Reflectivity measurement method and system based on plano-concave quasi-optical resonant cavity

Abstract

The embodiment of the invention discloses a reflectivity measurement method and system based on a plano-concave quasi-optical resonant cavity. The method comprises the following steps: establishing a first plano-concave quasi-optical resonant cavity by using a spherical mirror and a plane mirror, adjusting the cavity length of the first plano-concave quasi-optical resonant cavity to enable the first plano-concave quasi-optical resonant cavity to resonate at a resonant frequency, and measuring the resonance performance; a second plano-concave quasi-optical resonant cavity is established through the spherical mirror and the sample plate to be measured, the cavity length of the second plano-concave quasi-optical resonant cavity is adjusted to the cavity length of the first plano-concave quasi-optical resonant cavity, the second plano-concave quasi-optical resonant cavity resonates at the resonant frequency, the resonance performance is measured, and the size of the sample plate to be measured is the same as that of the plane mirror; calculating the surface resistance of the sample plate to be measured according to the resonance performance of the first plano-concave quasi-optical resonant cavity and the resonance performance of the second plano-concave quasi-optical resonant cavity; calculating the reflection loss of the to-be-measured sample plate according to the surface resistance of the to-be-measured sample plate; and calculating the reflectivity of the sample plate to be measured according to the reflection loss of the sample plate to be measured.

Description

Technical Field

[0001] The present invention relates to the field of reflectivity detection methods. More specifically, it relates to a reflectivity measurement method and system based on a plano-concave quasi-optical resonator. Background Art

[0002] Reflectivity is one of the key parameters describing the reflection performance of metals, and the reflectivity of metals has received extensive attention in many application scenarios. In high-power gyrotrons, metal mirrors are used to reflect high-power signals. A decrease in the reflectivity of the metal mirror will lead to an increase in losses, and further result in greater thermal losses, which will limit the power handling capacity. The submillimeter radio telescope and the metal mirror form a quasi-optical transmission network, which is used to reflect the ultra-weak signals received from the radio telescope. A decrease in the reflectivity of the mirror directly leads to an increase in surface losses, thereby increasing the noise temperature. In high-quality resonators and quasi-optical transmission links, an ideal mirror with high reflectivity is very important, which directly affects the cavity loss of the resonator and the signal quality of the quasi-optical path. In the design of all-metal antennas, the metal reflectivity directly affects the antenna performance. In the microwave and millimeter-wave frequency bands, metals should have a performance close to total reflection, but due to factors such as material, surface roughness, operating frequency, use environment, and coating thickness, the reflection performance is not ideal. In order to reduce weight, some applications use composite materials plated with metal molds instead of metals to produce total reflection characteristics. For example, carbon fiber reflectors usually have different plies, and each layer of carbon fiber is neatly arranged in different directions. Weak isotropy or anisotropy will affect the electrical reflectivity. Therefore, it is necessary to measure the reflectivity of metals or high-reflectivity surfaces with high precision.

[0003] In the microwave and millimeter-wave frequency bands, the reflection method based on transmission forms such as waveguides, coaxial cables, and free space can measure the relative reflectivity, but as the frequency increases, signal leakage or multipath interference gradually becomes serious, resulting in poor accuracy. Measuring the relative reflectivity using the resonance method has relatively high accuracy. At low frequencies, the measurement of reflectivity using a closed resonator has been explored, but there is little research on reflectivity measurement based on the resonance method in the millimeter-wave frequency band. Summary of the Invention

[0004] The purpose of the present invention is to provide a reflectivity measurement method and system based on a plano-concave quasi-optical resonator to solve at least one of the problems existing in the prior art.

[0005] To achieve the above purpose, the present invention adopts the following technical solutions:

[0006] The first aspect of the present invention provides a reflectivity measurement method based on a plano-concave quasi-optical resonator, and the method includes:

[0007] A first plano - concave quasi - optical resonator is established using a spherical mirror and a plane mirror, and the cavity length of the first plano - concave quasi - optical resonator is adjusted so that the first plano - concave quasi - optical resonator resonates at the resonant frequency, and the resonant performance of the first plano - concave quasi - optical resonator is measured;

[0008] A second plano - concave quasi - optical resonator is established using the spherical mirror and the sample to be measured, and the cavity length of the second plano - concave quasi - optical resonator is adjusted to the cavity length of the first plano - concave quasi - optical resonator so that the second plano - concave quasi - optical resonator resonates at the resonant frequency, and the resonant performance of the second plano - concave quasi - optical resonator is measured. The size of the sample to be measured is the same as the size of the plane mirror;

[0009] The surface resistance of the sample to be measured is calculated according to the resonant performance of the first plano - concave quasi - optical resonator and the resonant performance of the second plano - concave quasi - optical resonator;

[0010] The reflection loss of the sample to be measured is calculated according to the surface resistance of the sample to be measured;

[0011] The reflectivity of the sample to be measured is calculated according to the reflection loss of the sample to be measured.

[0012] Optionally, measuring the resonant performance of the first plano - concave quasi - optical resonator includes: measuring the first quality factor of the first plano - concave quasi - optical resonator.

[0013] Optionally, measuring the resonant performance of the second plano - concave quasi - optical resonator includes: measuring the second quality factor of the second plano - concave quasi - optical resonator.

[0014] Optionally, the calculation formula for calculating the surface resistance of the sample to be measured according to the resonant performance of the first plano - concave quasi - optical resonator and the resonant performance of the second plano - concave quasi - optical resonator is:

[0015]

[0016] where Q total-1 is the first quality factor; Q total-2 is the second quality factor; f0 is the resonant frequency; ε0 is the vacuum permittivity; D is the cavity length; η0 is the free - space wave impedance.

[0017] Optionally, calculating the reflection loss of the sample to be measured according to the surface resistance of the sample to be measured includes:

[0018]

[0019] where R L is the reflection loss of the sample to be measured.

[0020] Optionally, calculating the reflectivity of the sample to be measured based on the reflection loss of the sample to be measured includes:

[0021] Γ = 1 - R L

[0022] where Γ is the reflectivity of the sample to be measured.

[0023] Optionally, the surface roughness of the plane mirror is less than or equal to 0.8 μm.

[0024] Optionally, the surface of the plane mirror is gold-plated.

[0025] Optionally, the material of the plane mirror includes copper with gold plating.

[0026] The second aspect of the present invention provides a reflectivity measurement system based on a plano-concave quasi-optical resonator, and the system includes:

[0027] A positioning and adjusting device for adjusting the cavity length of the first plano-concave quasi-optical resonator so that the first plano-concave quasi-optical resonator resonates at the resonant frequency, and the first plano-concave quasi-optical resonator includes a spherical mirror and a plane mirror;

[0028] A network analyzer for measuring the resonant performance of the first plano-concave quasi-optical resonator;

[0029] The positioning and adjusting device is further used to adjust the cavity length of the second plano-concave quasi-optical resonator to the cavity length of the first plano-concave quasi-optical resonator so that the second plano-concave quasi-optical resonator resonates at the resonant frequency, and the second plano-concave quasi-optical resonator includes the spherical mirror and the sample to be measured, and the size of the sample to be measured is the same as the size of the plane mirror;

[0030] The network analyzer is further used to measure the resonant performance of the second plano-concave quasi-optical resonator;

[0031] A first calculation unit for calculating the surface resistance of the sample to be measured according to the resonant performance of the first plano-concave quasi-optical resonator and the resonant performance of the second plano-concave quasi-optical resonator;

[0032] A second calculation unit for calculating the reflection loss of the sample to be measured according to the surface resistance of the sample to be measured;

[0033] A third calculation unit for calculating the reflectivity of the sample to be measured according to the reflection loss of the sample to be measured.

[0034] The beneficial effects of the present invention are as follows:

[0035] The technical solution of the present invention is to set up a plano-concave quasi-optical resonator to facilitate the placement of the sample to be measured, which has the advantages of sparse resonance frequencies, etc., is applicable to the millimeter-wave band, and solves the problem of measuring the reflectivity of metals and materials with high reflectivity in the microwave and millimeter-wave bands. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0037] Figure 1 The flowchart showing the method for measuring reflectivity based on a plano-concave quasi-optical resonator according to an embodiment of the present invention is shown.

[0038] [[ID=—12]] Figure 2 The structural diagram showing the system for measuring reflectivity based on a plano-concave quasi-optical resonator according to an embodiment of the present invention is shown. SPECIFIC EMBODIMENTS

[0039] To describe the present invention more clearly, the present invention will be further described below with reference to the embodiments and the accompanying drawings. Similar components in the drawings are denoted by the same reference numerals. Those skilled in the art should understand that the content specifically described below is illustrative rather than restrictive, and should not be used to limit the protection scope of the present invention.

[0040] In the microwave and millimeter-wave bands, the reflection method based on transmission forms such as waveguides, coaxial cables, and free space can measure the relative reflectivity, but as the frequency increases, signal leakage or multipath interference gradually becomes serious, resulting in poor accuracy. Measuring the relative reflectivity using the resonance method has relatively high accuracy. At low frequencies, the measurement of reflectivity using a closed resonator has been explored, but there is little research on the measurement of reflectivity based on the resonance method in the millimeter-wave band.

[0041] An embodiment of the present invention provides a method for measuring reflectivity based on a plano-concave quasi-optical resonator, as Figure 1 shown, the method includes: establishing a first plano-concave quasi-optical resonator using a spherical mirror and a plane mirror, and adjusting the cavity length of the first plano-concave quasi-optical resonator so that the first plano-concave quasi-optical resonator resonates at the resonance frequency, and measuring the resonance performance of the first plano-concave quasi-optical resonator; establishing a second plano-concave quasi-optical resonator using the spherical mirror and the sample to be measured, and adjusting the cavity length of the second plano-concave quasi-optical resonator to the cavity length of the first plano-concave quasi-optical resonator so that the second plano-concave quasi-optical resonator resonates at the resonance frequency, and measuring the resonance performance of the second plano-concave quasi-optical resonator, wherein the size of the sample to be measured is the same as the size of the plane mirror; calculating the surface resistance of the sample to be measured according to the resonance performance of the first plano-concave quasi-optical resonator and the resonance performance of the second plano-concave quasi-optical resonator; calculating the reflection loss of the sample to be measured according to the surface resistance of the sample to be measured; calculating the reflectivity of the sample to be measured according to the reflection loss of the sample to be measured.

[0042] In a specific example, a high-precision plane mirror is developed as a total reflection standard. A high-precision plane mirror of the same size and a sample to be tested are used with a spherical mirror to form a quasi-optical resonant cavity. The resonance loss of the two quasi-optical resonant cavities is measured, and the coupling loss, path loss, and diffraction loss are analyzed. By comparing and processing the two measurements, the reflection loss of the sample to be tested can be obtained, and then its reflectivity can be calculated.

[0043] This embodiment provides a plano-concave quasi-optical resonant cavity to facilitate placement of the sample to be tested, has advantages such as sparse resonant frequency, is suitable for the millimeter wave band, and solves the problem of measuring the reflectivity of metals and high-reflectivity materials in the microwave and millimeter wave bands.

[0044] In a possible implementation, measuring the resonance performance of the first plano-concave quasi-optical resonant cavity includes measuring a first quality factor of the first plano-concave quasi-optical resonant cavity.

[0045] In a specific example, the resonance performance of a quasi-optical cavity is measured. The quasi-optical cavity includes a spherical mirror and a plane mirror. The quasi-optical cavity system is connected and the cavity length is adjusted using a positioning adjustment device so that the quasi-optical cavity resonates at the frequency to be measured and has a high quality factor. The first resonant frequency f1 and the quality factor Q are measured using a network analyzer. total-1 .

[0046] In a specific example, taking the W-band (75GHz~110GHz) plano-concave quasi-optical resonant cavity system as an example, the positioning adjustment device adjusts the W-band quasi-optical cavity length so that the quasi-optical cavity resonates at the frequency to be measured, and the frequency has a high quality factor. The first resonant frequency f1=100.414GHz and the quality factor Q are measured by a network analyzer. total-1 =47811.

[0047] In a possible implementation, measuring the resonance performance of the second plano-concave quasi-optical resonant cavity includes measuring a second quality factor of the second plano-concave quasi-optical resonant cavity.

[0048] In a specific example, the resonance performance of a quasi-optical cavity is measured. The quasi-optical cavity includes a spherical mirror and a sample to be tested. The plane mirror is replaced by the sample to be tested to reconstruct the quasi-optical cavity. The cavity length is precisely adjusted using a positioning adjustment device so that the quasi-optical cavity resonates at the frequency to be tested. The second resonant frequency f2 and the quality factor Q are measured using a network analyzer. total-2 , and f1=f2.

[0049] In a specific example, taking a W-band (75 GHz to 110 GHz) plano-concave quasi-optical resonator system as an example, the flat mirror is replaced with the sample to be measured to form a W-band quasi-optical cavity. The cavity length is finely adjusted through a positioning and adjusting device so that the quasi-optical cavity resonates again at the frequency to be measured. The second resonance frequency f2 = 100.414 GHz and the quality factor Q are measured through a network analyzer. total-2 = 40104.

[0050] In a possible implementation, the calculation formula for the surface resistance of the sample to be measured according to the resonance performance of the first plano-concave quasi-optical resonator and the resonance performance of the second plano-concave quasi-optical resonator is:

[0051]

[0052] In the formula, Q total-1 is the first quality factor; Q total-2 is the second quality factor; f0 is the resonance frequency; ε0 is the vacuum permittivity; D is the cavity length; η0 is the free space wave impedance.

[0053] In a specific example,

[0054] Step 3: Calculate the surface resistance of the sample to be measured. The quality factor describes the loss characteristics of the resonator and is defined as the ratio of the energy stored in the resonator to the energy dissipated, as shown in formula (1). The larger the quality factor, the smaller the loss of the resonator.

[0055] Furthermore, formula (1) is:

[0056]

[0057] In the formula, Q is the loaded quality factor; ω0 = 2πf0; f0 is the resonance frequency; P total is the loss of the quasi-optical cavity.

[0058] Furthermore, formula (2) is:

[0059] P total = P r + P j + P c + P dif + P a

[0060] In the formula, P r is the cavity loss; P j is the geometric loss; P c is the coupling loss; P dif is the diffraction loss; P a is the path loss.

[0061] Furthermore, the loaded quality factor Q of the quasi-optical cavitytotal As shown in Formula (3). Further, Formula (3) is:

[0062]

[0063] Further, Formula (3) is transformed to obtain Formula (4). Further, Formula (4) is:

[0064]

[0065] Further, Formula (4) is transformed to obtain Formula (5). Further, Formula (5) is:

[0066]

[0067] Further, Formula (5) is transformed to obtain Formula (6). Further, Formula (6) is:

[0068]

[0069] In the formula,

[0070] Further, in the quasi-optical cavity composed of a spherical mirror and a plane mirror, the first quality factor Q total-1 As shown in Formula (7). Further, Formula (7) is:

[0071]

[0072] In the formula, P r-1 [[ID=F43]]is the cavity loss of the quasi-optical cavity composed of a spherical mirror and a plane mirror, P j-1 is the geometric loss of the quasi-optical cavity composed of a spherical mirror and a plane mirror, P c-1 is the coupling loss of the quasi-optical cavity composed of a spherical mirror and a plane mirror, P dif-1 is the diffraction loss of the quasi-optical cavity composed of a spherical mirror and a plane mirror, P a-1 is the path loss of the quasi-optical cavity composed of a spherical mirror and a plane mirror.

[0073] Further, in the quasi-optical cavity composed of a spherical mirror and a sample to be measured, the second quality factor Q total-2 As shown in Formula (8). Further, Formula (8) is:

[0074]

[0075] Further, P r-2 is the cavity loss of the quasi-optical cavity composed of a spherical mirror and a sample to be measured, P j-2The geometric loss of the quasi-optical cavity formed by the spherical mirror and the sample to be measured, P c-2 The coupling loss of the quasi-optical cavity formed by the spherical mirror and the sample to be measured, P dif-2 The diffraction loss of the quasi-optical cavity formed by the spherical mirror and the sample to be measured, P a-2 The path loss of the quasi-optical cavity formed by the spherical mirror and the sample to be measured.

[0076] Furthermore, by finely adjusting the cavity length to keep the two resonance frequencies the same, it can be considered that the geometric loss, coupling loss, diffraction loss, and path loss are the same in the two resonance states.

[0077] Furthermore, subtracting Equation (7) from Equation (8) gives Equation (9). Furthermore, Equation (9) is:

[0078]

[0079] In the formula, P r-2 is the cavity loss of the quasi-optical cavity formed by the spherical mirror and the sample to be measured; P r-1 is the cavity loss of the quasi-optical cavity formed by the spherical mirror and the plane mirror.

[0080] Furthermore, Equation (10) is:

[0081]

[0082] In the formula, P r-球 is the loss of the spherical mirror; P r-平 is the loss of the plane mirror.

[0083] Furthermore, Equation (11) is:

[0084]

[0085] In the formula, D is the cavity length, that is, the distance between the spherical mirror and the plane mirror, in meters; R s-球 is the surface resistance of the spherical mirror, in ohms; R s-平 is the surface resistance of the plane mirror, in ohms; f0 is the resonance frequency, in hertz; ε0 is the vacuum permittivity, 8.854E-12 F / m; η0 is the free space wave impedance, η0 = 377 ohms.

[0086] Furthermore, at the same resonance frequency, it can be considered that the losses of the spherical mirror are the same in the two resonance states. Combining Equation (9) and Equation (11) gives Equation (12). Furthermore, Equation (12) is:

[0087]

[0088] In the formula, Q r-待测is the equivalent quality factor of the sample to be measured.

[0089] Furthermore, the high-precision flat mirror is used as the reflection reference standard. Considering its loss is very small and regarded as 0. Corresponding to Q r-平 is infinite, then formula (12) is transformed into formula (13). Furthermore, formula (13) is:

[0090]

[0091] Furthermore, substitute Q total-1 and Q total-2 into formula (13) and calculate to obtain Q r-待测 .

[0092] Furthermore, according to formula (14), the surface resistance R s-待测 of the sample to be measured can be obtained.

[0093] Furthermore, formula (14) is:

[0094]

[0095] In the formula, Q r-待测 can be obtained through formula (13).

[0096] In a specific example, taking the W-band (75 GHz - 110 GHz) plano-concave quasi-optical resonator system as an example, substitute Q total-1 = 47811 and Q total-2 = 40104 into formula (14) to solve the surface resistance of the sample to be measured.

[0097]

[0098] In the formula, f0 is 100.414 GHz; ε0 is 8.854E-12 F / m; D is the cavity length, which is inversely obtained from the resonance frequency and the spherical mirror curvature radius as 63.3675 mm; η0 is the free space wave impedance, 377 Ω.

[0099] Furthermore, the calculated surface resistance R s-待测 of the sample to be measured is 0.1011 Ω.

[0100] In a possible implementation manner, calculating the reflection loss of the sample to be measured according to the surface resistance of the sample to be measured includes:

[0101]

[0102] In the formula, R L is the reflection loss of the sample to be measured.

[0103] In a specific example, taking a plano-concave quasi-optical resonator system in the W-band (75 GHz to 110 GHz) as an example, the reflection loss of the sample to be measured is

[0104] In a possible implementation, the calculating the reflectivity of the sample to be measured according to the reflection loss of the sample to be measured includes:

[0105] Γ = 1 - R L

[0106] where Γ is the reflectivity of the sample to be measured.

[0107] In a specific example, taking a plano-concave quasi-optical resonator system in the W-band (75 GHz to 110 GHz) as an example, the reflectivity of the sample to be measured is Γ = 1 - R L = 99.89%.

[0108] In a possible implementation, the surface roughness of the plane mirror is less than or equal to 0.8 μm.

[0109] In a possible implementation, the surface of the plane mirror is gold-plated.

[0110] In a possible implementation, the material of the plane mirror includes copper with gold plating.

[0111] Another embodiment of the present invention provides a reflectivity measurement system based on a plano-concave quasi-optical resonator. As Figure 2 shown, the system includes: a positioning and adjusting device for adjusting the cavity length of the first plano-concave quasi-optical resonator so that the first plano-concave quasi-optical resonator resonates at the resonant frequency, the first plano-concave quasi-optical resonator including a spherical mirror and a plane mirror; a network analyzer for measuring the resonant performance of the first plano-concave quasi-optical resonator; the positioning and adjusting device is further used to adjust the cavity length of the second plano-concave quasi-optical resonator to the cavity length of the first plano-concave quasi-optical resonator so that the second plano-concave quasi-optical resonator resonates at the resonant frequency, the second plano-concave quasi-optical resonator including the spherical mirror and the sample to be measured, the size of the sample to be measured being the same as the size of the plane mirror; the network analyzer is further used to measure the resonant performance of the second plano-concave quasi-optical resonator; a first calculation unit for calculating the surface resistance of the sample to be measured according to the resonant performance of the first plano-concave quasi-optical resonator and the resonant performance of the second plano-concave quasi-optical resonator; a second calculation unit for calculating the reflection loss of the sample to be measured according to the surface resistance of the sample to be measured; a third calculation unit for calculating the reflectivity of the sample to be measured according to the reflection loss of the sample to be measured.

[0112] In a specific example, a relative reflectivity measurement system based on a plano-concave quasi-optical resonator includes a network analyzer, a plano-concave quasi-optical resonator, and a positioning and adjusting device. The plano-concave quasi-optical resonator includes a spherical mirror and a plane mirror, and the distance between the spherical mirror and the plane mirror is the cavity length. The plane mirror is required to adopt an optical mirror processing technology, with a gold-plated surface and a surface roughness not greater than 0.8 μm. The size of the sample to be measured should be the same as that of the plane mirror.

[0113] In a specific example, taking the W-band (75 GHz - 110 GHz) plano-concave quasi-optical resonator system as an example, the W-band plano-concave quasi-optical resonator relative reflectivity measurement system consists of a 3 mm network analyzer, a W-band spherical mirror, a W-band plane mirror, a positioning and adjusting device, etc. The W-band plane mirror is made of copper with a gold-plated surface, adopting an optical mirror processing technology and a surface finish of 0.8 μm. The sample to be measured is required to have the same size as the plane mirror.

[0114] In this embodiment, by setting up a plano-concave quasi-optical resonator, it is convenient to place the sample to be measured, and it has advantages such as sparse resonance frequencies, is applicable to the millimeter-wave band, and solves the measurement problems of the reflectivity of metals and high-reflectivity materials in the microwave and millimeter-wave bands.

[0115] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by terms such as "upper" and "lower" is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention. Unless otherwise clearly specified and defined, the terms "installed", "connected", and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0116] It should also be noted that in the description of the present invention, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variation thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "comprising an..." does not exclude the presence of additional identical elements in the process, method, article or device comprising said element.

[0117] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, rather than limitations on the implementation manners of the present invention. For those of ordinary skill in the art, based on the above description, other different forms of changes or variations can be made. It is impossible to list all the implementation manners here. Any obvious changes or variations derived from the technical solutions of the present invention still fall within the protection scope of the present invention.

Claims

1. A method for measuring reflectivity based on a plano-concave quasi-optical resonator, characterized in that The method includes: Establishing a first plano - concave quasi - optical resonator using a spherical mirror and a plane mirror, and adjusting the cavity length of the first plano - concave quasi - optical resonator so that the first plano - concave quasi - optical resonator resonates at the resonant frequency, and measuring the resonant performance of the first plano - concave quasi - optical resonator; Establishing a second plano - concave quasi - optical resonator using the spherical mirror and the sample to be measured, and adjusting the cavity length of the second plano - concave quasi - optical resonator to the cavity length of the first plano - concave quasi - optical resonator so that the second plano - concave quasi - optical resonator resonates at the resonant frequency, and measuring the resonant performance of the second plano - concave quasi - optical resonator, where the size of the sample to be measured is the same as the size of the plane mirror; Calculating the surface resistance of the sample to be measured according to the resonant performance of the first plano - concave quasi - optical resonator and the resonant performance of the second plano - concave quasi - optical resonator; Calculating the reflection loss of the sample to be measured according to the surface resistance of the sample to be measured; Calculating the reflectivity of the sample to be measured according to the reflection loss of the sample to be measured.

2. The reflectivity measurement method based on a plano - concave quasi - optical resonator according to claim 1, characterized in that Measuring the resonant performance of the first plano - concave quasi - optical resonator includes: measuring the first quality factor of the first plano - concave quasi - optical resonator.

3. The reflectivity measurement method based on a plano - concave quasi - optical resonator according to claim 2, characterized in that Measuring the resonant performance of the second plano - concave quasi - optical resonator includes: measuring the second quality factor of the second plano - concave quasi - optical resonator.

4. The reflectivity measurement method based on a plano - concave quasi - optical resonator according to claim 3, characterized in that The calculation formula for calculating the surface resistance of the sample to be measured according to the resonant performance of the first plano - concave quasi - optical resonator and the resonant performance of the second plano - concave quasi - optical resonator is: Where, Q total-1 is the first quality factor; Q total-2 is the second quality factor; f0 is the resonance frequency; ε0 is the permittivity of free space; D is the cavity length; η0 is the free - space wave impedance.

5. The reflectivity measurement method based on a plano - concave quasi - optical resonator according to claim 4, characterized in that Calculating the reflection loss of the sample to be measured according to the surface resistance of the sample to be measured includes: Wherein, R L is the reflection loss of the sample to be measured.

6. The reflectivity measurement method based on a plano - concave quasi - optical resonator according to claim 5, characterized in that Calculating the reflectivity of the sample to be measured according to the reflection loss of the sample to be measured includes: Γ = 1 - R L In the formula, Γ is the reflectivity of the sample to be measured.

7. The reflectivity measurement method based on a plano-concave quasi-optical resonator according to claim 6, wherein The surface roughness of the plane mirror is less than or equal to 0.8μm.

8. The reflectivity measurement method based on a plano-concave quasi-optical resonator according to claim 7, wherein 9. The reflectivity measurement method based on a plano-concave quasi-optical resonator according to claim 8, wherein The surface of the plane mirror is gold - plated.

10. A reflectivity measurement system based on a plano-concave quasi-optical resonator, characterized in that, The material of the plane mirror includes copper gold - plated. The system includes: A positioning and adjusting device for adjusting the cavity length of the first plano - concave quasi - optical resonator so that the first plano - concave quasi - optical resonator resonates at the resonant frequency, where the first plano - concave quasi - optical resonator includes a spherical mirror and a plane mirror; A network analyzer for measuring the resonant performance of the first plano - concave quasi - optical resonator; The positioning and adjusting device is further used to adjust the cavity length of the second plano - concave quasi - optical resonator to the cavity length of the first plano - concave quasi - optical resonator so that the second plano - concave quasi - optical resonator resonates at the resonant frequency, where the second plano - concave quasi - optical resonator includes the spherical mirror and the sample to be measured, and the size of the sample to be measured is the same as the size of the plane mirror; A network analyzer, which is also used to measure the resonance performance of the second plano-concave quasi-optical resonator; A first calculation unit, which is used to calculate the surface resistance of the to-be-tested sample according to the resonance performance of the first plano-concave quasi-optical resonator and the resonance performance of the second plano-concave quasi-optical resonator; A second calculation unit, which is used to calculate the reflection loss of the to-be-tested sample according to the surface resistance of the to-be-tested sample; A third calculation unit, which is used to calculate the reflectivity of the to-be-tested sample according to the reflection loss of the to-be-tested sample.

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