CN114594312A - Liquid complex dielectric constant sensor of mutual coupling annular gap resonance structure and measuring method - Google Patents

Abstract

The invention discloses a liquid complex dielectric constant sensor and a measurement method of a mutual coupling ring-slit resonance structure, and relates to the technical field of radio frequency and microwave engineering. The liquid complex permittivity sensor comprises a glass tube (4), a ground wire GND layer (3), a dielectric layer (2), a microstrip line layer (1), and the ground wire GND layer (3) is used to form an equivalent circuit , and measure the complex permittivity of the liquid sample by contacting the glass tube (4) where the liquid sample is located; the dielectric layer (2) is used to form an LC-like resonant cavity; the microstrip line layer (1) is used to transmit signals, And make the signal output end match the load. Simultaneous measurement of the dielectric constant and loss tangent of the liquid sample is achieved, and the measurement accuracy of the complex dielectric constant is improved.

Description

Liquid complex permittivity sensor and measurement method of mutual coupling ring-slit resonant structure

technical field

The invention relates to the technical field of radio frequency and microwave engineering, in particular to a liquid complex permittivity sensor and a measurement method with a mutually coupled annular slot resonance structure.

Background technique

The complex permittivity is one of the most important parameters of materials in RF and microwave engineering. The dielectric properties of the materials used in the substrates of microwave devices affect the response of microwave planar circuits. In order to model a complex microwave device, the complex permittivity of the materials used in the substrate of the microwave device must first be measured. Therefore, accurate determination of the complex permittivity of materials is an important task in the field of RF and microwave engineering. In addition to microwave engineering, other fields such as food, health care, agriculture, etc., also require accurate measurement of complex permittivity. The complex dielectric constant includes dielectric constant and loss tangent. Compared with solid materials, liquid materials have the characteristics of high dielectric constant, large loss tangent and difficult to fix fluidity, which makes it more difficult to measure the complex dielectric constant of liquid materials. .

In the prior art, methods for measuring the complex permittivity of liquids can be roughly divided into free space methods, transmission line methods and resonance methods. However, these methods all have shortcomings such as high requirements for liquid samples, low sensitivity, only low dielectric constant liquid materials can be measured, and loss tangent cannot be measured.

SUMMARY OF THE INVENTION

The purpose of the present invention is to solve the problems of the above-mentioned background technology, and propose a liquid complex permittivity sensor and a measurement method with a mutual coupling ring-slit resonance structure, so as to realize the simultaneous measurement of the permittivity and loss tangent of the liquid sample, and improve the measurement Measurement accuracy of complex permittivity.

The object of the present invention can be realized through the following technical solutions:

In the first aspect of the embodiment of the present invention, a liquid complex permittivity sensor with a mutually coupled ring-slit resonance structure is provided, including a glass tube 4, a ground wire GND layer 3, a dielectric layer 2, and a microstrip line layer 1. The ground wire The GND layer 3 is used to form an equivalent circuit, and by contacting the glass tube 4 where the liquid sample is located, the complex permittivity of the liquid sample is measured; the dielectric layer 2 is used to form an LC-like resonant cavity; The stripline layer 1 is used to transmit signals and match the signal output to the load.

Optionally, the ground wire GND layer 3 includes a mutual coupling ring-slit resonant structure 31 composed of 3 annular etched rings, wherein the centers of the 3 annular etched rings are coincident, and the through holes 32 with a diameter of 1.5 mm are penetrated at the center of the circles. ; The mutually coupled ring-slit resonant structure 31 is used to form a micro-variable equivalent circuit with the glass tube 4 loaded with the liquid sample in the through hole 32 .

Optionally, the ground wire GND layer 3 is a rectangular metal etched with a three-ring mutual coupling annular slot structure; wherein, the inner circle radius of the mutual coupling annular slot large ring 311 of the three-ring mutual coupling annular slot structure is 3.2mm, the outer radius is 3.65mm; the inner radius of the ring 312 in the mutual coupling annular slot of the three-ring mutual coupling annular slot structure is 2.5 mm, and the outer radius is 2.9 mm; the three-ring mutual coupling annular slot structure The inner radius of the mutual coupling ring slit 313 is 1.9mm, and the outer radius is 2.2mm.

Optionally, a slit is etched at the bottom end perpendicular to the microstrip line layer 1 of the mutual coupling ring slit macro ring 311, and the width of the slit is 0.22 mm; the ring 312 in the mutual coupling ring slit is perpendicular to the microstrip A slit is etched at the top of the strip line layer 1, and the width of the slit is 0.22 mm; the mutual coupling ring slit small ring 313 is etched with a slit at the bottom end perpendicular to the microstrip line layer 1, and the width of the slit is is 0.22mm.

Optionally, the material of the glass tube 4 is quartz glass, and the glass tube 4 is a hollow cylinder with an outer diameter of 1.5 mm, an inner diameter of 0.9 mm, and a length of 75 mm with a bottom on one side, and is used for loading the liquid sample into the sensor. Through holes 32 .

Optionally, the thickness of the ground line GND layer 3 and the microstrip line layer 1 is 0-0.02mm, and the material of the ground line GND layer 3 and the microstrip line layer 1 is any one of gold, silver and copper. , or a conductive material with comparable conductivity to any of gold, silver and copper.

Optionally, the microstrip line layer 1 is a microstrip line longitudinally passing through the middle position of the dielectric layer 2, and its size is 28 mm×1.66 mm.

Optionally, the size of the dielectric layer 2 is 28mm×20mm×0.75mm, and it floats up and down by 0.0015mm on the basis of this size, and the material of the dielectric layer 2 is RO3035 material with a dielectric constant of 3.5, and the loss The tangent value is 0.02.

Optionally, the measurement frequency band of the liquid complex permittivity sensor is between 2.75GHz-3GHz, and the effective measurement range is a liquid sample with a permittivity of 1-90 and a loss tangent value of 0-1.

Based on any of the liquid complex permittivity sensors described above, an embodiment of the present invention further provides a method for measuring liquid complex permittivity, where the liquid complex permittivity includes permittivity and loss tangent, and the method includes:

Insert the glass tube 4 containing the liquid sample into the through hole 32 of the liquid complex permittivity sensor;

Under the resonance of the 2.75GHz-3GHz frequency band, use a vector network analyzer to measure the liquid complex permittivity sensor to obtain the S21 parameter curve of the center frequency of the transmission coefficient;

Determine the resonant frequency and insertion loss of the S21 parameter curve;

The dielectric constant of the liquid sample is determined according to the resonant frequency, and the loss tangent value of the liquid sample is determined according to the insertion loss.

The liquid complex permittivity sensor based on the mutual coupling ring-slit resonance structure provided by the embodiment of the present invention can use a vector network analyzer to measure the S21 parameter curve of the center frequency of the transmission coefficient under the resonance of the 2.75GHz-3GHz frequency band, and according to the S21 parameter The resonant frequency and insertion loss of the curve determine the dielectric constant and loss tangent of the liquid sample. The liquid complex permittivity sensor provided by the embodiment of the present invention has the advantages of small volume, simple structure, low processing cost, good measurement range adaptation, etc., and can simultaneously measure the permittivity and loss tangent of the bulk sample, which improves the measurement complexity. The measurement accuracy of the dielectric constant.

Description of drawings

The present invention will be further described below in conjunction with the accompanying drawings.

1 is a three-dimensional structural diagram of a liquid complex permittivity sensor with a mutually coupled annular slot resonance structure provided in an embodiment of the present invention;

FIG. 2 is a schematic diagram of a ground wire GND layer of a liquid complex permittivity sensor with a mutually coupled annular slot resonance structure provided in an embodiment of the present invention;

3 is a schematic plan view of a mutually coupled annular slot resonance structure of a liquid complex permittivity sensor provided by an embodiment of the present invention;

4 is a flowchart of a liquid complex permittivity measurement method provided by an embodiment of the present invention;

5 is an equivalent circuit diagram of a mutually coupled annular slot resonance structure provided by an embodiment of the present invention;

6 is a schematic diagram of the S21 parameter curve of the liquid complex permittivity sensor under the frequency band resonance of the microstrip line of 2.75GHz-3GHz provided by an embodiment of the present invention;

FIG. 7 is a schematic diagram of the S21 parameter curve of a liquid complex permittivity sensor with a dielectric constant of 20 and a dielectric constant of 70 and a loss tangent value varying from 0 to 1 according to an embodiment of the present invention.

In the figure: 1. Microstrip line layer; 2. Dielectric layer; 3. Ground wire GND layer; 4. Glass tube; 31. Mutual coupling ring slot resonance structure; 32, Through hole; 312. The middle ring of the mutual coupling annular seam; 313, the small ring of the mutual coupling annular seam.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

The embodiment of the present invention provides a liquid complex permittivity sensor with a mutually coupled annular slot resonance structure. Referring to FIG. 1 , FIG. 1 is a three-dimensional structural diagram of a liquid complex permittivity sensor with a mutually coupled ring-slit resonance structure provided in an embodiment of the present invention. The liquid complex permittivity sensor includes a glass tube 4 , a ground wire GND layer 3 , a dielectric layer 2 , and a microstrip line layer 1 .

The ground wire GND layer 3 is used to form an equivalent circuit with the patch layer excitation, and is used to measure the complex permittivity of the liquid sample by contacting the glass tube 4 where the liquid sample is located; the dielectric layer 2 is used to form an LC-like resonant cavity; The microstrip line layer 1 is used to transmit signals, and the signal output terminal is matched with the load.

In one embodiment, referring to FIG. 2 , FIG. 2 is a schematic diagram of a ground wire GND layer of a liquid complex permittivity sensor with a mutual coupling ring-slit resonance structure provided in an embodiment of the present invention.

The ground line GND layer 3 includes a mutual coupling ring slit resonance structure 31 composed of three ring etchings, wherein the centers of the three ring etchings are coincident and pass through a through hole 32 with a diameter of 1.5 mm at the center of the circle; the mutual coupling ring slit resonance The structure 31 is used to form a micro-variable equivalent circuit with the glass tube 4 loaded with the liquid sample in the through hole 32 .

In one embodiment, referring to FIG. 3 , FIG. 3 is a schematic plan view of a mutual-coupled ring-slit resonance structure of a liquid complex permittivity sensor according to an embodiment of the present invention.

The ground wire GND layer 3 is a rectangular metal etched with a three-ring mutual coupling annular slot structure; wherein, the inner circle radius of the mutual coupling annular slot large ring 311 of the three-ring mutual coupling annular slot structure is 3.2mm, and the outer circle radius is 3.65mm mm; the inner circle radius of the middle ring 312 of the mutual coupling annular slot structure of the three-ring mutual coupling annular slot structure is 2.5mm, and the outer circle radius is 2.9 mm; the inner circle radius of the small ring 313 of the mutual coupling annular slot structure of the three-ring mutual coupling annular slot structure is 1.9mm, and the outer circle radius is 2.2mm.

In one embodiment, a slit is etched at the bottom end of the mutual coupling ring slit macroring 311 perpendicular to the microstrip layer 1, and the width of the slit is 0.22 mm; in the mutual coupling ring slit, the ring 312 is perpendicular to the microstrip line. The top of the layer 1 is etched with a slit with a width of 0.22mm; the mutual coupling annular slit small ring 313 is etched with a slit at the bottom end perpendicular to the microstrip layer 1 with a width of 0.22mm.

In one embodiment, the glass tube 4 is made of quartz glass, and the glass tube 4 is a hollow cylinder with an outer diameter of 1.5 mm, an inner diameter of 0.9 mm, and a length of 75 mm with a bottom and one side, and is used for loading a liquid sample into the through hole 32 of the sensor.

In one embodiment, the thickness of the ground line GND layer 3 and the microstrip line layer 1 is 0-0.02 mm, and the material of the ground line GND layer 3 and the microstrip line layer 1 is any one of gold, silver and copper, or It is a conductive material with comparable conductivity to any one of gold, silver and copper.

In one embodiment, the microstrip line layer 1 is a microstrip line longitudinally passing through the middle position of the dielectric layer 2, and its size is 28 mm×1.66 mm.

In one embodiment, the size of the dielectric layer 2 is 28mm×20mm×0.75mm, and the size is 0.0015mm up and down, the material of the dielectric layer 2 is RO3035 material with a dielectric constant of 3.5, and the loss tangent is 0.02.

In one embodiment, the measurement frequency band of the liquid complex permittivity sensor is between 2.75GHz-3GHz, and the effective measurement range is a liquid sample with a permittivity of 1-90 and a loss tangent of 0-1.

Based on the same inventive concept, the embodiments of the present invention also provide a method for measuring the complex permittivity of liquids. Referring to FIG. 4 , FIG. 4 is a flowchart of a method for measuring a liquid complex permittivity provided by an embodiment of the present invention. Liquid complex permittivity includes permittivity and loss tangent, and the method includes the following steps:

S401, insert the glass tube 4 containing the liquid sample into the through hole 32 of the liquid complex permittivity sensor.

S402, under the resonance of the 2.75GHz-3GHz frequency band, a vector network analyzer is used to measure the liquid complex permittivity sensor, and the S21 parameter curve of the center frequency of the transmission coefficient is obtained.

S403, determine the resonance frequency and insertion loss of the S21 parameter curve.

S404, the dielectric constant of the liquid sample is determined according to the resonance frequency, and the loss tangent value of the liquid sample is determined according to the insertion loss.

In an implementation manner, the liquid complex permittivity sensor may adopt dual SMA (Small AType) interfaces, and a vector network analyzer may be directly connected to the interface of the liquid complex permittivity sensor for measurement.

In an implementation manner, the mutual coupling ring-slit resonant structure 31 of the liquid complex permittivity sensor consists of a loop and a gap that divides the loop. According to the mutual coupling ring slot resonance structure 31, the equivalent circuit of the mutual coupling ring slot resonance structure 31 can be obtained.

Referring to FIG. 5 , FIG. 5 is an equivalent circuit diagram of a mutually coupled annular slot resonance structure provided by an embodiment of the present invention. Since the inductance generated by the loop current in the loop and the equivalent capacitance formed by the gap work together, the mutual coupling ring slot resonance structure 31 will generate resonance. Due to the change of the complex permittivity of the liquid sample, the equivalent capacitance corresponding to the mutually coupled ring-slit resonant structure 31 may change, while the equivalent inductance corresponding to the complementary open-loop structure is basically unchanged. Therefore, the excitation electric field of the mutually coupled ring slit resonance structure 31 can be changed by exciting the left and right complementary open-loop structures respectively by the microstrip line layer 1 .

Referring to FIG. 6, FIG. 6 is a schematic diagram of the S21 parameter curve of the liquid permittivity sensor under the excitation of the microstrip line in the frequency band of 2.75 GHz-3 GHz provided by the embodiment of the present invention.

The time domain solver of the EM simulation software is used to simulate the above-mentioned liquid complex permittivity sensor, and the transmission coefficient center frequency S21 parameter of the liquid complex permittivity sensor is calculated under the resonance of the 2.75GHz-3GHz frequency band.

It can be seen from Figure 6 that the dielectric constant of the liquid sample is related to the central resonance frequency of the S21 parameter. Therefore, by establishing the corresponding relationship between the liquid samples with different dielectric constants and the resonance frequency of the S21 parameter, the central resonance of the S21 parameter can be measured. frequency to determine the dielectric constant of the liquid sample.

Referring to FIG. 7 , FIG. 7 is a schematic diagram of the S21 parameter curve of a liquid complex permittivity sensor with a dielectric constant of 20 and a dielectric constant of 70 and a loss tangent value varying from 0 to 1 according to an embodiment of the present invention.

It can be seen from Figure 7 that when measuring multiple liquid samples with the same dielectric constant and different loss tangents, it can be observed that the change of the loss tangent will only affect the insertion loss of the S21 parameter, and will not affect the resonant frequency. . Therefore, by establishing the correspondence between liquid samples with different loss tangent values and the insertion loss of the S21 parameter curve, the loss tangent value of the liquid sample can be determined by measuring the insertion loss of the S21 parameter.

Since the accuracy of the vector network analyzer can reach 10Hz, the response-sensitive measurement accuracy of the liquid complex permittivity sensor to liquid samples with different complex permittivity can be within ±1.

An embodiment of the present invention has been described in detail above, but the content is only a preferred embodiment of the present invention, and cannot be considered to limit the scope of the present invention. All equivalent changes and improvements made according to the scope of the application of the present invention should still belong to the scope of the patent of the present invention.

Claims (10)

1. The liquid complex dielectric constant sensor of the mutual coupling circumferential seam resonance structure comprises a glass tube (4), a ground wire GND layer (3), a dielectric layer (2) and a microstrip line layer (1), and is characterized in that the ground wire GND layer (3) is used for forming an equivalent circuit and is in contact with the glass tube (4) where a liquid sample is located to measure the complex dielectric constant of the liquid sample; the dielectric layer (2) is used for forming an LC-like resonant cavity; the microstrip line layer (1) is used for transmitting signals and matching signal output ends with loads.

2. The sensor of liquid complex permittivity of a mutual coupling gap resonance structure according to claim 1, wherein said ground GND layer (3) comprises a mutual coupling gap resonance structure (31) of 3 ring etchings, wherein the centers of the 3 ring etchings coincide and penetrate a through hole (32) of 1.5mm in diameter at the center of the circle; the mutual coupling circular seam resonance structure (31) is used for forming a micro-variation equivalent circuit with a glass tube (4) loaded with the liquid sample in the through hole (32).

3. The sensor of the liquid complex permittivity of a mutual coupling gap resonance structure according to claim 2, wherein said ground GND layer (3) is a rectangular metal piece etched with a three-ring mutual coupling gap structure; wherein, the inner circle radius of the mutual coupling circular seam large ring (311) of the three-ring mutual coupling circular seam structure is 3.2mm, and the outer circle radius is 3.65 mm; the inner circle radius of a mutual coupling circular seam middle ring (312) of the three-ring mutual coupling circular seam structure is 2.5mm, and the outer circle radius is 2.9 mm; the inner circle radius of a small mutual coupling annular gap ring (313) of the three-ring mutual coupling annular gap structure is 1.9mm, and the outer circle radius is 2.2 mm.

4. A sensor of liquid complex permittivity of a mutually coupled slot-loop resonance structure according to claim 3, wherein said mutually coupled slot-loop large loop (311) is etched with a slit perpendicular to the bottom end of the microstrip line layer (1), the slit width being 0.22 mm; a slit is etched in the top end, perpendicular to the microstrip line layer (1), of the middle ring (312) of the mutual coupling circular seam, and the width of the slit is 0.22 mm; the mutual coupling annular seam small ring (313) is etched with a slit at the bottom end vertical to the microstrip line layer (1), and the width of the slit is 0.22 mm.

5. The sensor of claim 1, wherein the glass tube (4) is made of quartz glass, and the glass tube (4) is a hollow cylinder with an outer diameter of 1.5mm, an inner diameter of 0.9mm, a length of 75mm and a single bottom, and is used for loading the liquid sample into the through hole (32) of the sensor.

6. The sensor of the complex liquid dielectric constant of the mutually coupled annular gap resonance structure as claimed in claim 1, wherein the thickness of the ground GND layer (3) and the microstrip line layer (1) is 0-0.02mm, and the material of the ground GND layer (3) and the microstrip line layer (1) is any one of gold, silver and copper, or a conductive material having a conductivity equivalent to any one of gold, silver and copper.

7. The sensor of claim 6, wherein the microstrip line layer (1) is a microstrip line passing longitudinally through the middle of the dielectric layer (2) and having dimensions of 28mm x 1.66 mm.

8. The liquid complex permittivity sensor of a mutual coupling circumferential seam resonance structure according to claim 1, wherein the size of the medium layer (2) is 28mm x 20mm x 0.75mm, and the medium layer (2) floats up and down by 0.0015mm on the basis of the size, and the material of the medium layer (2) is RO3035 material with a dielectric constant of 3.5 and a loss tangent value of 0.02.

9. The sensor of claim 1, wherein the liquid complex permittivity sensor has a measurement band of 2.75GHz-3GHz, and an effective measurement range of a liquid sample having a permittivity of 1-90 and a loss tangent of 0-1.

10. The method for measuring a liquid complex permittivity of a liquid complex permittivity sensor according to any one of claims 1 to 9, wherein the liquid complex permittivity includes a permittivity and a loss tangent, the method including:

inserting a glass tube (4) filled with a liquid sample into a through hole (32) of the liquid complex dielectric constant sensor;

under the resonance of a 2.75GHz-3GHz frequency band, measuring the liquid complex dielectric constant sensor by using a vector network analyzer to obtain a transmission coefficient center frequency S21 parameter curve;

determining the resonant frequency and insertion loss of the S21 parameter curve;

and determining the dielectric constant of the liquid sample according to the resonance frequency, and determining the loss tangent value of the liquid sample according to the insertion loss.

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