TWI550282B - Dielectric constant measurement method and apparatus - Google Patents

Description

Dielectric constant quantity measurement method and dielectric constant quantity measuring device

The invention relates to a measuring method and device, and in particular to a dielectric constant quantity measuring method and a dielectric constant quantity measuring device which are measured by using a coaxial signal line.

Parallel plate technology has been applied in many fields. For example, in a microwave imaging system, a microwave signal is transmitted to an object by a flat panel, and a microwave signal penetrating the object is received and measured through another flat panel, and then the shape of the object or the object is reconstructed by calculating a scattering parameter. The dielectric constant distribution. However, prior to the measurement of the object using conventional parallel plates, the standard calibration samples are first measured using conventional parallel plates and the parameters of the measurement system are corrected based on the results of the measurements. In addition, conventional methods for conducting dielectric constant measurements using parallel plates are only applicable in environments where the electromagnetic wave frequency is below 1 GHz, and only a single frequency can be used to measure the object in the same operational step. For some high frequency components, their dielectric constant and conductivity have frequency dependence. If the conventional parallel plate is used to measure these high frequency components, the measurement results may have a large error and cause no reference value.

It is an object of the present invention to provide a dielectric constant quantity measuring method and a dielectric constant quantity measuring apparatus which are applicable to measurement of dielectric constant and electrical conductivity of a high frequency component and which can increase the accuracy of measurement. In addition, the dielectric constant quantity measuring method and the dielectric constant quantity measuring apparatus of the present invention do not need to perform parameter correction in advance before performing the measuring step, thereby increasing the convenience of operation and saving hardware cost and time.

According to the above object of the present invention, a dielectric constant quantity measurement method is provided. The dielectric constant quantity measurement method includes the following steps: measuring a first test object using a coaxial signal line to obtain a first load impedance of the first test object; The second test object is measured by using a coaxial signal line to obtain a second load impedance of the second test object, wherein the first test object and the second test object are composed of the same material, and the first test object and the second test object respectively Having a first thickness and a second thickness, and a difference between the first thickness and the second thickness is between 0.1 mm and 100 mm; dividing the first load impedance and the second load impedance by using a processor to obtain the first a propagation constant of the test object and the second test object; and determining a dielectric constant and a conductivity of the first test object and the second test object by a propagation constant.

According to an embodiment of the invention, the first test object and the second test object have a surface flatness of less than or equal to 0.1 mm.

According to still another embodiment of the present invention, the first thickness and the second thickness are between 0.1 mm and 100 mm.

According to still another embodiment of the present invention, the propagation constant is a complex number, and the dielectric constant and the conductivity are respectively obtained from a phase constant and an attenuation constant of a propagation constant.

According to still another embodiment of the present invention, the first load impedance and the second load impedance are obtained by subtracting a characteristic impedance and a propagation constant of the coaxial signal line.

According to still another embodiment of the present invention, the coaxial signal line performs open measurement on the first test object and the second test object.

According to the above object of the present invention, a dielectric constant quantity measuring device is further provided, which comprises a coaxial signal line and a processing module. The coaxial signal line has a first end and a second end. The first end of the coaxial signal line is configured to contact the first test object and the second test object to perform individual measurement on the first test object and the second test object, thereby obtaining a first load impedance of the first test object and a second a second load impedance of the test object, wherein the first test object and the second test object are composed of the same material, the first test object and the second test object respectively have a first thickness and a second thickness, and the first thickness and the first thickness The difference in thickness is between 0.1 mm and 100 mm. The processing module is coupled to the second end of the coaxial signal line for dividing the first load impedance and the second load impedance to obtain propagation constants of the first test object and the second test object, and by propagating The constant determines the dielectric constant and conductivity of the first test object and the second test object.

According to an embodiment of the invention, the contact between the coaxial signal line and the first test object and the coaxial signal line and the second test object is an open contact.

According to still another embodiment of the present invention, the characteristic impedance of the coaxial signal line is between 10 ohms and 250 ohms.

In accordance with still another embodiment of the present invention, the coaxial signal line includes a housing conductor, a dielectric, and a center conductor. The outer casing conductor and the center conductor comprise gold, silver, copper, aluminum, tin, nickel or an alloy, and the dielectric comprises a ceramic material, Glass fiber material, hydrocarbon material, Teflon material, Teflon fiberglass material or Teflon ceramic material.

100‧‧‧Dielectric constant measuring device

110‧‧‧ coaxial signal line

110A‧‧‧ first end

110B‧‧‧second end

120‧‧‧Processing module

210‧‧‧First test object

220‧‧‧Second test article

300‧‧‧Dielectric constant measurement method

310, 320, 330, 340‧ ‧ steps

T1, T2‧‧‧ thickness

For a more complete understanding of the embodiments and the advantages thereof, reference is made to the following description in conjunction with the drawings in which: FIG. 1 is a schematic diagram showing a dielectric constant quantity measuring device according to some embodiments of the present invention; 2A] and [Fig. 2B] are schematic views showing the measurement of the test object using the dielectric constant quantity measuring device of Fig. 1; and Fig. 3 is a diagram showing the dielectric constant quantity measuring method according to some embodiments of the present invention. Flow chart.

Please refer to FIG. 1. FIG. 1 is a schematic diagram of a dielectric constant measurement device 100 according to an embodiment of the invention. The dielectric constant measurement device 100 includes a coaxial signal line 110 and a processing module 120. The coaxial signal line 110 has a first end 110A and a second end 110B. The first end 110A is for contacting the test object, and the second end 110B is coupled to the processing module 120. The coaxial signal line 110 is sequentially ordered from the inside to the outer casing conductor, the dielectric and the center conductor, wherein the outer casing conductor and the center conductor may comprise gold, silver, copper, aluminum, tin, nickel, alloy or the like. The dielectric material may comprise ceramic material, fiberglass material, hydrocarbon material, Teflon material, Teflon fiberglass material, Teflon ceramic material or other similar dielectric materials. In addition, the characteristic impedance of the coaxial signal line 110 is preferably between 10 ohms and 250 ohms. Processing module 120 provides an interface for coupling the second end 110B of the coaxial signal line 110. The processing module 120 may be a device having an arithmetic function, such as a personal computer or a laptop computer, but is not limited thereto.

Please refer to FIG. 2A and FIG. 2B . FIG. 2A and FIG. 2B are schematic diagrams showing the measurement of the first test object 210 and the second test object 220 by using the dielectric constant measurement device 100, respectively. The first test object 210 and the second test object 220 are composed of the same material, which may be solid, semi-solid or liquid, etc., but are not limited thereto. The dielectric constant of the test material (which constitutes the first test object 210 and the second test object 220) is preferably between 1 and 80, and the conductivity of the test material is preferably between ¹ Sm ^-1 and 40 Sm ^-1 . The surface flatness of the first test object 210 and the second test object 220 is preferably less than or equal to 0.1 mm, so that the dielectric constant measurement device 100 can accurately measure the first test object 210 and the second test object 220. Measurement. In addition, the first test object 210 and the second test object 220 have thicknesses T1 and T2, respectively, wherein the thicknesses T1 and T2 are preferably between 0.1 mm and 100 mm, and the difference between the thicknesses T1 and T2 is preferably between 0.1 mm and 100. Between millimeters.

In order to obtain the dielectric constant and conductivity of the test material, the first end 110A of the coaxial signal line 110 is first contacted with the first test object 210, as shown in FIG. 2A. The coaxial signal line 110 measures the first test object 210, and subtracts the characteristic impedance and propagation constant of the coaxial signal line 110 from the measured value to obtain the load impedance of the first test object 210. The load impedance YL _{1 of the} first test object 210 is as shown in the formula (1): Where r1 is the diameter of the center conductor of the coaxial signal line 110, r2 is the outer diameter of the dielectric of the coaxial signal line 110, ε _d is the dielectric constant of the first test object 210, and γ _d is the first test object 210 The propagation constant is and T1 is the thickness of the first test object 210.

Next, the first test object 210 is removed, and the first end 110A of the coaxial signal line 110 is further contacted with the second test object 220, as shown in FIG. 2B. The coaxial signal line 110 measures the second test object 220, and subtracts the characteristic impedance and the propagation constant of the coaxial signal line 110 from the measured value to obtain the load impedance of the second test object 220. Similarly, the load impedance YL _{2 of the} second test object 220 is as shown in the formula (2): Where T2 is the thickness of the second test object 220.

After obtaining the first test was _a load impedance YL 210 and the second test load impedance 220 YL _2, then the processing module 120 to the load impedance and the load impedance YL ₁ YL ₂ division. Dividing the formula (1) and the formula (2), the formula (3) can be obtained as follows: Since the load impedance YL ₁ , the load impedance YL ₂ , the thickness T1 , and the thickness T2 are known, the values of the load impedance YL ₁ , the load impedance YL ₂ , the thickness T1 , and the thickness T2 are substituted into the equation (3) and calculated. The propagation constant γ _d of the test substance is obtained.

The propagation constant γ _d of the test substance is a complex number, which can be expressed by the formula (4): γ _d = α _d + jβ _d , (4) wherein α _d and β _d are both real numbers. α _d represents the attenuation constant of the propagation constant γ _d , and β _d represents the phase constant of the propagation constant γ _d . By substituting the phase constant β _d into the equation (5), the dielectric constant ε _{d of the} test substance can be obtained: Where λ ₀ is the wavelength of the electromagnetic wave signal emitted by the coaxial signal line 110 in a vacuum. After obtaining the dielectric constant ε _d , the dielectric constant ε _d and the attenuation constant α _{d are then} substituted into the formula (6) to obtain the conductivity σ of the test substance: Where f is the frequency of the electromagnetic wave signal emitted by the coaxial signal line 110, and ε ₀ is the vacuum permittivity.

It should be noted that, in the embodiment illustrated in FIG. 2A and FIG. 2B, the contact of the coaxial signal line 110 with the first test object 210 and the contact of the coaxial signal line 110 with the second test object 220 are open-circuit (open-circuit). )contact. In other words, the coaxial signal line 110 performs an open circuit measurement on the first test object 210 and the second test object 220.

Please refer to FIG. 3 , which illustrates a flow chart of using the dielectric constant measurement method 300 . The dielectric constant measurement method 300 is applicable to the dielectric constant measurement device 100 or other similar measurement device as shown in FIG. In the dielectric constant measurement method 300, first step 310 is performed to measure the first test object using a coaxial signal line to obtain a load impedance of the first test object. In some embodiments, the load impedance of the first test object can be obtained by subtracting the measured value from the characteristic impedance and propagation constant of the coaxial signal line.

Next, in step 320, the second test object is measured using a coaxial signal line to obtain a second load impedance of the second test object. In some embodiments, the load impedance of the second test object can be obtained by subtracting the measured value from the characteristic impedance and propagation constant of the coaxial signal line.

Then, in step 330, the first load impedance and the second load impedance are divided by the processor to obtain propagation constants of the first test object and the second test object. The processor uses the equation (3) to divide the first load impedance and the second load impedance to obtain propagation constants of the first test object and the second test object, and the description of the equation (3) refers to the previous paragraph, This will not go into details.

Finally, step 340 is performed to determine the dielectric constant and conductivity of the first test object and the second test object by propagation constants. The processor uses the equations (5) and (6) to calculate the phase constant and the decay constant of the propagation constant to obtain the dielectric constant and conductivity of the first test object and the second test object, and the equation (5) and the equation Please refer to the previous paragraph for the description of (6), and I will not repeat them here.

It should be noted that the first test substance and the second test substance are composed of the same material, which may be solid, semi-solid or liquid, etc., but is not limited thereto. The dielectric constant of the first test object and the second test object is preferably between 1 and 80, and the conductivity of the first test object and the second test object is preferably between ¹ Sm ^-1 and 40 Sm ^-1 , and The surface flatness of the first test object 210 and the second test object is preferably less than or equal to 0.1 mm. Further, the thickness of the first test object and the second test object is preferably between 0.1 mm and 100 mm, and the difference in thickness between the first test object and the second test object is preferably between 0.1 mm and 100 mm.

The invention is characterized in that the high-frequency characteristics of the material are calculated by measuring two highly different test materials composed of the same material through the coaxial signal line, so the invention can be widely applied to various communication industries and high-frequency materials industries. And the biomedical industry. For example, the application of the present invention to a microwave imaging system can confirm the correctness of the dielectric constant and conductivity of a standard microwave prosthesis; the application of the present invention to the communication industry can confirm the correct dielectric constant of the carrier substrate. The invention can be applied to the electronics industry to confirm the correctness of the dielectric constant of the film; the application of the present invention to the high-frequency material industry can confirm the dielectric constant of the newly formulated substrate. In addition, the dielectric constant quantity measuring method and the dielectric constant quantity measuring apparatus of the present invention do not need to perform parameter correction in advance before performing the measuring step, thereby increasing the convenience of operation and saving hardware cost and time.

Although the present invention has been disclosed in the above embodiments, it is not intended to limit the present invention, and any one of ordinary skill in the art can make some changes and refinements without departing from the spirit and scope of the present invention. The scope of the invention is defined by the scope of the appended claims.

300‧‧‧Dielectric constant measurement method

310, 320, 330, 340‧ ‧ steps

Claims (10)

A dielectric constant measurement method includes: measuring a first test object by using a coaxial signal line to obtain a first load impedance of the first test object; and measuring a second test object by using the coaxial signal line, Obtaining a second load impedance of the second test object, wherein the first test object and the second test object are composed of the same material, and the first test object and the second test object respectively have a first thickness And a second thickness, and the difference between the first thickness and the second thickness is between 0.1 mm and 100 mm; dividing the first load impedance and the second load impedance by using a processor to obtain a propagation constant of one of the first test object and the second test object; and determining a dielectric constant and a conductivity of the first test object and the second test object by the propagation constant. The dielectric constant measurement method according to claim 1, wherein one of the first test object and the second test object has a surface flatness of less than or equal to 0.1 mm. The dielectric constant measurement method according to claim 1, wherein the first thickness and the second thickness are between 0.1 mm and 100 mm. The dielectric constant quantity measuring method according to claim 1, wherein the propagation constant is a complex number, and the dielectric constant and the guiding The electrical rates are respectively obtained from one of the propagation constants and a decay constant. The dielectric constant quantity measuring method according to claim 1, wherein the first load impedance and the second load impedance are obtained by subtracting one characteristic impedance and a propagation constant of the coaxial signal line. The dielectric constant measurement method according to claim 1, wherein the coaxial signal line performs an open-circuit measurement on the first test object and the second test object. A dielectric constant measurement device, comprising: a coaxial signal line having a first end and a second end, wherein the first end is configured to contact the first test object and the second test object to Individually measuring a test object and the second test object to obtain a first load impedance of the first test object and a second load impedance of the second test object, wherein the first test object and the second test object The test object is composed of the same material, the first test object and the second test object respectively have a first thickness and a second thickness, and the difference between the first thickness and the second thickness is between 0.1 mm and 100. Between the millimeters; a processing module coupled to the second end of the coaxial signal line, the processing module is configured to divide the first load impedance and the second load impedance to obtain the first test And a propagation constant of one of the second test object, and determining a dielectric constant and a conductivity of the first test object and the second test object by the propagation constant. The dielectric constant measuring device of claim 7, wherein the coaxial signal line and the first test object and the coaxial signal line are in open contact with the second test object. The dielectric constant measuring device according to claim 7, wherein one of the coaxial signal lines has a characteristic impedance between 10 ohms and 250 ohms. The dielectric constant measuring device according to claim 7, wherein the coaxial signal line comprises a casing conductor, a dielectric and a center conductor, and the casing conductor and the center conductor comprise gold, silver, copper, Aluminum, tin, nickel or alloy, and the dielectric comprises a ceramic material, a glass fiber material, a hydrocarbon material, a Teflon material, a Teflon glass fiber material or a Teflon ceramic material.