CN113484615A - Material dielectric constant broadband test structure and test method thereof - Google Patents

Material dielectric constant broadband test structure and test method thereof Download PDF

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CN113484615A
CN113484615A CN202110861035.4A CN202110861035A CN113484615A CN 113484615 A CN113484615 A CN 113484615A CN 202110861035 A CN202110861035 A CN 202110861035A CN 113484615 A CN113484615 A CN 113484615A
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sample port
circular waveguide
resonant cavity
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CN113484615B (en
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陈付昌
黄学全
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South China University of Technology SCUT
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R27/00—Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
    • G01R27/02—Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant
    • G01R27/26—Measuring inductance or capacitance; Measuring quality factor, e.g. by using the resonance method; Measuring loss factor; Measuring dielectric constants ; Measuring impedance or related variables
    • G01R27/2617—Measuring dielectric properties, e.g. constants
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R27/00—Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
    • G01R27/02—Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant
    • G01R27/26—Measuring inductance or capacitance; Measuring quality factor, e.g. by using the resonance method; Measuring loss factor; Measuring dielectric constants ; Measuring impedance or related variables
    • G01R27/2617—Measuring dielectric properties, e.g. constants
    • G01R27/2635—Sample holders, electrodes or excitation arrangements, e.g. sensors or measuring cells
    • G01R27/2647—Sample holders, electrodes or excitation arrangements, e.g. sensors or measuring cells of coaxial or concentric type, e.g. with the sample in a coaxial line

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Abstract

The invention discloses a material dielectric constant broadband test structure and a test method thereof, which are suitable for measuring complex dielectric constants of low-dielectric constant (less than 10) and low-loss sheet materials and realizing the complex dielectric constant measurement of single-cavity broadband. The test frequency band is 0.7-10GHz, and three working modes are selected: TM010(coverage frequency band is 0.90-1.00GHz), TM220(coverage frequency band is 3.15-3.45GHz), TM460(the coverage frequency band is 9.50-9.70GHz), which respectively corresponds to the three sample ports. During testing, according to the required measuring frequency band, a piece of sheet-shaped material to be tested is inserted into the corresponding sample port, and the other two sample ports are vacant. The invention has the advantages of high precision, simple structure, low processing cost, easy taking and placing of the material to be measured and the like.

Description

Material dielectric constant broadband test structure and test method thereof
Technical Field
The invention relates to the technical field of microwave material testing, in particular to a material dielectric constant broadband testing structure based on a circular waveguide resonant cavity and a testing method thereof.
Background
Based on the superiority of the microwave performance of the sheet dielectric material, the material is widely applied to the fields of military and civil communication at present and is an indispensable basic material of a microwave device; the relative complex dielectric constant and loss tangent of the dielectric material are used as important indexes of qualified materials, and the performance of the microwave device is greatly influenced; with the deep development of 5G communication nowadays, the research and development of a high-precision low-loss microwave data acquisition device for 5G-Sub6GHz application (0.7-10GHz) is in great tendency.
The following investigations are now conducted on the electromagnetic parameter tests:
the microwave performance test method of the dielectric material can be roughly divided into a lumped parameter method and a field method, and the lumped parameter method is low in test precision, so that the field method is mostly applied at present; the field method can be divided into a non-resonance method and a resonance method, wherein in the non-resonance method, the microwave performance of the material is mainly obtained by deducing the impedance of a transmission line, network parameters, the wave velocity in the material and the like, and the method can be used for the electromagnetic parameter test of the material in a wide frequency range; the method of calculating the complex dielectric constant according to the resonant frequency F and the quality factor Q is generally referred to as a resonance method, and includes a resonant cavity perturbation method, a planar circuit resonance method, a mode matching method, a precise field solution method, a finite element method and the like, wherein the resonant cavity perturbation method is widely applied at present due to the advantages of good field symmetry in a resonant cavity, simple structure, high precision and the like. The method used by the invention is a circular waveguide resonant cavity perturbation method.
However, since the lowest mode of the circular waveguide resonant cavity is TM010The radius of the cylindrical cavity is inevitably increased according to a mode resonant frequency calculation formula of the cylindrical cavity, more modes are introduced into the increase of the radius of the cylindrical cavity within the frequency range of 0.7-10GHz, particularly, a working mode and an interference mode are difficult to distinguish in a high frequency range, great test errors are caused to actual tests, and therefore, most of electromagnetic parameter test devices in the current market, which test the frequency range and simultaneously comprise a low frequency (less than 1GHz) and a high frequency (10GHz), are composed of a plurality of resonant cavities, wherein a small resonant cavity is used for high frequency range tests, and a large resonant cavity is used for low frequency range tests, thereby bringing certain challenges in test convenience and cost budget.
In summary, the circular waveguide resonant cavity broadband electromagnetic parameter test still has a certain limitation, and is difficult to adapt to the test requirements of high precision, low cost and high convenience in the current electromagnetic parameter test field.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provide a material dielectric constant broadband test structure based on a circular waveguide resonant cavity and a test method thereof, which can realize convenient taking and placing of a material to be tested and meet the test requirements of high precision, low cost and high convenience.
In order to achieve the purpose, the technical scheme provided by the invention is as follows: the broadband material dielectric constant testing structure based on the circular waveguide resonant cavity comprises two coaxial adapters, the circular waveguide resonant cavity, a first sample port, a second sample port, a third sample port, a first sheet-shaped material to be tested, a second sheet-shaped material to be tested and a third sheet-shaped material to be tested; two coaxial adapters are used for feeding circular waveguide resonant cavity, are connected circular waveguide resonant cavity and vector network analyzer in order to draw scattering parameter and be used for follow-up calculation material parameter, circular waveguide resonant cavity divides there are epicoele and cavity of resorption, two coaxial adapters are fixed respectively on the top cap of epicoele and the bottom of cavity of resorption and the coincidence of axis of ordinates central line, are convenient for encourage mode of operation TM010Mode, working mode two TM220Mode or working mode three TM460Molding; the first sample port, the second sample port and the third sample port are arranged in the upper cavity, the first sheet-shaped material to be tested is loaded on the first sample port, the second sheet-shaped material to be tested is loaded on the second sample port, and the third sheet-shaped material to be tested is loaded on the third sample port.
Furthermore, the circular waveguide resonant cavity is formed by processing metal AL6061, the radius r of the inner cavity of the circular waveguide resonant cavity is 115-125mm, the height h of the inner cavity is 12-15mm, the thickness of the top cover and the bottom cover is 4-5mm, the thickness of the side wall is 5-6mm, and the wall of the inner cavity is plated with silver to increase the quality factor Q of the mode in the inner cavity.
Furthermore, the first sample port is symmetrical along the longitudinal central axis of the circular waveguide resonant cavity, the length is 10-11mm, the width is 3-3.2mm, and the height is 4-5mm of the wall thickness of the top cover; when the test frequency band is 0.90-1.00GHz, the first sheet-shaped material to be tested is directly inserted into the circular waveguide resonant cavity from the first sample port; the first sheet of material to be tested has dimensions of 10 x 3 x 25 mm; the loading position of the first sheet-shaped material to be detected is a working mode TM010Where the electric field of the mode is strongest.
Go toStep one, the wide center line of the second sample port and the wide center line of the first sample port form an angle of 35-37 degrees; the second sample port is symmetrical along the center line of the longitudinal axis of the second sample port, and the distance between the center line of the longitudinal axis of the second sample port and the center line of the longitudinal axis of the circular waveguide resonant cavity is 41-45 mm; the length of the second sample port is 10-11mm, the width is 1.5-1.7mm, and the height is 4-5mm of the wall thickness of the top cover; when the test frequency band is 3.15-3.45GHz, the second sheet-shaped material to be tested is directly inserted into the circular waveguide resonant cavity from the second sample port; the second sheet of material to be tested has dimensions of 10 x 1.5 x 25 mm; the loading position of the second sheet-shaped material to be tested is a working mode II TM220Where the electric field of the mode is strongest.
Further, the wide center line of the third sample port and the wide center line of the first sample port form an angle of 53-55 degrees; the third sample port is symmetrical along the center line of the longitudinal axis of the third sample port, and the distance between the center line of the longitudinal axis of the third sample port and the center line of the longitudinal axis of the circular waveguide resonant cavity is 26-30 mm; the third sample port is 10-11mm long, 1.5-1.7mm wide and 4-5mm high; when the measuring frequency band is 9.50-9.70GHz, the third sheet-shaped material to be measured is directly inserted into the circular waveguide resonant cavity from the third sample port; the loading position of the third flaky material to be tested is a working mode three TM460Where the electric field is strongest.
Further, the positions of the two coaxial adapters are selected according to whether the working mode is excited or not and the coupling strength of the excited working mode; the longitudinal axis center lines of the two coaxial adapters are overlapped; if the circular waveguide resonant cavity is overlooked, the following coordinate system is established: taking the wide center line of the first sample port as an X axis, the long center line as a Y axis and the intersection point of the two axes as an origin, and the point of the center line of the longitudinal axis of the second sample port is positioned in a second quadrant, so that the coordinates of the center line of the longitudinal axis coincided by the two coaxial adapters are (70 mm-50 mm); meanwhile, in order to ensure weak coupling between the circular waveguide resonant cavity and the vector network analyzer, the length of the probes of the two coaxial adapters is 0.8-1 mm.
Furthermore, during actual test, according to the test frequency band, only one piece of sheet-shaped material to be tested needs to be inserted into the corresponding sample port, and the rest two sample ports are vacant.
The invention also provides a test method of the material dielectric constant broadband test structure based on the circular waveguide resonant cavity, which comprises the following steps:
step 1: respectively connecting the two coaxial adapters to any two ports of the vector network analyzer;
step 2: the three sample ports are not provided with any material to be measured, the measurement frequency range is selected, and the vector network analyzer is sequentially calibrated in an open circuit mode, a short circuit mode and a load mode;
and step 3: the three sample ports are not provided with any material to be tested, and the transmission loss S of the port of the vector network analyzer is tested and recorded21(ii) a According to the tested S21Obtaining the resonant frequency F03dB bandwidth up-frequency F1And an upper frequency F of 3dB bandwidth2And according to the following formula:
Figure BDA0003185719600000041
calculating the cavity quality factor Q of the working mode corresponding to the selected test frequency band0；
And 4, step 4: according to the test frequency band, inserting a piece of real part of known relative dielectric constant of epsilon 'into a corresponding sample port'NThe standard sheet sample of (1) testing and recording the transmission loss S of the port of the vector network analyzer21(ii) a According to the tested S21Obtaining the resonant frequency FN(ii) a Is prepared from epsilon'N、FNAnd F from step 30Substituting the following equation (2) to obtain the value of the integral coefficient a:
Figure BDA0003185719600000042
a is called an integral coefficient because the intrinsic expression of a is a quotient of two integrals, see the following formula (3):
Figure BDA0003185719600000043
in the formula, n is a depolarization factor, is related to the shape and size of the material and the direction of an electric field in the material, and can be obtained by looking up a table; vSV is the volume of the flaky material to be measured and the volume of the inner cavity of the circular waveguide resonant cavity respectively; e0The electric field intensity of each position in the front circular waveguide resonant cavity is not loaded with the sheet material to be tested; epsilon'NKnown relative dielectric constant ε of standard sheet samplerThe real part of (a);
and 5: taking out the standard sheet sample in the step 4, inserting a sheet material to be tested into the same sample port, and testing and recording the transmission loss S of the port of the vector network analyzer21(ii) a According to the tested S21Obtaining the resonant frequency FC3dB bandwidth up-frequency FC1And an upper frequency F of 3dB bandwidthC2And according to the following equation (4):
Figure BDA0003185719600000051
calculating the loading quality factor Q of the working mode corresponding to the selected test frequency band after loading the corresponding sheet material to be testedC；
Step 6: f obtained in the above steps 3, 4 and 50、Q0、a、FCAnd QCSubstituting the formula (5), the formula (6) and the formula (7) to obtain the relative dielectric constant epsilon of the sheet material to be measuredrReal part ε', imaginary part ε "and loss tangent tan θ:
Figure BDA0003185719600000052
Figure BDA0003185719600000053
Figure BDA0003185719600000054
compared with the prior art, the invention has the following advantages and beneficial effects:
the invention is suitable for complex dielectric constant test of low dielectric constant (less than 10) and low loss sheet material, realizes complex dielectric constant test of single circular waveguide resonant cavity broadband (0.7-10GHz), and has the advantages of high precision, simple structure, low processing cost and easy taking and placing of the material to be tested.
Drawings
Fig. 1 is a perspective view of a material dielectric constant broadband test structure based on a circular waveguide resonant cavity.
Fig. 2 is a top view of a circular waveguide cavity-based material dielectric constant broadband test structure.
Fig. 3 is a side view of a circular waveguide cavity based material dielectric constant broadband test structure.
FIG. 4 shows the transmission coefficient S after the first sheet-like material to be measured is inserted into the sample at 0.945 to 0.97GHz21And (5) a simulation result graph.
FIG. 5 shows the transmission coefficient S of the second sheet-like material to be measured inserted within 3.30-3.44GHz21And (5) a simulation result graph.
FIG. 6 shows the transmission coefficient S after a third sheet-like material to be measured is inserted at 9.60-9.70GHz21And (5) a simulation result graph.
Detailed Description
The present invention will be described in further detail with reference to examples and drawings, but the present invention is not limited thereto.
Referring to fig. 1 to 3, the present embodiment provides a broadband material dielectric constant testing structure based on a circular waveguide resonant cavity, where the structure includes two coaxial adapters 1, a circular waveguide resonant cavity, a first sample port 201, a second sample port 202, a third sample port 203, a first sheet-like material to be tested 4, a second sheet-like material to be tested 5, and a third sheet-like material to be tested 6; two coaxial adapter 1 are used for the feed to circular waveguide resonant cavity, are connected circular waveguide resonant cavity and vector network analyzer in order to draw scattering parameter and be used for follow-up calculation material parameter, circular waveguide resonant cavity divides there are epicoele 2 and cavity of resorption 3, two coaxial adapter 1 are fixed respectively on the top cap of epicoele 2 and the bottom of cavity of resorption 3 and are indulged and indulgeThe axes being coincident to facilitate excitation of the operating mode-TM010Mode, working mode two TM220Mode or working mode three TM460(ii) a The first sample port 201, the second sample port 202 and the third sample port 203 are arranged in the upper chamber 2, the first sheet-shaped material to be measured 4 is loaded on the first sample port 201, the second sheet-shaped material to be measured 5 is loaded on the second sample port 202, and the third sheet-shaped material to be measured 6 is loaded on the third sample port 203. During actual test, according to the test frequency band, only one piece of sheet-shaped material to be tested is inserted into the corresponding sample port, and the other two sample ports are vacant.
The circular waveguide resonant cavity 2 and the circular waveguide resonant cavity 3 are processed by metal AL6061, the radius r of the inner cavity is 115-125mm (preferably 120mm), the height h of the inner cavity is 12-15mm (preferably 15mm), the thickness of the top cover and the bottom cover is 4-5mm (preferably 4mm), the thickness of the side wall is 5-6mm (preferably 5mm), and the wall of the inner cavity is plated with silver to increase the quality factor Q of the mode in the inner cavity.
The first sample port 201 is symmetrical along the longitudinal central axis of the circular waveguide resonant cavity, the length is 10-11mm (preferably 11mm), the width is 3-3.2mm (preferably 3.2mm), and the height is 4-5mm (preferably 4mm) of the wall thickness of the top cover; when the test frequency band is 0.90-1.00GHz, the first sheet-like material 4 to be tested is directly inserted into the circular waveguide resonant cavity from the first sample port 201; the dimensions of the first sheet of material to be measured 4 are 10 x 3 x 25 mm; the loading position of the first sheet material 4 to be measured is a working mode TM010Where the electric field of the mode is strongest.
The wide center line of the second sample port 202 is 35-37 degrees (preferably 36 degrees) to the wide center line of the first sample port 201; the second sample port 202 is symmetrical along the central line of the longitudinal axis of the second sample port, and the distance between the central line of the longitudinal axis of the second sample port and the central line of the longitudinal axis of the circular waveguide resonant cavity is 41-45mm (preferably 43 mm); the second sample port 202 has a length of 10-11mm (preferably 11mm), a width of 1.5-1.7mm (preferably 1.7mm), and a height of 4-5mm (preferably 4mm) of the wall thickness of the top cover; when the test frequency band is 3.15-3.45GHz, the second sheet material to be tested 5 is directly inserted into the circular waveguide resonant cavity from the second sample port 202; the dimensions of the second sheet of material to be tested 5 are 10 × 1.5 × 25 mm; the loading position of the second sheet-shaped material to be tested 5 is a working mode II TM220Where the electric field of the mode is strongest.
The wide center line of the third sample port 203 is 53-55 degrees (preferably 54 degrees) to the wide center line of the first sample port 201; the third sample port 203 is symmetrical along the center line of the longitudinal axis of the third sample port, and the distance between the center line of the longitudinal axis of the third sample port and the center line of the longitudinal axis of the circular waveguide resonant cavity is 26-30mm (preferably 28 mm); the third sample port 203 is 10-11mm (preferably 11mm) long, 1.5-1.7mm (preferably 1.7mm) wide and 4-5mm (preferably 4mm) high; when the measurement frequency band is 9.50-9.70GHz, the third sheet-shaped material to be measured 6 is directly inserted into the circular waveguide resonant cavity from the third sample port 203; the loading position of the third sheet-shaped material to be tested 6 is a working mode three TM460Where the electric field is strongest.
Selecting the positions of the two coaxial adapters 1 according to whether the working mode is excited or not and the coupling strength of the excited working mode; the longitudinal axis center lines of the two coaxial adapters 1 are overlapped; if the circular waveguide resonant cavity is overlooked, the following coordinate system is established: taking the wide center line of the first sample port 201 as an X axis, the long center line as a Y axis, and the intersection point of the two axes as an origin, and the point of the center line of the longitudinal axis of the second sample port 202 is located in the second quadrant, the coordinate of the center line of the longitudinal axis coincided by the two coaxial adapters 1 is (70mm, -50 mm); meanwhile, in order to ensure weak coupling between the circular waveguide resonant cavity and the vector network analyzer, the length of the probes of the two coaxial adapters 1 is 0.8-1mm (preferably 0.9 mm).
Next, the material dielectric constant broadband test structure based on the circular waveguide resonant cavity is used for carrying out complex dielectric constant test on the first sheet-shaped material to be tested 4.
The testing steps are as follows:
step 1: respectively connecting the two coaxial adapters 1 to any two ports of a vector network analyzer;
step 2: the three sample ports are not provided with any material to be tested, the selected test frequency range is 0.90-1.00GHz, and the vector network analyzer is sequentially subjected to open circuit, short circuit and load calibration;
and step 3: the three sample ports are not provided with any material to be tested, and the transmission loss S of the port of the vector network analyzer is tested and recorded21See S on the right side in fig. 421A curve; root of herbaceous plantAccording to S on the right side in FIG. 421Curve, obtaining resonant frequency F03dB bandwidth up-frequency F1And an upper frequency F of 3dB bandwidth2And according to the following formula:
Figure BDA0003185719600000081
computing operating mode-TM010Cavity quality factor Q of the mold0；
And 4, step 4: a real part of a known relative dielectric constant is epsilon 'is inserted into the first sample port 201'NThe standard sheet sample of (1) testing and recording the transmission loss S of the port of the vector network analyzer21(ii) a According to the tested S21Obtaining the resonant frequency FN(ii) a Is prepared from epsilon'N、FNAnd F from step 30Substituting the following equation (2) to obtain an integral coefficient a1The value of (c):
Figure BDA0003185719600000091
and 5: taking out the standard sheet sample in the step 4, inserting the first sheet material 4 to be tested into the first sample port 201, and testing and recording the transmission loss S of the port of the vector network analyzer21See S on the left side of fig. 421A curve; according to S on the left side of FIG. 421Curve, obtaining resonant frequency FC3dB bandwidth up-frequency FC1And an upper frequency F of 3dB bandwidthC2And according to the following formula (3):
Figure BDA0003185719600000092
after the first flaky sample to be detected 4 is loaded, the working mode-TM is calculated010Loading quality factor Q of dieC；
Step 6: f obtained in the above steps 3, 4 and 50、Q0、a1、FCAnd QCSubstituted into the following formulaThe relative dielectric constant epsilon of the first material to be detected 4 is obtained by the formula (4), the formula (5) and the formula (6)r1Of real part ε'1Imaginary part ε "1And loss tangent tan theta1：
Figure BDA0003185719600000093
Figure BDA0003185719600000094
Figure BDA0003185719600000095
Next, the second sheet-like material to be tested 5 is subjected to complex dielectric constant test by using the material dielectric constant broadband test structure based on the circular waveguide resonant cavity.
The testing steps are as follows:
step 1: respectively connecting the two coaxial adapters 1 to any two ports of a vector network analyzer;
step 2: the three sample ports are not provided with any material to be tested, the selected test frequency range is 3.15-3.45GHz, and the vector network analyzer is sequentially calibrated for 'open circuit', 'short circuit' and 'load';
and step 3: the three sample ports are not provided with any material to be tested, and the transmission loss S of the port of the vector network analyzer is tested and recorded21See S on the right side in fig. 521A curve; according to S on the right side in FIG. 521Curve, obtaining resonant frequency F03dB bandwidth up-frequency F1And an upper frequency F of 3dB bandwidth2And according to the following formula:
Figure BDA0003185719600000101
computing operating mode two TM220Cavity quality factor Q of the mold0；
And 4, step 4: a piece of known real part of relative permittivity ∈ 'is inserted into the second sample port 202'NThe standard sheet sample of (1) testing and recording the transmission loss S of the port of the vector network analyzer21(ii) a According to the tested S21Obtaining the resonant frequency FN(ii) a Is prepared from epsilon'N、FNAnd F from step 30Substituting the following equation (2) to obtain an integral coefficient a2The value of (c):
Figure BDA0003185719600000102
and 5: taking out the standard sheet sample in the step 4, inserting a second sheet material to be tested 5 into the second sample port 202, and testing and recording the transmission loss S of the port of the vector network analyzer21See S on the left side of fig. 521A curve; according to S on the left side of FIG. 521Curve, obtaining resonant frequency FC3dB bandwidth up-frequency FC1And an upper frequency F of 3dB bandwidthC2And according to the following formula (3):
Figure BDA0003185719600000103
working mode II TM after the second sheet-shaped sample 5 to be measured is calculated and loaded220Loading quality factor Q of dieC；
Step 6: f obtained in the above steps 3, 4 and 50、Q0、a2、FCAnd QCSubstituting the following formula (4), formula (5) and formula (6) to obtain the relative dielectric constant epsilon of the second sheet-like material to be measured (5)r2Of real part ε'2Imaginary part ε "2And loss tangent tan theta2：
Figure BDA0003185719600000111
Figure BDA0003185719600000112
Figure BDA0003185719600000113
Next, the third sheet-like material to be tested 6 is subjected to complex dielectric constant test by using the material dielectric constant broadband test structure based on the circular waveguide resonant cavity.
The testing steps are as follows:
step 1: respectively connecting the two coaxial adapters 1 to any two ports of a vector network analyzer;
step 2: the three sample ports are not provided with any material to be tested, the selected test frequency range is 9.50-9.70GHz, and the vector network analyzer is sequentially calibrated for 'open circuit', 'short circuit' and 'load';
and step 3: the three sample ports are not provided with any material to be tested, and the transmission loss S of the port of the vector network analyzer is tested and recorded21See S on the right side in fig. 621A curve; according to S on the right side in FIG. 621Curve, obtaining resonant frequency F03dB bandwidth up-frequency F1And an upper frequency F of 3dB bandwidth2And according to the following formula:
Figure BDA0003185719600000114
computing mode three TM460Cavity quality factor Q of the mold0；
And 4, step 4: a piece of known real part of relative permittivity ∈ 'is inserted into the third sample port 203'NThe standard sheet sample of (1) testing and recording the transmission loss S of the port of the vector network analyzer21(ii) a According to the tested S21Obtaining the resonant frequency FN(ii) a Is prepared from epsilon'N、FNAnd F from step 30Substituting the following equation (2) to obtain an integral coefficient a3The value of (c):
Figure BDA0003185719600000121
and 5: taking out the standard sheet sample in the step 4, inserting the second sheet material to be tested 6 into the third sample port 203, and testing and recording the transmission loss S of the port of the vector network analyzer21See S on the left side of fig. 621A curve; according to S on the left side of FIG. 621Curve, obtaining resonant frequency FC3dB bandwidth up-frequency FC1And an upper frequency F of 3dB bandwidthC2And according to the following formula (3):
Figure BDA0003185719600000122
after the third flaky sample to be tested 6 is loaded, the working mode is calculated to be three TM460Loading quality factor Q of dieC；
Step 6: f obtained in the above steps 3, 4 and 50、Q0、a3、FCAnd QCThe relative dielectric constant ε of the third sheet-like material to be measured 6 is obtained by substituting the following equations (4), (5) and (6)r3Of real part ε'3Imaginary part ε "3And loss tangent tan theta3：
Figure BDA0003185719600000123
Figure BDA0003185719600000124
Figure BDA0003185719600000125
The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such changes, modifications, substitutions, combinations, and simplifications are intended to be included in the scope of the present invention.

Claims (8)

1. A material dielectric constant broadband test structure based on a circular waveguide resonant cavity is characterized in that: the device comprises two coaxial adapters (1), a circular waveguide resonant cavity, a first sample port (201), a second sample port (202), a third sample port (203), a first flaky material to be detected (4), a second flaky material to be detected (5) and a third flaky material to be detected (6); two coaxial adapter (1) are used for feeding to circular waveguide resonant cavity, are connected circular waveguide resonant cavity and vector network analyzer in order to draw scattering parameter and be used for follow-up calculation material parameter, circular waveguide resonant cavity divides there are epicoele (2) and lower chamber (3), two coaxial adapter (1) are fixed respectively on the top cap of epicoele (2) and the bottom of lower chamber (3) and the coincidence of axis of ordinates central line, are convenient for encourage mode of operation TM010Mode, working mode two TM220Mode or working mode three TM460Molding; the first sample port (201), the second sample port (202) and the third sample port (203) are arranged in the upper cavity (2), the first sheet-shaped material to be measured (4) is loaded on the first sample port (201), the second sheet-shaped material to be measured (5) is loaded on the second sample port (202), and the third sheet-shaped material to be measured (6) is loaded on the third sample port (203).
2. The broadband test structure for the dielectric constant of the material based on the circular waveguide resonant cavity according to claim 1, wherein: the circular waveguide resonant cavity is formed by processing metal AL6061, the radius r of an inner cavity of the circular waveguide resonant cavity is 115-125mm, the height h of the inner cavity is 12-15mm, the thickness of a top cover and a bottom cover is 4-5mm, the thickness of a side wall is 5-6mm, and the wall of the inner cavity is plated with silver to increase the quality factor Q of an inner cavity mode.
3. The broadband test structure for the dielectric constant of the material based on the circular waveguide resonant cavity according to claim 1, wherein: the first sample port (201) is symmetrical along the longitudinal central axis of the circular waveguide resonant cavity, the length is 10-11mm, the width is 3-3.2mm, and the height is 4-5mm of the wall thickness of the top cover; when the test frequency band is 0.90-1.00GHz, the first frequency band is set to be the first frequency bandThe flaky material to be detected (4) is directly inserted into the circular waveguide resonant cavity from the first sample port (201); the first sheet-like material to be measured (4) has dimensions of 10 x 3 x 25 mm; the loading position of the first sheet-shaped material to be detected (4) is a working mode TM010Where the electric field of the mode is strongest.
4. The broadband test structure for the dielectric constant of the material based on the circular waveguide resonant cavity according to claim 1, wherein: the wide center line of the second sample port (202) and the wide center line of the first sample port (201) form an angle of 35-37 degrees; the second sample port (202) is symmetrical along the center line of the longitudinal axis of the second sample port, and the distance between the center line of the longitudinal axis of the second sample port and the center line of the longitudinal axis of the circular waveguide resonant cavity is 41-45 mm; the length of the second sample port (202) is 10-11mm, the width is 1.5-1.7mm, and the height is 4-5mm of the wall thickness of the top cover; when the test frequency band is 3.15-3.45GHz, the second sheet-shaped material to be tested (5) is directly inserted into the circular waveguide resonant cavity from the second sample port (202); the second sheet of material to be tested (5) has dimensions of 10 x 1.5 x 25 mm; the loading position of the second sheet-shaped material to be tested (5) is a working mode II TM220Where the electric field of the mode is strongest.
5. The broadband test structure for the dielectric constant of the material based on the circular waveguide resonant cavity according to claim 1, wherein: the width center line of the third sample port (203) and the width center line of the first sample port (201) form an angle of 53-55 degrees; the third sample port (203) is symmetrical along the center line of the longitudinal axis of the third sample port, and the distance between the center line of the longitudinal axis of the third sample port and the center line of the longitudinal axis of the circular waveguide resonant cavity is 26-30 mm; the third sample port (203) is 10-11mm long, 1.5-1.7mm wide and 4-5mm high; when the measuring frequency band is 9.50-9.70GHz, the third sheet-shaped material to be measured (6) is directly inserted into the circular waveguide resonant cavity from the third sample port (203); the loading position of the third sheet-shaped material to be tested (6) is a working mode three TM460Where the electric field of the mode is strongest.
6. The broadband test structure for the dielectric constant of the material based on the circular waveguide resonant cavity according to claim 1, wherein: the positions of the two coaxial adapters (1) are selected according to whether the working mode is excited or not and the coupling strength of the excited working mode; the longitudinal axis center lines of the two coaxial adapters (1) are overlapped; if the circular waveguide resonant cavity is overlooked, the following coordinate system is established: taking the wide center line of the first sample port (201) as an X axis, the long center line as a Y axis and the intersection point of the two axes as an origin, and the point of the center line of the longitudinal axis of the second sample port (202) is positioned in a second quadrant, so that the coordinates of the center line of the longitudinal axis coincided by the two coaxial adapters (1) are (70 mm-50 mm); meanwhile, in order to ensure weak coupling between the circular waveguide resonant cavity and the vector network analyzer, the probe lengths of the two coaxial adapters (1) are 0.8-1 mm.
7. The broadband test structure for the dielectric constant of the material based on the circular waveguide resonant cavity according to claim 1, wherein: during actual test, according to the test frequency band, only one piece of sheet-shaped material to be tested is inserted into the corresponding sample port, and the other two sample ports are vacant.
8. The method for testing the broadband dielectric constant test structure of the material based on the circular waveguide resonant cavity of any one of claims 1 to 7, characterized by comprising the following steps:
step 1: respectively connecting the two coaxial adapters (1) to any two ports of a vector network analyzer;
step 2: the three sample ports are not provided with any material to be measured, the measurement frequency range is selected, and the vector network analyzer is sequentially calibrated in an open circuit mode, a short circuit mode and a load mode;
and step 3: the three sample ports are not provided with any material to be tested, and the transmission loss S of the port of the vector network analyzer is tested and recorded21(ii) a According to the tested S21Obtaining the resonant frequency F03dB bandwidth up-frequency F1And an upper frequency F of 3dB bandwidth2And according to the following formula:
Figure FDA0003185719590000031
calculate outCavity quality factor Q of operating mode corresponding to selected test frequency band0；
And 4, step 4: according to the test frequency band, inserting a piece of real part of known relative dielectric constant of epsilon 'into a corresponding sample port'NThe standard sheet sample of (1) testing and recording the transmission loss S of the port of the vector network analyzer21(ii) a According to the tested S21Obtaining the resonant frequency FN(ii) a Is prepared from epsilon'N、FNAnd F from step 30Substituting the following equation (2) to obtain the value of the integral coefficient a:
Figure FDA0003185719590000032
a is called an integral coefficient because the intrinsic expression of a is a quotient of two integrals, see the following formula (3):
Figure FDA0003185719590000041
in the formula, n is a depolarization factor, is related to the shape and size of the material and the direction of an electric field in the material, and can be obtained by looking up a table; vSV is the volume of the flaky material to be measured and the volume of the inner cavity of the circular waveguide resonant cavity respectively; e0The electric field intensity of each position in the front circular waveguide resonant cavity is not loaded with the sheet material to be tested; epsilon'NKnown relative dielectric constant ε of standard sheet samplerThe real part of (a);
and 5: taking out the standard sheet sample in the step 4, inserting a sheet material to be tested into the same sample port, and testing and recording the transmission loss S of the port of the vector network analyzer21(ii) a According to the tested S21Obtaining the resonant frequency FC3dB bandwidth up-frequency FC1And an upper frequency F of 3dB bandwidthC2And according to the following equation (4):
Figure FDA0003185719590000042
calculating the loading quality factor Q of the working mode corresponding to the selected test frequency band after loading the corresponding sheet material to be testedC；
Step 6: f obtained in the above steps 3, 4 and 50、Q0、a、FCAnd QCSubstituting the formula (5), the formula (6) and the formula (7) to obtain the relative dielectric constant epsilon of the sheet material to be measuredrReal part ε', imaginary part ε "and loss tangent tan θ:
Figure FDA0003185719590000043
Figure FDA0003185719590000044
Figure FDA0003185719590000045
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