A compact waveguide slot antenna

Abstract

The application relates to the technical field of antenna devices, and particularly discloses a compact waveguide slot antenna, which comprises a substrate integrated cavity, an antenna radiation slot layer, a feed source excitation structure and an equivalent magnetic wall; the antenna radiation slot layer is arranged on the lower surface of the substrate integrated cavity; the feed source excitation structure is arranged below the substrate integrated cavity; and the distributed equivalent magnetic wall is formed through a medium-air interface of a long-side sidewall of the waveguide. The compact waveguide slot antenna is excited by adopting a microstrip line coupling slot feed mode to generate a TE20 mode, and the equivalent magnetic wall is introduced to optimize the surface current distribution of the substrate integrated waveguide, reduce the influence of the position deviation of the radiation slot caused by the machining error on the antenna performance, significantly reduce the size of the antenna, reduce the number of metal through holes, and reduce the machining cost, so that the antenna has the advantages of compact structure and stable performance.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of antenna devices, and particularly relates to a compact waveguide slot antenna. BACKGROUND

[0002] The waveguide slot antenna is an antenna that transmits electromagnetic waves by using a waveguide and realizes outward radiation of energy by opening a slot on the wall of the waveguide. The substrate integrated waveguide slot antenna has the advantages of easy manufacturing and integration, and is widely applied to wireless communication systems and radar systems. When the antenna works at a high frequency, the processing errors of the radiation slot position and size, the metal via hole diameter and the spacing in the manufacturing process will affect the performance of the antenna. One solution is to use the TE20 mode to replace the traditional main mode to reduce the number of metal vias and simplify the structure of the antenna array. However, the antenna feeding mode working in the TE20 mode is relatively complex, and the size of a single antenna array element is twice the size of the main mode antenna, which is not conducive to the miniaturization and integration of the antenna. The equivalent magnetic wall structure can simulate the magnetic wall characteristics at a specific position, change the propagation path and field distribution of electromagnetic waves in the waveguide, and can reduce the size of the original waveguide while maintaining or even improving the performance of the original waveguide. The introduction of the equivalent magnetic wall structure in the substrate integrated waveguide can replace the equivalent electric wall composed of metal vias, thereby reducing the number of metal vias in the substrate integrated waveguide and reducing the processing cost and processing error of the metal vias. Therefore, the application introduces the equivalent magnetic wall into the substrate integrated waveguide slot antenna and proposes a compact waveguide slot antenna, which realizes miniaturization while maintaining good performance. This antenna has the characteristics of compact structure, good stability and strong directivity, and has a wide application in the fields of radar, communication and the like. SUMMARY

[0003] The application aims to provide a compact waveguide slot antenna to solve the problems in the background.

[0004] In order to achieve the above-mentioned purpose, the application adopts the following technical scheme: a compact waveguide slot antenna, comprising a substrate integrated cavity, an antenna radiation slot layer, a feed source excitation structure and an equivalent magnetic wall. The antenna radiation slot layer is arranged on the lower surface of the substrate integrated waveguide and is used to realize the radiation of electromagnetic energy; the feed source excitation structure is arranged below the substrate integrated cavity and excites the electromagnetic mode in the cavity through a specific feeding mode; and the equivalent magnetic wall is arranged on the side of the long side (along the wave propagation direction) of the substrate integrated cavity and is used to limit the distribution of the electromagnetic field, thereby realizing the miniaturization and performance optimization of the waveguide structure.

[0005] Preferably, the substrate integrated cavity body is a dielectric plate, the upper and lower sides of the dielectric plate are metal layers, and metal vias are arranged in the dielectric plate to connect the metal layers on the upper and lower sides of the dielectric plate, thereby forming a substrate integrated waveguide; based on the substrate integrated waveguide structure of the TE20 mode, equivalent magnetic walls are arranged at the positions of 1 / 4 and 3 / 4 of the short side of the waveguide in the direction of the long side of the waveguide, only the field distribution in the range of 1 / 4 to 3 / 4 of the short side of the waveguide structure of the TE20 mode is retained, the effective field distribution area can be reduced by 50%, and the in-phase of the radiation slot layer current in the wavelength range is ensured. The introduction of the equivalent magnetic wall reduces the cross-sectional area of the waveguide by 50%, effectively reducing the size of the antenna and improving the space utilization.

[0006] Preferably, the present application adopts a slot coupling feeding mode, the excitation slot is arranged at the geometric center of the antenna radiation slot layer, and a microstrip line coupling feeding mode is used to excite an electric field parallel to the narrow side direction of the slot at the excitation slot, and then a TE20 mode is excited in the substrate integrated cavity. The waveguide slot antenna is centrally fed, and the electric field is symmetrically distributed on both sides in the substrate integrated waveguide.

[0007] Preferably, the current distribution of the antenna radiation slot layer is in-phase in each half-wavelength range. The antenna radiation slot is arranged at the in-phase position of the current of the antenna radiation slot layer, and the slot is symmetrically arranged with respect to the feeding port. The shape and size of the radiation slot are adjusted as needed to optimize the radiation performance.

[0008] Preferably, an equivalent magnetic wall is introduced on the long side of the substrate integrated waveguide, which can be realized by the dielectric constant interface formed between the substrate dielectric and air, or by other ways of blocking the current of the side wall.

[0009] In summary, compared with the prior art, the present application has the following advantages:

[0010] 1. By introducing an equivalent magnetic wall in the long side direction of the substrate integrated waveguide (the wave propagation direction), the present application replaces the traditional metal via array, and compared with the traditional substrate integrated waveguide slot antenna based on the main mode or TE20 mode, the number of metal vias is effectively reduced, which helps to reduce the production cost and improve the manufacturing efficiency. At the same time, since the metal via array is removed in the wave propagation direction and only the metal via array in the short side direction of the waveguide is retained, the influence of the position deviation of the metal via in the manufacturing process on the performance of the antenna is reduced, thereby improving the process controllability and stability of the antenna.

[0011] 2, The application utilizes the electromagnetic field distribution characteristics of the TE20 mode in the central part of the waveguide, so that the waveguide surface current is in phase distribution in every 1 / 2 wavelength range. Through this characteristic, the sensitivity of the radiation slot size and its specific position to the antenna performance is reduced, thereby simplifying the design requirements of the radiation slot. At the same time, the influence of the process processing deviation of the radiation slot on the antenna performance is also significantly reduced, further improving the production consistency and practicability of the antenna.

[0012] 3, The application introduces an equivalent magnetic wall, so that the actual size of the short side of the waveguide is only half of the size of the short side of the traditional TE20 mode waveguide, greatly reducing the overall cross-sectional area of the waveguide. While being compact in structure, the manufacturing cost of the antenna is further reduced. In addition, this design has high radiation performance and small size advantages, which is suitable for the application requirements of sparse antenna arrays, easy to integrate into complex radio frequency systems, and shows good engineering practicability and expansibility. BRIEF DESCRIPTION OF DRAWINGS

[0013] Figure 1 A schematic diagram of a compact waveguide slot antenna according to the application.

[0014] Figure 2 A schematic diagram of a compact waveguide slot antenna structure according to the application.

[0015] Figure 3 A schematic diagram of the cross-sectional (side view) electric field distribution and surface current distribution of the substrate integrated waveguide, the upper part is a TE20 mode substrate integrated waveguide, and the lower part is a substrate integrated waveguide according to the application.

[0016] Figure 4 A graph of the electric field intensity distribution of the substrate integrated waveguide according to the application.

[0017] Figure 5 A current vector diagram of the radiation slot layer in the substrate integrated waveguide according to the application.

[0018] Figure 6 An S11 characteristic diagram of a compact waveguide slot antenna according to the application.

[0019] Figure 7 A beam pattern diagram of a compact waveguide slot antenna according to the application at 10 GHz.

[0020] Figure 8 A schematic diagram of a 1x2 antenna array composed of waveguide slot antennas according to the application.

[0021] Figure 9 An S11 characteristic diagram of a 1x2 antenna array composed of waveguide slot antennas according to the application.

[0022] Figure 10The beam pattern of the waveguide slot antenna group 1x2 antenna array at 10GHz. DETAILED DESCRIPTION

[0023] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0024] Please refer to Figure 1 and Figure 2 , the present application provides a technical solution:

[0025] A compact waveguide slot antenna comprises, from top to bottom, a top metal layer 1 made of copper, a substrate integrated cavity 2 made of FR4 dielectric material with a dielectric constant of 4.4 and a loss tangent of 0.02, an antenna radiation slot layer 3 with a copper excitation slot 4 at the geometric center of the antenna radiation slot layer, and a microstrip line coupling excitation structure 5 comprising an RF4 dielectric plate and a microstrip line transmission line with an input impedance of 50 ohms.

[0026] The top metal layer 1 of the substrate integrated cavity 2 is connected to the antenna radiation slot layer 3 through a periodic array of metal vias to form an electromagnetic shield connection and a substrate integrated waveguide. The center frequency of the antenna in this embodiment is set to 10GHz, and the substrate integrated waveguide structure size is 14mmx32.4mmx0.785mm. The metal via diameter is 0.6mm, and the pitch is 1mm. An equivalent magnetic wall 6 is arranged on the long side of the substrate integrated cavity 2 to constrain the distribution of the electromagnetic field along the long side.

[0027] In an embodiment of the present application, the optimized slot coupling feeding mechanism is as follows:

[0028] The excitation slot 4 adopts an "H" shaped structure to realize electromagnetic coupling from the microstrip line to the substrate integrated waveguide and is arranged at the geometric center of the antenna radiation slot layer 1. The slot width is set to 1.47mm, and the "H" shaped structure has a height of 4.16mm and a width of 4.15mm. The "H" shaped excitation slot can reduce the coupling aperture and reduce the influence of the feeding microstrip line. Through the microstrip line coupling feeding mode, the TE20 mode can be excited inside the substrate integrated cavity 2.

[0029] The equivalent magnetic wall used in this embodiment realizes the miniaturization scheme as follows:

[0030] The equivalent magnetic wall 6 is realized through the dielectric interface formed between the substrate dielectric and air with a significant difference in dielectric constant.

[0031] According to the electromagnetic field theory and waveguide theory, when the electric field in the waveguide is completely symmetrically distributed about the symmetry plane, the symmetry plane is an equivalent magnetic wall. If an equivalent magnetic wall is artificially set along the symmetry plane, the electromagnetic field pattern in the waveguide remains consistent with the original electromagnetic field pattern. As shown in FIG. 1, Figure 3 Figure 3 The upper part shows the schematic diagram of the electric field and surface current distribution of the TE20 mode substrate integrated waveguide cross section. The electric field in the waveguide is symmetrically distributed about the center axis in the opposite direction, and the electric field on the left and right sides of the center axis is completely symmetric about the 1 / 4 and 3 / 4 positions of the short side (x direction) respectively. Figure 3 The lower part shows the schematic diagram of the electric field and surface current distribution of the substrate integrated waveguide cross section proposed by the present application. The substrate integrated waveguide proposed by the present application is based on the TE20 mode waveguide structure. The equivalent magnetic wall 6 is distributed along the long side (y direction) at the 1 / 4 and 3 / 4 positions of the short side. Only the field distribution in the range from 1 / 4 to 3 / 4 of the short side of the TE20 mode waveguide structure is retained. The effective field distribution area can be reduced by 50%, and the current in the radiation slot layer is ensured to be in phase within 1 / 2 wavelength. Figure 4 、 Figure 5 The electric field intensity distribution diagram and the current vector diagram of the radiation slot layer of the substrate integrated waveguide after introducing the equivalent magnetic wall are shown in FIG. 2 and FIG. 3 respectively. It can be seen that the electric field energy is concentrated near the magnetic wall, the current is in phase within half a wavelength, and the current is strongest near the center axis of the waveguide. The introduction of the equivalent magnetic wall reduces the cross-sectional area of the waveguide by 50%, effectively reducing the size and weight of the antenna, and improving the space utilization.

[0032] The radiation slot setting scheme adopted in this embodiment is as follows:

[0033] A 2x2 rectangular longitudinal radiation slot 7 is arranged in the antenna radiation slot layer 3 for radiation. The radiation slot 7 is located in the current in-phase position of the antenna radiation slot layer 3, which can effectively reduce the sensitivity of the antenna performance to the size and specific position of the radiation slot, thereby simplifying the design and manufacturing. The slots are symmetrically distributed about the feed port to ensure the symmetry of the electromagnetic radiation direction and the good directivity pattern characteristics of the antenna. The length of the radiation slot is 14.82 mm, the width is 2.16 mm, and the distance between the center of the radiation slot and the center axis of the waveguide is 4.9 mm.

[0034] The position and size of the opening on the waveguide will introduce admittance in the waveguide equivalent circuit, affecting the coupling efficiency between the slot and the waveguide and the radiation efficiency of the antenna. A pair of metal through holes is symmetrically arranged on both sides of the "H" shaped excitation slot for tuning, so as to achieve better impedance matching. The diameter of the metal through hole is 0.6 mm, and the center distance from the equivalent magnetic wall is 4.21 mm.

[0035] The key performance parameters of this embodiment are as follows:​

[0036] The effective size of the single-antenna unit is 14mm×32.4mm×1.57mm (0.47λ×1.08λ×0.05λ), and the electrical size is small.

[0037] As shown in FIG. 3, Figure 6 the S11 characteristic of the antenna is shown. Figure 6 The S11 characteristic of the antenna is shown, and the impedance bandwidth of -10dB is about 840MHz (9.44GHz-10.28GHz).

[0038] As shown in FIG. 5, Figure 7 the radiation pattern characteristic of the antenna at 10GHz is shown. Figure 7 The radiation pattern characteristic of the antenna at 10GHz is shown, and the peak gain of the antenna is 6.27dB, and the E-plane -3dB beam width is 42°.

[0039] The array expansion implementation of the embodiment is as follows:

[0040] The antenna can be used to construct an antenna array as a basic radiation unit. Figure 8 A 1×2 antenna array composed of two above-described antennas is shown, in which the microstrip feed structure is designed as a half-power divider structure, and a quarter impedance transformation section is applied to realize impedance matching between the 50-ohm microstrip line and the antenna. The distance between the two antenna array elements is 40.1mm, and the overall size of the 1×2 antenna array is 14mm×72.5mm×1.57mm (0.47λ×2.42λ×0.05λ).

[0041] As shown in FIG. 8, Figure 9 the S11 characteristic of the 1×2 antenna array is shown. Figure 9 The S11 characteristic of the 1×2 antenna array is shown, and the impedance bandwidth of -10dB is about 1120MHz (9.68GHz-10.80GHz).

[0042] As shown in FIG. 10, Figure 10 the radiation pattern characteristic of the 1×2 antenna array at 10GHz is shown. Figure 10 The radiation pattern characteristic of the 1×2 antenna array at 10GHz is shown, and the array realizes a gain improvement of 9.25dB, the E-plane -3dB beam width is narrowed to 20°, and the sidelobe level is lower than -3.5dB.

[0043] The above merely describes the preferred specific implementation of the present application, but the protection scope of the present application is not limited thereto, and any person skilled in the art can make equivalent replacements or changes to the technical solution and the inventive concept of the present application within the technical range disclosed by the present application, which should be covered within the protection scope of the present application.

Claims

1. A compact waveguide slot antenna, characterized in that: This includes the substrate integrated cavity, antenna radiation slot layer, feed excitation structure, and equivalent magnetic wall; The antenna radiation slot layer is disposed on the lower surface of the substrate integrated waveguide, and has a plurality of radiation slots thereon for realizing the radiation of electromagnetic waves. The feed excitation structure is located below the substrate integrated waveguide. The equivalent magnetic wall is located on the long side of the substrate integrated cavity. The equivalent magnetic wall is located at 1 / 4 and 3 / 4 positions in the short side direction of the waveguide and is distributed along the long side direction. Only the field distribution in the range of 1 / 4 to 3 / 4 of the short side of the TE20 mode waveguide structure is retained. The equivalent magnetic wall is realized through the dielectric constant interface formed between the substrate medium and the air. The surface current of the antenna radiation slot layer is in phase in each half-wavelength range. The substrate integrated cavity body is a dielectric substrate with metal layers above and below it. Metal vias are located inside the dielectric substrate to connect the metal layers above and below the cavity, together forming a substrate integrated waveguide. Based on the TE20 mode substrate integrated waveguide structure, equivalent magnetic walls are placed along the long side at 1 / 4 and 3 / 4 of the short side of the waveguide. Only the field distribution within the range of 1 / 4 to 3 / 4 of the short side of the TE20 mode waveguide structure is retained, which can reduce the effective field distribution area by 50% and ensure that the radiation slot layer current is in phase within the wavelength range. The introduction of the equivalent magnetic walls reduces the cross-sectional area of ​​the waveguide by 50%, effectively reducing the size and weight of the antenna and improving space utilization.

2. The compact waveguide slot antenna according to claim 1, characterized in that: The feeding method is slot coupling feeding. The excitation slot is located at the center of the bottom metal layer of the substrate integrated waveguide. The electric field parallel to the narrow side of the slot is excited at the excitation slot by microstrip line coupling feeding, and then the TE20 mode is excited in the substrate integrated cavity. The waveguide slot antenna is center-fed and the electric field is symmetrically distributed on both sides in the substrate integrated waveguide.

3. The compact waveguide slot antenna according to claim 1, characterized in that: The antenna radiation slots are located in the antenna radiation slot layer where the current is in the same direction, and the slots are placed symmetrically about the feed port.

4. The compact waveguide slot antenna according to claim 1, characterized in that: The shape and size of the radiation slits are adjustable to accommodate different radiation performance requirements.

5. A compact waveguide slot antenna according to claim 1, characterized in that: An equivalent magnetic wall is introduced into the long sidewall of the substrate integrated waveguide. The equivalent magnetic wall can be realized by the dielectric constant interface formed between the substrate medium and the air.

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