Coaxial-coplanar waveguide broadband matching structure for millimeter wave frequency band and installation method

Abstract

The invention provides a coaxial-coplanar waveguide broadband matching structure for a millimeter wave frequency band and an installation method. The coaxial-coplanar waveguide broadband matching structure for the millimeter wave frequency band comprises a coaxial plane center line structure, a coaxial plane coplanar gradient line structure and a coaxial plane coplanar waveguide structure which are sequentially arranged in the millimeter wave propagation direction, and the coaxial plane center line structure is fixedly connected with the coaxial plane coplanar gradient line structure. The coaxial plane coplanar tapered line structure is fixedly connected with the coaxial plane coplanar waveguide structure; the coaxial plane center line structure is used for forming a sheet-shaped axisymmetric field force line; the coaxial plane coplanar gradual change line structure is used for realizing gradual change of a field force line; the coaxial plane coplanar waveguide structure is used for forming a specific field force line, the specific field force line enables an electric field to be emitted to the plane grounding layers on the two sides, and the magnetic field shrinks. According to the coaxial-coplanar waveguide broadband matching structure for the millimeter wave frequency band, signal reflection caused by interconnection of the coaxial structure and the coplanar waveguide can be reduced, and impedance mutation is avoided.

Description

Technical Field

[0001] This invention relates to the field of millimeter-wave transmission, and in particular to a coaxial-coplanar waveguide broadband matching structure and installation method for millimeter-wave frequency bands. Background Technology

[0002] In modern microwave and millimeter-wave communications, radar systems, and high-speed data conversion circuits, coaxial connectors and coplanar waveguides are two crucial signal transmission media, widely used due to their unique advantages. However, achieving efficient and low-loss interconnection between these two structures has been a long-standing challenge in high-frequency circuit design. With the advancement of wireless communication technology towards millimeter-wave waveguides and the increasing pursuit of miniaturization, integration, and high performance in electronic devices, the importance of coaxial-coplanar waveguide matching structures—which can achieve good impedance matching, low insertion loss, and structural stability over a wide bandwidth—is becoming increasingly prominent.

[0003] Traditional low-frequency interconnection methods are relatively straightforward, typically involving directly soldering the center conductor of the coaxial cable (e.g., a probe) to the signal line of the coplanar waveguide, while simultaneously connecting the outer conductor of the coaxial cable to the ground plane of the coplanar waveguide. However, as operating frequencies enter the microwave and even millimeter-wave bands, this traditional interconnection method exposes several problems. First, mode mismatch is extremely prominent. The coaxial cable transmits axisymmetric TEM modes, while the coplanar waveguide transmits quasi-TEM modes. The electric field distributions of these two modes are fundamentally different, and direct connection will excite higher-order modes and discontinuities in capacitance, leading to severe signal reflection. Second, structural discontinuities introduce impedance abrupt changes. Unavoidable assembly gaps at the connection points introduce significant parasitic inductance and capacitance, disrupting the characteristic impedance continuity of the transmission line, causing impedance mismatch, and consequently increasing insertion loss and limiting operating bandwidth. These problems are particularly critical in the Ku-band and higher frequency bands, where traditional structures often struggle to achieve ultra-wideband matching.

[0004] Therefore, there is an urgent need for a broadband matching structure for coaxial-coplanar waveguides in the millimeter-wave band that can effectively reduce signal reflections at the interconnection between the coaxial structure and the coplanar waveguide, and avoid impedance abrupt changes. Summary of the Invention

[0005] This invention provides a coaxial-coplanar waveguide broadband matching structure for the millimeter-wave band, comprising a coaxial plane centerline structure, a coaxial plane coplanar tapered line structure, and a coaxial plane coplanar waveguide structure arranged sequentially along the millimeter-wave propagation direction. The coaxial plane centerline structure and the coaxial plane coplanar tapered line structure are fixedly connected, and the coaxial plane coplanar tapered line structure and the coaxial plane coplanar waveguide structure are fixedly connected.

[0006] in,

[0007] Coaxial plane centerline structures are used to form sheet-like axisymmetric field force lines;

[0008] Coaxial planar coplanar gradient line structure is used to realize the gradual change of field force lines, that is, the field force lines corresponding to the coaxial structure gradually change to the field force lines corresponding to the coplanar waveguide transmission line.

[0009] Coaxial planar waveguide structures are used to form specific field lines, which cause the electric field to be emitted towards the two planar ground layers and the magnetic field to contract.

[0010] Furthermore, the central conductor of the coaxial plane centerline structure has a first thin film sheet structure.

[0011] Furthermore, the central conductor of the coaxial planar coplanar tapered line structure has a size-gradient structure along the millimeter wave propagation direction.

[0012] Furthermore, the size gradient structure is a tapered size gradient structure.

[0013] Furthermore, the central conductor of the coaxial planar waveguide structure has a second thin-film sheet structure.

[0014] Furthermore, the width of the second thin film sheet structure is smaller than the width of the first thin film sheet structure.

[0015] Furthermore, the substrate for the coaxial-coplanar waveguide broadband matching structure used in the millimeter-wave band is polytetrafluoroethylene.

[0016] Furthermore, the substrate surface is plated with an 18μm thick copper layer and a 25nm thick gold layer.

[0017] Furthermore, the substrate thickness is 0.05 mm.

[0018] This invention provides a coaxial-coplanar waveguide broadband matching structure for the millimeter-wave band. It involves sequentially arranging a coaxial planar centerline structure, a coaxial planar coplanar tapered line structure, and a coaxial planar coplanar waveguide structure along the millimeter-wave propagation direction. The center conductor of the coaxial planar coplanar tapered line structure has a tapered size along the millimeter-wave propagation direction. This solves the problem of inconsistencies between the coaxial center conductor and the coplanar waveguide dimensions, preventing direct connection and effectively reducing signal reflection during the interconnection of the coaxial structure and the coplanar waveguide, thus avoiding impedance abrupt changes. Furthermore, it addresses the precision issues of hard-connection processes for the two structures, extending the frequency range of the two transmission lines to 67 GHz with a full-band VSWR of less than 1.45. It is easy to manufacture and assemble, and exhibits excellent stability and scalability.

[0019] The present invention also provides an installation method for a coaxial-coplanar waveguide broadband matching structure for the millimeter-wave band, comprising the following steps:

[0020] S1. Fix the coaxial-coplanar waveguide broadband matching structure for the millimeter-wave band onto the coaxial-coplanar adapter plate;

[0021] S2. Align and connect the coaxial plane centerline structure (1) of the coaxial-coplanar waveguide broadband matching structure used in the millimeter wave band with the coaxial structure.

[0022] S3. The coaxial planar coplanar waveguide structure (3) used for the millimeter-wave band broadband matching structure is welded to the coplanar waveguide structure.

[0023] Other features and advantages of the invention will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures particularly pointed out in the written description, claims, and accompanying drawings. Attached Figure Description

[0024] The accompanying drawings, which are included to provide a further understanding of the invention and constitute a part of this invention, illustrate exemplary embodiments of the invention and are used to explain the invention, but do not constitute an undue limitation of the invention. In the drawings:

[0025] Figure 1 This is a schematic diagram of a coaxial-coplanar waveguide broadband matching structure for the millimeter-wave band according to an embodiment of the present invention;

[0026] Figure 2 This is a schematic diagram of the field force lines of the coaxial plane centerline structure in a broadband matching structure for millimeter-wave band according to an embodiment of the present invention.

[0027] Figure 3 This is a schematic diagram of the field force lines of a coaxial planar coplanar tapered line structure in a broadband matching structure for millimeter-wave band according to an embodiment of the present invention.

[0028] Figure 4 This is a schematic diagram of the field force lines of a coaxial planar coplanar waveguide structure in a broadband matching structure for millimeter-wave band according to an embodiment of the present invention.

[0029] Figure 5 This is a schematic diagram of the installation of a coaxial-coplanar waveguide broadband matching structure for the millimeter-wave band according to an embodiment of the present invention.

[0030] Reference numerals: 1: Coaxial plane centerline structure, 2: Coaxial plane coplanar gradient line structure, 3: Coaxial plane coplanar waveguide structure. Detailed Implementation

[0031] To address the technical challenges of signal reflection and impedance abrupt changes caused by structural discontinuities in the interconnection of coaxial structures and coplanar waveguides, a broadband matching structure for coaxial-coplanar waveguides in the millimeter-wave band is provided.

[0032] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention. Furthermore, the embodiments and features in the embodiments of the present invention can be combined with each other without conflict.

[0033] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of the embodiments of the present invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments described herein can be implemented in a sequence other than that illustrated or described herein.

[0034] Figure 1 This diagram illustrates a broadband matching structure for a coaxial-coplanar waveguide in the millimeter-wave band according to an embodiment of the present invention. Figure 2 This diagram illustrates the field force lines of the coaxial plane centerline structure in a coaxial-coplanar waveguide broadband matching structure for the millimeter-wave band, according to an embodiment of the present invention. Figure 3 This is a schematic diagram of the field force lines of a coaxial planar coplanar tapered line structure in a broadband matching structure for millimeter-wave band according to an embodiment of the present invention. Figure 4 This is a schematic diagram of the field force lines of a coaxial planar coplanar waveguide structure in a broadband matching structure for millimeter-wave band according to an embodiment of the present invention.

[0035] See Figures 1-4 A coaxial-coplanar waveguide broadband matching structure for millimeter-wave band includes: a coaxial plane centerline structure 1, a coaxial plane coplanar gradient line structure 2, and a coaxial plane coplanar waveguide structure 3 arranged sequentially along the millimeter-wave propagation direction. The coaxial plane centerline structure 1 and the coaxial plane coplanar gradient line structure 2 are fixedly connected, and the coaxial plane coplanar gradient line structure 2 and the coaxial plane coplanar waveguide structure 3 are fixedly connected.

[0036] Among them, the coaxial plane centerline structure 1 is used to form a sheet-like axisymmetric field force line, which is approximately regarded as a continuously gradually changing coaxial transmission line used to transmit the axisymmetric TEM mode. It can weaken the impedance abrupt change and reduce the signal reflection caused by the step change in coaxial size.

[0037] Specifically, the central conductor of the coaxial plane centerline structure 1 has a first thin film sheet structure.

[0038] Among them, the coaxial planar coplanar gradient line structure 2 is used to realize the gradient of the field force lines, that is, the field force lines corresponding to the coaxial structure gradually change to the field force lines corresponding to the coplanar waveguide transmission lines, and its structure is transformed from a sheet-like axisymmetric structure to a coplanar waveguide structure under the coaxial cavity.

[0039] Specifically, the central conductor of the coaxial planar coplanar tapered line structure 2 has a size-gradient structure along the millimeter wave propagation direction, which can further weaken impedance abrupt changes and reduce signal reflection caused by size step changes.

[0040] Furthermore, the size gradient structure is a tapered size gradient structure, achieving a smooth transition.

[0041] Among them, the coaxial planar coplanar waveguide structure 3 is used to form specific field force lines. The specific field force lines cause the electric field emission to move towards the two planar ground layers and the magnetic field to contract, resulting in a stronger energy density. The axisymmetric TEM mode gradually converts into a quasi-TEM mode, completing the mode conversion.

[0042] Specifically, the central conductor of the coaxial planar waveguide structure 3 has a second thin film sheet structure.

[0043] Furthermore, the width of the second thin film sheet structure is smaller than the width of the first thin film sheet structure.

[0044] The substrate for the coaxial-coplanar waveguide broadband matching structure used in the millimeter-wave band is polytetrafluoroethylene (PTFE), with a substrate thickness of 0.05 mm. The substrate surface is plated with an 18 μm thick copper layer and a 25 nm thick gold layer.

[0045] In addition, to achieve broadband matching as much as possible, electromagnetic field simulation can be performed on the structural dimensions to achieve transition matching over a wider frequency band. Based on the electromagnetic field simulation model, the dielectric thickness, gold layer thickness, gap spacing, and transition structure length can be adjusted.

[0046] In summary, this invention provides a coaxial-coplanar waveguide broadband matching structure for the millimeter-wave band. By sequentially arranging a coaxial planar centerline structure 1, a coaxial planar coplanar tapered line structure 2, and a coaxial planar coplanar waveguide structure 3 along the millimeter-wave propagation direction, and with the center conductor of the coaxial planar coplanar tapered line structure 2 having a size-gradient structure along the millimeter-wave propagation direction, this invention solves the problem of inconsistencies between the coaxial center conductor size and the coplanar waveguide size, preventing direct connection. This effectively reduces signal reflection during the interconnection of the coaxial structure and the coplanar waveguide, avoiding impedance abrupt changes. Furthermore, it addresses the precision issues of hard-connection processes for the two structures, extending the frequency range of the two transmission lines to 67 GHz with a full-band VSWR of less than 1.45. It is also easy to process and assemble, exhibiting excellent stability and scalability.

[0047] Figure 5 The illustration shows an installation diagram of a coaxial-coplanar waveguide broadband matching structure for the millimeter-wave band according to an embodiment of the present invention. The present invention also provides an installation method for a coaxial-coplanar waveguide broadband matching structure for the millimeter-wave band, comprising the following steps:

[0048] S1. Fix the coaxial-coplanar waveguide broadband matching structure for the millimeter-wave band onto the coaxial-coplanar adapter plate.

[0049] S2. Align and connect the coaxial plane centerline structure 1, which is used for the broadband matching structure of the coaxial-coplanar waveguide in the millimeter-wave band, with the coaxial structure.

[0050] The coaxial structure adopts a 1.85mm coaxial form with a central conductor diameter of 0.8mm. The probe with a length of 0.1mm is cut in half in the direction of millimeter wave propagation to facilitate the installation of the coaxial-coplanar waveguide broadband matching structure for the millimeter wave band.

[0051] Specifically, the metal layer of the coaxial-coplanar adapter board faces downwards, and solder paste is applied evenly and smoothly, with the solder layer thickness controlled within 0.05mm. A certain pressure is applied during soldering. Solder paste is evenly applied to both sides and the surrounding plane of the coaxial-coplanar adapter board, with the solder layer thickness controlled within 0.05mm. A certain pressure is applied during soldering to ensure electrical connection.

[0052] S3. The coaxial planar coplanar waveguide structure 3, which is used for the millimeter-wave band broadband matching structure, is welded to the coplanar waveguide structure.

[0053] Specifically, the cross-stamping width is 0.07mm, the solder paste is applied, and the solder paste thickness is controlled within 0.05mm; the centerline width of the coplanar waveguide structure is 0.074mm, the gap width is 0.043mm, the centerline width of the coaxial-coplanar adapter board is 0.1mm, and the gap width is 0.05mm.

[0054] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of the invention.

[0055] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A coaxial-coplanar waveguide broadband matching structure for millimeter-wave bands, characterized in that, It includes a coaxial plane centerline structure (1), a coaxial plane coplanar gradient line structure (2), and a coaxial plane coplanar waveguide structure (3) arranged sequentially along the millimeter wave propagation direction. The coaxial plane centerline structure (1) is fixedly connected to the coaxial plane coplanar gradient line structure (2), and the coaxial plane coplanar gradient line structure (2) and the coaxial plane coplanar waveguide structure (3) are fixedly connected. in, The coaxial plane centerline structure (1) is used to form sheet-like axisymmetric field force lines; The coaxial planar coplanar gradient line structure (2) is used to realize the gradient of the field force lines, that is, the field force lines corresponding to the coaxial structure gradually change to the field force lines corresponding to the coplanar waveguide transmission lines. The coaxial planar waveguide structure (3) is used to form specific field lines, which cause the electric field to be emitted towards the two planar ground layers and the magnetic field to contract.

2. The coaxial-coplanar waveguide broadband matching structure for millimeter-wave band according to claim 1, characterized in that, The central conductor of the coaxial plane centerline structure (1) has a first thin film sheet structure.

3. The coaxial-coplanar waveguide broadband matching structure for millimeter-wave band according to claim 1, characterized in that, The central conductor of the coaxial planar coplanar gradient line structure (2) has a size gradient structure along the millimeter wave propagation direction.

4. The coaxial-coplanar waveguide broadband matching structure for millimeter-wave band according to claim 3, characterized in that, The size gradient structure is a tapered size gradient structure.

5. A coaxial-coplanar waveguide broadband matching structure for millimeter-wave bands according to claim 2, characterized in that, The central conductor of the coaxial planar waveguide structure (3) has a second thin film sheet structure.

6. The coaxial-coplanar waveguide broadband matching structure for millimeter-wave band according to claim 5, characterized in that, The width of the second thin film sheet structure is smaller than the width of the first thin film sheet structure.

7. The coaxial-coplanar waveguide broadband matching structure for millimeter-wave band according to claim 1, characterized in that, The substrate for the coaxial-coplanar waveguide broadband matching structure used in the millimeter-wave band is polytetrafluoroethylene.

8. A coaxial-coplanar waveguide broadband matching structure for millimeter-wave bands according to claim 7, characterized in that, The substrate surface is plated with an 18μm thick copper layer and a 25nm thick gold layer.

9. The coaxial-coplanar waveguide broadband matching structure for millimeter-wave band according to claim 7, characterized in that, The thickness of the substrate is 0.05 mm.

10. The installation method of the coaxial-coplanar waveguide broadband matching structure for the millimeter-wave band according to any one of claims 1 to 9, characterized in that, Includes the following steps: S1. Fix the coaxial-coplanar waveguide broadband matching structure for the millimeter-wave band onto the coaxial-coplanar adapter plate; S2. Align and connect the coaxial plane centerline structure (1) of the coaxial-coplanar waveguide broadband matching structure used in the millimeter wave band with the coaxial structure. S3. The coaxial planar coplanar waveguide structure (3) used for the millimeter-wave band broadband matching structure is welded to the coplanar waveguide structure.

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