Double-frequency CSRR blood glucose detection sensor and non-invasive blood glucose detection method thereof

Abstract

The invention belongs to the technical field of biomedical detection equipment and sensors, and provides a double-frequency CSRR sensor with high resonance depth detection sensitivity and high resonance frequency detection sensitivity and a non-invasive blood glucose detection method thereof. The invention relates to a double-frequency CSRR blood glucose detection sensor and a non-invasive blood glucose detection method thereof. The double-frequency CSRR blood glucose detection sensor comprises an open circuit device / combiner microstrip line, a substrate and a complementary split-ring resonator unit, and the open circuit device microstrip line / combiner microstrip line is etched on a copper layer at the top of the substrate; the two double-ring circular double-frequency complementary split-ring resonators CSRR units and the two single-ring circular double-frequency complementary split-ring resonators CSRR units are etched on the copper layer at the bottom of the substrate; the symmetric line of the four CSRR units is perpendicular to the axis of the open circuit device / combiner microstrip line. The sensor is used for testing blood glucose. The method is mainly applied to blood glucose monitoring equipment design and manufacturing occasions.

Description

Technical Field

[0001] The present invention belongs to the technical field of biomedical detection and sensors, and relates to a dual-frequency complementary open resonant ring (CSRR) sensor having both amplitude and frequency detection sensitivity and a non-invasive blood glucose detection method thereof. Background Art

[0002] Diabetes is a metabolic disease characterized by high blood sugar and accompanied by multiple complications. Testing blood sugar concentration can effectively help diabetics manage themselves. Currently, invasive blood sugar concentration testing methods are commonly used to test blood sugar concentration, but this method brings pain and infection risks to diabetic patients. In addition, frequent invasive blood sugar testing will lead to a decrease in diabetic patients' compliance with medical advice, a decrease in the level of self-management, and thus a worsening of the disease.

[0003] Non-invasive blood glucose testing methods overcome the shortcomings of invasive blood glucose testing methods. They do not cause pain or discomfort during blood glucose measurement, making the blood glucose testing process safer and more comfortable for diabetic patients. Non-invasive blood glucose testing methods can be divided into electrochemical methods and electromagnetic methods according to their working principles.

[0004] 1. Non-invasive blood glucose detection method based on electrochemistry. Non-invasive blood glucose detection method based on electrochemistry measures the glucose concentration of the human body through easily accessible external body fluids such as saliva, tissue fluid, tears, sweat, etc.

[0005] 2. Electromagnetic non-invasive blood glucose detection method. Electromagnetic non-invasive blood glucose detection method uses the reflection, absorption and scattering characteristics of electromagnetic waves to measure the glucose concentration in the human body. Typical detection methods include near-infrared spectroscopy, microwave detection method, impedance spectroscopy detection method, etc.

[0006] Among the above-mentioned detection methods, the electrochemical non-invasive blood glucose detection method has a certain delay time between the measured glucose concentration and the actual blood glucose concentration. The absorption peaks of other interfering substances and glucose in the near-infrared spectrum overlap in the human body, which will cause errors in the measurement results of near-infrared spectroscopy. The impedance of human tissue is affected by many factors, such as temperature, sweat, skin thickness and humidity. In addition, the relative movement between the skin and the electrode may change the measured impedance and may cause allergic reactions. Compared with other detection methods, the microwave detection method shows considerable performance and low manufacturing cost, and the microwave sensor is small in size and suitable for integration into wearable glucose sensing systems. Among microwave sensors, microwave sensors based on metamaterials have attracted widespread attention due to their high sensitivity and small electrical size. The sensor detects blood glucose concentration mainly through changes in the sensor's resonant frequency and resonant depth. Blood glucose concentration detection based on changes in resonant frequency has higher accuracy in predicting low glucose concentrations, while blood glucose concentration detection based on changes in resonant depth has higher accuracy in predicting high glucose concentrations. Summary of the invention

[0007] In order to overcome the shortcomings of the prior art, in view of the defects of the prior art and the latest needs in the industry, the present invention aims to propose a dual-frequency CSRR sensor having both high resonance depth detection sensitivity and high resonance frequency detection sensitivity and a non-invasive blood glucose detection method thereof. The dual-frequency CSRR blood glucose detection sensor comprises an opener / combiner microstrip line, a substrate, and a complementary open resonant ring unit, wherein:

[0008] (1) The opener microstrip line / combiner microstrip line is etched on the copper layer on the top of the substrate. The opener / combiner microstrip line consists of two combiner microstrip lines and two opener microstrip lines.

[0009] (2) The substrate material can be selected from FR4, Rogers RO4003, Rogers RO3003, Rogers RO4350 and Rogers RO5880.

[0010] (3) Two double-ring circular dual-frequency complementary split resonant ring CSRR units and two single-ring circular dual-frequency complementary split resonant ring CSRR units are etched on the copper layer at the bottom of the substrate, the double-ring CSRR unit is composed of two circular concentric grooves with symmetrical openings, and the single-ring CSRR unit is composed of one circular opening groove;

[0011] (4) When a microwave signal is applied to the microstrip line, if the symmetry line of the CSRR unit is perpendicular to the axis of the microstrip line, the microstrip line provides electric field excitation for the CSRR unit; if the symmetry line of the CSRR unit is parallel to the axis of the microstrip line, the microstrip line provides electric field excitation and magnetic field excitation for the CSRR unit; the symmetry lines of the four CSRR units are perpendicular to the axis of the opener / combiner microstrip line;

[0012] (5) Apply a microwave signal to the sensor's microstrip line to measure the sensor's transmission coefficient S 21 , the transmission coefficient S 21 Two transmission zeros are shown, which are named resonance mode 1 and resonance mode 2. The highest electric field strength of the sensor at resonance can be regarded as a manifestation of high resonance frequency detection sensitivity, and the sensor has a higher maximum electric field strength when it is in resonance mode 2 compared with resonance mode 1. The resonance depth of the sensor in the no-load state is regarded as a manifestation of high resonance depth detection sensitivity, and the sensor has a larger resonance depth when it is in resonance mode 1 compared with resonance mode 2. The above phenomenon indicates that the sensor has high resonance frequency detection sensitivity in the first resonance mode and high resonance depth detection sensitivity in the second resonance mode.

[0013] The characteristic impedance of the combiner microstrip line of the sensor is 50Ω, the characteristic impedance of the open circuit microstrip line of the sensor is 100Ω, and the characteristic impedance of the width microstrip line of the combiner microstrip line and the open circuit microstrip line is calculated by the following formula:

[0014]

[0015] Among them, ε e The expression is as follows:

[0016]

[0017] Among them, W Line is the width of the microstrip line, h is the thickness of the substrate, ε e is the effective dielectric constant of the microstrip line, ε r is the dielectric constant of the sensor substrate.

[0018] The sensor is equivalent to a circuit model, then: L 1 is the inductance of the combiner microstrip line above the double-loop CSRR unit; L 2 is the inductance of the open-circuit microstrip line above the single-loop CSRR unit; C 1 is the coupling capacitance between the combiner microstrip line and the dual-loop CSRR unit; C 2 is the coupling capacitance between the open circuit microstrip line and the single-loop CSRR unit; the gap capacitance, metal wire inductance and loss of the double-loop CSRR unit are represented by C C1 , LC1 and R 1 The gap capacitance, metal wire inductance and loss of a single-loop CSRR unit are represented by C C2 , L C2 and R 2 The microstrip line outside the CSRR unit has a characteristic impedance Z i and electrical length θ i (i=1,2) indicates that the two dual-loop CSRR units are far apart, so the coupling between the two dual-loop CSRR units can be ignored. The electrical distance between the two single-loop CSRR units is very close, so the mutual coupling between the two single-loop CSRR units cannot be ignored. The coupling between the two single-loop CSRR units is represented by the capacitor C m The ABCD matrix of the circuit model is as follows:

[0019]

[0020] Among them, the ABCD parameters in the matrix are as follows:

[0021]

[0022] Among them, Z 1 , Z 2 , Z 3 , Z 4 , Z 5 and Z 6 The expression is as follows:

[0023]

[0024] By setting the parallel impedance to zero, the resonant frequency of the sensor can be obtained. The parallel impedance of the sensor is shown as follows:

[0025]

[0026] Since the resistance of the sensor and the microstrip line outside the CSRR have no effect on the resonant frequency of the sensor, the resistance and the microstrip line outside the CSRR are ignored in the calculation of the resonant frequency. The resonant frequency expression of the sensor is:

[0027]

[0028] Sensor S 21 The parameters can also be obtained from the ABCD matrix. The S of the sensor 21 The parameters are as follows:

[0029]

[0030] A non-invasive blood glucose detection method is implemented using the aforementioned sensor, and the steps are as follows:

[0031] (1) Two coaxial connectors are welded on the opener / combiner microstrip line. The sensor is connected to ports 1 and 2 of the vector network analyzer through the coaxial line. The sensor transmission coefficient S is measured and recorded. 21 The resonant frequencies and resonance depths of the upper two resonant modes;

[0032] (2) Place the finger on the four CSRR units. The dual-frequency CSRR sensor is equivalent to a resonant circuit composed of capacitance, inductance and resistance. The real and imaginary parts of the relative complex dielectric constant of blood at a fixed frequency decrease with the increase of blood glucose concentration. The change of blood dielectric properties will be reflected in the resonant frequency and resonance depth of the sensor by disturbing the effective capacitance and effective resistance of the sensor.

[0033] (3) Measure the resonant frequencies and resonant depths of the two resonant modes of the dual-frequency CSRR sensor at different blood glucose concentrations, perform data fitting based on the measured data, and construct a blood glucose concentration prediction model;

[0034] (4) Place a finger on the dual-frequency CSRR sensor for non-invasive blood glucose detection and measure the transmission coefficient S of the sensor. 21 The resonance frequencies and resonance depths of the two resonance modes above are obtained; the resonance depth of resonance mode 1 and the resonance frequency of resonance mode 2 are used as features to train a multiple linear regression equation, and the equation is used to predict blood glucose concentration; the expression of the multiple linear regression equation is as follows:

[0035]

[0036] Where y is the blood glucose concentration They correspond to the resonance depth of sensor resonance mode 1, the resonance frequency of resonance mode 2, and w 0 is the constant to be fitted, is the weight corresponding to each independent variable.

[0037] The characteristics and beneficial effects of the present invention are:

[0038] (1) A dual-frequency CSRR sensor for non-invasive blood glucose detection provided by the present invention has two resonance modes, and has high resonance depth detection sensitivity and high resonance frequency detection sensitivity in resonance mode 1 and resonance mode 2, respectively. The resonance depth and resonance frequency are used to predict the blood glucose concentration, thereby improving the accuracy of blood glucose concentration measurement.

[0039] (2) The dual-frequency CSRR sensor for non-invasive blood glucose detection provided by the present invention adopts a planar design, and the sensing area size is consistent with that of a human finger, which is convenient for integration into a portable blood glucose measurement system.

[0040] (3) The present invention measures the S of the dual-frequency CSRR sensor 21 The parameters are used to predict blood glucose concentration, and the measurement algorithm is simple with little interference. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 Schematic diagram of the dual-frequency CSRR sensor structure for non-invasive blood glucose detection provided by the present invention: (a) top structure; (b) bottom structure.

[0042] Figure 2 The equivalent circuit model of the dual-frequency CSRR sensor is

[0043] Figure 3 is the S of the dual-frequency CSRR sensor under no-load condition in full-wave simulation 21 parameter

[0044] Figure 4 Electric field distribution on the surface of the dual-frequency CSRR sensor in the no-load state in full-wave simulation (a) Resonance mode 1; (b) Resonance mode 2

[0045] Figure 5 The S of the dual-frequency CSRR sensor for non-invasive blood glucose detection provided by the present invention in full-wave simulation when the blood glucose concentration changes 21 Parameters of (a) resonance mode 1; (b) resonance mode 2.

[0046] Figure 6 This is a physical picture of blood glucose detection using the dual-frequency CSRR sensor for non-invasive blood glucose detection provided by the present invention.

[0047] Figure 7 The blood glucose concentration and the resonance characteristic change of the sensor obtained by using a dual-frequency CSRR sensor for non-invasive blood glucose detection provided by the present invention to detect blood glucose. (a) Comparison between the resonance depth of resonance mode 1 and the blood glucose concentration; (b) Comparison between the resonance depth of resonance mode 2 and the blood glucose concentration; (c) Comparison between the resonance frequency of resonance mode 1 and the blood glucose concentration; (d) Comparison between the resonance frequency of resonance mode 2 and the blood glucose concentration. DETAILED DESCRIPTION

[0048] A dual-frequency CSRR sensor for non-invasive blood glucose detection includes an opener / combiner microstrip line, a substrate, and a complementary open resonant ring unit, wherein:

[0049] (1) The opener microstrip line / combiner microstrip line is etched on the copper layer on the top of the substrate. The opener / combiner microstrip line consists of two combiner microstrip lines and two open microstrip lines. The characteristic impedance of the combiner microstrip line of the sensor is 50Ω, and the characteristic impedance of the open microstrip line is 100Ω. The width of the combiner microstrip line and the open microstrip line is calculated by the following formula:

[0050]

[0051] Among them, ε e The expression is as follows:

[0052]

[0053] Among them, W Line is the width of the microstrip line, h is the thickness of the substrate, ε e is the effective dielectric constant of the microstrip line, ε r is the dielectric constant of the sensor substrate.

[0054] (2) The substrate material can be selected from FR4, Rogers RO4003, Rogers RO3003, Rogers RO4350 and Rogers RO5880.

[0055] (3) Two double-ring circular dual-frequency complementary split resonant ring CSRR units and two single-ring circular dual-frequency complementary split resonant ring CSRR units are etched on the copper layer at the bottom of the substrate, the double-ring CSRR unit is composed of two circular concentric grooves with symmetrical openings, and the single-ring CSRR unit is composed of one circular opening groove; wherein:

[0056] The sensor is equivalent to a circuit model, then: L 1 is the inductance of the combiner microstrip line above the double-loop CSRR unit; L 2 is the inductance of the open-circuit microstrip line above the single-loop CSRR unit; C 1 is the coupling capacitance between the combiner microstrip line and the dual-loop CSRR unit; C 2 is the coupling capacitance between the open circuit microstrip line and the single-loop CSRR unit; the gap capacitance, metal wire inductance and loss of the double-loop CSRR unit are represented by C C1 , L C1 and R 1 The gap capacitance, metal wire inductance and loss of a single-loop CSRR unit are represented by C C2 , L C2 and R 2 The microstrip line outside the CSRR unit has a characteristic impedance Z i and electrical length θ i (i=1,2) indicates that the two dual-loop CSRR units are far apart, so the coupling between the two dual-loop CSRR units can be ignored. The electrical distance between the two single-loop CSRR units is very close, so the mutual coupling between the two single-loop CSRR units cannot be ignored. The coupling between the two single-loop CSRR units is represented by the capacitor C mThe ABCD matrix of the circuit model is as follows:

[0057]

[0058] Among them, the ABCD parameters in the matrix are as follows:

[0059]

[0060] Among them, Z 1 , Z 2 , Z 3 , Z 4 , Z 5 and Z 6 The expression is as follows:

[0061]

[0062] By setting the parallel impedance to zero, the resonant frequency of the sensor can be obtained. The parallel impedance of the sensor is shown as follows:

[0063]

[0064] Since the resistance of the sensor and the microstrip line outside the CSRR have no effect on the resonant frequency of the sensor, the resistance and the microstrip line outside the CSRR are ignored in the calculation of the resonant frequency. The resonant frequency expression of the sensor is:

[0065]

[0066] Sensor S 21 The parameters can also be obtained from the ABCD matrix. The S of the sensor 21 The parameters are as follows:

[0067]

[0068] (4) The sensitivity of the sensor is related to the excitation method of the CSRR unit. When a microwave signal is applied to the microstrip line, if the symmetry line of the CSRR unit is perpendicular to the axis of the microstrip line, the microstrip line provides electric field excitation for the CSRR unit. If the symmetry line of the CSRR unit is parallel to the axis of the microstrip line, the microstrip line provides electric field excitation and magnetic field excitation for the CSRR unit. When the symmetry line of the CSRR unit is perpendicular to the microstrip line, the sensor has better sensitivity. Therefore, in this design, the symmetry lines of the four CSRR units are perpendicular to the axis of the opener / combiner microstrip line.

[0069] (5) Apply a microwave signal to the microstrip line of the sensor to measure the transmission coefficient of the sensor. 21The parameters show two transmission zeros, which are named resonance mode 1 and resonance mode 2. The maximum electric field strength of the sensor at resonance can be regarded as a manifestation of high resonance frequency detection sensitivity. The sensor has a higher maximum electric field strength when it is in resonance mode 2 than in resonance mode 1. The resonance depth of the sensor in the no-load state is regarded as a manifestation of high resonance depth detection sensitivity. The sensor has a larger resonance depth when it is in resonance mode 1 than in resonance mode 2. The above phenomenon indicates that the sensor has high resonance frequency detection sensitivity in the first resonance mode and high resonance depth detection sensitivity in the second resonance mode.

[0070] The dual-frequency CSRR sensor detection method for non-invasive blood glucose detection is implemented using the above-mentioned sensor, and the steps are as follows:

[0071] (1) Two coaxial connectors are welded on the opener / combiner microstrip line. The sensor is connected to ports 1 and 2 of a vector network analyzer (VNA) through the coaxial line. The sensor transmission coefficient (S 21 Parameters) The resonant frequencies and resonant depths of the two resonant modes;

[0072] (2) Place the finger on the four CSRR units. The dual-frequency CSRR sensor is equivalent to a resonant circuit composed of capacitance, inductance and resistance. The real and imaginary parts of the relative complex dielectric constant of blood at a fixed frequency decrease with the increase of blood glucose concentration. The change of blood dielectric properties will be reflected in the resonant frequency and resonance depth of the sensor by disturbing the effective capacitance and effective resistance of the sensor.

[0073] (3) Measure the resonant frequencies and resonant depths of the two resonant modes of the dual-frequency CSRR sensor at different blood glucose concentrations, perform data fitting based on the measured data, and construct a blood glucose concentration prediction model;

[0074] (4) Place the finger on the dual-frequency CSRR sensor for non-invasive blood glucose detection and measure the sensor S 21 The resonant frequencies and resonant depths of the two resonant modes are used as parameters. The resonant depth of resonant mode 1 and the resonant frequency of resonant mode 2 are used as features to train a multiple linear regression equation. The equation is used to predict blood glucose concentration. The expression of the multiple linear regression equation is as follows:

[0075]

[0076] Where y is the blood glucose concentration x s1 , x f2 They correspond to the resonance depth of sensor resonance mode 1, the resonance frequency of resonance mode 2, and w 0 is the constant to be fitted, w s1 , w f2is the weight corresponding to each independent variable.

[0077] In order to make the purpose, technical solution and advantages of the present invention clearer, the following describes the implementation of the present invention through specific examples. It should be understood that the present invention can also be implemented or applied through other different specific implementations, and is not intended to limit the present invention. A dual-frequency complementary open resonant ring (CSRR) sensor with both amplitude and frequency detection sensitivity and a specific technical solution of a non-invasive blood glucose detection method thereof are as follows:

[0078] (1) The structure of the dual-frequency CSRR sensor is as follows Figure 1 As shown in the figure, gray represents metal and white represents the etched part. FR4 is selected as the sensor substrate. The sensor substrate is 40mm long, 20mm wide and 0.8mm thick. The opener / combiner microstrip line is etched on the copper layer on the top of the substrate with a thickness of 35μm. It consists of two widths of W. C The combiner microstrip line and two width W S In this example, the width of the combiner microstrip line is 1.5 mm, and the width of the splitter microstrip line is 0.3 mm.

[0079] (2) Two double-ring CSRR units and two single-ring CSRR units are etched on the copper layer at the bottom of the substrate with a thickness of 35 μm. The horizontal distance between the two circular double-ring CSRR units is b, and the vertical distance between the two circular single-ring CSRR units is c. The circular double-ring CSRR unit consists of two circular concentric grooves with symmetrical openings with a spacing of t, and the diameter of the circular outer ring is a. 1 , the width of the opening is g, and the width of the groove between the inner and outer metals is s. The circular single-ring CSRR unit consists of a circular opening groove, and the diameter of the circular outer ring is a 2 , the width of the opening is g, and the width of the groove between the inner and outer metals is s.

[0080] (3) The equivalent circuit model of the dual-frequency CSRR sensor is as follows Figure 2 As shown in the figure, L 1 is the inductance of the combiner microstrip line above the double-loop CSRR unit; L 2 is the inductance of the open-circuit microstrip line above the single-loop CSRR unit; C 1 is the coupling capacitance between the combiner microstrip line and the dual-loop CSRR unit; C 2 is the coupling capacitance between the open circuit microstrip line and the single-loop CSRR unit; the gap capacitance, metal wire inductance and loss of the double-loop CSRR unit are represented by C C1 , L C1 and R 1 The gap capacitance, metal wire inductance and loss of a single-loop CSRR unit are represented by CC2 , L C2 and R 2 represent; The microstrip line outside the CSRR unit is represented by the characteristic impedance Z i and the electrical length θ i (i = 1, 2); The two double-ring CSRR units are far apart, so the coupling between the two double-ring CSRR units can be ignored. The electrical distance between the two single-ring CSRR units is very close, so the mutual coupling between the two single-ring CSRR units cannot be ignored. The coupling between the two single-ring CSRR units is represented by the capacitance C m . The ABCD matrix of this circuit model is as follows:

[0081]

[0082] Among them, the ABCD parameters in the matrix are as follows:

[0083]

[0084] Among them, the expressions of Z 1 , Z 2 , Z 3 , Z 4 , Z 5 and Z 6 are as follows:

[0085]

[0086] Let the parallel impedance be zero, and the resonant frequency of the sensor can be obtained. The parallel impedance of the sensor is as follows:

[0087]

[0088] Since the resistance of the sensor and the microstrip line outside the CSRR have no effect on the resonant frequency of the sensor, the resistance and the microstrip line outside the CSRR are ignored in the calculation of the resonant frequency. The expression of the resonant frequency of the sensor is:

[0089]

[0090] The S 21 parameter of the sensor can also be obtained from the ABCD matrix. The S 21 parameter of the sensor is as follows:

[0091]

[0092] (4) The S 21 parameter of the sensor in the no-load state is as Figure 3As shown in the figure, the sensor shows two transmission zeros, which are the same as the analysis results of the sensor equivalent circuit. The two transmission zeros are named resonance mode 1 and resonance mode 2. The resonance frequency and resonance depth of resonance mode 1 are 4.51 GHz and 34.3 dB respectively, and the resonance frequency and resonance depth of resonance mode 2 are 6.35 GHz and 20.1 dB respectively. Compared with resonance mode 2, resonance mode 1 has a larger resonance depth.

[0093] (5) When a microwave signal is applied to the microstrip line, the electric field generated by the microstrip line will excite the CSRR unit, and a highly concentrated annular electric field will appear around the CSRR unit. The electric field distribution on the surface of the dual-frequency complementary open resonant ring sensor during resonance is shown in the figure below: Figure 4 As shown, when the sensor is in resonance mode 1, the maximum electric field strength of the sensor is 2.45×10 4 V / m, when the sensor is in resonance mode 2, the maximum electric field strength of the sensor is 6.76×10 4 V / m, compared with resonance mode 1, resonance mode 2 has a higher maximum electric field strength.

[0094] (6) S of dual-frequency CSRR sensor in resonance mode 1 and resonance mode 2 under different blood glucose concentrations 21 Parameters such as Figure 5 As shown, S 21 The parameter curves are easily distinguished from each other. The simulation results show that the dual-frequency CSRR sensor has high resonance depth detection sensitivity and high resonance frequency detection sensitivity in resonance mode 1 and resonance mode 2, respectively. In resonance mode 1, the resonance depth detection sensitivity of the dual-frequency complementary split resonant ring sensor is 2.2×10 -6 dB / (mg / dL), the resonant frequency detection sensitivity of the dual-frequency complementary split resonant ring sensor is 4.6×10 -3 MHz / (mg / dL).

[0095] (6) Measurement systems for human experiments such as Figure 6 As shown in the figure, the measurement system consists of a vector network analyzer, a coaxial line, and a sensor. The sensor is connected to ports 1 and 2 of the VNA via a coaxial line, and the coaxial line is fixed with tape to prevent the coaxial line from moving during the measurement and causing experimental errors. An EPE foam board cut out in the shape of a finger is attached to the sensor, and the volunteer subjects place their index fingers in the gaps on the EPE foam board to reduce the measurement errors caused by finger movement. The changes in the sensor's blood glucose concentration and the sensor's resonance characteristics within 30 minutes after the volunteers ate are shown in the figure below. Figure 7 As shown in the figure, the experimental results show that the resonant depth detection sensitivity of the sensor in resonance mode 1 is 4.4×10 -3 dB / (mg / dL), the resonant frequency detection sensitivity in resonant mode 2 is 7.4×10-1 MHz / (mg / dL).

[0096] (7) The resonance depth of resonance mode 1 and the resonance frequency of resonance mode 2 of the dual-frequency CSRR sensor were used as the input of the mathematical model to establish a multivariate linear regression model to predict the blood glucose concentration of the volunteers. The prediction formula for blood glucose concentration is: Where y is the blood glucose concentration in mg / dL, and They correspond to the resonance depth of sensor resonance mode 1 and the resonance frequency of resonance mode 2, respectively. The unit is dB, The unit is GHz.

[0097] The above embodiments are only used to illustrate the technical solutions of the present invention. Those skilled in the art will easily understand that the above are only preferred embodiments of the present invention and are not limitations of the present invention. The present invention is not limited to the above examples. Any modification or equivalent replacement within the principle of the technical solution of the present invention, as long as it meets the requirements of the method of the present invention, should be included in the protection scope of the present invention.

Claims

1. A dual-frequency CSRR blood sugar detection sensor, characterized in that: The invention comprises an opener / combiner microstrip line, a substrate, and a complementary split resonant ring unit, wherein: (1) The opener microstrip line / combiner microstrip line is etched on the copper layer on the top of the substrate. The opener / combiner microstrip line consists of two combiner microstrip lines and two opener microstrip lines. (2) The material of the substrate is one of FR4, Rogers RO4003, Rogers RO3003, Rogers RO4350 and Rogers RO5880; (3) Two double-ring circular dual-frequency complementary split resonant ring CSRR units and two single-ring circular dual-frequency complementary split resonant ring CSRR units are etched on the copper layer at the bottom of the substrate, the double-ring CSRR unit is composed of two circular concentric grooves with symmetrical openings, and the single-ring CSRR unit is composed of one circular opening groove; (4) When a microwave signal is applied to the microstrip line, if the symmetry line of the CSRR unit is perpendicular to the axis of the microstrip line, the microstrip line provides electric field excitation for the CSRR unit; if the symmetry line of the CSRR unit is parallel to the axis of the microstrip line, the microstrip line provides electric field excitation and magnetic field excitation for the CSRR unit; the symmetry lines of the four CSRR units are perpendicular to the axis of the opener / combiner microstrip line; (5) Apply a microwave signal to the sensor's microstrip line to measure the sensor's transmission coefficient S 21 , the transmission coefficient S 21 Two transmission zeros are shown, and these two transmission zeros are named resonance mode 1 and resonance mode 2; the highest electric field strength of the sensor at resonance can be regarded as a manifestation of high resonance frequency detection sensitivity, and the sensor has a higher maximum electric field strength when it is in resonance mode 2 compared with resonance mode 1; the resonance depth of the sensor in the no-load state is regarded as a manifestation of high resonance depth detection sensitivity, and the sensor has a larger resonance depth when it is in resonance mode 1 compared with resonance mode 2; the above phenomenon indicates that the sensor has high resonance frequency detection sensitivity in the first resonance mode and high resonance depth detection sensitivity in the second resonance mode.

2. The dual-frequency CSRR blood sugar detection sensor as claimed in claim 1, characterized in that: The characteristic impedance of the combiner microstrip line of the sensor is 50Ω, the characteristic impedance of the open circuit microstrip line of the sensor is 100Ω, and the characteristic impedance of the width microstrip line of the combiner microstrip line and the open circuit microstrip line is calculated by the following formula: Among them, ε e The expression is as follows: Among them, W Line is the width of the microstrip line, h is the thickness of the substrate, ε e is the effective dielectric constant of the microstrip line, ε r is the dielectric constant of the sensor substrate.

3. The dual-frequency CSRR blood sugar detection sensor as claimed in claim 1, characterized in that: The sensor is equivalent to a circuit model, then: L1 is the inductance of the combiner microstrip line above the dual-loop CSRR unit; L2 is the inductance of the open circuit microstrip line above the single-loop CSRR unit; C1 is the coupling capacitance between the combiner microstrip line and the dual-loop CSRR unit; C2 is the coupling capacitance between the open circuit microstrip line and the single-loop CSRR unit; the gap capacitance, metal wire inductance and loss of the dual-loop CSRR unit are represented by C C1 , L C1 and R1; the gap capacitance, metal wire inductance and loss of the single-loop CSRR unit are represented by C C2 , L C2 and R2; the microstrip line outside the CSRR unit has a characteristic impedance Z i and electrical length θ i (i=1,2) indicates that the coupling capacitance C between two single-loop CSRR units m Indicates that the ABCD matrix of the circuit model is as follows: Among them, the ABCD parameters in the matrix are as follows: Among them, the expressions of Z1, Z2, Z3, Z4, Z5 and Z6 are as follows: Let the parallel impedance be zero and find the resonant frequency of the sensor. The parallel impedance of the sensor is as follows: Since the resistance of the sensor and the microstrip line outside the CSRR have no effect on the resonant frequency of the sensor, the resistance and the microstrip line outside the CSRR are ignored in the calculation of the resonant frequency. The resonant frequency expression of the sensor is: Sensor S 21 The parameters can also be obtained from the ABCD matrix. The S of the sensor 21 The parameters are as follows:

4. A non-invasive blood glucose detection method, characterized in that: The sensor according to claim 1 is used to implement the detection steps as follows: (1) Two coaxial connectors are welded on the microstrip line of the opener / combiner. The sensor is connected to ports 1 and 2 of the vector network analyzer through the coaxial line. The resonant frequency and resonant depth of the two resonant modes on the sensor transmission coefficient S21 are measured and recorded. (2) Place the finger on the four CSRR units. The dual-frequency CSRR sensor is equivalent to a resonant circuit composed of capacitance, inductance and resistance. The real and imaginary parts of the relative complex dielectric constant of blood at a fixed frequency decrease with the increase of blood glucose concentration. The change of blood dielectric properties will be reflected in the resonant frequency and resonance depth of the sensor by disturbing the effective capacitance and effective resistance of the sensor. (3) Measure the resonant frequencies and resonant depths of the two resonant modes of the dual-frequency CSRR sensor at different blood glucose concentrations, perform data fitting based on the measured data, and construct a blood glucose concentration prediction model; (4) Place a finger on the dual-frequency CSRR sensor for non-invasive blood glucose detection and measure the transmission coefficient S of the sensor. 21 The resonance frequencies and resonance depths of the two resonance modes above are obtained; the resonance depth of resonance mode 1 and the resonance frequency of resonance mode 2 are used as features to train a multiple linear regression equation, and the equation is used to predict blood glucose concentration; the expression of the multiple linear regression equation is as follows: y=w0+w s1 x s1 +w f2 x f2 Where y is the blood glucose concentration x s1 , x f2 They correspond to the resonance depth of sensor resonance mode 1 and the resonance frequency of resonance mode 2 respectively. w0 is the constant to be fitted, and w s1 , w f2 is the weight corresponding to each independent variable.

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