A broadband low-profile dual-polarization omnidirectional antenna

Abstract

The present invention proposes a broadband, low-profile, dual-polarization omnidirectional antenna, comprising a horizontally polarized radiator, a metal coupling patch, a vertically polarized radiator, and a metal floor, arranged sequentially from top to bottom. The horizontally polarized radiator comprises a dielectric substrate, and horizontally polarized radiating patches and a feed network printed on its upper and lower surfaces. The metal coupling patch comprises a metal disk and a metal ring nested on its circumference. The horizontally polarized radiating patch and the metal disk are connected via a first short-circuit line, and the metal ring and the horizontally polarized radiating patch are connected to the metal floor via four second short-circuit lines and four third short-circuit lines, respectively. The present invention achieves coupling between the horizontally polarized radiator and the vertically polarized radiator by short-circuiting the horizontally polarized radiating patch and the metal disk, and the metal ring and the horizontally polarized radiating patch and the metal floor, thereby extending the electrical length of the antenna, effectively broadening the antenna's bandwidth, and reducing the antenna's profile.

Description

Technical Field

[0001] The invention belongs to the technical field of microwave antennas and relates to a broadband low-profile dual-polarization omnidirectional antenna which can be used for indoor communications and mobile base stations. Background Art

[0002] Mobile communications continue to evolve. The 2G / 3G / LTE frequency bands still play an indispensable role in current mobile communications, and 5G and 2G / 3G / LTE will likely operate in parallel for a long time in the future. Consequently, the demand for antennas capable of simultaneously covering these frequency bands is increasing. Dual-polarized omnidirectional antennas are widely used for indoor communications due to their robustness against multipath fading and high channel capacity. These antennas improve indoor signal coverage and system capacity, particularly in low-profile applications, meeting the current demand for multi-antenna technology.

[0003] A dual-polarized omnidirectional antenna typically consists of a vertically polarized VP omnidirectional antenna and a horizontally polarized HP omnidirectional antenna. The VP antenna can be implemented as a monopole, featuring a single-cone shape for broadband performance and loaded with a metal top-loading disk for improved impedance matching. An array of multiple dipole antennas and a power divider feed network can serve as an alternative to the HP antenna. An array of multiple tapered slot antennas can also achieve horizontal omnidirectional radiation with a wider bandwidth. Depending on the application requirements, the dual-polarization configuration can be achieved with the HP antenna placed above, below, or embedded within the VP antenna.

[0004] To improve antenna performance and meet wider bandwidth requirements while maintaining a smaller size, patent application publication number CN115863950A, titled "A Dual-Polarized Omnidirectional Antenna for Indoor Distribution," includes a vertically polarized unit and a horizontally polarized unit. The vertically polarized unit comprises two vertically placed metal patches, a top-loaded metal disk, and an input port for the vertically polarized unit. The horizontally polarized unit comprises a dielectric substrate, a metal ground plane, and a dielectric resonator. A feeding structure is provided on the lower surface of the dielectric substrate. The dielectric resonator is annular and has a truncated cone-shaped notch in its center. A pair of curved metal oscillators are symmetrically positioned above the dielectric substrate on either side of the metal ground plane. The curved metal oscillators comprise two oscillator arms and open-circuit branches, and four parasitic patches are symmetrically positioned on the outer sides of the curved metal oscillators. This invention reduces the antenna's planar dimensions while ensuring wideband omnidirectional radiation. However, due to the lack of coupling loading between the vertically polarized unit and the horizontally polarized unit, the overlap bandwidth is relatively narrow, at only 30%, and the profile remains high. Summary of the Invention

[0005] The purpose of the present invention is to overcome the defects of the above-mentioned prior art and propose a broadband low-profile dual-polarization omnidirectional antenna to solve the technical problems of narrow bandwidth and high profile in the prior art.

[0006] To achieve the above objectives, the technical solution adopted by the present invention includes a horizontally polarized radiator 1, a metal coupling patch 2, a vertically polarized radiator 3 and a metal floor 4 arranged in sequence from top to bottom; the horizontally polarized radiator 1 includes a dielectric substrate 11 and horizontally polarized radiating patches 12 and a feeding network 13 printed on its upper and lower surfaces; the metal coupling patch 2 includes a metal disc 21 and a metal ring 22 nested on its circumference; the horizontally polarized radiating patch 12 and the metal disc 21 are connected through a first short-circuit line 5, and the metal ring 22 and the horizontally polarized radiating patch 12 are connected to the metal floor 4 through four second short-circuit lines 6 and four third short-circuit lines 7, respectively.

[0007] As an optimization, the dielectric substrate 11 and the metal floor 4 are both circular in shape, and the center normals of the dielectric substrate 11 , the metal floor 4 and the metal coupling patch 2 coincide with each other.

[0008] As an optimization, the horizontally polarized radiation patch 12 includes a circular patch 121 and four centrally symmetrically distributed dipole antenna units 122 and a microstrip line 123 connected thereto; four first rectangular slots 124 are etched on the circular patch 121; the dipole antenna unit 122 adopts a quasi-T-shaped structure with an arc-shaped transverse arm, a rectangular notch is etched in the middle position of the transverse arm, a second rectangular slot 125 is etched on the longitudinal arm, and a third rectangular slot 126 is etched between the second rectangular slot 125 and the bottom of the rectangular notch; an arc-shaped director 127 is printed on each of the edges of the center of the four dipole antenna units 122 near the circumference of the dielectric substrate 11.

[0009] As an optimization, four arc-shaped parasitic patches 8 are printed on the lower surface of the dielectric substrate 11 , and the four arc-shaped parasitic patches intersect with the projections of the four microstrip lines 123 respectively.

[0010] As an optimization, the horizontally polarized radiation patch 12 includes four centrosymmetrically distributed microstrip lines 123 on a circular patch 121 , which are respectively located on the angle bisectors between adjacent dipole antenna units 122 .

[0011] As an optimization, the four centrosymmetrically distributed microstrip lines 123 are connected to the metal floor 4 via four third short-circuit lines 7 respectively.

[0012] As an optimization, the center of the horizontally polarized radiation patch 12 is located on the center normal of the dielectric substrate 11 .

[0013] As an optimization, the feeding network 13 adopts a one-to-four power divider, whose input port 131 is connected to an external coaxial line, and the ends of the four output ports are each connected to a reverse extension branch 132. The four output ports respectively pass through the third rectangular slots 126 etched on the four dipole antenna units 122 to achieve coupled feeding of the horizontally polarized radiation patch 12.

[0014] As an optimization, the centers of the metal disk 21 and the metal ring 22 of the metal coupling patch 2 are both located on the central axis of the vertically polarized radiator 3 .

[0015] As an optimization, the vertically polarized radiator 3 adopts a hollow inverted disk-cone structure, and the diameter of the disk-cone bottom is smaller than the diameter of the metal ring 22 .

[0016] Compared with the prior art, the present invention has the following advantages:

[0017] The present invention connects the horizontally polarized radiating patch and the metal disk through a first short-circuit line. The metal ring and the horizontally polarized radiating patch are connected to the metal floor through four second short-circuit lines and four third short-circuit lines, respectively. This achieves coupling between the horizontally polarized radiator and the vertically polarized radiator, thereby creating equivalent capacitance and equivalent inductance, and extending the electrical length of the antenna. Compared with the existing technology, this effectively broadens the bandwidth of the antenna while reducing the cross-section of the antenna. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the overall structure of the present invention;

[0019] Figure 2 for Figure 1 Side view of;

[0020] Figure 3 Schematic diagram of the structure of the horizontally polarized radiation patch of the present invention;

[0021] Figure 4 Schematic diagram of the structure of the feeding network of the present invention;

[0022] Figure 5 is the impedance matching coefficient of the vertical polarization element before and after the loaded microstrip line and the short-circuit line in the embodiment of the present invention |S 11 |、Impedance matching coefficient of horizontal polarization element before and after loading microstrip line and short circuit line|S 22 | and the isolation between horizontally polarized components and vertically polarized components |S 21 |Graph showing the relationship between the curve and the frequency;

[0023] Figure 6 The normalized radiation patterns of the vertically polarized element in the embodiment of the present invention operating at 2 GHz, 2.7 GHz, 3.3 GHz, and 3.6 GHz are shown in FIG.

[0024] Figure 7 The normalized radiation patterns of the vertically polarized element in the embodiment of the present invention operating at 2 GHz, 2.7 GHz, 3.3 GHz, and 3.6 GHz are shown in the H-plane xoy plane.

[0025] Figure 8 The normalized radiation patterns of the horizontally polarized element in the embodiment of the present invention operating at 2 GHz, 2.7 GHz, 3.3 GHz, and 3.6 GHz are shown in FIG.

[0026] Figure 9 The normalized radiation patterns of the horizontally polarized element in the embodiment of the present invention operating at 2 GHz, 2.7 GHz, 3.3 GHz, and 3.6 GHz are shown in the H-plane xoy plane.

[0027] Figure 10 The impedance matching coefficients of the vertical polarization element when the metal ground radius is expanded from 90 mm to 150 mm and 200 mm in the embodiment of the present invention are shown in FIG. 11 Frequency variation curve and impedance matching coefficient of horizontal polarization element|S 22 |Curve graph showing changes with frequency. DETAILED DESCRIPTION

[0028] The present invention will be described in further detail below with reference to the accompanying drawings and specific embodiments.

[0029] Reference Figure 1 and Figure 2 The present invention includes a horizontally polarized radiator 1, a metal coupling patch 2, a vertically polarized radiator 3 and a metal floor 4 arranged in sequence from top to bottom; the horizontally polarized radiator 1 includes a dielectric substrate 11 and horizontally polarized radiating patches 12 and a feeding network 13 printed on the upper and lower surfaces thereof; the metal coupling patch 2 includes a metal disc 21 and a metal ring 22 nested on its circumference; the horizontally polarized radiating patch 12 is connected to the metal disc 21 through a first short-circuit line 5, and the metal ring 22 and the horizontally polarized radiating patch 12 are connected to the metal floor 4 through four second short-circuit lines 6 and four third short-circuit lines 7, respectively.

[0030] The dielectric substrate 11 has a circular cross-section and a thickness of 1 mm. Made of Arlon AD255A, it has a relative dielectric constant of 2.55 and a loss tangent of 0.0015. The horizontally polarized radiator is excited by an external 50Ω coaxial line through a feed network 13. The metal disk 21 connects the first short-circuit line 5 to the horizontally polarized radiating patch 12, while the metal ring 22 connects the second short-circuit line 6 to the metal floor 4. The annular gap in between provides capacitive loading, improving impedance matching for the vertically polarized element.

[0031] The vertically polarized radiator 3 is excited by a 50Ω coaxial line connected to its lower surface. The metal coupling patch 2 and the second short-circuit line 6 act on the vertically polarized radiator 3, acting as capacitive and inductive loads, respectively. The principle of operation is that when the vertically polarized radiator is operating, the current on the surface of the radiator 3 is coupled to the metal coupling patch 2 and conducted to the metal ground plane 4 by the second short-circuit line 6, thereby increasing the electrical length of the antenna and broadening the bandwidth of the vertically polarized radiator. The first short-circuit line 5 connects the center of the metal disk 21 with the center of the upper horizontally polarized radiating patch 12. The third short-circuit line 7 connects the upper horizontally polarized radiating patch 12 to the metal ground plane 4 via a microstrip line 123. This connection makes the horizontally polarized radiating patch a top load for the vertically polarized radiator. The principle of operation is that when the vertically polarized radiator is operating, the surface current of the radiator 3 is coupled to the metal coupling patch 2, further conducted to the horizontally polarized radiating patch 12 by the first short-circuit load 5, and then conducted back to the metal ground plane 4 by the third short-circuit line 7. This also increases the electrical length of the antenna and broadens the bandwidth. The radiator 3 is an inverted cone structure with a vacuum inside, that is, a metal shell that is circular in top view and isosceles trapezoidal in side view. When the vertically polarized radiator 3 is working, the current is concentrated on the outer surface of the radiator, so that the vertically polarized radiator has good omnidirectionality.

[0032] Reference Figure 3 The horizontally polarized radiation patch 12 includes a circular patch 121 and four centrally symmetrically distributed dipole antenna units 122 and a microstrip line 123 connected thereto. The microstrip line 123 extends to the circumferential edge of the dielectric substrate 11 to connect the horizontally polarized radiation patch 12 with the third short-circuit line 7; four first rectangular slots 124 are etched on the circular patch 121, which are used to improve the high-frequency radiation pattern of the horizontally polarized radiator; the dipole antenna unit 122 adopts a quasi-T-shaped structure with an arc-shaped transverse arm, a rectangular notch is etched in the middle of the transverse arm, and a second rectangular slot 12 is etched on the longitudinal arm. 5. A third rectangular slot 126 is etched between the second rectangular slot 125 and the bottom of the rectangular notch. The third rectangular slot 126 connects the second rectangular slot and the rectangular notch and is used for the feeding network 13 to perform microstrip-slot coupling feeding on the horizontally polarized radiating patch 12. The width of the second rectangular slot 125 is greater than that of the third rectangular slot 126, and its function is to act as a resonator to improve the impedance matching of the horizontally polarized element. The center of the four dipole antenna units 122 is close to the edge of the circumference of the dielectric substrate 11, and each is printed with an arc-shaped director 127 to improve the impedance matching of the horizontally polarized element.

[0033] Reference Figure 4The feeding network 13 uses a one-to-four power divider. The feeding network 13 consists of a 50Ω microstrip line, an 88Ω microstrip line, a 110Ω microstrip line, a 100Ω microstrip line, and a reverse extension branch 132. The feeding starts from the input end 131, and the distance and impedance to each third rectangular slot 126 are the same, so that currents of equal amplitude and phase flow through each radiating element 122, thereby achieving good omnidirectionality. The parasitic structure 8 is located between the projections of two adjacent radiating elements 122, and its line coincides with the microstrip line 123. Its function is to improve the impedance matching of the horizontally polarized element.

[0034] The following is a further explanation of the technical effects of the present invention in conjunction with simulation experiments:

[0035] 1. Experimental conditions and content:

[0036] The simulation software ANSYS Electronics Desktop v.18.2 was used to simulate the electrical characteristics of the present invention, including the impedance matching coefficient of the vertically polarized radiator before and after loading the microstrip line and the short-circuit line|S 11 |、Impedance matching coefficient of horizontal polarization radiator before and after loading microstrip line and short circuit|S 22 | and the isolation between horizontally polarized radiators and vertically polarized radiators |S 21 The curve relationship diagram of | with frequency, the normalized radiation patterns of the E-plane xoz and H-plane xoy of the vertically polarized radiator and the horizontally polarized radiator working at frequencies of 2GHz, 2.7GHz, 3.3GHz, and 3.6GHz under the final model, and the |S11| and |S22| after the size of the metal floor are changed are simulated. The results are shown in the figure. Figure 5-10 shown.

[0037] 2. Analysis of experimental results:

[0038] Reference Figure 5 , the antenna impedance matching coefficient in the frequency range of 1.6GHz-3.7GHz |S 11 |≤-10dB, impedance matching coefficient in the frequency range of 1.95GHz-3.67GHz|S 22 |≤-10dB, the full-band isolation is higher than 20dB. At the same time, it can be seen that before the introduction of microstrip lines and short-circuit lines, the antenna impedance matching coefficient |S between 2.4GHz and 3.0GHz 11 |>-10dB, and before and after the introduction of microstrip line and short circuit line, |S 22The change is minimal, indicating that the introduction of the stripline fully improves the impedance matching of the vertically polarized radiator without adversely affecting the impedance matching of the horizontally polarized radiator. After the introduction of the microstrip and short-circuit lines, the dual-polarized antenna's vertically polarized radiator bandwidth is 1.6 GHz to 3.7 GHz (79.2%), and the horizontally polarized radiator bandwidth is 1.95 GHz to 3.67 GHz (60.9%).

[0039] Reference Figure 6-7 , Figure 6 (a) is the E-plane xoz radiation pattern of a vertically polarized radiator operating at frequencies of 2 GHz and 2.7 GHz. Figure 6 (b) is the E-plane xoz radiation pattern of the vertically polarized radiator operating at frequencies of 3.3 GHz and 3.6 GHz; Figure 7 (a) is the H-plane xoy radiation pattern of the vertically polarized radiator working at frequencies of 2 GHz and 2.7 GHz. Figure 7 (b) shows the H-plane xoy-plane radiation pattern of a vertically polarized radiator operating at 3.3 GHz and 3.6 GHz. At 2 GHz, 2.7 GHz, 3.3 GHz, and 3.6 GHz, the nonuniformity of the normalized H-plane xoy-plane radiation pattern of the vertically polarized radiator is less than 4 dB. The maximum gain of the normalized E-plane xoz-plane radiation pattern varies between 4.2 dBi and 6.8 dBi, with a maximum gain of 6.8 dBi.

[0040] Reference Figure 8-9 , Figure 8 (a) is the E-plane xoz radiation pattern of a horizontally polarized radiator operating at frequencies of 2 GHz and 2.7 GHz. Figure 8 (b) is the E-plane xoz radiation pattern of the horizontally polarized radiator operating at frequencies of 3.3 GHz and 3.6 GHz; Figure 9 (a) is the H-plane xoy radiation pattern of a horizontally polarized radiator operating at frequencies of 2 GHz and 2.7 GHz. Figure 9 (b) shows the H-plane xoy-plane radiation pattern of a horizontally polarized radiator operating at 3.3 GHz and 3.6 GHz. At 2 GHz, 2.7 GHz, 3.3 GHz, and 3.6 GHz, the nonuniformity of the normalized H-plane xoy-plane radiation pattern of the horizontally polarized radiator is less than 5 dB. The maximum gain of the normalized E-plane xoz-plane radiation pattern varies between 4.8 dBi and 7.0 dBi, with a maximum gain of 7.0 dBi.

[0041] Reference Figure 10 , Figure 10 (a) The impedance matching coefficient of the vertically polarized radiator after the metal ground radius is expanded from the original 90mm to 150mm and 200mm |S 11 |Graph of frequency variation, Figure 10 (b) The impedance matching coefficient of the horizontally polarized radiator after the metal ground radius is expanded from the original 90 mm to 150 mm and 200 mm |S 22 |The curve graph changes with frequency. It can be seen that after the metal ground radius is expanded from the original 90mm to 150mm and 200mm in the present invention, the impedance matching coefficient of the vertically polarized radiator and the horizontally polarized radiator|S 11 |、|S 22 The frequency variation curve is basically consistent with the original simulation result. It can be concluded that the antenna of the present invention has good tolerance for the problem of changes in the antenna installation environment.

Claims

1. A broadband low-profile dual-polarization omnidirectional antenna, comprising a horizontally polarized radiator (1), a metal coupling patch (2), a vertically polarized radiator (3) and a metal floor (4) arranged in sequence from top to bottom; the horizontally polarized radiator (1) comprises a dielectric substrate (11) and horizontally polarized radiating patches (12) printed on the upper and lower surfaces thereof, and a feed network (13); the metal coupling patch (2) comprises a metal disc (21) and a metal ring (22) nested on the circumference thereof; and is characterized in that: The horizontally polarized radiation patch (12) and the metal disk (21) are connected via a first short-circuit line (5), and the metal ring (22) and the horizontally polarized radiation patch (12) are connected to the metal floor (4) via four second short-circuit lines (6) and four third short-circuit lines (7), respectively.

2. The broadband low-profile dual-polarization omnidirectional antenna according to claim 1, characterized in that: The dielectric substrate (11) and the metal floor (4) both have circular plate shapes, and the center normals of the dielectric substrate (11), the metal floor (4) and the metal coupling patch (2) coincide with each other.

3. The broadband low-profile dual-polarization omnidirectional antenna according to claim 2, characterized in that: The horizontally polarized radiation patch (12) comprises a circular patch (121) and four dipole antenna units (122) and a microstrip line (123) connected thereto and symmetrically distributed at the center thereof; four first rectangular slots (124) are etched on the circular patch (121); the dipole antenna unit (122) adopts a quasi-T-shaped structure with an arc-shaped transverse arm, a rectangular notch is etched in the middle of the transverse arm, a second rectangular slot (125) is etched on the longitudinal arm, and a third rectangular slot (126) is etched between the second rectangular slot (125) and the bottom of the rectangular notch; and an arc-shaped director (127) is printed on each of the four dipole antenna units (122) at the center close to the edge of the circumference of the dielectric substrate (11).

4. The broadband low-profile dual-polarization omnidirectional antenna according to claim 3, characterized in that: The dielectric substrate (11) has four arc-shaped parasitic patches (8) printed on its lower surface, and the four arc-shaped parasitic patches respectively intersect with the projections of the four microstrip lines (123).

5. The broadband low-profile dual-polarization omnidirectional antenna according to claim 3, characterized in that: The horizontally polarized radiation patch (12) comprises four centrosymmetrically distributed microstrip lines (123) on a circular patch (121) that are respectively located on the angle bisectors between adjacent dipole antenna units (122).

6. The broadband low-profile dual-polarization omnidirectional antenna according to claim 3, characterized in that: The four centrosymmetrically distributed microstrip lines (123) are respectively connected to the metal floor (4) via four third short-circuit lines (7).

7. The broadband low-profile dual-polarization omnidirectional antenna according to claim 3, characterized in that: The center of the horizontally polarized radiation patch (12) is located on the center normal line of the dielectric substrate (11).

8. The broadband low-profile dual-polarization omnidirectional antenna according to claim 3, characterized in that: The feeding network (13) adopts a one-to-four power splitter, wherein the input port (131) is connected to an external coaxial line, and the ends of the four output ports are respectively connected to a reverse extension branch (132). The four output ports respectively pass through the third rectangular slots (126) etched on the four dipole antenna units (122) to achieve coupled feeding of the horizontally polarized radiation patch (12).

9. The broadband low-profile dual-polarization omnidirectional antenna according to claim 1, characterized in that: The centers of the metal disc (21) and the metal ring (22) of the metal coupling patch (2) are both located on the central axis of the vertically polarized radiator (3).

10. The broadband low-profile dual-polarization omnidirectional antenna according to claim 1, characterized in that: The vertically polarized radiator (3) adopts a hollow inverted disk-cone structure, and the diameter of the disk-cone bottom is smaller than the diameter of the metal ring (22).

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