Method and apparatus for estimating permittivity of plastic pellets

Abstract

A method for measuring dielectric constant is disclosed, the method comprising: a step of calculating a scattering coefficient including a reflection coefficient and a transmission coefficient of air, a metal plate, foam, and a pellet; a step of obtaining a normalized measured scattering coefficient by applying time gating to the reflection coefficient and using a normalization formula; a step of calculating an estimated dielectric constant by applying an iterative algorithm that considers a multilayer model; and a step of obtaining the dielectric constant of the pellet by compensating the estimated dielectric constant using the mass fraction of the pellet.

Description

Technology Field

[0001] The present disclosure relates to a method and apparatus for measuring the dielectric constant of plastic pellets, and more specifically, to an apparatus and method for estimating the dielectric constant of a non-uniformed particle-shaped medium using a free-space measurement method. Background Technology

[0003] The utilization of recycled plastics is increasing in the field of microwave engineering. For example, recycled plastics can be used in various applications such as radomes, shielding, microwave lenses, and antenna substrates. However, accurate measurement of the recycled plastic's residue is an essential prerequisite for such applications.

[0004] Measuring permittivity is necessary to determine the electrical properties of various media, such as antennas, radar, and films. Since incorrect permittivity measurements can yield results different from the design intent, a method for accurate measurement is required.

[0005] Conventional free-space measurement techniques utilizing at least two antennas have primarily been used for measuring uniform media, but they have limitations in measuring particulate media such as pellets. In particular, while Trabelsi's study used free-space measurement techniques to measure the moisture content of particulate materials like grains, its application to plastic pellets was limited, and it had limitations in that it did not consider the influence of the medium container.

[0006] In addition, existing studies failed to accurately compensate for the influence of the medium container, and there was a lack of measurement methods that reflected the dielectric constant changes caused by voids between pellets and the characteristics of recycled plastic pellets. The problem to be solved

[0008] The technical objective of the present disclosure is to provide an apparatus and method for estimating permittivity, which measures the permittivity of a non-uniform particle-shaped medium using a free-space measurement method.

[0009] The technical problems to be solved in this disclosure are not limited to those mentioned above, and other technical problems not mentioned will be clearly understood by those skilled in the art to which this disclosure belongs from the description below. means of solving the problem

[0011] According to one aspect of the present disclosure, a method for measuring dielectric constant is disclosed, the method may include the steps of: calculating a scattering coefficient including a reflection coefficient and a transmission coefficient of air, a metal plate, foam, and a pellet; applying time gating to the reflection coefficient and obtaining a normalized measured scattering coefficient using a normalization formula; calculating an estimated dielectric constant by applying an iterative algorithm that considers a multilayer model; and obtaining the dielectric constant of the pellet by compensating the estimated dielectric constant using the mass fraction of the pellet.

[0012] According to one embodiment of the present disclosure, the step of calculating the scattering coefficient may include the step of sequentially calculating the scattering coefficients of the air, the metal plate, the foam, and the pellet using a Vector Network Analyzer (VNA) connected to a plurality of lens horn antennas.

[0013] According to another embodiment of the present disclosure, the time gating may utilize a window function that includes a interval in which a reflected signal appears.

[0014] According to another embodiment of the present disclosure, the normalized measured scattering coefficient can be obtained based on the scattering coefficient of the air, the scattering coefficient of the metal plate, and the reflection coefficient of the sample in which the foam and the pellet are combined.

[0015] According to another embodiment of the present disclosure, an iterative algorithm that considers the multilayer model may set an initial permittivity for the multilayer model in which the air, the metal plate, the foam, and the pellet are stacked, calculate a theoretical scattering coefficient using the initial permittivity, and obtain the estimated permittivity by updating the initial permittivity such that the difference between the theoretical scattering coefficient and the measured scattering coefficient of the multilayer model is less than or equal to a predetermined threshold value.

[0016] According to another embodiment of the present disclosure, the step of updating the initial permittivity may include updating the initial permittivity such that the difference between the transmittance of the theoretical scattering coefficient and the transmittance of the measured scattering coefficient is less than or equal to a predetermined threshold value.

[0017] According to another embodiment of the present disclosure, the reflection coefficient of the theoretical scattering coefficient can be calculated by a recursive function for transverse electric polarization.

[0018] According to another embodiment of the present disclosure, the mass fraction of the pellet may be determined by the mass ratio between the pellet and the solid medium relative to the reference volume of the pellet.

[0019] According to another embodiment of the present disclosure, the step of obtaining the dielectric constant of the pellet may include the step of obtaining the dielectric constant of the pellet with respect to the solid medium by reflecting the mass fraction in the estimated dielectric constant of the multilayer model.

[0020] According to another embodiment of the present disclosure, after the step of obtaining the dielectric constant of the pellet, the method may include the step of measuring the dielectric constant of a specimen fabricated based on the pellet using a waveguide technique and the step of evaluating accuracy by comparing the dielectric constant of the specimen with the dielectric constant of the pellet with respect to a solid medium.

[0021] According to another aspect of the present disclosure, a permittivity estimation device is provided. The permittivity estimation device comprises a memory storing at least one instruction and a processor executing the at least one instruction stored in the memory based on data obtained from the memory. The processor may be controlled to calculate scattering coefficients including reflection coefficients and transmission coefficients of air, a metal plate, foam, and a pellet, to apply time gating to the reflection coefficients and to obtain normalized measured scattering coefficients using a normalization formula, to calculate an estimated permittivity by applying an iterative algorithm that considers a multilayer model, and to obtain the permittivity of the pellet by compensating the estimated permittivity using the mass fraction of the pellet.

[0022] The features briefly summarized above regarding the present disclosure are merely exemplary aspects of the detailed description of the present disclosure that follows and do not limit the scope of the present disclosure. Effects of the invention

[0024] According to the present disclosure, an apparatus and method for estimating dielectric constant can be provided for measuring the dielectric constant of a non-uniform particle-shaped medium using a free-space measurement method.

[0025] In addition, according to the present disclosure, the dielectric properties of a pellet-shaped medium can be characterized more reliably.

[0026] In addition, according to the present disclosure, effective utilization of recycled plastics in microwave applications can be promoted and upcycling can be contributed.

[0027] The technical effects intended to be achieved in this disclosure are not limited to those mentioned above, and other technical effects not mentioned will be clearly understood by those skilled in the art to which this disclosure belongs from the description below. Brief explanation of the drawing

[0029] FIG. 1 is a diagram illustrating an overall system for measuring the permittivity of a pellet using a free-space estimation technique according to one embodiment of the present disclosure. FIG. 2 is a schematic diagram of an apparatus for measuring dielectric constant according to another embodiment of the present disclosure. FIG. 3 is a flowchart illustrating the process of measuring the dielectric constant of a pellet using a free space estimation technique according to another embodiment of the present disclosure. Figure 4 is a diagram illustrating the sequential calculation of scattering coefficients. Figure 5 is a diagram illustrating the removal of unnecessary reflected signals by applying time gating. Figure 6 is a flowchart illustrating the process of calculating the estimated permittivity by applying an iterative algorithm that considers a multilayer model. Figure 7 is a diagram illustrating a multilayer model for calculating the theoretical scattering coefficient. Figures 8a and 8b illustrate the difference between the permittivity measured by the waveguide technique and the permittivity obtained by the free-space measurement technique. Specific details for implementing the invention

[0030] Hereinafter, embodiments of the present disclosure are described in detail with reference to the attached drawings so that those skilled in the art can easily implement them. However, the present disclosure may be embodied in various different forms and is not limited to the embodiments described herein.

[0031] In describing the embodiments of the present disclosure, if it is determined that a detailed description of known configurations or functions could obscure the essence of the present disclosure, such detailed description is omitted. Additionally, parts of the drawings unrelated to the description of the present disclosure have been omitted, and similar parts are denoted by similar reference numerals.

[0032] In the present disclosure, when a component is described as being "connected," "combined," or "joined" with another component, this may include not only a direct connection but also an indirect connection in which another component exists in between. Furthermore, when a component is described as "comprising" or "having" another component, this means that, unless specifically stated otherwise, it does not exclude the other component but may include additional components.

[0033] In the present disclosure, terms such as first, second, etc. are used solely for the purpose of distinguishing one component from another component and do not limit the order or importance of the components unless specifically stated otherwise. Accordingly, within the scope of the present disclosure, a first component in one embodiment may be referred to as a second component in another embodiment, and likewise, a second component in one embodiment may be referred to as a first component in another embodiment.

[0034] In this disclosure, distinct components are intended to clearly describe their respective features and do not imply that the components are separate. That is, multiple components may be integrated to form a single hardware or software unit, or a single component may be distributed to form multiple hardware or software units. Accordingly, such integrated or distributed embodiments are included within the scope of this disclosure, even if not otherwise mentioned.

[0035] In the present disclosure, each of the phrases such as “A or B”, “at least one of A and B”, “at least one of A or B”, “A, B or C”, “at least one of A, B and C”, and “at least one of A, B, C or combination thereof” may include any one of the items listed together in the corresponding phrase, or all possible combinations thereof.

[0036] In the present disclosure, the components described in various embodiments do not necessarily mean essential components, and some may be optional components. Accordingly, embodiments consisting of a subset of the components described in one embodiment are also included within the scope of the present disclosure. Furthermore, embodiments including other components in addition to the components described in various embodiments are also included within the scope of the present disclosure.

[0037] The advantages and features of the present invention and the methods for achieving them will become clear by referring to the embodiments described below in detail together with the accompanying drawings. However, the present invention is not limited to the embodiments presented below but can be implemented in various different forms, and these embodiments are provided merely to ensure that the disclosure of the present invention is complete and to fully inform those skilled in the art of the scope of the invention.

[0038] Hereinafter, an apparatus for estimating dielectric constant according to one embodiment of the present disclosure, which estimates dielectric constant using a measured scattering coefficient with reference to the attached drawings, will be described.

[0039] FIG. 1 is a diagram illustrating an overall system for measuring the permittivity of a pellet using a free-space estimation technique according to one embodiment of the present disclosure.

[0040] Referring to FIG. 1, a permittivity estimation device (120) using a free-space estimation technique may be composed of an estimation unit (100), a mounting unit (not shown), first and second ports (110a, 110b), and a sample (115). Each component is not an essential component and may have additional components or be omitted, and one component may be included in or combined with another component so that a single component can perform multiple functions.

[0041] The estimation unit (100) may mean, for example, a Vector Network Analyzer (VNA), and the VNA may include a Signal Source, a Power Splitter, and a Network Analyzer. The estimation unit (100) may be connected to the first and second ports (110a, 110b) via a phase-stabilized cable. In addition, the estimation unit (100) may be connected to the first and second ports (110a, 110b) via a coaxial waveguide converter. By the means described above, the estimation unit may be connected to the first and second ports (110a, 110b), and the mounting unit may be positioned at a predetermined location between the first and second ports (110a, 110b).

[0042] When measuring the permittivity of a sample (115), if a signal is incident on the sample (115), multiple reflections may occur between the sample (115) and the first and second ports (110a, 110b). As a result, the influence of noise from external signals increases, and errors occur in the measurement of the scattering coefficient. Therefore, to minimize these errors, calibration of the estimation unit (100) and the first and second ports (110a, 110b) may be performed. Specifically, calibration of the cable connecting the estimation unit (100) and the first and second ports (110a, 110b) may be performed, and as an example, the cable may be calibrated using a short-open-load. In addition, the cable may use 2-Port TRL calibration (Trough, Reflection Line Method) through time domain gating, but is not limited thereto. For example, techniques such as TRM (Through, Reflect Match), LRL (Line Reflect Line), and GRL (Gated Reflect Line) can be utilized for cable correction.

[0043] The mounting portion may refer to a configuration that holds the sample (115) and interposes the sample between the first and second ports (110a, 110b). For example, the mounting portion may be designed as a slot structure capable of installing a plate of a predetermined thickness. In addition, the mounting portion may be designed to be larger than each plane (e.g., E-plane and H-plane) of the signal scanned from the first and second ports (110a, 110b).

[0044] The above-mentioned signal may be a transverse electric polarization mode (TE mode) electromagnetic wave, for example, a TE10 mode or a TE01 mode electromagnetic wave. Specifically, in the case of a TE10 mode electromagnetic wave, it may refer to an electromagnetic wave in which there is one electric field peak in the long axis direction and no electric field peak in the short axis direction. On the other hand, in the case of a TE01 mode electromagnetic wave, it may refer to an electromagnetic wave in which there is one electric field peak in the short axis direction and no electric field peak in the long axis direction.

[0045] The first and second ports (110a, 110b) may be composed of antennas, and each antenna may perform both electromagnetic wave input and reception depending on the purpose. For example, each antenna may incident electromagnetic waves toward a sample and may also receive electromagnetic waves reflected from the sample. Each antenna may be a spot-focusing horn lens antenna, and as an example, may be a lens horn focusing antenna. The types of antennas available for use in the present disclosure are not limited thereto.

[0046] The sample (115) may be interposed in the seating portion and may be interposed in a combined form of multiple media rather than a single medium. In addition, the sample (115) according to the present disclosure may include an atmospheric state of an empty space with nothing interposed. For example, the sample (115) may include air, foam, a metal plate, and a medium in the form of pellets in a state with nothing interposed. The foam according to the present disclosure may be designed in a form capable of accommodating the medium in the form of pellets. The medium in the form of pellets may be interposed in a combined state with the foam and may be interposed in a multilayer model form combined with a metal plate, etc. The pellets according to the present disclosure may include, but are not limited to, recycled polypropylene (rPP) or polyethylene (rPE) pellets. In addition, the sample (115) according to the present disclosure may include pellets converted into a solid state. In the following detailed description, in relation to the present disclosure, it may be mentioned that scattering coefficients are measured sequentially for a sample (115), and sequential is not limited to a time-series order but may include all processes of measurement according to a predetermined order.

[0047] FIG. 2 is a schematic diagram of an apparatus for measuring dielectric constant according to another embodiment of the present disclosure.

[0048] Referring to FIG. 2, the estimation unit (100) for measuring permittivity may include a communication unit (102), a memory (104), and a processor (106). Each component is not an essential component and may have additional components or be omitted, and one component may be included in or combined with another component so that a single component can perform multiple functions.

[0049] The communication unit (102) can generate or receive a signal to be injected into the sample. In addition, the communication unit (102) can support mutual communication with other devices. For example, other devices may include all electronic devices capable of network communication with the estimation unit (100) via wired or wireless means, such as user terminals, laptops, and tablet PCs. In the present disclosure, the communication unit (102) may be a communication interface that receives various data and networks (or algorithms) required to measure the dielectric constant of a pellet, and transmits information and networks related to the data for measuring the dielectric constant of the pellet to other devices.

[0050] The memory (104) stores a program and various data for controlling the communication unit (102), and can load the program or read and write data at the request of the processor (106).

[0051] The processor (106) can perform overall control of the estimation unit (100). The processor (106) may be configured to execute applications and instructions stored in memory (104). According to the present disclosure, the processor (106) may perform processing to calculate scattering coefficients including reflection coefficients and transmission coefficients of air, metal plates, foam, and pellets, apply time gating to the reflection coefficients, obtain normalized measured scattering coefficients using a normalization formula, calculate estimated permittivity by applying an iterative algorithm that considers a multilayer model, and obtain the permittivity of the pellet by compensating the estimated permittivity using the mass fraction of the pellet. Additionally, the processor (106) may perform processing to evaluate accuracy by comparing the permittivity of the pellet measured using a waveguide technique with the permittivity of the pellet obtained through a free-space measurement technique. In the present disclosure, the processor (106) may be implemented as a single processing module, for example. As another example, processing according to the above-described matters may be distributed across multiple processing modules, and the processor (106) may collectively refer to the multiple processing modules in this disclosure. Hereinafter, the processor (106) may be abbreviated as the estimation unit (100) or described interchangeably for convenience of explanation.

[0052] Hereinafter, the process of measuring the dielectric constant of a pellet-shaped sample, which is a heterogeneous medium according to another embodiment of the present disclosure, is described with reference to FIG. 3. FIG. 3 is a flowchart illustrating the process of measuring the dielectric constant of a pellet using a free space estimation technique according to yet another embodiment of the present disclosure.

[0053] The measuring unit (100) calculates the scattering coefficient of the sample (S410). Specifically, the measuring unit (100) sequentially calculates the scattering coefficients of air, a metal plate, foam, and pellets, and calculates the scattering coefficient of each sample (115) through a state where nothing is installed in the mounting section, a state where a metal plate is installed in the mounting section, a state where foam is installed in the mounting section, and a state where pellets are placed in the foam.

[0054] Next, the measurement unit (100) obtains a normalized measurement scattering coefficient by applying time gating and using a normalization formula (S420). Time gating can be used to remove unnecessary reflection signals obtained from a sample, and, for example, can partially remove reflection signals through a window function that includes a section where reflection signals appear. When time gating is applied, as an edge effect that distorts at both ends of the frequency of the obtained reflection signal occurs, the measurement unit (100) can extend the frequency measurement range beyond the frequency band of interest.

[0055] When using a free-space estimation technique, a scattering coefficient normalization formula can be used to extract the normalized measured scattering coefficient of the sample (115). It is difficult to extract the measured scattering coefficient of the sample (115) using only the scattering coefficient obtained by applying time-domain gating, and de-embedding must be performed to consider the influence of waves propagating in free space in the measurement environment. Therefore, it is necessary to extract the normalized measured scattering coefficient using a normalization formula. The scattering coefficient may include a reflection coefficient and a transmission coefficient.

[0056] The method of extracting the measured scattering coefficient of the sample (104) using a normalization formula is the scattering coefficient of the reference reflective surface air ( , ), scattering coefficient of metal plate( , propagation constant( , thickness of the metal plate ( and thickness of the sample ( It can be extracted based on. A metal plate according to the present disclosure may be assumed to be an ideal conductor. Additionally, in the present disclosure, the sample in the normalization formula may include a pellet combined with foam, and more specifically, may include a plastic pellet combined with foam.

[0057] Specifically, the normalized measured scattering coefficient of the sample using a normalization equation ( , ) can be extracted through the following mathematical formula.

[0058] [Mathematical Formula 1]

[0059] ,

[0060] represents the reflection coefficient measured by the signal reflected from the sample, and represents the transmittance coefficient measured by the signal transmitted through the sample. Likewise , Each can refer to the reflection coefficient and transmission coefficient measured by signals reflected or transmitted from the air. Each may refer to the reflection coefficient and transmission coefficient measured by the signal reflected or transmitted from the metal plate.

[0061] Next, the measurement unit (100) calculates the estimated permittivity by applying an iterative algorithm that considers the multilayer model (S430). Specifically, the measurement unit (100) sets the initial permittivity for a multilayer model in which air, a metal plate, foam, and pellets are stacked, and can also calculate the theoretical scattering coefficient using the initial permittivity. Next, the measurement unit (100) can obtain the estimated permittivity by updating the initial permittivity so that the difference between the theoretical scattering coefficient and the measured scattering coefficient of the multilayer model is less than or equal to a predetermined threshold value. The process of the measurement unit (100) calculating the estimated permittivity using an iterative algorithm that considers the multilayer model is explained in detail through FIG. 6.

[0062] Next, the measuring unit (100) obtains the dielectric constant of the pellet by compensating for the estimated dielectric constant using the mass fraction (S440). In the case of a pellet-shaped medium, it exists in a state containing air gaps, which occurs due to the structure in which the pellets are stacked individually. The dielectric constant measured in this state may be a composite dielectric constant including not only the pellet itself but also the air gaps. Therefore, the measuring unit (100) according to the present disclosure obtains the mass of the solid medium, which is a solidified pellet, in order to obtain the accurate dielectric constant of the pellet used as a sample (115), and then obtains the intrinsic dielectric constant of the solid state pellet by compensating for the estimated dielectric constant using the mass ratio between the pellets.

[0063] Specifically, the mass fraction according to the present disclosure can be determined as the mass ratio between the solid medium and the reference volume of the pellet. More specifically, the mass fraction can be determined by the following mathematical formula.

[0064] [Mathematical Formula 2]

[0065]

[0066] represents the measured mass of the pellet, and can mean the volume of the pellet as the standard volume. represents the density of the solidified pellet, and and The mass of the solid medium, which is a solidified pellet, by multiplying by ) can be obtained. Next, mass fraction ( ) Mass of the pellet( ) and mass of the solid medium ( ) can be determined by the rain.

[0067] Next, the measuring unit (100) compensates for the estimated permittivity using the mass fraction. Specifically, the measuring unit (100) obtains the permittivity for the solid medium of the pellet by reflecting the mass fraction in the estimated permittivity of the multilayer model.

[0068] As the permittivity is linearly proportional to the filling fraction of the medium, the measuring unit (100) compensates for the estimated permittivity through a linear equation model. Specifically, the measuring unit (100) obtains the permittivity for the solid medium of the pellet by reflecting the mass fraction in the estimated permittivity of the multilayer model using the following mathematical formula.

[0069] [Mathematical Formula 3]

[0070] , ,

[0071] At this time, and Each can represent the real and imaginary parts of the permittivity for a solid medium, which is a solidified pellet. and can represent the real and imaginary parts of the estimated permittivity of the pellet obtained from the multilayer model.

[0072] The estimation unit (100) can calculate the accurate dielectric constant of the solid medium without worrying about the material's properties changing during the solidification process by calculating the dielectric constant of the solid medium based on the dielectric constant in the pellet state through the method described above.

[0073] Next, the estimation unit (100) can evaluate the measurement accuracy by comparing the permittivity of the pellet with the permittivity measured by the waveguide measurement method (S450). Specifically, the estimation unit (100) evaluates the accuracy by comparing the permittivity of a solidified specimen made based on the pellet, obtained by the waveguide technique, with the permittivity of the solid medium.

[0074] The permittivity of the pellet measured by the waveguide measurement method can be calculated using the following mathematical formula. Specifically, the transmittance of the above specimen using the waveguide measurement method ( ) is the permittivity of the specimen ( ) is inserted as a variable and the length of the waveguide ( ) and wavelength of the input signal ( It can be expressed as a function composed of ). Specifically, it can be expressed through the following mathematical formula.

[0075] [Mathematical Formula 6]

[0076]

[0078] In this case, the propagation constant k can be defined by the following mathematical formula.

[0079] [Mathematical Formula 7]

[0080]

[0081] Specifically, Is It means, can mean the propagation constant in free space. may mean a propagation constant in a dielectric region, and in the present disclosure, may mean a propagation constant in a solidified pellet region measured by a waveguide measurement method. can refer to the wavelength of a signal in free space. In addition, the permittivity of the specimen can be derived as a theoretical value through optimization techniques. For example, an optimization function defined as a function can be used to derive the theoretical permittivity of the specimen.

[0082] Specifically, the optimization function is the measured scattering coefficient (estimated and normalized by the signal passing through the specimen) ) and estimated scattering coefficient( It can be defined by ). For example, the optimization function can be defined as the absolute value of the difference between the estimated scattering coefficient and the measured scattering coefficient, and the permittivity value at which the absolute value is minimized can be estimated as the permittivity. The optimization function can be expressed by the following mathematical formula.

[0083] [Mathematical Formula 7]

[0084]

[0085] At this time, represents the respective frequency of the sampled electromagnetic wave, and the optimization function( The permittivity value at which the value of ) is minimized can be estimated as the permittivity.

[0086] Next, the estimation unit (100) can evaluate the accuracy by measuring the relative error or absolute error through a comparison of the permittivity of the specimen obtained by the waveguide technique and the permittivity of the solid medium of the pellet obtained by the free space measurement method.

[0087] Next, the process of sequentially calculating the sample placed in the settling portion is explained through FIG. 4. FIG. 4 is a diagram illustrating the sequential calculation of scattering coefficients.

[0088] Referring to FIG. 4, the estimation unit (100) measures the scattering coefficient of air through a state where nothing is interposed in the mounting unit (AIR in FIG. 4). In addition, the estimation unit (100) can measure the scattering coefficient of each sample (115) through a state where a metal plate is installed in the mounting unit (PEC in FIG. 4), a state where foam is installed in the mounting unit (FOAM in FIG. 4), and a state where foam and pellet are combined (PELLET in FIG. 4). In the present disclosure, the order of measuring the scattering coefficient is not limited to the order shown in FIG. 4 and may vary according to user settings.

[0089] Figure 5 is a diagram illustrating the removal of unnecessary reflected signals by applying time gating.

[0090] FIG. 5 is a graph showing reflection signals for air and a metal plate. Referring to FIG. 5, according to the present disclosure, the estimation unit (100) can remove unnecessary reflection signals by using a window function that includes a section where reflection signals appear. For example, the estimation unit (100) can use a flattop window. The estimation unit (100) can likewise remove unnecessary reflection signals by using a window function in the case of a foam and a sample (115) in which the foam and a pellet are combined.

[0091] Next, through Fig. 6, an iterative algorithm considering multiple models is described. Fig. 6 is a flowchart illustrating the process of calculating the estimated permittivity by applying an iterative algorithm considering a multilayer model.

[0092] Non-uniformities, such as the random stacking of pellets and the flatness of metal plates and foam, can cause errors in permittivity measurements. Furthermore, using reflection coefficients can lead to greater errors in determining permittivity compared to using transmission coefficients. Accordingly, for materials (or systems) with multilayer structures, it is necessary to use multilayer models to clearly predict how electromagnetic waves are reflected and transmitted.

[0093] Referring to FIG. 6, the estimation unit (100) sets an initial permittivity (S510). For example, the estimation unit (100) may set the initial permittivity of the multilayer model to 1+0j. The multilayer model according to the present disclosure may refer to a model in which air, metal plates, foam, and pellets are stacked.

[0094] Next, the estimation unit (100) calculates the theoretical scattering coefficient using the initial permittivity (S520). For example, the estimation unit (100) calculates the theoretical transmission coefficient ( ) can be calculated. Specifically, the theoretical transmittance coefficient using the initial permittivity ( The calculation of ) is the permittivity of the multilayer model ( ) is inserted as a variable and the permeability of the multilayer model( ) and the angle of incidence of the signal incident on the multilayer model ( It can be expressed as a function composed of ). Specifically, it can be calculated through the following mathematical formula.

[0095] [Mathematical Formula 8]

[0096]

[0098] Next, the function It can be calculated recursively through the following mathematical formula.

[0100] [Mathematical Formula 9]

[0101]

[0103] At this time, 1, It can be set to 0. The value of can be derived by the following mathematical formula.

[0104] [Mathematical Formula 10]

[0105]

[0106] At this time, [Equation 9] It can be derived by the following mathematical formula.

[0107] [Mathematical Formula 11]

[0108]

[0109] At this time, represents the angular frequency of a signal incident on a multilayer model, the subscript j represents the medium number of the multilayer model, and N may represent the number of media. According to the present disclosure, N may be set to 3 as configured according to a combination of metal plates, foam, and pellets. represents the angle of incidence of a signal incident on a medium, and can represent the angle of refraction in each medium of a multilayer model. The angle of refraction in each medium can be calculated by Snell's Law. may refer to the thickness of each medium of a multilayer model. In addition, the permeability of a multilayer model according to the present disclosure ( ) can be set to 1. The estimation unit (100) obtains the theoretical scattering coefficient ( Calculate )

[0110] Next, the estimation unit (100) determines whether the difference between the theoretical scattering coefficient and the measured scattering coefficient exceeds a threshold value (S530). For example, the estimation unit (100) determines the threshold value It can be set to this, and may change differently depending on user settings.

[0111] Next, the estimation unit (100) determines the permittivity when the difference between the theoretical scattering coefficient and the measured scattering coefficient is less than or equal to a threshold value ( ) is determined as the estimated permittivity of the pellet (S550). If the difference between the theoretical scattering coefficient and the measured scattering coefficient exceeds a threshold value, the estimation unit (100) updates the initial permittivity and repeats the steps after S520 (S540).

[0112] The estimated dielectric constant of the pellet obtained through the above-described process is a dielectric constant that includes the voids between the pellets, so it requires compensation later, which can be resolved through the S440 process described in Fig. 3.

[0113] Figure 7 is a diagram illustrating a multilayer model for calculating the theoretical scattering coefficient.

[0114] Referring to FIG. 7, a multilayer model according to the present disclosure may be stacked using metal plates, foam, and pellets as media as illustrated in FIG. 7. In addition, the same medium may be stacked multiple times in the multilayer model according to the present disclosure. For example, the multilayer model may be stacked in the order of foam, pellet, foam.

[0115] Figures 8a and 8b illustrate the difference between the permittivity measured by the waveguide technique and the permittivity obtained by the free-space measurement technique.

[0116] Referring to Figures 8a and 8b, it can be seen that the dielectric constant of recycled polyethylene using the waveguide technique (WG-rPE in Figure 8(a)) and the dielectric constant of recycled polyethylene using the free-space measurement technique (FS-rPE in Figure 8(a)) show similar trends. Similarly, it can be seen that the dielectric constant of recycled polypropylene using the waveguide technique (WG-rPP in Figure 8(a)) and the dielectric constant of recycled polypropylene using the free-space measurement technique (FS-rPP in Figure 8(a)) show similar trends. In addition, it can be seen that the loss tangent also shows a relatively small relative error.

[0117] The exemplary methods of the present disclosure described above are expressed as a series of operations for clarity of explanation, but this is not intended to limit the order in which the steps are performed, and if necessary, each step may be performed simultaneously or in a different order. To implement the method according to the present disclosure, additional steps may be included in addition to the steps exemplified, steps excluding some steps and including the remaining steps, or steps excluding some steps and including additional steps.

[0118] The various embodiments of the present disclosure are not intended to list all possible combinations but to describe representative aspects of the present disclosure, and the matters described in the various embodiments may be applied independently or in combination of two or more.

[0119] Furthermore, although the embodiments of the present disclosure have been described by the limited drawings, those skilled in the art can apply various technical modifications and variations based on the above. For example, appropriate results may be achieved even if the components of the described system, structure, device, circuit, etc. are combined or assembled in a form different from the described method, or are replaced or substituted by other components or equivalents. Therefore, other implementations, other embodiments, and equivalents to the claims set forth below are also included in the claims.

[0120] In addition, various embodiments of the present disclosure may be implemented by hardware, firmware, software, or a combination thereof. In the case of implementation by hardware, it may be implemented by one or more ASICs (Application Specific Integrated Circuits), DSPs (Digital Signal Processors), DSPDs (Digital Signal Processing Devices), PLDs (Programmable Logic Devices), FPGAs (Field Programmable Gate Arrays), general processors, controllers, microcontrollers, microprocessors, etc.

[0121] The scope of the present disclosure includes software or machine-executable instructions (e.g., operating system, application, firmware, program, etc.) that enable an operation according to a method of various embodiments to be executed on a device or computer, and a non-transitory computer-readable medium on which such software or instructions, etc. are stored and executable on a device or computer. Explanation of the symbols

[0123] 100 : Estimation part 110a: 1st port 110b: Second port 115 : Sample 120: Permittivity estimation device

Claims

Claim 1 A method for measuring dielectric constant comprises: a step of calculating a scattering coefficient including a reflection coefficient and a transmission coefficient of air, a metal plate, foam, and a pellet; a step of obtaining a normalized measured scattering coefficient by applying time gating to the reflection coefficient and using a normalization formula; a step of calculating an estimated dielectric constant by applying an iterative algorithm that considers a multilayer model; and a step of obtaining the dielectric constant of the pellet by compensating the estimated dielectric constant using the mass fraction of the pellet, wherein the mass fraction of the pellet is determined by the mass ratio between the pellet and the solid medium relative to the reference volume of the pellet. Claim 2 In claim 1, the step of calculating the scattering coefficient comprises the step of sequentially calculating the scattering coefficients of the air, the metal plate, the foam, and the pellet using a Vector Network Analyzer (VNA) connected to a plurality of lens horn antennas. Claim 3 In claim 1, the time gating is a method using a window function that includes a interval in which a reflected signal appears. Claim 4 A method according to claim 1, wherein the normalized measured scattering coefficient is obtained based on the scattering coefficient of the air, the scattering coefficient of the metal plate, and the reflection coefficient of the sample in which the foam and the pellet are combined. Claim 5 In claim 1, the iterative algorithm considering the multilayer model sets an initial permittivity for the multilayer model in which the air, the metal plate, the foam, and the pellet are stacked, calculates a theoretical scattering coefficient using the initial permittivity, and obtains the estimated permittivity by updating the initial permittivity such that the difference between the theoretical scattering coefficient and the measured scattering coefficient of the multilayer model is less than or equal to a predetermined threshold value. Claim 6 In claim 5, the step of updating the initial permittivity comprises updating the initial permittivity such that the difference between the transmittance of the theoretical scattering coefficient and the transmittance of the measured scattering coefficient is less than or equal to a predetermined threshold value. Claim 7 In claim 6, the reflection coefficient of the theoretical scattering coefficient is calculated by a recursive function for transverse electric polarization. Claim 8 delete Claim 9 A method according to claim 1, wherein the step of obtaining the dielectric constant of the pellet comprises the step of obtaining the dielectric constant of the pellet with respect to the solid medium by reflecting the mass fraction in the estimated dielectric constant of the multilayer model. Claim 10 A method according to claim 1, comprising: a step of obtaining the dielectric constant of the pellet, a step of measuring the dielectric constant of a specimen fabricated based on the pellet using a waveguide technique; and a step of evaluating accuracy by comparing the dielectric constant of the specimen with the dielectric constant of the pellet with respect to a solid medium. Claim 11 A dielectric constant measuring device comprises: a memory storing at least one instruction; and a processor executing the at least one instruction stored in the memory based on data obtained from the memory, wherein the processor controls to calculate scattering coefficients including reflection coefficients and transmission coefficients of air, a metal plate, foam, and a pellet, controls to obtain a normalized measured scattering coefficient using a normalization formula in addition to applying time gating to the reflection coefficient, controls to calculate an estimated dielectric constant by applying an iterative algorithm considering a multilayer model, and controls to obtain the dielectric constant of the pellet by compensating the estimated dielectric constant using the mass fraction of the pellet, wherein the mass fraction of the pellet is determined by the mass ratio between the pellet and the solid medium relative to the reference volume of the pellet. Claim 12 In claim 11, the processor is a device that controls a plurality of lens horn antennas to sequentially calculate the scattering coefficients of the air, the metal plate, the foam, and the pellet. Claim 13 In claim 11, the time gating is a device that uses a window function including a interval in which a reflected signal appears. Claim 14 In claim 11, the normalized measured scattering coefficient is obtained based on the scattering coefficient of the air, the scattering coefficient of the metal plate, and the reflection coefficient of the sample in which the foam and the pellet are combined. Claim 15 In claim 11, the iterative algorithm considering the multilayer model sets an initial permittivity for the multilayer model in which the air, the metal plate, the foam, and the pellet are stacked, calculates a theoretical scattering coefficient using the initial permittivity, and obtains the estimated permittivity by updating the initial permittivity so that the difference between the theoretical scattering coefficient and the measured scattering coefficient of the multilayer model is less than or equal to a predetermined threshold value. Claim 16 In claim 15, the processor is a device that updates the initial permittivity such that the difference between the transmittance of the theoretical scattering coefficient and the transmittance of the measured scattering coefficient is less than or equal to a predetermined threshold value. Claim 17 In claim 16, the device wherein the reflection coefficient of the theoretical scattering coefficient is calculated by a recursive function for transverse electric polarization. Claim 18 delete Claim 19 In claim 11, the processor is a device for obtaining the dielectric constant of the solid medium of the pellet by reflecting the mass fraction in the estimated dielectric constant of the multilayer model. Claim 20 In claim 11, the processor is a device that measures the dielectric constant of a specimen made based on the pellet using a waveguide technique and evaluates accuracy by comparing the dielectric constant of the specimen with the dielectric constant of the pellet in a solid medium.

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