Method and system for testing dielectric stability of a sheet material

Abstract

The application relates to a plate material dielectric stability test method and a test system, and relates to the technical field of electromagnetic measurement.The plate material dielectric stability test method comprises the following steps: step 1: a planar capacitive resonance module is attached to the upper surface of a material to be measured, the planar capacitive resonance module comprises a resonance coil and two capacitive plates arranged on the same plane, and the two terminals of the resonance coil are connected to the two capacitive plates in a one-to-one correspondence; step 2: a frequency analyzer reads resonance frequency information through a coupler matched with the planar capacitive resonance module; step 3: the temperature of the material to be measured is measured, the temperature and the characteristic points of the resonance frequency information are compared with a pre-stored parameter comparison table, and the corresponding dielectric constant is obtained as a measured dielectric constant, the parameter comparison table records the corresponding relationship among the temperature, the characteristic points of the resonance frequency information and the dielectric constant; and step 4: the measured dielectric constant is compared with a theoretical dielectric constant.The application can realize nondestructive testing.

Description

Technical Field

[0001] This invention relates to the field of electromagnetic measurement technology, and in particular to the testing of the dielectric constant stability of materials. Background Technology

[0002] With the rapid development of electronic technology, testing systems and equipment are constantly evolving towards miniaturization, portability, and efficiency. Meanwhile, the application of sheet materials in modern high-tech fields such as communications and aerospace is becoming increasingly widespread, leading to a continuous increase in the demand for precise characterization of their key performance parameters. However, current mainstream methods for testing the dielectric constant stability of sheet materials generally rely on vector network analyzers or impedance analyzers to test material samples of fixed sizes. These devices are not only bulky and expensive, but also have high requirements for the operating environment and are difficult to adapt to on-site testing and rapid testing application scenarios.

[0003] Currently, sheet-like electromagnetic functional materials are mainly used in key projects such as radomes and electromagnetic functional skins. With the increasing demands for the dielectric stability of these materials, developing rapid, high-resolution testing methods has become a critical issue that urgently needs to be addressed in this testing field. Resonance refers to the phenomenon where, through the series or parallel connection of an inductor and capacitor, the inductive reactance of the inductor and the capacitive reactance of the capacitor cancel each other out at a specific frequency, thus causing the circuit to exhibit purely resistive characteristics. Based on this fundamental characteristic of resonance, the resonant frequency can be accurately obtained under specific circuit structures, providing an effective way for high-precision characterization of the dielectric properties of materials.

[0004] Chinese patent application 202011383414.9 discloses a relative permittivity testing technique that employs a resonance method. A ground plane (i.e., a second ground layer) of a microstrip line is bonded to the lower surface of a substrate containing the medium under test. A resonant conductive strip is placed on the upper surface of the substrate. A measuring device is connected to a probe via an electrical connection. By bringing the probe close to the resonant conductive strip on the upper surface of the substrate, the resonant frequency of that transmission line segment is measured. Based on a pre-defined relationship between the relative permittivity of the medium under test and the resonant frequency and substrate thickness, the relative permittivity of the medium under test is obtained. By separately placing a second ground layer and a resonant conductive strip on the medium under test, and connecting the second ground layer to the medium under test through bonding, the relative permittivity of the medium under test can be tested using the resonance method without damaging the medium. However, the technique in Chinese patent application 202011383414.9 requires microstrip lines to be placed on both the upper and lower surfaces of the medium under test, making non-destructive testing impossible for already installed equipment.

[0005] Chinese patent application 202211046593.6 discloses a millimeter-wave dielectric property testing device and method for electrically aligned liquid crystal materials. It designs a liquid crystal cell composed of multiple dielectric layers, using a symmetrical TM structure formed by multiple dielectric layers. 0n0The double-sided circular patch resonator has an internal electric field distribution that passes through the multilayer dielectric under test and is perpendicular to the metal disc. Therefore, by utilizing its internal field distribution characteristics, this structure can use modes with higher resonant frequencies.

[0006] Chinese patent application 202110984878.3 provides a dual-band lossless dielectric constant measurement sensor technology based on a spiral resonator. According to paragraph 0031 of its specification, from bottom to top, it includes a ground layer (3), a dielectric layer (2), and a metal patch layer (1).

[0007] Chinese patent applications 202211046593.6 and 202110984878.3 both pertain to resonant cavity Q-value testing. These require a coupled excitation source and a detection source, necessitate dual-port testing, and both require destroying the sample and placing it in a fixed position, making on-site testing during construction and maintenance impossible. Furthermore, resonant cavity Q-value testing places significant demands on material loss; excessive loss will cause the cavity Q-value to exceed its transformation range. Summary of the Invention

[0008] The technical problem to be solved by the present invention is to provide a method and system for testing the dielectric stability of plate-shaped materials, which can conveniently realize high-precision non-destructive field testing.

[0009] The technical solution adopted by the present invention to solve the aforementioned technical problem is a method for testing the dielectric stability of plate-shaped materials, comprising the following steps:

[0010] Step 1: Attach a planar capacitor resonant module to the upper surface of the material to be tested. The planar capacitor resonant module includes a resonant coil and two capacitor plates disposed on the same plane. The two terminals of the resonant coil are respectively connected to the two capacitor plates one by one.

[0011] Step 2: The frequency analyzer reads the resonant frequency information through a coupler adapted to the planar capacitor resonant module;

[0012] Step 3: Measure the temperature of the material to be tested, compare the characteristic points of temperature and resonant frequency information with the pre-stored parameter lookup table, and obtain the corresponding dielectric constant as the measured dielectric constant. The parameter lookup table records the correspondence between the characteristic points of temperature and resonant frequency information and the dielectric constant.

[0013] Step 4: Compare the measured dielectric constant with the theoretical dielectric constant.

[0014] Furthermore, the planar capacitor resonant module includes an electrode spacing adjustment structure, which has at least two selectable positions, each position corresponding to a preset electrode spacing;

[0015] Furthermore, the frequency analyzer is a vector network analyzer, impedance analyzer, or inductance-capacitance meter (LCR meter).

[0016] The characteristic point of the resonant frequency information is the frequency point where the resonant peak is located.

[0017] The present invention also provides a dielectric stability testing system for plate-shaped materials, which adopts the aforementioned dielectric stability testing method for plate-shaped materials. The dielectric stability testing system for plate-shaped materials includes the following parts:

[0018] A planar capacitor resonant module includes two capacitor plates disposed on the lower surface of a substrate and a resonant coil disposed on the upper surface of the substrate;

[0019] The frequency analyzer has its signal input terminal connected to the two connection terminals of the coupler, and its output terminal connected to the detection and query module.

[0020] The detection and query module stores the correspondence between feature points with temperature and resonant frequency information and dielectric constants;

[0021] The temperature sensor has its temperature detection point set on the lower surface of the substrate. The output of the temperature sensor is connected to the detection query module to detect the temperature of the material to be tested.

[0022] Furthermore, the planar capacitor resonant module includes a capacitor plate spacing adjustment structure with at least two selectable positions, each position corresponding to a preset plate spacing; the detection and query module stores the correspondence between feature points of temperature and resonant frequency information, plate spacing and dielectric constant.

[0023] The advantages of this invention are that it enables convenient and accurate measurement of the dielectric constant of the material under test without affecting the material's installation condition. It allows for "contact-based testing" of non-destructive testing and is fully applicable to construction sites and post-installation maintenance and testing conditions. This invention is characterized by low cost and high precision.

[0024] This invention proposes a testing system and method for the dielectric constant stability of plate-shaped materials. It innovatively employs a surface-mount testing approach, combined with the principle of parallel capacitor resonance, effectively broadening the dynamic adjustment range of the capacitance and significantly improving the measurement resolution and sensitivity of the dielectric stability of plate-shaped materials. During the test, the parallel resonant circuit enters a resonant state at a specific frequency, where the circuit current is at its minimum, the voltage is at its maximum, and the equivalent impedance reaches its peak. By directly attaching the plate-shaped material to the surface of the parallel resonant circuit, the dielectric loss alters the electric field distribution in the resonant region, effectively adjusting the capacitance in the circuit and causing a significant shift in the resonant frequency. The changes in the resonant frequency are collected using high-precision testing instruments, and combined with data processing algorithms, the stability of the dielectric constant of the plate-shaped material is accurately evaluated. Attached Figure Description

[0025] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced 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 on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a schematic diagram illustrating the principle of the present invention;

[0027] Figure 2 This is a schematic diagram of the characteristic points of the resonant frequency information;

[0028] Figure 3 This is a schematic diagram of the upper surface structure of the substrate of the planar capacitor resonant module structure of the present invention;

[0029] Figure 4 This is a schematic diagram of the lower surface structure of the substrate of the planar capacitor resonant module structure of the present invention;

[0030] Figure 5 This is a schematic diagram of the lower surface structure of the substrate in Example 2. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0032] This invention provides a method for testing the dielectric constant of plate-shaped materials based on a patch-type parallel resonant structure. The system uses a portable testing instrument as the signal source and detection unit, directly attaching the material under test to the resonant circuit to form an adjustable resonant system. Different materials, due to differences in their dielectric constant and loss characteristics, will alter the equivalent capacitance of the resonant region, thus causing a significant shift in the parallel resonant frequency. By accurately capturing the positional changes of the resonant frequency and the transformation of impedance information, combined with a calibration database, the differences in the dielectric constant of materials and their stability can be quickly identified and evaluated. This method is simple to operate, has a rapid response, and is suitable for efficient on-site testing and screening of multiple batches of materials.

[0033] Unlike existing technologies that require test components to be placed on the top and bottom sides of the medium, this invention only requires test components to be placed on one side of the surface of the material to be tested to complete accurate testing. It does not require damaging the installation of the material to be tested, thus truly realizing non-destructive testing on site.

[0034] Example 1

[0035] See Figure 1 and Figure 2 .

[0036] Figure 2 The resonant frequency curves of two materials (material A and material B) with different dielectric constants are shown, with the vertical axis S. 11 This refers to reflectivity. It's evident that materials with different dielectric constants will have different frequencies corresponding to their resonance peaks. If a sample designed with a dielectric constant of 15 is tested, and the frequency of the resonance peak is found to be 0.28 GHz, and a database query returns a frequency of 0.28 GHz, which matches the frequency (X-axis corresponding to the peak value) of the resonance peak of a material with a dielectric constant of 15, then the dielectric constant of that material is considered to be 15. This proves that the dielectric constant of the material matches the design value, thus confirming its stability.

[0037] The dielectric stability testing method for plate-shaped materials provided in this embodiment includes the following steps:

[0038] Step 1: Attach a planar capacitor resonant module to the upper surface of the material to be tested. The planar capacitor resonant module includes two capacitor plates and a resonant coil disposed on the same plane. The two terminals of the resonant coil are respectively connected to the two capacitor plates one by one.

[0039] Step 2: The frequency analyzer reads the resonant frequency information through a coupler adapted to the planar capacitor resonant module;

[0040] Step 3: Compare the characteristic points of the resonant frequency information with the pre-stored parameter lookup table to obtain the corresponding dielectric constant as the measured dielectric constant;

[0041] Step 4: Compare the measured dielectric constant with the theoretical dielectric constant.

[0042] The testing system of this invention includes:

[0043] A planar capacitor resonant module includes two capacitor plates disposed on the lower surface of a substrate and a resonant coil disposed on the upper surface of the substrate; Figure 3 The resonant coil on the upper surface of the substrate is shown. Figure 4 A schematic diagram of the capacitor plate distribution on the lower surface of the substrate is shown. The shaded area represents the capacitor plate. The resonant coil and the capacitor plate are connected by a circuit formed through a through-hole penetrating the substrate.

[0044] A frequency analyzer has its signal input terminal connected to the two connection terminals of a coupler, and its output terminal connected to a detection and query module. A frequency analyzer refers to a device that can analyze resonant frequencies, such as a single-port vector network analyzer like the Copper Mountain-R60, or an impedance analyzer, LCR meter, etc., all of which are mature devices.

[0045] The temperature sensor has its temperature detection point located on the lower surface of the substrate, on the same plane as the capacitor plate. The output of the temperature sensor is connected to the detection and query module to detect the temperature of the material to be tested.

[0046] The detection and query module stores the correspondence between characteristic points of resonant frequency information and dielectric constants. The characteristic points of resonant frequency information are the frequency points where the resonant peak is located, which are referred to as resonant frequency points in this invention.

[0047] The detection and query module receives frequency information from the frequency analyzer and temperature information from the temperature sensor. It calculates the characteristic points of the resonant frequency information from the frequency information, and then queries and compares them in a parameter lookup table that records the characteristic points of temperature and resonant frequency information and the corresponding dielectric constant information, and outputs the stability judgment result.

[0048] Work process:

[0049] First, the parameter lookup table is saved in the database format in the detection and query module (PC or other type of computer, such as tablet), as shown in Table 1:

[0050] Table 1

[0051] Dielectric constant temperature Resonance frequency 14 -40℃ 267.4MHz 14 -20℃ 268.7MHz 14 0℃ 270.6MHz 14 20℃ 271.3MHz 14 40℃ 272.0MHz 22 -40℃ 226.7MHz 22 -20℃ 228.2MHz 22 0℃ 230.0MHz 22 20℃ 231.1MHz 22 40℃ 231.8MHz

[0052] The table above only shows the correspondence in tabular form; the actual data is not limited to a tabular format.

[0053] The characteristic point of the resonant frequency information is the frequency point where the resonant peak is located (the same applies to wave peaks and valleys), and the dielectric constant is the dielectric constant.

[0054] During testing, a planar capacitor resonant module is attached to the surface of the material under test. A portable frequency analyzer collects the resonance parameters of the planar capacitor resonant module through a coupler, which are represented on the frequency analyzer as the frequency point where the resonance peak is located. Combined with the material temperature data collected by the temperature sensor, the dielectric constant corresponding to the temperature and frequency point data is retrieved in the detection query module, that is, the measured dielectric constant is obtained. By comparing it with the design parameters (i.e., theoretical parameters) of the material under test, the stability of the dielectric constant of the tested material can be determined.

[0055] Detailed explanation:

[0056] Frequency analyzers can be commercially available portable vector network analyzers, impedance analyzers, or LCR meters, etc., which can record the characteristics of transmission line ports. They have single-port testing capabilities and can dynamically analyze the S-parameters or impedance parameters of ports.

[0057] The instrument's terminal test ports are calibrated using general standard mechanical calibration components, namely open circuit calibration components, short circuit calibration components, and 50-ohm load calibration components.

[0058] The coupler uses an RF transmission line to connect to the frequency analyzer, and can radiate and receive electromagnetic wave signals to and from the resonant circuit. The coupler structure is a small loop antenna, and it has no obvious resonant characteristics in the test frequency band.

[0059] Resonators and planar capacitors are used to form parallel resonant circuits, which can be used for surface-mount testing of the material under test. The resonator mainly consists of a high-frequency Q-inductor and a structural capacitor.

[0060] A planar capacitor consists of two coplanar parallel metal electrodes. During testing, the coplanar parallel metal electrodes are attached to the surface of the plate-shaped material being tested.

[0061] The plate-shaped material is a composite material composed of various resins and functional materials. The dielectric constant of the plate-shaped material applicable to this invention can reach 1~200, which is superior to the prior art.

[0062] The testing process consists of three parts: system calibration, application of test samples, and parameter comparison.

[0063] Calibration: Adjust the test instrument to the frequency band to be tested, connect one end of the cable to the port of the test instrument, and connect the other end to the calibration component to perform port calibration.

[0064] Test: The planar capacitor is attached to the surface of the standard control sample material, and a coupler connected to the test instrument is placed on top of it to test the sample and record the sample's resonant frequency position, resonant impedance, and reflectivity information.

[0065] The standard reference material is a material sample with known material parameters, including material dimensions, material thickness, material stacking structure, material dielectric constant, and material magnetic permeability.

[0066] A planar capacitance and temperature sensor are attached to the surface of the plate-shaped material to be tested, and a coupler for connecting the test instrument is placed on top of it to test the sample and record the sample temperature, resonant frequency position, resonant impedance, and reflectivity information.

[0067] By combining the test data of the sample under test and the data of the standard control sample, the temperature, resonant frequency position, resonant impedance and reflectivity information obtained from the test are compared with the calibration data, and the deviation of each data is recorded. The stability of the dielectric constant of the plate material is evaluated by the agreed maximum permissible deviation of each data.

[0068] This invention can accurately detect the dielectric constant stability of materials under different temperature environments, and has extremely high practical value in the field of new material testing.

[0069] Example 2: See Figure 5 .

[0070] Based on Example 1, the present invention adds the function of adjustable capacitance to further eliminate the limitations that may arise from a single test parameter.

[0071] The planar capacitor resonant module of this embodiment includes a capacitor plate spacing adjustment structure 40, which has at least two selectable positions (which can be set via a scale), each position corresponding to a preset plate spacing; ordinary technicians can implement it according to the contents of the instruction manual, and its specific structure will not be described in detail here.

[0072] The detection and query module stores the correspondence between feature points recording temperature and resonant frequency information, electrode spacing, and dielectric constant.

[0073] By using this embodiment, the test results under different electrode spacings can be compared and cross-validated to improve measurement accuracy.

[0074] Example 3

[0075] As an alternative to Embodiment 2, the test system in this embodiment is configured with multiple planar capacitor resonant modules, each with different capacitance or inductance parameters. This embodiment achieves testing under different resonant parameters by replacing the planar capacitor resonant modules.

Claims

1. A method for testing the dielectric stability of plate-shaped materials, characterized in that, Includes the following steps: Step 1: Attach a planar capacitor resonant module to the surface of the material to be tested. The planar capacitor resonant module includes a resonant coil and two capacitor plates disposed on the same plane. The two terminals of the resonant coil are respectively connected to the two capacitor plates. Attach the two capacitor plates of the planar capacitor to the surface of the plate-shaped material to be tested. Step 2: The frequency analyzer reads the resonant frequency information through a coupler adapted to the planar capacitor resonant module; Step 3: Measure the temperature of the material to be tested, compare the characteristic points of temperature and resonant frequency information with the pre-stored parameter lookup table, and obtain the corresponding dielectric constant as the measured dielectric constant. The parameter lookup table records the correspondence between the characteristic points of temperature and resonant frequency information and the dielectric constant. Step 4: Compare the measured dielectric constant with the theoretical dielectric constant to determine stability.

2. The method for testing the dielectric stability of plate-shaped materials as described in claim 1, characterized in that, The planar capacitor resonant module includes an electrode spacing adjustment structure with at least two selectable positions, each corresponding to a preset electrode spacing.

3. The method for testing the dielectric stability of plate-shaped materials as described in claim 1, characterized in that, The frequency analyzer is a vector network analyzer, impedance analyzer, or inductance-capacitance tester.

4. The method for testing the dielectric stability of plate-shaped materials as described in claim 1, characterized in that, The characteristic point of the resonant frequency information is the frequency point where the resonant peak is located.

5. A dielectric stability testing system for plate-shaped materials, characterized in that, It employs the dielectric stability testing method for plate-shaped materials as described in claim 1, wherein the dielectric stability testing system for plate-shaped materials comprises the following components: A planar capacitor resonant module includes two capacitor plates disposed on the lower surface of a substrate and a resonant coil disposed on the upper surface of the substrate; The frequency analyzer has its signal input terminal connected to the two connection terminals of the coupler, and its output terminal connected to the detection and query module. The detection and query module stores the correspondence between feature points with temperature and resonant frequency information and dielectric constants; The temperature sensor has its temperature detection point set on the lower surface of the substrate. The output of the temperature sensor is connected to the detection query module to detect the temperature of the material to be tested.

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