Low-profile dual-polarized omnidirectional full-duplex antenna

Abstract

The low-profile dual-polarized omnidirectional full-duplex antenna comprises a vertical omnidirectional antenna unit, a horizontal omnidirectional antenna unit and a second horizontal dielectric substrate, wherein a metal floor is printed on the lower surface of the second horizontal dielectric substrate; a first radiation arm and a second radiation arm which are connected through metalized via holes are printed on two plate surfaces of two crossed dielectric substrates in the vertical omnidirectional antenna unit respectively; a plurality of rectangular grooves which are arranged in a radial manner are etched in the metal floor; the horizontal omnidirectional antenna unit is connected with the metal floor through four metal columns. The four metal columns can enable coupling current generated by the vertical omnidirectional antenna unit to the horizontal omnidirectional antenna unit to be short-circuited to the metal floor, the electrical length of the vertical omnidirectional antenna unit is increased, meanwhile, a plurality of rectangular grooves which are formed in the metal floor in a radioactive mode are etched, radial surface current can be blocked, and the coupling current is reduced. Omnidirectivity of the horizontal antenna is guaranteed, the profile height of the antenna is reduced, and the radiation arms on the two surfaces of the two vertical dielectric substrates improve isolation between antenna ports.

Description

Technical Field

[0001] This invention belongs to the field of antenna technology and relates to a low-profile dual-polarized omnidirectional full-duplex antenna that can be applied to modern wireless communication systems. Background Technology

[0002] A dual-polarized omnidirectional antenna is an antenna capable of simultaneously supporting two orthogonal polarization methods (such as vertical / horizontal polarization or ±45° oblique polarization) and providing uniform signal coverage within a 360-degree horizontal plane, ensuring no blind spots within the service area. It is widely used in modern wireless communication systems. A low-profile antenna refers to an antenna whose physical height is much smaller than the operating wavelength (typically less than λ / 10), featuring a compact structure and ease of integration. With the rapid development of modern wireless communication systems (such as 5G / 6G, IoT, and indoor distributed systems), higher demands are placed on the performance of terminal antennas. Compared to half-duplex technology, full-duplex technology can transmit and receive simultaneously in the same frequency band, theoretically doubling spectral efficiency, and is one of the key technologies for future communication. The core challenge in realizing a full-duplex system lies in achieving high isolation between the transmitting and receiving antenna ports and a low antenna profile to suppress interference from strong transmitted signals on weak received signals.

[0003] In June 2019, Libin Sun, Yue Li, and others published a paper entitled "Compact Co-Horizontally Polarized Full-Duplex Antenna With Omnidirectional Patterns" in IEEE ANTENNAS AND WIRELESSPROPAGATION LETTERS. They proposed an in-phase loop antenna consisting of four dipoles and four integrated baluns. The close coupling of the four dipoles can achieve horizontally polarized omnidirectional radiation characteristics, which is beneficial for the miniaturization of the antenna.

[0004] To improve antenna isolation, especially for dual-polarized omnidirectional antennas, traditional antennas often require large three-dimensional structures or high profiles, making it difficult to meet the low profile requirements of modern mobile devices. For example, patent application CN116454634A, entitled "A Full-Duplex Antenna Based on Slot-Coupled Differential Feeding," includes two pairs of butterfly dipole antennas, a first dielectric substrate, four sets of vertically placed signal transmission lines, a metal ground plane, a second dielectric substrate, two U-shaped feed networks, and a third dielectric substrate. The two pairs of butterfly dipole antennas are placed perpendicularly to each other on the upper and lower surfaces of the first dielectric substrate; four identical T-shaped slots are etched into the metal ground plane; and the differential signals at the T-shaped slots are transmitted to the feed positions of the dipole antennas using the four sets of vertically placed transmission lines. This invention is based on the principle of slot-coupled differential feeding. It improves the isolation between the transmit and receive antenna ports by using two U-shaped feeding networks placed on different dielectric layers and perpendicular to each other. The isolation exceeds 41dB. However, since the antenna only uses slot-coupled differential feeding, the vertically polarized antenna element generates coupling current to the horizontal antenna element, resulting in a high antenna profile height of 0.26λ. Summary of the Invention

[0005] The purpose of this invention is to overcome the defects of the prior art and propose a low-profile dual-polarized omnidirectional full-duplex antenna, which aims to reduce the antenna profile height while achieving high isolation between the transmit and receive antenna ports.

[0006] To achieve the above objectives, the technical solution adopted by the present invention includes a vertical omnidirectional antenna unit 1, a horizontal omnidirectional antenna unit 2 fixed on its top, and a second horizontal dielectric substrate 3 with a metal ground plane 4 printed on its bottom surface; the vertical omnidirectional antenna unit 1 includes a first vertical dielectric substrate 11 and a second vertical dielectric substrate 12 with intersecting plate surfaces; a first radiating arm 111 and a second radiating arm 121 connected by metallized vias are respectively printed on the two plate surfaces of the first vertical dielectric substrate 11 and the second vertical dielectric substrate 12; multiple rectangular slots arranged radially are etched on the metal ground plane 4; the horizontal omnidirectional antenna unit 2 is connected to the metal ground plane 4 by four metal pillars 5.

[0007] As an optimization, the vertical omnidirectional antenna unit 1 includes a first vertical dielectric substrate 11 that intersects the second vertical dielectric substrate 12 perpendicularly; the first radiating arm 111 printed on the first vertical dielectric substrate 11 includes a T-shaped metal patch and two rectangular cutout patches connected to the two ends of its lateral arm; the second radiating arm 121 printed on the second vertical dielectric substrate 12 includes two rectangular cutout patches that are mirror-symmetrical about the longitudinal central axis of the second vertical dielectric substrate 12.

[0008] As an optimization, the T-shaped metal patch has a rectangular groove at the center of its top, and the central axis of the T-shaped metal patch coincides with the longitudinal central axis of the first vertical dielectric substrate 11.

[0009] As an optimization, the horizontal omnidirectional antenna unit 2 includes a first horizontal dielectric substrate 21 and a feed network 22 printed on its upper surface, and a horizontal radiating patch 23 on the lower surface connected to the feed network 22 through metallized vias.

[0010] As an optimization, the first vertical dielectric substrate 11 and the second vertical dielectric substrate 12 intersect the first horizontal dielectric substrate 21 and the second horizontal dielectric substrate 3 perpendicularly, and the perpendicular intersection line coincides with the center normal of the first horizontal dielectric substrate 21 and the second horizontal dielectric substrate 3.

[0011] As an optimization, the power supply network 22 includes four balun feed lines 221 arranged in a cross shape. Each balun feed line 221 includes a metal microstrip line with one end connected to the central power supply point and the other end connected to a rectangular metal patch.

[0012] As an optimization, the horizontal radiating patch 23 includes four centrally symmetrical dipole antenna elements 231; the lateral arm of each dipole antenna element 231 is deformed into an airfoil structure, and a rectangular slot is provided on the longitudinal arm, which is parallel to the metal microstrip line at the corresponding position in the feed network 22.

[0013] As an optimization, the metal pillar 5 is inserted at its top onto the first horizontal dielectric substrate 21 and does not contact the center of the transverse arm of the dipole antenna element 231 or the rectangular metal patch in each balun feed 221.

[0014] As an optimization, the metal floor 4, on which multiple rectangular grooves are etched in a radial arrangement, is rotationally symmetrical about the center of the second horizontal dielectric substrate 3.

[0015] As an optimization, it also includes two coaxial lines fixed to the second horizontal dielectric substrate 3, which are used to feed the vertical omnidirectional antenna element 1 and the horizontal omnidirectional antenna element 2, respectively.

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

[0017] 1. The four metal pillars connecting the horizontal omnidirectional antenna unit and the metal ground plane of the present invention can short-circuit the coupling current generated by the vertical omnidirectional antenna unit to the horizontal omnidirectional antenna unit to the metal ground plane, thereby increasing the electrical length of the vertical omnidirectional antenna unit and reducing the profile height of the antenna; at the same time, the multiple rectangular grooves etched radially on the metal ground plane can block the surface current, which on the one hand allows the vertical omnidirectional antenna unit to effectively radiate into the lower half-space, thereby forming a more ideal omnidirectional radiation pattern, and on the other hand increases the electrical length of the antenna and reduces the profile height by suppressing the coupling current.

[0018] 2. In this invention, radiating arms are printed on both surfaces of the two vertical dielectric substrates and connected by metallized vias, which makes the current distribution on the surface of the vertical dielectric substrates symmetrical, which helps to ensure the isolation between the transmitting and receiving antenna ports. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the overall structure of the present invention.

[0020] Figure 2 This is a schematic diagram of the first radiating arm structure of the present invention.

[0021] Figure 3 This is a schematic diagram of the second radiating arm structure of the present invention.

[0022] Figure 4 This is a schematic diagram of the power supply network structure of the present invention.

[0023] Figure 5 This is a schematic diagram of the horizontal radiation patch structure of the present invention.

[0024] Figure 6 This is a schematic diagram of the metal floor structure of the present invention.

[0025] Figure 7 This is a graph showing the relationship between the S-parameters of the present invention and frequency.

[0026] Figure 8 This is a graph showing the relationship between the gain and frequency of the present invention.

[0027] Figure 9 The radiation patterns of the vertical omnidirectional antenna element of the present invention at F=2.4GHz, 2.5GHz, and 2.6GHz when it is excited at θ=90° and Φ=0°.

[0028] Figure 10 The radiation patterns of the horizontal omnidirectional antenna element at F=2.4GHz, 2.5GHz, and 2.6GHz are shown for the plane radiation patterns at θ=90° and Φ=0° when the antenna element is excited. Detailed Implementation

[0029] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0030] Reference Figure 1 The present invention includes a vertical omnidirectional antenna unit 1, a horizontal omnidirectional antenna unit 2 fixed on its top, and a second horizontal dielectric substrate 3 with a metal ground plane 4 printed on its bottom surface. The horizontal omnidirectional antenna unit 2 and the metal ground plane 4 are connected by four metal pillars 5.

[0031] The vertical omnidirectional antenna unit 1 includes a first vertical dielectric substrate 11 and a second vertical dielectric substrate 12 with intersecting plates. Both plates are 1 mm thick and made of FR4-epoxy material with a relative permittivity of 4.4 and a loss tangent of 0.02. First radiating arms 111 and second radiating arms 121, connected by metallized vias, are printed on the two plates of the first and second vertical dielectric substrates 11 and 12, respectively. The radiating arms on both sides of the plates are connected by metallized vias, resulting in a symmetrical current distribution on both sides of the vertical dielectric substrate.

[0032] Reference Figure 2 The first radiating arm 111 includes a T-shaped metal patch and two rectangular hollow patches connected to the two ends of its transverse arm. The T-shaped metal patch is a reference to the T-shaped open-ring resonator in the prior art and can be regarded as an LC resonator. The longitudinal microstrip line of the T-shaped metal patch is equivalent to an inductor. The gap between the open-side stub and the metal ground plane 4 is regarded as a resonant capacitor, radiating a vertically polarized omnidirectional wave.

[0033] Reference Figure 3 The second radiating arm 121 includes two rectangular cutout patches that are mirror-symmetrical about the longitudinal central axis of the second vertical dielectric substrate 12. The rectangular cutout patches printed on the first radiating arm 111 and the second radiating arm 121 have the same shape. The symmetrical structure formed by them allows for more uniform coverage of vertically polarized radiation waves. The cutout design adjusts impedance matching and reduces excessive shielding of electromagnetic radiation by the structure.

[0034] The vertical omnidirectional antenna element 1 is excited by an external 50Ω coaxial line. The inner conductor of the coaxial line is connected to the central axis of the first radiating arm 111, and the outer conductor is connected to the metal ground plane 3.

[0035] The horizontal omnidirectional antenna element 2 includes a first horizontal dielectric substrate 21 and a feed network 22 printed on its upper surface, as well as a horizontal radiating patch 23 on its lower surface connected to the feed network 22 via a metallized via, which serves as the center feed point of the horizontal omnidirectional antenna element 2. The first horizontal dielectric substrate 21 has a circular cross-section, a thickness of 1 mm, and is made of FR4_epoxy material with a relative permittivity of 4.4 and a loss tangent of 0.02.

[0036] Reference Figure 4The power supply network 22 includes four balun feeders 221 arranged in a cross shape. Each balun feeder 221 includes a metal microstrip line with one end connected to the central power supply point and the other end connected to a rectangular metal patch.

[0037] Reference Figure 5 The horizontal radiating patch 23 includes four centrally symmetrical dipole antenna elements 231; the lateral arm of each dipole antenna element 231 is deformed into an airfoil structure, which widens the operating bandwidth of the horizontal omnidirectional antenna element 2; a rectangular slot is provided on the longitudinal arm, and the longitudinal arm is parallel to the metal microstrip line at the corresponding position in the feed network 22.

[0038] The horizontal omnidirectional antenna element 2 is excited by an external 50Ω coaxial line through a center feed point. The inner conductor of the coaxial line is connected to the feed network 22, and the outer conductor is connected to the horizontal radiating patch 23. After the radio frequency signal is transmitted to the cross-shaped point through the coaxial line, it will excite a horizontally conducted current on the microstrip branch in the horizontal direction of the feed network 22. The horizontal current will form a horizontally distributed time-varying current on the surface of the horizontal radiating patch 23, which will excite electromagnetic waves perpendicular to the current direction, thus achieving horizontal polarization.

[0039] Reference Figure 6 The metal ground plate 4 has multiple rectangular slots etched radially. When the top horizontal antenna is working, its radiated near field will strongly act on the metal ground plate below, inducing a reverse current on its surface. The rectangular slots etched on the metal ground plate 4 can block the surface current, allowing it to effectively radiate into the lower half-space, thus forming a more ideal omnidirectional radiation pattern. At the same time, by suppressing the coupling current, the electrical length of the antenna is increased and the profile height is reduced.

[0040] When the horizontal omnidirectional antenna element 2 is working, a significant capacitance is formed between it and the metal ground plane 4, which serves as the capacitive load for the vertical omnidirectional antenna element 1. At the same time, the vertical omnidirectional antenna element 1 generates a strong coupling current to the horizontal omnidirectional antenna element 2. The metal pillar 5 short-circuits the coupling current generated by the vertical omnidirectional antenna element 1 to the horizontal omnidirectional antenna element 2 to the metal ground plane, increasing the electrical length of the vertical omnidirectional antenna element and reducing the profile height of the antenna. The metal pillar 5 has its top inserted into the first horizontal dielectric substrate 21 and its bottom connected to the metal ground plane 4. Two circles with different radii are etched at the center of the horizontal arm of the dipole antenna element 231 and at the corresponding insertion points of the rectangular metal patches in each balun feed line 221, respectively, so as not to directly contact the feed network 22 or the horizontal radiating patch 23.

[0041] In this invention, the vertical omnidirectional antenna unit 1 and the horizontal omnidirectional antenna unit 2 radiate vertically polarized omnidirectional waves and horizontally polarized omnidirectional waves respectively in the same operating frequency band, and are used as receiving or transmitting antennas. The two polarization methods realize the function of full-duplex antennas transmitting and receiving at the same frequency band.

[0042] The technical effects of the present invention will be further illustrated by the following simulation experiments:

[0043] 1. Experimental conditions and contents:

[0044] This invention uses ANSYS Electronics Desktop software, with a frequency sweep range of 2.0 GHz to 3.0 GHz, a sweep interval of 0.001 GHz, a center frequency of 2.5 GHz, and a maximum number of iterations of 20, to simulate the electrical characteristics of this invention, wherein:

[0045] Simulation 1, for the impedance matching coefficient |S of the present invention 11 |、|S 22 |Isolation between horizontal and vertical omnidirectional antenna elements|S 21 Simulations were performed to demonstrate the relationship between frequency and frequency, and the results are as follows: Figure 7 As shown.

[0046] Simulation 2 simulates the relationship between the gain of the present invention and frequency, and the results are as follows. Figure 8 As shown.

[0047] Simulation 3 simulates the radiation patterns of the vertical omnidirectional antenna element of this invention at F=2.4GHz, 2.5GHz, and 2.6GHz when it is excited at θ=90° and Φ=0°. The results are as follows. Figure 9 As shown.

[0048] Simulation 4 simulates the radiation patterns of the horizontal omnidirectional antenna element of this invention at F=2.4GHz, 2.5GHz, and 2.6GHz when it is excited at θ=90° and Φ=0°. The results are as follows. Figure 10 As shown.

[0049] 2. Analysis of experimental results:

[0050] Reference Figure 7 The antenna impedance matching coefficient |S| is within the 2.4-2.76 GHz frequency range. 11 |≤-10dB, impedance matching coefficient in the 2.15GHz-3.0GHz frequency range|S 22 If |≤-10dB, the antenna bandwidth is 2.4-2.76GHz (i.e., 18.2%), and the isolation level is greater than 40.0dB, with a maximum value of 68.0dB.

[0051] Reference Figure 8 The gain of this invention when excited at different excitation ports was simulated, and the results are as follows. Figure 8As shown, the gains of the two antenna ports are approximately 0.5 dBi and 1.0 dBi, respectively. Compared to the excitation port of the horizontal omnidirectional antenna element, the gain of the excitation port of the vertical omnidirectional antenna element is slightly lower. This is because the horizontal omnidirectional antenna element is mounted on top of the vertical omnidirectional antenna element in the antenna structure, resulting in a slight loss of gain for the vertical omnidirectional antenna element.

[0052] Reference Figure 9 (a) to (c) show the radiation patterns of the antenna in the θ=90° plane when the vertically polarized antenna element is excited at frequencies of 2.4 GHz, 2.5 GHz, and 2.6 GHz, respectively; (d) to (f) show the radiation patterns of the antenna in the Φ=0° plane when the vertically polarized antenna element is excited at frequencies of 2.4 GHz, 2.5 GHz, and 2.6 GHz, respectively; the vertically polarized antenna element radiates omnidirectional radiation waves in the vertical direction.

[0053] Reference Figure 10 (a) to (c) show the radiation patterns of the horizontally polarized antenna element when it is excited at frequencies of 2.4 GHz, 2.5 GHz, and 2.6 GHz, respectively, in the θ=90° plane; (d) to (f) show the radiation patterns of the horizontally polarized antenna element when it is excited at frequencies of 2.4 GHz, 2.5 GHz, and 2.6 GHz, respectively, in the Φ=0° plane; the horizontally polarized antenna element radiates omnidirectional radiation waves in the horizontal direction.

[0054] In summary, the antenna operates within a bandwidth of 2.4-2.76 GHz (18.2%), with isolation levels exceeding 40.0 dB, reaching a maximum of 68.0 dB. The profile height is 0.1λ. The gains at the two antenna ports are approximately 0.5 dBi and 1.0 dBi, respectively. Throughout the bandwidth, the cross-polarization levels of both the transmitting and receiving antennas are below -20.0 dB. This invention relates to the field of antenna technology, specifically to a low-profile, dual-polarized, omnidirectional, full-duplex antenna that can effectively improve the spectral efficiency of wireless communication systems.

Claims

1. A low-profile dual-polarized omnidirectional full-duplex antenna, comprising a vertical omnidirectional antenna element (1), a horizontal omnidirectional antenna element (2) fixed on its top, and a second horizontal dielectric substrate (3) with a metal ground plane (4) printed on its bottom surface; the vertical omnidirectional antenna element (1) comprises a first vertical dielectric substrate (11) and a second vertical dielectric substrate (12) with intersecting plate surfaces; characterized in that, The first vertical dielectric substrate (11) and the second vertical dielectric substrate (12) are respectively printed with a first radiating arm (111) and a second radiating arm (121) connected by metallized vias; the metal floor (4) is etched with multiple rectangular slots arranged radially; the horizontal omnidirectional antenna unit (2) is connected to the metal floor (4) by four metal pillars (5).

2. The full-duplex antenna according to claim 1, characterized in that, The vertical omnidirectional antenna unit (1) includes a first vertical dielectric substrate (11) that intersects the second vertical dielectric substrate (12) perpendicularly; the first radiating arm (111) printed on the first vertical dielectric substrate (11) includes a T-shaped metal patch and two rectangular cutout patches connected to the two ends of its lateral arm; the second radiating arm (121) printed on the second vertical dielectric substrate (12) includes two rectangular cutout patches that are mirror-symmetrical about the longitudinal central axis of the second vertical dielectric substrate (12).

3. The full-duplex antenna according to claim 2, characterized in that, The T-shaped metal patch has a rectangular groove at the center of its top, and the central axis of the T-shaped metal patch coincides with the longitudinal central axis of the first vertical dielectric substrate (11).

4. The full-duplex antenna according to claim 2, characterized in that, The horizontal omnidirectional antenna unit (2) includes a first horizontal dielectric substrate (21) and a feed network (22) printed on its upper surface, and a horizontal radiating patch (23) on the lower surface connected to the feed network (22) through metallized vias.

5. The full-duplex antenna according to claim 4, characterized in that, The first vertical dielectric substrate (11) and the second vertical dielectric substrate (12) intersect the first horizontal dielectric substrate (21) and the second horizontal dielectric substrate (3) perpendicularly, and the perpendicular intersection line coincides with the center normal of the first horizontal dielectric substrate (21) and the second horizontal dielectric substrate (3).

6. The full-duplex antenna according to claim 5, characterized in that, The power supply network (22) includes four balun feeders (221) arranged in a cross shape. Each balun feeder (221) includes a metal microstrip line with one end connected to the central power supply point and the other end connected to a rectangular metal patch.

7. The full-duplex antenna according to claim 6, characterized in that, The horizontal radiating patch (23) includes four centrally symmetrical dipole antenna elements (231); the transverse arm of each dipole antenna element (231) is deformed into an airfoil structure, and a rectangular slot is provided on the longitudinal arm, which is parallel to the metal microstrip line at the corresponding position in the feed network (22).

8. The full-duplex antenna according to claim 7, characterized in that, The metal pillar (5) is inserted at its top onto the first horizontal dielectric substrate (21) and does not contact the center of the transverse arm of the dipole antenna element (231) or the rectangular metal patch in each balun feed (221).

9. The full-duplex antenna according to claim 1, characterized in that, The metal floor (4) has multiple rectangular grooves etched thereon arranged radially about the center of the second horizontal dielectric substrate (3) and is rotationally symmetrical about it.

10. The full-duplex antenna according to claim 1, characterized in that, It also includes two coaxial lines fixed to the second horizontal dielectric substrate (3), which are used to feed the vertical omnidirectional antenna unit (1) and the horizontal omnidirectional antenna unit (2), respectively.

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