A suspended microstrip line based coplanar waveguide-coaxial transition

Abstract

The application discloses a kind of coplanar waveguide-coaxial transition based on suspended microstrip line, belong to microwave millimeter wave technical field.The transition includes radio frequency coaxial structure, air cavity, coplanar waveguide and L type metal carrier;Wherein, radio frequency coaxial structure and the longitudinal section of L type metal carrier are processed as a whole, and central conductor is extended to form metal probe;Coplanar waveguide structure is placed above the transverse section of L type metal carrier, and the part connected with metal probe is set to gradually change suspended microstrip structure.The application adopts the transition structure of gradually changing suspended microstrip line again to coaxial by coplanar waveguide, by setting gradually changing air cavity below suspended microstrip line, eliminate the adverse effects of assembly gap due to assembly process and machining precision, compensate the mismatch introduced by electromagnetic wave mode change and the impedance discontinuity caused by the existence of assembly gap, so as to realize the transmission of high frequency signal;It also has the advantages of low loss, ultra wide band, simple structure and easy processing.

Description

Technical Field

[0001] This invention belongs to the field of microwave and millimeter-wave technology, specifically relating to an ultrawideband coplanar waveguide-coaxial transition device based on a gradient suspended microstrip line. Background Technology

[0002] In the millimeter-wave band, coaxial structures are widely used for connections between RF modules. Coaxial cables and connectors, in particular, are widely used in medium- to long-distance millimeter-wave transmission due to their high bandwidth and small size. Inside the RF module, coaxial connectors can connect to microstrip circuits via RF insulators. With the development of communication RF technology, the requirements for miniaturization and lightweight design of modules are becoming increasingly stringent.

[0003] Coplanar waveguides are high-performance, easy-to-fabricate microwave planar transmission lines, also known as coplanar microstrip transmission lines. They are widely used in hybrid microwave integrated circuits and monolithic integrated circuits, and are easily integrated with other passive and active microwave circuits, enabling the integration of microwave components and systems. Therefore, research on coplanar waveguide / coaxial converter structures is essential.

[0004] In the low-frequency band, the typical connection method for coplanar waveguide-to-coaxial converters is to directly solder the inner conductor of the coaxial cable onto the metal conductor of the coplanar waveguide, while the outer conductor and the ground of the coplanar waveguide are mounted together. This structure has minimal impact on the standing wave ratio (SWR) and insertion loss of the converter interface in the low-frequency band. However, due to assembly process and precision issues, an air gap inevitably exists between the coaxial cable and the coplanar waveguide. If such an air gap occurs in the high-frequency band, it will significantly affect the transmission performance of the entire structure. Therefore, designing a coplanar waveguide-to-coaxial structure with ultra-wide bandwidth, low loss, and high efficiency is of great help in improving the performance of millimeter-wave RF module circuits. Summary of the Invention

[0005] In view of the above background technology, the present invention proposes an ultra-wideband, low-loss, structurally smooth, and easy-to-manufacture transition device based on a suspended microstrip line coplanar waveguide to coaxial line.

[0006] The technical solution adopted in this invention is:

[0007] A coplanar waveguide-to-coaxial transition device based on a suspended microstrip line is characterized by comprising: a radio frequency coaxial structure, an air cavity, a coplanar waveguide, and an L-shaped metal carrier.

[0008] The L-shaped metal carrier is composed of a longitudinal section and a transverse section, wherein a gradient air cavity is provided at the connection between the transverse section and the longitudinal section.

[0009] The radio frequency coaxial structure includes an outer insulating dielectric and a central conductor; the radio frequency coaxial structure extends through the longitudinal section of the L-shaped metal carrier, and the central conductor extends towards the front end to form a metal probe arranged parallel to the transverse section.

[0010] The coplanar waveguide structure is placed above the transverse section of the L-shaped metal carrier.

[0011] The coplanar waveguide structure includes a dielectric substrate, a ground layer disposed on the lower surface of the dielectric substrate, and a gradient metal patch, a rectangular metal patch, and an upper ground patch disposed on the upper surface of the dielectric substrate. The gradient metal patch is located directly above the gradient air cavity, and the corresponding area on the lower surface of the dielectric substrate does not have a ground layer, forming a suspended microstrip structure. One end of the gradient metal patch near the longitudinal section coincides with the edge of the dielectric substrate, and the other end extends to the other side of the dielectric substrate through the rectangular metal patch. The upper ground patch is disposed on both sides of the rectangular metal patch, and a uniform gap is provided between the upper ground patch and the rectangular metal patch.

[0012] The metal probe is attached to the upper surface of the gradient metal patch and fixed by welding.

[0013] Furthermore, the gradient metal patch and the gradient air cavity include, but are not limited to, stepped, trapezoidal, and exponential types.

[0014] Furthermore, the metal probe has a diameter of 0.23 mm or 0.3 mm and a length between 0.5 mm and 1.5 mm.

[0015] Furthermore, the impedance of both the coplanar waveguide and the radio frequency coaxial structure is 50 ohms.

[0016] Furthermore, the insulating medium of the radio frequency coaxial structure is made of glass.

[0017] Compared with the prior art, the beneficial effects of the present invention are:

[0018] 1. This invention integrates the radio frequency coaxial structure with an L-shaped metal carrier, making the L-shaped metal carrier the outer conductor of the radio frequency coaxial structure for a more stable connection with the coplanar waveguide; at the same time, the outer layer of the radio frequency coaxial structure is connected to the ground layer of the coplanar waveguide to maintain a consistent potential.

[0019] 2. This invention utilizes a transition structure that transforms a coplanar waveguide into a graded suspended microstrip line and then into a coaxial line. By setting a graded air cavity below the suspended microstrip line, it eliminates the adverse effects of assembly gaps caused by assembly process and precision issues, compensates for the mismatch introduced by the electromagnetic wave mode transition, and compensates for the impedance discontinuity caused by the assembly gap, thereby enabling the transmission of high-frequency signals.

[0020] 3. The present invention also has the advantages of low loss, ultra-wide bandwidth, and simple structure and easy processing of RF module port conversion. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the overall transition structure of the coplanar waveguide to coaxial structure of the present invention.

[0022] Figure 2 This is a top view of the transition structure of the coplanar waveguide to coaxial structure of the present invention.

[0023] Figure 3 This is a side view of the transition structure of the coplanar waveguide to coaxial structure of the present invention.

[0024] Figure 4 This is a graph showing the S-parameters of the transition structure from coplanar waveguide to coaxial in this invention.

[0025] Figure 5 The S-parameter curves are for a transition structure without an intermediate microstrip line suspension.

[0026] The following are the symbols in the attached diagram: 1. RF coaxial structure, 2. Metal probe, 3. Stepped gradient metal patch, 4. Rectangular metal patch, 5. Dielectric board, 6. Ground layer, 7. L-shaped metal carrier, 8. Stepped gradient air cavity, 9. Upper ground patch, 10. Assembly gap. Detailed Implementation

[0027] To better illustrate the purpose, advantages, and technical concepts of this invention, the technical solutions of this invention will be clearly and completely described below in conjunction with the accompanying drawings and specific examples. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. The components of the embodiments of this invention described and shown in the accompanying drawings can be arranged and designed in various different configurations. Therefore, it should be noted that the specific examples given below are only for explaining and illustrating this invention, and the scope of protection of this invention is not limited to what is described below.

[0028] Figure 1 This is a schematic diagram of the overall structure of an embodiment of the present invention, as shown below. Figure 1 As shown, the structure includes: a radio frequency coaxial structure, a stepped gradient air cavity, a coplanar waveguide, and an L-shaped metal carrier.

[0029] The L-shaped metal carrier is composed of a longitudinal section and a transverse section, wherein a stepped, gradually changing air cavity is provided at the connection between the transverse section and the longitudinal section.

[0030] The radio frequency coaxial structure includes an outer insulating dielectric and a central conductor; the radio frequency coaxial structure penetrates the longitudinal section of the L-shaped metal carrier, and the central conductor extends towards the front end to form a metal probe arranged parallel to the transverse section. In this embodiment, the metal probe has a diameter of 0.23 mm and a length of 1 mm.

[0031] The coplanar waveguide structure is placed above the transverse section of the L-shaped metal carrier.

[0032] The coplanar waveguide structure includes a dielectric substrate, a ground layer disposed on the lower surface of the dielectric substrate, and a stepped gradient metal patch, a rectangular metal patch, and an upper ground patch disposed on the upper surface of the dielectric substrate. The stepped metal patch is located directly above the stepped air cavity, and the corresponding area on the lower surface of the dielectric substrate does not have a ground layer, forming a suspended microstrip structure. One end of the stepped metal patch near the longitudinal section coincides with the edge of the dielectric substrate, and the other end extends to the other side of the dielectric substrate through the rectangular metal patch. The upper ground patch is disposed on both sides of the rectangular metal patch, and a uniform gap of 0.5 mm is provided between the upper ground patch and the rectangular metal patch.

[0033] The metal probe is attached to the upper surface of the gradient metal patch and fixed by welding.

[0034] Figure 2 This is a top view of an embodiment of the present invention. (See figure.) Figure 2 As shown, the upper and lower bottom line widths of the gradient metal patch in the gradient suspended microstrip line are consistent with the width of the rectangular metal patch, which is 0.35mm. The lower bottom length of the part near the coaxial section is 2.5mm. The length and width of each step gradient are the same.

[0035] Figure 3 This is a side view of an embodiment of the present invention. It should be noted that, in order to better demonstrate that the present invention can effectively eliminate the adverse effects caused by assembly gaps, in this embodiment, the longitudinal section of the dielectric plate and the metal carrier is provided with an assembly gap width of 0.2 mm, the maximum height of the stepped air cavity below the dielectric plate is 0.72 mm, and the length is consistent with the length of the gradient suspended microstrip line, both being 1 mm. The length and height of each step of the stepped air cavity are the same.

[0036] The signal is transmitted to the tapered suspension microstrip line through a coplanar waveguide, and then converted from the tapered suspension microstrip line with gradually increasing linewidth to the coaxial structure. The air gap that was originally caused by assembly process and precision issues is transformed into the lower air layer in the suspension microstrip line design, which compensates for the mismatch introduced by electromagnetic wave mode conversion and impedance discontinuity.

[0037] The entire simulation model was built in the simulation software to verify the performance of this embodiment. Figure 4 This is the S-parameter diagram of the transition in this embodiment. Figure 5 The S-parameters are those of the transition structure without the gradient suspended microstrip line. A comparison of the two figures shows that the transmission performance is significantly better with the addition of the suspended microstrip line. Figure 4 The S11 operates below -20dB in the 0-40GHz range, with a bandwidth of 40GHz. Figure 5The bandwidth in this embodiment is only about 16GHz. In terms of transmission efficiency, the transmission parameter S21 of the transition structure in this embodiment is almost zero in the range of 0-40GHz, resulting in low loss.

[0038] The results show that the coplanar waveguide-to-coaxial transition structure provided by this invention has the advantages of ultra-wide bandwidth, low loss, smooth structural transition, and ease of fabrication. It offers a new method to address the problems of discontinuity, impedance mismatch, air gaps, and large reflections in coplanar waveguide-to-coaxial structures.

[0039] The above examples are only for illustrating the technical concept and features of the present invention, and are only used to specifically describe the present invention so that those skilled in the art can understand the content of the present invention and implement it accordingly. They should not be used to limit the scope of protection of the present invention. All equivalent changes or modifications made according to the content of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A coplanar waveguide-to-coaxial transition device based on a suspended microstrip line, characterized in that, include: Radio frequency coaxial structure, air cavity, coplanar waveguide and L-shaped metal carrier; The L-shaped metal carrier is composed of a longitudinal section and a transverse section, wherein a gradient air cavity is provided at the connection between the transverse section and the longitudinal section. The radio frequency coaxial structure includes an outer insulating dielectric and a central conductor; the radio frequency coaxial structure penetrates the longitudinal section of the L-shaped metal carrier, and the central conductor extends towards the front end to form a metal probe arranged parallel to the upper part of the transverse section; The coplanar waveguide structure is placed above the transverse section of the L-shaped metal carrier; The coplanar waveguide structure includes a dielectric substrate, a ground layer disposed on the lower surface of the dielectric substrate, and a gradient metal patch, a rectangular metal patch, and an upper ground patch disposed on the upper surface of the dielectric substrate. The gradient metal patch is located directly above the gradient air cavity, and the corresponding area on the lower surface of the dielectric substrate does not have a ground layer, forming a suspended microstrip structure. One end of the gradient metal patch near the longitudinal section coincides with the edge of the dielectric substrate, and the other end extends to the other side of the dielectric substrate through the rectangular metal patch. The upper ground patch is disposed on both sides of the rectangular metal patch, and a uniform gap is provided between the upper ground patch and the rectangular metal patch. The metal probe is attached to the upper surface of the gradient metal patch and fixed by welding.

2. The coplanar waveguide-to-coaxial transition device based on a suspended microstrip line as described in claim 1, characterized in that, The gradient metal patch and the gradient air cavity are stepped, trapezoidal, or exponential in shape.

3. The coplanar waveguide-to-coaxial transition device based on a suspended microstrip line as described in claim 2, characterized in that, The metal probe has a diameter of 0.23 mm or 0.3 mm and a length between 0.5 mm and 1.5 mm.

4. The coplanar waveguide-to-coaxial transition device based on a suspended microstrip line as described in claim 3, characterized in that, The impedance of both the coplanar waveguide and the radio frequency coaxial structure is 50 ohms.

5. A coplanar waveguide-to-coaxial transition device based on a suspended microstrip line as described in claim 3, characterized in that, The insulating medium of the radio frequency coaxial structure is made of glass.

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