A method and system for testing high power millimeter wave absorption load reflectivity

Abstract

This invention discloses a method and system for testing the reflectivity of a high-power millimeter-wave absorbing load, relating to the field of high-power millimeter-wave power testing technology. The method includes the following steps: connecting the absorbing load to the back end of a mode converter, and measuring the frequency domain curve S of the reflection from the absorbing load at this time using a vector network analyzer. 11 Using the discrete inverse Fourier transform, the frequency domain curve S 11 Transforming to the time domain yields the time-domain curve S 11 (t); Determine the time-domain location of the reflection peak caused by the absorption load, gating the reflection peak caused by the absorption load to filter out the reflection waveform caused by the impedance mismatch of the mode converter, and obtain the gated time-domain curve S. 11 * (t); The gated time-domain curve S is obtained by using Discrete Fourier transform. 11 * (t) is transformed to the frequency domain to obtain the frequency domain curve S of the absorbed load. 11 * The reflectivity Γ of the absorbing load is then calculated. The method for testing the reflectivity of the absorbing load proposed in this invention is simple to operate, has a simple system link, and high testing accuracy.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high-power millimeter wave power test, in particular to a high-power millimeter wave absorption load reflectivity test method and system. BACKGROUND

[0002] In the experimental research of magnetic confinement thermonuclear fusion, high-power millimeter waves are needed for electron cyclotron resonance heating. High-power millimeter wave sources are usually a kind of electric vacuum device, named gyrotron. The millimeter wave power output by the gyrotron is usually as high as hundreds of kilowatts or even megawatts, and an absorption load is usually used to absorb and test the output millimeter wave power. In order to accurately evaluate the performance of the absorption load and analyze the uncertainty of the power test, it is required to test the reflectivity of the absorption load. The reflectivity of the absorption load is usually low, and the test result is often affected by the impedance mismatch in the test link, so the test is difficult.

[0003] At present, the existing high-power millimeter wave absorption load reflectivity test method is as shown in FIG. 1. Figure 4 Through exciting a Gaussian beam or HE 11 mode at port 1, the electromagnetic wave is reflected to port 2 and transmitted to port 3 through the dielectric sheet beam splitter. The reflected wave at port 2 can be measured by a 4-port power meter. During the test, a short-circuit plate is first connected at port 2, and the reading of the 4-port power meter at this time is read as W1. Then, the absorption load (DUT) to be tested is connected to port 2, and the reading of the power meter at this time is read as W2. The reflectivity of the absorption load to be tested at port 2 can be obtained by the ratio of W2 to W1.

[0004] Firstly, since the high-power millimeter wave source usually outputs TEM 00 mode or HE 11 mode, the existing conventional voltage standing wave ratio test method based on a vector network analyzer and a rectangular waveguide basic mode TE 10 mode cannot be directly applied to the test of the reflectivity of the high-power millimeter wave absorption load due to the difference in output mode.

[0005] Secondly, the existing high-power millimeter wave absorption load reflectivity test method has the disadvantages of more test equipment, complicated test steps, unstable power meter operation, and low test precision of reflectivity caused by impedance mismatch between devices.

[0006] Finally, since the reflectivity of the absorption load is usually low, the impedance mismatch in the test link will seriously affect the test result of the reflectivity.

[0007] In view of these shortcomings, the present application proposes a high-power millimeter wave absorption load reflectivity test method. SUMMARY

[0008] The present application aims at providing a high-power millimeter wave absorption load reflectivity test method and system, based on discrete Fourier transform (DFT and DIFT), gating filtering impedance mismatch in the test link in time domain, using a vector network analyzer and a mode converter to test the reflectivity of the absorption load, solving the problem of low test accuracy of reflectivity caused by impedance mismatch in the existing test link.

[0009] The technical solutions adopted by the present application are as follows:

[0010] The present application is a high-power millimeter wave absorption load reflectivity test method, comprising the following steps:

[0011] After connecting the absorption load to the back end of the mode converter, the frequency domain curve S 11 of the absorption load reflected at this time is measured by the vector network analyzer.

[0012] The frequency domain curve S 11 is transformed to time domain by using discrete inverse Fourier transform to obtain the time domain curve S 11 (t), and the pulse condition of the time domain curve S 11 (t) is observed.

[0013] According to the physical size of the test link, the time domain position of the reflection peak caused by the absorption load is determined, the reflection peak caused by the absorption load is gated, and the reflection waveform caused by the impedance mismatch of the mode converter is filtered out to obtain the gated time domain curve S 11 * (t).

[0014] The gated time domain curve S 11 * (t) is transformed to frequency domain by using discrete Fourier transform to obtain the frequency domain curve S 11 * of the absorption load, and the reflectivity Γ of the absorption load is further calculated, and the formula is:

[0015]

[0016] Further, the frequency domain curve S 11 is transformed to time domain by using discrete inverse Fourier transform to obtain the time domain curve S 11 (t), and the specific formula is:

[0017]

[0018] Furthermore, based on the physical dimensions of the test link, the time-domain location of the reflection peak caused by the absorbing load is determined, that is, the time t it takes for the high-power millimeter wave reflected by the absorbing load to reach the vector network analyzer is determined, t = 2L / c, where c is the speed of light and L is the distance from the reference port of the vector network analyzer to the absorbing load.

[0019] Furthermore, the reflection peak caused by the absorption load is gated using a window function win, as shown in the formula:

[0020] S 11 * (t)=S 11 (t)*win.

[0021] Furthermore, after gating the reflection peak caused by the absorption load, the gated time-domain curve S 11 * (t) Transforming to the frequency domain: The specific process of transforming to the frequency domain using the Discrete Fourier Transform is achieved through the following formula:

[0022]

[0023] A test system for the reflectivity of a high-power millimeter-wave absorbing load includes a vector network analyzer, a spread spectrum module, a mode converter, and an absorbing load connected in sequence.

[0024] Vector network analyzer for testing the frequency domain curves S of mode converters and absorbed loads. 11 ;

[0025] The spread spectrum module connects to the vector network analyzer to extend the frequency range that the vector network analyzer can test.

[0026] The mode converter connects to the spread spectrum module and the absorption load to realize the rectangular waveguide TE of the spread spectrum module port. 10 Mode towards HE 11 Mode or Gaussian beam conversion; the mode converter is a corrugated waveguide or corrugated horn.

[0027] Absorbing loads are loads that absorb and partially reflect high-power millimeter-wave power.

[0028] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0029] This invention relates to a method and system for testing the reflectivity of a high-power millimeter-wave absorbing load. Based on discrete Fourier transform pairs, impedance mismatch in the test link is filtered out in the time domain. The reflectivity of the absorbing load is tested using a vector network analyzer and a mode converter. The method for testing the reflectivity of the absorbing load proposed in this invention is simple to operate, has a simple system link, and high test accuracy. Attached Figure Description

[0030] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort, wherein:

[0031] Figure 1 This is a flowchart of the testing method of the present invention;

[0032] Figure 2 This is a schematic diagram of the time-domain curve of the present invention;

[0033] Figure 3 This is a schematic diagram of the test link structure of the test system of the present invention;

[0034] Figure 4 This diagram illustrates the existing testing method for the reflectivity of high-power millimeter-wave absorbing loads. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only for explaining the invention and are not intended to limit the invention; that is, the described embodiments are merely some embodiments of the invention, and not all embodiments. The components of the embodiments of the invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0036] It should be noted that the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0037] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0038] Example 1

[0039] like Figure 1 As shown, this invention is a method for testing the reflectivity of a high-power millimeter-wave absorbing load. The specific steps are as follows:

[0040] The absorption load is connected to the back end of the mode converter, and the frequency domain curve S of the reflection from the absorption load is measured using a vector network analyzer. 11 ;

[0041] Using the Discrete Inverse Fourier Transform (DIFT), the frequency domain curve S 11 Transforming to the time domain yields the time-domain curve S 11 (t), the specific formula is:

[0042]

[0043] Time-domain curve S 11 The pulse case of (t), such as Figure 2 As shown, Figure 2 The reflected waveforms caused by impedance mismatch of the mode converter and the time-domain waveforms generated by the reflection of the absorbed load need to be filtered out to avoid affecting the calculation of the reflectivity of the absorbed load.

[0044] Based on the physical dimensions of the test link, the time-domain location of the reflection peak caused by the absorbing load is determined, i.e., the time t it takes for the high-power millimeter wave reflected from the absorbing load to reach the vector network analyzer is determined, where t = 2L / c, where c is the speed of light and L is the distance from the reference port of the vector network analyzer to the absorbing load. The reflection peak caused by the absorbing load is then gated to filter out the reflection waveform caused by impedance mismatch in the mode converter, resulting in the gated time-domain curve S. 11 * (t);

[0045] The reflection peak caused by the absorption load is gated using the window function win, and the formula is as follows:

[0046] S 11 * (t)=S 11 (t)*win.

[0047] Using Discrete Fourier Transform, the gated time-domain curve S 11 * (t) is transformed to the frequency domain to obtain the frequency domain curve S of the absorbed load. 11 * ,

[0048] Further calculations yielded the reflectivity Γ of the absorption load, using the following formula:

[0049]

[0050] Example 2

[0051] like Figure 3 As shown, a test system for the reflectivity of a high-power millimeter-wave absorbing load includes a vector network analyzer, a spread spectrum module, a mode converter, and an absorbing load connected in sequence.

[0052] Vector network analyzer for testing the frequency domain curves S of mode converters and absorbed loads.11 ;

[0053] The spread spectrum module is connected with the vector network analyzer, and extends the frequency range that can be tested by the vector network analyzer;

[0054] The mode converter is connected with the spread spectrum module and the absorbing load, and realizes conversion of the TE10 mode of the port rectangular waveguide of the spread spectrum module into the HE11 mode or the Gaussian beam, and the mode converter is a corrugated waveguide or a corrugated horn;

[0055] The absorbing load absorbs high-power millimeter wave power and is partially reflective.

[0056] In the application, the time domain reflectometer (TDR) with the same function as the vector network analyzer can be realized, and the application can also be used for high-power millimeter wave testing.

[0057] In summary, impedance mismatch of the mode converter can cover the reflectivity test result of the absorbing load, the application proposes discrete Fourier transform (DFT and DIFT) based on the time-frequency domain conversion, and the impedance mismatch of the mode converter is filtered out in the time domain, the reflectivity of the absorbing load is tested by using the vector network analyzer and the mode converter, the reflectivity of the absorbing load in the HE11 mode or the Gaussian beam is tested, compared with the existing absorbing load reflectivity test method, the absorbing load reflectivity test method proposed in the application is simple in operation, simple in system link, high in test precision and good in repeatability.

[0058] The above is only the preferred embodiment of the application, but the protection scope of the application is not limited to this, any person skilled in the art can think of changes or replacements in the technical range disclosed by the application without creative labor, which should be covered in the protection scope of the application. Therefore, the protection scope of the application should be limited by the protection scope defined in the claims.

Claims

1. A method of testing high power millimeter wave absorption load reflectivity, characterized by, The method comprises the following steps: After connecting the absorbing load to the mode converter back end, the frequency domain curve S of the reflection of the absorbing load is measured by a vector network analyzer 11 ; The frequency domain curve S 11 is transformed into time domain by using inverse discrete Fourier transform to obtain the time domain curve S 11 (t), and the specific formula is: The pulse condition of the time domain curve S 11 (t) is observed. According to the physical size of the test link, the time domain position of the reflection peak caused by the absorbing load is determined, that is, the time t at which the absorbing load reflects the high-power millimeter wave to the vector network analyzer is determined, t = 2L / c, wherein c is the speed of light, and L is the distance from the reference port of the vector network analyzer to the absorbing load. The reflection peak caused by the absorbing load is gated by a window function win, and the formula is: S 11 * (t) = S 11 (t) * win; The reflection peak caused by the absorption load is gated, and the reflection waveform caused by the impedance mismatch of the mode converter is filtered out to obtain a gated time domain curve S 11 * (t), and the specific process is implemented through the following formula: The gated time-domain curve S is transformed into frequency domain by using discrete Fourier transform 11 * (t) is transformed into frequency domain to obtain the curve S of absorption load 11 * The reflectivity Γ of the absorption load is further calculated, and the formula is:

2. A test system for high power millimeter wave absorption load reflectivity, characterized in that, The test system performs the test method of claim 1, comprising a vector network analyzer, a spread spectrum module, a mode converter and an absorbing load connected in sequence, The vector network analyzer is used for testing the frequency domain curve S11 of the mode converter and the absorbing load; The spread spectrum module is connected with the vector network analyzer and expands the frequency range testable by the vector network analyzer; A mode converter is connected with the spread spectrum module and the absorbing load, and realizes the rectangular waveguide TE 10 mode to HE 11 The conversion of the mode or the Gaussian beam, and the mode converter is a corrugated waveguide or a corrugated horn; The absorbing load absorbs high-power millimeter wave power and is partially reflected.

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