength.

As shown in the rectifier circuit diagram in Fig. 6, according to the intercepted power distribution of the receiving antenna unit in the rectenna array, the rectifier circuit is designed with matching branches to achieve power matching and impedance matching. Using ADS software simulation, the rectification efficiency of the rectifier circuit under different powers is shown in Figure 4. When the input power is 60mW, the conversion efficiency of the rectifier circuit can reach 80%.

The transmission-conversion efficiency of this embodiment and the uniform array is shown in Table 1. It can be found that the energy transmission-conversion realized by the microwave energy transmission space matching technology proposed in the patent of the present invention The efficiency is 67.5%, which is much higher than the energy transfer-conversion efficiency obtained by the uniform array, which is 41.2%.

Table 1 Example 1 and Uniform Array Energy Transmission-Conversion Efficiency

Embodiment 2:

A microwave energy transmission system, the operating frequency of the system is 2.45GHz. It consists of a transmitting antenna array and a receiving antenna array. The diameter of the transmitting antenna array is 35 wavelengths, the diameter of the receiving antenna array is 50 wavelengths, and the distance is 980.4 wavelengths.

As shown in the transmitting antenna in Figure 13, the transmitting antenna adopts the linear polarization in the Y-axis direction. The transmitting antenna transmits a high-energy incoming wave from the horn antenna 5, and an artificial material 6 is placed in front of the horn antenna 5, as shown in Figure 14, It is composed of a square frame structure and realizes a uniform distribution field with an aperture field amplitude of 74.23V/m.

Figure 3 shows the distribution of linearly polarized/circularly polarized receiving antenna arrays, Figure 11 is a side view of the structure of the circularly polarized receiving antenna unit, and Figure 12 shows the patch on the upper surface of the circularly polarized antenna unit. It is composed of a dielectric plate 2 with a floor. The relative permittivity of the dielectric plate 2 is 2.65, the thickness is 1 mm, and the upper surface is a circular patch 1 with a cross groove at an angle of 45°. The energy is fed through the coaxial. . As shown in the axial ratio diagram of the circularly polarized antenna in Fig. 5, the receiving antenna adopts the circular polarization mode, and its axial ratio is 1.57dB. Since the transmitting antenna is linearly polarized and the receiving antenna is circularly polarized, there will be polarization mismatch, so the spatial transmission efficiency of the transmitting and receiving antenna is only 0.675.

Similarly, the rectenna array is arranged according to the power density distribution of the transmitting antenna radiation at the receiving antenna aperture, and its aperture surface is non-uniformly distributed. According to the power density distribution of the transmitting antenna radiation at the receiving aperture, five units of different sizes are selected. (cell) forms an array, and its array arrangement matches the power density field distribution; five different size units are realized by patch 1 antennas with different numbers and the antenna unit spacing is half a wavelength.

The structure of the rectifier circuit is the same as that of the first embodiment, and the ADS software is used to simulate the rectifier circuit.

The transmitting and receiving antenna arrays are all uniform arrays as a comparison. The energy transmission-conversion efficiency of this embodiment and the uniform array is shown in Table 2. It can be found that the energy transmission-conversion efficiency realized by the non-uniform array is 43.3%, which is far higher. The energy transfer-conversion efficiency obtained for the uniform array was 20.4%. Furthermore, by comparing the energy transfer-conversion efficiency of the polarization-matched non-uniform array in this embodiment with that of the first embodiment, it can be found that the energy transfer-conversion efficiency that satisfies polarization matching is 67.5%, which is much higher than that of the polarization-matched non-uniform array. The energy transfer-conversion efficiency obtained by the mismatch is 43.3%.

Table 2 Example 2 and Uniform Array Energy Transmission-Conversion Efficiency

The invention provides a microwave wireless energy transmission space matching method. By realizing field matching, impedance matching and power matching, the space electromagnetic wave transmission efficiency and the DC conversion efficiency of the rectenna are improved, thereby improving the energy transmission-conversion efficiency of the entire microwave energy transmission system. The invention takes into account the mutual coupling effect of the transmitting antenna and the receiving antenna, and solves the difficult problem of full-scale simulation of a complex and huge system by matching the polarization and aperture field distribution of the receiving antenna and the transmitting antenna.

Of course, without departing from the spirit and essence of the present invention, those skilled in the art should be able to make various corresponding changes and deformations according to the present invention, but these corresponding changes and deformations should all belong to the appendix of the present invention. the scope of protection of the claims.

Claims (3)

1. A microwave wireless energy transmission space matching method comprises a transmitting antenna, a receiving antenna and a rectifying circuit; the method is characterized in that: sequentially carrying out field matching, power matching and impedance matching; the field matching comprises polarization matching and aperture field matching; the field matching is carried out by a caliber field distribution iteration method;

the iterative method comprises two steps: a, transmitting microwave energy by a transmitting antenna, extracting field distribution reaching a receiving antenna in a beam propagation direction, extracting conjugation, and calculating to obtain a target conjugate field to be realized by the receiving antenna; b, taking the conjugate field as a target, optimizing the surface structure of a single antenna or the feeding amplitude and the phase of an antenna array by adopting an optimization algorithm, and enabling the field generated by the receiving antenna to approach the target conjugate field to realize field matching;

the transmitting antenna and the receiving antenna are composed of various types of antennas or antenna arrays; the optimization algorithm comprises a genetic algorithm, a particle swarm algorithm, a holographic method and a neural network method; the transmitting antenna and the receiving antenna adopt linear polarization or circular polarization for polarization matching; the power matching matches the received power of the receiving antenna through the input power of the optimum operating point of the rectifying circuit,

i.e. P_in＝P_sIn which P is_inInput power at the optimum operating point of the rectifier circuit; p_sIs the received power of the receive antenna.

2. The microwave wireless energy transmission space matching method according to claim 1, wherein: the impedance matching satisfies the impedance conjugate matching between the receiving antenna and the rectifying circuit:

namely, it is

And

wherein Z is_inIs the input impedance of the rectifying circuit; z_sIs the source impedance of the antenna; z_outIs the output impedance of the rectifying circuit; z_LIs the load impedance.

3. The microwave wireless energy transmission space matching method according to claim 1, wherein: the aperture field matching comprises the size, the phase and the power density distribution of aperture fields generated by the transmitting antenna and the receiving antenna.

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