A microstrip antenna sensor and a salt solution concentration measurement system and method

Abstract

The present invention provides a microstrip antenna sensor and a salt solution concentration measurement system and method. The microstrip antenna sensor includes a dielectric substrate, on one side of which there is a metal disk; on the other side there is a CSRR structure ground plane and a coaxial feeding structure; the metal disk is used as an antenna radiator to penetrate into the salt solution to be measured to sense the change in the dielectric constant of the salt solution, and the CSRR structure ground plane is a split metal ring structure, and the resonant frequency of the microstrip antenna sensor is adjusted by adjusting the geometric parameters of the split metal ring. By detecting the resonant frequency (reflection coefficient of the coaxial feeding port) of the microstrip antenna sensor with a vector network analyzer, the concentration value of the salt solution to be measured can be deduced. The size of the microstrip antenna sensor is optimized, and a microwave antenna with an electrical size of only 0.23λ is realized. The microstrip antenna sensor also exhibits high sensitivity, with a sensitivity of 0.367 (kHz / (mg / L)), and can make a rapid and accurate response to small changes in salinity concentration.

Description

Technical Field

[0001] This invention patent relates to the field of microwave measurement technology, and particularly to a microstrip antenna sensor and a salt solution concentration measurement system and method. Background Art

[0002] An antenna is a device for transmitting electromagnetic waves, used to send or receive radio waves. It is an important component in an electronic communication system, responsible for converting electrical signals into electromagnetic waves for transmission, or converting received electromagnetic waves into electrical signals. The basic principle of an antenna is to use the change of current to generate an electromagnetic field, thereby emitting electromagnetic waves, or to cause a change in current by receiving electromagnetic waves, thereby generating electrical signals. This process follows Maxwell's equations and the basic principles of electromagnetic induction. Sodium is one of the essential nutrients for maintaining human body functions, but excessive intake can lead to high blood pressure and increase the risk of heart disease, stroke, and premature death. In addition, more and more evidence shows that high sodium intake is associated with an increased risk of other health problems such as gastric cancer, obesity, osteoporosis, and kidney disease. In daily life, sodium intake mainly comes from sodium chloride, that is, the common table salt we know. Therefore, people use various methods to measure the salt concentration in food, such as the traditional methods of gravimetry, titration, infrared absorption spectroscopy, and spectrophotometry, but these methods all have some disadvantages, such as time-consuming, expensive, and not easy to carry. Summary of the Invention

[0003] The purpose of the present invention is to overcome the deficiencies in the prior art and provide a microstrip antenna sensor and a salt solution concentration measurement system and method.

[0004] To solve the problems of the prior art, the present invention discloses a microstrip antenna sensor, including a dielectric substrate, on one side of which there is a metal disk; on the other side, there is a CSRR structure ground plane and a coaxial feeding structure; the metal disk, as the antenna radiator, is immersed in the salt solution to be measured to sense the change of the dielectric constant of the salt solution, and the CSRR structure ground plane is a split metal ring structure, and the resonant frequency of the microstrip antenna sensor is adjusted by adjusting the geometric parameters of the split metal ring.

[0005] Further, the CSRR structure ground plane includes a first ring, a second ring, and a third ring. The inner side of the first ring is connected to the second ring through a first connecting part, the outer side of the second ring is connected to the third ring through a second connecting part, and the third ring is provided with a notch.

[0006] Further, the coaxial feeding port includes a signal transmission port and a feeding probe, and the feeding probe penetrates through the dielectric substrate to connect to the metal disk.

[0007] Correspondingly, a salt solution concentration measurement system includes a vector network analyzer, a host computer, and the above-mentioned microstrip antenna sensor. The coaxial feeding structure is connected to the vector network analyzer through a coaxial cable; the vector network analyzer is connected to the host computer.

[0008] Correspondingly, a method for measuring the concentration of a salt solution:

[0009] The metal disc of the microstrip antenna sensor is immersed in the salt solution;

[0010] The vector network analyzer measures the resonant frequency of the microstrip antenna sensor and transmits it to the host computer;

[0011] The host computer calculates the concentration of the salt solution based on the resonant frequency.

[0012] Furthermore, the calculation formula for the concentration of the salt solution is:

[0013] C = 439723.74679 + 54.74243·t - 639959.22258·f 0 + 0.0023·t 2 + 232847.93747·f 0 2 - 40.00776·t·f 0

[0014] t is the temperature, f 0 is the resonant frequency, and C is the concentration of the solution.

[0015] The beneficial effects of the present invention are:

[0016] The size of the microstrip antenna sensor provided by the present invention can be made very small, with good portability, and can also be easily integrated into various devices and systems; it also exhibits high sensitivity and can respond quickly and accurately to small changes in the concentration of the solution to be measured. The measurement method applying the microstrip antenna sensor of the present invention can achieve real-time instant feedback; at the same time, the microstrip antenna sensor of the present invention has a simple structure and low cost, and is more easily implemented and deployed in practical applications. Description of the Drawings

[0017] Figure 1 is a schematic structural diagram of the microstrip antenna sensor of the present invention;

[0018] Figure 2 is a schematic diagram of the salt solution concentration measurement system of the present invention;

[0019] Figure 3 is a schematic diagram of the result of the two-dimensional fitting surface of the concentration of the salt solution to be measured with respect to temperature and frequency of the present invention.

[0020] Figure 4It is a schematic diagram of the return loss S11 results of the resonant frequency of the microstrip antenna sensor of the present invention at different concentrations of the salt solution to be measured at room temperature of 25°C.

[0021] Figure 5 It is a graph of the resonant frequency of the microstrip antenna sensor of the present invention at different concentrations of the salt solution to be measured at 25°C.

[0022] Reference numerals:

[0023] 1. Dielectric substrate; 2. Metal disk; 3. CSRR structure ground plane; 4. Coaxial feeding structure; 5. Vector network analyzer; 6. Salt solution; 7. Container; 8. Coaxial feeder cable; 9. Data line; 10. Host computer; 31. First ring; 32. First connecting part; 33. Second ring; 34. Second connecting part; 35. Third ring. Detailed implementation manners

[0024] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention and cannot be used to limit the protection scope of the present invention.

[0025] As Figure 1As shown, the microstrip antenna sensor of the present invention is characterized in that it includes a dielectric substrate 1, on one side of which there is a metal disk 2; on the other side there is a CSRR structure ground plane 3 and a 50Ω coaxial feed port 4; the metal disk 2 serves as an antenna radiator and is immersed in the salt solution to be measured to sense the change in the dielectric constant of the salt solution. The CSRR structure ground plane 3 is a split metal ring structure, and the resonant frequency of the microstrip antenna sensor is adjusted by adjusting the geometric parameters of the split metal ring. The material of the dielectric substrate 1 is other common materials similar to FR4 board, with a relative dielectric constant of 4.4 and a loss tangent of 0.02. It has low cost and relatively low price, and is suitable for large-scale production; it has high mechanical strength and high mechanical strength and rigidity, which helps to maintain the stability and durability of the microstrip antenna sensor structure. It has good thermal stability and can maintain relatively stable performance under different temperature conditions; it has good process adaptability, is easy to process, and can produce complex microstrip antenna sensor structures through conventional manufacturing processes. Both the metal disk 2 and the CSRR structure ground plane 3 are metal sheets, which effectively reduces the height of the microstrip antenna sensor and is conducive to the optimized design of the microstrip antenna sensor structure. The split metal ring of the CSRR structure ground plane 3 includes a first ring 31, a second ring 33 and a third ring 35. The inner side of the first ring 31 is connected to the second ring 33 through a first connecting portion 32, and the outer side of the second ring 33 is connected to the third ring 35 through a second connecting portion 34. The third ring 35 is provided with a notch. First, by adjusting the geometric parameters of the split metal ring, the resonant frequency of the microstrip antenna sensor can be adjusted. The CSRR structure ground plane 3 can also make the structure of the microstrip antenna sensor very compact. The CSRR structure ground plane 3 makes the microstrip antenna sensor show extremely high sensitivity in sensing the change in solution concentration. When the salt solution concentration changes, the dielectric constant of the salt solution also changes, and the current distribution characteristics of the CSRR structure ground plane 3 will change accordingly, thereby affecting the resonant characteristics of the microstrip antenna sensor. The coaxial feed port 4 is composed of a signal transmission port with a radius of 1.5mm and a coaxial probe with a radius of 0.6mm and a height of 4.6mm, which improves the electrical performance stability of the microstrip antenna sensor.

[0026] As Figure 2As shown in the figure, a salt solution concentration measurement system based on the above microstrip antenna sensor; the metal disc 1 of the microstrip antenna sensor is immersed in the salt solution 6 to be measured, the depth of the salt solution to be measured is 50 mm, and the container 7 for holding the salt solution to be measured is a glassware with a radius of 50 mm, a height of 100 mm, and a wall thickness of 2 mm. The coaxial feed port 4 of the microstrip antenna sensor is connected to the vector network analyzer 5 through the coaxial cable 8. The coaxial cable 8 serves as the feed line of the microstrip antenna sensor, has low transmission loss, can effectively improve the signal transmission efficiency, and is usually stably connected and easy to maintain; the vector network analyzer (LiteVNA64 - 4-inch - 0.3.1 version) is used, and the measurable range is 50k - 6.3 GHz. The vector network analyzer 5 measures the resonant frequency of the microstrip antenna sensor and is connected to the upper computer 10 through the data line 9; the upper computer uses software to automatically invert the concentration of the salt solution to be measured.

[0027] Correspondingly, a measurement method using the above measurement system:

[0028] Step1 Use CST electromagnetic simulation software to simulate the salt solution to be measured with different concentrations at different temperatures, obtain their corresponding resonant frequencies, draw a two-dimensional surface diagram of temperature, resonant frequency and the concentration of the salt solution to be measured, and obtain the fitting relationship formula of the concentration of the salt solution to be measured with respect to temperature and resonant frequency according to the two-dimensional surface diagram;

[0029] Step2 The microstrip antenna sensor immerses the front metal disc 2 into the salt solution 6 to be measured as required, and the microstrip line sensor is connected to the vector network analyzer 5 through the coaxial cable 8 at the coaxial feed port 4;

[0030] Step3 The vector network analyzer 5 detects the resonant frequency of the microstrip antenna sensor and transmits it to the upper computer 10 of the vector network analyzer 5 through the data line 9;

[0031] Step4 The upper computer 10 automatically downloads the resonant frequency measured by the vector network analyzer 5, uses Python software for data processing, and automatically inverts the concentration value of the salt solution to be measured by using the relationship between the resonant frequency of the microstrip antenna sensor and the concentration of the salt solution to be measured.

[0032] The calculation formula for the salt solution concentration is:

[0033] C = 439723.74679 + 54.74243·t - 639959.22258·f 0 + 0.0023·t 2 + 232847.93747·f 0 2 - 40.00776·t·f 0

[0034] t is the temperature, f 0 is the resonant frequency, and C is the concentration of the solution.

[0035] As Figure 3 shown, a 2D surface plot of the concentration of the salt solution to be measured with respect to the unknowns temperature and resonant frequency is fitted using the ploy2D model, and the fitting plane R 2 = 0.99238.

[0036] As Figure 4 shown, the measured temperature is 25 °C, the measured frequency band is 1.1 - 1.7 GHz, and the resonant frequency increases with the increase in the concentration of the salt solution to be measured.

[0037] As Figure 5 shown, the resonant frequency measured by the vector network analyzer changes with the change in the concentration of the salt solution to be measured. When the concentration of the salt solution to be measured increases, the resonant frequency also gradually increases, and the trend of the entire experimental frequency band is basically consistent with the simulation results.

[0038] It can be concluded that: From Figure 3 and Figure 4 it can be concluded that the coverage bandwidth of CST is between 1.28 GHz and 1.5 GHz, and the resonant frequency is between 1.3746 and 1.3898 GHz. The maximum sensitivity of this microstrip antenna sensor after being immersed in the salt solution to be measured is 0.367 (kHz / (mg / L)), and the electrical size is 0.23λ. Through detailed analysis, simulation, and measurement, results with good consistency are obtained. These results provide a low-cost solution for authoritative institutions, managers in the food industry, and consumers, and can be used to accurately determine the salt content in food.

[0039] It should be noted that in this text, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, such that a process, method, article or device comprising a series of elements not only includes those elements but also includes other elements not expressly listed, or further includes elements inherent to such process, method, article or device. At the same time, in the description of the present invention, it should be understood that the orientation or positional relationship indicated by terms such as "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention. Also, in the drawings of the present invention, the filling pattern is only for differentiating layers and is not subject to any other limitations.

[0040] Although the embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for measuring the concentration of a salt solution, characterized in that: The invention comprises a vector network analyzer (5), a host computer (10) and a microstrip antenna sensor, wherein the microstrip antenna sensor comprises a dielectric substrate (1), one side of the dielectric substrate (1) is provided with a metal disk (2); the other side is provided with a CSRR structure ground plane (3) and a coaxial feeding structure (4); the metal disk (2) is used as an antenna radiator to penetrate into a salt solution to be tested to sense changes in the dielectric constant of the salt solution; the CSRR structure ground plane (3) is a split metal ring structure; and the resonant frequency of the microstrip antenna sensor is adjusted by adjusting the geometric parameters of the split metal ring; The CSRR structure ground plane (3) comprises a first circular ring (31), a second circular ring (33) and a third circular ring (35); the inner side of the first circular ring (31) is connected to the second circular ring (33) via a first connecting portion (32); the outer side of the second circular ring (33) is connected to the third circular ring (35) via a second connecting portion (34); and the third circular ring (35) is provided with a notch; The coaxial feeding structure (4) is connected to a vector network analyzer (5) via a coaxial feeding cable (8); the vector network analyzer (5) is connected to a host computer (10); The metal disk (2) of the microstrip antenna sensor is immersed in a salt solution; The vector network analyzer measures the resonant frequency of the microstrip antenna sensor and transmits it to the host computer; The host computer calculates the concentration of the salt solution based on the resonant frequency; The formula for calculating the concentration of salt solution is: ； t is temperature, f 0 is the resonant frequency and C is the concentration of the solution.

2. The method for measuring the concentration of a salt solution according to claim 1, characterized in that: The coaxial feeding structure (4) comprises a coaxial feeding signal transmission port and a feeding probe, wherein the feeding probe penetrates the dielectric substrate (1) and connects to the metal disc (2).

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