A substrate integrated coaxial line based cavity-backed slot antenna and manufacturing method

Abstract

The present invention discloses a substrate integrated coaxial line-based back cavity slot antenna and a manufacturing method thereof, which includes a substrate integrated coaxial line and a feeding structure with coupling slots, a substrate integrated waveguide circular resonator composed of four slot holes, and an H-shaped radiation slot. The present invention adopts an upper and lower stacked structure. The substrate integrated coaxial line is at the bottommost layer, the coupling slots are directly above the substrate integrated coaxial line, and the geometric centers of the coupling slots coincide with the geometric center of the upper substrate integrated waveguide circular resonator along the z-axis. The H-shaped radiation slot is etched on the top layer metal of the circular resonator. By using the coupling slot feeding, the electromagnetic energy in the substrate integrated coaxial line can be coupled into the circular resonator to excite the high-order modes in the resonator. The present invention adopts the substrate integrated coaxial line slot coupling technology to effectively excite the high-order modes in the circular resonator, expand the bandwidth, and achieve the low profile and integration of the antenna.

Description

Technical Field

[0001] The present invention relates to the field of wireless communication technology, and in particular to a cavity-backed slot antenna based on a substrate-integrated coaxial line and a processing method thereof. Background Art

[0002] In recent years, with the rapid development of wireless communication technology, the requirements for antennas in wireless communication systems have become increasingly higher. In a complex electromagnetic environment, both civil and military communication systems require not only high-quality transmission of multimedia information, but also the practical application of high-speed wireless communication under mobile conditions, which puts forward specific requirements for wireless communication equipment such as broadband, miniaturization, easy integration, and high gain. Although millimeter wave communication has many advantages, the key reason why it has not been used in mobile communications is that millimeter waves are easily absorbed by oxygen molecules when propagating in the atmosphere, resulting in extremely high path loss of millimeter waves, especially in severe weather conditions such as rain. Under the complex electromagnetic environment of 5G, single antenna form has become increasingly difficult to meet actual needs, and array antennas have become the most common antenna form in current 5G antenna design. The design of the array not only needs to consider the design of the unit, but also the design of the underlying feed network is also crucial.

[0003] In the millimeter wave band, the radiation efficiency of the antenna is an important indicator. Traditional rectangular or circular cavity-backed slot antennas etch slots on the resonant cavity, which can effectively cut the surface current of the metal, thereby enabling electromagnetic waves to radiate. This type of antenna has the advantages of low mutual coupling, high front-to-back ratio, high radiation efficiency and high gain, but it also has problems such as large size and high manufacturing cost, which seriously limits the practical application of this type of antenna.

[0004] How to solve the practical problems existing in traditional resonant cavities and achieve low profile and low cost of antennas while retaining the advantages of the original resonant cavity structure is the current problem. Summary of the invention

[0005] In order to solve the problems arising from the prior art, the present invention provides a cavity-backed slot antenna based on a substrate-integrated coaxial line with low profile, high integration and high gain, and a processing method thereof.

[0006] The present invention adopts the following technical scheme: a cavity-backed slot antenna based on a substrate integrated coaxial line, comprising a top metal conductor, a resonant cavity dielectric layer, an intermediate metal conductor, an upper dielectric layer, a metal inner conductor layer, an intermediate adhesive layer, a lower dielectric layer and a bottom metal conductor arranged from top to bottom;

[0007] A through circular resonant cavity is provided on the top metal conductor and the resonant cavity dielectric layer, and the circular resonant cavity includes slots evenly distributed in a ring shape.

[0008] An H-shaped radiation slot is etched on the top-layer metal conductor, and the H-shaped radiation slot is located in a circular resonant cavity;

[0009] A coupling slot is etched at the center of the middle-layer metal conductor, and the coupling slot is located in the circular resonant cavity,

[0010] The metal inner conductor layer is located at the center of the upper surface of the middle bonding layer,

[0011] Metallized vias are provided on the upper dielectric layer, the middle bonding layer, the lower dielectric layer and the bottom-layer metal conductor,

[0012] In the same plane, a plurality of metallized vias are in a rectangular shape with one end open,

[0013] In the z-axis direction, the coupling slot and the metal inner conductor layer are arranged crosswise and are respectively located in the metallized vias arranged in a rectangular shape.

[0014] The geometric center of the H-shaped radiation slot coincides with the geometric center of the circular resonant cavity along the z-axis.

[0015] The coupling slot is a horizontal slot,

[0016] The geometric center of the coupling slot coincides with the geometric center of the circular resonant cavity in the z-axis direction.

[0017] In the z-axis direction, the coupling slot and the metal inner conductor layer are arranged perpendicularly.

[0018] The rectangular metallized vias are symmetrically arranged on both sides and in front of the metal inner conductor layer, and the metal inner conductor layer is spaced from the metallized vias located in front.

[0019] The diameter of the metallized via is 0.4 mm, and the hole pitch between adjacent metallized vias in each row is 0.6 mm.

[0020] The top-layer metal conductor, the middle-layer metal conductor, the bottom-layer metal conductor and the metal inner conductor layer are all made of copper.

[0021] The resonant cavity dielectric layer is a Rogers 5880 printed circuit board with a thickness of 0.787 mm, the upper dielectric layer and the lower dielectric layer are both Rogers 5880 printed circuit boards with a thickness of 0.254 mm, and the middle bonding layer is a Rogers 4450F printed circuit board with a thickness of 0.1 mm.

[0022] A processing method for a substrate integrated coaxial back cavity slot antenna, comprising an upper component and a lower component which are connected up and down;

[0023] Among them,

[0024] The processing of the upper component includes:

[0025] S11. Copper is plated on the upper surface of the resonant cavity dielectric layer to form a top metal conductor, and copper is plated on the lower surface of the resonant cavity dielectric layer to form an intermediate metal conductor;

[0026] S12. An H-shaped radiation slot is etched on the surface of the top metal conductor, and a through-round resonant cavity is provided on the top metal conductor and the resonant cavity dielectric layer;

[0027] S13. A coupling slot is etched at the center of the intermediate metal conductor;

[0028] The processing of the lower component includes:

[0029] S21. Copper is plated on the lower surface of the upper dielectric layer to form a metal inner conductor layer, and copper is plated on the lower surface of the lower dielectric layer to form a bottom metal conductor;

[0030] S22. The upper dielectric layer, the lower dielectric layer and the intermediate adhesive layer are laminated, and finally holes are drilled at the corresponding positions of the metallized vias, and electrical connection is realized by copper plating between the holes.

[0031] The present invention has the following beneficial effects:

[0032] 1. The present invention is designed based on substrate integrated coaxial line, and the cross-section is reduced; by etching a coupling slot directly above the metal inner conductor layer of the substrate integrated coaxial line, the electromagnetic energy in the substrate integrated coaxial line can be coupled to the upper-round resonant cavity, and the high-order mode in the resonant cavity can be effectively excited.

[0033] 2. The coupling slot feeding of the substrate integrated coaxial line and the stacked structure of the substrate integrated waveguide round resonant cavity are beneficial to realizing the integrated design of the antenna and the microwave millimeter-wave circuit.

[0034] 3. By etching an H-shaped radiation slot on the top metal of the round resonant cavity, after the high-order mode is excited at the coupling slot, according to the electric field structure of the excited mode, by etching a slot at a suitable position, the efficient radiation of electromagnetic waves can be realized, and the design of a high-gain antenna can be realized. Description of the Drawings

[0035] Figure 1 is the structural diagram of the present invention;

[0036] Figure 2 is the schematic diagram of the feeding structure;

[0037] Figure 3 is the schematic diagram of the top metal conductor;

[0038] Figure 4 is the schematic diagram of the reflection coefficient and gain of the present invention;

[0039] Figure 5Schematic diagram of the main polarization and cross polarization of the present invention in the xoz plane at 31 GHz;

[0040] Figure 6 Schematic diagram of the main polarization and cross polarization of the present invention in the yoz plane at 31 GHz;

[0041] In the figure, 1 is the top metal conductor, 2 is the resonant cavity dielectric layer, 3 is the middle metal conductor, 4 is the upper dielectric layer, 5 is the middle adhesive layer, 6 is the lower dielectric layer, 7 is the bottom metal conductor, 8 is the metal inner conductor layer, 9 is the metallized through hole, 10 is the slot hole, 11 is the coupling slot, and 12 is the H-shaped radiation slot. Detailed implementation manners

[0042] The present invention will be further clarified below in conjunction with the accompanying drawings and specific implementation manners. It should be understood that the following specific implementation manners are only used to illustrate the present invention and not to limit the scope of the present invention. After reading the present invention, various equivalent modifications made by those skilled in the art fall within the scope defined by the appended claims of this application.

[0043] Please refer to Figure 1 As shown, the present invention discloses a back cavity slot antenna based on a substrate integrated coaxial line, which sequentially includes a top metal conductor 1, a resonant cavity dielectric layer 2, a middle metal conductor 3, an upper dielectric layer 4, a middle adhesive layer 5, a lower dielectric layer 6, and a bottom metal conductor 7 from top to bottom in the vertical direction. In addition, a plurality of regularly arranged metallized through holes 9 that penetrate the substrate integrated coaxial line from top to bottom are provided. The coupling slot 11 is etched at the center of the surface of the middle metal conductor 3. Four slot holes 10 penetrate the substrate integrated waveguide structure from top to bottom, and the H-shaped radiation slot 12 is etched on the surface of the top metal conductor 1.

[0044] Refer to Figure 1-3 As shown, the feeding main body part of the antenna includes a metal inner conductor layer 8 and a coupling slot 11. The metal inner conductor layer 8 is located at the center of the middle adhesive layer 5. The metal inner conductor layer 8 is not short-circuited with the metallized through hole 9 and is in an open state. Electromagnetic energy is effectively coupled into the circular resonant cavity through the coupling slot 11 directly above, and the appropriate high-order mode in the resonant cavity is excited by the characteristic that the electric field directions at the slot edges of the coupling slot 11 must be in antiphase.

[0045] Refer to Figure 1-3As shown, the antenna radiator is an H-shaped radiation slot 12 etched on the surface of the top-layer metal conductor 1. The circular resonator of the substrate integrated waveguide is composed of four annularly distributed slot holes 10. The coupling slot 11 couples the electromagnetic energy of the substrate integrated coaxial line into the circular resonator and excites appropriate higher-order modes. According to the electric field pattern of the excited higher-order modes, the H-shaped radiation slot 12 that can radiate in phase is etched on the top-layer metal conductor 1. The etched slot is provided in the H-shaped radiation slot for convenient field pattern control, and the etched slot is used to cut the surface current, thereby radiating electromagnetic waves.

[0046] Among them, the intermediate adhesive layer 5 tightly connects the upper dielectric layer 4 and the lower dielectric layer 6, and the upper dielectric layer 4, the lower dielectric layer 6 and the intermediate adhesive layer 5 completely overlap. The intermediate-layer metal conductor 3 covers the upper surface of the upper dielectric layer 4, and the bottom-layer metal conductor 7 covers the lower surface of the lower dielectric layer 6. A metal inner conductor layer 8 is provided between the lower surface of the upper dielectric layer 4 and the intermediate adhesive layer 5. The metallized vias 9 are symmetrically arranged on both sides and in front of the metal inner conductor layer 8 and penetrate the entire substrate integrated coaxial line from top to bottom. The metallized vias on both sides and in front form a closed structure with good shielding performance; the slot holes 10 are arranged in a ring and penetrate the entire substrate integrated waveguide resonator structure from top to bottom to realize the design of the circular resonator.

[0047] The intermediate-layer metal conductor 3, the upper dielectric layer 4, the intermediate adhesive layer 5, the lower dielectric layer 6, the bottom-layer metal conductor 7 and the metal inner conductor layer 8 are sequentially arranged to form a substrate integrated coaxial line; the top-layer metal conductor 1, the intermediate-layer metal conductor 3 and the slot holes 10 are sequentially arranged to form a substrate integrated waveguide circular resonator.

[0048] In the z-axis direction, the coupling slot 11 and the metal inner conductor layer 8 are vertically arranged. To effectively realize the coupling of electromagnetic energy, the coupling slot also needs to be located at the center of the radiation slot to excite the corresponding mode in the resonator cavity.

[0049] In this embodiment, the metal materials used are all copper. A back cavity slot antenna based on a substrate integrated coaxial line is realized by PCB processing technology. Copper is plated on the upper surface of the resonator dielectric layer 2 to form the top-layer metal conductor 1, copper is plated on the lower surface of the resonator dielectric layer 2 to form the intermediate-layer metal conductor 3, copper is plated on the lower surface of the upper dielectric layer 4 to form the metal inner conductor layer 8, and copper is plated on the lower surface of the lower dielectric layer 6 to form the bottom-layer metal conductor 7; the upper dielectric layer 4, the lower dielectric layer 6 and the intermediate adhesive layer 5 are laminated, and finally holes are drilled at the corresponding positions of the metallized vias 9, and electrical connection is realized through copper plating between the holes.

[0050] Substrate integrated coaxial line (SICL) is a transmission line technology developed based on substrate integrated waveguide (SIW). It retains the closed - type characteristics of SIW, but introduces a metal inner conductor layer in the dielectric. Electromagnetic energy is transmitted along the inner conductor rather than diffusing throughout the entire structure. Therefore, the fundamental transmission mode of SICL is the quasi - TEM mode, that is, the characteristic impedance of SICL is independent of frequency. So, using SICL for feeding is easy to integrate with other circuits and can reduce the loss during energy propagation. By etching a coupling slot directly above the inner conductor, electromagnetic energy can be effectively coupled into the resonant cavity, realizing the integration, miniaturization, and high - efficiency of the back - cavity antenna feeding.

[0051] The circular resonant cavity structure in this invention is realized by substrate integrated waveguide (SIW). Using SIW to realize the resonant cavity structure can greatly solve the practical problems existing in traditional resonant cavities. While retaining the advantages of the original resonant cavity structure, it also realizes the low - profile and low - cost of the antenna.

[0052] In the feeding network, it is realized by substrate integrated coaxial line (SICL) and coupling slots. Substrate integrated coaxial line transmits the quasi - TEM mode, and electromagnetic energy is concentrated on the inner conductor. The structural size is not limited by the low - frequency cut - off frequency. Using substrate integrated coaxial line as the feeding structure can adopt PCB processing technology with the upper - layer cavity structure, reducing costs and facilitating mass production and use.

[0053] For effectively feeding the substrate integrated waveguide resonant cavity structure using substrate integrated coaxial line, this invention adopts slot - coupling feeding. According to the target higher - order mode to be excited, slots are etched at appropriate positions for coupling excitation. According to the specific phase relationship of the coupling slots, the corresponding higher - order mode can be highly efficiently excited to a great extent. Compared with traditional feeding methods, it can more accurately excite the corresponding mode and is more flexible in application.

[0054] In this example, it is mainly divided into the substrate integrated coaxial line slot - coupling feeding part and the circular resonant cavity radiation part. The diameter of the metallized vias 9 on both sides of the metal inner conductor layer in the substrate integrated coaxial line is 0.4 mm, the hole pitch between adjacent metallized vias in each row is 0.6 mm, and the distance between the metallized vias on both sides is 4.85 mm. Appropriate via size and pitch can reduce the processing difficulty and achieve the purpose of preventing electromagnetic wave leakage at the same time; the length of the coupling slot 11 etched on the intermediate - layer metal conductor 3 is 3.97 mm, and the width is 0.2 mm. The electromagnetic energy in the substrate integrated coaxial line is coupled into the resonant cavity through the coupling slot 11, and the coupling slot is etched at the geometric center of the intermediate - layer metal conductor 3; the distance from the coupling slot 11 to the end of the metal inner conductor layer 8 is 1.5 mm, and the distance from the end of the metal inner conductor layer 8 to the metallized via 9 is 0.3 mm.

[0055] The diameter of the slot hole 10 forming the substrate integrated waveguide circular resonator is 0.6 mm. The four slot holes are annularly distributed, and the radian of each slot hole is 86°. The radius of the circular resonator formed by the slot holes 10 is 6.48 mm. By controlling the radius of the circular resonator, the resonance frequency of the high-order mode of the resonator can be changed. Therefore, after determining the size of the resonator, the resonance frequency of the back cavity slot antenna is also determined. The structure of the slot hole has the same electromagnetic shielding effect as the regularly arranged metallized vias. The geometric centers of the circular resonator and the coupling slot 11 coincide along the z-axis. In addition, the geometric centers of both of them and the H-shaped radiation slot 12 etched on the top metal conductor 1 also coincide along the z-axis. The slot width of the H-shaped radiation slot 12 is 0.8 mm, the sizes of the left and right two slots are the same, the length is 10 mm, and the length of the short slot in the middle is 1.55 mm.

[0056] The dielectric layer includes a resonator dielectric layer 2, an upper dielectric layer 4, an intermediate adhesive layer 5, and a lower dielectric layer 6. The resonator dielectric layer 2 is Rogers 5880 with a thickness of 0.787 mm. Both the upper dielectric layer 4 and the lower dielectric layer 6 are Rogers 5880 printed circuit boards with a thickness of 0.254 mm. The intermediate adhesive layer 4 is Rogers 4450F with a thickness of 0.1 mm. The impedance of the substrate integrated coaxial line is determined by the substrate thickness and the width of the metal inner conductor layer. The port impedance of the present invention is 50 ohms, which is convenient for integration with other integrated circuit structures.

[0057] In this example, in order to measure the antenna performance, a simulation software is used to perform parameter simulation on the back cavity slot antenna based on the substrate integrated coaxial line. Since the antenna operates in free space, after the antenna model is created, the antenna boundary is set to the ideal boundary condition, and the antenna input port is set to the waveguide port, and the performance in the 25 - 33 GHz frequency band is analyzed and calculated.

[0058] Refer to Figure 4 As shown, the reflection coefficient and gain of the antenna in the corresponding frequency band are given. Obviously, the -10 dB impedance bandwidth of the antenna is 25.85 - 31.27 GHz, the relative bandwidth is 19%, the peak gain within the bandwidth is 6.98 dBi, and the bandwidth of this antenna is greatly improved compared with the impedance bandwidth of the traditional slot antenna.

[0059] Refer to Figure 5-6 As shown, the main polarization and cross-polarization gain patterns of the xoz plane and the yoz plane of the antenna at a frequency of 31 GHz are given: The main polarization radiation gain in the maximum radiation direction of the antenna in both the xoz plane and the yoz plane is more than 30 dBi greater than the cross-polarization radiation gain, and the cross-polarization performance is good.

[0060] In summary, a cavity-backed slot antenna based on substrate integrated coaxial line in the present invention has the characteristics of miniaturization, high integration, high gain and low profile.

[0061] Those of ordinary skill in the art should understand that the discussion of any embodiment above is only exemplary and is not intended to imply that the scope of the present invention is limited to these examples; under the concept of the present invention, the technical features in the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations in different aspects of the present invention as described above, which are not provided in detail for the sake of brevity.

[0062] The present invention is intended to cover all such substitutions, modifications and variations that fall within the broad scope of the claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A substrate integrated coaxial line based cavity-backed slot antenna, characterized in that, It includes a top metal conductor, a resonator dielectric layer, an intermediate metal conductor, an upper dielectric layer, a metal inner conductor layer, an intermediate adhesive layer, a lower dielectric layer, and a bottom metal conductor which are arranged from top to bottom; A through circular resonator is provided on the top metal conductor and the resonator dielectric layer, and the circular resonator includes slot holes arranged annularly and evenly; An H-shaped radiation slot is etched on the top metal conductor, and the H-shaped radiation slot is located inside the circular resonator; A coupling slot is etched at the center of the intermediate metal conductor, and the coupling slot is located inside the circular resonator; The metal inner conductor layer is located at the center of the upper surface of the intermediate adhesive layer; Through metallized vias are provided on the upper dielectric layer, the intermediate adhesive layer, the lower dielectric layer, and the bottom metal conductor; In the same plane, several metallized vias are in a rectangular shape with one end open; In the z-axis direction, the coupling slot and the metal inner conductor layer are cross-arranged and are respectively located in the metallized vias arranged in a rectangular shape.

2. The substrate integrated coaxial line based back cavity slot antenna according to claim 1, characterized in that, The geometric center of the H-shaped radiation slot and the geometric center of the circular resonator coincide along the z-axis.

3. The substrate integrated coaxial line based back cavity slot antenna according to claim 2, characterized in that, The coupling slot is a horizontal slot; The geometric center of the coupling slot and the geometric center of the circular resonator coincide in the z-axis direction.

4. The substrate integrated coaxial line-based back cavity slot antenna according to claim 1, characterized in that, In the z-axis direction, the coupling slot and the metal inner conductor layer are vertically arranged.

5. The substrate integrated coaxial line based back cavity slot antenna according to claim 1, characterized in that, The rectangular metallized vias are symmetrically arranged on both sides and in front of the metal inner conductor layer, and the metal inner conductor layer is spaced from the metallized vias located in front.

6. The substrate integrated coaxial line based back cavity slot antenna according to claim 1, characterized in that, The diameter of the metallized via is 0.4 mm, and the hole pitch between adjacent metallized vias in each row is 0.6 mm.

7. The substrate integrated coaxial line based back cavity slot antenna according to claim 1, characterized in that, The top metal conductor, the intermediate metal conductor, the bottom metal conductor, and the metal inner conductor layer are all made of copper.

8. The substrate integrated coaxial line based back cavity slot antenna according to claim 1, characterized in that, The resonator dielectric layer is a Rogers 5880 printed circuit board with a thickness of 0.787 mm, the upper dielectric layer and the lower dielectric layer are both Rogers 5880 printed circuit boards with a thickness of 0.254 mm, and the intermediate adhesive layer is a Rogers4450F printed circuit board with a thickness of 0.1 mm.

9. A processing method for a back cavity slot antenna based on substrate integrated coaxial line, characterized in that It includes an upper component and a lower component which are connected up and down; Wherein, The processing of the upper component includes: S11. Copper is plated on the upper surface of the resonator dielectric layer to form the top metal conductor, and copper is plated on the lower surface of the resonator dielectric layer to form the intermediate metal conductor; S12. The H-shaped radiation slot is etched on the surface of the top metal conductor, and a through circular resonator is provided on the top metal conductor and the resonator dielectric layer; S13. A coupling slot is etched in the center of the intermediate layer metal conductor; The processing of the lower component includes: S21. Copper is plated on the lower surface of the upper dielectric layer to form a metal inner conductor layer, and copper is plated on the lower surface of the lower dielectric layer to form a bottom layer metal conductor; S22. The upper dielectric layer, the lower dielectric layer, and the intermediate adhesive layer are laminated, and finally holes are drilled at the corresponding positions of the metallized vias, and electrical connection is achieved through copper plating between the holes.

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