CN111880012A - Method for detecting broadband continuous dielectric characteristic parameters of microwave dielectric substrate - Google Patents

Abstract

The invention discloses a method for detecting broadband continuous dielectric characteristic parameters of a microwave dielectric substrate. A test device can be set up based on two linear waveguide structures, and two ends of a material to be tested are fixed on the test device to obtain two linear waveguide structures. The scattering parameters are converted into corresponding ABCD matrices to obtain the first ABCD matrix corresponding to the first linear guided wave structure and the second ABCD matrix corresponding to the second linear guided wave structure. The ABCD matrix based on the double-line optimization , calculate the optimized complex propagation constant expression, thus obtain the conductor loss and radiation loss of the linear guided wave structure, calculate the dielectric loss, and determine the dielectric loss tangent of the dielectric substrate to determine the comprehensive phase number, linear loss, effective dielectric constant, Dielectric characteristic parameters such as dielectric constant of dielectric substrate, dielectric loss and dielectric loss tangent of dielectric substrate are accurately detected, so that the detected dielectric characteristic parameters have high precision.

Description

Detection method of broadband continuous dielectric characteristic parameters of microwave dielectric substrate

technical field

The invention relates to the technical field of extraction and testing of dielectric characteristic parameters of a dielectric substrate, in particular to a method for detecting broadband continuous dielectric characteristic parameters of a microwave dielectric substrate.

Background technique

When designing microwave (MW)/millimeter wave (MMW)/terahertz (THz) devices and circuits, it is important to know the dielectric properties (dielectric constant and dielectric loss tangent) of the dielectric substrate substrate used. What's true is that dielectric substrate manufacturers usually only provide dielectric information at a single frequency, such as 1GHz or 10GHz. In general, the dielectric properties do not change significantly over a small frequency range, but can still cause some deviation in the frequency offset and performance of the device. In addition, substrate materials from different manufacturers and different batches may also have different dielectric properties. At the same time, with the development of material technology, more and more new materials have been developed and applied in the field of electromagnetic fields. Therefore, the extraction of dielectric properties in microwave band has always been very important and meaningful, especially for newly developed materials.

Many methods and techniques for extracting dielectric properties have been proposed in the related literature, which can be divided into two categories. One is a narrowband measurement technique and the other is a broadband measurement technique. Narrowband measurement techniques are mainly resonator-based, which can provide more accurate measurements, but only work at discrete resonance points. Broadband measurement techniques typically rely on the transmission or reflection of electromagnetic waves rather than using resonant cavities, so the technique can provide broadband and continuous material properties.

At present, there are some methods that use multi-line to extract the material parameters of microwave dielectric substrates. However, the material parameters of microwave dielectric substrates detected by these methods often have problems of low precision or low accuracy.

SUMMARY OF THE INVENTION

In view of the above problems, the present invention proposes a method for detecting broadband continuous dielectric characteristic parameters of a microwave dielectric substrate.

In order to achieve the purpose of the present invention, a method for detecting broadband continuous dielectric characteristic parameters of a microwave dielectric substrate is provided, comprising the following steps:

S10, a test device is constructed based on two linear waveguide structures, and two ends of the material to be tested are fixed on the test device through a set of high-frequency microwave connectors; the two ends of the linear waveguide structure are provided with high-frequency microwave connectors, In order to connect the test device with the straight wave guided structure; the two straight wave guided structures include a first straight wave guided structure and a second straight wave guided structure, and the length of the first straight wave guided structure is greater than that of the second straight wave guided structure length;

S20, using a vector network analyzer to test the two straight-line guided wave structures respectively, to obtain scattering parameters of the two straight-line guided wave structures;

S30, converting the scattering parameters of the two linear waveguide structures into corresponding ABCD matrices, to obtain a first ABCD matrix corresponding to the first linear waveguide structure and a second ABCD matrix of the second linear waveguide structure;

S40, calculate and obtain the optimized comprehensive phase number and linear loss according to the first ABCD matrix and the second ABCD matrix, and determine the effective dielectric constant according to the comprehensive phase number-effective dielectric constant equation; the phase number-effective dielectric constant The electric constant equation records the relationship between the number of integrated phases and the effective dielectric constant;

S50, determining the dielectric constant of the dielectric substrate of the material to be tested according to the effective dielectric constant;

S60: Obtain conductor loss and radiation loss of the linear waveguide structure, calculate dielectric loss according to the linear loss, conductor loss and radiation loss, and determine the dielectric loss tangent of the dielectric substrate according to the dielectric loss, effective dielectric constant and dielectric constant of the dielectric substrate.

In one embodiment, the ABCD matrix includes:

In the formula, A represents the first parameter of the ABCD matrix, B represents the second parameter of the ABCD matrix, C represents the third parameter of the ABCD matrix, D represents the fourth parameter of the ABCD matrix, _S11 represents the input reflection coefficient, _S12 represents the inverse The forward transmission coefficient, S ₂₁ represents the forward transmission coefficient, S ₂₂ represents the output reflection coefficient, and Z _c represents the linear characteristic impedance of the linear waveguide structure.

In one embodiment, the comprehensive phase number calculation formula includes:

The calculation formula of the linear loss includes:

In the formula, β represents the number of integrated phases, α represents the linear loss, A _L1 represents the first matrix parameter of the first ABCD matrix, D _L1 represents the fourth matrix parameter of the first ABCD matrix, and A _S1 represents the first matrix parameter of the second ABCD matrix. Matrix parameters, D _S1 represents the fourth matrix parameter of the second ABCD matrix, Re represents the real part, Im represents the imaginary part, L ₁ represents the straight length of the first straight long waveguide structure, S ₁ represents the second straight short waveguide structure straight line length.

Specifically, the phase number-effective dielectric constant equation includes:

In the formula, ε _eff represents the effective dielectric constant equation, f represents the operating frequency, and c represents the speed of light.

Specifically, the formula for calculating the dielectric constant of the dielectric substrate includes:

In the formula, ε _r represents the dielectric constant of the dielectric substrate, and q represents the filling factor of the linear waveguide structure.

In one embodiment, the calculation formula of the dielectric loss includes:

α _d =α-α _c -α _r ,

The formula for calculating the dielectric loss tangent of the dielectric substrate includes:

In the formula, α _d represents the dielectric loss, α _c represents the conductor loss, α _r represents the radiation loss, tanδ represents the dielectric loss tangent of the dielectric substrate, ε _eff represents the effective dielectric constant equation, f represents the operating frequency, c represents the speed of light, ε _r represents the dielectric constant of the dielectric substrate, and q represents the fill factor of the linear waveguide structure.

Specifically, the calculation formula of the conductor loss includes:

其中T是金属导体的厚度，集肤效应电阻

δ、σ、μ分别是集肤深度、金属导体电导率、自由空间的磁导率，且

k₀表示模

其中，S表示中心信号导体的线宽，W表示中心信号导体与地平面的间距,k₀′表示与模k₀相关联的互补模，K表示表示第一类完全椭圆积分。In the formula, R _c represents the distributed series resistance of the central signal conductor, R _g represents the distributed series resistance of the ground plane, and Z _c represents the characteristic impedance of the waveguide structure. The calculation formula is:

where T is the thickness of the metal conductor and the skin effect resistance

δ, σ, and μ are the skin depth, the conductivity of metal conductors, and the permeability of free space, respectively, and

k ₀ means modulo

Among them, S represents the line width of the center signal conductor, W represents the distance between the center signal conductor and the ground plane, k ₀ ′ represents the complementary mode associated with the modulo k ₀ , and K represents the complete elliptic integral of the first kind.

Specifically, the calculation formula of the radiation loss includes:

Among them, S represents the line width of the central signal conductor, W represents the distance between the central signal conductor and the ground plane, K(k ₀ ) represents the first-type complete elliptic integral, and the superscript ' represents the complementary mode.

In one embodiment, the length of the first linear waveguide structure is twice or more than the length of the second linear waveguide structure.

In one embodiment, the fixed installation of the material to be tested in the testing device includes a fixed manner of welding or direct clamping.

The above-mentioned detection method for broadband continuous dielectric characteristic parameters of microwave dielectric substrates can be based on two linear guided wave structures to build a test device, fix both ends of the material to be tested on the test device through a set of high-frequency microwave connectors, and use vector network analysis. The instrument tests the two linear guided wave structures respectively, obtains the scattering parameters of the two linear guided wave structures, and converts the scattering parameters into corresponding ABCD matrices to obtain the first ABCD matrix and the first ABCD matrix corresponding to the first linear guided wave structure. For the second ABCD matrix corresponding to the two straight-line guided wave structures, the comprehensive phase number and the linear loss are respectively determined according to the first ABCD matrix and the second ABCD matrix, and the effective dielectric constant is determined according to the phase number and the phase number-effective dielectric constant equation, Determine the dielectric constant of the dielectric substrate of the material to be tested according to the effective dielectric constant, obtain the conductor loss and radiation loss of the linear waveguide structure, calculate the dielectric loss according to the linear loss, conductor loss and radiation loss, and determine according to the dielectric loss and effective dielectric constant The dielectric loss tangent of the dielectric substrate is used to accurately detect the dielectric characteristic parameters such as the comprehensive phase number, linear loss, effective dielectric constant, dielectric constant of the dielectric substrate, dielectric loss and dielectric loss tangent of the dielectric substrate. The ideal model of constant ε _r and dielectric loss tangent tanδ is used to alleviate the influence of errors caused by the fixed installation of microwave connectors, so that the detected dielectric parameters have high accuracy.

Description of drawings

1 is a flowchart of a method for detecting broadband continuous dielectric characteristic parameters of a microwave dielectric substrate according to an embodiment;

2 is a schematic diagram of a test fixture of a two-wire two-port guided wave structure based on an ABCD matrix according to an embodiment;

3 is a schematic diagram of a three-dimensional model for extracting dielectric parameters of an existing dielectric substrate in one embodiment;

4 is a top view of a stub structure based on an ungrounded coplanar waveguide in one embodiment;

5 is a schematic diagram of the phase number β result derived based on two-line optimization, long straight lines, and short straight lines in one embodiment;

6 is a schematic diagram of the result of the effective dielectric constant ε _eff derived based on double-line optimization, long straight lines, and short straight lines in one embodiment;

FIG. 7 is a schematic diagram of the result of obtaining the dielectric constant ε _r of the dielectric substrate based on the double-line optimization, the long straight line and the short straight line in an embodiment;

FIG. 8 is a schematic diagram of an enlarged result of the dielectric constant ε _r of the dielectric substrate obtained based on the double-line optimization in one embodiment;

FIG. 9 is a schematic diagram of the results of total linear loss α, conductor loss α _c , radiation loss α _r , and dielectric loss α _d obtained based on the two-line optimization method in one embodiment;

FIG. 10 is a schematic diagram of the result of the dielectric loss tangent tanδ of the dielectric substrate derived based on the two-line optimization in one embodiment.

Detailed ways

In order to make the purpose, technical solutions and advantages of the present application more clearly understood, the present application will be described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application, but not to limit the present application.

Reference herein to an "embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the present application. The appearances of the phrase in various places in the specification are not necessarily all referring to the same embodiment, nor a separate or alternative embodiment that is mutually exclusive of other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

Referring to FIG. 1, FIG. 1 is a flowchart of a method for detecting broadband continuous dielectric characteristic parameters of a microwave dielectric substrate according to an embodiment, including the following steps:

S10, a test device is constructed based on two linear waveguide structures, and two ends of the material to be tested are fixed on the test device through a set of high-frequency microwave connectors; the two ends of the linear waveguide structure are provided with high-frequency microwave connectors, In order to connect the test device with the straight wave guided structure; the two straight wave guided structures include a first straight wave guided structure and a second straight wave guided structure, and the length of the first straight wave guided structure is greater than that of the second straight wave guided structure length;

S20, using a vector network analyzer to test the two straight-line guided wave structures respectively, to obtain scattering parameters of the two straight-line guided wave structures;

S30, converting the scattering parameters of the two linear waveguide structures into corresponding ABCD matrices, to obtain a first ABCD matrix corresponding to the first linear waveguide structure and a second ABCD matrix of the second linear waveguide structure;

S40, calculate and obtain the optimized integrated phase number and linear loss (such as integrated linear loss) according to the first ABCD matrix and the second ABCD matrix, and determine the effective dielectric constant according to the integrated phase number-effective dielectric constant equation; The phase number-effective dielectric constant equation records the relationship between the integrated phase number and the effective dielectric constant; specifically, in this step, the optimized complex propagation constant expression can be obtained based on the first ABCD matrix and the second ABCD matrix, namely, Extract the total attenuation and phase number of the linear structure based on the two-line optimization;

S50, determining the dielectric constant of the dielectric substrate of the material to be tested according to the effective dielectric constant;

S60: Obtain conductor loss and radiation loss of the linear waveguide structure, calculate dielectric loss according to the linear loss, conductor loss and radiation loss, and determine the dielectric loss tangent of the dielectric substrate according to the dielectric loss, effective dielectric constant and dielectric constant of the dielectric substrate.

The above-mentioned material to be tested is a dielectric material to be tested, such as a linear waveguide structure to be tested. The two rectilinear waveguide structures may include coplanar waveguide structures suitable for ungrounded, microstrip, stripline, or substrate-integrated waveguides, among others.

This embodiment is based on two straight-line microwave guided wave structures (linear guided wave structures) with different lengths to form a test device. The scattering parameter (S-parameter) results obtained respectively are converted into corresponding ABCD matrices, and the ABCD matrix and the complex are converted into corresponding ABCD matrices. The propagation constants are related to each other. Through the ABCD matrix based on the two-line optimization, the optimized complex propagation constant expression is calculated, and then the total attenuation α, phase number β, characteristic impedance Z _c , and dielectric substrate of the linear guided wave structure can be directly extracted. The dielectric constant ε _r and the dielectric loss tangent tanδ. Compared with the single-line method, the double-line optimization method can alleviate the influence of errors caused by the fixed installation of the microwave connector, and obtain more accurate and continuous dielectric parameters of the broadband dielectric substrate. The method can be applied to waveguide structures such as ungrounded coplanar waveguide structures, microstrip lines, strip lines, and substrate-integrated waveguides. In particular, the method is well suited for ungrounded coplanar waveguide structures, which are well suited for plating some newly developed dielectric materials (only one plating is required, but structures such as microstrip lines require multiple platings), avoiding Therefore, the manufacturing cost is high, the difficulty is high, and the consistency error of conductor thickness and roughness may be caused by multiple electroplating processes.

The above-mentioned detection method for broadband continuous dielectric characteristic parameters of microwave dielectric substrates can be based on two linear guided wave structures to build a test device, fix both ends of the material to be tested on the test device through a set of high-frequency microwave connectors, and use vector network analysis. The instrument tests the two linear guided wave structures respectively, obtains the scattering parameters of the two linear guided wave structures, and converts the scattering parameters into corresponding ABCD matrices to obtain the first ABCD matrix and the first ABCD matrix corresponding to the first linear guided wave structure. For the second ABCD matrix corresponding to the two straight-line guided wave structures, the comprehensive phase number and the linear loss are respectively determined according to the first ABCD matrix and the second ABCD matrix, and the effective dielectric constant is determined according to the phase number and the phase number-effective dielectric constant equation, Determine the dielectric constant of the dielectric substrate of the material to be tested according to the effective dielectric constant, obtain the conductor loss and radiation loss of the linear waveguide structure, calculate the dielectric loss according to the linear loss, conductor loss and radiation loss, and determine according to the dielectric loss and effective dielectric constant The dielectric loss tangent of the dielectric substrate is used to accurately detect the dielectric characteristic parameters such as the comprehensive phase number, linear loss, effective dielectric constant, dielectric constant of the dielectric substrate, dielectric loss and dielectric loss tangent of the dielectric substrate. The ideal model of constant ε _r and dielectric loss tangent tanδ is used to alleviate the influence of errors caused by the fixed installation of microwave connectors, so that the detected dielectric parameters have high accuracy.

In one embodiment, the ABCD matrix includes:

In the formula, A represents the first parameter of the ABCD matrix, B represents the second parameter of the ABCD matrix, C represents the third parameter of the ABCD matrix, D represents the fourth parameter of the ABCD matrix, _S11 represents the input reflection coefficient, _S12 represents the inverse The forward transmission coefficient, S ₂₁ is the forward transmission coefficient, S ₂₂ is the output reflection coefficient, and Z _c is the linear characteristic impedance of the linear waveguide structure (such as the first linear waveguide structure and the second linear waveguide structure).

其中，A_L1表示第一ABCD矩阵的第一矩阵参数，B_L1表示第一ABCD矩阵的第二矩阵参数，C_L1表示第一ABCD矩阵的第三矩阵参数，D_L1表示第一ABCD矩阵的第四矩阵参数。第二直线导波结构对应的第二ABCD矩阵为：

其中，A_S1表示第二ABCD矩阵的第一矩阵参数，B_S1表示第二ABCD矩阵的第二矩阵参数，C_S1表示第二ABCD矩阵的第三矩阵参数，D_S1表示第二ABCD矩阵的第四矩阵参数。两端口直线导波结构与ABCD矩阵示意图如图2所示。Specifically, the first ABCD matrix corresponding to the first linear waveguide structure is:

Among them, A _L1 represents the first matrix parameter of the first ABCD matrix, B _L1 represents the second matrix parameter of the first ABCD matrix, C _L1 represents the third matrix parameter of the first ABCD matrix, and D _L1 represents the first ABCD matrix. Four matrix parameters. The second ABCD matrix corresponding to the second linear guided wave structure is:

Among them, A _S1 represents the first matrix parameter of the second ABCD matrix, B _S1 represents the second matrix parameter of the second ABCD matrix, C _S1 represents the third matrix parameter of the second ABCD matrix, and D _S1 represents the second ABCD matrix. Four matrix parameters. The schematic diagram of the two-port linear guided wave structure and the ABCD matrix is shown in Figure 2.

In one embodiment, the comprehensive phase number calculation formula includes:

The calculation formula of the linear loss includes:

In the formula, β represents the number of integrated phases, α represents the linear loss, A _L1 represents the first matrix parameter of the first ABCD matrix, D _L1 represents the fourth matrix parameter of the first ABCD matrix, and A _S1 represents the first matrix parameter of the second ABCD matrix. Matrix parameters, D _S1 represents the fourth matrix parameter of the second ABCD matrix, Re represents the real part, Im represents the imaginary part, L ₁ represents the straight length of the first straight long waveguide structure, S ₁ represents the second straight short waveguide structure straight line length.

The above-mentioned phase number β based on two-line optimization is related to the ABCD matrix (such as the first ABCD matrix and the second ABCD matrix) of the long straight line (the first straight-line guided wave structure) and the short straight line (the second straight-line guided wave structure). .

Specifically, the phase number-effective dielectric constant equation includes:

In the formula, ε _eff represents the effective dielectric constant equation, f represents the operating frequency, and c represents the speed of light.

Specifically, the formula for calculating the dielectric constant of the dielectric substrate includes:

In the formula, ε _r represents the dielectric constant of the dielectric substrate, and q represents the filling factor of the linear waveguide structure.

At this point, there are:

Specifically, the calculation formula of the dielectric loss includes:

α _d =α-α _c -α _r ,

The formula for calculating the dielectric loss tangent of the dielectric substrate includes:

In the formula, α _d represents the dielectric loss, α _c represents the conductor loss, α _r represents the radiation loss, tanδ represents the dielectric loss tangent of the dielectric substrate, ε _eff represents the effective dielectric constant equation, f represents the operating frequency, c represents the speed of light, ε _r represents the dielectric constant of the dielectric substrate, and q represents the fill factor of the linear waveguide structure. The values of the filling factor q, the conductor loss α _c , and the radiation loss α _r are related to the selected structures (eg, the first linear waveguide structure and the second linear waveguide structure).

In one example, for an ungrounded coplanar waveguide structure, the calculation formula of the conductor loss includes:

In the formula, R _c represents the characteristic impedance of the linear waveguide structure, R _g represents the distributed series resistance of the linear waveguide structure, and Z _c represents the characteristic impedance of the waveguide structure.

中心信号导体的分布串联电阻

地平面的分布串联电阻

T是金属导体的厚度，集肤效应电阻

δ、σ、μ分别是集肤深度、金属导体电导率、自由空间的磁导率，且

k₀表示模

其中，S表示中心信号导体的线宽，W表示中心信号导体与地平面的间距,k₀′表示与模k₀相关联的互补模，K表示表示第一类完全椭圆积分。Specifically, the characteristic impedance

Distributed series resistance of the center signal conductor

Distributed series resistance of the ground plane

T is the thickness of the metal conductor, the skin effect resistance

δ, σ, and μ are the skin depth, the conductivity of metal conductors, and the permeability of free space, respectively, and

k ₀ means modulo

Among them, S represents the line width of the center signal conductor, W represents the distance between the center signal conductor and the ground plane, k ₀ ′ represents the complementary mode associated with the modulo k ₀ , and K represents the complete elliptic integral of the first kind.

In one example, the calculation formula of the radiation loss includes:

Among them, S represents the line width of the central signal conductor, W represents the distance between the central signal conductor and the ground plane, K(k ₀ ) represents the first-type complete elliptic integral, and the superscript ' represents the complementary mode.

介质波长

In this example, the radiation factor

Medium wavelength

In one embodiment, the length of the first linear waveguide structure is twice or more than the length of the second linear waveguide structure.

The test device constructed in this embodiment is composed of two linear microwave waveguide structures of different lengths. The length of the long linear waveguide structure (the first linear waveguide structure) is equal to the length of the short linear waveguide structure (the second linear waveguide structure). 2 times or more is better, and its scattering parameters are tested by high-frequency microwave connectors.

In one embodiment, the fixed installation of the material to be tested in the testing device includes a fixed manner of welding or direct clamping.

In this embodiment, metal copper is attached to the surface of the material to be tested; the fixed installation of the material to be tested in the testing device includes welding or direct clamping.

Compared with the prior art, the technical effects of the method for detecting broadband continuous dielectric characteristic parameters of microwave dielectric substrates are as follows:

1) Compared with other methods, such as the wave cascade matrix algorithm, this method is simpler and more convenient to test and operate, and the parameter extraction accuracy is high. It is only composed of a simple microwave guided wave structure composed of two straight lines of different lengths, and the circuit can be directly extracted. Total attenuation, number of phases, characteristic impedance, substrate dielectric constant and dielectric loss tangent, etc.;

2) Since the method is based on the two-line optimized ABCD matrix for parameter extraction, the method can alleviate the derivation error caused by connector welding and device manufacturing to a certain extent, and consider the conductor loss and radiation loss of the structure at the same time. Accurate and continuous broadband dielectric properties;

3) This method is the first to realize the extraction of the dielectric parameters of the dielectric substrate based on the ungrounded coplanar waveguide, which is very suitable for the electroplating of some newly developed dielectric materials (only one electroplating is required, but structures such as microstrip lines require multiple electroplating) , avoiding the high cost and difficulty of manufacturing, and the consistency error of conductor thickness and roughness that may be caused by multiple electroplating processes;

4) The two-line optimization extraction method is not only applicable to ungrounded coplanar waveguide structures, but also to structures such as microstrip lines, striplines, and substrate-integrated waveguides.

In one embodiment, taking the extraction of dielectric parameters of a dielectric substrate based on an ungrounded coplanar waveguide as an example, the structure shown in FIG. 3 is a schematic diagram of a three-dimensional model, which is composed of two straight lines of different lengths (linear guided wave structures). 4 is a top view of a stub structure based on an ungrounded coplanar waveguide in an embodiment of the present invention.

As shown in FIG. 3 and FIG. 4 , a test device under a set of linear waveguide structures with different lengths shown in this embodiment is fixed by high-frequency microwave connectors 1 at both ends of the material 2 to be tested. 2 and the high-frequency microwave connector 1 can be fixed by welding or by direct clamping, and the upper surface of the material to be tested 2 is a metal copper surface 3 . Under the test of the test device, an error frame 4 is formed at the joint between the two ends of the material to be tested 2 and the high-frequency microwave connector 1 .

The method is experimentally verified with the widely used microwave dielectric material FR4 as the test material. In this embodiment, two straight samples of ungrounded coplanar waveguides with lengths of 50 mm and 100 mm, respectively, are used as test objects. The thickness of the FR4 material is 0.5mm, and one side is etched with 18μm thick copper metal, the signal line width S and the gap W are 1.3mm and 0.16mm, respectively, and two SMA coaxial connectors are carefully welded in these two straight lines. , so that they have almost the same welding effect, thus ensuring that their mechanical and electrical properties are close.

Further, the two straight lines produced are measured with a vector network analyzer (VNA) N5247A, and the scattering parameter results of the two straight lines are obtained, and then the equation

和

Converted to ABCD matrix, the ABCD matrix of long straight line and short straight line are respectively expressed as

and

Further, using the ABCD matrix of the long straight line and the short straight line to deduce the phase number β based on the two-line optimization, thereby further deriving the effective dielectric constant ε _eff of the structure, its equation is:

In order to illustrate the superiority of the two-line optimization method, the results using the single-line calculation are also presented here. According to the ABCD matrix of the long straight line and the short straight line, the respective phase numbers β are calculated respectively, so as to further deduce the effective dielectric constant ε _eff of the respective structures. The equation used is:

The results of phase number β and effective dielectric constant ε _eff obtained based on two-line optimization, long straight line, and short straight line are shown in Figures 5 and 6.

Further, using the following relationship between the dielectric constant ε _r of the dielectric substrate and the obtained effective dielectric constant ε _eff , the dielectric constant ε _r of the dielectric substrate is calculated:

where q is the fill factor of the selected structure. For the ungrounded coplanar waveguide structures described in Figures 2 and 3, the fill factor q can be calculated by the following equation:

where K is a complete elliptic integral of the first kind, and k′ ₀ and k′ ₁ are the complementary moduli associated with modulo k ₀ and k ₁ , given by:

Among them, S and W are the signal line width and slot width of the ungrounded coplanar waveguide, respectively, and H is the thickness of the dielectric substrate. K(k)/K(k'), K(k) and K'(k) can be calculated by the following equations:

Finally, the dielectric constant ε _{r of the dielectric substrate is obtained based on the double-line optimization, long straight line, and short straight line. The result is shown in Figure 7. Figure 8 is an enlarged view of the dielectric constant ε r of} the dielectric substrate derived based on the double-line optimization. It can be seen from the figure that the dielectric constant _εr values of the dielectric substrate at 10 GHz based on the double-line optimization, the long straight line and the short straight line are 17.37, 9.95 and 4.37, respectively. Since the material provided by the supplier has an ε _r of 4.4 at 10 GHz, the ε _r extracted based on the optimized two-line algorithm is obviously closer to the reference value, and in an extremely wide frequency band (4 to 20 GHz), the difference between the two is only -0.03 (0.68%) to -0.07 (1.59%).

Further, using the ABCD matrix of the long straight line and the short straight line, the straight line loss α based on the two-line optimization is deduced, and its expression is:

The relationship between the linear loss α and the conductor loss α _c , the radiation loss α _r , and the dielectric loss α _d based on the two-line optimization is established to calculate the dielectric loss α _d , thereby deriving the dielectric loss tangent tanδ of the dielectric substrate, as follows:

The calculation expression of the dielectric loss α _d is as follows:

α _d =α- _αc - _αr

The calculation expression of the dielectric loss tangent tanδ of the dielectric substrate is as follows:

The calculation expression of the conductor loss α _c is as follows:

中心信号导体的分布串联电阻

地平面的分布串联电阻

T是金属导体的厚度，集肤效应电阻

δ、σ、μ分别是集肤深度、金属导体电导率、自由空间的磁导率，且

Among them, the characteristic impedance

Distributed series resistance of the center signal conductor

Distributed series resistance of the ground plane

T is the thickness of the metal conductor, the skin effect resistance

δ, σ, and μ are the skin depth, the conductivity of metal conductors, and the permeability of free space, respectively, and

The calculation expression of the radiation loss α _r is as follows:

介质波长

Among them, the radiation factor

Medium wavelength

Finally, the total linear loss α, conductor loss α _c , radiation loss α _r , and dielectric loss α _d obtained based on the two-line optimization method are shown in Figure 9, and Figure 10 is the dielectric loss tangent of the dielectric substrate derived based on the two-line optimization. The value of tanδ results. It can be seen from Figure 8 that the radiation loss and conductor loss only account for a small part of the total loss, and the main source of loss is the dielectric loss of the substrate, which increases with the increase of frequency. It can be seen from Figure 10 that the value of tanδ gradually increases from 0.0186 to 0.0214 between 8 and 20 GHz, which is a difference of 0.0014 (7%) compared to the 10 GHz reference value (0.02) provided by the supplier. The extracted tan delta value at 10 GHz is 0.0199, the difference from the reference value is 0.0001 (0.5%). The extraction accuracy becomes relatively poor below 8 GHz, because at low frequencies, the electrical length of the corresponding straight line is too small. The extraction accuracy of the material parameters of this method is higher than other commonly used methods in the literature.

Further, since this example uses SMA coaxial connectors, the dielectric substrate material properties are only characterized at frequencies below 20 GHz. The proposed algorithm is based on the quasi-TEM approximation, if the quasi-TEM wave assumption and good welding accuracy of millimeter-wave connectors (such as 2.92mm connectors) are satisfied, the feature extraction of dielectric materials at higher frequencies can be achieved.

Further, this example verifies the effectiveness of the method in the frequency range below 20 GHz, which can accurately invert the complex permittivity of the dielectric substrate, and the extraction errors of the permittivity and the dielectric loss tangent are 0.68%, respectively. (4.37vs 4.4) and 0.5% (0.0199vs 0.02),. The main source of errors is that the connection and welding of long and short lines are not exactly the same, and there are also errors from metal surface oxidation and preparation. This method is also applicable to other guided wave structures. After deriving the differential phase and effective dielectric constant, and combining with the structure size to accurately separate various losses, the dielectric constant and dielectric loss tangent of the dielectric substrate can be extracted.

The patent of the present invention is exemplarily described above in conjunction with the extraction of the dielectric parameters of the dielectric substrate based on the ungrounded coplanar waveguide and the experimental results. Various improvements made by adopting the method ideas and technical solutions of the present invention fall within the protection scope of the present invention.

It can be seen that this embodiment implements a characterization method for extracting broadband continuous dielectric properties of microwave dielectric substrates based on two-line optimization ABCD matrix.

The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity, all possible combinations of the technical features in the above embodiments are not described. However, as long as there is no contradiction in the combination of these technical features, all It is considered to be the range described in this specification.

It should be noted that the term "first\second\third" involved in the embodiments of the present application is only to distinguish similar objects, and does not represent a specific ordering of objects. It is understandable that "first\second\third" "Three" may be interchanged in a particular order or sequence where permitted. It should be understood that the "first\second\third" distinctions may be interchanged under appropriate circumstances to enable the embodiments of the application described herein to be practiced in sequences other than those illustrated or described herein.

The terms "comprising" and "having" and any variations thereof in the embodiments of the present application are intended to cover non-exclusive inclusion. For example, a process, method, apparatus, product or device comprising a series of steps or modules is not limited to the listed steps or modules, but optionally also includes unlisted steps or modules, or optionally also includes Other steps or modules inherent to these processes, methods, products or devices.

The above-mentioned embodiments only represent several embodiments of the present application, and the descriptions thereof are specific and detailed, but should not be construed as a limitation on the scope of the invention patent. It should be pointed out that for those skilled in the art, without departing from the concept of the present application, several modifications and improvements can be made, which all belong to the protection scope of the present application. Therefore, the scope of protection of the patent of the present application shall be subject to the appended claims.

Claims (10)

1. A method for detecting broadband continuous dielectric characteristic parameters of a microwave dielectric substrate is characterized by comprising the following steps:

s10, building a testing device based on the two linear guided wave structures, and fixing two ends of a material to be tested on the testing device through a group of high-frequency microwave connectors; the two ends of the linear guided wave structure are provided with high-frequency microwave connectors so that the testing device is connected with the linear guided wave structure; the two linear guided wave structures comprise a first linear guided wave structure and a second linear guided wave structure, and the length of the first linear guided wave structure is greater than that of the second linear guided wave structure;

s20, respectively testing the two linear guided wave structures by using a vector network analyzer to obtain scattering parameters of the two linear guided wave structures;

s30, converting scattering parameters of the two linear guided wave structures into corresponding ABCD matrixes to obtain a first ABCD matrix corresponding to the first linear guided wave structure and a second ABCD matrix corresponding to the second linear guided wave structure;

s40, calculating according to the first ABCD matrix and the second ABCD matrix to obtain an optimized comprehensive phase number and linear loss, and determining an effective dielectric constant according to a comprehensive phase number-effective dielectric constant equation; the phase number-effective dielectric constant equation records the relationship between the integrated phase number and the effective dielectric constant;

s50, determining the dielectric constant of the dielectric substrate of the material to be measured according to the effective dielectric constant;

s60, obtaining conductor loss and radiation loss of the linear wave guide structure, calculating dielectric loss according to the linear loss, the conductor loss and the radiation loss, and determining dielectric loss tangent of the dielectric substrate according to the dielectric loss, the effective dielectric constant and the dielectric constant of the dielectric substrate.

2. The method for detecting the broadband continuous dielectric characteristic parameter of the microwave dielectric substrate according to claim 1, wherein the ABCD matrix comprises:

in the formulaA denotes a first parameter of the ABCD matrix, B denotes a second parameter of the ABCD matrix, C denotes a third parameter of the ABCD matrix, D denotes a fourth parameter of the ABCD matrix, S₁₁Representing the input reflection coefficient, S₁₂Representing the reverse transmission coefficient, S₂₁Denotes the forward transmission coefficient, S₂₂Representing the output reflection coefficient, Z_cRepresenting the linear characteristic impedance of the linear guided wave structure.

3. The method for detecting the broadband continuous dielectric characteristic parameter of the microwave dielectric substrate according to claim 1, wherein the comprehensive phase calculation formula comprises:

the calculation formula of the linear loss comprises:

wherein β represents the number of integrated phases, α represents the linear loss, and A_L1First matrix parameters, D, representing a first ABCD matrix_L1Fourth matrix parameter, A, representing the first ABCD matrix_S1First matrix parameters, D, representing a second ABCD matrix_S1A fourth matrix parameter representing the second ABCD matrix, Re representing the real part, Im representing the imaginary part, L₁Denotes the linear length, S, of the first linear waveguide structure₁Indicating the linear length of the second linear short waveguide structure.

4. The method for detecting the broadband continuous dielectric characteristic parameter of the microwave dielectric substrate as claimed in claim 3, wherein the equation of phase number-effective dielectric constant includes:

in the formula (I), the compound is shown in the specification,_effequation representing effective dielectric constantF denotes the operating frequency and c denotes the speed of light.

5. The method for detecting the broadband continuous dielectric characteristic parameter of the microwave dielectric substrate as claimed in claim 4, wherein the formula for calculating the dielectric constant of the dielectric substrate comprises:

in the formula (I), the compound is shown in the specification,_rdenotes the dielectric constant of the dielectric substrate, and q denotes the fill factor of the linear waveguide structure.

6. The method for detecting the broadband continuous dielectric characteristic parameter of the microwave dielectric substrate according to claim 1, wherein the formula for calculating the dielectric loss comprises:

α_d＝α-α_c-α_r，

the calculation formula of the dielectric loss tangent of the dielectric substrate comprises the following steps:

in the formula, alpha_dDenotes dielectric loss, α_cRepresenting conductor loss, α_rDenotes the radiation loss, tan denotes the dielectric loss tangent of the dielectric substrate,_effrepresenting the effective dielectric constant equation, f the operating frequency, c the speed of light,_rdenotes the dielectric constant of the dielectric substrate, and q denotes the fill factor of the linear waveguide structure.

7. The method for detecting the broadband continuous dielectric characteristic parameter of the microwave dielectric substrate according to claim 6, wherein the calculation formula of the conductor loss comprises:

in the formula, R_cRepresenting the distributed series resistance, R, of the central signal conductor_gRepresenting distributed series resistance of ground plane, Z_cThe characteristic impedance of the waveguide structure is represented by the following calculation formula:

where T is the thickness of the metal conductor, the skin effect resistance

σ and μ are skin depth, conductivity of metal conductor, and permeability of free space, respectively, and

k₀display module

Wherein S represents the line width of the central signal conductor, W represents the distance between the central signal conductor and the ground plane, and k₀' representation and modulus k₀The associated complementary modes, K, represent the first class of perfect elliptic integrals.

8. The method for detecting the broadband continuous dielectric characteristic parameter of the microwave dielectric substrate according to claim 6, wherein the formula for calculating the radiation loss comprises:

where superscript' denotes the complementary mode.

9. The method according to claim 1, wherein the length of the first linear guided wave structure is 2 times or more the length of the second linear guided wave structure.

10. The method for detecting the broadband continuous dielectric characteristic parameter of the microwave dielectric substrate as claimed in claim 1, wherein the fixing and installation of the material to be tested in the testing device comprises a fixing mode of welding or direct clamping.

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