Method for determining optimal microwave emission signal frequency band of winter bamboo shoot detection device

Abstract

The invention provides a method for determining the optimal microwave emission signal frequency band of a winter bamboo shoot detection device, and the method comprises the steps: analyzing the change rules of the dielectric properties of winter bamboo shoots and soil corresponding to different microwave signal frequencies and the change conditions of the dielectric properties of the soil under different water contents through measuring the water contents and dielectric properties of the winter bamboo shoots and the soil in a bamboo forest; the difference between the moisture content of the winter bamboo shoots and the moisture content of the soil is converted into the difference of dielectric properties; according to the measured dielectric property, the frequency band range with the maximum dielectric loss factor between the winter bamboo shoots and the soil is analyzed to serve as the antenna bandwidth; and constructing winter bamboo shoot-soil dielectric models under different water contents to analyze the influence on the S parameter of the antenna emission signal so as to determine the center frequency of the optimal microwave emission signal frequency band of the winter bamboo shoot detection device. And the center frequency of the optimal microwave emission signal frequency band is further verified through an antenna radiation pattern.

Description

Technical Field

[0001] The present invention relates to the technical field of winter bamboo shoot detection, and in particular to a method for determining an optimal microwave emission signal frequency band of a winter bamboo shoot detection device. Background Art

[0002] Traditional winter bamboo shoot detection methods have certain limitations, such as complex operation and low efficiency. Using microwave signals for non-destructive detection has become an emerging research direction. Microwave signals have the advantages of strong penetration and high detection accuracy, and can be effectively used in the detection of winter bamboo shoots.

[0003] However, the echo energy intensity of microwave signals is affected by the dielectric constant of the material during propagation, and the amount of energy absorbed by the material is proportional to the dielectric constant. The dielectric constant of soil increases with increasing humidity, which affects the propagation speed and reflection characteristics of microwaves in the soil. Summary of the invention

[0004] In view of the actual demand for winter bamboo shoots detection using microwave signals, the purpose of the present invention is to provide a method for determining the optimal microwave transmission signal frequency band of a winter bamboo shoot detection device. By constructing a winter bamboo shoot-soil coupling model, the mutual influence mechanism between the dielectric properties of the model and the center frequency of the microwave signal is explored, thereby determining the optimal microwave signal frequency band for winter bamboo shoot detection. This is of great significance for improving the research and development of winter bamboo shoot detectors and improving detection accuracy and efficiency, and provides a theoretical basis and technical support for the efficient detection of winter bamboo shoots.

[0005] The present invention specifically adopts the following technical solutions: A method for determining an optimal microwave transmission signal frequency band of a winter bamboo shoot detection device: by measuring the moisture content and dielectric properties of winter bamboo shoots and soil in a bamboo forest, analyzing the change rules of dielectric properties of winter bamboo shoots and soil corresponding to different microwave signal frequencies and the change of dielectric properties of soil under different moisture contents, and converting the difference between moisture contents of winter bamboo shoots and soil into the difference of dielectric properties; according to the measured dielectric properties, analyzing the frequency band range with the largest dielectric loss factor between winter bamboo shoots and soil as the antenna bandwidth; constructing winter bamboo shoot-soil dielectric models under different moisture contents to analyze the influence on the S parameters of the antenna transmission signal, so as to determine the center frequency of the optimal microwave transmission signal frequency band of the winter bamboo shoot detection device.

[0006] Furthermore, the method for determining the dielectric properties of winter bamboo shoots and soil in the bamboo forest is to use a vector network analyzer to determine the dielectric properties of winter bamboo shoots and soil samples within the frequency band of 0.001 GHz to 3.0 GHz.

[0007] Furthermore, the winter bamboo shoots-soil dielectric model is specifically as follows: using ANSYS HFSS simulation software, a cuboid is created to simulate a real soil environment; using Solidworks2020 to build a three-dimensional model of winter bamboo shoots, and importing it into ANSYS HFSS simulation software, the three-dimensional model of winter bamboo shoots is set directly below the transceiver antenna in the entire dielectric model.

[0008] Furthermore, the transceiver antenna in the winter bamboo shoot-soil dielectric model is a butterfly-shaped transceiver antenna.

[0009] Furthermore, the construction of winter bamboo shoot-soil dielectric models under different moisture contents to analyze the impact on the S parameters of the antenna transmission signal is specifically for five winter bamboo shoot-soil coupled dielectric models with soil moisture contents of 17.61%, 20.43%, 23.58%, 26.27% and 29.43% to analyze the impact of soil moisture content on the S21 parameters of the antenna transmission signal.

[0010] Furthermore, the center frequency of the optimal microwave transmission signal frequency band of the winter bamboo shoot detection device is 1.6 GHz.

[0011] Furthermore, the center frequency of the optimal microwave transmission signal frequency band of the winter bamboo shoot detection device was verified through the antenna radiation pattern.

[0012] And, a microwave antenna for a winter bamboo shoot detection device: the center frequency is 1.6 GHz.

[0013] Furthermore, a butterfly-shaped transceiver antenna is adopted. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The present embodiment is further described in detail below with reference to the accompanying drawings and specific implementation methods: Figure 1 The diagram is a diagram showing the dielectric properties of winter bamboo shoots according to an embodiment of the present invention; wherein: the left diagram is The curve changes with frequency. The right figure shows the curve changing with frequency; Figure 2 The following are the results of measuring the dielectric properties of soil in the embodiment of the present invention; The curve changes with frequency. The right figure shows the curve changing with frequency; Figure 3 Schematic diagram of a winter bamboo shoot-soil coupling model according to an embodiment of the present invention; Figure 4 Schematic diagram of an antenna-winter bamboo shoot-soil coupling model according to an embodiment of the present invention; Figure 5 7 is a graph showing the variation of the transmission coefficient of winter bamboo shoots when the moisture content of the embodiment of the present invention is different and there is no winter bamboo shoot transmission coefficient; Figure 6~Figure 10They are radiation patterns of the antenna according to the embodiment of the present invention at center frequencies of 1.5 GHz, 1.6 GHz, 1.7 GHz, 1.8 GHz and 1.9 GHz respectively. DETAILED DESCRIPTION

[0015] Hereinafter, the specific embodiments of the present application will be described in detail with reference to the accompanying drawings. According to these detailed descriptions, those skilled in the art can clearly understand the present application and can implement the present application. Without violating the principles of the present application, the features in the various embodiments can be combined to obtain new implementations, or certain features in certain embodiments can be replaced to obtain other preferred implementations.

[0016] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0017] In order to make the features and advantages of the present invention more clearly understood, the following embodiments are specifically described in detail as follows: The main design points of the embodiment of the present invention are: 1. Determine the moisture content of the soil and winter bamboo shoots in the actual bamboo forest by sampling and taking soil on the spot, and use a vector network analyzer to measure the dielectric properties of winter bamboo shoots and soil samples in the frequency range of 0.001GHz~3.0GHz, and analyze the change of dielectric properties of winter bamboo shoots and soil with the increase of microwave signal frequency and the change of dielectric properties of soil under different moisture contents. Converting the difference between the moisture content of winter bamboo shoots and soil into the difference of dielectric properties can more clearly and conveniently analyze the subsequent energy absorption of microwave signals by winter bamboo shoots and soil; 2. A method is proposed to determine the difference in dielectric constant between winter bamboo shoots and soil, construct a winter bamboo shoot-soil coupling model, study the S parameter size under the coupling model, and analyze the optimal detection frequency band for underground winter bamboo shoots. According to the measured dielectric characteristics, the frequency band with the largest dielectric loss factor between winter bamboo shoots and soil is analyzed. According to this frequency band, the antenna is designed in ANSYS HFSS 15.0 simulation software. According to the determined frequency band, it is used as the antenna bandwidth. The dielectric constant size of five groups of soils under typical moisture content is selected to construct a winter bamboo shoot-soil coupling model. Due to the complex growth environment of winter bamboo shoots and the complex underground environment, a butterfly antenna with wide-band characteristics, radiation directivity, simple structure and easy adjustment is considered as the transceiver antenna of the detection system. The butterfly antenna is designed in terms of angle, arm length, arm width and materials. According to the dielectric property measurement results of test soil samples with different mass moisture contents in the present invention, it can be known that in the process of microwave propagation underground, the energy loss is positively correlated with the dielectric loss factor. When the microwave frequency band ranges from 1.0 to 2.0 GHz, the dielectric loss factor of the five test soil samples with different moisture contents is the smallest. At 1.6 GHz, the S21 parameter reaches the lowest value, and the energy signal emitted by the antenna is absorbed the most. Therefore, the central operating frequency selected for the designed detection antenna is approximately 1.6 GHz.

[0018] 3. The antenna radiation pattern is an important parameter of antenna performance and a concrete manifestation of the antenna's far-field characteristics. It can be seen from the antenna's radiation pattern at different center frequencies that the radiation main lobe width is large and the visible angle is greater than 100, indicating that the antenna has good directional performance. When the center transmission frequency of the antenna is 1.6GHz, the maximum gain is 7.27, and the antenna has good directivity, concentrated main lobe, fewer side lobes, high gain, and good radiation efficiency, which can be better used in underground winter bamboo shoot detection. It is further verified that 1.6GHz is the optimal center frequency for the antenna to work.

[0019] In the specific implementation process of the above scheme, according to the completed dielectric property measurement experiments, such as Figure 1 , Figure 2 As shown, the relative dielectric constant of winter bamboo shoot soil is obtained.

[0020] Depend on Figure 1 As can be seen from the left figure, the relative dielectric constant They all decrease with increasing frequency, and decrease rapidly in the low frequency band, decrease significantly slowly after 300MHz, and tend to be stable in the high frequency band.

[0021] Depend on Figure 1 As can be seen from the figure on the right, the dielectric loss factor It first decreases with the increase of frequency, and then increases slightly after 1.500GHz. In the low frequency band (0-1000MHz), ion migration and electrode polarization effects are more significant. The ions and water molecules inside the winter bamboo shoots can produce a greater response in the low-frequency electric field, resulting in dielectric loss factors. Large; in the medium frequency band (1000-1500MHz), the dielectric loss factor tends to be stable, because the polarization effect begins to dominate and the ion migration effect weakens; in the high frequency band (1500-3000MHz), the molecular polarization effect and dielectric relaxation process dominate, and the dielectric loss factor Increase again.

[0022] Depend on Figure 2 As can be seen from the left figure, at different moisture contents, the dielectric constant of soil samples changes in a similar pattern with frequency; at the same measurement frequency, the dielectric constant increases with increasing moisture content; the relative dielectric constant shows a trend of first decreasing and then remaining unchanged with frequency, and decreases rapidly in the low frequency band of 0~200MHz, and remains basically unchanged after 200MHz.

[0023] Depend on Figure 2 As can be seen from the figure on the right, the dielectric loss factor When the frequency is 0-250MHz, the dielectric loss factor decreases rapidly; in the range of 250-1500MHz, it remains basically unchanged; after 1500MHz, the dielectric loss factor Gradually increase.

[0024] In further research, it was found that the reasons and mechanisms for the above changes are: in the low frequency range (0-250MHz), the ions in the soil (such as mineral ions dissolved in water) respond slowly to the electric field, so the dielectric loss factor is large at low frequencies; in the medium frequency range (250-1500MHz), the electrode polarization effect and dielectric relaxation process begin to appear, causing the dielectric loss factor to stabilize. In this frequency range, the organic matter and mineral particles in the soil have a greater impact on the loss factor; in the high frequency range (1500-3000MHz), molecular polarization and dielectric relaxation processes dominate the dielectric loss, and the polarization of water molecules has a better response to high-frequency electric fields, so the loss factor increases. At the same time, the higher the moisture content in the soil, the more significant the increase in the dielectric loss factor.

[0025] Open the ANSYS HFSS15.0 simulation software, create a 1.0m×1.0m×0.5m cuboid to simulate the real soil environment, and use Solidworks2020 to build a 3D model of winter bamboo shoots, and import it into the ANSYSHFSS15.0 simulation software. In order to observe the influence of winter bamboo shoots and soil dielectric properties on the S parameters of the antenna transmission signal, the winter bamboo shoots are located directly below the butterfly-shaped transceiver antenna in the entire dielectric model. The schematic diagram of the constructed winter bamboo shoot-soil dielectric model is shown in the figure. Figure 3 , Figure 4 shown.

[0026] The influence of soil moisture content on the S21 parameters was investigated for five winter bamboo shoot-soil coupled dielectric models with soil moisture contents of 17.61%, 20.43%, 23.58%, 26.27% and 29.43%, respectively. The results are as follows Figure 5 shown.

[0027] Depend on Figure 5 It can be seen that the greater the moisture content, the smaller the S21 parameter, the greater the loss, and the more the energy signal emitted by the antenna is absorbed; and when the center frequency is 1.6GHz, the S21 parameter reaches the lowest point, and the energy signal emitted by the antenna is absorbed the most, so the center frequency is selected to be around 1.6GHz.

[0028] Depend on Figure 6~Figure 10 It can be seen that the radiation main lobe width is large and the visible angle is greater than 100, indicating that the antenna has good directional performance. Figures 6 to 10 From the three-dimensional radiation pattern of the antenna, we can see that the maximum gain of the antenna is 7.27, and the main lobe is prominent within the frequency band, indicating that the radiation characteristics of the antenna are excellent. Figure 7 From the various performance indicators of the antenna, it can be seen that when the central transmission frequency of the antenna is 1.6GHz, the maximum gain is 7.27, and the antenna has good directivity, concentrated main lobe, fewer side lobes, high gain, and good radiation efficiency, which can be better used in underground winter bamboo shoot detection. The optimal frequency determined by the three-dimensional radiation pattern is also consistent with the effect when the S21 parameter reaches the lowest valley when the center frequency is 1.6GHz in the previous article. Therefore, the 1.6GHz frequency can be used as the signal transmission center frequency of the winter bamboo shoot detection system.

[0029] It should be noted that, unless otherwise defined, the technical terms or scientific terms used in the present invention should be understood by people with ordinary skills in the field to which the present invention belongs. The "first", "second" and similar words used in the present invention do not indicate any order, quantity or importance, but are only used to distinguish different components. "Include" or "comprise" and similar words mean that the elements or objects appearing before the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects. "Connect" or "connected" and similar words are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0030] The present invention is not limited to the above-mentioned optimal implementation mode. Anyone can derive various other forms of a method for determining the optimal microwave transmission signal frequency band of a winter bamboo shoot detection device under the inspiration of the present invention. All equal changes and modifications made according to the scope of the patent application of this embodiment should fall within the scope of the present invention.

Claims

1. A method for determining the optimal microwave transmission signal frequency band of a winter bamboo shoot detection device, characterized in that: By measuring the moisture content and dielectric properties of winter bamboo shoots and soil in bamboo forests, the changing rules of dielectric properties of winter bamboo shoots and soil corresponding to different microwave signal frequencies and the changing conditions of dielectric properties of soil under different moisture contents are analyzed, and the difference between moisture content of winter bamboo shoots and soil is converted into difference in dielectric properties. According to the measured dielectric properties, the frequency band with the largest dielectric loss factor between winter bamboo shoots and soil is analyzed as the antenna bandwidth. A winter bamboo shoot-soil dielectric model under different moisture contents is constructed to analyze the influence on the S parameters of the antenna transmission signal, so as to determine the center frequency of the optimal microwave transmission signal band of the winter bamboo shoot detection device.

2. A method for determining the optimal microwave transmission signal frequency band of a winter bamboo shoot detection device according to claim 1, characterized in that: The method for measuring the dielectric properties of winter bamboo shoots and soil in bamboo forests is to use a vector network analyzer to measure the dielectric properties of winter bamboo shoots and soil samples in the frequency band of 0.001GHz~3.0GHz.

3. A method for determining the optimal microwave transmission signal frequency band of a winter bamboo shoot detection device according to claim 1, characterized in that: The winter bamboo shoots-soil dielectric model is specifically as follows: using ANSYS HFSS simulation software, a cuboid is created to simulate a real soil environment; using Solidworks2020 to build a three-dimensional model of winter bamboo shoots, and importing it into ANSYS HFSS simulation software, the three-dimensional model of winter bamboo shoots is set directly below the transceiver antenna in the entire dielectric model.

4. A method for determining the optimal microwave transmission signal frequency band of a winter bamboo shoot detection device according to claim 3, characterized in that: The transceiver antenna in the winter bamboo shoot-soil dielectric model is a butterfly-shaped transceiver antenna.

5. A method for determining the optimal microwave transmission signal frequency band of a winter bamboo shoot detection device according to claim 1, characterized in that: The winter bamboo shoot-soil dielectric model under different moisture contents is constructed to analyze the influence on the S parameter of the antenna transmission signal. Specifically, five winter bamboo shoot-soil coupled dielectric models with soil moisture contents of 17.61%, 20.43%, 23.58%, 26.27% and 29.43% are constructed to analyze the influence of soil moisture content on the S21 parameter of the antenna transmission signal.

6. A method for determining the optimal microwave transmission signal frequency band of a winter bamboo shoot detection device according to claim 1, characterized in that: The center frequency of the optimal microwave transmission signal frequency band of the winter bamboo shoot detection device is 1.6 GHz.

7. A method for determining the optimal microwave transmission signal frequency band of a winter bamboo shoot detection device according to claim 1, characterized in that: The center frequency of the optimal microwave transmission signal frequency band of the winter bamboo shoot detection device was verified through the antenna radiation pattern.

8. A microwave antenna for a winter bamboo shoot detection device, characterized in that: The center frequency is 1.6GHz.

9. The microwave antenna for a winter bamboo shoot detection device according to claim 8, characterized in that: Adopt butterfly-shaped transceiver antenna.

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