Planar microwave medium sensor based on SIW excitation complementary split-ring resonator

Abstract

The invention discloses a planar microwave dielectric sensor based on SIW (substrate integrated waveguide) excitation complementary split-ring resonators, which is a dual-port device and comprises a three-layer structure, namely a top layer, a middle layer and a bottom layer, the middle layer is a dielectric substrate; the bottom layer is a grounding metal plate; the antenna is characterized in that the top layer comprises a 50-ohm microstrip line, an input trapezoidal microstrip impedance transformer, an output trapezoidal microstrip impedance transformer, a substrate integrated waveguide, an upper row of through holes, a lower row of through holes and two CSRR structures; the two CSRR structures are composed of two complementary rectangular ring resonators, and each complementary rectangular ring resonator comprises an outer ring and an inner ring nested in the outer ring; the outer ring and the inner ring are each provided with an opening, and the two openings are opposite in direction. Miniaturization and planarization of the sensor can be realized, the interference resistance of the sensor to the environment is effectively improved by utilizing a complementary opening resonance structure, and the detection precision is improved.

Description

Technical Field

[0001] The present invention relates to the field of microwave measurement technology, and in particular to a planar microwave dielectric sensor based on SIW excitation complementary split resonant rings. Background Art

[0002] With the rapid development of microwave technology in fields such as biology, medicine, chemistry, military affairs, and agricultural production and life, various types of radio frequency microwave devices have been gradually developed and applied. Among them, the research on microwave sensors for measuring the dielectric constant of dielectric materials has attracted widespread attention. Numerous methods are used to measure dielectric constants, mainly divided into resonant and non-resonant methods. Non-resonant methods, such as the free-space method and the transmission line method, determine the dielectric constant of a sample by measuring its effect on the reflection coefficient or transmission coefficient of electromagnetic waves. Resonant methods, such as the cavity perturbation method, utilize the changes in the resonant frequency and quality factor of a resonant rectangular waveguide before and after the sample is placed in the cavity to accurately derive the sample's electromagnetic parameters. This method not only provides accurate dielectric constant measurements but also allows for further analysis of the material's loss characteristics. Compared to non-resonant methods, the cavity perturbation method achieves high test accuracy and is highly resistant to interference, making it the most accurate method for measuring dielectric materials to date.

[0003] At present, with the development demand for integration and miniaturization of microwave circuits, traditional cavity perturbation microwave sensors are difficult to integrate with modern miniaturized circuits because their resonant cavities are usually large in size; their performance is easily affected by environmental factors such as temperature and humidity, resulting in low test sensitivity. At the same time, a large sample amount is required to obtain obvious resonance changes, which will cause contamination and waste of the tested products; therefore, their wide application is greatly limited.

[0004] In order to avoid the large size of sensors, difficulty in integration, susceptibility to environmental factors, low sensitivity, and large sample consumption, technical personnel in this field have been seeking a miniaturized, highly sensitive, and low-loss microwave dielectric constant measurement method so that it can be integrated with modern miniaturized circuits, improve test accuracy and anti-interference capabilities, and meet the needs of the integration and miniaturization development of microwave circuits. Summary of the Invention

[0005] The purpose of the present invention is to provide a planar microwave dielectric sensor based on SIW excitation complementary open resonant ring to achieve miniaturization and planarization of the sensor, and to utilize the complementary open resonant structure to effectively improve its anti-interference ability to the environment and improve its detection accuracy.

[0006] To achieve the above objectives, the present invention proposes a planar microwave dielectric sensor based on a SIW-excited complementary split ring resonator. The sensor is a dual-port device comprising a three-layer structure: a top layer, a middle layer, and a bottom layer. The middle layer is a dielectric substrate; the bottom layer is a grounded metal plate. The top layer comprises a 50-ohm microstrip line, an input trapezoidal microstrip impedance transformer, an output trapezoidal microstrip impedance transformer, a substrate-integrated waveguide, an upper row of through-holes, a lower row of through-holes, and two CSRR structures.

[0007] The 50-ohm microstrip line has an input port and an output port, and the input port and the output port are used to connect to the SMA connector, and the SMA connector is connected to the vector network analyzer;

[0008] The input end of the 50-ohm microstrip line is connected to the narrower end of the input trapezoidal microstrip impedance transformer, the wider end of the input trapezoidal microstrip impedance transformer is connected to one end of the substrate integrated waveguide, the other end of the substrate integrated waveguide is connected to the wider end of the output trapezoidal microstrip impedance transformer, and the narrower end of the output trapezoidal microstrip impedance transformer is connected to the output end of the 50-ohm microstrip line;

[0009] The upper and lower ends of the substrate integrated waveguide are respectively provided with an upper row of through holes and a lower row of through holes; two CSRR structures that are mirror-symmetrical and arranged longitudinally are etched at the center of the substrate integrated waveguide;

[0010] The upper row of through holes and the lower row of through holes are both composed of a row of multiple through holes distributed periodically;

[0011] The two CSRR structures are composed of two complementary rectangular ring resonators, each of which includes an outer ring and an inner ring nested inside the outer ring; each of the outer ring and the inner ring has an opening, and the two openings face in opposite directions.

[0012] Furthermore, the straight line where the centers of the two complementary rectangular ring resonators are located is arranged perpendicular to the central axis of the substrate integrated waveguide.

[0013] Furthermore, the side length of the outer rectangular ring of the complementary rectangular ring resonator is 6.0-6.5 mm, the distance between the inner and outer rings is 0.3-0.5 mm, and the distance between the two complementary rectangular ring resonators is 0.4-0.8 mm.

[0014] Furthermore, the line width of the outer rectangular ring and the inner rectangular ring of the complementary rectangular ring resonator are the same.

[0015] Furthermore, the width of the 50-ohm microstrip line is the same as the width of the narrower ends of the input trapezoidal microstrip impedance transformer and the output trapezoidal microstrip impedance transformer.

[0016] Furthermore, the diameter of the upper row of through holes and the lower row of through holes at the upper and lower ends of the substrate integrated waveguide is 1-3 mm, the distance between adjacent through holes is 0.6-2.4 mm, the inner wall is a metal layer, and the upper row of through holes and the lower row of through holes at the upper and lower ends of the substrate integrated waveguide are equivalent to the two side walls of the substrate integrated waveguide, which limits the electromagnetic field to propagate in the SIW.

[0017] Furthermore, the dielectric substrate is FR4, which has a relative dielectric constant of 4.4, a loss tangent of 0.02, and a thickness of 1.6 mm.

[0018] The two CSRR structures form a parallel resonant circuit, and the resonant frequency is related to the equivalent inductance and equivalent capacitance of the parallel resonant circuit, and the expression is:

[0019]

[0020] When the sample under test completely covers the two CSRR structures, the overall resonant frequency of the resonant circuit changes. Its resonant frequency is correlated with the capacitance of the sample under test, as expressed by:

[0021]

[0022] Among them, L r Represents the equivalent inductance in the resonant circuit, C r Represents the equivalent capacitance in the resonant circuit, C MUT Indicates the equivalent capacitance of the sample to be tested.

[0023] Furthermore, the equivalent capacitance C of the sample to be tested MUT , as described in the following formula:

[0024]

[0025] Among them, ε0 represents the dielectric constant in vacuum, ε r represents the relative dielectric constant of the sample to be tested, A represents the effective cross-sectional area of ​​the sample to be tested parallel to the CSRR, and d represents the thickness of the sample to be tested.

[0026] Another object of the present invention is to provide a method for detecting the relative dielectric constant of a sample using the above-mentioned sensor, the specific steps of which are:

[0027] Turn on the vector network analyzer and perform pre-measurement calibration using the SOLT calibration method.

[0028] Tightly connect two coaxial cables of a vector network analyzer to the input and output ports of the 50-ohm microstrip line;

[0029] Record the resonant frequency f at no load at this time r0 ;

[0030] Cover the sample to be tested tightly on the surface of the sensing area formed by the two CSRR structures and record the resonant frequency f at this time. rm ;

[0031] Calculate the relative frequency offset X, the expression is:

[0032] X=|f rm -f r0 | / f r0

[0033] Among them, f rm Indicates the resonant frequency when the measurement sample is loaded, f r0 Indicates the resonant frequency when no load;

[0034] Substitute the calculated relative frequency offset into the formula to calculate the relative dielectric constant of the sample to be tested at this time. The expression is:

[0035] ε r =1.0073+17.342X-2.3891X 2 +112.39X 3

[0036] Among them, ε r Indicates the relative dielectric constant of the sample to be tested.

[0037] The present invention has the following beneficial effects:

[0038] (1) The present invention uses a substrate-integrated waveguide to excite two mirror-symmetrical CSRR structures to form a parallel resonant circuit. The CSRR structure is highly sensitive to changes in the surrounding dielectric environment. The introduction of the sample to be tested will significantly change the equivalent capacitance of the resonant circuit, thereby causing a significant shift in the resonant frequency. By establishing a clear mathematical relationship between the resonant frequency shift and the relative dielectric constant of the sample to be tested, the equivalent capacitance of the sample to be tested is incorporated into the calculation formula of the resonant frequency, and accurate coefficients are obtained by fitting experimental data, thereby ensuring the accuracy of the dielectric constant inversion calculation.

[0039] (2) The present invention adopts a planar microwave circuit structure, in which all components are located on the same plane of the dielectric substrate, resulting in a compact structure. This planar structure is easy to integrate with other microwave circuits to realize a miniaturized and integrated sensing system; the main components include a 50-ohm microstrip line, an input trapezoidal microstrip impedance transformer, an output trapezoidal microstrip impedance transformer, a substrate integrated waveguide and a CSRR structure, etc., which can be manufactured through a standard printed circuit board process, which is conducive to large-scale production and reduces manufacturing costs and difficulty. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1A schematic diagram of the three-dimensional structure of the planar microwave dielectric sensor based on SIW excitation complementary split resonant rings of the present invention is shown.

[0041] Figure 2 A schematic diagram showing the three-dimensional structure of the planar microwave dielectric sensor based on SIW excitation complementary split resonant rings of the present invention, in which a sample to be tested is placed in a sensing area.

[0042] Figure 3 A schematic diagram of the resonance structure of the planar microwave dielectric sensor based on the SIW excitation complementary split resonant ring of the present invention is shown.

[0043] Figure 4 A schematic diagram showing the dimensions of a planar microwave dielectric sensor based on a SIW-excited complementary split resonant ring according to the present invention is shown.

[0044] Figure 5 The transmission coefficient distribution diagram of the planar microwave dielectric sensor based on SIW excitation complementary split resonant ring of the present invention is shown when no sample to be tested is loaded.

[0045] Figure 6 The relationship between the relative dielectric constant and the resonant frequency of the planar microwave dielectric sensor based on SIW excitation complementary split resonant ring of the present invention is shown.

[0046] Figure 7 The relationship diagram between the resonant relative frequency deviation and the relative dielectric constant of the planar microwave dielectric sensor based on SIW excitation complementary split resonant ring of the present invention is shown.

[0047] Among them, there are a 50-ohm microstrip line 1; an input trapezoidal microstrip impedance transformer 2; an output trapezoidal microstrip impedance transformer 3; a substrate integrated waveguide 4; an upper row of through holes 5; a lower row of through holes 6; a CSRR structure 7; and a sample to be tested 8. DETAILED DESCRIPTION

[0048] Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

[0049] A planar microwave dielectric sensor based on SIW excitation complementary split resonant rings is disclosed. The sensor is a dual-port device comprising a three-layer structure, namely a top layer, a middle layer and a bottom layer.

[0050] like Figure 1-7As shown, the top layer includes a 50-ohm microstrip line 1, an input trapezoidal microstrip impedance transformer 2, an output trapezoidal microstrip impedance transformer 3, a substrate integrated waveguide 4, an upper row of through holes 5, a lower row of through holes 6, and two CSRR structures 7;

[0051] The 50-ohm microstrip line 1 has an input port and an output port, and the input port and the output port are used to connect to an SMA connector, and the SMA connector is connected to a vector network analyzer;

[0052] The input end of the 50-ohm microstrip line 1 is connected to the narrower end of the input trapezoidal microstrip impedance converter 2, the wider end of the input trapezoidal microstrip impedance converter 2 is connected to one end of the substrate integrated waveguide, the other end of the substrate integrated waveguide 4 is connected to the wider end of the output trapezoidal microstrip impedance converter 3, and the narrower end of the output trapezoidal microstrip impedance converter 3 is connected to the output end of the 50-ohm microstrip line 1;

[0053] The upper and lower ends of the substrate integrated waveguide 4 are respectively provided with an upper row of through holes 5 and a lower row of through holes 6; two CSRR structures 7 are etched at the center of the substrate integrated waveguide 4, which are mirror-symmetrical and arranged longitudinally;

[0054] The upper row of through holes 5 and the lower row of through holes 6 are both composed of a row of multiple through holes that are periodically distributed.

[0055] The middle layer is a dielectric substrate;

[0056] The bottom layer is a grounded metal plate.

[0057] The straight line where the centers of the two complementary rectangular ring resonators are located is perpendicular to the central axis of the substrate integrated waveguide.

[0058] The line width of the outer rectangular ring of the complementary rectangular ring resonator is the same as that of the inner rectangular ring.

[0059] The width of the 50-ohm microstrip line 1 is the same as the width of the narrower ends of the input trapezoidal microstrip impedance transformer 2 and the output trapezoidal microstrip impedance transformer 3 .

[0060] The diameter of the upper row of through holes 5 and the lower row of through holes 6 at the upper and lower ends of the substrate integrated waveguide 4 is 1-3 mm, the distance between adjacent through holes is 0.6-2.4 mm, and the inner wall is a metal layer. The upper row of through holes 5 and the lower row of through holes 6 at the upper and lower ends of the substrate integrated waveguide 4 are equivalent to the two side walls of the substrate integrated waveguide, which limits the electromagnetic field to propagate in the SIW.

[0061] The size of the overall microwave sensor is W X =45mm, L X =95mm;

[0062] The size of the substrate integrated waveguide 4 is W SIW =37mm, L SIW =49mm;

[0063] The width of the 50 ohm microstrip line 1 is W i =2.8-3.2mm;

[0064] The width of the wider end of the input trapezoidal microstrip impedance transformer 2 is W t =10-11mm, the length of the input trapezoidal microstrip impedance transformer 2 is L t =10-16mm;

[0065] The width of the wider end of the output trapezoidal microstrip impedance transformer 3 is W t =10-11mm, the length of the output trapezoidal microstrip impedance transformer 3 is L t =10-16mm;

[0066] The two CSRR structures 7 are composed of two complementary rectangular ring resonators, each of which includes an outer ring and an inner ring nested inside the outer ring; each of the outer ring and the inner ring has an opening, and the two openings face in opposite directions;

[0067] The side length of the outer rectangular split ring of each complementary rectangular ring resonator is a = b = 6.0-6.5 mm, the spacing between the inner and outer rings is g = 0.3-0.5 mm, the line width is a1 = a2 = 0.3-0.5 mm, and the width of the opening gap is f = 0.3-0.4 mm;

[0068] The spacing between the two complementary rectangular ring resonators is t = 0.4-0.8 mm;

[0069] The thickness of the dielectric substrate of the sensor is h = 1.6 mm;

[0070] The dielectric substrate is made of FR4 material, which has a relative dielectric constant of 4.4 and a loss tangent of 0.02;

[0071] The diameter of each through hole is d = 1-3 mm;

[0072] The distance between each two through holes is p=0.6-2.4 mm.

[0073] In the top layer structure, a 50-ohm microstrip line 1 is first connected to an input trapezoidal microstrip impedance transformer 2, which is then connected to a substrate-integrated waveguide 4. The substrate-integrated waveguide 4 is then connected to an output trapezoidal microstrip impedance transformer 3, which is then connected to the 50-ohm microstrip line 1. Two mirror-symmetrical, longitudinally arranged CSRR structures 7 are etched at the center of the substrate-integrated waveguide 4. These two CSRR structures 7 form a sensing region for measuring information such as the relative dielectric constant of the sample under test.

[0074] The performance of the microwave dielectric sensor of the present invention was simulated in simulation software, and the specific values ​​are as follows:

[0075] The width of the 50-ohm microstrip line 1 is 3 mm;

[0076] The width of the wider end of the input trapezoidal microstrip impedance transformer 2 is 10.7 mm, and the length of the input trapezoidal microstrip impedance transformer 2 is 15 mm;

[0077] The width of the wider end of the output trapezoidal microstrip impedance transformer 3 is 10.7 mm, and the length of the output trapezoidal microstrip impedance transformer 3 is 15 mm;

[0078] The side length of the outer rectangular split ring of each complementary rectangular ring resonator is 6.4 mm, the spacing between the inner and outer rings is 0.4 mm, the line width is 0.4 mm, and the width of the opening gap is 0.4 mm;

[0079] The spacing between the two complementary rectangular ring resonators is 0.6 mm;

[0080] The thickness of the dielectric substrate of this sensor is 1.6 mm;

[0081] The diameter of each through hole is 1 mm;

[0082] The distance between each two through holes is 0.8mm;

[0083] The substrate integrated waveguide 4 has a width of 37 mm and a length of 49 mm;

[0084] The overall microwave sensor has a width of 45 mm and a length of 95 mm.

[0085] The two CSRR structures 7 form a parallel resonant circuit, and its resonant frequency is related to the equivalent inductance and equivalent capacitance of the parallel resonant circuit, and the expression is:

[0086]

[0087] When the sample 8 under test completely covers the two CSRR structures 7, the overall resonant frequency of the resonant circuit changes. The resonant frequency is correlated with the capacitance of the sample under test, as expressed by:

[0088]

[0089] Among them, L r Represents the equivalent inductance in the resonant circuit, C r Represents the equivalent capacitance in the resonant circuit, C MUT Indicates the equivalent capacitance of the sample to be tested.

[0090] The equivalent capacitance C of the sample 8 to be tested MUT , as described in the following formula:

[0091]

[0092] Among them, ε0 represents the dielectric constant in vacuum, ε r represents the relative dielectric constant of the sample to be tested, A represents the effective cross-sectional area of ​​the sample to be tested parallel to the CSRR, and d represents the thickness of the sample to be tested.

[0093] The method for detecting the relative dielectric constant of a sample to be tested using the above sensor comprises the following specific steps:

[0094] Turn on the vector network analyzer and perform pre-measurement calibration using the SOLT calibration method.

[0095] Tightly connect the two coaxial cables of the vector network analyzer to the input and output ports of the 50-ohm microstrip line 1;

[0096] Record the resonant frequency f at no load at this time r0 ;

[0097] Cover the sample 8 to be tested tightly on the surface of the sensing area formed by the two CSRR structures 7, and record the resonant frequency f at this time. rm ;

[0098] Calculate the relative frequency offset X, the expression is:

[0099] X=|f rm -f r0 | / f r0

[0100] Among them, f rm Indicates the resonant frequency when the measurement sample is loaded, f r0 Indicates the resonant frequency when no load;

[0101] Substitute the calculated relative frequency offset into the formula to calculate the relative dielectric constant of the sample to be tested at this time. The expression is:

[0102] ε r =1.0073+17.342X-2.3891X 2 +112.39X 3

[0103] Among them, ε r Indicates the relative dielectric constant of the sample to be tested.

[0104] By combining the measured resonant frequency and the fitted polynomial, the relative dielectric constant of the sample to be measured can be calculated. The offset relative to the no-load resonant frequency reaches 865MHz, and the sensitivity is 86.5MHz, which realizes the measurement of the relative dielectric constant of the sample to be measured. It has high sensitivity and will play an important role in the measurement field.

[0105] No matter how detailed the above description is, there are many ways to implement the present invention. The description is only a few specific examples of the present invention. Any equivalent changes or modifications made based on the spirit of the present invention should be included in the scope of protection of the present invention.

[0106] The above detailed description of the embodiment of the present invention is not intended to be exhaustive or to limit the present invention to the above explicit form. While the above specific embodiments and embodiments of the present invention are described for illustrative purposes, those skilled in the art will recognize that various equivalent modifications may be made within the scope of the present invention.

[0107] While the above description describes specific embodiments of the present invention and describes the best mode contemplated, no matter how detailed the above description appears, the present invention can be implemented in many ways. The details of the above circuit structure and its control method can be varied considerably in its implementation details, while still being encompassed by the invention disclosed herein.

[0108] As mentioned above, it should be noted that the use of a specific term in describing certain features or aspects of the present invention should not be construed to limit the specific features, characteristics, or aspects of the present invention to which the term is applied. In short, the terms used in the appended claims should not be construed to limit the invention to the specific embodiments disclosed in the specification unless the above detailed description explicitly defines such terms. Therefore, the actual scope of the present invention encompasses not only the disclosed embodiments, but also all equivalent embodiments of the present invention as can be practiced or implemented under the claims.

[0109] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A planar microwave dielectric sensor based on SIW excitation complementary open resonant ring, the sensor is a dual-port device, including a three-layer structure, namely a top layer, a middle layer and a bottom layer; the middle layer is a dielectric substrate; the bottom layer is a grounded metal plate; the characteristics are: The top layer comprises a 50-ohm microstrip line (1), an input trapezoidal microstrip impedance transformer (2), an output trapezoidal microstrip impedance transformer (3), a substrate integrated waveguide (4), an upper row of through holes (5), a lower row of through holes (6) and two CSRR structures (7); The 50-ohm microstrip line (1) has an input port and an output port, and the input port and the output port are used to connect to the SMA connector, and the SMA connector is connected to the vector network analyzer; The input end of the 50-ohm microstrip line (1) is connected to the narrower end of the input trapezoidal microstrip impedance transformer (2), the wider end of the input trapezoidal microstrip impedance transformer (2) is connected to one end of the substrate integrated waveguide, the other end of the substrate integrated waveguide (4) is connected to the wider end of the output trapezoidal microstrip impedance transformer (3), and the narrower end of the output trapezoidal microstrip impedance transformer (3) is connected to the output end of the 50-ohm microstrip line (1); The upper and lower ends of the substrate integrated waveguide (4) are respectively provided with an upper row of through holes (5) and a lower row of through holes (6); two CSRR structures (7) that are mirror-symmetrical and arranged longitudinally are etched at the center of the substrate integrated waveguide (4); The upper row of through holes (5) and the lower row of through holes (6) are both composed of a row of multiple through holes that are periodically distributed; The two CSRR structures (7) are composed of two complementary rectangular ring resonators, which include an outer ring and an inner ring nested inside the outer ring; the outer ring and the inner ring are each provided with an opening, and the two openings are oriented in opposite directions.

2. The planar microwave dielectric sensor based on SIW excitation complementary open resonant ring according to claim 1 is characterized in that: The straight line where the centers of the two complementary rectangular ring resonators are located is arranged perpendicular to the central axis of the substrate integrated waveguide.

3. The planar microwave dielectric sensor based on SIW excitation complementary open resonant ring according to claim 2 is characterized in that: The side length of the outer rectangular ring of the complementary rectangular ring resonator is 6.0-6.5 mm, the distance between the inner and outer rings is 0.3-0.5 mm, and the distance between the two complementary rectangular ring resonators is 0.4-0.8 mm.

4. The planar microwave dielectric sensor based on SIW excitation complementary open resonant ring according to claim 3 is characterized in that: The line width of the outer rectangular ring and the inner rectangular ring of the complementary rectangular ring resonator are the same.

5. The planar microwave dielectric sensor based on SIW excitation complementary open ring resonator according to claim 1, characterized in that: The width of the 50-ohm microstrip line (1) is the same as the width of the narrower ends of the input trapezoidal microstrip impedance transformer (2) and the output trapezoidal microstrip impedance transformer (3).

6. The planar microwave dielectric sensor based on SIW excitation complementary open ring resonator according to claim 1, characterized in that: The through hole diameters of the upper row of through holes (5) and the lower row of through holes (6) at the upper and lower ends of the substrate integrated waveguide (4) are 1-3 mm, the distance between adjacent through holes is 0.6-2.4 mm, the inner wall is a metal layer, and the upper row of through holes (5) and the lower row of through holes (6) at the upper and lower ends of the substrate integrated waveguide (4) are equivalent to the two side walls of the substrate integrated waveguide, limiting the electromagnetic field to propagate in the SIW.

7. The planar microwave dielectric sensor based on SIW excitation complementary open ring resonator according to claim 1, characterized in that: The dielectric substrate is FR4, with a relative dielectric constant of 4.4, a loss tangent of 0.02, and a thickness of 1.6 mm.

8. The planar microwave dielectric sensor based on SIW excitation complementary split resonant ring according to claim 1, characterized in that: The two CSRR structures (7) form a parallel resonant circuit, and the resonant frequency thereof is related to the equivalent inductance and equivalent capacitance of the parallel resonant circuit, and the expression is: When the sample under test completely covers the two CSRR structures (7), the overall resonant frequency of the resonant circuit changes, and its resonant frequency is correlated with the capacitance of the sample under test, expressed as: Among them, L r Represents the equivalent inductance in the resonant circuit, C r Represents the equivalent capacitance in the resonant circuit, C MUT Represents the equivalent capacitance of the sample to be tested.

9. The planar microwave dielectric sensor based on SIW excitation complementary split resonant ring according to claim 8, characterized in that: The equivalent capacitance C of the sample to be tested (8) MUT , as described in the following formula: Among them, ε0 represents the dielectric constant in vacuum, ε r represents the relative dielectric constant of the sample to be tested, A represents the effective cross-sectional area of ​​the sample to be tested parallel to the CSRR, and d represents the thickness of the sample to be tested.

10. A method for detecting the relative dielectric constant of a sample using the sensor according to any one of claims 1 to 9, characterized in that: The steps include: Turn on the vector network analyzer and perform calibration before measurement using the SOLT calibration method; Tightly connecting two coaxial cables of a vector network analyzer to the input and output ports of the 50-ohm microstrip line (1); Record the resonant frequency f at no load at this time r0 ; The sample to be tested (8) is tightly covered on the surface of the sensing area formed by the two CSRR structures (7), and the resonant frequency f at this time is recorded. rm ; Calculate the relative frequency offset X, the expression is: X=|f rm -f r0 | / f r0 Among them, f rm represents the resonant frequency when the measurement sample is loaded, f r0 Indicates the resonant frequency when no load; Substitute the calculated relative frequency offset into the formula to calculate the relative dielectric constant of the sample to be tested at this time. The expression is: e r =1.0073+17.342X-2.3891X 2 +112.39X 3 Among them, ε r Indicates the relative dielectric constant of the sample to be tested.

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