阅读说明：本技术 平面介质介电常数宽频带测试结构及其测试方法 (Planar dielectric constant broadband test structure and test method thereof ) 是由 褚庆昕 时琴 于 2021-08-05 设计创作，主要内容包括：本发明公开了一种基于圆柱腔的平面介质介电常数宽频带测试结构及其测试方法,包括圆柱腔和两个磁耦合环；圆柱腔的下部分底面中心设有第一矩形槽,其上部分顶面中心设有第二矩形槽,两个矩形槽共同构成用于放置平面介质的矩形安装槽,圆柱腔下部分的侧壁上开有两个对称的输入通孔,安装上两个磁耦合环后,两个磁耦合环和两个输入通孔构成两个输入端口,该两个输入端口能够对圆柱腔中相应的模式进行激励；圆柱腔上部分顶面开有多条分布在径向上的缝,用于对杂模进行干扰,使杂模无法激励,每条缝的两侧均形成有长条形槽,用于放置吸波材料,使能量辐射到圆柱腔外。本发明可有效测量低频段宽带,计算结果准确。(The invention discloses a planar dielectric constant broadband test structure based on a cylindrical cavity and a test method thereof, wherein the test structure comprises the cylindrical cavity and two magnetic coupling rings; the center of the bottom surface of the lower part of the cylindrical cavity is provided with a first rectangular groove, the center of the top surface of the upper part of the cylindrical cavity is provided with a second rectangular groove, the two rectangular grooves jointly form a rectangular mounting groove for placing a planar medium, the side wall of the lower part of the cylindrical cavity is provided with two symmetrical input through holes, after the two magnetic coupling rings are mounted, the two magnetic coupling rings and the two input through holes form two input ports, and the two input ports can excite corresponding modes in the cylindrical cavity; the top surface of the upper part of the cylindrical cavity is provided with a plurality of radially distributed seams for disturbing the miscellaneous modes and leading the miscellaneous modes to be incapable of being excited, and two sides of each seam are respectively provided with a strip-shaped groove for placing wave-absorbing materials and leading the energy to radiate outside the cylindrical cavity. The invention can effectively measure the low-frequency band broadband and has accurate calculation result.)

1. Planar dielectric constant broadband test structure based on cylinder chamber, its characterized in that: the test structure comprises a cylindrical cavity and two magnetic coupling rings; the cylindrical cavity is formed by assembling an upper part and a lower part, a first rectangular groove is formed in the center of the bottom surface of the lower part of the cylindrical cavity, a second rectangular groove is formed in the center of the top surface of the upper part of the cylindrical cavity, the two rectangular grooves jointly form a rectangular mounting groove for placing a plane medium, and the plane medium is inserted into the rectangular mounting groove for fixing during testing; the side wall of the lower part of the cylindrical cavity is provided with two symmetrical input through holes, the two input through holes correspond to two magnetic coupling rings, namely one input through hole is used for installing one magnetic coupling ring, after the two magnetic coupling rings are installed, the two magnetic coupling rings and the two input through holes form two input ports, and corresponding modes in the cylindrical cavity can be excited through the two input ports; the top surface of the upper part of the cylindrical cavity is provided with a plurality of radially distributed seams for interfering the miscellaneous modes and leading the miscellaneous modes not to be excited, and two sides of each seam are respectively provided with a strip-shaped groove for placing wave-absorbing materials and leading the energy to radiate outside the cylindrical cavity.

2. The cylindrical cavity based planar dielectric constant broadband test structure of claim 1, wherein: the magnetic coupling ring is formed in an annular shape by connecting an inner conductor and an outer conductor through copper wires.

3. The cylindrical cavity based planar dielectric constant broadband test structure of claim 1, wherein: the slits are distributed in an annular array on the top surface of the upper part of the cylindrical cavity by taking the second rectangular groove as a central point.

4. The cylindrical cavity based planar dielectric constant broadband test structure of claim 1, wherein: the input port is a 50 ohm impedance matching port.

5. The cylindrical cavity based planar dielectric constant broadband test structure of claim 1, wherein: the dielectric constant of the planar medium is less than 10.

6. The cylindrical cavity based planar dielectric constant broadband test structure of claim 1, wherein: the measuring frequency band of the test structure is 0.7 GHz-10 GHz.

7. The method for testing the cylindrical cavity-based planar dielectric constant broadband test structure according to any one of claims 1 to 6, comprising the following steps:

1) exciting by using a magnetic coupling ring in a cavity state to obtain a transmission coefficient S₂₁From S₂₁To obtain the resonant frequency f of the cavity₀And cavity quality factor Q₀；

2) Inserting plane medium into the rectangular mounting groove, and updating the transmission coefficient S after inserting the plane medium₂₁To obtain the resonance frequency f after perturbation₁And the quality factor Q after perturbation₁The method comprises the following steps:

according to the perturbation principle, after the planar medium is inserted, the resonance frequency and the quality factor are changed due to the disturbance of the intra-cavity field, so that the dielectric constant and the loss tangent of the planar medium are obtained through calculation;

the formula for the perturbation is:

Δε＝ε₂-ε₁

Δμ＝μ₂-μ₁

in the formula: f. of₀And f₁Respectively before and after insertion into a planar medium₁And ε₂The dielectric constant of the cylindrical cavity and the dielectric constant of the planar medium, mu₁And mu₂Permeability of the cylindrical cavity and of the planar medium, respectively, E₁And H₁Is the original electric and magnetic field in the cylindrical cavity, E₂And H₂Is the electric field and the magnetic field in the cylindrical cavity after being inserted into the plane medium,andare each E₁And H₁Conjugation of (2) V_CAnd V_SRespectively the volume of the cylindrical cavity and the volume of the plane medium, and Delta epsilon is the dielectric constant epsilon of the plane medium₂Dielectric constant epsilon with cylindrical cavity₁Δ μ is the permeability μ of the planar medium₂Magnetic permeability mu with cylindrical cavity₁A difference of (d);

the formula for calculating the dielectric constant and loss tangent of a planar medium is as follows:

in the formula: ε' is the real part of the dielectric constant,. epsilon. "is the imaginary part of the dielectric constant, tan is the loss tangent, x_omIs a zero order Bessel function J of the first kind₀(x) 0 th root, J₁(x_om) Is x_omCorresponding first order Bessel function J of the first kind₁(x) Value of (a), (b), f)₀And Q₀Is the original resonant frequency and quality factor of the cylindrical cavity, f₁And Q₁Is the resonant frequency and quality factor of the cylindrical cavity after insertion into the planar medium.

Technical Field

The invention relates to the technical field of material measurement, in particular to a cylindrical cavity-based planar dielectric constant broadband test structure and a test method thereof.

Background

With the rapid development of wireless communication technology, various microwave dielectric materials are widely used in radio frequency microwave engineering. Among them, accurate measurement of relevant characteristic parameters of microwave dielectric materials, such as dielectric constant and loss tangent, is a research topic of interest to researchers in recent years. Because the tested materials are different in shape, different in testing frequency band, different in physical state and the like, different testing methods can be selected for measurement according to the properties of the materials.

The existing design method for measuring the material characteristics is investigated and known, and the method specifically comprises the following steps:

Chul-Ki Kim et al revise the rectangular cavity perturbation formula, calculate the effective volume of the sample and the distribution of the field more accurately, provide that the measurement of the dielectric constant and the magnetic conductivity can be carried out without repositioning, and obtain more accurate material characteristic parameters.

N.K.Tiwari et al improve Q value by using a new feed topological structure, correct a perturbation formula in a high-state mode, and realize TE using a SIW cavity₁₀₅，TE₁₀₇,TE₁₀₉,TE₁₀₁₁The 4 modes are used for measuring the dielectric constant and the loss tangent between 10GHz and 20 GHz.

In general, there are many methods for measuring the relative dielectric constant and the loss tangent, which are mainly classified into a resonance method and a non-resonance method, but these methods are not perfect. The resonance method mainly measures materials with low loss, has higher accuracy, but can only measure single frequency, and has limited test bandwidth; the non-resonant method is mainly suitable for broadband measurement, but the accuracy of the measurement is not high. Therefore, the design of the cylindrical cavity for testing the broadband dielectric constant of the planar dielectric medium is of great significance.

Disclosure of Invention

The invention aims to overcome the defects in the prior art, provides a planar dielectric constant broadband test structure based on a cylindrical cavity, can effectively measure a low-frequency-band broadband, and has accurate calculation results.

In order to achieve the purpose, the technical scheme provided by the invention is as follows: the planar dielectric permittivity broadband test structure based on the cylindrical cavity comprises the cylindrical cavity and two magnetic coupling rings; the cylindrical cavity is formed by assembling an upper part and a lower part, a first rectangular groove is formed in the center of the bottom surface of the lower part of the cylindrical cavity, a second rectangular groove is formed in the center of the top surface of the upper part of the cylindrical cavity, the two rectangular grooves jointly form a rectangular mounting groove for placing a plane medium, and the plane medium is inserted into the rectangular mounting groove for fixing during testing; the side wall of the lower part of the cylindrical cavity is provided with two symmetrical input through holes, the two input through holes correspond to two magnetic coupling rings, namely one input through hole is used for installing one magnetic coupling ring, after the two magnetic coupling rings are installed, the two magnetic coupling rings and the two input through holes form two input ports, and corresponding modes in the cylindrical cavity can be excited through the two input ports; the top surface of the upper part of the cylindrical cavity is provided with a plurality of radially distributed seams for interfering the miscellaneous modes and leading the miscellaneous modes not to be excited, and two sides of each seam are respectively provided with a strip-shaped groove for placing wave-absorbing materials and leading the energy to radiate outside the cylindrical cavity.

Furthermore, the magnetic coupling ring is formed in a ring shape by connecting the inner conductor and the outer conductor through copper wires.

Furthermore, the seams are distributed in an annular array on the top surface of the upper part of the cylindrical cavity by taking the second rectangular groove as a central point.

Further, the input port is a 50 ohm impedance matching port.

Further, the dielectric constant of the planar medium is less than 10.

Furthermore, the measuring frequency band of the test structure is 0.7 GHz-10 GHz.

The invention also provides a test method of the plane dielectric constant broadband test structure based on the cylindrical cavity, which comprises the following steps:

1) exciting by using a magnetic coupling ring in a cavity state to obtain a transmission coefficient S₂₁From S₂₁To obtain the resonant frequency f of the cavity₀And cavity quality factor Q₀；

2) Inserting plane medium into the rectangular mounting groove, and updating the transmission coefficient S after inserting the plane medium₂₁To obtain the resonance frequency f after perturbation₁And the quality factor Q after perturbation₁The method comprises the following steps:

according to the perturbation principle, after the planar medium is inserted, the resonance frequency and the quality factor are changed due to the disturbance of the intra-cavity field, so that the dielectric constant and the loss tangent of the planar medium are obtained through calculation;

the formula for the perturbation is:

Δε＝ε₂-ε₁

Δμ＝μ₂-μ₁

in the formula: f. of₀And f₁Respectively before and after insertion into a planar medium₁And ε₂The dielectric constant of the cylindrical cavity and the dielectric constant of the planar medium, mu₁And mu₂Permeability of the cylindrical cavity and of the planar medium, respectively, E₁And H₁Is the original electric and magnetic field in the cylindrical cavity, E₂And H₂Is the electric field and the magnetic field in the cylindrical cavity after being inserted into the plane medium,andare each E₁And H₁Conjugation of (2) V_CAnd V_SRespectively the volume of the cylindrical cavity and the volume of the plane medium, and Delta epsilon is the dielectric constant epsilon of the plane medium₂Dielectric constant epsilon with cylindrical cavity₁Δ μ is the permeability μ of the planar medium₂Magnetic permeability mu with cylindrical cavity₁A difference of (d);

the formula for calculating the dielectric constant and loss tangent of a planar medium is as follows:

in the formula: ε' is the real part of the dielectric constant,. epsilon. "is the imaginary part of the dielectric constant, tan is the loss tangent, x_omIs a zero order Bessel function J of the first kind₀(x) 0 th root, J₁(x_om) Is x_omCorresponding first order Bessel function J of the first kind₁(x) Value of (a), (b), f)₀And Q₀Is the original resonant frequency and quality factor of the cylindrical cavity, f₁And Q₁Is the resonant frequency and quality factor of the cylindrical cavity after insertion into the planar medium.

Compared with the prior art, the invention has the following advantages and beneficial effects:

1. the test frequency band is 0.7-10 GHz, and the measurement frequency point can be less than 1GHz by utilizing the principle of one-cavity multi-mode, so that the low-frequency-band broadband measurement is realized.

2. The measuring object of the invention is a plane medium, the requirement on the shape of the sample is simpler, and the measuring requirement in the engineering is richer.

3. Compared with dielectric constant measurement by a non-resonance method, the method has the advantages that the calculation result is more accurate and more reliable.

Drawings

Fig. 1 is an exploded view of a planar dielectric permittivity broadband test structure.

Fig. 2 is a schematic view of the lower part of the cylindrical cavity.

Fig. 3 is a schematic structural diagram of an upper part of the cylindrical cavity.

Fig. 4 is a schematic structural view of a magnetic coupling ring.

FIG. 5 is a graph of field distribution simulation results at 0.861 GHz.

FIG. 6 shows the transmission coefficient S after the cavity of 0.857 GHz-0.865 GHz and the inserted planar medium₂₁And (5) a simulation result graph.

FIG. 7 is a graph of the field distribution simulation results at 3.098 GHz.

FIG. 8 shows the transmission coefficient S after the cavity is filled with the planar medium at 3.08 GHz-3.11 GHz₂₁And (5) a simulation result graph.

FIG. 9 is a graph of the simulation results for field distribution at 9.8418 GHz.

FIG. 10 shows the transmission coefficient S after the cavity and the inserted planar medium are at 9.82 GHz-9.855 GHz₂₁And (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 4, the present embodiment provides a planar dielectric constant broadband test structure based on a cylindrical cavity, the measurement frequency band is 0.7GHz to 10GHz, and the planar dielectric constant broadband test structure includes the cylindrical cavity and two magnetic coupling rings 2, wherein the magnetic coupling rings 2 are formed in a ring shape by connecting an inner conductor 21 and an outer conductor 22 with copper wires; the cylindrical cavity is formed by assembling an upper part and a lower part, a first rectangular groove 1101 is formed in the center of the bottom surface of the lower part 11 of the cylindrical cavity, a second rectangular groove 1201 is formed in the center of the top surface of the upper part 12 of the cylindrical cavity, the two rectangular grooves jointly form a rectangular mounting groove for placing the plane medium 3, and the plane medium 3 is inserted into the rectangular mounting groove for fixing during testing; the side wall of the lower part 11 of the cylindrical cavity is provided with two symmetrical input through holes 1102, the two input through holes 1102 correspond to the two magnetic coupling rings 2, namely one input through hole 1102 is used for mounting one magnetic coupling ring 2, after the two magnetic coupling rings 2 are mounted through screws, the two magnetic coupling rings 2 and the two input through holes 1102 form two input ports (specifically, 50-ohm impedance matching ports), and corresponding modes in the cylindrical cavity can be excited through the two input ports; the top surface of the upper part 12 of the cylindrical cavity is provided with a plurality of radially distributed slits 1202 for interfering the mixed modes and preventing the mixed modes from being excited, the slits 1202 take the second rectangular groove 1201 as a central point, the top surface of the upper part 12 of the cylindrical cavity is distributed in an annular array, and strip-shaped grooves 1203 are formed on two sides of each slit 1202 and used for placing wave-absorbing materials and enabling energy to be radiated outside the cylindrical cavity.

In this embodiment, the material of the cylindrical cavity is aluminum; the height of the lower part 11 of the cylindrical cavity is 18.5mm, the inner radius is 135mm, the thickness of the lower wall is 4mm, and the thickness of the peripheral wall is 5 mm; the height of an inner conductor 21 of the magnetic coupling ring is 12mm, the height of an outer conductor 22 of the magnetic coupling ring is 4mm, the height of a middle medium layer is 5mm, and the inner conductor and the outer conductor are connected through copper wires; the first rectangular groove 1101 and the second rectangular groove 1201 are 4mm in height, 1.5mm in cross section width and 10mm in length; the height of the upper part 12 of the cylindrical cavity is 4.5mm, the inner radius is 135mm, the upper wall thickness is 4mm, and the peripheral wall thickness is 5 mm; the number of the seams 1202 is 8, the included angle between the seams is 45 degrees, the width of the seam is 0.5mm, the length of the seam is 90mm, and the depth of the seam is 0.5 mm; the width of the long strip-shaped groove 1203 is 6mm, the length of the long strip-shaped groove 1203 is 90mm, the two sides of the groove are semi-cylinders with the diameter of 6mm, and the depth of the groove is 3.5 mm; the width of the planar medium 3 is 1.5mm, the length is 10mm, the height is greater than or equal to 23mm, and the dielectric constant is less than 10.

The following is a testing method of the planar dielectric constant broadband testing structure based on the cylindrical cavity in this embodiment, including the following steps:

1) exciting by using a magnetic coupling ring in a cavity state to obtain a transmission coefficient S₂₁From S₂₁To obtain the original resonant frequency f₀And an original quality factor Q₀；

2) Inserting a planar medium with a width of 1.5mm, a length of 10mm and a height of 23mm or more, and updating the transmission coefficient S₂₁To obtain the resonance frequency f after perturbation₁And the quality factor Q after perturbation₁The method comprises the following steps:

according to the perturbation principle, after the planar medium is inserted, the resonance frequency and the quality factor are changed due to the disturbance of the intra-cavity field, so that the dielectric constant and the loss tangent of the planar medium are obtained through calculation;

the formula for the perturbation is:

Δε＝ε₂-ε₁

Δμ＝μ₂-μ₁

in the formula: f. of₀And f₁Respectively before and after insertion into a planar medium₁And ε₂The dielectric constant of the cylindrical cavity and the dielectric constant of the planar medium, mu₁And mu₂Are respectively a circlePermeability of the column cavity and of the planar medium, E₁And H₁Is the original electric and magnetic field in the cylindrical cavity, E₂And H₂Is the electric field and the magnetic field in the cylindrical cavity after being inserted into the plane medium,andare each E₁And H₁Conjugation of (2) V_CAnd V_SRespectively the volume of the cylindrical cavity and the volume of the plane medium, and Delta epsilon is the dielectric constant epsilon of the plane medium₂Dielectric constant epsilon with cylindrical cavity₁Δ μ is the permeability μ of the planar medium₂Magnetic permeability mu with cylindrical cavity₁A difference of (d);

the formula for calculating the dielectric constant and loss tangent of a planar medium is as follows:

in the formula: ε' is the real part of the dielectric constant,. epsilon. "is the imaginary part of the dielectric constant, tan is the loss tangent, x_omIs a zero order Bessel function J of the first kind₀(x) 0 th root, J₁(x_om) Is x_omCorresponding first order Bessel function J of the first kind₁(x) Value of (a), (b), f)₀And Q₀Is the original resonant frequency and quality factor of the cylindrical cavity, f₁And Q₁Is the resonant frequency and quality factor of the cylindrical cavity after insertion into the planar medium.

Following is a test structure and method employing the aboveAnd measuring the dielectric constant and the loss tangent at 0.857 GHz-0.865 GHz. When the cavity was measured, there was a resonance point at 0.861GHz, as shown in FIG. 5, which is a graph of the field distribution simulation results at 0.861 GHz. As can be seen from the figure, the excited mode is TM₀₁₀。

Referring to FIG. 6, the transmission coefficient S is shown after the cavity with 0.857 GHz-0.865 GHz and the planar medium are inserted₂₁And (5) a simulation result graph. The figure shows that the resonant frequency shifts to the left after insertion into a planar medium. From S₂₁The resonant frequency f of the cavity can be obtained in a simulation result chart₀And quality factor Q₀Resonant frequency f after insertion into a planar medium₁And quality factor Q₁And substituting the parameters into a calculation formula to obtain the dielectric constant and the loss tangent of the planar medium.

The following are measurements of dielectric constant and loss tangent at 3.08GHz to 3.11GHz using the test structures and methods described above. When the cavity was measured, there was a resonance point at 3.098GHz, as shown in fig. 7, which is a graph of the field distribution simulation results at 3.098 GHz. As can be seen from the figure, the excited mode is TM₀₃₀。

Referring to FIG. 8, the transmission coefficient S is shown after the cavity is between 3.08GHz and 3.11GHz and the planar medium is inserted₂₁And (5) a simulation result graph. The figure shows that the resonant frequency shifts to the left after insertion into a planar medium. From S₂₁The resonant frequency f of the cavity can be obtained in a simulation result chart₀And quality factor Q₀Resonant frequency f after insertion into a planar medium₁And quality factor Q₁And substituting the parameters into a calculation formula to obtain the dielectric constant and the loss tangent of the planar medium.

The following are measurements of dielectric constant and loss tangent at 9.82GHz to 9.855GHz using the test structures and methods described above. When the cavity was measured, there was a resonance point at 9.8418GHz, as shown in FIG. 9, which is a graph of the field distribution simulation results at 9.8418 GHz. As can be seen from the figure, the excited mode is TM₀₉₀。

Referring to FIG. 10, the transmission coefficient S is shown after the cavity is inserted into the planar medium at 9.82 GHz-9.855 GHz₂₁Simulation result graph. The figure shows that the resonant frequency shifts to the left after insertion into a planar medium. From S₂₁The resonant frequency f of the cavity can be obtained in a simulation result chart₀And quality factor Q₀Resonant frequency f after insertion into a planar medium₁And quality factor Q₁And substituting the parameters into a calculation formula to obtain the dielectric constant and the loss tangent of the planar medium.

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.