Circularly polarized patch array antenna with low axial ratio

Abstract

The invention discloses a low-axial-ratio circularly-polarized patch array antenna, and relates to the technical field of electronics and wireless communication, the array antenna adopts 2 * 2 sub-arrays which are rotationally and symmetrically arranged, circularly-polarized units in the sub-arrays are trimming laminated patch antennas which are obliquely arranged at 45 degrees, and four units in the sub-arrays adopt sequential rotation phase feeding; the four unit ports in the subarray adopt sequential rotation phase feed, and the phase distribution is gradually increased anticlockwise or clockwise at an interval of 90 degrees. Therefore, the radiation electric field vector of the sub-array in the normal direction rotates anticlockwise or clockwise in the propagation direction, namely, the sub-array realizes left-hand circular polarization or right-hand circular polarization radiation. By the adoption of the array arrangement method, the low axial ratio, namely the high polarization purity, of the circularly polarized array antenna can be achieved within the wide angle range of the azimuth plane and the diagonal plane.

Description

Technical Field

[0001] The present invention relates to the technical field of wireless communications, and in particular to a low-axial-ratio circularly polarized patch array antenna. Background Art

[0002] Circularly polarized antennas offer improved performance in the following areas: 1) They are better able to combat multipath interference. 2) They can mitigate the "Faraday rotation" effect. 3) They can minimize polarization mismatch losses between the transmitting and receiving antennas. These advantages make circularly polarized antennas promising for improving the stability and performance of communication systems. Patch array antennas are widely adopted due to their low profile, simple structure, and ease of single-board integration. Circularly polarized array antennas offer flexible beam steering capabilities and high gain, making them widely used in satellite communications. The axial ratio of a circularly polarized antenna characterizes the polarization purity of its radiation. Reducing the antenna axial ratio helps reduce polarization mismatch losses and improve the gain of the array antenna.

[0003] In satellite communications applications, the beam of an active array antenna typically needs to be deflected over a wide angle range of ±60°. Using a conventional array arrangement, a circularly polarized antenna array will experience a deterioration in the circular polarization axial ratio at the main lobe beam's direction when deflected at large angles.

[0004] Some published work has demonstrated that array antennas with dual-linear polarization, dual-circular polarization, and single-linear polarization elements can achieve a lower circular polarization axial ratio near the normal direction with the aid of reverse feeding technology. However, these array antenna designs all experience a sharp deterioration in the circular polarization axial ratio when scanning at large angles in at least one scanning plane (the axial ratio reaches approximately 10 dB at the calibration frequency, while it is typically required to be less than 3 dB). This deterioration in polarization purity further reduces the gain of the main polarization beam and reduces the signal coverage range.

[0005] The only solution currently available is to recalibrate the amplitude and phase of the vertical and horizontal polarization components during wide-angle scanning to reduce the axial ratio. This involves recalibrating the array antenna at a poorly performing beam pointing position. This increases the array antenna calibration workload and system complexity and is limited to hardware with dual-polarized antennas. Therefore, the development of circularly polarized patch array antennas with low axial ratios during wide-angle scanning remains to be explored. Summary of the Invention

[0006] In response to the above problems, the purpose of the present invention is to provide a low-axial-ratio circularly polarized patch array antenna, which is based on a 45° tilted circularly polarized patch antenna unit and a rotating feeding technology, and has a low-axial-ratio within a wide angle range. At the same time, the array antenna has the advantages of simple structure and low cost.

[0007] To achieve the above objectives, the present invention employs a technical solution: a low-axial-ratio circularly polarized patch array antenna, characterized in that the array antenna comprises a rotationally symmetrical 2×2 subarray, each of which includes four circularly polarized elements; each circularly polarized element is a circularly polarized patch antenna element tilted at 45°. The 2×2 subarray can be expanded into an array antenna of any size in a two-dimensional plane.

[0008] As a preferred structure of the present invention, the four circularly polarized patch antenna units are arranged in a rotationally symmetrical manner around the center of the subarray.

[0009] As a preferred structure of the present invention, the four circularly polarized patch antenna units adopt sequential rotating phase feeding, and the phase distribution increases in a clockwise or counterclockwise direction at intervals of 90 degrees, thereby realizing left-handed or right-handed circularly polarized radiation.

[0010] As a preferred structure of the present invention, the patch antenna in the circularly polarized patch antenna unit is a cut-edge laminated patch antenna, wherein the radiating patch arranged on the top layer and the driving patch arranged on the third layer are cut-edge structures, and the feeding probe in the cut-edge laminated patch antenna is not connected to the radiating patch but is connected to the driving patch.

[0011] As a preferred structure of the present invention, the four circularly polarized patch antenna units are installed at rotation angles of 45°, 135°, 225° and 315°, and the feeding structures of the four patch antennas are also rotationally symmetric around the subarray center.

[0012] As a preferred structure of the present invention, the unit spacing of the four circularly polarized patch antenna units is 0.44λ, where λ is the free space wavelength at the center operating frequency.

[0013] Compared with the prior art, the technical solution adopted by the present invention has the following beneficial effects: (1) The present invention adopts a 2×2 sub-array with a rotationally symmetrical arrangement, which can be expanded into an array antenna of any scale on a two-dimensional plane.

[0014] (2) In the rotationally symmetrically arranged 2×2 subarray of the present invention, the four unit ports in the subarray are fed with sequentially rotating phases, with the phase distribution increasing in a counterclockwise or clockwise direction at intervals of 90°. This causes the radiated electric field vector of the subarray in the normal direction to rotate counterclockwise or clockwise in the propagation direction, that is, the subarray realizes left-hand circular polarization or right-hand circular polarization radiation.

[0015] (3) The array arrangement method of the present invention can enable the circularly polarized array antenna to achieve a low axial ratio within a wide angle range in the azimuth plane and the diagonal plane, that is, a higher polarization purity. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 13 is a schematic diagram of a subarray of the low axial ratio circularly polarized patch array antenna provided in this embodiment.

[0017] Figure 2 Schematic diagram of the top radiating patch structure of the trimmed-edge laminated patch antenna provided in this embodiment; Figure 3 1 is a schematic diagram of the structure of the driving patch of the third layer in the cut-edge laminated patch antenna provided in this embodiment; Figure 4 Schematic diagram of the stacked structure of a multilayer printed circuit board provided in this embodiment.

[0018] Figure 5 Schematic diagram of the antenna surface structure of an 8×8 array example of a multilayer printed circuit board provided in this embodiment.

[0019] Figure 6 It is a schematic diagram of the simulated beam deflection radiation pattern and circular polarization axial ratio results of the low axial ratio circularly polarized patch array antenna provided in this embodiment on the horizontal plane.

[0020] Figure 7 It is a schematic diagram of the simulated beam deflection radiation pattern and circular polarization axial ratio results of the low axial ratio circularly polarized patch array antenna provided in this embodiment on the diagonal plane.

[0021] Figure 8 This is a schematic diagram of the measured beam deflection radiation pattern and circular polarization axial ratio results of the low axial ratio circularly polarized patch array antenna provided in this embodiment on the horizontal plane.

[0022] Figure 9 This is a schematic diagram of the measured beam deflection radiation pattern and circular polarization axial ratio results of the low axial ratio circularly polarized patch array antenna provided in this embodiment on the diagonal plane. DETAILED DESCRIPTION

[0023] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Any modifications made based on the technical solutions in accordance with the technical ideas proposed by the present invention shall fall within the scope of protection of the present invention.

[0024] Take the design of left-hand circularly polarized array antenna as an example, refer to the attached Figure 1 -Attached Figure 2The low-axial-ratio circularly polarized patch array antenna provided by the present invention utilizes a rotationally symmetrical 2×2 subarray 1. The circularly polarized elements in the subarray are 45° tilted, cut-edge laminated patch antennas 2. The four elements in the subarray utilize sequential rotational phase feeding 3. The element antennas are laminated patch antennas, with the top-layer radiating patch having a cut-edge 4 and the third-layer driver patch also having a cut-edge 6. The feed probe 5 is connected to the driver patch instead of the radiating patch.

[0025] The excitation phases at the antenna element input ports are set to 0°, 90°, 180°, and 270° counterclockwise within the subarray. This causes the radiated electric field vector in the normal direction of the subarray to rotate counterclockwise relative to the propagation direction, resulting in left-hand circular polarization. The element spacing is 0.44λ, where λ is the free-space wavelength at the center operating frequency.

[0026] In an 8×8 array, 16 of the above circularly polarized 2×2 subarrays are arranged together. Based on the rotationally symmetrical arrangement of the subarrays, appropriate phase excitation is applied to each unit to simulate the beam deflection of the array. The simulated array beam scans to -60° in the horizontal plane. Figure 6 In the horizontal plane, the circularly polarized array can achieve beam scanning within a range of ±60° with a scanning loss of less than 3.8 dB. The left-hand circular polarization axial ratio in the main beam direction of each beam is less than 3 dB.

[0027] The simulation results on the diagonal surface are as follows Figure 7 As shown in the figure, under ideal conditions, the circularly polarized array can achieve beam scanning within a range of ±60°, with a scanning loss of less than 4.1 dB. The left-hand circular polarization axis ratio in the main beam direction of each beam is less than 3 dB.

[0028] In order to verify the authenticity and reliability of the low-axial-ratio circularly polarized patch array antenna provided by the present invention, a circularly polarized array antenna operating in the 25GHz to 27GHz frequency band was designed and manufactured in accordance with this embodiment, and the array size is 8×8. The active array was finally designed on a 10-layer PCB board. The PCB is laminated by DS-3 dielectric boards and RO4450F adhesive boards. The antenna is located on the 1st to 5th layers of the 10-layer board, and the fifth layer serves as the floor of the antenna. The active feeding network is designed on the 6th to 10th layers, and the beamforming chip is surface-mounted on the bottom layer (the 10th layer). The active feeding network is used to apply a feeding signal excitation to each antenna unit that meets the requirements of the rotating feeding phase in the present invention. The laminated structure of the circularly polarized array is shown in FIG. Figure 4 As shown, the antenna surface structure is as follows Figure 5 After the array antenna is calibrated, the beam scanning pattern results and circular polarization axis ratio results on the horizontal and diagonal planes are measured. Figure 8 and Figure 9The array's main beam can scan within a ±60° range in the horizontal plane. Its axial ratio results are consistently better than 3.07dB, demonstrating significant performance advantages over similar designs.

[0029] The above theoretical and measured results prove the authenticity and reliability of this implementation case.

[0030] Although the present invention has been disclosed above with reference to preferred embodiments, the embodiments and accompanying drawings are not intended to limit the present invention. Any person skilled in the art will readily be able to make various changes or modifications without departing from the spirit and scope of the present invention, and such changes and modifications are within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be determined by the scope of protection of the claims of this application.

Claims

1. A low-axial-ratio circularly polarized patch array antenna, characterized by: The array antenna includes a 2×2 sub-array that is arranged rotationally symmetrically. The 2×2 sub-array includes four circularly polarized units. The circularly polarized unit is a circularly polarized patch antenna unit tilted at 45 degrees.

2. The low axial ratio circularly polarized patch array antenna according to claim 1, wherein: The four circularly polarized patch antenna units are arranged in a rotationally symmetrical manner around the center of the subarray.

3. The low axial ratio circularly polarized patch array antenna according to claim 1, wherein: The four circularly polarized patch antenna units are fed by sequentially rotating phases, and the phase distribution increases in a clockwise or counterclockwise direction at intervals of 90 degrees.

4. A low axial ratio circularly polarized patch array antenna according to any one of claims 1 to 3, characterized in that: The patch antenna in the circularly polarized patch antenna unit is a cut-edge stacked patch antenna, wherein the radiating patch arranged on the top layer and the driving patch arranged on the third layer are cut-edge structures, and the feeding probe in the cut-edge stacked patch antenna is not connected to the radiating patch but is connected to the driving patch.

5. The low axial ratio circularly polarized patch array antenna according to claim 4, wherein: The four circularly polarized patch antenna units are installed at rotation angles of 45°, 135°, 225° and 315°, and the feeding structures of the four patch antennas are also rotationally symmetrical around the subarray center.

6. The low axial ratio circularly polarized patch array antenna according to claim 4, wherein: The unit spacing of the four circularly polarized patch antenna units is 0.44λ, where λ is the free space wavelength at the center operating frequency.

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