CN110687136B - Wheat moisture microwave transmission model construction method based on COMSOL - Google Patents
Wheat moisture microwave transmission model construction method based on COMSOL Download PDFInfo
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Abstract
The invention relates to a wheat moisture microwave transmission model construction method based on COMSOL, which comprises the steps of establishing a 3D simulation model, adding material attributes, adding an electromagnetic wave source field, carrying out grid division on the 3D simulation model, defining a frequency range, calculating the 3D simulation model, and obtaining a frequency-S parameter one-dimensional curve graph; changing the water content of the wheat, observing a frequency-S parameter curve of the changed water content, and recording the change rule of the curve; forming a rule between the water content of the wheat and a frequency-S parameter curve; measuring a frequency-S parameter curve of the wheat to be measured so as to determine the water content of the wheat to be measured; under the premise of not destroying the state of the wheat, the invention adopts a microwave detection method to explore the rule between the water content of the wheat and the frequency-S parameter curve of the microwave, thereby improving the accuracy of the measurement of the water content of the wheat; meanwhile, a water content database can be quickly established according to different grain water contents with different characteristic parameters, so that the establishment of grain water standards in the grain industry is promoted.
Description
Technical Field
The invention relates to a wheat moisture microwave transmission model construction method based on COMSOL.
Background
The grain moisture content is an important quality index of grain storage safety, and the grain moisture content can be mastered in time to prevent grain mildew caused by overhigh moisture content. The traditional methods for detecting the moisture of the grains mainly comprise a capacitance method, a resistance method, a near infrared method and the like. The capacitance method has the advantages of low measurement cost, simple structure, great influence by the variety, temperature, density and the like of grains, low measurement precision and poor stability. The resistance method grain moisture measuring instrument has low price and simple structure; the defects are that the sampling requirement is high, the signal intensity is low, the contact state of the sensor and grains can influence the measurement precision, and the sensor is not suitable for measuring micro-moisture and high-moisture. The near infrared method is non-contact measurement, does not need pretreatment, and has high measurement speed and wide application range; the defects are that the grain shape and size, the density, the environmental temperature and other factors influence the measurement result. Compared with the traditional detection method, the microwave detection method has the advantages of small sensitivity to the environment, strong penetrating power, non-intrusive type, no damage to a detected object and capability of online continuous and rapid detection; however, the microwave detection method has not been widely applied to the detection of the moisture content of the grain.
Disclosure of Invention
In order to explore the rule between the wheat water content and the microwave frequency-S parameter curve and improve the accuracy of wheat water content measurement, the invention provides a wheat water microwave transmission model construction method based on COMSOL. In order to achieve the purpose, the invention adopts the following technical scheme:
a wheat moisture microwave transmission model building method based on COMSOL comprises the following steps:
step one, establishing a 3D simulation model of a transmitting antenna, a receiving antenna, air, a wheat module and a container according to structural parameters of a real object diagram;
adding material attributes to the 3D simulation model;
adding an electromagnetic wave source field to the 3D simulation model;
step four, carrying out mesh division on the 3D simulation model;
defining a frequency range in research setting;
step six, calculating the 3D simulation model to obtain a frequency-S parameter one-dimensional curve graph;
step seven, observing the change of the frequency-S parameter curve, changing the water content of the wheat, skipping to step six, observing the frequency-S parameter curve of the changed water content, and recording the change rule of the frequency-S parameter curve; forming a rule between the water content of the wheat and a frequency-S parameter curve;
and step eight, measuring a frequency-S parameter curve of the wheat to be measured, and comparing the frequency-S parameter curve with a corresponding rule between the water content of the wheat and the frequency-S parameter curve to determine the water content of the wheat to be measured.
The method for constructing the wheat moisture microwave transmission model based on COMSOL has the beneficial effects that: the method is characterized in that the whole wheat moisture microwave transmission detection system is simulated based on COMSOL simulation software, a relation graph of S21 parameters changing along with frequency can be obtained by establishing a 3D simulation model, setting material attributes of modules, carrying out grid division and setting frequency ranges, a plurality of frequency-S parameter curve graphs can be obtained by changing the water content in wheat, and the rule between the water content of the wheat and the frequency-S parameter curve is obtained by observation and analysis; the water content in the wheat to be detected is determined by measuring the frequency-S parameter curve of the wheat to be detected. According to the invention, on the premise of not damaging the wheat state, the rule between the water content of the wheat and the frequency-S parameter curve of the microwave is explored by adopting a microwave detection method, so that the accuracy of measuring the water content of the wheat is improved. The method comprehensively utilizes the interaction between microwaves and substances, and detects by measuring the change of basic parameters (such as amplitude, phase, frequency and the like) of microwave signals by utilizing the change of physical properties such as microwave reflection, penetration, scattering, cavity perturbation and the like according to the functional relation between the dielectric constant and the non-electric quantity of the material. The microwave has extremely wide frequency spectrum which can be selected, and different frequencies can be selected for measurement according to the characteristics of the object to be measured; the microwave has excellent directional radiation characteristic, and can generate good reflection when meeting various obstacles in the propagation process; the microwave measurement signal is an electric signal, and non-electric quantity conversion is not needed, so that the response speed is high; the microwave is absorbed strongly: the microwave absorption by the medium has a fixed relation with the dielectric constant of the medium, wherein the microwave absorption of water molecules is the largest, and the principle is applied to the detection of the moisture content of wheat. The method overcomes the defects of long sample preparation period and uneven sample moisture distribution in an experiment, can conveniently and quickly adjust various characteristic parameters of the medium to be detected, realizes quick modeling, and further improves the detection precision of the wheat moisture. Meanwhile, the method can effectively guide the construction of an experimental system, effectively verify the accuracy of experimental results, and quickly construct a water content database of different grain moisture contents with different characteristic parameters, thereby promoting the formulation of grain moisture standards in the grain industry.
Further, the structural parameters of the 3D simulation model comprise the distance between the two antenna models and the container model, the length, the width and the height of the container model and the angle unit of the model; the wheat model is in an ellipsoid shape, a plurality of ellipsoid-shaped areas are constructed in the container model to replace wheat grains in the grain pile, and the length, the width and the height of each area are defined in global parameters.
Has the advantages that: a plurality of ellipsoidal areas are constructed in a sample container model to replace wheat grains in a grain pile, the size and the shape of each ellipsoid can be set according to the wheat grains in the grain pile, the storage distribution of the wheat in the grain pile can be simulated by the scheme, the water content of the wheat can be quickly changed in material setting, the water content is increased or decreased for many times, different frequency-S21 parameter graphs can be obtained, and then S21 parameters under different water contents can be obtained.
Furthermore, a plurality of ellipsoidal areas are constructed inside the container model to replace wheat grains, and the size and the shape of each ellipsoid can be set according to the wheat grains in the grain pile.
Has the advantages that: the method is adopted to construct the wheat model, the distribution condition of the wheat grains in the grain stack can be obtained, each ellipsoidal adjacent area is filled with air, and pores are naturally formed, so that the independent construction of the air model is avoided, the wheat model constructed by the method is closer to the stacking condition of the wheat grains in the grain stack, and the accurate S21 transmission coefficient can be obtained.
Further, the material properties in the second step comprise the material properties of wheat and air; the material properties of the wheat comprise relative dielectric constant, relative permeability, electric conductivity and water content; the material properties of the air include relative permittivity, relative permeability, electrical conductivity, acoustic velocity, real and imaginary refractive indices.
Has the advantages that: the wheat microwave projection detection system is subjected to parameterized structural design, the material properties of wheat and air are adjusted, rapid modeling is realized, the material properties of the wheat and the air are closer to the stacking condition of wheat grains in a grain stack, and the detection accuracy is improved.
Furthermore, in the third step, a first port is arranged at one end of the 3D simulation model, a second port is arranged at the other end of the 3D simulation model, and the first port and the second port are respectively used as the transmitting antenna and the receiving antenna; and sets periodic conditions for the 3D simulation model.
Has the advantages that: in a wheat moisture microwave detection experiment, wheat to be detected is filled in a fixed container, and a first port and a second port of a 3D simulation model are respectively used as a transmitting antenna and a receiving antenna; the transmitting antenna and the receiving antenna are respectively positioned at two sides of the container to be measured and fixed on the support with unchanged relative position with the container filled with grains; the electromagnetic wave signals transmitted and received by the vector network analyzer are enabled to cover the fixed container, so that the detection accuracy is improved, and the collected receiving signals are stored and processed through a computer.
Further, the mesh division in the fourth step includes: the sequence type is set as a user control network, the size setting is selected and customized, the outer surface of the 3D simulation model is divided into triangles with any shapes, and the triangles form a free tetrahedral network.
Has the advantages that: and a formulated method is adopted to subdivide the grids, all the areas in the simulation model are divided by adopting the same method, a unit histogram with higher quality is obtained, the simulation time is shortened, and the simulation result is optimized.
Further, the defining the frequency range in the step five includes: the definition method is step length and initial frequency
[GHz]Step length of
[GHz]Frequency of stopping
[GHz]。
Has the advantages that: reasonably setting the starting frequency
[GHz]Step length
[GHz]And stopping frequency
[GHz](ii) a The frequency of the measurement system is in a reasonable range, meanwhile, the occurrence rate of calculation errors caused by the fact that the initial frequency is too small is reduced, the simulation time is saved, and the correctness of a simulation result is improved.
Further, the initial frequency of the detection method
≥0.5[GHz]Step length of
≥0.05[GHz]Frequency of stopping
Initial frequency
。
Has the advantages that: when the initial frequency is less than 0.5 GHz and the step length is less than 0.05 GHz, the electromagnetic wave cannot be effectively transmitted out of the container, and a correct frequency-S parameter curve cannot be obtained, so that the finally obtained frequency-relative dielectric constant curve graph does not accord with the actual situation.
Further, the seventh step includes: observing the change of the frequency-S parameter curve, and changing the water content of the wheat in the material setting under the condition of not changing the volume density of the wheat; and (4) observing the change of the frequency-S parameter curve after changing the water content of the wheat, and recording the change rule of the frequency-S parameter curve.
Has the advantages that: under the condition of not changing the volume density of the wheat, the change of the frequency-S parameter curve of the recorded microwave is observed by changing the water content of the wheat; determining the rule between the water content of the wheat and the frequency-S parameter curve of the microwave; the measurement of the wheat water content to be measured and the improvement of the measurement accuracy are facilitated.
Drawings
FIG. 1 is a 3D simulation model diagram of an experimental scenario;
FIG. 2 is a mesh division of a 3D simulation model;
FIG. 3 is a graph of frequency versus S parameter for a wheat moisture content of 12.5% in a sample container;
FIG. 4 is a graph of the frequency-S parameter for wheat samples in a sample container with moisture contents of 10.5%, 12.5% and 14.5%, respectively;
FIG. 5 is a frequency-S parameter curve diagram of wheat to be tested.
Detailed Description
The invention is described in further detail below with reference to the following figures and detailed description:
the concrete method of the embodiment of the method for constructing the wheat moisture microwave transmission model based on COMSOL comprises the following steps:
step one, setting the size of each module in the global definition of COMSOL simulation software according to the structural parameters of a physical map, setting the shape of each module in a component, and establishing a 3D simulation model of a transmitting antenna, a receiving antenna, air, a wheat module and a container; the axis type set by the simulation model is a z axis, and the working plane is an xy plane. The structural parameters of the 3D simulation model comprise the distance between the two antenna models and the container model, the length, the width and the height of the container model and the angle unit of the model. In the embodiment, the wheat model is set to be in an ellipsoid shape, a plurality of ellipsoid-shaped areas are constructed in the container model to replace the wheat grains in the grain pile, and the length, the width and the height of each area are defined in global parameters. The size and shape of each ellipsoid is set according to the size and shape of the wheat grains in the grain heap. A plurality of ellipsoidal areas are constructed in a sample container model to replace wheat grains in a grain pile, the size and the shape of each ellipsoid can be set according to the wheat grains in the grain pile, the storage distribution of the wheat in the grain pile can be simulated by the scheme, the water content of the wheat can be quickly changed in material setting, the water content is increased or decreased for many times, different frequency-S21 parameter graphs can be obtained, and then S21 parameters under different water contents can be obtained. Each ellipsoidal adjacent area is filled with air, pores are naturally formed, and therefore an air model is prevented from being independently constructed, the wheat model constructed by the method is closer to the stacking condition of wheat grains in a grain pile, and the accurate S21 transmission coefficient can be obtained. In other embodiments, under the precondition that the requirement on simulation precision is not high, the wheat model can be set to be a cube, a cuboid or a cylinder instead of an ellipsoid, and an air model is arranged between the unit models.
Adding material attributes to the 3D simulation model; the material properties include those of wheat and air; wherein the material properties of wheat include relative permittivity, relative permeability, electrical conductivity and water content; the material properties of air include relative permittivity, relative permeability, electrical conductivity, acoustic velocity, real and imaginary refractive indices. The wheat microwave projection detection system is subjected to parameterized structural design, the material properties of wheat and air are adjusted, rapid modeling is realized, the material properties of the wheat and the air are closer to the stacking condition of wheat grains in a grain stack, and the detection accuracy is improved. For the 3D simulation model, a middle cuboid is selected to replace a sample container, a plurality of ellipsoid domains are constructed in the middle cuboid to replace wheat grains in a grain pile, and cuboids on two sides are selected to replace air between two antennas and the container.
And step three, adding an electromagnetic wave source field to the 3D simulation model. A first port is arranged at one end of the 3D simulation model, a second port is arranged at the other end of the 3D simulation model, namely the first port is arranged on the surface of the leftmost cuboid of the 3D simulation model, and the second port is arranged on the surface of the rightmost cuboid. The first port is representative of a transmit antenna, the port type is periodic and the port's wave excitation is default to open. In the port mode setting, the input quantity is set to be a magnetic field, and the size of the magnetic mode field is x:1, y:0 and z: 0; the port input power Pin is set to 1[ W ]; the remaining settings are unchanged by default. The receiving antenna is represented by a second port, the port type being periodic, the port being set to off for wave excitation. In the port mode setting, the input quantity is set to be a magnetic field, the size of the magnetic mode field is x:1, y:0 and z:0, and the rest settings are default and unchanged.
For the 3D simulation model, two periodic conditions are added. And selecting a global coordinate system from a coordinate system in two periodic conditions, wherein the periodic type is a Floquet period, and a Floquet period k vector is set to come from a periodic port.
And step four, carrying out mesh division on the 3D simulation model. Selecting a user control network according to the sequence type, calibrating the cell size to be common physics, and setting the maximum cell size, the minimum cell size, the maximum cell growth rate, the curvature factor and the narrow region resolution of the grid in customization; in this embodiment, the outer surface of the 3D simulation model is replaced by a triangle of arbitrary shape, and the triangles constitute a geometric entity layer in the free tetrahedral network domain selection to select the whole geometry. In other embodiments, the outer surface of the 3D simulation model may also be directly divided into free tetrahedral networks.
Defining a frequency range in research setting; the definition method is step length, and the frequency parameter comprises the starting frequency
[GHz]Step length of
[GHz]And stopping frequency
[GHz](ii) a Initial frequency of the method
≥0.5[GHz]Step length of
≥0.05[GHz]Frequency of stopping
Initial frequency
(ii) a In this embodiment, the start frequency
In particular 0.5[ GHz ]]Step length of
Specifically 0.05[ GHz ]]Frequency of stopping
Is 5[ GHz ]]. In other embodiments, the start frequency
In particular 1[ GHz ]]、1.5[GHz]、2[GHz]、2.5[GHz]Or other greater than 0.5[ GHz ]]The frequency of (d); step size
Specifically 0.1[ GHz ]]、0.15[GHz]、0.2[GHz]、0.25[GHz]Or other greater than 0.05[ GHz ]]Step size of (2); wherein the stop frequency
When the frequency is larger than the initial frequency
Is greater than 0.5[ GHz ]]Any frequency of (a).
Step six, calculating a 3D simulation model to obtain a frequency-S parameter one-dimensional curve graph; according to the calculation result, deriving a frequency-S parameter curve graph after COMSOL simulation software is set; in this embodiment, the setting process of the COMSOL simulation software specifically includes: adding different parameters to obtain; the title type is selected none, the X-axis label in the plot setting is frequency (GHz), the y-axis label is S-parameter (dB), the legend is selected to be displayed in the legend, and the position is selected in the lower left corner. Locating the y-axis data in Global 1, the expression emw2.S11dB, depicted as S11, is filled in the first column, and the expression emw2.S21dB, depicted as S21, is filled in the second column. Locating the x-axis data, selecting an expression from the parameters, and clicking the replacement expression to select emw2.freq with the unit of GHz. Find line style select solid line and loop in shading and style, select loop and interpolation in line markup, define number 37, click draw. The frequency-S parameter curve is shown in fig. 3. In other embodiments, a three-dimensional drawing set can be obtained instead of the frequency-S parameter one-dimensional graph; the setting process of the COMSOL simulation software specifically comprises the following steps: the three-dimensional drawing group comprises a multi-section and a volume arrow, wherein the setting of the multi-section comprises clicking a replacement expression in the expression, and selecting emw2.Hx with the unit of A/m; setting the number of x planes as 1, the number of y planes as 0 and the number of z planes as 0 in the multi-plane data; and coloring to select a color table, selecting Wave in the color table, and finally selecting a color legend. The remaining settings are unchanged by default.
Step seven, observing the change of the frequency-S parameter curve, changing the water content of the wheat, skipping to step six, observing the frequency-S parameter curve of the changed water content, and recording the change rule of the frequency-S parameter curve; forming a rule between the water content of the wheat and a frequency-S parameter curve. In this example, the moisture content of wheat was changed in the material setting without changing the bulk density of the wheat; setting the water content of the wheat to 10.5%, 12.5% and 14.5% respectively; and forming the change of frequency-S parameter curves with different water contents; and forming a frequency-S parameter curve of a plurality of groups of wheat with different water contents, specifically as shown in figure 4, and comparing the frequency-S parameter curve of the wheat to be detected with the frequency-S parameter curve of the wheat with different water contents in figure 4. In other embodiments, different wheat volume density parameters can be set, and the frequency-S parameter curve graph of the water content and the microwave of the wheat under different volume density parameters can be measured.
Step eight, measuring a frequency-S parameter curve of the wheat to be measured, comparing the frequency-S parameter curve of the wheat to be measured with the frequency-S parameter curves of the wheat with different water contents in the graph 4 as shown in FIG. 5, and observing which curve is closest to the frequency-S parameter curve of the wheat with different water contents in the graph 4; thus, the moisture content of the closest frequency-S parameter curve pair in FIG. 4 is the moisture content of the wheat to be measured.
The concrete implementation process of the wheat moisture microwave transmission model construction method based on COMSOL comprises the following steps:
(1) and establishing a 3D simulation model according to the structural parameters of the physical map, wherein the 3D simulation model is shown in figure 1.
(2) Adding material properties to the 3D simulation model, wherein the material properties mainly comprise those of wheat and air. Specifically as shown in tables 1 and 2;
TABLE 1 wheat material Property parameter plot
| Properties | Variables of | Expression formula | Unit of |
| Relative dielectric constant | epsilonr_iso;epsilonrii=epsi;onr_iso | 3 | 1 |
| Relative magnetic permeability | mur_iso;murii=mur_iso | 0.00000125 | 1 |
| Electrical conductivity of | sigma_iso;sigmaii=sigma_iso | 0.000001 | S/m |
| Water content | w_c | 1050 | Kg/m3 |
TABLE 2 air material Property parameter plot
| Properties | Variables of | Value of | Unit of | Attribute group |
| Relative dielectric constant | epsilonr_iso;epsilonrii=epsi;onr_iso | 1 | 1 | Basic |
| Relative magnetic permeability | mur_iso;murii=mur_iso | 1.00000004 | 1 | Basic |
| Electrical conductivity of | sigma_iso;sigmaii=sigma_iso | 0.00018 | S/m | Basic |
| Real part of refractive index | n_iso;nii=n_iso | 1 | 1 | Refractive index |
| Imaginary part of refractive index | ki_iso;kiii= | 0 | 1 | Refractive index |
(3) And adding an electromagnetic wave source field to the 3D simulation model.
(4) Carrying out mesh division on the 3D simulation model; the specific structure of the mesh division is shown in fig. 2.
(5) Defining a frequency range in a research setting; wherein the starting frequency
In particular 0.5[ GHz ]]Step length of
Specifically 0.05[ GHz ]]Frequency of stopping
Is 5[ GHz ]]。
(6) And calculating the 3D simulation model to obtain a frequency-S parameter one-dimensional curve graph, wherein a frequency-S parameter curve when the water content of the wheat in the sample container is 12.5 percent is shown in figure 3.
(7) Observing the change of the frequency-S parameter curve, changing the water content of the wheat, skipping to the step six, observing the frequency-S parameter curve of the changed water content, and recording the change rule of the frequency-S parameter curve; wherein the moisture contents of wheat were set to 10.5%, 12.5% and 14.5%, respectively, and a change pattern of a frequency-S parameter curve was formed as shown in FIG. 4.
(8) Measuring a frequency-S parameter curve graph of the wheat to be measured, as shown in FIG. 5, comparing a frequency-S parameter curve in FIG. 5 with a frequency-S parameter curve in FIG. 4, observing which frequency-S parameter curve in FIG. 5 is closest to which frequency-S parameter curve in FIG. 4, wherein the water content of the frequency-S parameter curve closest to the wheat is the water content of the wheat to be measured; wherein the frequency-S parameter curve of the wheat with the water content of 10.5 percent is closest to the frequency-S parameter curve of the wheat to be detected, and the water content of the wheat to be detected is 10.5 percent.
In the present invention, unless otherwise expressly specified or limited, the terms "mounted," "connected," "secured," and the like are to be construed broadly and can, for example, be fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.
The above description is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and substitutions can be made without departing from the technical principle of the present invention, and these modifications and substitutions should also be regarded as the protection scope of the present invention.
Claims (8)
1. A wheat moisture microwave transmission model building method based on COMSOL is characterized by comprising the following steps:
step one, establishing a 3D simulation model of a transmitting antenna, a receiving antenna, air, a wheat module and a container according to structural parameters of a real object diagram;
adding material attributes to the 3D simulation model;
adding an electromagnetic wave source field to the 3D simulation model;
step four, carrying out mesh division on the 3D simulation model;
defining a frequency range in research setting;
sixthly, calculating the 3D simulation model, wherein the structural parameters of the 3D simulation model comprise the distance between the two antenna models and the container model, the length, the width and the height of the container model and the angle unit of the model; the wheat model is in an ellipsoid shape, a plurality of ellipsoid-shaped areas are constructed in the container model to replace small wheat grains in the grain pile, and the length, the width and the height of each area are defined in global parameters; obtaining a frequency-S parameter one-dimensional curve graph;
step seven, observing the change of the frequency-S parameter curve, changing the water content of the wheat, skipping to step six, observing the frequency-S parameter curve of the changed water content, and recording the change rule of the frequency-S parameter curve; forming a rule between the water content of the wheat and a frequency-S parameter curve;
and step eight, measuring a frequency-S parameter curve of the wheat to be measured, and comparing the frequency-S parameter curve with the rule between the water content of the wheat and the frequency-S parameter curve to determine the water content of the wheat to be measured.
2. A COMSOL-based wheat moisture microwave transmission model building method as claimed in claim 1, wherein a plurality of ellipsoid areas are built inside the container model to replace wheat grains, and the size and shape of each ellipsoid can be set according to the wheat grains in the grain bulk.
3. The COMSOL-based wheat moisture microwave transmission model building method of claim 1, wherein the material properties in step two comprise the material properties of wheat and air; the material properties of the wheat comprise relative dielectric constant, relative permeability, electric conductivity and water content; the material properties of the air include relative permittivity, relative permeability, electrical conductivity, acoustic velocity, real and imaginary refractive indices.
4. The COMSOL-based wheat moisture microwave transmission model building method of claim 1, wherein in the third step, one end of the 3D simulation model is provided with a first port, the other end is provided with a second port, and the first port and the second port are respectively used as the transmitting antenna and the receiving antenna; and sets periodic conditions for the 3D simulation model.
5. The COMSOL-based wheat moisture microwave transmission model building method of claim 1, wherein the meshing in the fourth step comprises: the sequence type is set as a user control network, the size setting is selected and customized, the outer surface of the 3D simulation model is divided into triangles with any shapes, and the triangles form a free tetrahedral network.
6. The COMSOL-based wheat moisture microwave transmission model building method of claim 1, wherein the defining the frequency range in the fifth step comprises: the definition method is step length and initial frequency
[GHz]Step length of
[GHz]Frequency of stopping
[GHz]。
7. COMSOL-based wheat moisture microwave-transmissive mold according to claim 6A method of pattern construction characterized by an initial frequency
≥0.5[GHz]Step length of
≥0.05[GHz]Frequency of stopping
Initial frequency
。
8. The COMSOL-based wheat moisture microwave transmission model building method of claim 1, wherein said seventh step comprises: observing the change of the frequency-S parameter curve, and changing the water content of the wheat in the material setting under the condition of not changing the volume density of the wheat; and (4) observing the change of the frequency-S parameter curve after changing the water content of the wheat, and recording the change rule of the frequency-S parameter curve.
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