Capacitor equivalent series resistance value calculation method and resonant cavity testing device

Abstract

The embodiment of the invention provides a capacitor equivalent series resistance value calculation method and a resonant cavity test device. The method comprises the following steps: acquiring a first loss angle tangent value, a first resonant frequency of a preset wavelength, a second loss angle tangent value and a second resonant frequency of the preset wavelength; determining an equivalent series resistance value of the capacitor to be measured according to the first loss angle tangent value, the second loss angle tangent value, the first resonant frequency and the second resonant frequency; according to the embodiment of the invention, the resonant cavity parameters are obtained under the condition that whether the to-be-tested capacitor is installed in the test device of the resonant cavity or not, and the equivalent series resistance value of the to-be-tested capacitor under the preset wavelength is calculated according to the resonant cavity parameters under different conditions, so that the ESR test of different application frequency bands can be adapted.

Description

Technical Field

[0001] The present application relates to the technical field of testing, and in particular, to a method for calculating the equivalent series resistance value of a capacitor and a test device for a resonant cavity. Background Art

[0002] Application of Nuclear Magnetic Resonance Nuclear magnetic resonance imaging (MRI) examination has become a common imaging examination method. As a new imaging examination technology, nuclear magnetic resonance imaging has no impact on human health. Currently, the commonly used MRI equipment in clinics uses hydrogen atom resonance, and its resonance frequency is 42.58 MHz / T. At a magnetic field strength of 1.5 T, the working frequency of MRI is 64 MHz (42.58 MHz / T * 1.5 T).

[0003] Currently, an impedance analyzer can be used to detect the capacitors in the equipment. This impedance analyzer is used to test the ESR (Equivalent Series Resistance) of the capacitors. However, this impedance analyzer has no problem for general capacitor products with a low Q value. When testing high-Q capacitors, due to the problem of the equipment accuracy of the impedance analyzer itself, it is difficult to accurately measure the Q value, and the ESR of products with a large capacitive reactance often measures a negative value. Another way is to use a Boonton 34A resonant cavity to test the ESR of the capacitors. Due to the design size and structure of the resonant cavity, the test range is from 100 MHz to 2 GHz, which cannot meet the component test in the nuclear magnetic resonance application frequency band (64 MHz). Therefore, how to perform ESR tests on capacitors in different application frequency bands is an urgent problem to be solved at present. Summary of the Invention

[0004] Some embodiments of the present application aim to provide a method for calculating the equivalent series resistance value of a capacitor and a test device for a resonant cavity. Through the technical solution of the embodiments of the present application, by obtaining a first tangent of the loss angle, a first resonant frequency at a preset wavelength, a second tangent of the loss angle, and a second resonant frequency at the preset wavelength; determining the equivalent series resistance value of the capacitor to be measured according to the first tangent of the loss angle, the second tangent of the loss angle, the first resonant frequency, and the second resonant frequency; wherein the first tangent of the loss angle and the first resonant frequency at the preset wavelength are resonant cavity parameters obtained when the capacitor to be measured is not installed in the test device of the resonant cavity, and the second tangent of the loss angle and the second resonant frequency at the preset wavelength are resonant cavity parameters obtained when the capacitor to be measured is installed in the test device of the resonant cavity. In the embodiments of the present application, by obtaining the resonant cavity parameters when the capacitor to be measured is installed or not installed in the test device of the resonant cavity, and then calculating the equivalent series resistance value of the capacitor to be measured at the preset wavelength according to the resonant cavity parameters in different situations, the ESR test for different application frequency bands can be adapted.

[0005] In a first aspect, some embodiments of the present application provide a method for calculating the equivalent series resistance value of a capacitor, including:

[0006] Obtaining a first tangent of the loss angle, a first resonant frequency at a preset wavelength, a second tangent of the loss angle, and a second resonant frequency at the preset wavelength;

[0007] Determining the equivalent series resistance value of the capacitor to be measured according to the first tangent of the loss angle, the second tangent of the loss angle, the first resonant frequency, and the second resonant frequency;

[0008] Wherein, the first tangent of the loss angle and the first resonant frequency at the preset wavelength are resonant cavity parameters obtained when the capacitor to be measured is not installed in the test device of the resonant cavity, and the second tangent of the loss angle and the second resonant frequency at the preset wavelength are resonant cavity parameters obtained when the capacitor to be measured is installed in the test device of the resonant cavity.

[0009] Some embodiments of the present application obtain the resonant cavity parameters when the capacitor to be measured is installed or not installed in the test device of the resonant cavity, and then calculate the equivalent series resistance value of the capacitor to be measured at the preset wavelength according to the resonant cavity parameters in different situations, so as to adapt to the ESR test for different application frequency bands.

[0010] Optionally, the determining the equivalent series resistance value of the capacitor to be measured according to the first tangent of the loss angle, the second tangent of the loss angle, the first resonant frequency, and the second resonant frequency includes:

[0011] Determine the loss tangent value of the capacitance under test according to the second loss tangent value, the first resonance frequency, and the second resonance frequency;

[0012] Determine the corresponding relationship between the capacitance value of the capacitance under test and the equivalent capacitance value of the resonant cavity according to the first resonance frequency and the second resonance frequency;

[0013] Determine the equivalent series resistance value of the capacitance to be measured according to the loss tangent value of the capacitance under test, the corresponding relationship between the capacitance value of the capacitance under test and the equivalent capacitance value of the resonant cavity, and the second resonance frequency.

[0014] Some embodiments of the present application respectively obtain the resonant cavity parameters in the case where the capacitance to be measured is not installed or the capacitance to be measured is installed in the test device of the resonant cavity, and then calculate the equivalent series resistance value of the capacitance to be measured according to the resonant cavity parameters. Based on the test device of the resonant cavity of the present application, a simpler calculation method can be used to calculate the equivalent series resistance value of the capacitance at different operating frequencies.

[0015] Optionally, the calculation formula for the equivalent series resistance value of the capacitance to be measured is as follows:

[0016]

[0017] Where: ESR(F X ) is the equivalent series resistance value of the capacitance to be measured, tanδ x is the loss tangent value of the capacitance under test, tanδ is the second loss tangent value, tanδ short is the first loss tangent value, F X is the second resonance frequency, F short is the first resonance frequency.

[0018] Some embodiments of the present application obtain the loss tangent value, the second loss tangent value, the first loss tangent value, and the first resonance frequency of the capacitance under test through instrument testing, and calculate the equivalent series resistance value of the capacitance. In this way, a simpler calculation method can be used to calculate the equivalent series resistance value of the capacitance at different operating frequencies.

[0019] Optionally, the obtaining of the first loss tangent value, the first resonance frequency of the preset wavelength, the second loss tangent value, and the second resonance frequency of the preset wavelength includes:

[0020] Obtain the first loss tangent value, the first resonance frequency of the preset wavelength, the second loss tangent value, and the second resonance frequency of the preset wavelength respectively through a vector network analyzer.

[0021] In some embodiments of the present application, a test device of a resonant cavity is connected to a vector network analyzer. Without installing the capacitor under test in the test device of the resonant cavity, the parameters of the resonant cavity are collected. Then, the capacitor under test is installed in the test device of the resonant cavity, and the parameters of the resonant cavity are collected again. In this way, the equivalent series resistance value of the capacitor under test is calculated based on the parameters of the resonant cavity collected twice.

[0022] In a second aspect, some embodiments of the present application provide a test device of a resonant cavity. The test device of the resonant cavity includes: an outer conductor, an inner conductor, and a fixture plunger. The outer conductor and the inner conductor are insulated from each other. The inner conductor and the fixture plunger are installed inside the outer conductor. The inner conductor and the fixture plunger correspond to each other. The capacitor under test is installed between the inner conductor and the plunger. A connection port is provided on the outer conductor, and the connection port is respectively connected to a vector network analyzer. The test device of the resonant cavity is used to execute the method for calculating the equivalent series resistance value of the capacitor as described in any one of the claims in the first aspect.

[0023] Optionally, the inner conductor is of a hollow structure, and the thickness of the inner conductor is determined according to the magnetic permeability of the conductor, the conductivity of the conductor, and the angular frequency.

[0024] Optionally, the thickness of the inner conductor is obtained by the following method:

[0025] According to the magnetic permeability of the conductor, the conductivity of the conductor, and the angular frequency of the inner conductor, calculate the skin depth value corresponding to the inner conductor;

[0026] According to the skin depth value, determine the thickness of the inner conductor.

[0027] In some embodiments of the present application, according to the calculated skin depth value, the inner conductor is processed into a hollow structure to reduce the weight of the inner conductor and the cost of the inner conductor.

[0028] Optionally, the first end of the inner conductor is in the shape of a trapezoidal column, the first end of the fixture plunger is in the shape of a trapezoidal column, the first end of the inner conductor is connected to the first end of the fixture plunger through the capacitor under test, and the second ends of the inner conductor and the fixture plunger are respectively connected to the outer conductor, and the size of the trapezoidal column on the side connected to the capacitor under test is the same as the size of the capacitor under test.

[0029] In some embodiments of the present application, by improving the structure of the inner conductor, the impedance at the connection between the conductor and the capacitor under test changes smoothly, reducing the test error caused by impedance mismatch due to structural mutation.

[0030] Optionally, slots are provided on the first end of the inner conductor and the first end of the fixture plunger, and the slots are used to install the capacitor under test.

[0031] In some embodiments of the present application, through the groove design at the connection, different types of capacitors can be tested, and the ability to test chip capacitors and lead capacitors is provided.

[0032] Optionally, the outer conductor is provided with a first input connection port, a second input connection port, and an output connection port, wherein the first input connection port and the second input connection port are determined according to different capacitance values of the capacitor to be tested.

[0033] In some embodiments of the present application, by providing sockets with high and low capacitance values on the outer conductor, in this way, capacitors with different capacitance values can be tested. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the technical solutions of some embodiments of the present application, the drawings required to be used in some embodiments of the present application will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application, and therefore should not be regarded as limiting the scope. For those of ordinary skill in the art, without creative efforts, other related drawings can also be obtained based on these drawings.

[0035] Figure 1 It is a schematic flow chart of a method for calculating the equivalent series resistance value of a capacitor provided by an embodiment of the present application;

[0036] Figure 2 It is a schematic structural diagram of a test device for a resonant cavity provided by an embodiment of the present application;

[0037] Figure 3 It is an equivalent schematic diagram of a resonant cavity provided by an embodiment of the present application;

[0038] Figure 4 It is a schematic structural diagram of another test device for a resonant cavity provided by an embodiment of the present application;

[0039] Figure 5 It is a schematic structural diagram of yet another test device for a resonant cavity provided by an embodiment of the present application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0040] Next, the technical solutions in some embodiments of the present application will be described in conjunction with the drawings in some embodiments of the present application.

[0041] It should be noted that: similar reference numerals and letters denote similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings. At the same time, in the description of the present application, the terms "first", "second", etc. are only used for distinguishing descriptions and cannot be understood as indicating or implying relative importance.

[0042] Applications of Nuclear Magnetic Resonance Magnetic Resonance Imaging (MRI) examination has become a common imaging examination method. As a new imaging examination technology, MRI has no impact on human health. Currently, the commonly used MRI equipment in clinical practice uses hydrogen atom resonance, and its resonance frequency is 42.58 MHz / T. At a magnetic field strength of 1.5 T, the working frequency of MRI is 64 MHz (42.58 MHz / T * 1.5 T).

[0043] Currently, an impedance analyzer can be used to detect the capacitors in the equipment. This impedance analyzer is used to test the ESR (Equivalent Series Resistance) of the capacitors. However, this impedance analyzer has no problem for general capacitor products with a low Q value. When testing high-Q capacitors, due to the problem of the equipment accuracy of the impedance analyzer itself, it is difficult to accurately measure the Q value, and the ESR of products with a large capacitive reactance often shows a negative value. Another method is to use a Boonton 34A resonator to test the ESR of the capacitors. Due to the design size and structure of the resonator, the test range is from 100 MHz to 2 GHz, which cannot meet the component tests in the nuclear magnetic resonance application frequency band (64 MHz). Therefore, how to perform ESR tests on capacitors in different application frequency bands is an urgent problem to be solved at present. In view of this, some embodiments of the present application provide a method for calculating the equivalent series resistance value of a capacitor, and the method includes: obtaining a first tangent of the loss angle, a first resonance frequency of a preset wavelength, a second tangent of the loss angle, and a second resonance frequency of a preset wavelength; determining the equivalent series resistance value of the capacitor to be tested according to the first tangent of the loss angle, the second tangent of the loss angle, the first resonance frequency, and the second resonance frequency; wherein, the first tangent of the loss angle and the first resonance frequency of the preset wavelength are the resonator parameters obtained when the capacitor to be tested is not installed in the test device of the resonator, and the second tangent of the loss angle and the second resonance frequency of the preset wavelength are the resonator parameters obtained when the capacitor to be tested is installed in the test device of the resonator. In the embodiments of the present application, by obtaining the resonator parameters when the capacitor to be tested is installed or not installed in the test device of the resonator, and then calculating the equivalent series resistance value of the capacitor to be tested at the preset wavelength according to the resonator parameters in different situations, the ESR test for different application frequency bands can be adapted.

[0044] As Figure 1 shown, the embodiments of the present application provide a method for calculating the equivalent series resistance value of a capacitor, and the method includes:

[0045] S101. Obtain a first tangent of the loss angle, a first resonance frequency of a preset wavelength, a second tangent of the loss angle, and a second resonance frequency of a preset wavelength;

[0046] Among them, the first tangent of the loss angle and the first resonant frequency at the preset wavelength are the resonant cavity parameters obtained when the capacitance under test is not installed in the test device of the resonant cavity, and the second tangent of the loss angle and the second resonant frequency at the preset wavelength are the resonant cavity parameters obtained when the capacitance under test is installed in the test device of the resonant cavity.

[0047] Specifically, an embodiment of the present application provides a test device for a resonant cavity. The test device for the resonant cavity is connected to a vector network analyzer. First, when the capacitance under test is not installed in the test device of the resonant cavity, the first tangent of the loss angle and the first resonant frequency at the preset wavelength are obtained through the vector network analyzer. Then, according to the capacitance value of the capacitance under test, the capacitance under test is installed in the test device of the resonant cavity, and the second tangent of the loss angle and the second resonant frequency at the preset wavelength are obtained through the vector network analyzer.

[0048] S102. Determine the equivalent series resistance value of the capacitance under test according to the first tangent of the loss angle, the second tangent of the loss angle, the first resonant frequency, and the second resonant frequency;

[0049] Specifically, according to the obtained first tangent of the loss angle, the second tangent of the loss angle, the first resonant frequency, and the second resonant frequency, a preset algorithm is used to calculate the equivalent series resistance value to be measured.

[0050] Exemplarily, the preset algorithm can be

[0051] Among them: ESR(F X ) is the equivalent series resistance value of the capacitance under test, tanδ x is the tangent of the loss angle of the capacitance under test, tanδ is the second tangent of the loss angle, tanδ short is the first tangent of the loss angle, δ X is the second resonant frequency, F short is the first resonant frequency.

[0052] Some embodiments of the present application obtain the resonant cavity parameters by whether the capacitance under test is installed in the test device of the resonant cavity, and then calculate the equivalent series resistance value of the capacitance under test at the preset wavelength according to the resonant cavity parameters in different situations, so as to adapt to the ESR test of different application frequency bands.

[0053] Another embodiment of the present application further supplements and explains the calculation method of the equivalent series resistance value of the capacitance provided in the above embodiment.

[0054] Optionally, determining the equivalent series resistance value of the capacitance under test according to the first tangent of the loss angle, the second tangent of the loss angle, the first resonant frequency, and the second resonant frequency includes:

[0055] Determine the tangent of the loss angle of the capacitance under test according to the second tangent of the loss angle, the first resonance frequency, and the second resonance frequency;

[0056] Determine the corresponding relationship between the capacitance value of the capacitance under test and the equivalent capacitance value of the resonant cavity according to the first resonance frequency and the second resonance frequency;

[0057] Determine the equivalent series resistance value of the capacitance to be measured according to the tangent of the loss angle of the capacitance under test, the corresponding relationship between the capacitance value of the capacitance under test and the equivalent capacitance value of the resonant cavity, and the second resonance frequency.

[0058] Some embodiments of the present application calculate the equivalent series resistance value of the capacitance to be measured by respectively obtaining the resonant cavity parameters when the capacitance to be measured is not installed or the capacitance to be measured is installed in the test device of the resonant cavity, and then according to the resonant cavity parameters. Based on the test device of the resonant cavity of the present application, a simpler calculation method can be used to calculate the equivalent series resistance value of the capacitance at different operating frequencies.

[0059] Optionally, the calculation formula for the equivalent series resistance value of the capacitance to be measured is as follows:

[0060]

[0061] Where: ESR(F X ) is the equivalent series resistance value of the capacitance to be measured, tanδ x is the tangent of the loss angle of the capacitance under test, tanδ is the second tangent of the loss angle, tanδ short is the first tangent of the loss angle, F X is the second resonance frequency, F short is the first resonance frequency.

[0062] Some embodiments of the present application obtain the tangent of the loss angle of the capacitance under test, the second tangent of the loss angle, the first tangent of the loss angle, and the first resonance frequency through instrument testing, and calculate the equivalent series resistance value of the capacitance. In this way, a simpler calculation method can be used to calculate the equivalent series resistance value of the capacitance at different operating frequencies.

[0063] Optionally, obtaining the first tangent of the loss angle, the first resonance frequency of the preset wavelength, the second tangent of the loss angle, and the second resonance frequency of the preset wavelength includes:

[0064] Obtain the first tangent of the loss angle, the first resonance frequency of the preset wavelength, the second tangent of the loss angle, and the second resonance frequency of the preset wavelength respectively through a vector network analyzer.

[0065] As Figure 3As shown, it is a schematic diagram of a resonant cavity and its equivalent circuit, where L is the equivalent inductance of the resonant cavity, Cs is the equivalent capacitance of the resonant cavity, and Cx is the capacitance to be measured. Cs and Cx are in series, and the self-inductance of the capacitance to be measured is not considered in this calculation.

[0066] The principle formula for the calculation of the resonant cavity is:

[0067] The total energy storage U of the circuit S = U 0 + U C , U 0 is the energy storage of the resonant cavity itself, and U C is the energy storage of the capacitance to be measured;

[0068] The total power consumption P S = P 0 + P C , P 0 is the power consumption of the resonant cavity itself, and P C is the power consumption of the capacitance to be measured;

[0069] The Q value of the resonant cavity system with the capacitance to be measured loaded:

[0070] The Q value of the resonant cavity Q 0 = U 0 / P 0 ;

[0071] The Q value of the capacitance to be measured Q C = U C / P C ;

[0072] The relationship between the loss tangent and the Q value is tanδ = 1 / Q;

[0073] Specifically, in the embodiment of the present application: U 0 is expressed as U short , and U C is expressed as U X .

[0074] The total energy storage U of the circuit S = U short + U X , U short is the energy storage of the resonant cavity itself, and U X is the energy storage of the capacitance to be measured;

[0075] The total power consumption P S = P short + P X , P short is the power consumption of the resonant cavity itself, and P X is the power consumption of the capacitance to be measured;

[0076] The Q value of the resonant cavity system with the capacitance to be measured loaded:

[0077] Resonator Q value Q short = U short / P short ;

[0078] Measured capacitance Q value Q X = U X / P X ;

[0079] Relationship between loss tangent and Q value tanδ = 1 / Q;

[0080] Derived

[0081]

[0082] Where: tanδ x is the loss tangent of the measured capacitance, tanδ is the loss tangent of the resonator system loaded with the measured capacitance (the second loss tangent value), tanδ short is the loss tangent of the resonator itself (the first loss tangent value), F X is the λ / 4 resonance frequency of the resonance system after loading the measured capacitance (the second resonance frequency), F short is the λ / 4 resonance frequency of the resonator itself (the first resonance frequency).

[0083] This ESR calculation method is simpler than the traditional resonator algorithm and is suitable for engineering tests. In the formula, it is considered that the measured capacitance is in an ideal situation and the self-inductance is ignored. In actual situations, the capacitance value increases with the increase of frequency and approaches the self-resonance frequency of the capacitance. The self-equivalent inductance of the capacitance can no longer be ignored. Therefore, this calculation method requires the test frequency to be far from the self-resonance frequency of the capacitance, and the accuracy is relatively high. The NMR working frequency band of 64 MHz is lower than the self-resonance frequencies of most capacitors.

[0084] The NMR working frequency band capacitance element resonator test provided by the embodiments of the present application can calculate parameters such as the 64 MHz ESR value of a high-Q capacitor through the design of the resonator size and structure and the use of a vector network analyzer, and can achieve accurate performance testing of the capacitance element in a specific working frequency band of MRI.

[0085] In some embodiments of the present application, the test device of the resonator is connected to a vector network analyzer. When the test capacitor is not installed in the test device of the resonator, the parameters of the resonator are collected, and then the test capacitor is installed in the test device of the resonator, and the parameters of the resonator are collected again. In this way, the equivalent series resistance value of the test capacitor is calculated through the parameters of the resonator collected twice.

[0086] It should be noted that in this embodiment, each feasible implementation method can be implemented independently, or can be combined in any combination without conflict. The present application does not make any limitations.

[0087] Another embodiment of the present application provides a calculation device for the capacitance equivalent series resistance value. The test device of the resonant cavity includes: an outer conductor, an inner conductor, and a fixture plunger. The outer conductor and the inner conductor are insulated from each other. The inner conductor and the fixture plunger are installed inside the outer conductor. The inner conductor and the fixture plunger correspond to each other. A capacitor under test is installed between the inner conductor and the plunger. A connection port is provided on the outer conductor, and the connection port is respectively connected to a vector network analyzer. The test device of the resonant cavity is used to execute the capacitance equivalent series resistance value calculation method of any one of the above-mentioned claims.

[0088] Optionally, the inner conductor is of a hollow structure, and the thickness of the inner conductor is determined according to the conductor permeability, conductor conductivity, and angular frequency.

[0089] Optionally, the thickness of the inner conductor is obtained by the following method:

[0090] Calculate the skin depth value corresponding to the inner conductor according to the conductor permeability, conductor conductivity, and angular frequency of the inner conductor;

[0091] Determine the thickness of the inner conductor according to the skin depth value.

[0092] Among them, according to the different materials of the inner conductor, obtain the conductor permeability, conductor conductivity, and angular frequency of the inner conductor, and then according to the skin effect formula as follows:

[0093]

[0094] Δ is the skin depth, ω is the angular frequency, μ is the conductor permeability, γ is the conductor conductivity, and calculate the skin effect value of the inner conductor.

[0095] According to the calculated skin effect value, in the case of being greater than the skin effect value, determine the thickness that the inner conductor can be set. That is to say, the thickness of the inner conductor is greater than the skin effect value. In this way, in order not to affect the performance index of the resonant cavity, the inner conductor is hollowed out. In this way, both cost is saved and the weight of the inner conductor is reduced.

[0096] Exemplarily, the skin depth of copper at 64 MHz is about 8.27 um. Therefore, the outer wall thickness of the inner conductor is greater than 8.27 um, which does not affect the performance index of the resonant cavity. In the embodiment of the present application, the thickness of the inner conductor is designed to be 3 mm, which is much greater than the skin depth value.

[0097] In some embodiments of the present application, according to the calculated skin depth value, the inner conductor is hollowed out to reduce the weight of the inner conductor and the cost of the inner conductor.

[0098] Optionally, the first end of the inner conductor is in the shape of a trapezoidal column, the first end of the fixture plunger is in the shape of a trapezoidal column, the first end of the inner conductor is connected to the first end of the fixture plunger through the capacitance to be measured, the second ends of the inner conductor and the fixture plunger are respectively connected to the outer conductor, and the dimensions of the trapezoidal column on the side connected to the capacitance to be measured are the same as those of the capacitance to be measured.

[0099] Specifically, a trapezoidal column design is adopted at the capacitance connection (first end) of the inner conductor. The first end of the fixture plunger is in the shape of a trapezoidal column and smoothly transitions to a dimension close to the width of the capacitance, reducing the negative impact caused by impedance mutation. At the same time, grooves are engraved at both ends of the connector, and the thickness of the groove body is the same as the thickness of the capacitance lead, meeting the requirements of lead capacitance testing. It is also possible to directly connect the two ends of the capacitance to the inner conductor to test the chip capacitance. The connection structure of the inner conductor is as Figure 4 and Figure 5 shown.

[0100] Among them, the fixture plunger can be adjusted according to the length of the capacitance to be measured.

[0101] In some embodiments of the present application, by improving the structure of the inner conductor, the impedance at the connection between the conductor and the capacitance to be measured changes smoothly, reducing the test error caused by impedance mismatch due to structural mutation.

[0102] Optionally, slots are provided on the first ends of the inner conductor and the fixture plunger, and the slots are used to install the capacitance to be measured.

[0103] In some embodiments of the present application, through the groove design at the connection, different types of capacitances can be tested, and the test capabilities of chip capacitance and lead capacitance are available.

[0104] In particular, the capacitance to be measured can be a leaded capacitance or a leadless capacitance. Thus, if the capacitance to be measured is a leadless capacitance, the first ends of the inner conductor and the fixture plunger are used to clamp the capacitance to be measured in the middle; if the capacitance to be measured is a leaded capacitance, a slot is provided on the inner conductor, and in this way, the lead of the leaded capacitance can be inserted into the slot for easy installation.

[0105] In the embodiments of the present application, by improving the structure of the inner conductor, the impedance at the connection between the conductor and the capacitance to be measured changes smoothly, reducing the test error caused by impedance mismatch due to structural mutation. At the same time, with the groove design at the connection, the resonant cavity test system has the ability to test chip capacitance and lead capacitance.

[0106] Optionally, the outer conductor is provided with a first input connection port, a second input connection port, and an output connection port. Among them, the first input connection port and the second input connection port are determined according to different capacitance values of the capacitance to be measured.

[0107] An embodiment of the present application provides a resonant cavity applied to the test of nuclear magnetic resonance capacitive elements, such as Figure 2 shown, including: a fixture plunger, an inner conductor, P 1 The excitation end is connected to one port of the vector network, i.e., the first input connection port (P 1,a The toroidal coil (RF connector) is connected to the outer conductor, which is in the form of magnetic coupling and is suitable for large capacitance value tests; P 1,b The small coupling antenna, i.e., the second input connection port, is in the form of electric coupling and is suitable for small capacitance value tests), P 2 The receiving end, i.e., the output connection port, is connected to the second port of the vector network and is connected to the instrument, and the vector network is connected one.

[0108] The open end of the resonant cavity S 1 = 200 mm, the length of the inner conductor S 2 = 1170 mm, the installation distance of the capacitor under test S 3 , rotate the inner conductor plug S 4 The length is adjustable by bolts and depends on the size of the capacitor under test. The diameter of the inner conductor d = 28 mm, the diameter of the outer conductor D = 200 mm, the total length of the outer conductor S = 1445 mm, and the wall thickness of the inner and outer conductors is 3 mm.

[0109] According to the nuclear magnetic resonance frequency band, at a magnetic field strength of 1.5 T, the operating frequency of MRI is 64 MHz. The size of the resonant cavity is designed according to the operating frequency of MRI at 64 MHz. The first resonant point of the resonant cavity is 1 / 4λ. The resonant cavity needs to be tested up to the 64 MHz frequency band, and the 1 / 4 wavelength resonant frequency needs to fall within the 64 MHz frequency band.

[0110] According to C = λ / T = λ·f

[0111] where C is the speed of light, λ is the wavelength, T is the period, and f is the frequency

[0112] It can be obtained that when the 1 / 4 wavelength resonant frequency is 64 MHz, it can be calculated that λ = 4.68 m. When the size of the inner conductor in the resonant cavity is 1 / 4 of the wavelength, i.e., 1.17 m, it can achieve resonance at the 1 / 4 wavelength, that is, the resonant frequency of the first resonant point is 64 MHz, meeting the requirements of the MRI frequency band.

[0113] In some embodiments of the present application, by providing sockets with high and low capacitance values on the outer conductor, in this way, capacitors with different capacitance values can be tested.

[0114] An embodiment of the present application provides a resonant cavity applied to the test of nuclear magnetic resonance capacitance elements. By using a vector network analyzer, this method can calculate parameters such as the ESR and Q value in the nuclear magnetic resonance application frequency band of high-Q capacitors. Compared with the original resonant cavity, the inner conductor is improved, the impedance change at the connection is smooth, and the cavity weight is reduced without affecting the test value. The new resonant cavity can not only test chip capacitors but also capacitors with leads. An embodiment of the present application also provides a relatively simple ESR calculation method.

[0115] Regarding the device in this embodiment, the specific manner in which each module performs operations has been described in detail in the embodiment related to the method, and will not be elaborated here.

[0116] It should be noted that each feasible manner in this embodiment can be implemented separately or in any combination manner without conflict. The present application does not make any limitations.

[0117] The above are only the embodiments of the present application and are not used to limit the protection scope of the present application. For those skilled in the art, the present application can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application. It should be noted that similar reference numerals and letters indicate similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0118] The above is only the specific implementation manner of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art can easily think of changes or replacements within the technical scope disclosed by the present application, and all should be covered by the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

[0119] It should be noted that in this article, 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 variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes 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 "including a..." does not exclude the existence of additional identical elements in the process, method, article or device including the element.

Claims

1. A method for calculating the equivalent series resistance of a capacitor, characterized in that: The method comprises: Obtaining a first loss tangent value, a first resonant frequency of a preset wavelength, a second loss tangent value, and a second resonant frequency of the preset wavelength; Determine an equivalent series resistance value of the capacitor to be measured according to the first loss tangent value, the second loss tangent value, the first resonant frequency, and the second resonant frequency; Among them, the first loss tangent value and the first resonant frequency of the preset wavelength are resonant cavity parameters obtained when the capacitor to be measured is not installed in the test device of the resonant cavity, and the second loss tangent value and the second resonant frequency of the preset wavelength are resonant cavity parameters obtained when the capacitor to be measured is installed in the test device of the resonant cavity.

2. The method for calculating the capacitor equivalent series resistance value according to claim 1, characterized in that: The determining the equivalent series resistance value of the capacitor to be measured according to the first loss tangent value, the second loss tangent value, the first resonant frequency, and the second resonant frequency includes: Determining a loss tangent value of the measured capacitor according to the second loss tangent value, the first resonant frequency, and the second resonant frequency; Determining a corresponding relationship between a capacitance value of the measured capacitor and an equivalent capacitance value of the resonant cavity according to the first resonant frequency and the second resonant frequency; The equivalent series resistance value of the capacitor to be measured is determined according to the loss tangent value of the capacitor to be measured, the corresponding relationship between the capacitance value of the capacitor to be measured and the equivalent capacitance value of the resonant cavity, and the second resonant frequency.

3. The method for calculating the capacitor equivalent series resistance value according to claim 2, characterized in that: The calculation formula of the equivalent series resistance value of the capacitor to be measured is as follows: Where: ESR(F X ) is the equivalent series resistance of the capacitor to be measured, tanδ x is the loss tangent value of the measured capacitor, tanδ is the second loss tangent value, tanδ short is the first loss tangent, F X is the second resonant frequency, F short is the first resonant frequency.

4. The method for calculating the capacitor equivalent series resistance value according to claim 1, characterized in that: The obtaining of the first loss tangent value, the first resonant frequency of the preset wavelength, the second loss tangent value, and the second resonant frequency of the preset wavelength includes: The first loss tangent value, the first resonant frequency of the preset wavelength, the second loss tangent value and the second resonant frequency of the preset wavelength are respectively obtained by a vector network analyzer.

5. A resonant cavity testing device, characterized in that: The test device of the resonant cavity includes: an outer conductor, an inner conductor and a fixture plunger, the outer conductor and the inner conductor are insulated, the inner conductor and the fixture plunger are installed inside the outer conductor, the inner conductor and the fixture plunger correspond to each other, and the capacitor to be measured is installed between the inner conductor and the plunger; the outer conductor is provided with a connection port, and the connection port is respectively connected to a vector network analyzer. The test device of the resonant cavity is used to execute the method for calculating the equivalent series resistance value of the capacitor as described in any one of claims 1 to 4.

6. The resonant cavity testing device according to claim 5, characterized in that: The inner conductor is a hollow structure, and the thickness of the inner conductor is determined according to the magnetic permeability, electrical conductivity and angular frequency of the conductor.

7. The resonant cavity testing device according to claim 6, characterized in that The thickness of the inner conductor is obtained by: Calculating a skin depth value corresponding to the inner conductor according to the conductor magnetic permeability, the conductor electrical conductivity and the angular frequency of the inner conductor; The thickness of the inner conductor is determined according to the skin depth value.

8. The resonant cavity testing device according to claim 5, characterized in that: The first end of the inner conductor is in the shape of a trapezoidal column, the first end of the fixture plunger is in the shape of a trapezoidal column, the first end of the inner conductor is connected to the first end of the fixture plunger through the capacitor to be measured, the second end of the inner conductor and the second end of the fixture plunger are respectively connected to the outer conductor, and the size of the trapezoidal column on the side connected to the capacitor to be measured is consistent with the size of the capacitor to be measured.

9. The resonant cavity testing device according to claim 5, characterized in that: A slot is provided on the first end of the inner conductor and the first end of the fixture plunger, and the slot is used to install the capacitor to be measured.

10. The resonant cavity testing device according to claim 5, characterized in that: The outer conductor is provided with a first input connection port, a second input connection port and an output connection port, wherein the first input connection port and the second input connection port are determined according to different capacitance values ​​of the capacitor to be measured.

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