A high-power microwave power density measurement method based on infrared imaging

Abstract

The present invention relates to a high-power microwave power density measurement method based on infrared imaging, which belongs to the technical field of power density measurement, and solves the measurement problem of large error in the calibration of the prior art. The method comprises: selecting a nonlinear medium as an absorbing material plate for high-power microwave measurement, turning on a high-power microwave source to be measured, irradiating the absorbing material plate, controlling the irradiation time of the high-power microwave source to be measured, ensuring the heat conversion of the high-power microwave energy by the absorbing material plate, and performing thermal imaging of the absorbing material plate that reaches thermal equilibrium through an infrared imager; according to the reflection coefficient, specific heat capacity, density of the absorbing material plate, thickness of the absorbing material plate, high-power microwave duty cycle, and irradiation area and temperature difference of the high-power microwave on the absorbing material plate, the power density of the high-power microwave source to be measured is determined. The present application can avoid repeated measurements and sampling points, thereby improving efficiency.

Description

Technical Field

[0001] The invention belongs to the technical field of power density measurement, and in particular relates to a high-power microwave power density measurement method based on infrared imaging. Background Art

[0002] At present, the measurement method for the power density of high-power microwaves is generally based on the antenna reception method, which uses a receiving antenna to set up on the high-power microwave radiation surface and connect it to an oscilloscope, receiver or spectrum analyzer to measure the power density of high-power microwaves. The basic principle is to use a radiation horn to radiate high-power microwaves into space, and use a receiving horn to receive a very small part of the power of the radiation field in the far field of radiation. After detection, the power is measured with a calibrated oscilloscope, and then the total radiation power is calculated by conversion. The main disadvantages of this technology and method are as follows: 1) A large amount of calibration is required; 2) Due to the reason 1), the error is inevitably increased. Summary of the invention

[0003] In view of the above analysis, the present invention aims to propose a high-power microwave power density measurement method based on infrared imaging to solve at least one of the above problems.

[0004] The purpose of the present invention is mainly achieved through the following technical solutions:

[0005] In one aspect, the present invention provides a high-power microwave power density measurement method based on infrared imaging, comprising:

[0006] The first step is to select a nonlinear (non-single-valued) medium to make an absorbing material plate for high-power microwave power density measurement as a high-power microwave absorbing device for high-power microwave measurement; use a high-power microwave source to irradiate the absorbing material plate, use the electromagnetic field to generate relaxation loss in the nonlinear medium, and use the principle that part of the electromagnetic energy is irreversibly converted into heat energy, and control the irradiation time t of the high-power microwave source on the absorbing material plate to ensure the maximum conversion of the nonlinear medium of the absorbing material to the high-power microwave, that is, to achieve thermal equilibrium of the absorbing material, and use an infrared imager to perform thermal imaging on the absorbing material plate that has reached thermal equilibrium after irradiation;

[0007] Further, for the infrared imaging unit pixel of the absorbing material, the temperature difference between the thermal equilibrium temperature (T1) of the unit pixel of the absorbing material and the initial temperature (T0) of the material (i.e., the initial temperature of the unit pixel), i.e., the temperature difference ΔT before and after high-power microwave irradiation, is calculated: ΔT=T1-T0;

[0008] Further: calculate the conversion heat of the absorbing material to high-power microwaves: Q = ΔT*m*c, where m is the material mass of the irradiated area of ​​the absorbing material plate, and c is the specific heat capacity of the absorbing material;

[0009] Furthermore, when the electromagnetic wave passes through the free space with impedance Z0 and is incident on the interface of the absorbing material with input impedance Zi, a part of it is reflected to the space W due to the impedance mismatch between air and material. 反 , and the other part enters the absorbing material as W 吸 , assuming that the electromagnetic wave energy reaching the absorbing material is W, then W = W 反 +W 吸 And W 吸 =η*W, η is the reflection coefficient of the absorbing material; the reflection coefficient η of the absorbing material can be expressed by the following formula:

[0010] η=(Z i -Z0) / (Z i +Z0)

[0011]

[0012] Where Z0 is the characteristic impedance of free space, Z i is the normalized input impedance of the absorbing material, μ0, ε0 are the magnetic permeability and dielectric constant of free space, μ i , ε i are the magnetic permeability and dielectric constant of the material, respectively.

[0013] Assume that W absorbed in the absorbing material is completely converted into heat Q, Q can be measured, and Q = ΔT*m*c, where m = ρ*v, where ρ is the density of the absorbing material, v = S*h, where S is the irradiation area of ​​the absorbing material by the high-power microwave strong field, and h is the thickness of the absorbing material plate, then

[0014] W=W 吸 / n=Q / n=ΔT*m*c / n=ΔT*ρ*S*h*c / n

[0015] From this we can calculate W, and the power density P is

[0016] P=W / S=ΔT*ρ*h*c / η

[0017] Finally, assuming that the duty cycle of the high-power microwave is one percent n, we can know that

[0018] P 高 =P / n

[0019] P 高 That is the power density of high-power microwave.

[0020] Compared with the prior art, the present invention can achieve at least one of the following technical effects:

[0021] Through infrared imaging technology, the high-power action area is instantly imaged on a specific absorbing material plate, avoiding the repeated measurement and sampling of traditional technologies; at the same time, the power density of the high-power microwave source can be obtained by combining the physical properties of the absorbing material plate (reflection coefficient, specific heat capacity, density, thickness, etc.) with the parameters of the infrared imaging pictures before and after the absorbing material plate is irradiated with high-power microwaves (temperature difference, imaging area, etc.) and the parameters of the high-power microwave source itself (duty cycle). This is simple, practical and efficient.

[0022] Other features and advantages of the present invention will be described in the following description, and part of them will become obvious from the description, or will be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures particularly pointed out in the written description and the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The drawings are only for the purpose of illustrating particular embodiments and are not to be considered limiting of the present invention. Like reference symbols denote like components throughout the drawings.

[0024] Figure 1 A flow chart of a high-power microwave power density measurement method based on infrared imaging provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0025] The preferred embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of the present invention and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not used to limit the scope of the present invention.

[0026] At present, traditional positioning technology in strong radiation electromagnetic environment is generally implemented through antennas or field strength meters. Generally, the search and exploration are carried out in the axis direction of the main beam of the radiation antenna, and the main beam of the radiation source is located in combination with the measurement data of the receiver or spectrum analyzer.

[0027] The power measurement of electromagnetic field is different from the usual measurement of electric power. It cannot be directly measured through voltage, current and resistance. The solution is to measure it indirectly through the various effects of electromagnetic field on other media or devices, that is, through the effects of the electric field, magnetic field, power or energy of the electromagnetic field on certain functional materials or devices, the electromagnetic field energy is converted into measurable physical quantities such as light, force, heat, electricity, etc., and the electromagnetic field power is calculated by detecting these measurable quantities. Therefore, it can be said that the power of electromagnetic field is measured through the electromagnetic field effect.

[0028] The present invention illustrates the effect of electromagnetic energy loss caused by simple harmonic wave field in typical medium due to the failure of change of polarization intensity P to keep up with change of external electric field E, and change of magnetization intensity M to keep up with change of external magnetic field H, which leads to conversion of electromagnetic field energy under strong field radiation into heat energy. By using infrared imaging technology to measure the temperature data of each pixel point of the imaged typical absorbing material medium under strong field irradiation, the spatial field strength of each point is inferred, to illustrate the technical principle and measurement principle of the present invention.

[0029] When an electromagnetic wave passes through a free space with an impedance of Z0 and is incident on a i When it reaches the interface of the absorbing material, part of it is reflected to the space W due to the impedance mismatch between air and material. 反 , and the other part enters the absorbing material as W 吸 , assuming that the electromagnetic wave energy reaching the absorbing material is W, then W = W 反 +W 吸 And Wabsorption = η*W, η is the reflection coefficient of the absorbing material; the reflection coefficient η of the absorbing material can be expressed by the following formula:

[0030] η=(Z i -Z0) / (Z i +Z0)

[0031]

[0032] Where Z0 is the characteristic impedance of free space, Z i is the normalized input impedance of the absorbing material, μ0, ε0 are the magnetic permeability and dielectric constant of free space, μ i , ε i are the magnetic permeability and dielectric constant of the material, respectively.

[0033] When the energy is W 吸 When electromagnetic waves propagate in nonlinear (non-single-valued) media, due to various damping effects, the rotation of the electric (magnetic) dipole cannot keep up with the changes in the external field, resulting in relaxation loss, and part of the electromagnetic energy is irreversibly converted into heat energy. For dielectric materials, dielectric loss is related to the frequency and intensity of the external field change, and the imaginary part of the relative dielectric constant reflects the loss characteristics of the dielectric; the average power density of dielectric loss under the action of a simple harmonic electric field is:

[0034]

[0035] For magnetic dielectric materials, under the action of an alternating external magnetic field, the average power density of magnetic dielectric loss is:

[0036]

[0037] If the conductivity of the medium is not 0, there is also conductivity loss in the medium. Under the action of a simple harmonic electric field, the average value of the conductivity loss power density is

[0038] Therefore, the calculation formula for the average total electromagnetic loss power density (or heating power density) of a simple harmonic field in a medium is:

[0039]

[0040] The first part of the formula is the conductivity loss of the medium, the second part is the dielectric loss, and the third part is the magnetic dielectric loss; where, is the average total electromagnetic loss power density, σ represents the electrical conductivity of the medium; E0 and H0 represent the peak values ​​of the external field strength and the magnetic field; ω=2πf represents the angular frequency, where f is the frequency of the external field strength; ε0 and ε″ represent the imaginary part of the dielectric constant in vacuum and the relative dielectric constant of dielectric properties, respectively; μ0 and μ″ represent the imaginary part of the magnetic permeability in vacuum and the relative permeability of magnetic medium properties, respectively.

[0041] From the above formula, it can be seen that the electromagnetic energy loss power density is determined by the imaginary part of the relative dielectric constant (relative magnetic permeability) of the medium, the conductivity, the external field frequency and the external field strength.

[0042] If a nonlinear dielectric material is used to make an absorbing material plate, and it is irradiated with a simple harmonic wave strong field, and the area per unit pixel of the thermal imaging image of the irradiated absorbing material plate is calculated, the area per unit pixel point s is obtained; then the irradiation energy of the simple harmonic wave strong field on the absorbing material medium unit pixel point s within the time period t is At this time, the heat converted by the absorbing material to the simple harmonic wave strong field Where h is the irradiation depth of the simple harmonic wave strong field on the absorbing material.

[0043] Assuming that W is completely converted into heat Q in the absorbing material, Q can be measured (Q = ΔT*m*c, where ΔT is the temperature difference of the material before and after irradiation, m = ρ*v, where ρ is the density of the absorbing material, v = S*h, where S is the irradiation area of ​​the absorbing material by the simple harmonic wave strong field, and c is the specific heat capacity of the material), then

[0044] W=W 吸 / n=Q / n=ΔT*m*c / n=ΔT*ρ*S*h*c / n

[0045] From this we can calculate W, and the power density P is

[0046] P=W / S=ΔT*ρ*h*c / η

[0047] As a typical strong electromagnetic radiation environment, the power measurement of high-power microwave electromagnetic environment also needs to be measured through electromagnetic field effects, and its electromagnetic field effects are characterized by electric field energy density and magnetic field energy density. The electromagnetic changes inside the medium after high-power microwave irradiation can be characterized by the temperature change of the medium.

[0048] Based on the above theory, the present application embodiment provides a high-power microwave power density measurement method based on infrared imaging, such as Figure 1 As shown, the following steps are included:

[0049] S1. Select a nonlinear dielectric absorbing material plate, turn on the high-power microwave source to be tested, and irradiate the absorbing material plate; and ensure the heat conversion and thermal balance of the high-power microwave on the absorbing material plate by controlling the irradiation time of the high-power microwave source to be tested.

[0050] S2. Collect an infrared image of the absorbing material plate using an infrared imager.

[0051] S3. The power density of the high-power microwave source can be obtained by measuring the physical properties of the absorbing material plate (reflection coefficient, specific heat capacity, density, thickness, etc.) combined with the parameter comparison of the infrared imaging pictures before and after the absorbing material plate is irradiated with high-power microwaves (temperature difference, imaging area, etc.) and the parameters of the high-power microwave source itself (duty cycle, etc.).

[0052] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A high-power microwave power density measurement method based on infrared imaging, characterized in that: include: Select a nonlinear medium as an absorbing material plate for high-power microwave measurement, turn on the high-power microwave source to be measured, irradiate the absorbing material plate, control the irradiation time of the high-power microwave source to be measured, ensure the absorbing material plate heat conversion of the high-power microwave energy, and perform thermal imaging of the absorbing material plate that has reached thermal equilibrium through an infrared imager; The power density of the high-power microwave source to be measured is determined based on the reflection coefficient, specific heat capacity, density of the absorbing material plate, thickness of the absorbing material plate, high-power microwave duty cycle, and irradiation area and temperature difference of infrared imaging of the absorbing material plate by the high-power microwave.

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