CN115575720A - Coupling complementary type spiral resonance sensor - Google Patents

Abstract

The invention relates to a coupled complementary spiral resonance sensor. The sensor includes: a microstrip line, a dielectric substrate, and a metal ground plate stacked in sequence from top to bottom; two mutually coupled circular complementary rotating resonators are etched on the metal ground plate; the bottom of the metal ground plate placing the material sample to be tested, and the material sample to be tested is set under the two circular complementary rotating resonators; when the material sample to be tested interacts with the electric field energy to disturb the field distribution, the two described The resonant frequency of the circular complementary rotating resonator is measured simultaneously to obtain the thickness and the dielectric constant of the material sample to be tested according to the two resonant frequencies. The invention can simultaneously measure the thickness and dielectric constant of the material sample to be tested, and improves the sensitivity of the sensor.

Description

A Coupled Complementary Helical Resonant Sensor

technical field

The invention relates to the technical field of microwave sensors, in particular to a coupled complementary spiral resonance sensor.

Background technique

Accurately measuring the properties of dielectric materials has important applications in many fields, such as medicine, electronic information, aerospace, national defense, etc. The main measurement methods currently used are reflection method, transmission line method and resonant cavity method. The reflection method generally realizes the thickness and dielectric constant measurement in a wide frequency band by transmitting the phase and amplitude of the antenna echo, but this method generally has high cost and low precision; the transmission line method generally places the medium to be measured in the Inside the transmission line (such as waveguide, etc.), the thickness and dielectric constant information are obtained by measuring the transmission parameters; the resonant cavity method generally places the sample of the material to be tested inside the resonant cavity, and obtains the thickness and dielectric constant by measuring the change of the resonant frequency and quality factor. Constant information; these two methods have higher requirements for sample preparation, because it is not easy to achieve non-destructive measurement because it needs to be placed in a cavity with limited volume.

In order to solve the above problems, in recent years, with the development of metamaterial technology, subwavelength planar microwave sensors have been widely used, providing an optional method for the measurement of electromagnetic properties of dielectric materials, which cannot be measured simultaneously by common single-resonator sensors The dielectric constant and thickness of the material sample to be tested, and the sensitivity of the single resonator sensor is low.

Contents of the invention

The purpose of the present invention is to provide a coupled complementary spiral resonant sensor to solve the problem that the single resonator sensor cannot simultaneously measure the dielectric constant and thickness of the material sample to be tested and has low sensitivity.

To achieve the above object, the present invention provides the following scheme:

A coupled complementary helical resonance sensor, comprising: a microstrip line, a dielectric substrate, and a metal grounding plate stacked sequentially from top to bottom;

Two mutually coupled circular complementary rotating resonators are etched on the metal grounding plate; the material sample to be tested is placed on the bottom of the metal grounding plate, and the material sample to be tested is arranged on the two circular complementary rotating resonators. below the resonator;

When the material sample to be tested interacts with the electric field energy to disturb the field distribution, obtain the resonant frequencies of the two circular complementary rotating resonators, and simultaneously measure the two resonant frequencies to obtain the resonant frequency of the material sample to be tested thickness and dielectric constant.

Optionally, the circular complementary rotating resonator is helically formed by a metal wire.

Optionally, by changing the outer diameter of the circular complementary rotating resonator, the distance between adjacent metal lines, the width of the metal line, and the gap between the two circular complementary rotating resonators, the coupling compensation The quality factor Q value of the type spiral resonant sensor and the test frequency.

Optionally, the electric field is concentrated in the gap between the two circular complementary rotating resonators.

Optionally, the relationship between the resonance frequency measurement and the thickness and dielectric constant of the material sample to be tested is:

f _L (ε _d ,t)＝3.086-0.2836ε _d +0.0155ε _d ² +(0.2836ε _d -0.0155ε _d ² )e ^-t/0.1483

f _H (ε _d ,t)＝3.248-0.317ε _d +0.0181ε _d ² +(0.317ε _d -0.0181ε _d ² )e ^-t/0.1353

Among them, f _L is the lower frequency value of the two resonance frequencies; f _H is the higher frequency value of the two resonance frequencies; f _L (ε _d , t) is the lower frequency value of the two resonance frequencies The function of ε _d and t; f _H (ε _d , t) is the function of the higher frequency value of the two resonance frequencies about ε _d and t; ε _d is the dielectric constant of the material sample to be tested and the dielectric constant of air The difference in electric constant; t is the thickness of the material sample to be tested.

Optionally, both ends of the microstrip line are connected to SMA connectors, and during measurement, the microstrip line is connected to a vector network analyzer through the SMA connector; the vector network analyzer is used to analyze the two The thickness and the dielectric constant of the material sample to be tested are obtained by simultaneously measuring each of the resonant frequencies.

Optionally, the characteristic impedance of the microstrip line is 50 ohms.

Optionally, the material of the dielectric substrate is Teflon.

According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects: The present invention provides a coupled complementary spiral resonator sensor, which uses two circular complementary spiral resonators to couple with each other, and its electromagnetic coupling can be equivalent to mutual Capacitance and mutual inductance, which allow the sensor to have two resonant frequencies. When the sample to be tested is loaded, the two resonant frequencies change simultaneously, so that the thickness and the dielectric constant can be measured simultaneously. In addition, compared with the case of a single resonator, the resonant frequency shift of the sensor increases after adding the coupling, thereby further improving the sensitivity of the sensor.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the accompanying drawings required in the embodiments. Obviously, the accompanying drawings in the following description are only some of the present invention. Embodiments, for those of ordinary skill in the art, other drawings can also be obtained based on these drawings without any creative effort.

Fig. 1 is the schematic diagram of the side view structure of the coupled complementary spiral resonator sensor provided by the present invention;

Fig. 2 is the top view of the coupled complementary spiral resonator sensor provided by the present invention;

3 is a schematic diagram of a circular complementary spiral resonator provided by the present invention;

Fig. 4 is the equivalent circuit diagram corresponding to the circular complementary spiral resonator sensor provided by the present invention;

Fig. 5 is the transmission parameter S21 emulation diagram under the different dielectric constants that the modeling simulation of the present invention obtains;

Fig. 6 is the simulation diagram of the transmission parameter S21 under different thicknesses that the modeling and simulation of the present invention obtains;

Fig. 7 is the relationship diagram of f _L obtained by modeling simulation of the present invention and dielectric constant and thickness;

Fig. 8 is a graph showing the relationship between f _H and the dielectric constant and thickness obtained from the modeling and simulation of the present invention.

detailed description

The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some, not all, embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

The purpose of the present invention is to provide a coupled complementary spiral resonance sensor, which can simultaneously measure the thickness and dielectric constant of the material sample to be tested, and further improve the sensitivity of the sensor.

In order to make the above objects, features and advantages of the present invention more comprehensible, the present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

Fig. 1 is a schematic side view structural diagram of a coupled complementary spiral resonator sensor provided by the present invention, and Fig. 2 is a top view of a coupled complementary spiral resonator sensor provided by the present invention, as shown in Fig. 1-Fig. 2, a coupling Complementary spiral resonant sensor, including: a microstrip line 1, a dielectric substrate 2, and a metal ground plate 3 stacked in sequence from top to bottom; two mutually coupled circular complementary spiral resonators are etched on the metal ground plate 3 4; the bottom of the metal grounding plate 3 places the material sample to be tested, and the material sample to be tested is arranged under the two circular complementary spiral resonators 4; when the material sample to be tested interacts with the electric field energy When disturbing the field distribution, the resonant frequencies of the two circular complementary helical resonators 4 are obtained, and the thickness and the dielectric constant of the material sample to be tested are obtained by simultaneous measurement according to the two resonant frequencies.

In practical applications, the microstrip line 1 is set in the middle position directly above the dielectric substrate 2, and the metal ground plate 3 is set directly below the dielectric substrate 2; two circular complementary spiral resonators 4 are etched on the metal ground plate 3 center, and pass below the microstrip line 1; SMA connectors are placed at both ends of the microstrip line, and are connected to a vector network analyzer during measurement, and the vector network analyzer is used to analyze two resonant frequencies and measure simultaneously to obtain the For the thickness and dielectric constant of the material sample to be tested, the width of the microstrip line 1 in FIG. 2 is W; the thickness of the microstrip line 1 and the metal ground plate 3 is selected from the thickness commonly used in the market.

FIG. 3 is a schematic diagram of a circular complementary spiral resonator provided by the present invention. As shown in FIG. 3 , the circular complementary spiral resonator 4 is spirally formed by a metal wire.

In practical applications, the size parameters of the circular complementary spiral resonator 4 are determined through simulation optimization and considering the manufacturing accuracy. The upper and lower parts of the spiral resonator are each composed of a group of concentric semicircular metal wires. The lines connect at the left end.

By changing the outer diameter L _R of the circular complementary spiral resonator 4 , the spacing s between adjacent metal lines, the metal line width w and the gap d between two circular complementary spiral resonators 4 , Combined with the processing accuracy, adjust the quality factor Q value and test frequency of the coupled complementary spiral resonant sensor.

The invention uses a planar sensor structure to characterize the thickness of the sample to be tested. This measurement method is based on field perturbation. When the material to be tested interacts with the stored magnetic field and electric field energy to disturb the field distribution, the resonant frequency of the resonant structure will change. The circular complementary spiral resonator 4 used in the present invention can provide a stronger electric field between the gaps of the metal wires, resulting in greater sensitivity. The invention uses a vector network analyzer to measure the change value of the resonant frequency after the sensor is added to the sample to be tested, and then determines the dielectric constant and thickness of the medium to be tested.

In practical application, the electric field is concentrated in the gap between the two circular complementary spiral resonators 4 .

In practical applications, after optimization, the thickness of the dielectric substrate 2 is determined by comprehensive measurement sensitivity and manufacturing cost, and the material is Teflon. The characteristic impedance of the microstrip line 1 is 50 ohms to achieve matching.

Fig. 4 is an equivalent circuit diagram corresponding to the sensor of the present invention. When the electrical size of the resonator is sufficiently small, its electromagnetic response can be described by a lumped circuit model. C _c1 and C _c2 represent the coupling capacitance between the microstrip line 1 and the two resonators, respectively; L _r and C _r are the equivalent inductance and capacitance of the spiral resonator itself; the electrical coupling between the two resonators and The magnetic coupling is represented by mutual capacitance C _M and mutual inductance M in the equivalent circuit; P1 is the first port of the equivalent circuit; R1 is the equivalent resistance of the microstrip line; P2 is the second port of the equivalent circuit; Rr is The equivalent resistance of the resonator.

In this way, two resonance branches can generate two resonance points. As the distance between the two resonators increases, the mutual capacitance and mutual inductance will decrease. Same as the single resonator case when there is no coupling. Mutual capacitance can be equivalent to a Π-shaped circuit between two branches. When the sample to be tested is placed on the sensor, the sample to be tested will change the capacitance Cr. At this time, the derivative of the resonant frequency f to the capacitance C _r is greater than that without coupling, so the sensitivity of the sensor will be improved.

The circular complementary spiral resonator 4 that the present invention adopts can make the electric field more concentrated in the gap of the resonator compared with the commonly used CSRR (complementary split resonator). When disturbed, higher sensitivity can be obtained. In addition, compared with other shapes, the circular resonator can obtain a higher equivalent capacitance, and the value of the equivalent inductance is relatively small, thereby obtaining a higher quality factor Q value, which can make the measurement accuracy higher .

The present invention carries out modeling and simulation on the above-mentioned sensor with a certain size through the modeling and simulation of the full-wave simulation software. As shown in Figure 5, where _εr is the dielectric constant of the material sample to be tested, when the thickness of the sample to be tested is 1mm, the present invention obtains the simulation diagram of the transmission parameter S21 under different dielectric constants. When the dielectric constant remains constant, both f _L and f _H decrease with increasing thickness. When the thickness reaches 1mm, the change of resonance frequency is small. When the relative dielectric constant of the sample to be tested is large, the sensitivity to thickness measurement will also increase. In addition, when the thickness remains constant, f _L and f _H will also decrease with the increase of dielectric constant. When the thickness of the sample to be measured is larger, the sensitivity of the resonance frequency with respect to the dielectric constant is also larger. It can be obtained from it that when the thickness of the sample to be tested is 1mm, when the dielectric constant changes from 1 to 10, the offsets of the two resonance frequencies can reach 1.406GHz and 1.516GHz, and the average offset of each 1 change in the dielectric constant The frequency is 156MHz and 168MHz, and the sensitivity is high.

As shown in Fig. 6, when the sample to be tested is FR4 medium (relative permittivity 4.5), the present invention obtains simulation diagrams of transmission parameters S21 under different thicknesses. When the thickness changes from 0.1mm to 1mm, the offsets of the two resonant frequencies are 372MHz and 404MHz, and the average offsets caused by each 0.1mm thickness are 41.3MHz and 44.9MHz, and the sensitivity is high.

Fig. 7 and Fig. 8 are diagrams of relationship between two resonant frequency points with respect to permittivity and thickness in the present invention. In order to obtain the thickness and dielectric constant of the sample to be tested from the resonant frequency value, it is necessary to establish a mathematical model to find their relationship. In the present invention, the relationship between the resonance frequency and the dielectric constant of the medium to be measured can be expressed by a quadratic function, and the relationship between the resonant frequency and the thickness can be expressed by an exponential function. And when the relative permittivity of the sample to be tested is 1 or the thickness is 0, the resonant frequency should be equal to the no-load resonant frequency. Based on the data fitting, the relationship between the resonance frequency and the thickness and permittivity can be obtained as:

f _L (ε _d ,t)＝3.086-0.2836ε _d +0.0155ε _d ² +(0.2836ε _d -0.0155ε _d ² )e ^-t/0.1483

f _H (ε _d ,t)＝3.248-0.317ε _d +0.0181ε _d ² +(0.317ε _d -0.0181ε _d ² )e ^-t/0.1353

Among them, f _L is the lower frequency value of the two resonance frequencies; f _H is the higher frequency value of the two resonance frequencies; f _L (ε _d , t) is the lower frequency value of the two resonance frequencies The function of ε _d and t; f _H (ε _d , t) is the function of the higher frequency value of the two resonance frequencies about ε _d and t; it is the dielectric constant of the material sample to be tested and the dielectric constant of air The difference; t is the thickness of the material sample to be tested.

Based on the above formula, when using the present invention to measure the relative permittivity and thickness, the sample to be tested can be placed under the two spiral resonators and cover them all; through the two resonance frequency shifts of the sensor, the calculated The dielectric constant and thickness of the material sample to be tested.

The invention has the advantages of simple experimental process, low sample preparation requirements and easy testing.

Each embodiment in this specification is described in a progressive manner, each embodiment focuses on the difference from other embodiments, and the same and similar parts of each embodiment can be referred to each other.

In this paper, specific examples have been used to illustrate the principle and implementation of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea; meanwhile, for those of ordinary skill in the art, according to the present invention Thoughts, there will be changes in specific implementation methods and application ranges. In summary, the contents of this specification should not be construed as limiting the present invention.

Claims (8)

1. A coupled complementary spiral resonant sensor, characterized in that it comprises: a microstrip line, a dielectric substrate and a metal grounding plate stacked sequentially from top to bottom; Two mutually coupled circular complementary rotating resonators are etched on the metal grounding plate; the material sample to be tested is placed on the bottom of the metal grounding plate, and the material sample to be tested is arranged on the two circular complementary rotating resonators. below the resonator; When the material sample to be tested interacts with the electric field energy to disturb the field distribution, obtain the resonant frequencies of the two circular complementary rotating resonators, and simultaneously measure the two resonant frequencies to obtain the resonant frequency of the material sample to be tested thickness and dielectric constant. 2 . The coupled complementary spiral resonant sensor according to claim 1 , wherein the circular complementary rotating resonator is helically formed by a metal wire. 3. The coupled complementary spiral resonant sensor according to claim 2, characterized in that, by changing the outer diameter of the circular complementary rotating resonator, the spacing between adjacent metal wires, the metal wire width and two The gap between the circular complementary rotating resonators adjusts the quality factor Q value and test frequency of the coupled complementary spiral resonant sensor. 4. The coupled complementary spiral resonant sensor according to claim 2, wherein the electric field is concentrated in the gap between the two circular complementary rotating resonators. 5. coupling complementary type spiral resonance sensor according to claim 1, is characterized in that, the relational expression of described resonant frequency measurement and the thickness of described material sample to be measured and dielectric constant is: f _L (ε _d ,t)＝3.086-0.2836ε _d +0.0155ε _d ² +(0.2836ε _d -0.0155ε _d ² )e ^-t/0.1483 f _H (ε _d ,t)＝3.248-0.317ε _d +0.0181ε _d ² +(0.317ε _d -0.0181ε _d ² )e ^-t/0.1353 Among them, f _L is the lower frequency value of the two resonance frequencies; f _H is the higher frequency value of the two resonance frequencies; f _L (ε _d , t) is the lower frequency value of the two resonance frequencies The function of δ _d and t; f _H (ε _d , t) is the function of the higher frequency value of the two resonance frequencies about ε _d and t; it is the dielectric constant of the material sample to be tested and the dielectric constant of air The difference; t is the thickness of the material sample to be tested. 6. coupling complementary type spiral resonant sensor according to claim 1, is characterized in that, the two ends of described microstrip line connect SMA connector, when measuring, described microstrip line passes through described SMA connector and vector The network analyzer is connected; the vector network analyzer is used to analyze the two resonant frequencies and measure simultaneously to obtain the thickness and dielectric constant of the material sample to be tested. 7. The coupled complementary spiral resonance sensor according to claim 1, wherein the characteristic impedance of the microstrip line is 50 ohms. 8. The coupled complementary spiral resonance sensor according to claim 1, wherein the material of the dielectric substrate is Teflon.

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