Grounding coplanar waveguide with low radiation loss and high signal uniformity

Abstract

The invention discloses a grounding coplanar waveguide with low radiation loss and high signal uniformity, and belongs to the field of magnetic parameter measurement. The grounding coplanar waveguide comprises a bottom metal grounding layer, a medium substrate, a grounding through hole, a signal line, a split signal line and two side metal grounding layers. The dielectric substrate is arranged above the metal grounding layer, two-side metal grounding layers are arranged above two sides of the dielectric substrate, the two-side metal grounding layers are respectively provided with more than two columns of grounding through holes to form a through hole array, a split signal line is arranged in the middle position above the dielectric substrate, and two ends of the split signal line are respectively connected with signal lines. One end of the split signal line is connected with a signal input end, and the other end is connected with a signal output end; the bottom metal grounding layer and the two side metal grounding layers are connected through grounding through holes. According to the invention, the phenomenon of broadening of a test curve caused by non-uniform distribution of a surface magnetic field is avoided, so that the test precision is improved to a great extent, and the radiation loss at a high-frequency position of the grounded coplanar waveguide is reduced.

Description

Technical Field

[0001] The present invention belongs to the field of testing parameters of magnetic materials in the microwave and millimeter-wave bands, and particularly relates to a novel grounded coplanar waveguide with low radiation loss and high signal uniformity. Background Art

[0002] Magnetism is one of the fundamental physical phenomena in the world, running through many processes in nature and a wide range of applications in human technology. From the guidance of the Earth's magnetic field for biological migration to the precise magnetic storage and magnetic induction technology in modern electronic devices, the magnetic principle is everywhere. Ferromagnetic materials are an important branch of magnetic substances. Due to their advantages of both electromagnetic properties, they play an indispensable role in many key fields such as electronics, energy, and medicine. From hard disk storage to transformers, from biomedical imaging to the motors of electric vehicles, the applications of ferromagnetic materials are extensive and crucial.

[0003] In order to better apply ferromagnetic materials, how to efficiently and accurately obtain the performance parameters of ferromagnetic materials has become the focus of research. Early methods for testing the performance parameters of ferromagnetic materials were often based on resonant cavities. However, with the continuous development of information technology, people have begun to pay more attention to the high-speed and integration of electronic components. Therefore, in the testing of materials, the demand for high-frequency and broadband testing is becoming increasingly strong. The traditional resonant cavity method only supports single-frequency point measurement and faces problems such as complex waveguide fabrication and poor sample adaptability in the high-frequency band (such as millimeter waves), making it difficult to meet the testing requirements. Therefore, the ferromagnetic resonance testing method based on planar transmission lines has become a research hotspot. The planar transmission line structures used for ferromagnetic resonance testing usually include microstrip lines, coplanar waveguides, etc. The microstrip line consists of a narrow metal strip (signal line), a grounding plane, and a dielectric substrate, with a simple structure and easy processing. However, its characteristic impedance and transmission characteristics are relatively fixed, so it is usually only used for testing within a specific frequency band. To achieve broadband testing, multiple microstrip lines of different sizes are required. The coplanar waveguide, due to its different microwave transmission characteristics, has a wider frequency range and higher flexibility compared to the microstrip line, and can achieve continuous broadband testing on the same coplanar waveguide. In addition, the coplanar waveguide has lower radiation loss and is easy to integrate active and passive components, so it is more widely used than the microstrip line testing.

[0004] In the traditional grounded coplanar waveguide, the microwave magnetic field distribution in the vertical direction of the signal line is uneven, which may thus excite different degrees of ferromagnetic resonance in the test sample, resulting in inaccurate testing. And due to process limitations, the single-layer grounding vias of the traditional grounded coplanar waveguide are often difficult to optimize to the best, leading to serious high-frequency radiation loss. Summary of the Invention

[0005] The object of the present invention is to provide a grounded coplanar waveguide with low radiation loss and high signal uniformity. The present invention solves the problems of uneven surface signal distribution and large high-frequency radiation loss existing in the traditional grounded coplanar waveguide from two aspects of signal line splitting and optimization of the ground via array, and provides a new grounded coplanar waveguide with better performance and higher precision for ferromagnetic resonance testing.

[0006] To solve the above technical problems, the specific technical solution of the present invention is as follows:

[0007] A grounded coplanar waveguide with low radiation loss and high signal uniformity, the grounded coplanar waveguide includes a bottom metal ground layer, a dielectric substrate, ground vias, signal lines, split signal lines, and two-side metal ground layers; the dielectric substrate is arranged above the metal ground layer, and two-side metal ground layers are arranged above both sides of the dielectric substrate, and each of the two-side metal ground layers is provided with more than 2 columns of ground vias to form a via array, and the ground vias in each column are arranged alternately, a split signal line is arranged at the middle position above the dielectric substrate, and signal lines are respectively connected to both ends of the split signal line, and one end of the signal lines at both ends of the split signal line is connected to a signal input end, and the other end is connected to a signal output end; the signal line and the split signal line can be connected with equal width, or can be connected with unequal width through a transition line structure; the bottom metal ground layer and the two-side metal ground layers are connected through the ground vias.

[0008] Further, the thickness of the bottom metal ground layer is greater than three times the skin depth of the metal at the lowest operating frequency.

[0009] Further, the signal lines at the input and output ends meet the impedance matching requirements, and the signal line and the split signal line meet the impedance matching requirements.

[0010] Further, the distance between the ground vias in the same column uses the minimum value allowed by the process, and the distance between the columns of ground vias is greater than the via radius.

[0011] Further, the length of the split signal line is greater than one-quarter wavelength of the lowest frequency used.

[0012] Further, the material of the dielectric substrate has high mechanical stability, low dielectric constant and low loss tangent.

[0013] Further, the bottom metal ground layer, the signal line, the split signal line and the two-side metal ground layers are made of materials with high conductivity.

[0014] Further, the surfaces of the signal line, the split signal line, the two-side metal ground layers and the bottom metal ground layer are gold-plated.

[0015] Compared with the prior art, the present invention has the following beneficial technical effects:

[0016] 1) A grounded coplanar waveguide structure with low radiation loss and high signal uniformity proposed by the present invention splits the middle signal line. While ensuring a characteristic impedance matching of 50 Ω, it homogenizes the magnetic field on the signal line to excite a uniform ferromagnetic resonance in the test sample, avoiding the broadening phenomenon of the test curve caused by uneven surface magnetic field distribution in the traditional grounded coplanar waveguide, and thus greatly improving the test accuracy.

[0017] 2) A grounded coplanar waveguide structure with low radiation loss and high signal uniformity proposed by the present invention optimizes the via hole array. By increasing the number of columns of the via hole array, it provides better electrical boundaries on both sides for the grounded coplanar waveguide. The electric field of the microwave signal terminates on the electrical boundaries, reducing the radiation loss at high frequencies of the grounded coplanar waveguide. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments of the present invention. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0019] Figure 1 It is a schematic diagram of the grounded coplanar waveguide structure with low radiation loss and high signal uniformity proposed by the present invention.

[0020] Figure 2 It is a VNA-FMR system for testing the grounded coplanar waveguide built in Embodiment 1 of the present invention.

[0021] Figure 3 It is a graph of the insertion loss S21 and return loss S11 of the grounded coplanar waveguide with low radiation loss and high signal uniformity designed in Embodiment 1 of the present experimental invention.

[0022] Figure 4 It is a surface magnetic field distribution diagram of the single signal lines at both ends and the split signal line in the middle of the grounded coplanar waveguide with low radiation loss and high signal uniformity designed in Embodiment 1 of the present experimental invention.

[0023] Figure 5 It is a graph of the insertion loss S21 and return loss S11 of the grounded coplanar waveguide with low radiation loss and high signal uniformity designed in Embodiment 2 of the present experimental invention.

[0024] Explanation of the marks in the figure: 1 - bottom metal ground layer; 2 - dielectric substrate; 3 - ground via hole; 4 - signal line; 5 - split signal line; 6 - metal ground layers on both sides. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0025] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0026] A ground coplanar waveguide with low radiation loss and high signal uniformity is as Figure 1 shown, which can be used to improve the accuracy of a Vector Network Analyzer-FerroMagnetic Resonance (VNA-FMR) test system. The ground coplanar waveguide includes a bottom metal ground layer 1, a dielectric substrate 2, via holes 3 for grounding, a signal line 4, a split signal line 5, and two side metal ground layers 6. The dielectric substrate 2 is disposed above the metal ground layer 1. Two side metal ground layers 6 are disposed above both sides of the dielectric substrate 2. Each of the two side metal ground layers 6 is provided with more than 2 columns of via holes 3 for grounding to form a via hole array, and the columns of via holes are arranged alternately. A split signal line 5 is disposed at the middle position above the dielectric substrate 2. Signal lines 4 are respectively connected to both ends of the split signal line 5. One end of each of the signal lines 4 at both ends of the split signal line 5 is connected to a signal input end, and the other end is connected to a signal output end; the signal line and the split signal line can be connected with equal width, or can be connected with unequal width through a transition line structure; the bottom metal ground layer 1 and the two side metal ground layers 6 are connected through the via holes 3 for grounding.

[0027] The bottom metal ground layer 1 uses a material with high conductivity to reduce conductor loss. The middle layer dielectric substrate 2 uses a material with low dielectric constant and low loss tangent to reduce the dielectric loss of the ground coplanar waveguide. The signal line 4 and the two side metal ground layers 6 also adopt materials with high conductivity.

[0028] Further, the thickness of the bottom metal ground layer is greater than three times the skin depth of the metal at the lowest operating frequency.

[0029] Further, the material of the dielectric substrate has high mechanical stability, low dielectric constant and low loss tangent to reduce the loss of microwave signals propagating in the dielectric of the ground coplanar waveguide;

[0030] Further, the distance between the signal line and the two side metal ground layers meets the impedance matching requirements to reduce the transmission loss caused by impedance mismatch during signal transmission.

[0031] Further, the signal line and the split signal line meet the impedance matching requirements.

[0032] Further, the impedance matching requirement means that its characteristic impedance is 50 Ω.

[0033] Further, the surfaces of the signal line, the split signal line, the two-side metal ground layer, and the bottom metal ground layer are gold-plated, which can prevent oxidation and reduce the contact resistance.

[0034] Further, the coating thickness is usually 0.1 - 1 μm. If it is too thick, it will cause an increase in high-frequency loss.

[0035] Further, the line width of the split signal line uses the minimum process dimension, and the spacing between each line is determined by the impedance matching requirement. The number of splits of the signal line is as many as possible.

[0036] Further, the length of the split signal line is greater than one-quarter wavelength of the lowest frequency used. For the convenience of testing, it is usually greater than 2 mm.

[0037] Further, the grounding vias satisfy that the spacing between the grounding vias in the same column uses the minimum value allowed by the process, and the spacing between each column of grounding vias is greater than the via radius.

[0038] Further, the radius of the grounding via is usually 25 - 100 μm, and a conductive material can be filled to reduce the resistance.

[0039] The specific application of the ground coplanar waveguide with low radiation loss and high signal uniformity during testing is as follows: First, place the magnetic sample film to be measured on the split signal line, and the sample length does not exceed the length of the split signal line. Then, apply an externally applied magnetic field with an adjustable magnitude in the direction perpendicular to the coplanar waveguide. Then, generate a microwave signal through a vector network analyzer. The microwave signal is transmitted through a coaxial cable to a waveguide coaxial converter with a characteristic impedance of 50 Ω, and then transmitted from the waveguide coaxial converter to the signal line of the ground coplanar waveguide; the microwave signal generates a microwave magnetic field inside the sample after being transmitted through the ground coplanar waveguide, and then acts together with the externally applied magnetic field to excite ferromagnetic resonance inside the magnetic sample, and part of the microwave energy is absorbed. The method of obtaining the absorption curve by testing the change of the insertion loss S21 of the microwave signal with the microwave frequency is the frequency sweep method. The method of obtaining the absorption curve by testing the change of the insertion loss S21 of the microwave signal with the externally applied magnetic field is the field sweep method.

[0040] Embodiment 1

[0041] This embodiment proposes a ground coplanar waveguide structure with low radiation loss and high signal uniformity.

[0042] In the ground coplanar waveguide structure of this embodiment, the material used for the bottom metal ground layer is copper, and the conductivity is about 5.8E+08 S / m.

[0043] The lowest frequency for ferromagnetic resonance testing in this embodiment is 1 GHz. At this frequency, the skin depth of copper is about 2.9 μm, and the calculation formula is as follows:

[0044]

[0045] Among them, δ is the skin depth (unit: meter), ω is the angular frequency, μ is the magnetic permeability of the conductor, and σ is the electrical conductivity of the conductor.

[0046] In the ground coplanar waveguide structure of this embodiment, the thickness of the bottom metal ground layer is 0.033 mm.

[0047] In the ground coplanar waveguide structure of this embodiment, the dielectric substrate material is Rogers RT / duriod 5800, the relative dielectric constant is 2.2, the dielectric loss tangent is 0.0009, and the thickness is 0.254 mm.

[0048] In the ground coplanar waveguide structure of this embodiment, the signal line uses copper as the material, the signal line width is 0.45 mm, and the thickness is 0.033 mm.

[0049] In the ground coplanar waveguide structure of this embodiment, the two side metal ground layers use copper as the material, and the slot spacing between the signal line is 0.076 mm;

[0050] Using an electromagnetic simulation software to build a model, it is simulated that the input and output port impedance of the ground coplanar waveguide structure of this embodiment is about 51 Ω;

[0051] The ground coplanar waveguide structure of this embodiment contains two layers of ground vias, the diameter of the ground vias is 0.1 mm, the spacing between the vias in the same layer is 0.2 mm, and the spacing between the two layers of vias is 0.2 mm;

[0052] In the ground coplanar waveguide structure of this embodiment, the signal line is split into three, the width of each split signal line is 0.1 mm, and the spacing between each split signal line is 0.075 mm;

[0053] Using an electromagnetic simulation software to build a model, it is simulated that the port impedance of the split signal line part in the ground coplanar waveguide structure of this embodiment is about 52 Ω;

[0054] The VNA-FMR test system is as Figure 2As shown, the specific test method is as follows: First, connect all the instruments in the system. The electromagnet and the current source provide an external magnetic field. The vector network analyzer (VNA) is used to transmit and receive microwave signals. Connect the grounded coplanar waveguide to the system through a fixture. The magnetic sample to be measured is placed on the split signal line part of the grounded coplanar waveguide, covering the split signal line and the groove, and the length does not exceed the length of the split signal line. The vector network analyzer transmits microwave signals, which are transmitted through the grounded coplanar waveguide to provide a microwave magnetic field for the sample. Under the action of the microwave magnetic field and the external magnetic field, the sample will undergo ferromagnetic resonance absorption at a certain frequency and external magnetic field, reducing the energy of the transmitted microwave signals. The insertion loss S21 of the detected signal is manifested through the vector network analyzer. During the sweep frequency test, by outputting microwave signals of different frequencies through the vector network analyzer, the ferromagnetic resonance absorption curve of S21 changing with frequency can be obtained, and parameters such as the resonance linewidth and resonance frequency can be obtained using Lorentz fitting; during the sweep field test, by scanning the external magnetic field, the ferromagnetic resonance absorption curve of S21 changing with the magnetic field can be obtained, and parameters such as the resonance linewidth and resonance magnetic field can be obtained using Lorentz fitting; in addition, parameters such as the Gilbert damping coefficient of the sample can be obtained through multiple sweep field tests.

[0055] Build a model using electromagnetic simulation software and simulate to obtain Figure 3 the insertion loss S21 and return loss S11 parameters of the grounded coplanar waveguide structure of this embodiment as shown. Among them, the insertion loss S21 is higher than -0.7 dB within 0 - 60 GHz, and the return loss S11 is lower than -25 dB within 0 - 60 GHz, indicating that the grounded coplanar waveguide structure of this embodiment fully meets the requirements of the ferromagnetic resonance test system.

[0056] Figure 4 This is the transverse magnetic field distribution on the two - end signal lines and the split signal line in this embodiment. It can be seen that compared with the single signal line for input and output at both ends, the transverse magnetic field distribution on the split signal line is more uniform.

[0057] Embodiment 2

[0058] In the grounded coplanar waveguide structure of this embodiment, the material used for the bottom metal ground layer is copper, and the conductivity is about 5.8E + 08 S / m;

[0059] The lowest frequency for ferromagnetic resonance testing in this embodiment is 70 GHz. At this frequency, the skin depth of copper is about 0.21 μm, so the thickness of the bottom metal ground layer is 0.033 mm;

[0060] In the grounded coplanar waveguide structure of this embodiment, the dielectric substrate material is Rogers RO3003, the relative dielectric constant is 3, the tangent of the dielectric loss angle is 0.0013, and the thickness is 0.254 mm;

[0061] In the grounded coplanar waveguide structure of this embodiment, the signal line uses copper as the material, the width of the signal line is 0.3 mm, and the thickness is 0.033 mm;

[0062] In the grounded coplanar waveguide structure of this embodiment, the materials of the two side metal ground layers are copper, and the slot spacing between the signal line and the ground layer is 0.046 mm;

[0063] Use electromagnetic simulation software to build a model, and the simulation shows that the impedance of the input and output ports in the grounded coplanar waveguide structure of this embodiment is about 53 Ω;

[0064] The grounded coplanar waveguide structure of this embodiment has three layers of grounding vias. The diameter of the grounding vias is 0.05 mm, the spacing between the grounding vias in the same layer is 0.1 mm, and the spacing between the grounding vias in each layer is 0.1 mm;

[0065] In the grounded coplanar waveguide structure of this embodiment, the signal line is split into two, the width of each split signal line is 0.1 mm, and the spacing between each split signal line is 0.1 mm;

[0066] Use electromagnetic simulation software to build a model, and the simulation shows that the impedance of the split signal line part of the port in the grounded coplanar waveguide structure of this embodiment is about 55 Ω;

[0067] Use electromagnetic simulation software to build a model, as Figure 5 shown, the insertion loss S21 and return loss S11 of the grounded coplanar waveguide structure of this embodiment are obtained by simulation. Since the radiation loss will gradually increase with the increase of frequency, the insertion loss S21 of the traditional coplanar waveguide will decrease rapidly with the increase of frequency, while the decrease of the insertion loss S21 of this new coplanar waveguide is not obvious, indicating that the optimization of the grounding vias reduces the radiation loss. The insertion loss S21 of the grounded coplanar waveguide in this embodiment is higher than -1.3 dB within 70 - 100 GHz, and the return loss S11 is lower than -20 dB within 70 - 98 GHz. The grounded coplanar waveguide structure of this embodiment can meet the requirements of the ferromagnetic resonance test system.

[0068] It can be understood that the present invention is described through some embodiments. Those skilled in the art know that without departing from the spirit and scope of the present invention, various changes or equivalent replacements can be made to these features and embodiments. In addition, under the teaching of the present invention, these features and embodiments can be modified to adapt to specific situations and materials without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application belong to the scope protected by the present invention.

Claims

1. A grounded coplanar waveguide with low radiation loss and high signal uniformity, characterized in that: The grounded coplanar waveguide includes a bottom metal grounding layer, a dielectric substrate, a grounding through hole, a signal line, a split signal line, and metal grounding layers on both sides; the dielectric substrate is arranged above the metal grounding layer, and metal grounding layers on both sides are arranged above the two sides of the dielectric substrate, and the metal grounding layers on both sides are respectively provided with more than two columns of grounding through holes to form a through hole array, and the grounding through holes in each column are arranged alternately, and a split signal line is arranged at the middle position above the dielectric substrate, and signal lines are respectively connected to signal lines at both ends of the split signal line, and one end of the signal line at both ends of the split signal line is connected to the signal input end, and the other end is connected to the signal output end; the signal line and the split signal line can be connected with equal width, or can be connected with unequal width through a transition line structure; the bottom metal grounding layer and the metal grounding layers on both sides are connected through grounding through holes.

2. The grounded coplanar waveguide with low radiation loss and high signal uniformity according to claim 1, characterized in that: The thickness of the bottom metal ground plane should be greater than three times the metal skin depth at the lowest operating frequency.

3. The grounded coplanar waveguide with low radiation loss and high signal uniformity according to claim 1, characterized in that: The signal lines at the input and output ends of the grounded coplanar waveguide meet impedance matching requirements, and the signal lines and the split signal lines meet impedance matching requirements.

4. The grounded coplanar waveguide with low radiation loss and high signal uniformity according to claim 1, characterized in that: The spacing between ground vias in the same column uses the minimum value allowed by the process, and the spacing between ground vias in each column is greater than the via radius.

5. The grounded coplanar waveguide with low radiation loss and high signal uniformity according to claim 1, characterized in that: Split the signal line length to be greater than one quarter wavelength of the lowest frequency used.

6. The grounded coplanar waveguide with low radiation loss and high signal uniformity according to claim 1, characterized in that: The material of the dielectric substrate has high mechanical stability and low dielectric constant and loss tangent.

7. The grounded coplanar waveguide with low radiation loss and high signal uniformity according to claim 1, characterized in that: The bottom metal ground layer, signal line, split signal line and metal ground layers on both sides are made of high conductivity materials.

8. The grounded coplanar waveguide with low radiation loss and high signal uniformity according to claim 1, characterized in that: The surfaces of the signal lines, split signal lines, metal ground layers on both sides, and the bottom metal ground layer are gold plated.

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