PCB mainboard signal conversion structure suitable for waveguide signal feed-in and waveguide transmission line

Abstract

The invention provides a PCB mainboard signal conversion structure suitable for waveguide signal feed-in and a waveguide transmission line, and the structure comprises a PCB mainboard which is provided with a grounding coplanar waveguide and a substrate integrated waveguide; one end of the grounding coplanar waveguide is used for being connected with a radio frequency chip, the other end of the grounding coplanar waveguide is connected with the substrate integrated waveguide, a coupling slot is formed in the substrate integrated waveguide area, and the coupling slot generates a signal fed in perpendicular to the tail end of the bottom surface of the waveguide H surface. Through a composite conversion structure of the grounding coplanar waveguide, the substrate integrated waveguide and the coupling slot, a radio frequency signal is converted into an electric field signal fed in perpendicular to the bottom surface of the waveguide H surface, and the problem of transmission mode conversion from a radio frequency chip signal to the waveguide is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of waveguide structures, and in particular to a PCB mainboard signal conversion structure and a waveguide transmission line suitable for waveguide signal feeding. Background Art

[0002] With the rapid development of wireless communication technology, microwaves and millimeter waves have gradually come into people's view and play an important role in the field of communications.

[0003] At present, in the application of vehicle-mounted millimeter-wave radar, waveguide antennas are gaining more and more attention due to their advantages such as low loss and high isolation. In the application of vehicle-mounted radar in the 76-81GHz frequency band, since the new RF chip technology with waveguide ports is not yet mature, using existing RF chips for waveguide connection has become an effective way to apply waveguide antennas in vehicle-mounted radar.

[0004] However, how to convert the RF signal into a signal suitable for feeding into the bottom surface of the waveguide H-surface becomes a key issue. Summary of the invention

[0005] In view of the defects in the prior art, the object of the present invention is to provide a PCB mainboard signal conversion structure and a waveguide transmission line suitable for waveguide signal feeding.

[0006] A PCB mainboard signal conversion structure suitable for waveguide signal feeding provided by the present invention comprises: a PCB mainboard, on which a grounded coplanar waveguide and a substrate integrated waveguide are respectively formed;

[0007] One end of the grounded coplanar waveguide is used to connect to the RF chip, and the other end of the grounded coplanar waveguide is connected to the substrate integrated waveguide. A coupling slot is arranged in the substrate integrated waveguide region, and the coupling slot generates a signal fed perpendicularly to the bottom surface of the waveguide H-plane.

[0008] Preferably, the top surface of the PCB mainboard is also formed with a signal transmission bottom surface, and the signal transmission bottom surface is used to form a waveguide cavity in combination with a single-layer waveguide, and the signal transmission bottom surface constitutes the H-plane bottom surface of the waveguide cavity.

[0009] Preferably, the slot antenna is made by removing metallization from the metal top surface of the substrate integrated waveguide, and the coupling slot is arranged at the end of the substrate integrated waveguide and is aligned with the center of the substrate integrated waveguide along the center line.

[0010] Preferably, the coupling slot has an H-shape, an oblique slot shape, a circle, an annular shape, a cross shape or a V-shape.

[0011] Preferably, the PCB main board comprises a PCB top surface, a dielectric layer and a PCB bottom surface which are stacked in sequence, and the PCB top surface and the PCB bottom surface are metallization layers;

[0012] A feed line is arranged on the top surface of the PCB, one end of the feed line is used to connect the RF chip, slots are arranged on both sides of the feed line on the top surface of the PCB, and grounding holes are arranged on the outside of the slots; the feed line, the slots and the grounding holes together constitute the grounded coplanar waveguide.

[0013] Preferably, the grounding hole is extended in a direction away from the radio frequency chip, and the lateral spacing between the grounding holes on both sides gradually increases, and the grounding hole is combined with the top surface of the PCB and the bottom surface of the PCB to form a substrate integrated waveguide;

[0014] The end of the substrate integrated waveguide is closed by one or more rows of grounding holes.

[0015] Preferably, a waveguide transition section is formed on the PCB main board between the grounded coplanar waveguide and the substrate integrated waveguide.

[0016] A waveguide transmission line provided according to the present invention comprises the PCB mainboard signal conversion structure suitable for waveguide signal feeding.

[0017] A waveguide antenna radar provided according to the present invention comprises the waveguide transmission line.

[0018] A car provided according to the present invention is characterized by comprising the waveguide antenna radar.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] 1. The present invention converts the radio frequency signal into an electric field signal fed perpendicular to the bottom surface of the waveguide H-plane through a composite conversion structure of a grounded coplanar waveguide, a substrate integrated waveguide and a coupling slot, thereby solving the problem of transmission mode conversion from the radio frequency chip signal to the waveguide.

[0021] 2. The present invention provides a waveguide transition section with gradually increasing lateral spacing, which is beneficial to the gradual transition of the signal transmission mode from the grounded coplanar waveguide to the substrate integrated waveguide, reduces adverse effects such as reflection and loss, and ensures transmission efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings:

[0023] Figure 1 is a schematic diagram of a traditional waveguide transmission line;

[0024] Figure 2Schematic diagram of a conventional waveguide transmission line with EH conversion;

[0025] Figure 3 A stereoscopic diagram of a millimeter wave radar waveguide antenna with a single-layer waveguide structure disclosed in the present invention;

[0026] Figure 4 A top view of a millimeter-wave radar waveguide antenna with a single-layer waveguide structure disclosed in the present invention;

[0027] Figure 5 It is a schematic diagram of matching the waveguide antenna disclosed in the present invention with the PCB mainboard;

[0028] Figure 6 A top view of the signal feeding structure disclosed in the present invention;

[0029] Figure 7 A cross-sectional view of the grounded coplanar waveguide disclosed in the present invention;

[0030] Figure 8 It is a cross-sectional view of the waveguide transition section disclosed in the present invention;

[0031] Fig. 9 A cross-sectional view of a substrate integrated waveguide disclosed in the present invention;

[0032] Fig.10 illustrative diagram of different shapes of coupling gaps disclosed in the present invention;

[0033] Fig.11 This is an example diagram of the shielding wall solution disclosed in the present invention;

[0034] Fig.12 This is a schematic diagram of S parameters in an embodiment of the present invention;

[0035] Fig.13 It is a three-dimensional exploded diagram of a practical case of the 4T4R single-layer waveguide structure antenna of the present invention.

[0036] Description of reference numerals:

[0037] DETAILED DESCRIPTION

[0038] The present invention is described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several changes and improvements can also be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0039] Typical waveguide functional surfaces are as follows: Figure 1As shown, the traditional feeding method of the PCB mainboard to the waveguide is usually to set a patch probe parallel to the end face of the waveguide, or to use a feeding probe protruding into the waveguide cavity to be set perpendicular to the bottom surface of the H-plane of the waveguide; because the PCB mainboard is usually parallel to the transmission direction of the waveguide, these feeding methods all require the setting of a feeding component protruding from the PCB surface on the PCB, which has the problems of complex structure and difficult processing and assembly.

[0040] Another more mainstream feeding method is Figure 2 As shown, this feeding method adds an EH conversion structure at the end of the lateral waveguide, so that the end face of the waveguide extending downward is aligned parallel to the patch probe set on the PCB mainboard to form a feeding structure. This feeding method has the problems of complex waveguide structure, multi-layer structure required during plastic molding, high assembly process requirements, and high cost.

[0041] The present invention provides a single-layer waveguide antenna, referring to Figure 3-Figure 11 As shown, it includes a PCB main board 1 and a waveguide antenna 2.

[0042] The PCB main board 1 includes a PCB top surface 11, a dielectric layer 12 and a PCB bottom surface 13, wherein the PCB top surface 11 and the PCB bottom surface 13 are metallized layers, and the dielectric layer 12 is made of high-frequency PCB material suitable for the 76-81 GHz frequency band, with a thickness of 5-10 mil.

[0043] A feed line 111 is arranged on the top surface 11 of the PCB, one end of which is connected to the signal pin of the RF chip to receive or feed back electromagnetic signals; slots 115 are arranged on both sides of the feed line 111 of the PCB top surface 11, and ground holes 116 of suitable size and spacing are arranged outside the slots 115, and the ground holes 116 are respectively well electrically connected to the top surface 11 of the PCB and the bottom surface 13 of the PCB. The grounded coplanar waveguide is mainly formed by the feed line 111, the slots 115 and the ground holes 116.

[0044] The grounding holes 116 extend in a direction away from the RF chip, with the lateral spacing gradually increasing, and are mainly combined with the PCB top surface 11 and the PCB bottom surface 13 to form a substrate integrated waveguide 113. The ends of the substrate integrated waveguide 113 are closed with one or more rows of grounding holes 116, forming a substrate integrated waveguide 113 with closed ends. The grounding holes 116 can be single or multiple rows to meet the performance requirements of good grounding and signal shielding.

[0045] Between the grounded coplanar waveguide and the substrate integrated waveguide 113 , the width of the feed line 111 gradually increases, the width of the slots 115 on both sides remains unchanged but the lateral spacing gradually increases, forming a waveguide transition section 112 between the grounded coplanar waveguide and the substrate integrated waveguide 113 .

[0046] There is a difference in the lateral width of the grounded coplanar waveguide and the substrate integrated waveguide 113, that is, the grounded coplanar waveguide is smaller and the substrate integrated waveguide 113 is larger; by setting a waveguide transition section 112 with a gradually increasing spacing, the grounded coplanar waveguide and the substrate integrated waveguide 113 can be effectively connected; the gradually increasing spacing is conducive to the gradual transition of the signal transmission mode from the grounded coplanar waveguide to the substrate integrated waveguide 113, reducing adverse effects such as reflection and loss, and ensuring transmission efficiency.

[0047] On the top surface 11 of the PCB, in the area of ​​the substrate integrated waveguide 113, a coupling slot 114 without metallization or with metallization removed is provided; the coupling slot 114 is provided at the end of the substrate integrated waveguide 113 and is aligned with the substrate integrated waveguide 113 along the center line; the electric field perpendicular to the H-plane of the waveguide is excited by the coupling slot 114, so as to couple the energy of the baseband integrated waveguide into the waveguide. The shape of the coupling slot 114 can be in the form of an H-shape, an oblique slot shape, a circle, an annular shape, a cross shape, a V-shape, etc., and there is no restriction here, as long as it can excite the mode conversion from the substrate integrated waveguide 113 to the waveguide. By adjusting the local size of the shape, the reflection and impedance matching of the conversion can be improved, thereby improving the transmission efficiency.

[0048] Reference Fig.10 As shown, the coupling gap 114 can be set to a variety of different shapes. Fig.10 Among the coupling gaps 114 (the shaded part in the figure), a is H-shaped, b is oblique gap-shaped, c is cross-shaped, d is V-shaped, e is circular, and f is annular.

[0049] The waveguide antenna 2 includes: a waveguide top layer 21 , a shielding wall 22 , a magnetic conductor 24 and a slot antenna 23 .

[0050] The waveguide top layer 21 is the main component of the waveguide antenna 2, and a shielding wall 22 and a magnetic conductor 24 are arranged below it; the shielding wall 22 and the magnetic conductor 24 are combined with the waveguide top layer 21 to form two E-surface side surfaces, an H-surface top surface and two terminal end surfaces of the waveguide cavity. The top surface of the PCB main board 1 also forms a signal transmission bottom surface 117, which covers the waveguide cavity and constitutes the H-surface bottom surface of the waveguide cavity, and is combined to form a complete waveguide cavity.

[0051] The end feeding port 26 of the waveguide cavity located at the bottom of the H-plane covers the coupling gap 114, as shown in FIG. Figure 5As shown, a feeding port 26 for the signal from the coupling slot 114 to the waveguide antenna is formed on the bottom surface of the H surface of the waveguide cavity. The coupling slot 114 and the feeding port 26 are aligned along the center of the signal transmission direction. The coupling slot 114 and the feeding port 26 at the end of the bottom surface of the H surface of the waveguide are kept at an appropriate distance to ensure excellent coupling efficiency. The extension direction of the waveguide cavity is parallel to the PCB main board 1, wherein the top surface and the bottom surface of the H surface of the waveguide cavity are both parallel to the PCB main board 1.

[0052] In the design of the waveguide antenna 2, the fewer the waveguide layers, the simpler the manufacturing, the smaller the volume, and the lower the cost. Therefore, the optimal structure of the waveguide antenna 2 is a single layer. The single-layer waveguide antenna 2 needs to use the metal top surface of the PCB mainboard 1 as the H-surface bottom surface of the waveguide. The single-layer structure is conducive to the plastic molding and post-surface metallization process of the waveguide antenna, and does not require additional connection processes such as welding or gluing. It is more conducive to the processing and assembly of the radar waveguide antenna, reduces the dimensional accuracy requirements, and saves manufacturing costs.

[0053] The main characteristic requirement of waveguide feeding is that the electric field direction of the fed signal must be perpendicular to the waveguide H-plane (i.e., the long side plane). In the design of a single-layer waveguide body, the top surface of the PCB mainboard 1 is parallel to and close to the bottom H-plane of the waveguide cavity. The electric field direction of the electromagnetic signal excited by the patch probe provided by the traditional microstrip design must be parallel to the waveguide H-plane, and thus cannot excite the waveguide transmission mode.

[0054] The present invention uses a coupling slot 114 on a substrate integrated waveguide 113 to perform signal conversion, thereby solving the signal transmission problem from a PCB mainboard 1 to a single-layer waveguide antenna 2. Slot coupling is a waveguide coupler in principle. The basic structure of a waveguide coupler includes an input waveguide, an output waveguide, and a coupling component. When a microwave signal enters the coupling component from the input waveguide, the signal can be coupled to the output waveguide, thereby realizing signal transmission and distribution.

[0055] At the other end of the waveguide cavity, multiple slot structures are provided to penetrate the waveguide top layer 21 to form a waveguide slot antenna 23 for transmitting and receiving signals of the waveguide antenna 2. The number of slots in the slot antenna 23 is determined according to different antenna radiation performances. In vehicle-mounted radar applications, 4 to 12 slots are generally provided in consideration of the size of the waveguide structure itself.

[0056] Reference Fig.11As shown, the internal dimensions of the waveguide cavity formed by the shielding wall 22 and the magnetic conductor 24 are set to a ratio of 2:1 or a similar ratio of the H-surface width to the E-surface height, and meet the transmission requirements of the 76-81GHz frequency band; the magnetic conductor 24 can be one circle, two circles or more circles, and the shielding wall 22 is set on the outside of the magnetic conductor 24; the magnetic conductor 24 is a periodically arranged cylinder, rectangle, trapezoid and other geometric shapes, which can be selected according to different materials and processes, isolation performance and other technical requirements; according to actual needs, a ridge 25 can be added to form a ridge waveguide form. A ridge 25 is set below the top layer of the waveguide and located at the center line of the waveguide cavity to form a ridge waveguide transmission line. The positive projection of the ridge 25 on the PCB mainboard 1 is staggered with the coupling gap 114, and the waveguide cavity is a cavity at the feeding port 26.

[0057] The material of the waveguide antenna 2 is metal material, or plastic material with metallized surface.

[0058] The connection between the waveguide antenna 2 and the PCB main board 11 is generally a metal fastening connection or a plastic fastening connection. Among them, the shielding wall 22 and the magnetic conductor 24 can be closely connected or set with a gap with the PCB main board 1; the feed port 26 at the end of the waveguide cavity located on the bottom surface of the H surface is kept at an appropriate distance from the coupling gap 114 to stimulate signal coupling.

[0059] Reference Fig.12 As shown, the waveguide antenna 2 structure disclosed in the present invention achieves efficient conversion with an operating frequency of 76-81 GHz, a -10 dB relative bandwidth of 12.16%, and a loss of -0.6 dB, and is suitable for vehicle-mounted radar applications. Fig.12 It can be seen from the figure that the present invention realizes the feeding from the substrate integrated waveguide to the end feeding port 26 of the bottom surface of the waveguide H-plane, and the transmission efficiency is high.

[0060] Reference Fig.13 As shown, in a specific implementation manner provided by the present invention, a practical case of a 4T4R single-layer waveguide structure transmission line is introduced, which includes a radio frequency chip and 8 single-layer waveguide antennas 2 connected to the radio frequency chip.

[0061] The present invention provides a waveguide antenna radar, which adopts the waveguide transmission line of the present invention. The present invention also provides a car, on which the waveguide antenna radar is installed.

[0062] In the description of the present application, it should be understood that the terms "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0063] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various changes or modifications within the scope of the claims, which does not affect the essence of the present invention. In the absence of conflict, the embodiments of the present application and the features in the embodiments can be combined with each other arbitrarily.

Claims

1. A PCB mainboard signal conversion structure suitable for waveguide signal feeding, characterized in that: include: A PCB mainboard (1), wherein a grounded coplanar waveguide and a substrate integrated waveguide (113) are respectively formed on the PCB mainboard (1); One end of the grounded coplanar waveguide is used to connect to a radio frequency chip, and the other end of the grounded coplanar waveguide is connected to the substrate integrated waveguide (113). A coupling slot (114) is provided in the substrate integrated waveguide (113) region, and the coupling slot (114) generates a signal fed vertically to the bottom surface of the waveguide H-plane.

2. The PCB mainboard signal conversion structure suitable for waveguide signal feeding according to claim 1 is characterized in that: The top surface of the PCB mainboard (1) is also formed with a signal transmission bottom surface (117), the signal transmission bottom surface (117) is used to form a waveguide cavity in combination with a single-layer waveguide, and the signal transmission bottom surface (117) constitutes the H-plane bottom surface of the waveguide cavity.

3. The PCB mainboard signal conversion structure suitable for waveguide signal feeding according to claim 1 is characterized in that: The slot antenna (23) is manufactured by removing metallization from the metal top surface of a substrate integrated waveguide (113); the coupling slot (114) is arranged at the end of the substrate integrated waveguide (113) and is aligned with the center of the substrate integrated waveguide (113) along a center line.

4. The PCB mainboard signal conversion structure suitable for waveguide signal feeding according to claim 1 is characterized in that: The coupling gap (114) is in an H-shape, an oblique slit shape, a circle, an annular shape, a cross shape or a V-shape.

5. The PCB mainboard signal conversion structure suitable for waveguide signal feeding according to claim 1 is characterized in that: The PCB main board (1) comprises a PCB top surface (11), a dielectric layer (12) and a PCB bottom surface (13) which are stacked in sequence, and the PCB top surface (11) and the PCB bottom surface (13) are metallized layers; A feed line (111) is arranged on the top surface (11) of the PCB, one end of the feed line (111) is used to connect to a radio frequency chip, slots (115) are arranged on both sides of the feed line (111) on the top surface (11) of the PCB, and grounding holes (116) are arranged outside the slots (115); the feed line (111), the slots (115) and the grounding holes (116) together constitute the grounded coplanar waveguide.

6. The PCB mainboard signal conversion structure suitable for waveguide signal feeding according to claim 5 is characterized in that: The grounding holes (116) are extended in a direction away from the radio frequency chip, and the lateral spacing between the grounding holes (116) on both sides gradually increases; the grounding holes (116) are combined with the PCB top surface (11) and the PCB bottom surface (13) to form a substrate integrated waveguide (113); The end of the substrate integrated waveguide (113) is closed by one or more rows of grounding holes.

7. The PCB mainboard signal conversion structure suitable for waveguide signal feeding according to claim 7, characterized in that: A waveguide transition section (112) is formed on the PCB mainboard (1) between the grounded coplanar waveguide and the substrate integrated waveguide (113).

8. A waveguide transmission line, characterized in that: A PCB mainboard signal conversion structure suitable for waveguide signal feeding comprising any one of claims 1 to 7.

9. A waveguide antenna radar, characterized in that: Comprising the waveguide transmission line as claimed in claim 8.

10. An automobile, characterized in that: Includes the waveguide antenna radar as described in claim 9.

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