Calibration system and method for high-temperature waveguide electromagnetic parameter test

Abstract

The invention discloses a calibration system and method for high-temperature waveguide electromagnetic parameter testing, and belongs to the technical field of testing. According to the invention, the movable device is arranged, the S parameters of the test straight-through piece, the reflector plate and the no-load offset piece are switched by using the movable device in a high-temperature environment to complete high-temperature calibration, and then the offset piece for loading the sample is switched to carry out material test, so that the synchronization of the high-temperature calibration and the sample test state is ensured; and conical pins and corresponding positioning holes are arranged for connection and fixation, so that unified alignment of waveguide ports after switching is ensured. Influences caused by clamp expansion deformation and electrical property change at high temperature can be eliminated, and the high-temperature test precision is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of testing, and particularly relates to a calibration system and method for testing electromagnetic parameters of high-temperature waveguides. Background Art

[0002] Microwave dielectric materials, as media for electromagnetic wave transmission, have been widely used in systems such as satellite communication, electronic countermeasure, radar navigation, remote sensing, and telemetry. Transparent wave materials are a typical type of microwave dielectric material, and their performance is mainly characterized by electromagnetic parameters. Therefore, it is very important to accurately measure the microwave parameters of dielectric materials.

[0003] The methods for measuring electromagnetic parameters of materials in the millimeter-wave band can be classified into resonance methods and network parameter methods according to the principle. The resonance method can only perform point-frequency measurement. By placing the sample in a resonant cavity and using the changes in the electromagnetic field characteristics (quality factor and resonant frequency) in the cavity with and without the sample, the electromagnetic parameters of the dielectric material are calculated. The network parameter method can perform sweep-frequency measurement in a wide frequency band. The sample and its sensor are regarded as a one-port or two-port network, and the electromagnetic parameters of the dielectric material are calculated by measuring the network parameters. As a test method of the network parameter method, the waveguide method has the advantages of a wide test frequency band and high test accuracy.

[0004] In the existing high-temperature test methods using the waveguide method, in the high-temperature waveguide method test system developed by Jiang Yu of North University of China, the system is as Figure 1 shown. The system calibration method is to open the cavity at room temperature to perform TRL calibration on the test fixture, and keep the temperature insulated by closing the cavity in the high-temperature test state. After the temperature rises to the target temperature and stabilizes, the test is carried out. It can only perform calibration operations at room temperature and cannot eliminate the influence brought by the expansion and deformation of the fixture and the change of electrical performance at high temperature.

[0005] Wang Yi of the University of Electronic Science and Technology built a 1300 °C high-temperature waveguide method test system. The test system is as shown in Figure 2, where 1 - coaxial waveguide converter; 2 - directional coupler; 3 - water-cooled part; 4 - variable-temperature waveguide; 5 - sealing window. By using the transformation of the T-parameter matrix and the S-parameter matrix, the reflection coefficient of the waveguide section during high-temperature testing is obtained, and an empty waveguide comparison calibration is added to eliminate the influence of thermal expansion on the waveguide model. However, it is necessary to measure the reflection coefficient of the empty carrier waveguide first and then optimize the parameters of the test results, which is different from the real-time calibration at high temperature proposed by the present invention. Compared with this system, the calibration method at high temperature proposed by the present invention has simpler test steps and higher test accuracy.

[0006] The Beijing Institute of Radio Metrology and Measurement constructed a coaxial transmission and reflection method system from room temperature to 600 °C. The design adopts a calibration method of calibrating at room temperature and correcting at high temperature. The design model of this system is as Figure 3 shown. By introducing a high-temperature error matrix, the scattering parameters of the material under test under target temperature conditions are obtained, which is different from the high-temperature calibration method based on the high-temperature waveguide method of this system.

[0007] The above high-temperature test scheme adopts the method of sealing the test environment. This method can ensure the accuracy of the test temperature. However, in the high-temperature environment, the calibration process and the loading of sample tests cannot be carried out simultaneously. Calibration needs to be carried out at room temperature. After calibration is completed, the sample is placed and then the temperature is raised for testing. It is impossible to eliminate the influence of waveguide deformation and the like on the test results at high temperature. There will be ineliminable errors when calibrating high-temperature tests only at room temperature. Summary of the Invention

[0008] In view of the above technical problems existing in the prior art, the present invention proposes a calibration system and method for high-temperature waveguide electromagnetic parameter testing, which is reasonably designed, overcomes the deficiencies of the prior art, and has good effects.

[0009] In order to achieve the above object, the present invention adopts the following technical solutions:

[0010] A calibration system for high-temperature waveguide electromagnetic parameter testing includes a sealed heating cavity, which is internally provided with a movable switching device, a network analyzer, a calibration component, a pin and a positioning hole structure, and an observation window;

[0011] The calibration component includes a reflection sheet and an unloaded offset sheet;

[0012] The movable switching device is configured to be able to switch different calibration components and samples in a high-temperature environment for high-temperature calibration;

[0013] The network analyzer is configured to measure the S parameters of the calibration component;

[0014] The pin and the positioning hole structure are configured to achieve precise alignment of the waveguide ports;

[0015] The observation window is configured to facilitate the operator to observe and adjust the switching process to ensure the accurate alignment of the pin and the positioning hole.

[0016] Preferably, the pin adopts a tapered pin.

[0017] Preferably, the observation window adopts a high-temperature resistant transparent observation window.

[0018] In addition, the present invention also mentions a calibration method for high-temperature waveguide electromagnetic parameter testing. This method adopts the above-mentioned calibration system for high-temperature waveguide electromagnetic parameter testing, and specifically includes the following steps:

[0019] Step 1: Sample preparation;

[0020] Step 2: System setup;

[0021] Step 3: High-temperature calibration; specifically includes the following steps:

[0022] Step 3.1: Use a movable switching device to directly connect the two waveguide ports, and fasten the pins and positioning holes.

[0023] Step 3.2: Confirm through the observation window that the pins and positioning holes are completely aligned.

[0024] Step 3.3: Use a network analyzer to measure the S-parameters in the through state.

[0025] Step 3.4: Repeat Steps 3.1 - 3.3 to measure the S-parameters of the reflector and the unloaded offset piece calibration piece in sequence.

[0026] Step 3.5: Perform calibration at the target temperature using the measured S-parameters.

[0027] Preferably, in Step 1, it specifically includes the following steps:

[0028] Step 1.1: Process the material to be tested according to the waveguide size to make it into a rectangular / circular thin sheet that matches the waveguide cross-section.

[0029] Step 1.2: Measure and record the thickness of the sample.

[0030] Step 1.3: Ensure that the surface of the sample is flat and clean.

[0031] Preferably, in Step 2, it specifically includes the following steps:

[0032] Step 2.1: Connect a network analyzer with a suitable frequency range and interface type to the waveguide.

[0033] Step 2.2: Place the waveguide in a sealed heating cavity with an observation window.

[0034] The beneficial technical effects brought by the present invention:

[0035] The present invention provides a calibration system and method for testing the electromagnetic parameters of a high-temperature waveguide; a movable device is set up, and the S-parameters of the through, reflector, and unloaded offset piece are switched and measured in a high-temperature environment using the movable device to complete high-temperature calibration, and then the offset piece loaded with the sample is switched for material testing to ensure that the high-temperature calibration is synchronized with the sample testing state; a tapered pin and corresponding positioning holes are set for connection and fixation to ensure the unified alignment of the waveguide ports after switching. The present invention can eliminate the influence brought by the expansion and deformation of the fixture and the change of electrical performance at high temperature, and improve the high-temperature test accuracy. Description of the Drawings

[0036] Figure 1 It is a system block diagram of the prior art;

[0037] Figure 2 It is a test system block diagram of the prior art;

[0038] Figure 3 It is the design model diagram of the system;

[0039] Figure 4 It is the schematic diagram of the internal connection of the heating cavity. Specific implementation manners

[0040] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific implementation manners:

[0041] The method of the present invention mainly aims at the problem of high-temperature test accuracy of the high-temperature waveguide test system. By adding a switching device to switch the reflector, the open-circuit offset sheet, and the waveguide offset sheet containing the sample to be measured, the TRL calibration operation at high temperature is realized, and the high-temperature calibration and material test are carried out simultaneously, so as to improve the accuracy of the high-temperature waveguide test.

[0042] Design a tapered pin and a high-temperature observation window. When moving and switching, it is possible to confirm through the observation window that the pin is completely matched with the positioning hole of the waveguide offset sheet, ensuring the unified alignment of the waveguide ports after switching.

[0043] Embodiment 1:

[0044] A calibration system for measuring the electromagnetic parameters of a high-temperature waveguide includes a sealed heating cavity, in which a movable switching device, a network analyzer, a calibration component, a tapered pin and a positioning hole structure, and a high-temperature resistant transparent observation window are arranged;

[0045] The calibration component includes a reflector and an open-circuit offset sheet;

[0046] The movable switching device is configured to be able to switch different calibration components and samples in a high-temperature environment for high-temperature calibration;

[0047] The network analyzer is configured to measure the S parameters of the calibration component;

[0048] The pin and the positioning hole structure are configured to achieve the precise alignment of the waveguide ports;

[0049] The observation window is configured to facilitate the operator to observe and adjust the switching process to ensure the accurate alignment of the pin and the positioning hole.

[0050] Embodiment 2:

[0051] On the basis of the above Embodiment 1, the present invention also mentions a calibration method for measuring the electromagnetic parameters of a high-temperature waveguide, which specifically includes the following steps:

[0052] Step 1: Sample preparation; specifically includes the following steps:

[0053] Step 1.1: Process the material to be measured according to the waveguide size to make it into a rectangular / circular thin sheet that matches the waveguide cross-section;

[0054] Step 1.2: Measure and record the thickness of the sample;

[0055] Step 1.3: Ensure that the surface of the sample is flat and clean.

[0056] Step 2: System setup; specifically including the following steps:

[0057] Step 2.1: Connect a network analyzer with a suitable frequency range and interface type to the waveguide;

[0058] Step 2.2: Place the waveguide in a sealed heating cavity with an observation window.

[0059] Step 3: High-temperature calibration; specifically including the following steps:

[0060] Step 3.1: Use a movable switching device to place the through calibration component at the test position, and fasten the pin and the positioning hole;

[0061] Step 3.2: Confirm through the observation window that the pin and the positioning hole are completely aligned;

[0062] Step 3.3: Use the network analyzer to measure the S-parameters of the through calibration component;

[0063] Step 3.4: Repeat steps 3.1 - 3.3 to measure the S-parameters of the reflector and the open offset calibration components in sequence;

[0064] Step 3.5: Use the measured S-parameters to perform calibration at the target temperature.

[0065] Figure 4 It is a schematic diagram of the internal connection of the heating cavity. The S-parameters of the through, reflector, and open offset can be switched under high-temperature environment through a movable switching device to complete high-temperature calibration, and then switch to the offset loaded with the sample for material testing. Taper pins and corresponding positioning holes are provided at both ends of the connections of different components for connection and fixation. When moving, align the pins of the switching component with the positioning holes through the observation window, and slowly tighten until the pins and the positioning holes are completely matched to ensure the unified alignment of the waveguide ports after switching.

[0066] Of course, the above description is not a limitation of the present invention, and the present invention is not limited to the above examples. Changes, modifications, additions, or substitutions made by those skilled in the art within the essence of the present invention should also fall within the protection scope of the present invention.

Claims

1. A calibration system for testing electromagnetic parameters of a high-temperature waveguide, characterized in that: It includes a sealed heating cavity, inside which there are a movable switching device, a network analyzer, a calibration component, a pin and a positioning hole structure, and an observation window; The calibration component includes a reflection sheet calibration component and an air - loaded offset sheet calibration component; The movable switching device is configured to be able to switch different calibration components and samples in a high - temperature environment for high - temperature calibration; The network analyzer is configured to measure the S - parameters of the calibration component; The pin and the positioning hole structure are configured to achieve precise alignment of the waveguide ports; The observation window is configured to facilitate the operator to observe and adjust the switching process to ensure the accurate alignment of the pin and the positioning hole.

2. The calibration system for testing electromagnetic parameters of a high-temperature waveguide according to claim 1, characterized in that: The pin uses a tapered pin.

3. The calibration system for testing electromagnetic parameters of a high-temperature waveguide according to claim 1, characterized in that: The observation window uses a high - temperature - resistant transparent observation window.

4. A calibration method for measuring electromagnetic parameters of a high-temperature waveguide, characterized in that: A calibration system for testing the electromagnetic parameters of a high - temperature waveguide as described in claim 1 is adopted, which specifically includes the following steps: Step 1: Sample preparation; Step 2: System setup; Step 3: High - temperature calibration; specifically includes the following steps: Step 3.1: Use the movable switching device to directly connect the two waveguide ports, and fasten the pin and the positioning hole; Step 3.2: Confirm through the observation window that the pin and the positioning hole are completely aligned; Step 3.3: Use the network analyzer to measure the S - parameters in the through - connection state; Step 3.4: Repeat steps 3.1 - 3.3 to measure the S - parameters of the reflection sheet and the air - loaded offset sheet calibration components in sequence; Step 3.5: Use the measured S - parameters to perform calibration at the target temperature.

5. The calibration method for testing electromagnetic parameters of a high-temperature waveguide according to claim 4, characterized in that: In step 1, it specifically includes the following steps: Step 1.1: Process the material to be measured according to the waveguide size to make it into a rectangular / circular thin sheet that matches the waveguide cross - section; Step 1.2: Measure and record the thickness of the sample; Step 1.3: Ensure that the surface of the sample is flat and clean.

6. The calibration method for testing electromagnetic parameters of a high-temperature waveguide according to claim 4, characterized in that: In step 2, it specifically includes the following steps: Step 2.1: Connect a network analyzer with a suitable frequency range and interface type to the waveguide; Step 2.2: Place the waveguide in a sealed heating cavity with an observation window.

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