An end-fire antenna with stable wide-beam gain

Abstract

The present invention discloses an end-fire antenna with stable wide-beam gain, which relates to the technical field of antennas. It includes an additional cladding layer located on the upper layer and an antenna layer located on the lower layer; the antenna layer includes an SIW third-order ridge waveguide horn printed on a dielectric substrate, coaxial feeding, slow-wave structure, air vias, and an additional ground structure AGS; wherein the outer conductor of the coaxial feeding is electrically connected to the lower-layer metal of the SIW third-order ridge waveguide horn, and the inner conductor of the coaxial feeding is connected to the leftmost end of the first-order ridge of the third-order ridge in the SIW third-order ridge waveguide horn; the slow-wave structure is arranged around the ridge end of the third-order ridge, air vias are arranged in the dielectric extension part at the end of the SIW third-order ridge waveguide horn, and an additional ground structure AGS is loaded at the tail of the lower-layer dielectric substrate of the extension part. The present invention can achieve the regulation of electromagnetic waves, so as to realize the miniaturized design of the antenna while enabling the antenna to have stable gain and polarization characteristics, and at the same time solve the problem of beam upward deviation in a large metal environment.

Description

Technical Field

[0001] The present invention belongs to the technical field of antennas, and particularly relates to an end-fire antenna with stable gain in a wide beamwidth. Background Art

[0002] With the rapid development of wireless communication technologies and the continuous progress of technologies such as radar, early warning, detection, and guidance, antennas, as the core components of wireless systems, are also constantly evolving and play a crucial role in the overall performance of wireless communication systems. During use, the radiation direction of the antenna should be the same as the flight direction of the carrier, so the structure of an end-fire antenna is adopted. Due to the needs of daily use, the operating bandwidth of the antenna must be very wide, so some ordinary antenna structures cannot be used. Although some traditional antennas can achieve ultra-wideband characteristics and stable gain, in order to conform to the carrier system and at the same time take into account many issues such as miniaturization, polarization, and in-band pattern stability, the development of end-fire antennas faces challenges. Summary of the Invention

[0003] In view of the above problems, the present invention proposes an end-fire antenna with stable gain in a wide beamwidth. By loading a dielectric cladding, a slow-wave structure, air vias, etc., the regulation of electromagnetic waves is realized, so that while realizing the miniaturized design of the antenna, the antenna has stable gain and polarization characteristics, and at the same time solves the problem of beam upward deviation in a large metal environment.

[0004] The above object is achieved by the following technical solutions:

[0005] An end-fire antenna with stable gain in a wide beamwidth of the present invention includes an additional cladding located in the upper layer and an antenna layer located in the lower layer; the antenna layer includes an SIW third-order ridge waveguide horn printed on a dielectric substrate, coaxial feeding, a slow-wave structure, air vias, and an additional ground structure AGS; wherein the outer conductor of the coaxial feeding is electrically connected to the lower metal of the SIW third-order ridge waveguide horn, and the inner conductor of the coaxial feeding is connected to the leftmost end of the first-order ridge of the third-order ridge in the SIW third-order ridge waveguide horn; the slow-wave structure is arranged around the ridge end of the third-order ridge, air vias are arranged in the dielectric extension part at the end of the SIW third-order ridge waveguide horn, and an additional ground structure AGS is loaded at the tail of the lower dielectric substrate of the extension part.

[0006] Further, the slow-wave structure is realized by grooving the upper and lower surfaces of the SIW third-order ridge waveguide horn. Each groove is equivalent to a series inductor, and the space between adjacent grooves is equivalent to a parallel capacitor, where:

[0007] The inductance L is expressed as L = μ r h[ln(h / d)+1 / 2] / π;

[0008] The capacitance C is expressed as C = ε r h2 d / [4πk(h - 2d)(p - d)];

[0009] Where h is the height of the groove, d is the diameter of the groove, p is the spacing between adjacent grooves, μ r is the equivalent magnetic permeability of the medium, ε r is the equivalent dielectric constant of the medium, k = 9.0×10 9 N·m 2 / C 2 is the electrostatic constant;

[0010] Furthermore, calculate the propagation constant of the electromagnetic wave ω is the angular frequency;

[0011] Therefore, by adjusting the groove depth, groove diameter and the spacing between adjacent grooves of the slow-wave structure, the adjustment of the propagation constant of the electromagnetic wave is realized. And the number of grooves in different regions is different, so the equivalent shunt capacitance and series inductance are different. According to the calculation formula of the propagation constant of the electromagnetic wave, the propagation constants of the electromagnetic waves in different regions are different. Therefore, the phase of the electromagnetic waves reaching the aperture plane in different regions can be changed to realize the phase correction at the aperture plane.

[0012] Furthermore, the aperture of the air via changes in a gradient manner. Specifically, the aperture of the air vias in the middle column right at the horn mouth of the SIW third-order ridge waveguide horn is the smallest, and the aperture gradually increases towards both sides. The aperture change range is from 1.8 mm to 2.4 mm. The array arrangement of the air vias with a gradient change in aperture is equivalent to a dielectric plate with a gradually decreasing dielectric constant. According to the phase calculation formula where ψ is the phase that the electromagnetic wave passes through when propagating through the air via, ω is the angular frequency, μ r is the equivalent magnetic permeability of the medium, ε r is the equivalent dielectric constant of the medium, c is the speed of light in vacuum. The air via can provide a specific phase for the electromagnetic wave passing through it to compensate for the phase difference between the edge and the center position of the horn antenna aperture, thus realizing the improvement of the radiation pattern.

[0013] Furthermore, the additional structure AGS is composed of 4 mutually separated metal sheets, which is loaded on the right side of the lower surface metal plate. The extension length of the lower surface metal plate relative to the upper surface metal plate is 2 mm. The first-order metal sheet is spaced 0.08 mm from the lower surface metal plate, and the spacing between adjacent mutually separated metal sheets is also 0.08 mm.

[0014] Furthermore, the additional cladding includes an FR4 substrate layer with a dielectric constant of 4.4. Three spindle-shaped metal parasitic patches and a rectangular metal parasitic patch are provided on the lower surface of the substrate layer. A metal fence composed of metal patches and metallized vias arranged in a one-dimensional uniform period along the direction perpendicular to the aperture and a metal grid arranged in a two-dimensional uniform period along the aperture direction and the direction perpendicular to the aperture are provided on the upper surface of the substrate layer.

[0015] Furthermore, the diameter of the metallized vias in the metal fence is 0.4 mm, the width of the metal patches is 1.2 mm, and they are arranged at intervals of 1.3 mm; the diameter of the metallized vias in the metal grid is 0.4 mm. Along the aperture direction, the length of the metallized patches is 1.4 mm, with an interval of 1.5 mm, and along the direction perpendicular to the aperture, the width of the metallized patches is 1.2 mm, with an interval of 1.3 mm.

[0016] Furthermore, the additional cladding is connected to the antenna layer through a multi-layer board lamination technology.

[0017] Furthermore, the dielectric substrate of the antenna layer uses F4B with a dielectric constant of 2.2.

[0018] Compared with the prior art, the significant advantages of the present invention are as follows:

[0019] 1. By loading a dielectric cladding, the present invention realizes a miniaturized design, and improves the pattern deterioration problem caused by the miniaturized design by loading parasitic patches, slow-wave structures, and electromagnetic metamaterials, and has a smaller size.

[0020] 2. The present invention proposes an additional structure, which improves the problem of beam upward deviation in the presence of an extended floor, and has a more stable beam in the target airspace compared with traditional SIW antennas.

[0021] 3. By improving the beam, the present invention has a wider beam width compared with traditional SIW (Substrate integrated waveguide) antennas. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is a schematic diagram of the overall structure of the SIW horn antenna proposed by the present invention;

[0023] Figure 2 is a schematic diagram of the antenna layer proposed by the present invention, Figure 2 in which, (a) is a top view, and (b) is a cross-sectional view;

[0024] Figure 3 is a schematic diagram of the additional cladding proposed by the present invention, Figure 3 in which, (a) is a top view, and (b) is a cross-sectional view;

[0025] Figure 4 Current distribution before and after loading the slow-wave structure, (a) before loading (b) after loading;

[0026] Figure 5 Azimuth plane radiation pattern (7.5 GHz) before and after loading the slow-wave structure;

[0027] Figure 6 Radiation patterns (17 GHz) before and after loading the metamaterial, (a) elevation plane (b) azimuth plane;

[0028] Figure 7 Radiation pattern before loading AGS;

[0029] Figure 8 Radiation pattern after loading AGS;

[0030] Figure 9 Radiation patterns after loading AGS, (a) 7.5 GHz (b) 9.5 GHz (c) 17 GHz;

[0031] Figure 10 Elevation plane radiation pattern, (a) 6 - 12 GHz (b) 12 - 18 GHz;

[0032] Figure 11 Azimuth plane radiation pattern, (a) 6 - 12 GHz (b) 12 - 18 GHz;

[0033] Explanation of reference numerals: 1. Antenna layer; 2. Additional cladding; 1-1. SIW third-order ridge waveguide horn; 1-2. Coaxial feed; 1-3. Slow-wave structure; 1-4. Air via; 1-5. Additional ground structure AGS. Detailed implementation manners

[0034] The following combines the drawings to specifically illustrate a kind of ultra-wideband planar spiral antenna based on notch tunability of split-ring resonators proposed by the present invention with specific embodiments.

[0035] Figure 1 Schematic diagram of the overall structure of an end-fire antenna with wide beamwidth and stable gain proposed by the present invention, which mainly consists of two parts. The upper layer is the additional cladding 2, and the lower layer is the antenna layer 1. The two layers are connected by multi-layer board lamination technology.

[0036] Figure 2For the antenna layer 1 in the present invention, the dielectric substrate uses F4B with a dielectric constant of 2.2. It mainly consists of five parts printed on the dielectric substrate, namely the SIW third-order ridge waveguide horn 1-1, the coaxial feed 1-2, the slow-wave structure 1-3, the air via 1-4, and the additional ground structure AGS 1-5. Among them, the outer conductor of the coaxial feed 1-2 is electrically connected to the lower-layer metal of the SIW third-order ridge waveguide horn 1-1, and the inner conductor of the coaxial feed 1-2 is connected to the leftmost end of the first-order ridge of the SIW third-order ridge waveguide horn 1-1. The slow-wave structure 1-3 is arranged around the ridge end, the air via 1-4 is set in the dielectric extension part at the end of the SIW third-order ridge waveguide horn 1-1, and the additional ground structure AGS 1-5 is loaded at the tail of the lower floor of the extension part. The slow-wave structure is realized by sinking grooves on the upper and lower surfaces of the SIW. The adjacent metallized groove structures can be equivalent to an inductor and a capacitor. The inductor can be expressed as L = μ0h[ln(h / d)+1 / 2] / π, and the capacitor is expressed as C = ε0h 2 d / [4πk(h - 2d)(p - d)], where h is the height of the metallized groove, d is the diameter of the metallized groove, p is the spacing between adjacent metallized grooves, μ r is the equivalent magnetic permeability of the medium, ε r is the equivalent dielectric constant of the medium, k = 9.0×10 9 N·m 2 / C 2 is the electrostatic constant; and then the propagation constant of the electromagnetic wave can be calculated ω is the angular frequency. Therefore, by adjusting the groove depth, groove diameter, and the spacing between adjacent grooves of the slow-wave structure, the propagation constant of the electromagnetic wave can be adjusted. And the number of grooves in different regions is different, so the equivalent parallel capacitance and series inductance are different. According to the calculation formula of the electromagnetic wave propagation constant, the electromagnetic wave propagation constants in different regions are different. Therefore, the phase of the electromagnetic wave reaching the aperture surface in different regions can be changed to achieve phase correction at the aperture surface. At the same time, the slow-wave structure proposed in the present invention also has a field concentration effect. As the depth of the metal groove increases, the capacitance effect between the two adjacent upper and lower metal blocks will be enhanced, so that the electric field is distributed on the two sides of the metal block, and thus the purpose of adjusting the electric field intensity distribution of the aperture surface can be achieved, as Figure 4 shown. Combining the above two functions, the structure proposed in the present invention can achieve an increase in gain, as Figure 5As shown. Air vias with a gradient change in aperture are also loaded at the aperture of the SIW ridge waveguide horn. The aperture of the air vias changes in a gradient manner. Specifically, the aperture of the air vias in the middle column directly in front of the horn mouth of the SIW third-order ridge waveguide horn is the smallest, and the aperture gradually increases towards both sides. In this embodiment, the diameters of the air vias are 1.8 mm, 2.2 mm, and 2.4 mm respectively, showing a gradient change. Their array arrangement can be equivalent to a dielectric plate with a gradually decreasing dielectric constant, enabling electromagnetic waves to propagate from a high-dielectric-constant dielectric substrate to a low-dielectric-constant dielectric substrate and finally reaching free space. It can be equivalent to a metamaterial with a phase-shifting function, changing the equivalent dielectric constant of the medium. According to the phase calculation formula where ψ is the phase that the electromagnetic wave passes through when propagating through the air via, ω is the angular frequency, μ r is the equivalent magnetic permeability of the medium, and ε r is the equivalent dielectric constant of the medium, c is the speed of light in vacuum. The air via can provide a specific phase for the electromagnetic wave passing through it to compensate for the phase difference between the edge and the center position of the horn antenna aperture, achieving an improvement in the radiation pattern. As Figure 6 shown, it can be seen that after loading the metamaterial, the antenna gain value is effectively increased and the antenna beam width is expanded.

[0037] An additional ground structure AGS is loaded at the aperture edge. The proposed AGS is composed of 4 mutually separated metal sheets and is loaded on the right side of the lower surface metal plate. The lower surface metal plate extends 2 mm relative to the upper surface metal plate. The first-order metal sheet is spaced 0.08 mm from the lower surface metal plate, and the adjacent mutually separated metal sheets are also spaced 0.08 mm apart, effectively destroying the continuity of the ground plane. Through this additional ground structure, beam correction can be achieved. As Figure 7 , Figure 8 , Figure 9 shown, it can be seen that after loading the AGS, the problem of the upward deviation of the radiation pattern beam is effectively solved.

[0038] Figure 3The additional cladding in the present invention is made of FR4 with a dielectric constant of 4.4. It mainly consists of two parts, namely three spindle-shaped metal parasitic patches and a rectangular metal parasitic patch located on the lower surface, and a metal fence and a metal grid located on the upper surface. The metal fence is composed of metal patches and metallized vias arranged in a one-dimensional uniform period along the direction perpendicular to the aperture, and the metal grid is arranged in a two-dimensional uniform period along the aperture direction and the direction perpendicular to the aperture. The diameter of the metallized vias in the metal fence is 0.4 mm, the width of the metal patches is 1.2 mm, and the spacing is 1.3 mm. The diameter of the metallized vias in the metal grid is 0.4 mm. Along the aperture direction, the length of the metallized patches is 1.4 mm, the spacing is 1.5 mm, and along the direction perpendicular to the aperture, the width of the metallized patches is 1.2 mm, and the spacing is 1.3 mm. The parasitic patches are used to adjust the phase at the radiation aperture surface, suppress the generation of higher-order modes, and improve the radiation performance of the antenna. The metal fence suppresses the surface current at the edge of the upper surface of the SIW and suppresses the backward radiation brought by the upper surface, thereby improving the front-to-back ratio of the end-fire antenna at low frequencies. The final radiation pattern is as shown in Figure 10 , 11 . It can be seen that the backward radiation of the antenna is effectively reduced after loading the additional cladding.

[0039] The above is only the best embodiment of the present invention. However, the present invention is not limited to the above embodiments. The above specific implementation manners are merely illustrative and not restrictive. Under the inspiration of the present invention, those of ordinary skill in the art can also make many forms without departing from the purpose of the present invention and the scope protected by the claims. All of these fall within the protection scope of the present invention.

Claims

1. A wide beam gain stable end-fire antenna, characterized in that: It includes an additional covering layer located on the upper layer and an antenna layer located on the lower layer; the antenna layer includes a SIW third-order ridge waveguide horn printed on a dielectric substrate, a coaxial feed, a slow-wave structure, an air via and an additional ground structure AGS; The outer conductor of the coaxial feed is electrically connected to the lower metal layer of the SIW third-order ridge waveguide horn, and the inner conductor of the coaxial feed is connected to the leftmost end of the first-order ridge of the third-order ridge in the SIW third-order ridge waveguide horn; the slow-wave structure is arranged around the ridge end of the third-order ridge, an air via is provided at the dielectric extension part at the end of the SIW third-order ridge waveguide horn, and an additional ground structure AGS is loaded at the tail of the dielectric substrate under the extension part; The additional coating layer includes an FR4 substrate layer made of a dielectric constant of 4.4, the lower surface of the substrate layer is provided with three spindle-shaped metal parasitic patches and one rectangular metal parasitic patch, and the upper surface of the substrate layer is provided with a metal fence composed of metal patches and metallized vias arranged in a one-dimensional uniform periodic arrangement along a direction perpendicular to the aperture, and a metal grid arranged in a two-dimensional uniform periodic arrangement along the aperture direction and perpendicular to the aperture direction; The diameter of the metalized via in the metal fence is 0.4mm, the width of the metal patch is 1.2mm, and the metal patches are arranged at intervals of 1.3mm; the diameter of the metalized via in the metal grid is 0.4mm, along the caliber direction, the length of the metal patch is 1.4mm, the interval is 1.5mm, and the width of the metal patch in the direction perpendicular to the caliber is 1.2mm, and the interval is 1.3mm; The dielectric substrate of the antenna layer adopts F4B with a dielectric constant of 2.

2.

2. The wide beam gain stable end-fire antenna according to claim 1, characterized in that: The slow wave structure is realized by forming grooves on the upper and lower surfaces of the SIW third-order ridge waveguide horn. Each groove is equivalent to a series inductor, and adjacent grooves are equivalent to a parallel capacitor, wherein: Inductance L is expressed as L = μ r h[ln(h / d)+1 / 2] / π; Capacitance C is expressed as C = ε r h 2 d / [4πk(h-2d)(pd)]; Where h is the height of the sink, d is the diameter of the sink, p is the distance between adjacent sinks, μ r is the equivalent magnetic permeability of the medium, ε r is the equivalent dielectric constant of the medium, k = 9.0 × 10 9 N·m 2 / C 2 is the electrostatic force constant; Then calculate the propagation constant of electromagnetic waves ω is the angular frequency; Therefore, the electromagnetic wave propagation constant is adjusted by adjusting the groove depth, groove diameter and spacing between adjacent grooves of the slow-wave structure. The number of grooves in different areas is different, so the equivalent parallel capacitance and series inductance are different. According to the calculation formula of the electromagnetic wave propagation constant, the electromagnetic wave propagation constant in different areas is different, so the phase of the electromagnetic waves in different areas arriving at the aperture surface is changed to achieve phase correction at the aperture surface.

3. The wide beam gain stable end-fire antenna according to claim 1, characterized in that: The aperture gradient of the air vias is specifically that the aperture of the air vias in the middle of the horn of the SIW third-order ridge waveguide horn is the smallest, and the aperture gradually increases toward both sides, and the aperture variation range is 1.8mm-2.4mm. The array of the air vias with the aperture gradient variation is equivalent to a dielectric plate with a gradually decreasing dielectric constant. According to the phase calculation formula Among them, ψ is the phase of the electromagnetic wave propagating through the air via, ω is the angular frequency, μ r is the equivalent magnetic permeability of the medium, ε r is the equivalent dielectric constant of the medium, c is the speed of light in a vacuum, and the air via can provide a specific phase for the electromagnetic wave passing through it to compensate for the phase difference between the edge and center of the horn antenna aperture, thereby improving the radiation pattern.

4. The wide beam gain stable end-fire antenna according to claim 1, characterized in that: The additional covering layer is connected to the antenna layer by a multi-layer board lamination technology.

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