Substrate integrated coaxial line-based cavity-backed slot antenna and processing method

Abstract

The invention discloses a cavity-backed slot antenna based on a substrate integrated coaxial line and a processing method. The cavity-backed slot antenna comprises a substrate integrated coaxial line, a feed structure of a coupling slot, a substrate integrated waveguide circular resonant cavity formed by four slot holes, and an H-shaped radiation slot. An up-and-down stacked structure is adopted, the substrate integrated coaxial line is arranged at the bottommost portion, the coupling gap is located over the substrate integrated coaxial line, the geometric center of the coupling gap coincides with the geometric center of the substrate integrated waveguide circular resonant cavity above the coupling gap along the z axis, and the H-shaped radiation gap is etched in top metal of the circular resonant cavity. The coupling gap is adopted for feeding, electromagnetic energy in the substrate integrated coaxial line can be coupled into the circular resonant cavity, and a high-order mode in the resonant cavity is excited. According to the invention, a substrate integrated coaxial line slot coupling technology is adopted, effective excitation of a high-order mode in the circular resonant cavity is realized, the bandwidth is expanded, and low profile and integration of the antenna are realized.

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; 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. An H-shaped radiation slot is etched on the top metal conductor, and the H-shaped radiation slot is located in the circular resonant cavity; A coupling slot is etched at the center of the intermediate metal conductor, and the coupling slot is located in the circular resonant cavity. The metal inner conductor layer is located at the center of the upper surface of the middle bonding layer. The upper dielectric layer, the middle adhesive layer, the lower dielectric layer and the bottom metal conductor are provided with through metalized through holes. In the same plane, several metallized through holes are rectangular with one end open. In the z-axis direction, the coupling gap and the metal inner conductor layer are arranged crosswise and are respectively located in the metallized through holes arranged in a rectangular shape.

[0007] The geometric center of the H-shaped radiation slot coincides with the geometric center of the circular resonant cavity along the z-axis.

[0008] The coupling gap is a transverse gap, The geometric center of the coupling gap coincides with the geometric center of the circular resonant cavity in the z-axis direction.

[0009] In the z-axis direction, the coupling gap and the metal inner conductor layer are arranged vertically.

[0010] The rectangular metallized through holes are symmetrically arranged on both sides and the front of the metal inner conductor layer, and the metal inner conductor layer is spaced apart from the metallized through holes located in the front.

[0011] The diameter of the metallized through hole is 0.4 mm, and the hole spacing between adjacent metallized through holes in each row is 0.6 mm.

[0012] The top metal conductor, the middle metal conductor, the bottom metal conductor and the inner metal conductor layer are all made of copper.

[0013] The resonant cavity dielectric layer is a Rogers 5880 printed circuit substrate with a thickness of 0.787 mm, the upper dielectric layer and the lower dielectric layer are both Rogers 5880 printed circuit substrates with a thickness of 0.254 mm, and the middle adhesive layer is a Rogers 4450F printed circuit substrate with a thickness of 0.1 mm.

[0014] A method for processing a cavity-backed slot antenna based on a substrate-integrated coaxial line, comprising an upper component and a lower component connected up and down; in, Upper component processing includes: 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; S12, etching an H-shaped radiation gap on the surface of the top metal conductor, and setting a through circular resonant cavity on the top metal conductor and the resonant cavity dielectric layer; S13, etching a coupling gap at the center of the intermediate layer metal conductor; The following components are processed: 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; S22, laminating the upper dielectric layer, the lower dielectric layer and the middle adhesive layer, and finally drilling holes at corresponding positions of the metallized through holes, and achieving electrical connection by copper plating between the holes.

[0015] The present invention has the following beneficial effects: 1. The present invention is based on a substrate-integrated coaxial line design with a reduced cross-section. By etching a coupling gap just above the metal inner conductor layer of the substrate-integrated coaxial line, the electromagnetic energy in the substrate-integrated coaxial line is coupled to the circular resonant cavity above, which can effectively excite high-order modes in the resonant cavity.

[0016] 2. The stacked structure of substrate-integrated coaxial line coupling slot feeding and substrate-integrated waveguide circular resonant cavity is conducive to the integrated design of antenna and microwave millimeter wave circuit.

[0017] 3. By etching an H-shaped radiation slot on the top metal of the circular resonant cavity and exciting the higher-order mode through the coupling slot, efficient radiation of electromagnetic waves can be achieved by etching the slot at the appropriate position according to the electric field structure of the excitation mode, and the design of a high-gain antenna can be realized. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a structural diagram of the present invention; Figure 2 is a schematic diagram of the feeding structure; Figure 3 is a schematic diagram of the top metal conductor; Figure 4 It is a reflection coefficient and gain schematic diagram of the present invention; Figure 5 It is a schematic diagram of the main polarization and cross polarization of the xoz plane at 31GHz of the present invention; Figure 6 It is a schematic diagram of the main polarization and cross polarization of the yoz plane at 31GHz of the present invention; 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, 11 is the coupling gap, and 12 is the H-type radiation gap. DETAILED DESCRIPTION

[0019] The present invention is further explained below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the following specific embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention. After reading the present invention, various equivalent forms of modifications to the present invention by those skilled in the art all fall within the scope defined by the claims attached to this application.

[0020] See also Figure 1 As shown, the present invention discloses a cavity-backed slot antenna based on a substrate-integrated coaxial line, which includes, from top to bottom in the vertical direction, a top metal conductor 1, a resonant cavity dielectric layer 2, an intermediate metal conductor 3, an upper dielectric layer 4, an intermediate adhesive layer 5, a lower dielectric layer 6 and a bottom metal conductor 7. In addition, a plurality of regularly arranged metallized through holes 9 penetrating the substrate-integrated coaxial line from top to bottom are provided, a coupling slot 11 is etched at the center of the surface of the intermediate metal conductor 3, four slots 10 penetrate the substrate-integrated waveguide structure from top to bottom, and an H-shaped radiation slot 12 is etched on the surface of the top metal conductor 1.

[0021] See also Figure 1-3 As shown, the feeding body 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 intermediate adhesive layer 5. The metal inner conductor layer 8 is not short-circuited with the metallized through-hole 9 and is in an open circuit state. The electromagnetic energy is effectively coupled to the circular resonant cavity through the coupling slot 11 directly above, and the electric field direction of the slot edge of the coupling slot 11 must be in reverse phase to excite the appropriate high-order mode in the resonant cavity.

[0022] See also Figure 1-3 As shown, the antenna radiator is an H-shaped radiation slot 12 etched on the surface of the top metal conductor 1. The circular resonant cavity of the substrate integrated waveguide is composed of four annularly distributed slots 10. The coupling slot 11 couples the electromagnetic energy of the substrate integrated coaxial line into the circular resonant cavity and excites the appropriate high-order mode. According to the electric field diagram of the excited high-order mode, an H-shaped radiation slot 12 that can radiate in phase is etched on the top metal conductor 1. The H-shaped radiation slot is set to facilitate the control of the field shape. The etched slot is used to cut the surface current and then radiate the electromagnetic wave.

[0023] Among them, the middle 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 middle adhesive layer 5 completely overlap. The middle layer metal conductor 3 covers the upper surface of the upper dielectric layer 4, and the bottom 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 middle adhesive layer 5. The metallized through holes 9 are symmetrically arranged on both sides and the front of the metal inner conductor layer 8, and penetrate the entire substrate integrated coaxial line from top to bottom. The metallized through holes on both sides and the front form a closed structure with good shielding properties; the slots 10 are arranged in a ring, and penetrate the entire substrate integrated waveguide resonant cavity structure from top to bottom, realizing the design of a circular resonant cavity.

[0024] The middle layer metal conductor 3, the upper dielectric layer 4, the middle 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 middle layer metal conductor 3 and the slot 10 are sequentially arranged to form a substrate integrated waveguide circular resonant cavity.

[0025] In the z-axis direction, the coupling slot 11 is arranged perpendicular to the metal inner conductor layer 8. To effectively realize the coupling of electromagnetic energy, the coupling slot also needs to be located at the center of the radiation slot to realize the excitation of the corresponding mode in the resonant cavity.

[0026] The metal materials used in this embodiment are all copper. A cavity-backed slot antenna based on a substrate integrated coaxial line is realized through PCB processing technology. Copper is plated on the upper surface of the resonant cavity dielectric layer 2 to form a top metal conductor 1, copper is plated on the lower surface of the resonant cavity dielectric layer 2 to form an intermediate metal conductor 3, copper is plated on the lower surface of the upper dielectric layer 4 to form a metal inner conductor layer 8, and copper is plated on the lower surface of the lower dielectric layer 6 to form a bottom metal conductor 7; the upper dielectric layer 4, the lower dielectric layer 6 and the intermediate adhesive layer 5 are laminated into shape, and finally holes are drilled at the corresponding positions of the metallized through holes 9, and electrical connection is achieved by copper plating between the holes.

[0027] Substrate integrated coaxial line SICL is a transmission line technology developed on the basis of substrate integrated waveguide SIW. It retains the closed characteristics of SIW, but introduces a metal inner conductor layer in the medium. The electromagnetic energy is transmitted along the inner conductor instead of being diffused throughout the structure. Therefore, the transmission fundamental mode of SICL is a quasi-TEM mode, that is, the characteristic impedance of SICL is independent of frequency. Therefore, SICL is used for feeding, which is easy to integrate with other circuits and reduce the loss in the energy propagation process. Etching a coupling gap just above the inner conductor can effectively couple the electromagnetic energy into the resonant cavity, realizing the integration, miniaturization and high efficiency of cavity-backed antenna feeding.

[0028] The circular resonant cavity structure in the present invention is implemented by substrate integrated waveguide (SIW). Using SIW to implement the resonant cavity structure can greatly solve the practical problems existing in the traditional resonant cavity, and on the basis of retaining the advantages of the original resonant cavity structure, it also realizes the low profile and low cost of the antenna.

[0029] In the feeding network, substrate integrated coaxial line (SICL) and coupling gap are used. The substrate integrated coaxial line transmits quasi-TEM mode, and the electromagnetic energy is concentrated on the inner conductor. The structural size is not limited by the low-frequency cutoff frequency. The substrate integrated coaxial line is used as the feeding structure, and the PCB processing technology can be used with the upper cavity structure to reduce costs and facilitate mass production.

[0030] In order to effectively feed the substrate integrated waveguide resonant cavity structure using the substrate integrated coaxial line, the present invention adopts slot coupling feeding. According to the target high-order mode to be excited, the slots at the appropriate positions are etched for coupling excitation. According to the specific phase relationship of the coupling slots, the corresponding high-order modes can be efficiently excited to a great extent. Compared with the traditional feeding method, the corresponding mode can be excited more accurately and the application is more flexible.

[0031] In this example, it is mainly divided into a substrate integrated coaxial line slot coupling feeding part and a circular resonant cavity radiation part. The diameter of the metallized through holes 9 located on both sides of the metal inner conductor layer in the substrate integrated coaxial line is 0.4mm, the hole spacing between adjacent metallized through holes in each row is 0.6mm, and the distance between the metallized through holes on both sides is 4.85mm. The appropriate through hole size and hole spacing can reduce the processing difficulty and achieve the purpose of preventing electromagnetic wave leakage; the length of the coupling slot 11 etched in the intermediate layer metal conductor 3 is 3.97mm and the width is 0.2mm. The electromagnetic energy in the substrate integrated coaxial line is coupled to 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 1.5mm, and the distance from the end of the metal inner conductor layer 8 to the metallized through hole 9 is 0.3mm.

[0032] The diameter of the slots 10 constituting the substrate integrated waveguide circular resonant cavity is 0.6mm. The four slots are distributed in a ring shape, and the arc of each slot is 86°. The radius of the circular resonant cavity formed by the slots 10 is 6.48mm. By controlling the radius of the circular resonant cavity, the resonant frequency of the high-order mode of the resonant cavity can be changed. Therefore, after determining the size of the resonant cavity, the resonant frequency of the back cavity slot antenna has also been determined. The structure of the slots has the same electromagnetic shielding effect as the regularly arranged metallized through holes. The geometric centers of the circular resonant cavity and the coupling slot 11 coincide along the z-axis. In addition, the geometric centers of the two coincide along the z-axis with the H-type radiation slot 12 etched on the top metal conductor 1. The slot width of the H-type radiation slot 12 is 0.8mm. The left and right slots are of the same size and length of 10mm. The short slot in the middle is 1.55mm long.

[0033] The dielectric layer includes a resonant cavity dielectric layer 2, an upper dielectric layer 4, an intermediate bonding layer 5 and a lower dielectric layer 6. The resonant cavity dielectric layer 2 is Rogers 5880 with a thickness of 0.787 mm, the upper dielectric layer 4 and the lower dielectric layer 6 are both Rogers 5880 printed circuit substrates with a thickness of 0.254 mm, and the intermediate bonding layer 4 is Rogers 4450F with a thickness of 0.1 mm. The impedance of the substrate integrated coaxial line is determined by the thickness of the substrate 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.

[0034] In this example, in order to measure the antenna performance, simulation software is used to perform parameter simulation on the cavity-backed slot antenna based on substrate-integrated coaxial line. Since the antenna works in free space, after the antenna model is created, the antenna boundary is set to the ideal boundary condition, the antenna input port is set to the waveguide port, and the performance of the 25-33GHz frequency band is analyzed and calculated.

[0035] See also Figure 4 As shown in the figure, the reflection coefficient and gain of the antenna in the corresponding frequency band are given. Obviously, the -10dB impedance bandwidth of the antenna is 25.85-31.27GHz, the relative bandwidth is 19%, and the peak gain within the bandwidth is 6.98dBi. Compared with the impedance bandwidth of the traditional slot antenna, the bandwidth of this antenna is greatly improved.

[0036] See also Figure 5-6 As shown, the main polarization and cross-polarization gain radiation patterns of the xoz plane and yoz plane of the antenna at a frequency of 31 GHz are given: the main polarization radiation gain of the antenna in the maximum radiation direction of either the xoz plane or the yoz plane is more than 30 dBi greater than the cross-polarization radiation gain, and the cross-polarization performance is good.

[0037] In summary, the 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.

[0038] Those skilled in the art should understand that the discussion of any of the above embodiments is merely illustrative 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 may be combined, the steps may be implemented in any order, and there are many other variations of the different aspects of the present invention as described above, which are not provided in detail for the sake of simplicity.

[0039] 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 principles of the present invention should be included in the protection scope of the present invention.

Claims

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

2. The cavity-backed slot antenna based on substrate integrated coaxial line according to claim 1, characterized in that: The geometric center of the H-shaped radiation slot coincides with the geometric center of the circular resonant cavity along the z-axis.

3. The cavity-backed slot antenna based on substrate integrated coaxial line according to claim 2, characterized in that: The coupling gap is a transverse gap, The geometric center of the coupling gap coincides with the geometric center of the circular resonant cavity in the z-axis direction.

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

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

6. The cavity-backed slot antenna based on substrate integrated coaxial line according to claim 1, characterized in that: The diameter of the metallized through hole is 0.4 mm, and the hole spacing between adjacent metallized through holes in each row is 0.6 mm.

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

8. The cavity-backed slot antenna based on substrate integrated coaxial line according to claim 1, characterized in that: The resonant cavity dielectric layer is a Rogers 5880 printed circuit substrate with a thickness of 0.787 mm, the upper dielectric layer and the lower dielectric layer are both Rogers 5880 printed circuit substrates with a thickness of 0.254 mm, and the middle adhesive layer is a Rogers 4450F printed circuit substrate with a thickness of 0.1 mm.

9. A method for processing a cavity-backed slot antenna based on a substrate-integrated coaxial line, characterized in that: It includes an upper component and a lower component connected up and down; in, Upper component processing includes: 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; S12, etching an H-shaped radiation gap on the surface of the top metal conductor, and setting a through circular resonant cavity on the top metal conductor and the resonant cavity dielectric layer; S13, etching a coupling gap at the center of the intermediate layer metal conductor; The following components are processed: 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; S22, laminating the upper dielectric layer, the lower dielectric layer and the middle adhesive layer, and finally drilling holes at corresponding positions of the metallized through holes, and achieving electrical connection by copper plating between the holes.

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