Complementary Open-Screen Resonant Ring Sensor Based on Interdigitated Structure and Its Design Method

Abstract

This invention discloses a complementary open-ring resonator sensor based on an interdigital structure and its design method. The sensor is a two-port device comprising a three-layer structure: a top layer, a middle layer, and a bottom layer. The top layer includes a microstrip line with an input port and an output port, the output port being connected to an SMA connector. The middle layer is a dielectric substrate. The bottom layer includes a metal sheet and a three-ring complementary open-ring resonator (CSRR) structure. The middle region of the metal sheet is an etching region used to etch the three-ring CSRR structure, which includes an outer ring, a middle ring, and an inner ring. The outer and inner rings are two open-ring resonators of unequal width. The middle ring is a ring structure composed of interdigital capacitors (IDCs). A sample holder is fixed on the middle ring for measuring the complex dielectric constant of the liquid. Compared with existing sensors, this invention features a smaller size, lower detection error, and a sensitivity as high as 1.23%.

Description

Technical Field

[0001] This invention belongs to the field of microwave radio frequency sensing technology, and relates to a complementary open resonant ring sensor based on an interdigital structure and its design method. Background Technology

[0002] In recent years, with the rapid development of sensor technology, more and more people have begun to devote themselves to the research and development of microwave sensors. To date, microwave sensors have been widely used in many fields such as food, agriculture, and biomedicine, especially in materials science. Because microwave sensors can provide label-free detection, they eliminate the need for large amounts of reagents when characterizing the dielectric constant of liquids, significantly reducing costs. At the same time, microwave sensors have the advantages of low cost and small size compared to other similar sensors. Therefore, microwave sensors have very important application value in the field of materials sensing.

[0003] Currently, many different types of microwave sensors have been proposed to characterize binary liquids, most of which utilize a complementary open-ring resonator structure. Although the electric field of the complementary open-ring resonator structure is more concentrated compared to other resonant structures, this structure employs coupling during transmission, which affects the sensor's sensitivity. Summary of the Invention

[0004] To address the aforementioned problems, the technical solution of this invention is as follows: a complementary open-ring resonant sensor based on an interdigital structure, which employs methods such as shortening the outer ring width and using an IDC ring structure for the middle ring to increase the capacitance effect of the resonant circuit, enhance the electric field effect, and improve the sensor sensitivity.

[0005] To overcome the existing technical difficulties, the technical solution of this invention is as follows: The sensor is a dual-port device comprising a three-layer structure, namely a top layer, a middle layer, and a bottom layer. The top layer includes a microstrip line with an input port and an output port, the output port being connected to an SMA connector. The middle layer is a dielectric substrate. The bottom layer includes a metal sheet and a three-ring CSRR structure. The middle region of the metal sheet is an etching region used to etch the three-ring CSRR structure. The three-ring CSRR structure includes an outer ring, a middle ring, and an inner ring. The outer and inner rings are two open resonant rings of unequal width. The middle ring is a ring structure with an interdigitated structure composed of IDCs. A sample holder is fixed on the middle ring to measure the complex dielectric constant of the liquid.

[0006] Preferably, the SMA connector is connected to the vector network analyzer to form a liquid detection system.

[0007] Preferably, the outer ring has a width of 0.3 mm, and the middle and inner rings have a width of 1 mm.

[0008] Preferably, the opening gap width of the outer ring is 1 mm.

[0009] Preferably, the interdigitated structure of the intermediate ring has an interdigitated finger length of 0.8 mm, a finger width of 0.2 mm, an outer interdigitated finger gap width of 0.63 mm, an inner interdigitated finger gap width of 0.45 mm, and 36 interdigitated fingers on both the outer and inner sides.

[0010] Preferably, the width of the microstrip line is 1.6 mm.

[0011] Preferably, the dielectric substrate is a Rogers 4350 series dielectric substrate with a dielectric constant of 3.66, a loss tangent of 0.004, and a thickness of 0.762 mm.

[0012] Preferably, the outer ring and inner ring, after loading the interdigitated middle ring structure, form two parallel resonant circuits. Their resonant frequencies are related to the inductance and capacitance of the resonant ring structure and the IDC structure, as expressed by:

[0013]

[0014] When a liquid sample is added to the sample holder, the overall resonant frequency of the resonant circuit changes, and its resonant frequency becomes correlated with the capacitance of the liquid sample, as expressed by:

[0015]

[0016] Among them, L C C C For the capacitance and inductance of the open-circuit resonant ring, C I For interdigitated capacitors, C is the coupling capacitance between the microstrip line and the metal sheet; C LUT This simulates the change in capacitance after the sample solution is added.

[0017] The normalized sensitivity of a sensor is defined as:

[0018]

[0019] Where Δf is the offset of the resonant frequency; Δε is the change in the dielectric constant of the liquid sample loaded in the sample holder; and f0 is the resonant frequency when the circuit is unloaded.

[0020] Preferably, the sample holder is made of acrylonitrile-butadiene-styrene, is rectangular in shape, has an inner wall width of 3 mm, and a length of 5 mm.

[0021] To achieve the above objectives, the present invention also provides a design method for a complementary open-loop resonator sensor based on an interdigital structure. The method, employing the aforementioned complementary open-loop resonator sensor based on an interdigital structure, includes the following steps:

[0022] S1, a triple complementary open-loop resonant ring structure is etched on the underlying metal sheet, wherein the outer ring and the inner ring are of different widths, and the middle ring is a complete ring with an interdigitated structure composed of IDCs.

[0023] S2, a sample holder is placed on the resonant ring structure for measuring liquid samples;

[0024] S3, design a signal transmission circuit. The transmission circuit is a 1.6mm wide transmission line. The microstrip line has an output port and an input port. The output port at the end of the microstrip line is soldered to an SMA connector. The SMA connector is connected to a vector network analyzer.

[0025] S4 records the signal generated at the output port when no liquid is injected, i.e., when the circuit is unloaded;

[0026] S5 measures the signal generated at the output port after the liquid is injected;

[0027] S6, acquire the two signals mentioned above, and obtain the sensing information through the difference between the two.

[0028] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0029] 1. This invention employs a loaded interdigitated open-loop resonant ring structure to replace the traditional CSRR structure in sensors to achieve a sensor no-load resonant frequency of 2.65 GHz. This invention can be applied in the field of materials science for detecting the dielectric constant of liquid samples.

[0030] 2. This invention employs a narrower outer ring and an IDC (Inductively Coupled Discharge) middle ring structure to enhance the capacitance effect of the resonant structure. Compared with existing structures, this significantly improves the sensor's sensitivity when characterizing ethanol solutions of different concentrations, enabling accurate detection of the solution's dielectric constant. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the working principle of the complementary open resonant ring sensor based on the interdigital structure of the present invention;

[0032] Figure 2 This is a rear structural diagram of the complementary open-ring resonator sensor based on the interdigital structure of the present invention;

[0033] Figure 3 This is a front view of the complementary open-ring resonator sensor based on the interdigital structure of the present invention;

[0034] Figure 4 This is a schematic diagram of the back of the complementary open-ring resonator sensor based on the interdigital structure of the present invention;

[0035] Figure 5This is an equivalent circuit model diagram of the complementary open resonant ring sensor based on the interdigital structure of the present invention;

[0036] Figure 6 This is a diagram showing the no-load transmission response and electric field distribution at the resonant frequency of the complementary open resonant ring sensor based on the interdigital structure of this invention.

[0037] Figure 7 This is a waveform diagram of the positive transport coefficient of the complementary open resonant ring sensor based on the interdigitated structure of the present invention for ethanol-water binary solutions with different water volume fractions. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0039] Conversely, this invention encompasses any substitutions, modifications, equivalent methods, and solutions made within the spirit and scope of the invention as defined in the claims. Furthermore, to provide a better understanding of the invention, certain specific details are described in detail below. However, those skilled in the art will fully understand the invention even without these detailed descriptions.

[0040] In response to the shortcomings of existing technologies, the applicant has conducted in-depth research on the structure of traditional broadband high-efficiency power amplifiers in the prior art. The applicant found in the research that the traditional broadband high-efficiency power amplifiers in the prior art have relatively simple modes, relatively complex structures, are difficult to implement, have a large overall circuit size, and relatively high costs.

[0041] To overcome the shortcomings of existing technologies, see Figure 1 The diagram shows the working principle of the application system of this invention. The sensor is a two-port device with a three-layer structure: a top layer, a middle layer, and a bottom layer. The top layer includes a microstrip line 10, which has an input port. Figure 1 Port1 and output ports Figure 1The middle layer is a dielectric substrate 20; the bottom layer includes a metal sheet 31 and a three-ring complementary split ring resonator (CSRR) structure. The middle area of ​​the metal sheet 31 is an etching area used to etch the three-ring CSRR structure. The three-ring CSRR structure includes an outer ring 32, a middle ring, and an inner ring 34. The outer ring 32 and the inner ring 34 are two split resonator rings of unequal width. The middle ring 33 is a ring structure with interdigital capacitors. A sample holder 40 is fixed on the middle ring 33 to measure the complex permittivity of the liquid.

[0042] See Figure 2 This is a three-dimensional view of the sample holder 40 in this embodiment. The sample holder 40 is made of acrylonitrile-butadiene-styrene, has a cuboid structure, an inner wall width of 3 mm, and a length of 5 mm. The dielectric substrate 20 is a Rogers 4350 series dielectric substrate with a dielectric constant of 3.66, a loss tangent of 0.004, and a thickness of 0.762 mm.

[0043] See Figure 3 This is a schematic diagram of the front planar structure of the sensor based on the complementary open-loop resonator with a loaded interdigital structure in this embodiment. The width W0 of the microstrip line 10 is 1.6 mm. See also... Figure 4 This is a schematic diagram of the back planar structure of the sensor based on the complementary open-ring resonator with a loaded interdigital structure in this embodiment. In this example, the opening gap widths d1 and d2 of the outer ring 32 and inner ring 34 are both 1 mm, the width W3 of the outer ring 32 is 0.3 mm, and the widths W2 and W1 of the middle ring 33 and inner ring 34 are both 1 mm. Furthermore, the middle ring 33 is an IDC structure, where the interdigital length L1 of the IDC structure is 0.8 mm, the finger width is 0.2 mm, and the outer interdigital gap width W... I The width of the interdigitated finger gap is 0.63mm, the width of the inner interdigitated finger gap is 0.45mm, and the number of interdigitated fingers on both the outer and inner sides is 36.

[0044] See Figure 5 This is the equivalent circuit model for this embodiment. The complementary open-loop resonant rings with interdigitated structures form two parallel resonant circuits. P1 is the input port, and P2 is the output port. Their resonant frequencies are related to the inductance and capacitance of the resonant ring structure and the IDC structure, as specifically expressed below:

[0045]

[0046] When a liquid sample is added to the sample holder 40, the overall resonant frequency of the resonant circuit changes, and its resonant frequency becomes correlated with the capacitance of the liquid sample: the specific expression is as follows:

[0047]

[0048] Among them, L C C C For the capacitor and inductor in the resonant circuit formed by the inner and outer rings, C I and C S The capacitors are parallel and series capacitors with interdigitated structures; C is the coupling capacitance between microstrip line 10 and metal sheet 31; C LUT The simulation then examines the capacitance change after the sample solution is added. L represents the inductance of the microstrip line, and R represents the resistance of the microstrip line segment between the CSRR and the input / output port. LI and RI represent the inductance and resistance of the interdigitated structure, respectively.

[0049] The normalized sensitivity of a sensor is defined as:

[0050]

[0051] Where Δf is the offset of the resonant frequency; Δε is the change in the dielectric constant of the liquid sample loaded in the sample holder 40; and f0 is the resonant frequency when the circuit is unloaded.

[0052] See Figure 6 As shown in the figure, there is a very dense electric field distribution in the middle ring 33 and outer ring 32 of the upper part of the sensor. Therefore, the sample holder 40 is placed at this location to detect the dielectric constant of the liquid.

[0053] See Figure 7 The figure shows the forward transmission coefficient of the sensor in this embodiment for ethanol-water binary solutions with different water volume fractions. As can be seen from the figure, the resonant frequency decreases continuously as the water volume fraction increases, gradually decreasing from 2.13 GHz to 1.12 GHz. The overall resonant frequency change exceeds 1 GHz, indicating high sensitivity.

[0054] To achieve the above objectives, the present invention also provides a design method for a complementary open-loop resonator sensor based on an interdigital structure. The method, employing the aforementioned complementary open-loop resonator sensor based on an interdigital structure, includes the following steps:

[0055] S1, a triple complementary open-loop resonant ring structure is etched on the underlying metal sheet, wherein the outer ring and the inner ring are of different widths, and the middle ring is a complete ring with an interdigitated structure composed of IDCs.

[0056] S2, a sample holder is placed on the resonant ring structure for measuring liquid samples;

[0057] S3, design a signal transmission circuit. The transmission circuit is a 1.6mm wide transmission line. The microstrip line has an output port and an input port. The output port at the end of the microstrip line is soldered to an SMA connector. The SMA connector is connected to a vector network analyzer.

[0058] S4 records the signal generated at the output port when no liquid is injected, i.e., when the circuit is unloaded;

[0059] S5 measures the signal generated at the output port after the liquid is injected;

[0060] S6, acquire the two signals mentioned above, and obtain the sensing information through the difference between the two.

[0061] Regardless of the detailed description above, there are many ways to implement this invention. The embodiments described in this specification are merely a few specific examples of the invention. All equivalent transformations or modifications made in accordance with the spirit and essence of this invention should be covered within the scope of protection of this invention.

[0062] The detailed description of the embodiments of the present invention above is not exhaustive or intended to limit the invention to the specific forms described above. While specific embodiments and examples of the invention have been described above for illustrative purposes, those skilled in the art will recognize that various equivalent modifications can be made within the scope of the invention.

[0063] While the foregoing description has described specific embodiments of the invention and the intended optimal mode, the invention can be implemented in many ways, regardless of the level of detail described above. The details of the circuit structure and its control method described above can be varied considerably in their implementation, yet they are still included within the scope of the invention disclosed herein.

[0064] As stated above, it should be noted that the specific terminology used in describing certain features or aspects of the invention should not be used to indicate that the term is being redefined herein to limit certain particular features, characteristics, or aspects of the invention associated with that term. In short, the terminology used in the appended claims should not be construed as limiting the invention to the specific embodiments disclosed in the specification, unless these terms are expressly defined in the foregoing detailed description. Therefore, the actual scope of the invention includes not only the disclosed embodiments but also all equivalents implemented or practiced under the claims.

[0065] 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 within the protection scope of the present invention.

Claims

1. A complementary open-loop resonant sensor based on an interdigital structure, characterized in that, This sensor is a two-port device comprising a three-layer structure: a top layer, a middle layer, and a bottom layer. The top layer includes a microstrip line with an input port and an output port, the output port of which connects to an SMA connector. The middle layer is a dielectric substrate. The bottom layer includes a metal sheet and a three-ring CSRR structure. The central region of the metal sheet is an etching area used to etch the three-ring CSRR structure, which consists of an outer ring, a middle ring, and an inner ring. The outer and inner rings are two open resonant rings of unequal width. The middle ring is a ring structure with an interdigitated structure composed of IDCs. A sample holder is fixed on the middle ring to measure the complex dielectric constant of the liquid. The SMA connector is connected to the vector network analyzer to form a liquid detection system; The outer ring has a width of 0.3 mm, and the middle and inner rings have a width of 1 mm. The opening gap width of the outer ring is 1 mm; The interdigitated structure of the intermediate ring has an interdigitated finger length of 0.8 mm, a finger width of 0.2 mm, an outer interdigitated finger gap width of 0.63 mm, an inner interdigitated finger gap width of 0.45 mm, and 36 interdigitated fingers on both the outer and inner sides. The microstrip line has a width of 1.6 mm; The dielectric substrate is a Rogers 4350 series dielectric substrate with a dielectric constant of 3.66, a loss tangent of 0.004, and a thickness of 0.762 mm. The outer and inner rings, after being loaded with the interdigitated structure of the intermediate ring, form two parallel resonant circuits. Their resonant frequencies are related to the inductance and capacitance of the resonant ring structure and the IDC structure, as expressed in the following expression: ； When a liquid sample is added to the sample holder, the overall resonant frequency of the resonant circuit changes, and its resonant frequency becomes correlated with the capacitance of the liquid sample, as expressed by: ； in, , It refers to the capacitor and inductor in a parallel resonant circuit composed of an outer ring and an inner ring. It is a capacitor with an interdigitated structure. This is the coupling capacitor between the microstrip line and the metal sheet; The simulation then shows the change in capacitance after the sample solution is added. The normalized sensitivity of a sensor is defined as: ； in, This is the offset of the resonant frequency; This represents the change in dielectric constant of the liquid sample loaded in the sample holder. This is the resonant frequency of the circuit when it is unloaded. The sample holder is made of acrylonitrile-butadiene-styrene, and is rectangular in shape with an inner wall width of 3 mm and a length of 5 mm.

2. A design method for a complementary open-loop resonant sensor based on an interdigital structure, employing the complementary open-loop resonant sensor based on an interdigital structure as described in claim 1, characterized in that, Includes the following steps: S1, a triple complementary open-loop resonant ring structure is etched on the underlying metal sheet, wherein the outer ring and the inner ring are of different widths, and the middle ring is a complete ring with an interdigitated structure composed of IDCs. S2, a sample holder is placed on the resonant ring structure for measuring liquid samples; S3, design a signal transmission circuit. The transmission circuit is a 1.6mm wide transmission line. The microstrip line has an output port and an input port. The output port at the end of the microstrip line is soldered to an SMA connector. The SMA connector is connected to a vector network analyzer. S4 records the signal generated at the output port when no liquid is injected, i.e., when the circuit is unloaded; S5 measures the signal generated at the output port after the liquid is injected; S6, acquire the two signals mentioned above, and obtain the sensing information through the difference between the two.

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