TW202317977A - Tuning fork-shaped coupled microwave sensor including a microwave resonant cavity and a signal feed-in member or a microwave transmitting member - Google Patents

Abstract

Disclosed are a coupled microwave sensor and a method for obtaining a linear regression equation of the signal value of the coupled microwave sensor and the moisture content of an object. The coupled microwave sensor of the present invention includes a microwave resonant cavity and a signal feed-in member or a microwave transmitting member. A to-be-measured object is placed in the exterior of the microwave resonant cavity, and the signal feed-in member or the microwave transmitting member transmits microwave, such that after the microwave passes through the to-be-measured object, the resonant frequency of the microwave resonant cavity is measured to obtain the water content of the to-be-measured object. In addition, a highly accurate linear regression equation is obtained as a reference for measuring the water content of unknown water-containing objects by measuring the corresponding resonant frequency of a plurality of objects with known moisture content, and by calculating correlation coefficients to eliminate the combinations with low correlation coefficients.

Description

Tuning-fork-shaped coupled microwave sensor and method for obtaining the linear regression formula between the signal value of the coupled microwave sensor and the moisture content of the object

The present invention relates to the technical field of measuring the water content of objects with microwaves, in particular to a vortex vortex that utilizes microwave feed-in parts or microwave emitters to excite a resonant electric field and measures the change of resonant frequency to measure the water content of objects. A coupled microwave sensor, a tuning fork coupled microwave sensor and a linear regression method for obtaining the signal value of the coupled microwave sensor and the moisture content of an object.

The storage of various agricultural products, forestry products and even food often causes the moisture content to increase due to the absorption of moisture in the air, resulting in mildew, or the moisture content of the product is greatly reduced due to the climate being too dry, plus The temperature rises and thus leads to combustion and so on. Therefore, monitoring the moisture content of items becomes very important.

The traditional method of measuring the moisture content of an item is to heat the item to evaporate the water in the item, and then calculate the weight difference before and after heating to obtain the moisture content of the item. However, this method is quite time-consuming, and due to sampling inspection, it is not easy to know the moisture content of the whole product due to insufficient number of samples. Therefore, an online moisture content measuring instrument has been developed.

The existing on-line moisture content measuring instruments are mainly divided into two types: contact type and non-contact type. The contact type is to measure the moisture content of the object by contacting the moisture content measuring instrument with the object to be measured, while the non-contact type is to use a transmitter to emit electromagnetic waves, make it pass through the object, and then be received by a receiver to measure the electromagnetic wave. The moisture content of the item is measured by the change of the property. The non-contact online moisture content measuring instrument can be used in many occasions due to its small size and small installation space requirements. Therefore, the development of non-contact online moisture content measuring instrument is an important trend at present.

In view of this, the object of the present invention is to provide a vortex-shaped coupled microwave sensor, a tuning fork-shaped coupled microwave sensor and a method for obtaining the linear regression formula of the signal value of the coupled microwave sensor and the moisture content of the object, which utilize microwave The resonant cavity is used as a sensing head for sensing the moisture content of the item. The item is placed in the scattered field formed by the microwave or after the microwave passes through the item to measure the change of the resonant frequency, and then the moisture content of the item is measured.

An embodiment of the vortex coupling microwave sensor of the present invention includes a bottom wall, an inner shaft body, an outer ring body, a connecting piece, a microwave feed-in piece and an insulating cover. The bottom wall is round. There is a distance between the inner shaft body and the bottom wall and a center. The outer ring body is arranged on the bottom wall and surrounds the inner shaft body, and the outer ring body and the inner shaft body are arranged concentrically. The connecting piece is connected with the inner shaft body at a first position and connected with the outer ring body at a second position, and the first position and the second position have an angular distance of 90 degrees relative to the center. The microwave feed-in piece is arranged at the center of the inner shaft body. The insulating cover is arranged on the axial end surface of the outer ring body and covers the inner shaft body. The bottom wall, the outer ring body, the inner shaft body and the insulating cover form a microwave resonance chamber.

In another embodiment, the connector includes an arc-shaped body, a first connecting portion and a second connecting portion, the arc-shaped body is arranged on the bottom wall and is located between the inner shaft body and the outer ring body, and the first connecting portion One end of the arc-shaped body is connected with the inner shaft body, and the second connecting part is connected with the other end of the arc-shaped body and the outer ring body.

In another embodiment, the arc-shaped body is a circular arc body with a central angle of 90 degrees relative to the center.

In another embodiment, the outer ring body has a notch, the notch is disposed at the joint of the connecting piece and the outer ring body, and the second connecting portion is disposed in the notch.

In another embodiment, the length of the first connecting portion is twice the length of the second connecting portion.

An embodiment of the tuning fork-shaped coupled microwave sensor of the present invention includes a base, a pair of semi-cylindrical resonant cavities, a microwave emitting element and a pair of electromagnetic coupling elements. A pair of semi-cylindrical resonant cavities are arranged on the base, each semi-cylindrical resonant cavity includes a semi-cylindrical shell and an insulating cover covering the semi-cylindrical shell, the insulating cover system of the pair of semi-cylindrical resonant cavities set opposite to each other and separated by a predetermined distance. The microwave emitting part is arranged in one of the semi-cylindrical resonant cavities. The microwave receiving part is arranged in another semi-cylindrical resonant cavity, and the microwave emitting part and the microwave receiving part are arranged facing each other. A pair of electromagnetic coupling parts are respectively arranged in the pair of semi-cylindrical resonant cavities, and are vertically arranged with the microwave transmitting part and the microwave receiving part respectively.

In another embodiment, the pair of electromagnetic coupling parts are respectively arranged close to the insulating cover, there is a distance between the electromagnetic coupling part and the microwave emitting part, and there is a distance between the electromagnetic coupling part and the microwave receiving part. spacing.

In another embodiment, the microwave transmitting part and the microwave receiving part are respectively equidistant from the two axial end faces of the semi-cylindrical shell, and the axial length of the semi-cylindrical shell is 1/2 of the wavelength of the electromagnetic wave corresponding to the resonant frequency.

In another embodiment, the distance between the microwave transmitting part and the microwave receiving part and one axial end face of the semi-cylindrical shell is three times the distance from the other axial end face of the semi-cylindrical shell, and the semi-cylindrical shell The axial length of the body is equal to the wavelength of the electromagnetic wave corresponding to the resonant frequency.

An embodiment of the method of obtaining the linear regression formula between the signal value of the coupled microwave sensor and the moisture content of the object in the present invention includes the following steps: using the microwave sensor to obtain the signal values of N items with different moisture content; Obtain the number of combinations of n signal values from the signal values; calculate the correlation coefficient of each combination; determine whether the correlation coefficients meet the target; if not all the correlation coefficients meet the target, obtain the N signal values The number of combinations of n-1 signal values, and calculate the correlation coefficient of each combination; if all the correlation coefficients meet the target, the combination with the best correlation coefficient is obtained; the signal value is calculated based on the signal value of the best correlation coefficient combination The linear regression formula for ; complete the corrected regression.

The coupled microwave sensor of the present invention excites electromagnetic waves through a special coupling structure, generates a scattered field above the coupled microwave sensor and passes through the object to be measured, and measures the resonant frequency of the microwave resonant cavity, and when the water content of the object increases It will cause the resonant frequency of the microwave resonant cavity to decrease, so that the water content of the object can be measured. At the same time, the signal value of multiple objects with known water content is measured by the coupled microwave sensor, and the combination of the best correlation coefficient is obtained by judging whether the correlation coefficient of each combination of water content and signal value meets the target value , so as to obtain the linear regression formula between the signal value of each coupled microwave sensor and the moisture content of the object.

Please refer to FIG. 1 , FIG. 2 , FIG. 3 and FIG. 4 , which show an embodiment of a vortex coupling microwave sensor. The vortex coupled microwave sensor of this embodiment includes a bottom wall 10 , an inner shaft body 20 , an outer ring body 30 , a connecting piece 40 , a microwave feed-in piece 50 and an insulating cover 60 .

The bottom wall 10 is a circular disk. The inner shaft body 20 is a cylindrical shaft body. There is a distance between the inner shaft body 20 and the bottom wall 10 . The inner shaft body 20 has a center 21 , and a through hole is formed at the center 21 for setting the microwave feed-in component 50 described later. The outer ring body 30 is disposed on the bottom wall 10 and connected to the edge of the bottom wall 10 to form a cylindrical structure. The outer ring body 30 surrounds the inner shaft body 20 and is arranged concentrically with the inner shaft body 20 .

The connecting member 40 is connected to the inner shaft body 20 at a first position and is connected to the outer ring body 30 at a second position, and the first position and the second position have an angular distance of 90 degrees relative to the center 21 . The connector 40 includes an arc-shaped body 41, a first connecting portion 42 and a second connecting portion 43. The arc-shaped body 41 is arranged on the bottom wall 10 and is located between the inner shaft body 20 and the outer ring body 30. The arc-shaped body 41 is an arcuate body with a central angle of 90 degrees relative to the center 21 . The first connecting part 42 connects one end of the arc-shaped body 41 and the inner shaft body 20, the second connecting part 43 connects the other end of the arc-shaped body 41 and the outer ring body 30, and there is a gap between the connecting piece 40 and the bottom wall 10 as a whole. spacing. In this embodiment, the length of the first connecting portion 42 is twice the length of the second connecting portion 43 , that is, the arc-shaped body 41 is arranged closer to the outer ring body 30 . The outer ring body 30 has a notch 31 , and the notch 31 is disposed at the joint between the connecting member 40 and the outer ring body 30 , and the second connecting portion 43 is disposed in the notch 31 and connected to the outer ring body 30 .

The bottom wall 10 , the inner shaft body 20 , the outer ring body 30 , the connector 40 and the insulating cover 60 form a microwave resonant cavity. The structure of the bottom wall 10, the inner shaft body 20, the outer ring body 30, and the connecting piece 40 can be made by additive manufacturing (three-dimensional printing). The material is polylactic acid plastic (PLA), and two layers are formed on the surface. Coating, the first layer is a nickel layer, the second layer is a chromium layer.

The microwave feeding element 50 is disposed at the center 21 of the inner shaft body 20 . The microwave feed-in 50 of this embodiment is an SMA probe connector, and a single port of a network analyzer is connected to the microwave feed-in 50 as a signal feed-in source.

The insulating cover 60 is disposed on an axial end surface of the outer ring body 30 and opposite to the bottom wall 10 , and the insulating cover 60 covers the inner shaft body 20 and the connecting member 40 . The insulating cover 60 can be made of insulating ceramic. The insulating cover 60 is used to carry the object to be sided and prevent the object to be sided from entering the microwave resonant cavity. On the other hand, since ceramics have a high dielectric coefficient, the charge value of the microwave resonant cavity can be increased, so even if the moisture content of the object changes slightly It can also be distinguished, thereby improving the analytical ability of moisture content measurement. The dielectric coefficient of the insulating cover 60 in this embodiment is 9-10.

Please refer to FIG. 5 , which shows that when no object is placed above the insulating cover 60 of the vortex coupling microwave sensor, that is, when there is only air above the insulating cover 60 , the resonant frequency of the microwave resonant cavity is 1 GHz. Please refer to Fig. 6, which shows that when objects with different water contents are placed on the insulating cover 60 of the vortex coupling microwave sensor, the change of the resonant frequency corresponding to each object of the vortex coupling microwave sensor is measured, and the water content The higher the value, the lower the resonant frequency. The resonant frequency of only air above is 1GHz. As the water content of the object to be measured is higher, the resonant frequency measured by the vortex coupling microwave sensor is lower. This is because the dielectric coefficient of the object itself is low, about 2 The dielectric coefficient of water is about 10, and the dielectric coefficient of water is 79 to 81. Therefore, when the moisture content of the object increases, the water will increase the dielectric coefficient of the object on the side, resulting in a decrease in the resonance frequency of the microwave resonant cavity, and at the same time reduce the amplitude. Therefore, the moisture content of the object to be detected can be measured by measuring the change of the resonant frequency of the microwave resonant cavity by the object to be measured by the influence of the dielectric coefficient of the object to be detected on the resonant frequency. The curve in the center of Fig. 6 shows the resonant frequency when there is only air above the insulating cover 60, and the distribution of the curve in the direction of frequency reduction is dry objects, objects with a moisture content of Y%, and the moisture content of (Y+N) % of objects.

Please refer to FIG. 7 , FIG. 8 , FIG. 9 and FIG. 10 , which show an embodiment of the tuning fork type coupled microwave sensor of the present invention. The tuning-fork coupled microwave sensor of this embodiment includes a base 70 , a pair of semi-cylindrical resonant cavities 80 , a microwave emitting element 90 , a microwave receiving element 100 and a pair of electromagnetic coupling elements 110 .

The base 70 is cylindrical, and a pair of semi-cylindrical resonant cavities 80 are disposed on an axial end surface of the base 70 . Each semi-cylindrical resonant cavity 80 includes a semi-cylindrical shell 81 and an insulating cover 82 covering the semi-cylindrical shell 81 . The radius of each semi-cylindrical shell 81 is less than the radius of the base 70, so the edge of the middle part of the semi-cylindrical shell 81 is flush with the edge of the base 70, and the insulating cover 82 of a pair of semi-cylindrical resonant cavity 80 The systems are arranged facing each other and are separated by a predetermined distance. The insulating cover 82 of this embodiment is made of Teflon, which prevents the object to be side from entering the semi-cylindrical resonant cavity 80 and affecting the resonant mode of the cavity.

The microwave emitting element 90 is arranged in a semi-cylindrical resonant cavity 80 . The microwave receiver 100 is arranged in another semi-cylindrical cavity 80 , and the microwave emitter 90 and the microwave receiver 100 are arranged facing each other. The microwave transmitting part 90 of the present embodiment and the microwave receiving part 100 are metal probe structures, the microwave transmitting part 90 of the present embodiment and the microwave receiving part 100 are SMA probe joints, and the two ports of the commercially available network analyzer They are respectively connected to the microwave transmitting part 90 and the microwave receiving part 100 as the signal feeding end and the signal receiving end, and then the frequency spectrum of the resonant cavity is measured by using a network analyzer. One end of the microwave transmitting part 90 and one end of the microwave receiving part 100 are respectively fixed on the semi-cylindrical casing 81 of the semi-cylindrical resonant cavity 80, and these ends are connected to wires as a signal feed-in and output structure. The other ends of the microwave emitting element 90 and the microwave receiving element 100 are disposed in the semi-cylindrical resonant cavity 80 and have a distance from the insulating cover 82 respectively. The microwave emitting part 90 and the microwave receiving part 100 are aligned with each other.

A pair of electromagnetic coupling elements 110 are respectively disposed in a pair of semi-cylindrical resonant cavities 80 , and are perpendicular to the microwave emitting element 90 and the microwave receiving element 100 . The electromagnetic coupling part 110 of this embodiment is a metal rod-shaped body, which extends along the axial direction of the semi-cylindrical resonant cavity 80 and is arranged at a position corresponding to the centerline of the insulating cover 82 . In this embodiment, there is a distance between the electromagnetic coupling element 110 and the insulating cover 82 . The microwave transmitting part 90 and the microwave receiving part 100 are perpendicular to the electromagnetic coupling part 110 , and the distance between the microwave transmitting part 90 and the microwave receiving part 100 and the insulating cover 82 is greater than the distance between the electromagnetic coupling part 110 and the insulating cover 82 .

By feeding in the signal, the microwave launcher 90 emits microwaves, and the microwave passes through the insulating cover 82 of the semi-cylindrical resonant cavity 80 on one side and passes through the object to be treated, and then passes through the insulation of the semi-cylindrical resonant cavity 80 on the other side. The cover 82 is received by the microwave receiver 100 . At this time, measuring the resonant frequency of the semi-cylindrical resonant cavity 80 can obtain the water content of the object to be sided.

For the tuning fork type coupling microwave sensor shown in Fig. 9 and Fig. 10, its microwave transmitting part 90 and microwave receiving part 100 have equal distances from the two axial end faces of the semi-cylindrical shell 81 respectively, and the axial direction of the semi-cylindrical shell 81 The length L is 1/2 of the wavelength λ of the electromagnetic wave corresponding to the resonance frequency, that is, L=1/2λ.

Please refer to FIG. 11 and FIG. 12 , which show another embodiment of the tuning fork type coupled microwave sensor of the present invention. This embodiment has part of the same structure as the embodiment shown in FIG. 7 and FIG. 8 , so the same components are given the same symbols and their descriptions are omitted. The difference between the present embodiment and the previous embodiment is that the distance between the microwave transmitting part 90 and the microwave receiving part 100 of the present embodiment and one axial end face of the semi-cylindrical shell 81 is equal to that of the other axis of the semi-cylindrical shell 81. Three times the distance to the end face, and the axial length L of the semi-cylindrical shell 81 is equal to the wavelength λ of the electromagnetic wave corresponding to the resonance frequency, that is, L=λ.

Please refer to Fig. 13, which shows the resonant frequency of the microwave resonant cavity when there is no object to be placed between the two insulating covers 82 of the tuning fork type coupling microwave sensor, that is, when there is only air between the two insulating covers 82 2.68GHz. Please refer to Fig. 14, which shows that when objects with different water contents are placed on the insulating cover 82 of the tuning fork type coupling microwave sensor, the variation of the resonant frequency corresponding to each object of the tuning fork type coupling microwave sensor is measured, and the water content The higher the value, the lower the resonance frequency and the lower the amplitude. As mentioned above, since the dielectric coefficient of water is quite high, objects with different water contents have different dielectric coefficients, so that the resonant frequency of the microwave resonant cavity is also different. The curve in the center of the frequency spectrum shown in FIG. 14 is the resonant frequency when there is only air between the two insulating covers 82 , which is 2.68 GHz. The other two curves from the center to the direction of decreasing frequency are respectively the dry object to be tested and the object to be tested with a moisture content of Y%. It can be seen from Figure 14 that the higher the water content of the object, the lower its resonant frequency and amplitude will be.

Before the coupled microwave sensor of the present invention measures the moisture content of the object to be measured, it must be calibrated with a variety of objects with known moisture content to obtain a linear regression curve between the signal value of the coupled microwave sensor and the moisture content of the object. So that when the coupled microwave sensor of the present invention measures an object with unknown water content, it can derive the water content of the object according to the measured resonant frequency.

Please refer to FIG. 15 , which shows an embodiment of the linear regression method for coupling the signal value of the microwave sensor and the moisture content of the object according to the present invention.

Firstly, in step S1, N objects with known moisture content are placed on the scroll-shaped or tuning-fork type coupled microwave sensor of the present invention to measure N corresponding signal values (resonant frequencies). Then go to step S2.

In step S2, a standard value A of the correlation coefficient is set. Then go to step S3.

In step S3, the combination number of n signal values is obtained from the N signal values. Firstly, the maximum value of n can be set as N, and the minimum value is 3. Then go to step S4.

In step S4, the correlation coefficient of each combination is calculated. Then go to step S5.

In step S5, it is compared with the standard value A of the correlation coefficient to determine whether the correlation coefficient of each combination is greater than or equal to the standard value A of the correlation coefficient. If the correlation coefficient of each combination is not greater than or equal to the standard value A of the correlation coefficient, then enter step S6; if the correlation coefficient of each combination is greater than or equal to the standard value A of the correlation coefficient, then enter step S7.

In step S6, decrement n by 1, then return to step S3, obtain the combination number of n-1 signal values among the N signal values, and continue with steps S3, S4 and S5.

In step S7, the maximum value among the correlation coefficients of each combination greater than or equal to the standard value A is taken as the new standard value. Then go to step S8.

In step S8, the optimal linear regression formula is obtained with the optimal correlation coefficient.

If the correlation coefficients of various combinations of n from N to 3 are not greater than or equal to the standard value A, the linear regression formula can also be obtained by taking the combination with the maximum correlation coefficient.

Fig. 16 shows that in the embodiment of N=8, eight objects with known water content are used for calibration, and the combination of water content and signal value in four of them obtains a linear regression formula, and its correlation coefficient R2=0.9935.

The following describes the implementation example of the method of coupling the signal value of the microwave sensor and the linear regression formula of the moisture content of the object in a computer program to embody the algorithm.

First input the moisture content of N items of material, set a sequence B as an empty sequence, and use the while loop to put N items of data into sequence B until the input of -1 means the input is complete.

Place N items of materials with different moisture content on the sensing probe, obtain the corresponding signal values of N items, set sequence C as an empty sequence, and use the while loop to put N items of signal reference values into sequence C until inputting -1 means Input is complete.

Use the built-in function len() to calculate the total number of items in sequence B, and store this calculation result as a variable N.

，其中初始值n=N，並一一列舉出其所有組合

(n=N)。 Set the start value of a for loop D to N, and the end value to 3. After each execution of the loop, D is decremented by 1. In this loop, define a rec recursive function, and use the function rec to calculate the relationship between sequence B and sequence C. All combinations

, where the initial value n=N, and list all its combinations one by one

(n=N).

Set a for loop E in this loop D, the initial value is 0, and the end value is the total number of combinations of the sequence calculated by the rec recursive function. Each time the loop E is executed, it is incremented by 1 to form a double loop, and Use the command from scipy import stats. in loop E to obtain the linear regression formula and its correlation coefficient for each listed combination.

Define the correlation coefficient standard value A, judge whether the correlation coefficient of the combination obtained in loop E is greater than or equal to the correlation coefficient standard value A, if the correlation coefficient of the group is greater than or equal to the correlation coefficient standard value A, then store the correlation coefficient value of the group into variable A , and jump out of the loop to display the execution result. It includes the set of correlation coefficients (variable A) and its linear regression formula.

Define and judge whether the variable F of the maximum correlation coefficient is 0, assuming that there is no search in the loop E that is greater than or equal to the standard value of the correlation coefficient A, then the value of the maximum correlation coefficient in each sequence is stored in the variable F, and the execution result is displayed. It contains the set of correlation coefficients (variable B) and its linear regression formula.

Decrease n by 1, and then return to the aforementioned loop D to obtain the correlation coefficient of each combination again.

Based on the above, the correlation coefficients of each combination are obtained, and combinations with low correlation coefficients are eliminated to avoid environmental or human errors, thereby obtaining a linear regression formula with high accuracy.

The coupled microwave sensor of the present invention excites electromagnetic waves through a special coupling structure, generates a scattered field above the coupled microwave sensor and passes through the object to be measured, and measures the resonant frequency of the microwave resonant cavity, and when the water content of the object increases It will cause the resonant frequency of the microwave resonant cavity to decrease, so that the water content of the object can be measured. At the same time, the signal value of multiple objects with known water content is measured by the coupled microwave sensor, and the combination of the best correlation coefficient is obtained by judging whether the correlation coefficient of each combination of water content and signal value meets the target value , so as to obtain the linear regression formula between the signal value of each coupled microwave sensor and the moisture content of the object.

But what is described above is only a preferred embodiment of the present invention, and should not limit the scope of the present invention with this, that is, all simple equivalent changes and modifications made according to the scope of patent application of the present invention and the contents of the description of the invention , all still belong to the scope covered by the patent of the present invention. In addition, any embodiment or scope of claims of the present invention does not necessarily achieve all the objectives or advantages or features disclosed in the present invention. In addition, the abstract and the title are only used to assist the search of patent documents, and are not used to limit the scope of rights of the present invention. In addition, terms such as "first" and "second" mentioned in this specification or the scope of the patent application are only used to name elements (elements) or to distinguish different embodiments or ranges, and are not used to limit the number of elements. upper or lower limit.

10: bottom wall 20: inner shaft body 21: center 30: outer ring body 31: Gap 40: connector 41: Arc body 42: The first connecting part 43: The second connecting part 50:Microwave feed-in 60: Insulation cover 70: base 80: Semi-cylindrical resonant cavity 81: Semi-cylindrical shell 82: Insulation cover 90:Microwave launcher 100:Microwave receiver 110: Electromagnetic coupling L: axial length S1~S8: steps

FIG. 1 is a perspective view of an embodiment of a scroll-coupled microwave sensor (without an insulating cover). FIG. 2 is a top view of the scroll-coupled microwave sensor of FIG. 1 . FIG. 3 is a perspective view of the vortex coupled microwave sensor in FIG. 1 plus an insulating cover. Fig. 4 is a sectional view along line A-A of Fig. 1 . FIG. 5 is a spectrum diagram of a resonant mode with no object to be measured (only air) above the vortex coupled microwave sensor of FIG. 1 . FIG. 6 is a spectrum diagram of resonance modes of different objects to be measured placed above the vortex coupling microwave sensor in FIG. 1 . FIG. 7 is a perspective view of an embodiment of a tuning fork type coupled microwave sensor. FIG. 8 is a perspective view of the tuning-fork coupled microwave sensor in FIG. 7 with the semi-cylindrical housing removed. FIG. 9 is a side view of the tuning fork type coupled microwave sensor of FIG. 7 . Fig. 10 is a side view of the tuning-fork type coupled microwave sensor in Fig. 9 with the semi-cylindrical casing removed. 11 is a side view of another embodiment of a tuning fork type coupled microwave sensor. Fig. 12 is a side view of the tuning-fork type coupled microwave sensor in Fig. 11 with the semi-cylindrical housing removed. FIG. 13 is a spectrum diagram of the resonance mode of the tuning-fork type coupled microwave sensor of FIG. 7 without side objects (only air). FIG. 14 is a spectrum diagram of the resonant modes of the tuning fork-type coupled microwave sensor in FIG. 7 with different objects to be disposed. FIG. 15 is a flow chart of an embodiment of the method for obtaining the linear regression equation between the signal value of the coupled microwave sensor and the moisture content of the object according to the present invention. FIG. 16 is a schematic diagram of the linear regression equation obtained by the method for obtaining the linear regression equation between the signal value of the coupled microwave sensor and the moisture content of the object in FIG. 15 .

10: bottom wall

20: inner shaft body

21: center

30: outer ring body

31: Gap

40: connector

41: Arc body

42: The first connecting part

43: The second connecting part

50:Microwave feed-in

Claims (5)

A tuning fork-shaped coupled microwave sensor, comprising: a base; A pair of semi-cylindrical resonant cavities are arranged on the base, each semi-cylindrical resonant cavity includes a semi-cylindrical shell and an insulating cover covering the semi-cylindrical shell, the insulating cover of the pair of semi-cylindrical resonant cavities The cover systems are arranged facing each other and are separated by a predetermined distance; A microwave emitting element is arranged in one of the semi-cylindrical resonant cavities; A microwave receiving part is arranged in the other semi-cylindrical resonant cavity, and the microwave emitting part is arranged opposite to the microwave receiving part; and A pair of electromagnetic coupling parts are respectively arranged in the pair of semi-cylindrical resonant cavities, and are vertically arranged with the microwave emitting part and the microwave receiving part respectively. The tuning fork-shaped coupled microwave sensor as described in Claim 1, wherein the pair of electromagnetic coupling elements are respectively arranged close to the insulating cover, there is a distance between the electromagnetic coupling elements and the microwave emitting element, and the electromagnetic coupling elements There is a distance from the microwave receiver. The tuning-fork-shaped coupled microwave sensor as claimed in item 1, wherein the distance from the microwave emitting part to any end face of the semi-cylindrical shell perpendicular to the axial direction is equal to the distance from the microwave receiving part to the semi-cylindrical shell The distance between any end surface perpendicular to the axial direction, the axial length of the semi-cylindrical shell is 1/2 of the wavelength of the electromagnetic wave corresponding to the resonant frequency. The tuning-fork-shaped coupled microwave sensor as described in Claim 1, wherein the distance from the microwave launcher to an end surface perpendicular to the axial direction of the semi-cylindrical shell is the distance from the microwave launcher to the semi-cylindrical shell perpendicular to Three times the distance from the other end face of the axial direction; the distance from the microwave receiving part to the one end face perpendicular to the axial direction of the semi-cylindrical shell is the other end face perpendicular to the axial direction from the microwave receiving part to the semi-cylindrical shell Three times the distance between the end faces, and the axial length of the semi-cylindrical shell is equal to the wavelength of the electromagnetic wave corresponding to the resonant frequency. A method for obtaining a linear regression expression between the signal value of a coupled microwave sensor and the moisture content of an object, comprising: Use the microwave sensor to obtain the signal values of N items with different known moisture contents; Obtain the number of combinations of n signal values among the N signal values; Calculate the correlation coefficient of each combination; Determining whether the correlation coefficients meet the target; If not all correlation coefficients meet the target, obtain the number of combinations of n-1 signal values among the N signal values, and calculate the correlation coefficient of each combination; If all the correlation coefficients meet the target, the combination of the best correlation coefficients is obtained; Calculate the linear regression formula of the signal value with the signal value of the best correlation coefficient combination; Complete the calibration regression.

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