A sensor for characterizing electromagnetic parameters of a magnetic fluid

Abstract

This invention discloses a sensor for characterizing the electromagnetic parameters of magnetohydrodynamic materials, belonging to the field of microwave testing technology. The sensor includes a dielectric substrate, a ground plane, an improved complementary split-ring resonator unit etched on the ground plane, and multiple magnetic cavity pin structures. A hollowed-out cavity for accommodating the magnetohydrodynamic material is provided on the substrate. The magnetic cavity pins actively isolate the electric and magnetic field regions, forming mutually separated dielectric and magnetic sensitive regions on the sensor. By placing the sample in different sensitive regions, and based on perturbation theory, the complex permittivity and complex permeability of the sample can be decoupled and calculated by measuring the resonant frequency shift. This invention effectively suppresses electromagnetic coupling effects, achieving highly sensitive and quantitative characterization of the complex electromagnetic parameters of magnetohydrodynamic materials, and is particularly suitable for magnetohydrodynamic materials with fluidity and complex electromagnetic parameters.

Description

Technical Field

[0001] This invention belongs to the field of microwave testing technology, specifically, it relates to a sensor for characterizing the electromagnetic parameters of a magnetohydrodynamic fluid. Background Technology

[0002] Magnetofluids are colloidal suspensions composed of magnetic nanoparticles dispersed in a carrier liquid. They have significant applications in high-frequency 5G / 6G communications, radar stealth technology, and electromagnetic shielding. However, magnetofluids exhibit complex electromagnetic properties. The inherent electromagnetic coupling effect poses a major challenge in characterizing these materials, affecting the reliability of measurement results. Traditionally, planar resonant sensors for magnetic materials address electromagnetic coupling issues by employing electromagnetic field isolation techniques to characterize the dielectric constant and permeability separately. Among these methods, complementary split-ring resonators (CSRRs) have received considerable attention in sensor design due to their inherent non-uniform field distribution. However, due to the inherent fluidity of magnetofluids, few sensors are suitable for characterizing their electromagnetic parameters using this method.

[0003] This application proposes a novel sensor design based on CSRR and a magnetic cavity pin structure. The basic layout of the sensor has been structurally modified to characterize magnetohydrodynamics, thereby improving the sensor's electromagnetic coupling immunity and high sensitivity to changes in dielectric constant and permeability parameters. Summary of the Invention

[0004] The purpose of this invention is to provide a sensor for characterizing the electromagnetic parameters of magnetohydrodynamic materials, solving the problem in the prior art of decoupling and highly sensitive characterizing the complex permittivity and complex permeability of magnetohydrodynamic materials.

[0005] The objective of this invention can be achieved through the following technical solutions: A sensor for characterizing electromagnetic parameters of a magnetohydrodynamic fluid, comprising: A dielectric substrate having a hollowed-out cavity for accommodating a magnetofluid sample to be tested; A grounding plane is located on the dielectric substrate; CSRR cells are etched on the ground plane; Multiple magnetic cavity pin structures are used to isolate the electric and magnetic field regions generated by the CSRR unit; The hollow cavity, CSRR unit, and magnetic cavity pin structure work together to form a dielectric sensitive area and a magnetic sensitive area that are separated from each other on the sensor, so as to place the sample to be tested to cause electric field disturbance or magnetic field disturbance, respectively. The magnetic cavity pin structure is a 0.5mm diameter copper cylinder that penetrates the dielectric substrate from the ground plane. The magnetic cavity pin structure is arranged with a spacing of 0.8mm parallel to the complex permeability measurement area and a spacing of 0.6mm perpendicular to the complex permeability measurement area.

[0006] As a further aspect of the present invention, the dielectric sensitive region is a strong electric field region determined by simulation or experiment, used to characterize the complex dielectric constant of the sample; The magnetically sensitive region is a strong magnetic field region determined by simulation or experiment, used to characterize the complex permeability of the sample.

[0007] As a further aspect of the present invention, the resonant frequency of the sensor shifts with the change in the dielectric constant and / or magnetic permeability of the sample placed in the dielectric sensitive region and / or magnetic sensitive region.

[0008] As a further aspect of the present invention, the sensor calculates the real part of the dielectric constant and magnetic permeability of the ferromagnetic fluid under test by measuring the resonant frequency shift before and after the sample is loaded.

[0009] This invention also discloses a method for characterizing magnetohydrodynamic electromagnetic parameters based on the above-mentioned sensor, comprising the following steps: Step 1: Inject the magnetic fluid sample to be tested into the hollowed-out cavity of the dielectric substrate, so that it is located in the dielectric sensitive region of the sensor; Step 2: Measure the resonant frequency of the sensor and calculate the offset Δf relative to the resonant frequency when no sample is loaded. r电 and resonance depth ΔS 21电 ; Step 3: Using the measured Δf r电 The real part of the complex permittivity of the sample under test is obtained by inversion, and then ΔS is used to obtain the real part of the complex permittivity of the sample under test. 21电 The imaginary part of the sample under test is obtained through inversion; Step 4: Inject the magnetofluid sample to be tested into the hollowed-out cavity of the dielectric substrate, so that it is located in the permeability sensitive region of the sensor; Step 5: Measure the resonant frequency of the sensor and calculate the offset Δf relative to the resonant frequency when no sample is loaded. r磁 and resonance depth ΔS 21磁 ; Step 6: Using the measured Δf r磁 The real part of the complex permeability of the sample under test is obtained by inversion, and then obtained through ΔS. 21电 The imaginary part of the sample to be tested is obtained through inversion.

[0010] The beneficial effects of this invention are: This invention combines a magnetic cavity pin structure with a hollowed-out substrate cavity, and achieves physical separation of the electric field region and magnetic field region inside the sensor through complementary resonant units. It can place the magnetic fluid sample to be tested in the dielectric sensitive region and the magnetic sensitive region respectively, thereby effectively suppressing the mutual interference between dielectric constant and magnetic permeability measurement, and realizing the decoupled characterization of complex dielectric constant and complex magnetic permeability of magnetic fluid.

[0011] The specially designed hollow cavity on the substrate can be used to accommodate fluid magnetofluid samples, solving the problem that traditional planar resonant sensors have difficulty characterizing fluid materials.

[0012] The sensor of this invention has a highly sensitive response to changes in dielectric constant and permeability, and has strong anti-electromagnetic coupling capability.

[0013] This invention establishes a quantitative fitting formula between resonant frequency shift and electromagnetic parameters based on simulation data, which can directly deduce the electromagnetic parameters of the magnetofluid based on the measurement results. Attached Figure Description

[0014] The invention will now be further described with reference to the accompanying drawings.

[0015] Figure 1 This is a schematic diagram of the structure of the sensor described in this invention; Figure 2 The diagrams show (a) H-field distribution and (b) E-field distribution of the sensor in this invention. Figure 3 This is a simulation diagram of the S-parameters in the unloaded state of the sensor in this invention; Figure 4 The figures show the simulation results under different electromagnetic parameters in this invention. Detailed Implementation

[0016] 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. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0017] Example 1

[0018] like Figure 1 As shown, a sensor for characterizing the electromagnetic parameters of a magnetohydrodynamic fluid includes: A dielectric substrate having a hollowed-out cavity for accommodating a magnetofluid sample to be tested; A ground plane is located on the dielectric substrate; A complementary split-ring resonator (CSRR) unit is etched on the ground plane; Multiple magnetic cavity pin structures are used to actively isolate the electric and magnetic field regions generated by the CSRR unit.

[0019] The sensor incorporates a hollow cavity, a CSRR unit, and a magnetic cavity pin structure to form separate dielectric and magnetic sensitive regions. The dielectric sensitive region is used to place the sample under test to primarily induce electric field disturbances, while the magnetic sensitive region is used to place the sample under test to primarily induce magnetic field disturbances. The magnetic cavity pin structure is a 0.5mm diameter copper cylinder that penetrates the dielectric substrate from the ground plane. The magnetic cavity pin structure is arranged with a spacing of 0.8mm parallel to the complex permeability measurement area and a spacing of 0.6mm perpendicular to the complex permeability measurement area.

[0020] Its working principle is as follows: When the sample to be tested is placed in the dielectric sensitive region and the magnetic sensitive region, respectively, the electric field (E field) and / or magnetic field (H field) distribution of the resonator is disturbed, thereby causing changes in the resonant frequency and quality factor of the sensor. By measuring the shift in the resonant frequency, the complex permittivity and complex permeability of the sample can be calculated, and then the real parts of the permittivity and permeability of the ferrofluid under test can be calculated. When used as a sensor for measuring complex permittivity, the measurement frequency band is 0.65GHz-0.78GHz, and the effective measurement range is for samples with a permittivity of 1-20 and an electrical loss tangent of 0-1. When used as a complex permeability measurement sensor, the measurement frequency band is 0.7GHz-0.78GHz, and the effective measurement range is for samples with a permeability of 1-2 and a magnetic loss tangent of 0-0.5. The complex permittivity includes the permittivity and the electrical loss tangent, and the complex permeability includes the permeability and the magnetic loss tangent.

[0021] Specifically, the sensor can be modeled as an LC equivalent circuit:

[0022] Its equivalent resonant inductance L r and equivalent resonant capacitance C r The value is determined by the perimeter of the CSRR structure, the size of the gap, and the overall shape; Among them, C c For coupling capacitor, f r It is the resonant frequency when unloaded; According to perturbation theory, the relationship between the change in resonant frequency and the sample characteristics is as follows:

[0023] Where, Δfr It is the frequency shift after the sample is loaded; ε is the permittivity, and μ is the permeability. ε0 and μ0 are the permittivity and permeability of free space; Δε = ε0(ε r -1) and Δμ = μ0(μ r -1) represents the changes in dielectric constant and permeability; E0 and H0 are the electric and magnetic fields when unloaded, E1 and H1 are the fields after perturbation; v is the perturbation volume.

[0024] In a preferred embodiment, strong electric field regions and strong magnetic field regions on the sensor are determined by electromagnetic simulation software, and are used as the measurement regions for dielectric constant and magnetic permeability, respectively.

[0025] Example 2

[0026] A sensor for characterizing the electromagnetic parameters of magnetohydrodynamics. Its dielectric substrate measures 40*20*7mm and is made of a synthetic ceramic material with a dielectric constant of 25 and a loss tangent of 0.004, making it effective for use with high-dielectric-value, high-loss magnetohydrodynamic materials.

[0027] A hollowed-out cavity is provided on the dielectric substrate to accommodate the magnetofluid sample to be tested.

[0028] The CSRR resonant unit is etched on the ground plane.

[0029] The magnetic cavity pin structure is used to actively isolate the resonant unit to achieve separation of the electric and magnetic field regions.

[0030] From an electrical perspective, this sensor can be modeled as an LC equivalent circuit, and its resonant characteristics are determined by the physical dimensions of the CSRR structure.

[0031] According to perturbation theory, when a sample is placed on a CSRR structure, it will disturb the E-field and H-field distributions of the resonator, causing changes in the resonant frequency and quality factor. From formula (2), it can be seen that if the sample is placed in the region where H0=0, the frequency change is determined only by the electric field perturbation; if it is placed in the region where E0=0, the frequency change is determined only by the magnetic field perturbation. The design of this invention is based on this principle, optimizing the structure to ensure that the strongest electric and magnetic fields appear in different regions, thereby achieving independent measurement of the dielectric constant and permeability.

[0032] The method for characterizing magnetohydrodynamic electromagnetic parameters using the aforementioned sensor includes the following steps: Step 1: Inject the magnetic fluid sample to be tested into the hollowed-out cavity of the dielectric substrate, so that it is located in the dielectric sensitive region of the sensor; Step 2: Measure the resonant frequency of the sensor and calculate the offset Δf relative to the resonant frequency when no sample is loaded. r电 and resonance depth ΔS 21电 ; Step 3: Using the measured Δf r电 The real part of the complex permittivity of the sample under test is obtained by inversion, and then ΔS is used to obtain the real part of the complex permittivity of the sample under test. 21电 The inversion yields the tangent of the electrical loss of the sample under test (imaginary part). Step 4: Inject the magnetofluid sample to be tested into the hollowed-out cavity of the dielectric substrate, so that it is located in the permeability sensitive region of the sensor; Step 5: Measure the resonant frequency of the sensor and calculate the offset Δf relative to the resonant frequency when no sample is loaded. r磁 and resonance depth ΔS 21磁 ; Step 6: Using the measured Δf r磁 The real part of the complex permeability of the sample under test is obtained by inversion, and then obtained through ΔS. 21电 The inversion yields the imaginary part of the magnetic loss tangent of the sample under test. Specifically: S1: Measure the complex permeability of the sample being tested. S11: Inject the magnetofluid sample to be tested into the permeability-reduced cavity of the dielectric substrate; S12: Under the resonance of the 0.7GHz-0.782GHz frequency band, the 5G planar electromagnetic sensor with mutual coupling ring gap is measured using a vector network analyzer to obtain the transmission coefficient center frequency S21 parameter curve; S13: Determine the resonant frequency and insertion loss of the S21 parameter curve; S14: Determine the permeability of the sample based on the resonant frequency, and determine the magnetic loss tangent of the magnetic fluid based on the insertion loss; S2: Measure the complex permittivity of the sample. S21: Inject the magnetic fluid sample to be tested into the dielectric constant cavity of the dielectric substrate; S22: Under resonance in the 0.65GHz-0.78GHz frequency band, the 5G planar electromagnetic sensor of the mutually coupled annular gap is measured using a vector network analyzer to obtain the transmission coefficient center frequency S21 parameter curve; S023: Determine the resonant frequency and insertion loss of the parameter curve in S21; S024: Determine the dielectric constant of the sample under test based on the resonant frequency, and determine the electrical loss tangent of the magnetofluid sample based on the insertion loss.

[0033] Example 3: Simulation Verification and Results The sensor in this embodiment was simulated and analyzed using the commercial electromagnetic simulation software HFSS.

[0034] Figure 2 The field distribution of the sensor is shown.

[0035] from Figure 2 (a) It can be seen that the magnetic field has a high intensity in the dashed region, so this region is suitable for measuring magnetic permeability.

[0036] from Figure 2 (b) It can be seen that the electric field has a higher intensity in the solid line region, which is suitable for measuring the dielectric constant.

[0037] Thus, the regions for measuring dielectric constant and permeability have been successfully separated and determined.

[0038] like Figure 4 As shown, changes in the dielectric constant do not significantly alter the transmission response in the permeability measurement region.

[0039] Similarly, the change in magnetic permeability has little effect on the measurement of dielectric constant, indicating that this sensor has good anti-electromagnetic coupling capability.

[0040] The sensor was first simulated in an unloaded state, and the corresponding S-parameters were as follows: Figure 3 As shown.

[0041] Subsequently, parameter scanning was performed by introducing samples with different magnetic permeabilities into the magnetically sensitive region and samples with different dielectric constants into the dielectrically sensitive region. Representative simulation results are shown below. Figure 4 As shown.

[0042] Depend on Figure 4 It can be seen that both permeability and dielectric constant are strongly correlated with the resonant frequency. By performing curve fitting on the data, the electromagnetic parameters of the magnetofluid sample can be quantitatively determined.

[0043] The above description is merely an example and illustration of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described, or use similar methods to replace them, as long as they do not deviate from the invention or exceed the scope defined in the claims, all of which should fall within the protection scope of the present invention.

Claims

1. A sensor for characterizing electromagnetic parameters of a magnetohydrodynamic fluid, characterized in that, include: A dielectric substrate having a hollowed-out cavity for accommodating a magnetofluid sample to be tested; A grounding plane is located on the dielectric substrate; CSRR cells are etched on the ground plane; Multiple magnetic cavity pin structures are used to isolate the electric and magnetic field regions generated by the CSRR unit; The hollow cavity, CSRR unit, and magnetic cavity pin structure work together to form a dielectric sensitive area and a magnetic sensitive area that are separated from each other on the sensor, so as to place the sample to be tested to cause electric field disturbance or magnetic field disturbance, respectively. The magnetic cavity pin structure is a 0.5mm diameter copper cylinder that penetrates the dielectric substrate from the ground plane. The magnetic cavity pin structure is arranged with a spacing of 0.8mm parallel to the complex permeability measurement area and a spacing of 0.6mm perpendicular to the complex permeability measurement area.

2. A sensor for characterizing electromagnetic parameters of a magnetohydrodynamic fluid according to claim 1, characterized in that, The dielectric sensitive region is a strong electric field region determined by simulation or experiment, used to characterize the complex dielectric constant of the sample; The magnetically sensitive region is a strong magnetic field region determined by simulation or experiment, used to characterize the complex permeability of the sample.

3. A sensor for characterizing electromagnetic parameters of a magnetohydrodynamic fluid according to claim 1, characterized in that, The resonant frequency of the sensor shifts with the change in the dielectric constant and / or permeability of the sample placed in the dielectric sensitive region and / or magnetic sensitive region.

4. A sensor for characterizing electromagnetic parameters of a magnetohydrodynamic fluid according to claim 1, characterized in that, The sensor calculates the real part of the dielectric constant and the real part of the permeability of the ferromagnetic fluid under test by measuring the resonant frequency shift before and after the sample is loaded.

5. A sensor for characterizing electromagnetic parameters of a magnetohydrodynamic fluid according to claim 1, characterized in that, The dielectric substrate is a synthetic ceramic material with a dielectric constant of 25 and a loss tangent of 0.

004.

6. A sensor for characterizing electromagnetic parameters of a magnetohydrodynamic fluid according to claim 1, characterized in that: When used as a sensor for measuring complex permittivity, the measurement frequency band is 0.65GHz-0.78GHz, and the effective measurement range is for samples with a permittivity of 1-20 and an electrical loss tangent of 0-1. When used as a complex permeability measurement sensor, the measurement frequency band is 0.7GHz-0.78GHz, and the effective measurement range is for samples with a permeability of 1-2 and a magnetic loss tangent of 0-0.

5. The complex permittivity includes the permittivity and the electrical loss tangent, and the complex permeability includes the permeability and the magnetic loss tangent.

7. A method for characterizing the magnetohydrodynamic electromagnetic parameters of a sensor for characterizing magnetohydrodynamic electromagnetic parameters according to any one of claims 1 to 6, characterized in that, Includes the following steps: Step 1: Inject the magnetic fluid sample to be tested into the hollowed-out cavity of the dielectric substrate, so that it is located in the dielectric sensitive region of the sensor; Step 2: Measure the resonant frequency of the sensor and calculate the offset Δf relative to the resonant frequency when no sample is loaded. r电 and resonance depth ΔS 21电 ; Step 3: Using the measured Δf r电 The real part of the complex permittivity of the sample under test is obtained by inversion, and then ΔS is used to obtain the real part of the complex permittivity of the sample under test. 21电 The imaginary part of the sample under test is obtained through inversion; Step 4: Inject the magnetofluid sample to be tested into the hollowed-out cavity of the dielectric substrate, so that it is located in the permeability sensitive region of the sensor; Step 5: Measure the resonant frequency of the sensor and calculate the offset Δf relative to the resonant frequency when no sample is loaded. r磁 and resonance depth ΔS 21磁 ; Step 6: Using the measured Δf r磁 The real part of the complex permeability of the sample under test is obtained by inversion, and then obtained through ΔS. 21电 The imaginary part of the sample to be tested is obtained through inversion.

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