A millimeter wave dielectric performance test system and method based on suspended microstrip line

Abstract

The present invention discloses a millimeter wave dielectric property test system and method based on suspended microstrip line, the system comprises: a network analyzer, a metal shielding cavity, a suspended microstrip line resonator and a coupling adjustment device, the metal shielding cavity comprises a cavity and an openable and closable cover body arranged on the cavity, a card slot is arranged in the middle position of the inner side wall of the cavity, the suspended microstrip line resonator comprises a substrate and a metal conductive strip plated in the middle of the substrate, the substrate is directly processed from the sample to be tested, the substrate is carded in the card slot, so that the suspended microstrip line resonator is suspended in the center of the cavity; the coupling adjustment device is inserted into the cavity and is located below the substrate; the signal input and output ends of the network analyzer are respectively connected to the coupling adjustment devices on both sides of the metal shielding cavity. The present invention combines the advantages of the suspended microstrip line, designs a suspended microstrip line resonator, and places the suspended microstrip line resonator in an openable and closed closed metal cavity, which can reduce energy leakage and increase test stability and accuracy.

Description

Technical Field

[0001] The present invention relates to the technical field of microwave dielectric performance testing, and in particular to a millimeter wave dielectric performance testing system and method based on a suspended microstrip line. Background Art

[0002] With the development of 5G and the advent of the era of the Internet of Everything, dielectric materials represented by circuit board materials are increasingly used in production and life. In many practical applications, accurate testing of dielectric properties of dielectric materials is required, but accurate testing of dielectric material performance in the millimeter wave band has always been a difficult problem. The industry currently has no dielectric performance testing standards for the millimeter wave band.

[0003] The complex dielectric constant of dielectric materials has directional anisotropy, that is, there is a difference in the dielectric constant of the XY plane and the Z axis (thickness) direction of the dielectric material. The resonance mode of the dielectric constant test method determines in which direction the test method can accurately measure the dielectric properties of the material. The common test methods, such as the SPDR method and the quasi-optical cavity method, test the dielectric constant of the XY plane. The industry has an urgent need for accurate testing of the dielectric constant in the Z axis direction. The X-band standard test method specified by the International Circuit Board Association - IPC-TM-6502.5.5.5c, a clamped stripline resonator test method, has a quasi-TEM mode resonance mode, which can accurately test the dielectric properties of dielectric materials in the Z axis (thickness) direction. It has good test stability and has always been an internationally recognized test method. With the increase in the operating frequency of microwave devices, the X-band stripline resonator method has inherent defects and can no longer meet the requirements of dielectric performance testing in the millimeter wave band. The increase in frequency leads to the miniaturization of devices, making it difficult to process stripline resonators and test samples; at the same time, tiny devices require more precise performance parameters of dielectric materials, and the test accuracy of stripline resonator test methods can no longer meet the requirements.

[0004] As a variant of the traditional stripline, the suspended microstrip line inherits the advantages of the traditional stripline. The resonance mode is a quasi-TEM mode, which tests the dielectric properties of the dielectric material in the Z-axis (thickness) direction, and overcomes the drawbacks of the stripline in the millimeter wave band. Therefore, it is of great significance to design a suspended microstrip line resonator based on the traditional stripline resonance method and combining the advantages of the suspended microstrip line. Summary of the invention

[0005] The purpose of the present invention is to provide a millimeter-wave dielectric property test system and method based on a suspended microstrip line. On the basis of the traditional stripline resonance method, combined with the advantages of the suspended microstrip line, a suspended microstrip line resonator is designed, and the suspended microstrip line resonator is placed in an openable and closed closed metal cavity, which can reduce energy leakage, increase test stability and accuracy, and has the characteristics of high precision and easy operation.

[0006] To achieve the above object, the present invention provides the following solutions:

[0007] A millimeter-wave dielectric property test system based on a suspended microstrip line comprises a network analyzer, a metal shielding cavity, a suspended microstrip line resonator and a coupling adjustment device, wherein the metal shielding cavity comprises a cavity body and an openable and closable cover body arranged on the cavity body, a card slot is arranged in the middle position of the inner side wall of the cavity body, the suspended microstrip line resonator comprises a substrate and a metal conductive strip plated on the middle of the substrate, the substrate is directly processed from a sample to be tested, the substrate is carded in the card slot, so that the suspended microstrip line resonator is suspended in the center of the cavity; mounting holes for the coupling adjustment device are arranged on both sides of the metal shielding cavity, the coupling adjustment device is inserted into the cavity through the mounting holes and is located below the substrate; the signal input end and the output end of the network analyzer are respectively connected to the coupling adjustment devices on both sides of the metal shielding cavity.

[0008] Furthermore, the substrate is a rectangular sheet sample, the length and width of which match the size of the card slot and the thickness does not exceed 1.5 mm.

[0009] Furthermore, the network analyzer adopts Agilent PNA series with a sweep frequency range of 10MHz-67GHz.

[0010] The present invention also provides a millimeter wave dielectric property test method based on a suspended microstrip line, which is applied to the above-mentioned millimeter wave dielectric property test system based on a suspended microstrip line, and comprises the following steps:

[0011] S1, the sample to be tested is processed into a substrate with a thickness of T, and a metal conductive strip is plated on the central axis of the substrate to prepare a suspended microstrip line resonator, which is placed in a metal shielding cavity;

[0012] S2, the signal of the network analyzer is input into the metal shielding cavity through the coupling adjustment device, acts on the suspended microstrip line resonator, generates resonance, and records the resonance frequency f and quality factor Q generated by the resonance;

[0013] S3, substitute T, f, and Q into the following solution formula to obtain the dielectric constant and dielectric loss of the sample to be tested:

[0014] Dk=-22.6079*T-4.1438*f+0.7694*T*f+0.2102*x 2 +0.0419*f 2 +85.7421 (1)

[0015]

[0016]

[0017]

[0018] Wherein, formula (1) is used to calculate the dielectric constant, and formulas (2), (3), and (4) are used to calculate the dielectric loss, where Dk represents the dielectric constant, f represents the resonant frequency, and T represents the sample thickness. represents the conductor loss, represents dielectric loss, a c refers to the attenuation coefficient, λ is the wavelength of the suspended microstrip line, Z0 represents the equivalent impedance of the suspended microstrip line, R S is the surface resistance, W is the equivalent bandwidth of the metal conduction band, and h is the thickness of the metal conduction band.

[0019] Furthermore, the derivation process of the solution formula is as follows:

[0020] (1) Use HFSS to establish a simulation model of the suspended microstrip line resonator and metal shielding cavity;

[0021] (2) Set the thickness of the substrate for preparing the sample to be tested as variable T, in mm, and the dielectric constant as variable $p;

[0022] (3) Set the value of T to 0.1, 0.3, 0.5, 0.7, 0.9, 1; the value of $p to 2, 4, 6, 8, 10, 12; simulate and record the resonant frequency f and quality factor Q of each group;

[0023] (4) Import the data matrix of T-$pf in step (3) into the numerical analysis software MATLAB and draw a three-dimensional stereogram;

[0024] (5) Find the singular points in the three-dimensional image and perform secondary simulation and data correction on the data there;

[0025] (6) Repeat steps (4) and (5) until a smooth fitting surface is obtained;

[0026] (7) deriving the fitting formula corresponding to the fitted surface image;

[0027] (8) The dielectric properties are known and the thickness is T X1 and polytetrafluoroethylene with a dielectric constant of 2 and a thickness of T X2 The substrate was made of Rogers 3003 with a dielectric constant of 3, and the T X1 The resonance f corresponding to the thickness of PTFE X1 、T X2 Thickness Rogers 3003 corresponding to the resonance f X2 ;

[0028] (9) X1 ,2)、(T X2 , 3) Substitute into the fitting formula to obtain f'x1 、f' x2 ;

[0029] (10) Comparison f X1 、f X2 With f' x1 、f' x2 By adding the correction factor, we can finally obtain the dielectric constant solution formula (1) applicable to the entire test system.

[0030] According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects: the millimeter-wave dielectric property test system and method based on the suspended microstrip line provided by the present invention, the suspended microstrip line resonator designed based on the suspended microstrip line, and suspended in the center of the cavity, most of the electromagnetic waves propagate in the air, on the one hand, reducing the conductor loss and improving the test accuracy of the test method, on the other hand, increasing the cavity size, facilitating the processing of millimeter-wave frequency band devices; the suspended microstrip line resonator test method is a high-precision test method for the dielectric properties of the dielectric material in the Z-axis (thickness) direction in the millimeter-wave frequency band, the present invention can accurately test the dielectric properties of sheet dielectric materials such as circuit boards in the millimeter-wave frequency band, and the relative error of the dielectric constant and the dielectric loss is controlled within 8%. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0032] Figure 1 It is a structural schematic diagram of a millimeter wave dielectric property test system based on a suspended microstrip line according to an embodiment of the present invention;

[0033] Figure 2 is a schematic structural diagram of a suspended microstrip line resonator according to an embodiment of the present invention;

[0034] Description of the drawings: 1. Network analyzer; 2. Opening and closing connector; 3. Metal shielding cavity; 4. Metal conducting strip; 5. Substrate; 6. Coupling adjustment device. DETAILED DESCRIPTION

[0035] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0036] The purpose of the present invention is to provide a millimeter-wave dielectric property test system and method based on a suspended microstrip line. On the basis of the traditional stripline resonance method, combined with the advantages of the suspended microstrip line, a suspended microstrip line resonator is designed, and the suspended microstrip line resonator is placed in an openable and closed closed metal cavity, which can reduce energy leakage, increase test stability and accuracy, and has the characteristics of high precision and easy operation.

[0037] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0038] like Figure 1 and Figure 2 As shown, the millimeter-wave dielectric property test system based on suspended microstrip line provided by the present invention includes a network analyzer 1, a metal shielding cavity 3, a suspended microstrip line resonator and a coupling adjustment device 6, wherein the metal shielding cavity 3 includes a cavity and an openable and closable cover body arranged on the cavity, the openable and closable cover body is connected to the cavity through an openable and closable connecting member 2 (such as a hinged hinge), a card slot is arranged in the middle position of the inner side wall of the cavity, the suspended microstrip line resonator includes a substrate 5 and a metal conductive strip 4 plated on the middle of the substrate, the substrate 5 is directly processed from a sample to be tested, and the substrate 5 is carded in the card slot so that the suspended microstrip line resonator is suspended in the center of the cavity; mounting holes for the coupling adjustment device 6 are arranged on both sides of the metal shielding cavity 3, the coupling adjustment device 6 is penetrated into the cavity through the mounting holes, and is located below the substrate 5; the signal input end and the output end of the network analyzer 1 are respectively connected to the coupling adjustment devices 6 on both sides of the metal shielding cavity 3.

[0039] The method for testing the performance of millimeter wave dielectric materials of the present invention requires that the sample is a rectangular sheet sample, the length and width of which are consistent with the size of the slots of each frequency cavity, and the thickness does not exceed 1.5 mm.

[0040] The coupling adjustment device 6 transmits the external excitation signal into the cavity, and the suspended microstrip line resonator resonates under the action of the excitation signal. The closed metal shielding cavity 3 provides a stable resonance environment, and the dielectric properties of the sample to be tested placed therein are accurately measured. By controlling the size of the metal shielding cavity 3 and the suspended microstrip line resonator, the test frequency can be limited to a specific frequency range. During the test, the substrate is suspended in the center of the cavity, and the sample to be tested is fixed at the axis position of the cavity through the cavity slot design, which reduces the error caused by position offset, ensures the symmetry of the electric field, and can effectively improve the test accuracy of dielectric properties.

[0041] Different from the improved microstrip line mentioned in the existing article "Research on Microwave Dielectric Performance Test System Based on Improved Microstrip Line Resonant Cavity", the present invention creatively processes the sample to be tested directly into a substrate 5 (see Figure 2 ), a metal conducting strip 4 is plated on the central axis to form a resonator. This design improves the defects of the previous structure such as the air gap between the substrate and the sample to be tested and the easy breakage of the substrate.

[0042] The millimeter-wave dielectric property test system based on suspended microstrip line provided by the present invention is a suspended microstrip line resonator designed on the basis of a traditional stripline resonance method and in combination with the advantages of suspended microstrip line. In order to reduce energy leakage and increase test stability and accuracy, the suspended microstrip line resonator is placed in an openable and closed closed metal shielding cavity to form a suspended microstrip line resonant cavity. The signal of a network analyzer (the present invention adopts Agilent PNA series with a sweep frequency range of 10MHz-67GHz) is input into the suspended microstrip line resonant cavity through a coaxial line to generate resonance.

[0043] The present invention also provides a millimeter wave dielectric property test method based on a suspended microstrip line, which is applied to the above-mentioned millimeter wave dielectric property test system based on a suspended microstrip line, and comprises the following steps:

[0044] S1, the sample to be tested is processed into a substrate with a thickness of T, and a metal conductive strip is plated on the central axis of the substrate to prepare a suspended microstrip line resonator, which is placed in a metal shielding cavity;

[0045] S2, the signal of the network analyzer is input into the metal shielding cavity through the coupling adjustment device, acts on the suspended microstrip line resonator, generates resonance, and records the resonance frequency f and quality factor Q generated by the resonance;

[0046] S3, substitute T, f, and Q into the following solution formula to obtain the dielectric constant and dielectric loss of the sample to be tested:

[0047] Dk=-22.6079*T-4.1438*f+0.7694*T*f+0.2102*x 2 +0.0419*f 2 +85.7421 (1)

[0048]

[0049]

[0050]

[0051] Wherein, formula (1) is used to calculate the dielectric constant, and formulas (2), (3), and (4) are used to calculate the dielectric loss, where Dk represents the dielectric constant, f represents the resonant frequency, and T represents the sample thickness. represents the conductor loss, represents dielectric loss, a c refers to the attenuation coefficient, λ is the wavelength of the suspended microstrip line, Z0 represents the equivalent impedance of the suspended microstrip line, R S is the surface resistance, W is the equivalent bandwidth of the metal conduction band, and h is the thickness of the metal conduction band.

[0052] In the steps S1-S2, the specific operation steps of the test system are as follows:

[0053] Connect the resonant cavity to the network analyzer through a coaxial cable, build a test system, set the starting frequency and number of scanning points of the network analyzer, and calibrate the network analyzer and coaxial cable;

[0054] The metal shielding cavity is opened, and the sample to be tested with a thickness of T is processed into a suspended microstrip line resonator, which is placed in the slot of the metal cavity, and the metal shielding cavity is closed;

[0055] Find the resonance peak and adjust the coupling knob until the insertion loss is around -40dB;

[0056] Record the resonant frequency f and quality factor Q.

[0057] Wherein, in step S3, the derivation process of the solution formula is as follows:

[0058] (1) Use HFSS to establish a simulation model of the suspended microstrip line resonator and metal shielding cavity;

[0059] (2) Set the thickness of the substrate for preparing the sample to be tested as variable T, in mm, and the dielectric constant as variable $p;

[0060] (3) Set the value of T to 0.1, 0.3, 0.5, 0.7, 0.9, 1; the value of $p to 2, 4, 6, 8, 10, 12; simulate and record the resonant frequency f and quality factor Q of each group;

[0061] (4) Import the data matrix of T-$pf in step (3) into the numerical analysis software MATLAB and draw a three-dimensional stereogram;

[0062] (5) Find the singular points in the three-dimensional image and perform secondary simulation and data correction on the data there;

[0063] (6) Repeat steps (4) and (5) until a smooth fitting surface is obtained;

[0064] (7) deriving the fitting formula corresponding to the fitted surface image;

[0065] (8) The dielectric properties are known and the thickness is T X1 and polytetrafluoroethylene with a dielectric constant of 2 and a thickness of TX2 The substrate was made of Rogers 3003 with a dielectric constant of 3, and the T X1 The resonance f corresponding to the thickness of PTFE X1 、T X2 Thickness Rogers 3003 corresponding to the resonance f X2 ;

[0066] (9) X1 ,2)、(T X2 , 3) Substitute into the fitting formula to obtain f' x1 、f' x2 ;

[0067] (10) Comparison f X1 、f X2 With f' x1 、f' x2 By adding the correction factor, we can finally obtain the dielectric constant solution formula (1) applicable to the entire test system.

[0068] According to the above test method, the microwave dielectric property test of Rogers 3003 with stable dielectric property is carried out, and the accuracy of the present invention is verified. The sample specifications and purchase channels are shown in Table 1, and the sample test results are shown in Table 2.

[0069] Table 1 Sample specifications and purchasing channels

[0070]

[0071] Table 2 Sample test results

[0072]

[0073] It can be seen from Table 2 that when the method provided by the present invention is used for testing, the errors of the dielectric constant and the dielectric loss can be controlled within 8%, and the test results are good, which proves that the method is feasible and has high test accuracy.

[0074] The present invention improves the transmission line resonator structure and utilizes a combination of simulation and actual measurement methods, combined with numerical analysis software to fit the dielectric performance calculation formula, to achieve convenient, fast and high-precision dielectric performance testing within a certain frequency range, thereby improving the test accuracy and speed of microwave dielectric performance, and can achieve accurate testing of dielectric performance in the millimeter wave band. The test method provided by the present invention is based on the principle of transmission line resonators, and thus overcomes the defects of low test accuracy of the waveguide method and the coaxial air line method from the test principle. In the present invention, the test frequency can be limited to a specific frequency range by suspending the microstrip line resonator and the metal shielding cavity; at the same time, most of the suspension design is placed in the air, which reduces the impact of the frequency increase on the cavity design, so that the cavity can be applied to higher test frequencies.

[0075] The principles and implementation methods of the present invention are described in this article using specific examples. The description of the above embodiments is only used to help understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A millimeter wave dielectric performance test method based on a suspended microstrip line, applied to a millimeter wave dielectric performance test system based on a suspended microstrip line, characterized in that: The system comprises: a network analyzer, a metal shielding cavity, a suspended microstrip line resonator and a coupling adjustment device, wherein the metal shielding cavity comprises a cavity body and an openable and closable cover body arranged on the cavity body, a card slot is arranged in the middle position of the inner side wall of the cavity body, the suspended microstrip line resonator comprises a substrate and a metal conductive strip plated in the middle of the substrate, the substrate is directly processed from a sample to be tested, the substrate is carded in the card slot, so that the suspended microstrip line resonator is suspended in the center of the cavity; mounting holes for the coupling adjustment device are arranged on both sides of the metal shielding cavity, the coupling adjustment device is inserted into the cavity through the mounting holes and is located below the substrate; the signal input end and the output end of the network analyzer are respectively connected to the coupling adjustment devices on both sides of the metal shielding cavity; The method comprises the following steps: S1, processing the sample to be tested into a substrate with a thickness of T, and coating a metal conductive strip on the central axis of the substrate to prepare a suspended microstrip line resonator, which is placed in a metal shielding cavity; S2, the signal of the network analyzer is input into the metal shielding cavity through the coupling adjustment device, acts on the suspended microstrip line resonator, generates resonance, and records the resonance frequency f and quality factor Q generated by the resonance; S3, substitute T, f, and Q into the following solution formula to obtain the dielectric constant and dielectric loss of the sample to be tested: Dk=-22.6079*T-4.1438*f+0.7694*T*f+0.2102*T 2 +0.0419*f 2 +85.7421(1) Wherein, formula (1) is used to calculate the dielectric constant, and formulas (2), (3), and (4) are used to calculate the dielectric loss, where Dk represents the dielectric constant, f represents the resonant frequency, and T represents the sample thickness. represents the conductor loss, represents dielectric loss, a c refers to the attenuation coefficient, λ is the wavelength of the suspended microstrip line, Z0 represents the equivalent impedance of the suspended microstrip line, R S is the surface resistance, W is the equivalent bandwidth of the metal conduction band, and h is the thickness of the metal conduction band; The derivation process of the solution formula is as follows: (1) Use HFSS to establish a simulation model of the suspended microstrip line resonator and metal shielding cavity; (2) Set the thickness of the substrate for preparing the sample to be tested as variable T, in mm, and the dielectric constant as variable $p; (3) Set the value of T to 0.1, 0.3, 0.5, 0.7, 0.9, 1; the value of $p to 2, 4, 6, 8, 10, 12; simulate and record the resonant frequency f and quality factor Q of each group; (4) Import the data matrix of T-$pf in step (3) into the numerical analysis software MATLAB and draw a three-dimensional stereogram; (5) Find the singular points in the three-dimensional image and perform secondary simulation and data correction on the data there; (6) Repeat steps (4) and (5) until a smooth fitting surface is obtained; (7) deriving the fitting formula corresponding to the fitted surface image; (8) The dielectric properties are known and the thickness is T X1 and polytetrafluoroethylene with a dielectric constant of 2 and a thickness of T X2 The substrate was made of Rogers 3003 with a dielectric constant of 3, and the T X1 The resonance f corresponding to the thickness of PTFE X1 , T X2 Thickness Rogers 3003 corresponding to the resonance f X2 ; (9) X1 ,2)、(T X2 , 3) Substitute into the fitting formula to obtain f x '1, f x '2; (10) Comparison f X1 、f X2 With f x '1, f x '2, add the correction factor to get the final dielectric constant solution formula (1) applicable to the entire test system.

2. The millimeter wave dielectric property testing method based on suspended microstrip line according to claim 1 is characterized in that: The substrate is a rectangular sheet sample, the length and width of which match the size of the card slot, and the thickness does not exceed 1.5 mm.

3. The millimeter wave dielectric property testing method based on suspended microstrip line according to claim 1 is characterized in that: The network analyzer adopts Agilent PNA series, and the frequency sweep range is 10MHz-67GHz.

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