A stripline to coaxial transmission line transition

Abstract

The application discloses a transition structure from a stripline transmission line to a coaxial transmission line, which comprises a stripline, an upper shielding cavity communicated above the stripline, a lower shielding cavity communicated below the stripline, and a multilayer circuit board in which the upper shielding cavity, the stripline and the lower shielding cavity are arranged together, one side of the multilayer circuit board being electrically connected with a transition interface, the other side of the transition interface being electrically connected with a coaxial line, the transition interface comprising an interface floor, the middle part of the interface floor being provided with an insulating gap, the insulating gap being communicated with the upper shielding cavity, the stripline, the lower shielding cavity and the coaxial line. The transition interface is designed to realize the transition from the stripline inside the multilayer circuit board to the coaxial line on the sidewall of the multilayer circuit board; the insulating gap is arranged at the transition interface, and the transition gaps are arranged at the positions close to the transition interface between the upper inner floor and the lower inner floor to guide the electromagnetic field type to smoothly transit from the stripline field type to the coaxial field type, so that the advantages of good transmission standing wave and low loss are obtained.

Description

Technical Field

[0001] This invention relates to the field of multilayer radio frequency circuit technology, and in particular to a transition structure from stripline transmission line to coaxial transmission line. Background Technology

[0002] With the rapid development of the communications industry, the requirements for miniaturization, intelligence, multi-functionality, and high integration of microwave and millimeter-wave components are becoming increasingly stringent. Traditional two-dimensional planar circuits can no longer meet these needs, and multi-layer three-dimensional circuits are gradually becoming the mainstream.

[0003] In multilayer circuit technology, striplines are the most commonly used transmission lines. They consist of upper and lower ground planes and a conductor strip in the middle. The space between the conductor strip and the ground planes can be air or filled with other media to transmit TEM waves. Compared to microstrip lines, striplines have certain advantages in terms of characteristic impedance precision control and electromagnetic shielding characteristics.

[0004] Meanwhile, with advancements in multilayer circuit board manufacturing processes, methods such as high- and low-temperature co-fired ceramics and multilayer hybrid printed circuit boards have developed for sidewall circuitry. This means that functional circuits or components can be printed on the sidewalls of multilayer circuit boards, pushing multilayer circuits towards multilayer three-dimensional circuits. The sidewalls of multilayer circuit boards need electrical interaction with the internal circuitry to function, requiring a transition structure from the internal circuitry to the sidewall circuitry. Currently, there are many reports in the literature regarding transition structures from the internal circuitry to the upper and lower surfaces of multilayer circuit boards, but fewer reports on transition structures from the internal circuitry to the sidewall circuitry. Summary of the Invention

[0005] The purpose of this invention is to provide a transition structure from stripline transmission line to coaxial transmission line, which can achieve a high-performance transition from the internal circuitry to the sidewall circuitry of a multilayer circuit board.

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

[0007] A transition structure from a stripline transmission line to a coaxial transmission line includes a stripline, an upper shielding cavity connected above the stripline, and a lower shielding cavity connected below the stripline. The upper shielding cavity, the stripline, and the lower shielding cavity are collectively disposed within a multilayer circuit board. A transition interface is electrically connected to one side of the multilayer circuit board, and a coaxial line is electrically connected to the other side of the transition interface. The transition interface includes an interface ground plane, and an insulating notch is provided in the middle of the interface ground plane. The insulating notch is connected to the upper shielding cavity, the stripline, the lower shielding cavity, and the coaxial line.

[0008] Alternatively, the stripline includes an inner upper floor and an inner lower floor arranged in parallel and having a transition gap, with a signal line parallel to both the inner upper floor and the inner lower floor, and an insulating medium between the signal line and the inner upper floor and the inner lower floor.

[0009] Optionally, a plurality of strip-shaped shielding posts are provided between the inner upper floor and the inner lower floor, perpendicular to both of them, with the plurality of strip-shaped shielding posts respectively located on both sides of the signal line.

[0010] Alternatively, the transition gap is located on the side of the inner upper floor and inner lower floor near the transition interface, and the transition gap extends through the transition interface.

[0011] Alternatively, the insulation gap and the transition interface may meet at the edge of the insulation gap.

[0012] Alternatively, the upper shielding cavity includes a top floor disposed above the inner upper floor, and a plurality of upper shielding cavity shielding pillars are provided between the top floor and the strip line. The plurality of upper shielding cavity shielding pillars are distributed in a "U" shape, and the "U" shaped openings face the transition interface.

[0013] Alternatively, the lower shielding cavity includes a bottom floor located below the inner lower floor, and a plurality of lower shielding cavity shielding pillars are provided between the bottom floor and the strip line. The plurality of lower shielding cavity shielding pillars are distributed in a "U" shape, and the "U" shaped openings face the transition interface.

[0014] Alternatively, the coaxial cable includes an outer conductor, the insulating notch is located inside the outer conductor, an inner conductor is provided inside the outer conductor, and an insulating medium is provided between the outer conductor and the inner conductor.

[0015] Alternatively, a signal disk may be provided within the insulating notch.

[0016] Alternatively, the transition interface can be made of metal.

[0017] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0018] 1. The present invention provides a transition structure from stripline transmission line to coaxial transmission line, which designs a transition interface to realize the transition from stripline inside the multilayer circuit board to coaxial line on the side wall of the multilayer circuit board; an insulation gap is set at the transition interface, and a transition gap is set at the inner upper ground plane and the inner lower ground plane near the transition interface to guide the electromagnetic field mode to smoothly transition from stripline field mode to coaxial field mode, thereby obtaining the advantages of good transmission standing wave and low loss.

[0019] 2. The transition structure from stripline transmission line to coaxial transmission line provided by the present invention has two shielding cavities set at the upper and lower positions of the stripline near the transition interface to perform electromagnetic shielding of the transition electromagnetic field, thereby obtaining the advantage of good electromagnetic shielding characteristics. Attached Figure Description

[0020] The present invention will be described by way of example and with reference to the accompanying drawings, wherein:

[0021] Figure 1 This is a three-dimensional view of the direct transition structure from the stripline to the coaxial line of the present invention;

[0022] Figure 2 This is a planar schematic diagram of the direct transition structure from the stripline to the coaxial line of the present invention;

[0023] Figure 3 The simulation results show the direct transition structure from stripline to coaxial line of this invention.

[0024] The markings in the diagram are: 1-Strip line, 101-Signal line, 102-Strip line shielding post, 103-Inner upper floor, 104-Inner lower floor, 105-Transition gap, 2-Upper shielding cavity, 201-Upper shielding cavity shielding post, 202-Top floor, 3-Lower shielding cavity, 301-Lower shielding cavity shielding post, 302-Bottom floor, 4-Transition interface, 401-Signal disk, 402-Transition interface floor, 403-Insulation gap, 5-Coaxial line, 501-Inner conductor, 502-Outer conductor. Detailed Implementation

[0025] The present invention will now be described in detail with reference to the accompanying drawings.

[0026] All features disclosed in this specification, or all steps in all disclosed methods or processes, may be combined in any way, except for mutually exclusive features and / or steps.

[0027] Any feature disclosed in this specification, unless otherwise stated, may be replaced by other equivalent or similar features. That is, unless otherwise stated, each feature is merely one example of a series of equivalent or similar features.

[0028] A transition structure from stripline transmission line to coaxial transmission line, such as Figure 1-3As shown, the circuit includes a stripline 1, with an upper shielding cavity 2 connected above the stripline 1 and a lower shielding cavity 3 connected below the stripline 1. The upper shielding cavity 2, the stripline 1, and the lower shielding cavity 3 are all disposed within a multilayer circuit board. A transition interface 4 is electrically connected to one side of the multilayer circuit board, and a coaxial line 5 is electrically connected to the other side of the transition interface 4. The transition interface 4 includes an interface ground plane, and an insulating notch 403 is provided in the middle of the interface ground plane. The insulating notch 403 is connected to the upper shielding cavity 2, the stripline 1, the lower shielding cavity 3, and the coaxial line 5.

[0029] Specifically, stripline 1 is used to transmit signals within the multilayer circuit board; upper shielding cavity 2 and lower shielding cavity 3 are connected to stripline 1, allowing the signal of stripline 1 to diffuse vertically within a set range; upper shielding cavity 2, stripline 1, and lower shielding cavity 3 are all disposed within a multilayer circuit board, and can be directly integrated into the original multilayer circuit board without the need for a separate structure, thus ensuring the integration of the multilayer circuit board; transition interface 4 is used to connect stripline 1 and coaxial line 5, bringing together the internal circuits of the multilayer circuit board to the side wall, and allowing the signal of stripline 1 to diffuse smoothly to coaxial line 5 through insulating gap 403; coaxial line 5 serves as the signal line 101 of the side wall circuit, receiving the signal of stripline 1 and completing the transmission from the internal circuits of the multilayer circuit board to the side wall circuit.

[0030] In this design, stripline 1 has a flat structure, while coaxial line 5 has a circular structure. Their cross-sectional areas and shapes differ, making them incompatible, and direct connection would not achieve a smooth transition. The sudden increase in transmission cross-section would cause signal reflection and refraction, as well as changes in transmission impedance, leading to signal distortion, decreased signal quality, and the receiver's inability to correctly identify the signal. In this solution, the signals from both the upper and lower sides of stripline 1 first diffuse into the upper shielding cavity 2 and lower shielding cavity 3, and then connect to coaxial line 5 through the insulating gap 403 in the transition interface 4, thus achieving signal transmission from stripline 1 to coaxial line 5. Because the signal range of stripline 1 begins to diffuse before entering coaxial line 5, its range is closer to the cross-section of coaxial line 5, resulting in less and smoother changes upon entry. This reduces signal reflection and refraction, prevents signal distortion, and improves transmission performance. Furthermore, the signal generates electromagnetic radiation. When the signal from stripline 1 diffuses outward, this radiation propagates into the surrounding environment. If this radiation is not effectively controlled and constrained, the signal may lose energy due to radiation, leading to signal attenuation. It can also interfere with other devices and systems, causing unpredictable malfunctions or failures in electronic components, thus affecting the normal operation of the multilayer circuit board and even damaging it. In this solution, the upper shielding cavity 2 and the lower shielding cavity 3 are used to control the diffusion range of the stripline 1 signal, causing it to diffuse towards the cross-section of the coaxial line 5. This constrains the radiation of the stripline 1 signal, improving communication efficiency and range, maintaining signal quality and integrity, reducing the impact of electromagnetic radiation on the surrounding environment, and ensuring the stable and reliable operation of the multilayer circuit board. Further, the multilayer circuit board can be a hybrid printed circuit board, or a high- or low-temperature co-fired ceramic, or other circuit boards capable of realizing a multilayer circuit structure; the upper shielding cavity 2 and the lower shielding cavity 3 can be rectangular cavities, or cavities such as circular, elliptical, or irregular cavities; the insulating notch 403 can be hexagonal, quadrilateral, circular, elliptical, irregular, or other shapes.

[0031] In another specific embodiment, the stripline 1 includes an inner upper ground plane 103 and an inner lower ground plane 104 arranged in parallel and having a transition gap 105. A signal line 101 parallel to the inner upper ground plane 103 and the inner lower ground plane 104 is provided between them, and an insulating medium is provided between the signal line 101 and the inner upper ground plane 103 and the inner lower ground plane 104. The inner upper ground plane 103 and the inner lower ground plane 104 can shield external electromagnetic interference and reduce the radiation of the electromagnetic field inside the stripline 1. The signal of the stripline 1 can enter the upper shielding cavity 2 and the lower shielding cavity 3 through the transition gap 105 between the inner upper ground plane 103 and the inner lower ground plane 104. The signal line 101 is used to transmit signals within the circuit board. The dielectric constant of the insulating medium determines the characteristic impedance of the stripline 1.

[0032] In another specific embodiment, a plurality of strip-shaped shielding posts 102 are provided between the inner upper floor 103 and the inner lower floor 104, perpendicular to both. These strip-shaped shielding posts 102 are respectively located on both sides of the signal line 101. The strip-shaped shielding posts 102 can control and limit the electromagnetic wave radiation of the signal line 101 towards both sides, maintaining the quality and integrity of the signal in the transmission direction and reducing interference to surrounding components. Furthermore, the strip-shaped shielding posts 102 are made of a metallic material with good conductivity, effectively reflecting, absorbing, and canceling electromagnetic waves, thereby providing a good shielding effect. Specifically, the strip-shaped shielding posts 102 are distributed in a straight line at equal intervals and electrically connected to the inner upper floor 103 and the inner lower floor 104.

[0033] In another specific implementation, the transition gap 105 is located on the side of the inner upper floor 103 and inner lower floor 104 near the transition interface 4, and the transition gap 105 extends through the transition interface 4. Since the stripline 1 connects with the coaxial line 5 at the transition interface 4, setting the transition gap 105 close to the transition interface 4 allows the signal range of the stripline 1 to expand further as it approaches the transition interface 4, ensuring a smooth transition between the stripline 1 and the coaxial line 5. Preferably, the transition gap 105 gradually increases in size as it approaches the transition interface 4, for example, it can be triangular, semi-circular, or semi-elliptical, thereby gradually expanding the signal radiation range; of course, other shapes such as irregularities can also be adopted, and the size should be appropriately selected based on electromagnetic simulation.

[0034] In another specific implementation, the insulation gap 403 and the transition interface 4 intersect at the edge of the insulation gap 403. This allows the expanded signal range of the stripline 1 to match the insulation gap 403 in the transition interface 4, ensuring smooth signal transmission.

[0035] As another specific implementation, the upper shielding cavity 2 includes a top floor 202 disposed above the inner upper floor 103. A plurality of upper shielding cavity shielding pillars 201 are provided between the top floor 202 and the strip line 1. The plurality of upper shielding cavity shielding pillars 201 are distributed in a "U" shape, and the "U" shaped opening faces the transition interface 4.

[0036] As another specific implementation, the lower shielding cavity 3 includes a bottom floor 302 located below the inner lower floor 104. A plurality of lower shielding cavity shielding pillars 301 are provided between the bottom floor 302 and the strip line 1. The plurality of lower shielding cavity shielding pillars 301 are distributed in a "U" shape, and the "U" shaped opening faces the transition interface 4.

[0037] Since the signal expands towards the coaxial line 5 through the upper shielding cavity 2 and the lower shielding cavity 3, and the openings of the upper shielding cavity shielding pillar 201 and the lower shielding cavity shielding pillar 301 face the transition interface 4, they can be used to control and limit the signal transmission only to the transition interface 4, maintaining the quality and integrity of the signal in the transmission direction and reducing interference to surrounding components. The upper shielding cavity shielding pillar 301 is electrically connected to the top floor 202 and the inner upper floor 103 and is evenly distributed on the three sides of the upper shielding cavity 2 excluding the transition interface 4; the lower shielding cavity shielding pillar 301 is electrically connected to the bottom floor 302 and the inner lower floor 104 and is evenly distributed on the three sides of the lower shielding cavity 3 excluding the transition interface 4. To achieve a better electromagnetic shielding effect, the upper shielding cavity 2 and the lower shielding cavity 3 should be as small as possible.

[0038] In another specific embodiment, the coaxial line 5 includes an outer conductor 502, with an insulating notch 403 located inside the outer conductor 502. An inner conductor 501 is disposed within the outer conductor 502, and an insulating medium exists between the outer conductor 502 and the inner conductor 501. The outer conductor 502 serves to shield against external interference and reduce signal radiation; the signal from the stripline 1 can enter the outer conductor 502 through the insulating notch 403; the inner conductor 501 is used for signal transmission; and the dielectric constant of the insulating medium determines the characteristic impedance of the coaxial line 5.

[0039] Furthermore, one side of the interface floor is electrically connected to the top floor 202, the inner upper floor 103, the inner lower floor 104 and the bottom floor 302, and the other side of the interface floor is electrically connected to the outer conductor 502.

[0040] In another specific implementation, a signal disk is provided within the insulation gap 403. Specifically, one side of the signal disk 401 is electrically connected to the signal line 101, and the other side of the signal disk 401 is electrically connected to the inner conductor 501, enabling connection between the signal line 101 and the inner conductor 501. Furthermore, the size of the signal disk is larger than the cross-section of the signal line 101. Since the signal line 101 is very small, the signal disk can increase the contact area of ​​the signal line 101, facilitating docking with the inner conductor 501. The signal disk can be circular, square, irregular, or other shapes. To achieve good transmission characteristics, the insulation gap 403 and the signal disk 401 should be appropriately selected based on electromagnetic simulation.

[0041] In another specific implementation, the transition interface 4 is made of metal. This provides electromagnetic shielding, reduces electromagnetic interference, improves electromagnetic compatibility, and ensures that signals pass only through the insulation gap 403.

[0042] This invention is not limited to the specific embodiments described above. The invention extends to any new feature or combination disclosed in this specification, as well as any new method or process step or combination disclosed herein.

Claims

1. A stripline to coaxial transmission line transition structure, characterized by: The utility model provides a coaxial transition interface of strip line, including strip line (1), the upper side of strip line (1) is communicated with upper shielding cavity (2), the lower side of strip line (1) is communicated with lower shielding cavity (3), upper shielding cavity (2), strip line (1) and lower shielding cavity (3) are arranged in a multilayer circuit board together, one side of multilayer circuit board is electrically connected with a transition interface (4), the other side of transition interface (4) is electrically connected with a coaxial line (5), and transition interface (4) includes interface floor, the middle part of interface floor is provided with insulating gap (403), and insulating gap (403) is communicated with upper shielding cavity (2), strip line (1), lower shielding cavity (3) and coaxial line (5) all.

2. The stripline-to-coaxial transition of claim 1, wherein: The signal line (101) and the internal upper floor (103) and the internal lower floor (104) have an insulating medium therebetween.

3. The stripline-to-coaxial transition of claim 1, wherein: The internal upper floor (103) and the internal lower floor (104) are provided with a plurality of strip line shielding columns (102) arranged perpendicularly thereto, and the plurality of strip line shielding columns (102) are respectively arranged on both sides of the signal line (101).

4. The stripline-to-coaxial transition of claim 1, wherein: The insulating gap (403) and the transition interface (4) meet at the edge of the insulating gap (403).

5. The stripline-to-coaxial transition of claim 1, wherein: the first end of the coaxial line is connected to the second end of the stripline line by a via; and the second end of the coaxial line is connected to the first end of the coaxial line by a via. The upper shielding cavity (2) includes a top floor (202) arranged above the internal upper floor (103), and a plurality of upper shielding cavity shielding columns (201) are arranged between the top floor (202) and the strip line (1), the plurality of upper shielding cavity shielding columns (201) are arranged in a "U" shape, and the "U" shape opening faces the transition interface (4). ​ 6. The stripline-to-coaxial transition of claim 1, wherein: The lower shielding cavity (3) includes a bottom floor (302) arranged below the internal lower floor (104), and a plurality of lower shielding cavity shielding columns (301) are arranged between the bottom floor (302) and the strip line (1), the plurality of lower shielding cavity shielding columns (301) are arranged in a "U" shape, and the "U" shape opening faces the transition interface (4).

7. The stripline-to-coaxial transition of claim 1, wherein: The coaxial line (5) includes an outer conductor (502), the insulating gap (403) is located inside the outer conductor (502), an inner conductor (501) is arranged in the outer conductor (502), and the outer conductor (502) and the inner conductor (501) have an insulating medium therebetween.

8. The stripline-to-coaxial transition of claim 7, wherein: The insulating gap (403) is provided with a signal disc.

9. The stripline-to-coaxial transition of claim 1, wherein: The transition interface (4) is made of metal.

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