Metasurface-based microwave power detector and method

Abstract

The application discloses a kind of microwave power detectors and methods based on super surface, belong to microwave detection field, this method includes metal resonator, F4B dielectric layer and metal backplate;The metal resonator is inlaid in the upper surface of F4B dielectric;The metal backplate is inlaid in the lower surface of F4B dielectric;The metal resonator is connected with metal backplate.This application solves the problem that the size of existing microwave detector is large, the detection angle is small, the polarization sensitivity is high and the cost is high.

Description

Technical Field

[0001] This invention belongs to the field of microwave detection, and particularly relates to a microwave power detector and method based on metasurface. Background Technology

[0002] In recent years, wireless power transmission technology has gained significant application value in fields such as electronic device charging, military energy transmission, and space-based solar power stations, becoming a research hotspot in both academic and industrial fields. The development and research of this technology can be broadly divided into two categories: one based on non-radiative near-field electromagnetic induction or strong magnetic resonance coupling, and the other based on radio frequency, microwave, and laser radiation. Among these, microwave power transmission is rapidly developing into a very promising technology due to its advantages such as long transmission distance, good stability, and strong high-power transmission capability. A microwave power transmission system includes a microwave transmitter, a propagation space, and a microwave receiver. To achieve maximum power processing efficiency, a high-performance microwave energy detector or sensor is crucial for ensuring the selection of a matched rectifier circuit.

[0003] Currently, the academic community has studied various typical microwave power detectors, including thermoelectric detectors, capacitive detectors, and coupled microwave power detectors. However, these energy harvesting modules are usually composed of waveguide antennas, which have drawbacks in practical applications, such as large size, small detection angle, high polarization sensitivity, and high cost. Furthermore, although commercial microwave power meters can be used to detect the power distribution of microwaves, they cannot be effectively applied to large-area power distribution detection. Fortunately, the emergence of energy-absorbing metasurfaces provides an ideal solution for this. Unlike absorbers, energy-absorbing metasurfaces absorb electromagnetic energy into the device and transfer it to the load for utilization with maximum efficiency. When the load is a resistor, the incident electromagnetic energy is converted into heat energy and then dissipated into the atmosphere through thermal radiation, eventually reaching thermal equilibrium. According to the law of conservation of energy, the heat generated on the load resistor directly reflects the energy of the incident microwave. Summary of the Invention

[0004] In view of the above-mentioned shortcomings in the prior art, the present invention provides a microwave power detector and method based on metasurface, which solves the problems of large size, small detection angle, high polarization sensitivity and high cost of existing microwave detectors.

[0005] To achieve the above-mentioned objectives, the present invention adopts the following technical solution: a microwave power detector based on metasurface, comprising a metal resonator, an F4B dielectric layer, and a metal backplate; the metal resonator is embedded on the upper surface of the F4B dielectric; the metal backplate is embedded on the lower surface of the F4B dielectric; and the metal resonator is connected to the metal backplate.

[0006] The beneficial effects of this invention are as follows: This invention proposes a microwave power detector that converts microwave energy into load resistor heat energy, and finally reflects the microwave power density through thermal sampling results. It has the performance advantages of high efficiency, large detection angle and polarization insensitivity, and provides a new design idea for large-area microwave power detection.

[0007] Furthermore, the metal resonator is a disk with a central circular hole; four orthogonally symmetrically distributed grooves surround the circular hole; a pair of circular hollow metal cylinders are provided near the edge of each groove; each pair of circular hollow metal cylinders are symmetrically distributed about the grooves; each circular hollow metal cylinder penetrates the F4B dielectric layer and is connected to the underlying metal backplate; a load resistor is welded between each pair of circular hollow metal cylinders; each load resistor is located on the metal backplate.

[0008] The beneficial effects of the above-mentioned further scheme are: the hole and groove structure of the metal resonator allows electromagnetic waves to resonate effectively within it, and converts them into resonant current to the greatest extent within the resonator; the centrally symmetrical structural distribution can achieve insensitivity to the polarization of the received electromagnetic waves.

[0009] Furthermore, the metal resonator is used to convert the received microwaves into a resonant current through resonance.

[0010] The F4B dielectric layer is used to maintain the insulation between the metal resonator and the metal backplate, support the entire microwave power detector, and at the same time dominate the impedance matching control of the microwave power detector to electromagnetic waves.

[0011] The metal backplate is used to reflect electromagnetic waves that have passed through the intermediate dielectric layer back into the device, prevent electromagnetic waves from being transmitted out of the microwave power detector, improve the absorption rate of electromagnetic waves by the microwave power detector, and also serve as a support for the load resistor on the back of the microwave power detector.

[0012] The beneficial effects of the above-mentioned further solutions are: achieving impedance matching for incident electromagnetic waves, optimizing the absorption efficiency of the device, preventing electromagnetic wave transmission, and further improving absorption efficiency.

[0013] This invention provides a microwave power detection method based on metasurfaces, comprising the following steps:

[0014] S1. Obtain the detection characteristic curve of the microwave power detector;

[0015] S2. Measure the temperature of the load resistor of the microwave power detector using a thermal detector;

[0016] S3. Based on the temperature and detection characteristic curve of the load resistor, the incident wave power density is obtained, and microwave power detection is completed.

[0017] The beneficial effects of this invention are as follows: This invention proposes a microwave power detection method, which converts microwave energy into load resistor heat energy, performs qualitative analysis on the load resistor heat energy, quantitatively calculates the transient temperature response in the wave-heat process, calculates the influence of different microwave power densities on the load resistor temperature, fits the relationship between the two, and realizes microwave power detection.

[0018] Furthermore, the expression for the detection characteristic curve in step S1 is:

[0019] f(x) = ax 2 +bx+c

[0020] Where f(x) is the detection characteristic curve, representing the incident wave power density; x is the temperature of the load resistor; and a, b, and c are the temperature correlation coefficients of the detection characteristic curve.

[0021] The beneficial effects of the above-mentioned further scheme are as follows: the detection characteristic curve shows the direct relationship between the incident wave power density and the resistance temperature, and the power density value of the detected incident wave can be obtained quickly through this curve. Attached Figure Description

[0022] Figure 1 This is a structural diagram of the microwave power detector of the present invention.

[0023] Figure 2 This is a schematic diagram of the incident situation of the microwave power detector in Embodiment 2 of the present invention.

[0024] Figure 3 This is a color diagram showing the absorption efficiency of the microwave power detector under different polarization angles and incident angles in Embodiment 2 of the present invention.

[0025] Figure 4 In Embodiment 2 of the present invention, the incident wave power density is 21.6 mW / cm². 2 Temperature distribution diagram of the time unit at the 10th second.

[0026] Figure 5 This is a graph showing the average temperature distribution of each component of the microwave power detector in Embodiment 2 of the present invention.

[0027] Figure 6 This is a graph showing the average temperature of the resistor under different incident wave power densities and the change curve of incident wave power density with resistor temperature in Embodiment 2 of the present invention.

[0028] Figure 7 This is a comparison chart of the temperature sampling experiment of the microwave power detector in Embodiment 2 of the present invention and the incident wave power density curves of simulation and testing. Detailed Implementation

[0029] 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.

[0030] Example 1

[0031] like Figure 1 As shown, in one embodiment of the present invention, a microwave power detector based on a metasurface includes a metal resonator, an F4B dielectric layer, and a metal backplate; the metal resonator is embedded on the upper surface of the F4B dielectric; the metal backplate is embedded on the lower surface of the F4B dielectric; and the metal resonator is connected to the metal backplate.

[0032] In this embodiment, Figure 1 The schematic diagram and prototype of the proposed electromagnetic energy detector are shown. Figure 1 As shown in (a) and 1(b), a device unit consists of three layers: a top periodic metal resonator, a middle F4B dielectric layer, and a bottom metal backplate. The top metal resonator is a disk with four grooves. To dissipate electromagnetic energy at the required material and location, eight metal vias are symmetrically distributed around the four grooves, penetrating the top and bottom metal patches. Every two adjacent metal vias are connected at the bottom layer by a 750Ω resistor. The resonant current generated at the top layer is guided through the metal channels to the resistor at the bottom layer, where the electrical energy is converted into heat. The metal resonator and the metal backplate are lossy copper with thicknesses of 0.15 mm and 0.035 mm, respectively, and a conductivity σ of 5.8 × 10⁻⁶. 7 The thickness, dielectric constant, and loss tangent of the F4B dielectric layer are 1.165 mm, 2.2, and 0.001, respectively. Figure 1 (c) and 1(d) are the top and bottom layers of a device array manufactured using printed circuit board technology, with dimensions of 216 × 216 mm. 2 (12×12 elements). The optimized dimensions of each element are: P = 18mm, l = 6mm, d = 0.8mm, w = 0.3mm, r1 = 1mm, r2 = 1.5mm, r3 = 6.7mm, r4 = 0.13mm.

[0033] The metal resonator is a disk with a central circular hole; four orthogonally symmetrically distributed grooves surround the circular hole; a pair of circular hollow metal cylinders are provided near the edge of each groove; each pair of circular hollow metal cylinders are symmetrically distributed about the groove; each circular hollow metal cylinder penetrates the F4B dielectric layer and is connected to the underlying metal backplate; a load resistor is welded between each pair of circular hollow metal cylinders; each load resistor is located on the metal backplate.

[0034] The metal resonator is used to convert the received microwaves into resonant current through resonance.

[0035] The F4B dielectric layer is used to maintain the insulation between the metal resonator and the metal backplate, support the entire microwave power detector, and at the same time dominate the impedance matching control of the microwave power detector to electromagnetic waves.

[0036] The metal backplate is used to reflect electromagnetic waves that have passed through the intermediate dielectric layer back into the device, prevent electromagnetic waves from being transmitted out of the microwave power detector, improve the absorption rate of electromagnetic waves by the microwave power detector, and also serve as a support for the load resistor on the back of the microwave power detector.

[0037] Example 2

[0038] This invention provides a microwave power detection method based on metasurfaces, comprising the following steps:

[0039] S1. Obtain the detection characteristic curve of the microwave power detector;

[0040] S2. Measure the temperature of the load resistor of the microwave power detector using a thermal detector;

[0041] S3. Based on the temperature and detection characteristic curve of the load resistor, the incident wave power density is obtained, and microwave power detection is completed.

[0042] The expression for the detection characteristic curve in step S1 is:

[0043] f(x) = ax 2 +bx+c

[0044] Where f(x) is the detection characteristic curve, representing the incident wave power density; x is the temperature of the load resistor; and a, b, and c are the temperature correlation coefficients of the detection characteristic curve.

[0045] In this embodiment, to demonstrate the absorption performance of the proposed microwave power detector, CSTMicrowave Studio was used to perform a full-wave electromagnetic simulation based on the finite element method. In the simulation settings, the boundary conditions along the Z-axis were open space, while periodic boundary conditions were used along the X and Y directions, numerically realizing an infinitely large array plane. This element is excited by a Floquet port and has TE and TM modes of polarization at the top boundary. These two modes correspond to a plane wave with an electric field parallel to the y-axis and x-axis, respectively. The angle between the electric field and the y-axis is defined as the angle between the wave propagation direction and the z-axis. The absorptivity is calculated using the formula A(ω) = 1 - R(ω) - T(ω), where R(ω) and T(ω) are the reflectivity and transmittance, respectively.

[0046] Figure 2 (a) shows the simulated absorption, reflection, and transmission spectra of the designed microwave power detector under normal incident conditions as a function of frequency. It can be observed that the detector's absorption frequency is at 5.8 GHz, with an absorption rate of 99.82%, and the TE and TM polarizations exhibit identical absorption and reflection spectra. To investigate the energy dissipation of each unit's incident electromagnetic wave by the four resistors, we named the two resistors on the X-axis R1 and R2, and the two resistors on the Y-axis R3 and R4. Figure 2 (b) shows the proportion of electromagnetic energy absorbed by each component within a unit. It can be seen that only 5.82% of the energy is dissipated in the metal and dielectric substrate, while a high percentage (94%) of the incident wave energy is collected by the resistors. For TE polarization, almost all the absorbed energy is dissipated evenly in the two resistors distributed along the x-axis, while the dissipation in resistors R3 and R4 distributed along the y-axis is close to zero. Similarly, for TM polarization, the absorbed energy is dissipated in resistors R3 and R4.

[0047] To assess the angular sensitivity of the microwave power detector to the incident angle of electromagnetic waves, as proposed in our research, we plotted color maps of the absorption efficiency under normal incidence with different polarizations and angles of incidence, and then plotted them separately on [the graphs]. Figure 3 From (a) and 3(b). Figure 3 As can be seen in (a), the detector exhibits fairly uniform and good absorption efficiency within the polarization range of 0° to 45°, which is attributed to the centrosymmetry of the structure. Figure 3 As shown in (b), under TE polarization, the absorption efficiency decreases slightly when the incident angle θ > 50°, but still remains above 90%. Therefore, this electromagnetic detector possesses both a large detection angle and polarization insensitivity.

[0048] The collected energy is converted into heat by the resistance; therefore, electromagnetic energy can be detected by establishing a mapping relationship between incident wave power or power density and temperature. To study the wave-thermal conversion effect in the device, COMSOL multiphysics simulation software was used to simulate wave-thermal coupling. In the simulation, the radiation source was set to a continuous wave at 5.8 GHz, and the initial power density of the incident wave was 21.6 mW / cm². 2 The ambient temperature is 298K. Electromagnetic waves of a certain power are incident on the detector and displayed as heat in the back-end resistor. This heat can be divided into two main parts. The first part is the total heat generated by the resistor, which can be calculated using the following formula:

[0049]

[0050] Where I is the current flowing through the resistor, t is the time the current flows, and ρ0, α, β, L, and S are the resistivity, temperature coefficient, temperature, length, and cross-sectional area of ​​the resistor, respectively. The second part is the heat consumed by the resistor, including heat conduction with the contact material, heat convection with the air, and heat radiation from itself. The instantaneous heat conduction equation following Fourier's law can be written as:

[0051]

[0052] Among them, T and C p ρ and k represent the transient temperature, heat capacity, density, and thermal conductivity of different materials. Calculation of heat convection with air:

[0053]

[0054] Among them, Γ, h, T f Let represent the boundary conditions, the convective heat transfer coefficient with respect to air, and the initial temperature. Let n be the direction of the normal outside the model boundary. Finally, thermal radiation can be expressed as:

[0055]

[0056] Where k b ε and ε are the Boltzmann constant and the radiation coefficient of the resistor, respectively.

[0057] To quantitatively evaluate the performance of this electromagnetic energy detector, we simulated the temperature distribution across the resistor under TE polarization, such as... Figure 4 As shown. It can be observed that resistors R1 and R2 are the brightest in color throughout the structure, indicating that they have the highest temperature. At 10 seconds, the temperature at the center of the resistors is 344K. The average temperature of each structural component was further investigated and is shown in... Figure 5In the graph, the red and orange lines represent the temperatures of the two resistors distributed along the x-axis, respectively. For TE polarization, these two curves highly overlap. The average temperature of the two resistors rapidly rises to 346.13 K within 0.1 seconds, then enters a dynamic equilibrium state, with temperature fluctuations within 2.2 K. As for the temperature of other parts of the detector, the average temperature remains below 302 K. This is because most of the electromagnetic energy is consumed by the two resistors, generating Joule heat, with only a very small portion of the electromagnetic energy consumed by the F4B dielectric and metal. For the TM polarized incident wave, the average temperature distribution curve of the detector is similar to that of the TE polarized wave.

[0058] The power of the incident wave has a direct impact on the temperature of the resistor. Therefore, it is necessary to study the relationship between different incident wave power densities and the resistor temperature. Figure 6 (a) shows the temperature versus time curves at different power densities. It is clear that, compared to... Figure 5 The situation is similar; the time it takes for resistors R1 and R2 to reach thermal equilibrium differs only slightly. When the incident wave power density increases from 15.43 mW / cm²... 2 Increased to 33.95 mW / cm 2 At that time, the resistor temperature increased from 330K to approximately 373K, and the temperature difference was almost constant at each moment. This is because the resonant current flowing through the resistor increases with the increase of the incident power density, thereby generating more Joule heat.

[0059] To accurately study the relationship between incident wave power density and resistance temperature, we plotted the power density versus temperature curve at the 10th second, as shown below. Figure 6 The points in (b) are shown. Based on these points, we fitted the curve shown in the figure, and it can be seen that the power density exhibits a good linear relationship with temperature. This curve can be represented by the following formula:

[0060] f(x) = ax 2 +bx+c. (5)

[0061] Where f(x) represents the incident wave power density, and x represents the resistance temperature. a, b, and c are -9.526 × 10⁻⁶. -4 1.11 and -247.6.

[0062] In this embodiment, as Figure 1 As shown in (c) and 1(d), a 12×12 array was constructed to demonstrate the feasibility of the detector. A horn antenna, supplied by a signal generator, was positioned at a far-field distance R to illuminate the array, ensuring plane wave excitation. The far-field distance R was defined based on the aperture of the horn antenna. The incident power density P on the array... D It can be represented as:

[0063]

[0064] Where G is the gain of the speaker, P in This refers to the input power. When the experimental equipment is in operation, the resistance temperature in the array backplane is sampled by an infrared thermal imager, such as... Figure 7 As shown in (a). However, due to limitations of the experimental equipment, a circularly polarized antenna was used to illuminate the array in the experiment. This resulted in the incident wave energy being uniformly dissipated across the resistors on the X and Y axes, so all resistors in the figure are highlighted. The curves showing the relationship between incident power density and temperature obtained through multiple samplings are plotted on [the graph]. Figure 7 (b) shows that the measurement results are basically consistent with the simulation results. The difference between the simulation and measurement results can be explained by the following three aspects. First, the 12×12 finite array has edge effects, thus it cannot achieve the effect of an infinite array in the simulation experiment, leading to changes in device performance. Second, the manufacturing tolerance of the array and the parameter differences between the simulated and experimental resistors also contribute to the error. Third, the influence of the experimental environment and experimental setup errors are also unavoidable.

Claims

1. A microwave power detector based on a metasurface, characterized in that, The device includes a metal resonator, an F4B dielectric layer, and a metal backplate. The metal resonator is embedded on the upper surface of the F4B dielectric. The metal backplate is embedded on the lower surface of the F4B dielectric. The metal resonator is connected to the metal backplate. The metal resonator is a disk with a central circular hole. Four orthogonally symmetrically distributed grooves surround the circular hole. A pair of hollow metal cylinders are provided near the edge of each groove. Each pair of hollow metal cylinders is symmetrically distributed about the groove. Each hollow metal cylinder penetrates the F4B dielectric layer and connects to the underlying metal backplate. A load resistor is welded between each pair of hollow metal cylinders. Each load resistor is located on the metal backplate.

2. The microwave power detector based on metasurface according to claim 1, characterized in that, The metal resonator is used to convert the received microwaves into resonant current through resonance. The F4B dielectric layer is used to maintain the insulation between the metal resonator and the metal backplate, support the entire microwave power detector, and at the same time dominate the impedance matching control of the microwave power detector to electromagnetic waves. The metal backplate is used to reflect electromagnetic waves that have passed through the intermediate dielectric layer back into the device, prevent electromagnetic waves from being transmitted out of the microwave power detector, improve the absorption rate of electromagnetic waves by the microwave power detector, and also serve as a support for the load resistor on the back of the microwave power detector.

3. A microwave power detection method using a metasurface-based microwave power detector as described in any one of claims 1-2, characterized in that, Includes the following steps: S1. Obtain the detection characteristic curve of the microwave power detector; S2. Measure the temperature of the load resistor of the microwave power detector using a thermal detector; S3. Based on the temperature and detection characteristic curve of the load resistor, the incident wave power density is obtained, and microwave power detection is completed.

4. The microwave power detector method based on metasurface according to claim 3, characterized in that, The expression for the detection characteristic curve in step S1 is: in, The detection characteristic curve represents the incident wave power density; The temperature of the load resistor; , and All are temperature correlation coefficients of the detection characteristic curves.

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