De-embedding microstrip line structure and calibration clamp applying same
By introducing a deembedded microstrip line structure with chamfered transition segment connection into the microstrip line structure, the problem of redundant part parasitic effect in microstrip line transmission in high-frequency band is solved, and efficient transmission quality improvement and cost reduction are achieved.
Patent Information
- Application Number
- CN202411933431.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-26
- Publication Date
- 2025-04-08
AI Technical Summary
The prior art is difficult to effectively remove the parasitic effects of redundant parts in microstrip line transmission in high frequency bands, affecting test results and parameter extraction, and expensive welding-free adapters are expensive and difficult to popularize.
The de-embedded microstrip line structure is adopted, including a microstrip line connected in sequence along the length direction and at least one level of grounded coplanar waveguide. It is connected by a chamfer transition section to ensure that the line width of the microstrip line is larger than that of the grounded coplanar waveguide. The grounded coplanar waveguides of adjacent stages are connected by a chamfer transition section to reduce discontinuity and impedance mismatch.
Without rectification of the SMA adapter, the microstrip line transmission quality is improved, the loss is reduced, and the accurate de-embedding and calibration of components is achieved, with good economic benefits.
Smart Images
Figure CN119786928A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the field of component calibration, and in particular to a de-embedded microstrip line structure and a calibration fixture using the same. Background Art
[0002] With the continuous development of high-speed and highly integrated electronic and electrical systems, miniaturized components such as surface mount devices (SMDs) are widely used on printed circuit boards (PCBs). Usually, SMD components are soldered on pads and connected to each other through traces such as microstrip lines (ML) or coplanar waveguides with ground (CPWG). When used in high-frequency bands, due to the shortening of the electrical wavelength, components will gradually show stronger nonlinear characteristics, and their parameters are difficult to characterize. Traces, pads, and packages may produce parasitic effects that interfere with their true characteristics. This is also the reason why it is difficult to model and characterize parameters of microelectronic products in the RF and millimeter wave bands up to GHz. Accurate characterization of SMD components is crucial to the reliability of microwave design.
[0003] Various calibration algorithms have been developed and applied to the parameter characterization of micro components, but the calibration effect is more dependent on the transmission performance of the calibration parts, so the design of high-frequency through-fixtures has always been the focus of research. Figure 1 As shown, the DUT is connected to a vector network analyzer (VNA) via a coaxial cable and a corresponding adapter. Figure 1 The dotted line in the middle is the area to be calibrated. The parameters that need to be measured (obtained) are only the part in the dotted line. The parameters from the left adapter to the left dotted line and from the right adapter to the right dotted line are not needed. Under DC or low-frequency power supply excitation, the parameters of the two redundant parts on the left and right can be ignored. However, when the high frequency reaches above GHz, the redundant part is no longer a simple wire, but each small section is a small component. The parameters of these small components are embedded in the entire measurement results during testing, so calibration is required (the results of the redundant parts are removed). That is, under high-frequency excitation, the PCB traces, adapters and solder used to connect the DUT test fixture will cause parasitic effects, affecting the test results and parameter extraction. In the implementation process of parasitic removal and de-embedding, the transmission quality of the calibration fixture plays a decisive role, and the parasitic effects generated by the transition from coaxial to PCB are also important influencing factors.
[0004] In recent years, the academic community has conducted extensive research on the structural optimization and improvement of coaxial RF connectors to reduce insertion loss, minimize parasitic effects, and improve transmission quality. P. Li proposed a circuit model for coaxial to microstrip transition, which can analyze its radiation and power consumption from the perspective of mathematical equations. In order to improve transmission quality, various expensive solder-free adapters are also widely used to avoid parasitic effects caused by irregular solder. H. Votsi demonstrated experimental verification of horizontal solder-free SMA adapters up to 40GHz. P. The application of vertical solderless coaxial to PCB adapters up to 67 GHz is introduced. Low-loss, solderless adapters are usually very expensive. As experimental consumables, these adapters are a huge expense that not every research institution or funding project can support. In view of this, it is also meaningful to improve the structure of the adapter and optimize the calibration traces. ESLi removed the contact pins of the coaxial to microstrip adapter to reduce parasitic effects [8]. J.Cheng replaced the grounding part with a metal flange structure embedded in the PCB [9]. These methods are effective to a certain extent, but at the same time they will incur considerable modification costs and are difficult to mass produce.
[0005] Therefore, in the application of ordinary coaxial adapters, it is urgent to find an optimization solution that can improve the transmission quality of microstrip lines without modifying the adapter structure. Summary of the invention
[0006] The technical problem to be solved by the present invention is to overcome the defects of the prior art and provide a de-embedded microstrip line structure, which can improve the transmission quality and reduce the loss without modifying the SMA adapter.
[0007] In order to solve the above technical problems, the technical solution of the present invention is: a de-embedded microstrip line structure, comprising a microstrip line and at least one level of grounded coplanar waveguide connected in sequence along the length direction; wherein,
[0008] The line width of the microstrip line is greater than the line width of the grounded coplanar waveguide, and the microstrip line is connected to the grounded coplanar waveguide through a chamfered transition section;
[0009] When the number of the grounded coplanar waveguides is greater than one, in two adjacent grounded coplanar waveguides, the line width of the outer level is smaller than the line width of the inner level, and the adjacent grounded coplanar waveguides are also connected by a chamfered transition section.
[0010] Furthermore, the angle of the chamfered transition section is 45 to 60 degrees.
[0011] Furthermore, the length of the chamfered transition section is 0.6 mm.
[0012] The present invention also provides a calibration fixture, comprising a PCB board, an SMA adapter and a de-embedded microstrip line structure; wherein:
[0013] The de-embedded microstrip line structure and the device under test are respectively configured on the surface of the PCB board;
[0014] The microstrip line end of the de-embedded microstrip line structure is electrically connected to the device under test, and the grounded coplanar waveguide end is electrically connected to the needle of the SMA adapter.
[0015] In order to further eliminate the antenna effect generated when the SMA adapter is not structurally adjusted, the metal layer of the PCB board that contacts the contact pins of the SMA adapter is arranged with a plurality of ground vias near the contact pins and the needle.
[0016] Furthermore, the needle is placed in the outermost grounded coplanar waveguide, and the outermost grounded coplanar waveguide completely covers the needle.
[0017] Furthermore, the grounded coplanar waveguide has a first level, the width of the microstrip line is 2.14 mm, the line width of the grounded coplanar waveguide is 0.9 mm, and the gap width between the grounded coplanar waveguide and the metal layer of the PCB board in contact with the contact pins of the SMA adapter is 0.11 mm.
[0018] Furthermore, the grounded coplanar waveguide has two stages, the outer stage is the first stage, and the inner stage is the second stage; wherein,
[0019] The width of the microstrip line is 2.14 mm;
[0020] The line width of the first-level grounded coplanar waveguide is 0.9 mm, and the gap width between the metal layer of the PCB board that contacts the contact pins of the SMA adapter is 0.34 mm;
[0021] The line width of the second-level grounded coplanar waveguide is 1.6 mm, and the gap width between the metal layer of the PCB board in contact with the contact pins of the SMA adapter is 0.11 mm.
[0022] After adopting the above technical solution, the present invention can achieve good transmission quality without complex and expensive coaxial adapter structure modification, can accurately de-embed and calibrate components, and has good economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS
[0023] Figure 1 This is a schematic diagram of the traditional test device on the microstrip line;
[0024] Figure 2 is a schematic structural diagram of a calibration fixture in Embodiment 1 of the present invention;
[0025] Figure 3 is a schematic structural diagram of a calibration fixture in Embodiment 2 of the present invention;
[0026] Figure 4 Graphs showing simulation results of two embodiments of the present invention;
[0027] Figure 5 It is a structural schematic diagram of the calibration fixture in comparative example 1;
[0028] Figure 6 It is a structural schematic diagram of the calibration fixture in comparative example 2;
[0029] Figure 7 The simulation results of two comparative examples are shown in FIG.
[0030] In the figure, 1, microstrip line; 2, grounded coplanar waveguide; 3, chamfered transition section; 4, PCB board; 41, metal layer; 5, SMA adapter; 51, contact pin; 52, needle; 6, ground via. DETAILED DESCRIPTION
[0031] In order to make the contents of the present invention more clearly understood, the present invention is further described in detail below based on specific embodiments in conjunction with the accompanying drawings.
[0032] like Figure 2 and Figure 3 As shown, a de-embedded microstrip line structure comprises a microstrip line 1 and at least one level of grounded coplanar waveguide 2 connected in sequence along the length direction; wherein,
[0033] The line width of the microstrip line 1 is greater than the line width of the grounded coplanar waveguide 2, and the microstrip line 1 is connected to the grounded coplanar waveguide 2 through a chamfered transition section 3;
[0034] When the number of the grounded coplanar waveguides 2 is greater than one, in two adjacent grounded coplanar waveguides 2 , the line width of the outer stage is smaller than the line width of the inner stage, and the adjacent grounded coplanar waveguides 2 are also connected by the chamfered transition section 3 .
[0035] In this embodiment, the angle of the chamfered transition section 3 is 45-60°, which is determined based on simulation results.
[0036] like Figure 2 and Figure 3 As shown, a calibration fixture includes a PCB board 4, an SMA adapter 5 and the de-embedded microstrip line structure involved in the above embodiment; wherein,
[0037] The de-embedded microstrip line structure and the device under test are respectively arranged on the surface of the PCB board 4;
[0038] The microstrip line end of the de-embedded microstrip line structure is electrically connected to the device under test, and the grounded coplanar waveguide end is electrically connected to the needle 52 of the SMA adapter 5 .
[0039] In this embodiment, if Figure 2and Figure 3 As shown, the metal layer 41 of the PCB board 4 that contacts the contact pins 51 of the SMA adapter 5 has a plurality of ground vias 6 arranged near the contact pins 51 and the needle 52. The ground vias 6 can eliminate the antenna effect generated when the SMA adapter 5 is not structurally adjusted.
[0040] In this embodiment, if Figure 2 and Figure 3 As shown, the needle 52 is placed in the outermost grounded coplanar waveguide 2 , and the outermost grounded coplanar waveguide 2 completely covers the needle 52 , and the length is approximately equal to the length of the needle 52 , so as to reduce the discontinuity caused by the needle 52 .
[0041] The solutions involved in the above embodiments are described in detail below in conjunction with specific embodiments.
[0042] Embodiment 1
[0043] like Figure 2 As shown, a calibration fixture includes a PCB board 4, an SMA adapter 5 and a de-embedded microstrip line structure, wherein the de-embedded microstrip line structure and the device under test are respectively arranged on the surface of the PCB board 4; the microstrip line end of the de-embedded microstrip line structure is electrically connected to the device under test, and the grounded coplanar waveguide end is electrically connected to the needle 52 of the SMA adapter 5. The grounded coplanar waveguide 2 has a first level, the width of the microstrip line 1 is 2.14 mm, the line width of the grounded coplanar waveguide 2 is 0.9 mm, and the gap width between the grounded coplanar waveguide 2 and the metal layer 41 of the PCB board 4 contacting the contact pin 51 of the SMA adapter 5 is 0.11 mm.
[0044] Embodiment 2
[0045] like Figure 3 As shown, a calibration fixture includes a PCB board 4, an SMA adapter 5 and a de-embedded microstrip line structure, wherein the de-embedded microstrip line structure and the device under test are respectively arranged on the surface of the PCB board 4; the microstrip line end of the de-embedded microstrip line structure is electrically connected to the device under test, and the grounded coplanar waveguide end is electrically connected to the needle 52 of the SMA adapter 5. The grounded coplanar waveguide 2 has two levels, the outer level is the first level, and the inner level is the second level; wherein the width of the microstrip line 1 is 2.14mm; the line width of the first-level grounded coplanar waveguide 2 is 0.9mm, and the gap width between the metal layer 41 of the PCB board 4 and the contact pin 51 of the SMA adapter 5 is 0.34mm; the line width of the second-level grounded coplanar waveguide 2 is 1.6mm, and the gap width between the metal layer 41 of the PCB board 4 and the contact pin 51 of the SMA adapter 5 is 0.11mm. Such a two-stage grounded coplanar waveguide 2 can reduce the discontinuity and impedance mismatch caused by a single-stage conversion from the grounded coplanar waveguide 2 to the microstrip line 1 .
[0046] Figure 4The simulation results of Example 1 and Example 2 are shown in Figure 1. Due to the presence of ground vias, compared with the original microstrip line, the transmission loss of Example 1 (CPWG-ML) does not drop sharply when approaching 30GHz, and the insertion loss is above -2dB. Compared with Example 1 (CPWG-ML), Example 2 (CPWG1-CPWG2-ML) performs better at high frequencies, and its insertion loss value is slightly higher, because the CPWG structure is more suitable for high-frequency transmission.
[0047] Comparative Example 1
[0048] like Figure 5 As shown, the original microstrip line 1 is used to realize signal transmission between the device under test and the SMA adapter 5, and in order to prevent the occurrence of antenna effect, the two contact pins 51 of the SMA adapter 5 are also removed.
[0049] Embodiment 2
[0050] like Figure 6 As shown, on the one hand, in order to prevent the risk of short circuit between the microstrip line 1 and the SMA adapter 5 (if the substrate of the PCB board 4 is not thin, such as a 1.6 mm thick RO4350B board, the trace width of the microstrip line reaches 3.5 mm, which will make the SMA adapter unsuitable and there is a risk of short circuit); on the other hand, in order to reduce the discontinuity between the SMA adapter and the PCB board 4 and minimize the insertion loss, a chamfered transition section 3 is provided at the position where the microstrip line is connected to the needle 52 of the SMA adapter 5.
[0051] Figure 7 The simulation result diagram of Example 1 and Example 2 shows that in Example 1, in order to prevent the occurrence of antenna effect, the two contact pins 51 of the SMA adapter 5 are removed. In Example 2, a chamfered transition section 3 is set at the connection between the microstrip line 1 and the SMA adapter 5. It can be seen from the simulation results that when the frequency reaches about 22 GHz, the loss of the original microstrip line (Comparative Example 1) will deteriorate, while the loss of the microstrip line 1 with the chamfered transition section 3 (Comparative Example 2) is relatively low, but the microstrip line 1 with the chamfered transition section 3 (Comparative Example 2) will still drop to -3dB at around 23 GHz. The result is not good enough and still needs further improvement. However, Example 2 also illustrates the effectiveness of the chamfered transition section 3 to a certain extent.
[0052] It should be noted that in Example 1, Example 2, Comparative Example 1 and Comparative Example 2, the material of the PCB board 4 is RO4350B, and the relative dielectric constant is ε r=3.66, the substrate thickness is h=1mm, and the thickness of the upper trace (de-embedded microstrip line structure) and the metal layer 41 are both t=35μm. The line width of the microstrip line 1 is w=2.2mm, the outer diameter of the SMA coaxial adapter 5 is 3.86mm, the inner diameter is 0.8mm, and the relative dielectric constant of the dielectric material is 3.55. The line width of the microstrip line 1, the gap and line width of the grounded coplanar waveguide 3 are all calculated by the two parameters of relative dielectric constant and plate thickness. The calculation method is the existing technology and will not be described in detail here. Of course, the values of the substrate thickness and dielectric constant are not limited to this, and can also be other values.
[0053] By comparing the first embodiment, the second embodiment, the first comparative example and the second comparative example, the simulation results of the first embodiment and the second embodiment are better, and the entire optimization method of the present invention is proved to be useful, especially if the line width of the microstrip line 1 is wide due to the height of the PCB board 4, then the transmission line design of two or more levels of grounded coplanar waveguide 2 will be a good choice, which will not lead to a large difference in line width between two adjacent sections. Because if the line width difference between the beginning and the end of the transition section is too large, the continuity will be deteriorated.
[0054] Moreover, the structure in this patent can also generate significant economic benefits. First, although this de-embedded microstrip line structure may slightly increase the complexity of manufacturing, PCB board processing is relatively easy to mass-produce, and the established 3D simulation model can provide an imported document for PCB design. Secondly, based on this de-embedded microstrip line structure, the ordinary SMA adapter 5 can be used as a coaxial to microstrip transition application, eliminating the need for expensive solderless adapters or more complex flange structure modifications. Third, if low loss is pursued, the thinner the thickness of the dielectric board, the better the transmission quality, but the structure is also more prone to deformation and bending. There is solder reinforcement between the contact pins 51 that are not removed in this calibration fixture and the metal layer 41 of the PCB board 4, which can enhance the stability of the entire structure, thereby improving the strength and service life of the calibration piece. Fourth, when applied to a dielectric board with the same material and thickness parameters, the line width of the microstrip line 1 is very wide, and various standard or non-standard pads can be applied in the test of the DUT.
[0055] Based on the above ideal embodiments of the present invention, the relevant staff can make various changes and modifications without departing from the technical concept of the present invention through the above description. The technical scope of the present invention is not limited to the contents of the specification, and its technical scope must be determined according to the scope of the claims.
Claims
1. A de-embedded microstrip line structure, characterized in that: It comprises a microstrip line (1) and at least one level of grounded coplanar waveguide (2) connected in sequence along a length direction; wherein: The line width of the microstrip line (1) is greater than the line width of the grounded coplanar waveguide (2), and the microstrip line (1) is connected to the grounded coplanar waveguide (2) via a chamfered transition section (3); When the number of stages of the grounded coplanar waveguide (2) is greater than one, in two adjacent stages of the grounded coplanar waveguide (2), the line width of the outer stage is smaller than the line width of the inner stage, and the adjacent stages of the grounded coplanar waveguide (2) are also connected via a chamfered transition section (3).
2. The de-embedded microstrip line structure according to claim 1, characterized in that: The angle of the chamfered transition section (3) is 45-60°.
3. The de-embedded microstrip line structure according to claim 1 or 2, characterized in that: The length of the chamfered transition section (3) is 0.6 mm.
4. A calibration fixture, characterized in that: It comprises a PCB board (4), an SMA adapter (5) and the de-embedded microstrip line structure according to any one of claims 1 to 3; wherein: The de-embedded microstrip line structure and the device under test are respectively arranged on the surface of the PCB board (4); The microstrip line end of the de-embedded microstrip line structure is electrically connected to the device under test, and the grounded coplanar waveguide end is electrically connected to the needle (52) of the SMA adapter (5).
5. The calibration fixture according to claim 4, characterized in that: The metal layer (41) of the PCB board (4) in contact with the contact pin (51) of the SMA adapter (5) has a plurality of grounding vias (6) arranged at positions close to the contact pin (51) and the needle (52).
6. The calibration fixture according to claim 4, characterized in that: The needle (52) is placed on the outermost grounded coplanar waveguide (2), and the outermost grounded coplanar waveguide (2) completely covers the needle (52).
7. The calibration fixture according to claim 4, characterized in that: The grounded coplanar waveguide (2) has a first level, the width of the microstrip line (1) is 2.14 mm, the line width of the grounded coplanar waveguide (2) is 0.9 mm, and the gap width between the grounded coplanar waveguide (2) and the metal layer (41) of the PCB board (4) in contact with the contact pin (51) of the SMA adapter (5) is 0.11 mm.
8. The calibration fixture according to claim 4, characterized in that: The grounded coplanar waveguide (2) has two stages, the outer stage being the first stage and the inner stage being the second stage; wherein: The width of the microstrip line (1) is 2.14 mm; The line width of the first-level grounded coplanar waveguide (2) is 0.9 mm, and the gap width between the metal layer (41) of the PCB board (4) in contact with the contact pin (51) of the SMA adapter (5) is 0.34 mm; The line width of the second-level grounded coplanar waveguide (2) is 1.6 mm, and the gap width between the metal layer (41) of the PCB board (4) in contact with the contact pin (51) of the SMA adapter (5) is 0.11 mm.