A microwave sensing system for non-invasive blood glucose detection

Abstract

The present invention discloses a microwave sensing system for non-invasive blood glucose detection, which relates to the technical field of blood glucose detection. The system comprises: a voltage-controlled oscillator for generating a frequency-adjustable radio frequency signal; a radio frequency amplifier for boosting the radio frequency signal power; a dual-resonance unit differential detection structure comprising a test channel and a reference channel, both of which have identical structures, including a split-ring interdigital resonator and an envelope detector; a power divider / directional coupler for distributing the output signal of the radio frequency amplifier to the test channel and the reference channel in a 1:1 ratio; the test channel for outputting a DC voltage V_test; and the reference channel for outputting a DC voltage V_ref; and a differential processing module including a subtractor for calculating a voltage difference ΔV = V_test-V_ref in real time to eliminate common-mode interference. The system does not rely on a vector network analyzer, reducing costs; effectively suppresses common-mode interference from environmental noise; and reduces system size and power consumption.

Description

Technical Field

[0001] The present invention relates to the technical field of blood sugar detection, and in particular to a microwave sensing system for non-invasive blood sugar detection. Background Art

[0002] Currently, most diabetics use blood glucose test strips and blood glucose meters to measure their blood sugar levels by pricking their fingers. This requires patients to endure pain and the risk of infection daily to monitor their blood glucose levels. Electrochemical methods, often the primary method used in commercial blood glucose monitoring, utilize the catalytic reaction of glucose oxidase for detection. While they are popular for their high accuracy and stability, they still require blood sampling and are invasive.

[0003] Several non-invasive blood glucose monitoring technologies have emerged, primarily focusing on the following methods: a. Infrared spectroscopy: This method measures glucose concentration by analyzing the absorption characteristics of infrared light in glucose molecules. However, it is significantly affected by environmental factors and suffers from limited sensitivity and accuracy. b. Microwave technology: This method combines microwave and radio frequency technologies for blood glucose monitoring, offering the advantages of non-invasiveness and rapid detection. However, microwave detection technology faces a core challenge: traditional microwave sensors rely on bulky and expensive vector network analyzers (VNAs), severely restricting portability and clinical application. CN119375256A discloses a microwave sensing system for non-invasive blood glucose monitoring. This system achieves enhanced sensitivity through a substrate-integrated waveguide (SIW) coupled with a split-ring resonator (SRR). However, it still relies on an external vector network analyzer (VNA) for frequency domain analysis and has limited anti-interference capabilities. Summary of the Invention

[0004] To address the deficiencies in the prior art, the present invention provides a microwave sensing system for non-invasive blood glucose detection, which does not rely on a vector network analyzer, reduces costs, and reduces size.

[0005] In order to achieve the purpose of the present invention, the following scheme is proposed:

[0006] A microwave sensing system for non-invasive blood glucose detection comprises a voltage-controlled oscillator, a radio frequency amplifier, a power divider / directional coupler, a dual-resonance unit differential detection structure, and a differential processing module, which are connected in sequence.

[0007] The voltage-controlled oscillator is used to generate a frequency-adjustable radio frequency signal;

[0008] RF amplifiers are used to increase RF signal power;

[0009] The dual-resonance unit differential detection structure includes a test channel and a reference channel, both of which have the same structure, including a split-ring interdigital resonator and an envelope detector connected in sequence;

[0010] The split-ring interdigital resonator includes a split-ring resonator and an interdigital structure disposed therein. The split-ring resonator is configured as a rectangular ring structure, including two transverse segments and two longitudinal segments. A notch is provided in the middle of the transverse segment. The outer sides of the two longitudinal segments are vertically connected to an input segment and an output segment, respectively. The interdigital structure includes a rectangular frame and a plurality of interdigital fingers disposed therein. The plurality of interdigital fingers are vertically connected to two opposite inner walls of the rectangular frame and are staggered. The interdigital fingers are parallel to the transverse segments.

[0011] The power splitter / directional coupler is used to distribute the output signal of the RF amplifier to the test channel and the reference channel in a 1:1 ratio;

[0012] In the test channel, the split-ring interdigital resonator is used to input the acquired solution information into the envelope detector, and the envelope detector is used to output a DC voltage V_test;

[0013] In the reference channel, the split-ring interdigital resonator is used to input the obtained interference information into the envelope detector. The interference information includes ambient temperature, ambient humidity and electromagnetic noise. The envelope detector is used to output a DC voltage V_ref.

[0014] The differential processing module includes a subtractor for calculating the voltage difference ΔV=V_test-V_ref in real time to eliminate common-mode interference.

[0015] Furthermore, the output power of the voltage controlled oscillator is 7dBm.

[0016] Furthermore, the power divider / directional coupler adopts a high-isolation Wilkinson power divider / directional coupler.

[0017] Furthermore, the length of the interdigital fingers is 5 mm, the width is 0.34 mm, the inner spacing between two adjacent interdigital fingers is 0.31 mm, the side width of the rectangular frame perpendicular to the interdigital fingers is 0.6 mm, and the side width of the rectangular frame parallel to the interdigital fingers is 0.575 mm.

[0018] Furthermore, the input section is 6 mm long and 1.5 mm wide, the horizontal section is 8 mm long and 0.5 mm wide, and the vertical section is 11 mm long and 0.6 mm wide.

[0019] Furthermore, the split-ring interdigital resonator uses Rogers RO4350 board with a size of 20mm×20mm, a thickness of 0.762mm, and a copper-clad area at the bottom.

[0020] The beneficial effects of the present invention are:

[0021] 1. The improved split-ring interdigital resonator is used to combine the split-ring resonator and the interdigital structure, which effectively reduces the sensor area and significantly enhances the electric field strength.

[0022] 2. Eliminate the existing method's dependence on vector network analyzers and greatly reduce costs.

[0023] 3. The differential structure is used to effectively suppress the common mode interference of environmental noise (temperature, humidity, electromagnetic noise), and has strong anti-interference ability and temperature drift self-compensation.

[0024] 4. System miniaturization and low power consumption: The self-contained RF link (voltage-controlled oscillator, RF amplifier, and envelope detector integrated) replaces the traditional VNA, reducing the system size and greatly reducing power consumption, adapting to the integration needs of wearable devices.

[0025] 5. Non-invasive and highly comfortable: Based on the principle of microwave sensing, it does not require blood sampling or skin puncture. The testing process is painless and has no infection risk, significantly improving patient compliance. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Shows the connection diagram of the microwave sensing system;

[0027] Figure 2 shows a schematic diagram of the split-ring interdigital resonator structure;

[0028] Figure 3 shows the electric field distribution of the split-ring interdigital resonator;

[0029] Figure 4 The figure shows the simulation and measured results of the split-ring interdigital resonator;

[0030] Figure 5 The S21 parameter diagram of different glucose solution concentrations in the frequency range of 2.35GHz~2.55GHz is shown;

[0031] Figure 6 The S21 parameter diagram of different glucose solution concentrations in the frequency range of 2.40 GHz to 2.70 GHz is shown;

[0032] Figure 7 A subtractor circuit diagram is shown;

[0033] Figure 8 shows a graph of glucose concentration versus output voltage;

[0034] Figure 9 shows a schematic diagram of another split-ring interdigital resonator structure;

[0035] Figure 10 shows another electric field distribution diagram of a split-ring interdigital resonator;

[0036] Reference numerals: split ring resonator-1, horizontal segment-11, vertical segment-12, notch-13, interdigital structure-2, rectangular frame-21, interdigital-22, input segment-31, output segment-32. DETAILED DESCRIPTION

[0037] like Figure 1 As shown, this embodiment provides a microwave sensing system for non-invasive blood glucose detection, including a voltage-controlled oscillator, a radio frequency amplifier, a power divider / directional coupler, a dual-resonance unit differential detection structure, and a differential processing module connected in sequence.

[0038] Specifically, the voltage-controlled oscillator is used to generate a frequency-adjustable radio frequency signal with an output power of 7 dBm.

[0039] Specifically, the RF amplifier is used to increase the power of the RF signal and is also used to drive the dual-resonance unit differential detection structure.

[0040] Specifically, the dual-resonance unit differential detection structure includes a test channel and a reference channel, both of which have the same structure, and both include a split-ring interdigital resonator and an envelope detector connected in sequence.

[0041] Specifically, the power divider / directional coupler uses a high-isolation Wilkinson power divider / directional coupler to distribute the output signal of the RF amplifier to the test channel and the reference channel in a 1:1 ratio.

[0042] Specifically, in the test channel, the split-ring interdigital resonator is used to input the acquired solution information into the envelope detector, which is used to output a DC voltage, V_test. In the reference channel, the split-ring interdigital resonator is used to input the acquired interference information, including ambient temperature, humidity, and electromagnetic noise, into the envelope detector, which is used to output a DC voltage, V_ref.

[0043] Specifically, the differential processing module includes a subtractor for calculating the voltage difference ΔV=V_test-V_ref in real time to eliminate common-mode interference.

[0044] More specifically, Figure 2 As shown, the split-ring interdigital resonator includes a split-ring resonator 1 and an interdigital structure 2 arranged therein. The split-ring resonator 1 includes two transverse segments 11 and two longitudinal segments 12, and forms a rectangular ring structure. A notch 13 is provided in the middle of the transverse segment 11. The outer sides of the two longitudinal segments 12 are respectively vertically connected to the input segment 31 and the output segment 32. The interdigital structure 2 includes a rectangular frame 21 and ten interdigital fingers 22 arranged therein. The ten interdigital fingers 22 are respectively vertically connected to the two opposite inner walls of the rectangular frame 21 and are staggered. The interdigital fingers 22 are parallel to the transverse segment 11.

[0045] Among them, the split-ring interdigital resonator uses Rogers RO4350 board with a size of 20mm×20mm and a thickness of 0.762mm. The bottom is a copper-clad area. The size of the split-ring interdigital resonator is reduced by 86%.

[0046] Among them, the length of the interdigital fingers 22 is 5mm, the width is 0.34mm, the inner spacing between two adjacent interdigital fingers 22 is 0.31mm, the side width of the rectangular frame 21 perpendicular to the interdigital fingers 22 is 0.6mm, the side width of the rectangular frame 21 parallel to the interdigital fingers 22 is 0.575mm, and the length of the side is 6.5mm.

[0047] Among them, the input section 31 is 6 mm long and 1.5 mm wide, the transverse section 11 is 8 mm long and 0.5 mm wide, and the longitudinal section 12 is 11 mm long and 0.6 mm wide.

[0048] like Figure 3 As shown in the figure, the maximum electric field strength of the split-ring interdigital resonator provided by this embodiment can be increased by 2.9 times. The simulation results are shown in Figure 4 shown.

[0049] like Figure 9 As shown, it is another structure of split-ring interdigital resonator, and its electric field distribution is shown in Figure 10 As shown, it can be seen that the electric field strength is not as good as that of the split-ring interdigital resonator of this embodiment.

[0050] In order to evaluate the response of the split-ring interdigital resonator to solutions with different complex dielectric constants, a vector network analyzer (VNA) was used to measure the S parameters of the split-ring interdigital resonator. The full name of the S parameter is Scatter parameter, i.e., scattering parameter. The two ports of the split-ring interdigital resonator were connected to the vector network analyzer (VNA), the solution to be tested was injected into the container, and the container was placed on the split-ring interdigital resonator. The forward transmission coefficient S21 of the split-ring interdigital resonator was measured using the vector network analyzer. The measurement results are shown in Figure 2. Figure 5 、 Figure 6 The experimental results show that the resonant frequency of the split-ring interdigital resonator increases with the increase of solution concentration.

[0051] like Figure 7As shown, the subtractor circuit includes an RF connector U2, an RF connector U3, an operational amplifier U1, a resistor R1, a resistor R2, a resistor R3, a resistor R4, a pin header H1, a pin header H2, a capacitor C1, a capacitor C2, a capacitor C3 and a capacitor C4. The models of the RF connector U2 and the RF connector U3 are both SMA-KHD9, the model of the operational amplifier U1 is OPA627, the resistance of the resistor R1 and the resistor R4 is 28kΩ, the resistance of the resistor R2 and the resistor R3 is 10kΩ, the value of the capacitor C1 and the capacitor C3 is both 10uF, the value of the capacitor C2 and the capacitor C4 is both 100nF, the output end of the RF connector U3 is connected to the input end of the resistor R3, and the output end of the resistor R3 is connected to the same end of the operational amplifier U1. The input end of the RF connector U2 is connected to the inverting input end of the operational amplifier U1, the input end of the resistor R4 is connected to the non-inverting input end of the operational amplifier U1, the output end of the resistor R4 is grounded, the output end of the operational amplifier U1 is connected to the input end of the pin header H1, the output end of the RF connector U2 is connected to the input end of the resistor R2, the output end of the resistor R2 is connected to the inverting input end of the operational amplifier U1, the input end of the resistor R1 is connected to the inverting input end of the operational amplifier U1, the output end of the resistor R1 is connected to the output end of the operational amplifier U1, the positive power supply VCC of the operational amplifier U1 is connected to the capacitor C1 and then to ground, the negative power supply VEE of the operational amplifier U1 is connected to the capacitor C3 and then to ground, the positive power supply VCC of the pin header H2 is connected to the capacitor C2 and then to ground, and the negative power supply VEE of the pin header H2 is connected to the capacitor C4 and then to ground.

[0052] The experimental group signal is input from RF connector U3, passes through resistor R3, and then inputs into operational amplifier U1. The control group signal is input from RF connector U2, passes through resistor R2, and then inputs into operational amplifier U1. Operational amplifier U1 calculates the difference between the two signals and outputs ΔV. The subtractor circuit provided in this embodiment uses a high-precision resistor network to construct a differential amplifier circuit with a gain of 2.8. Combined with the low-noise characteristics of the OPA627, it can achieve efficient common-mode rejection of V_test and V_ref.

[0053] Circuit test: Adjust the voltage controlled oscillator output signal frequency to 2.55GHz, Figure 5 and Figure 6 It can be seen that S21 increases with the increase of glucose concentration at 2.55GHz. The envelope detector of the experimental group is connected to the same-direction input terminal of the operational amplifier, and the envelope detector of the control group is connected to the reverse input terminal of the operational amplifier. The output voltage of the subtractor is measured by a voltmeter. Figure 8 As shown, x corresponds to the glucose concentration on the horizontal axis, y corresponds to the output voltage on the vertical axis, and the correlation coefficient R 2 =0.99, it can be seen that as the glucose concentration increases, the subtractor output voltage increases.

[0054] The above embodiments are only used to illustrate the technical ideas and features of the present invention and are not intended to be exclusive or limit the present invention. It should be understood by those skilled in the art that various changes or equivalent substitutions made to the present invention without departing from the scope of the present invention are within the scope of protection of the present invention.

Claims

1. A microwave sensing system for non-invasive blood glucose detection, characterized in that: It includes a voltage-controlled oscillator, a radio frequency amplifier, a power divider / directional coupler, a dual-resonance unit differential detection structure, and a differential processing module connected in sequence; The voltage-controlled oscillator is used to generate a frequency-adjustable radio frequency signal; RF amplifiers are used to increase RF signal power; The dual-resonance unit differential detection structure includes a test channel and a reference channel, both of which have the same structure, including a split-ring interdigital resonator and an envelope detector connected in sequence; The split ring interdigital resonator comprises a split ring resonator (1) and an interdigital structure (2) arranged therein. The split ring resonator (1) is configured as a rectangular ring structure, comprising two transverse sections (11) and two longitudinal sections (12). A notch (13) is provided in the middle of the transverse section (11). The outer sides of the two longitudinal sections (12) are respectively vertically connected to an input section (31) and an output section (32). The interdigital structure (2) comprises a rectangular frame (21) and a plurality of interdigital fingers (22) arranged therein. The plurality of interdigital fingers (22) are respectively vertically connected to two opposite inner walls of the rectangular frame (21) and are staggeredly distributed. The interdigital fingers (22) and the transverse sections (11) are parallel to each other. The power splitter / directional coupler is used to distribute the output signal of the RF amplifier to the test channel and the reference channel in a 1:1 ratio; In the test channel, the split-ring interdigital resonator is used to input the acquired solution information into the envelope detector, and the envelope detector is used to output a DC voltage V_test; In the reference channel, the split-ring interdigital resonator is used to input the obtained interference information into the envelope detector. The interference information includes ambient temperature, ambient humidity and electromagnetic noise. The envelope detector is used to output a DC voltage V_ref. The differential processing module includes a subtractor for calculating the voltage difference ΔV=V_test-V_ref in real time to eliminate common-mode interference.

2. The microwave sensing system for non-invasive blood glucose detection according to claim 1, characterized in that: The output power of the voltage controlled oscillator is 7dBm.

3. The microwave sensing system for non-invasive blood glucose detection according to claim 1, characterized in that: The power divider / directional coupler adopts a high isolation Wilkinson power divider / directional coupler.

4. The microwave sensing system for non-invasive blood glucose detection according to claim 1, characterized in that: The length of the interdigital fingers (22) is 5 mm, the width is 0.34 mm, the inner spacing between two adjacent interdigital fingers (22) is 0.31 mm, the side width of the rectangular frame (21) perpendicular to the interdigital fingers (22) is 0.6 mm, and the side width of the rectangular frame (21) parallel to the interdigital fingers (22) is 0.575 mm.

5. The microwave sensing system for non-invasive blood glucose detection according to claim 1, characterized in that: The input section (31) is 6 mm long and 1.5 mm wide, the transverse section (11) is 8 mm long and 0.5 mm wide, and the longitudinal section (12) is 11 mm long and 0.6 mm wide.

6. The microwave sensing system for non-invasive blood glucose detection according to claim 4, characterized in that: The split-ring interdigital resonator uses Rogers RO4350 board with a size of 20mm×20mm, a thickness of 0.762mm, and a copper-clad area at the bottom.

Images