A circularly polarized array antenna with sequential rotation feeding

Abstract

The present application provides a circularly polarized array antenna with sequential rotation feeding, which is characterized by comprising a radiation top plate, a feeding network and a bottom plate. The radiation top plate is connected to the feeding network at intervals through a first connector. The radiation top plate includes a plurality of radiation units, which are respectively coupled to the feeding network. The bottom plate is disposed on the side of the feeding network away from the radiation top plate and serves as an antenna reflector. This circularly polarized array antenna has the characteristics of small volume, high gain and low profile, can be used in application scenarios of limited spaces such as under-construction tunnels, and can operate in the LTE (1.7 - 2.7 GHz) frequency band.

Description

Technical Field

[0001] The present application relates to the technical field of antennas, and particularly to a circularly polarized array antenna with a sequential rotation feeding network. Background Art

[0002] With the rapid development of satellite communication, navigation and positioning, and radio frequency identification systems, circularly polarized antennas have attracted wide attention. Since circularly polarized antennas can receive incident waves from any direction, and can significantly reduce the multipath effect, reduce the delay spread, effectively reduce the bit error rate, and improve the communication reliability.

[0003] In recent years, scholars at home and abroad have proposed a number of broadband, high-gain, low-profile circularly polarized antennas with sequential rotation feeding. The literature [Hu W, Wen G, Inserra D, et al. A Circularly Polarized Antenna Array with Gain Enhancement for Long-Range UHF RFID Systems[J]. Electronics, 2019, 8(4)] proposed a 2×2 sequentially rotated microstrip patch circularly polarized array antenna. By using a series power division form, the amplitudes of the four ports are made equal and the phases are sequentially generated by 90°. Its 3dB axial ratio bandwidth is 18.2% (828 - 994 MHz), and the corresponding peak gain is 12.5 dBi. However, the size of its antenna reflector is large and it is not easy to install and produce. The literature [Ibrahim K M, Hassan W M, Abdallah E A, et al. Wideband sequential feeding network for Ku‐band dual circularly polarized 4 × 4 antenna array[J]. International Journal of RF and Microwave Computer-Aided Engineering, 2020(11)] proposed a dual circularly polarized 4×4 array antenna. The designed feeding network is composed of 2 sequentially rotated feeding networks. By adding appropriate short sections in the feeding network to compensate for the coupling effect between the feeding networks. The circular polarization performance of the antenna is good and it has a small size. However, its feeding network is complex and there are many coupling variables, which is not convenient for design and production. The literature [Verma A, Arrawatia M, Kumar G. Broadband Series-fed Circularly Polarized Microstrip Antenna Array[C] / / 2020 IEEE International Symposium on Antennas and Propagation and North American Radio Science Meeting. IEEE, 2020] is composed of four sequentially rotated microstrip circularly polarized microstrip antennas connected to a circularly polarized patch antenna. The central patch is fed by two orthogonal L-probes.The literature [Ong C S, Karim M F, Ong L C, et al. A 2×4 circularly polarized antenna Array for WLAN applications[C] / / Asia-Pacific Microwave Conference 2011. IEEE, 2012] demonstrates a compact 2.45 GHz circularly polarized antenna and a 2×4 antenna array. The circular polarization characteristic is achieved by using unbalanced slots on the circular patch, and a 2×4 antenna array is designed using a sequential rotation feeding scheme. The 3 dB axial ratio bandwidth is greater than 45 MHz, and the gain is 12.5 dBi. In addition to considering the effectiveness of communication between the circularly polarized array antenna and mobile devices in a limited space, the robustness of the circularly polarized array antenna also needs to be considered. In addition, the impedance bandwidth and axial ratio bandwidth of the circularly polarized array antenna may have some frequency offsets in other limited spaces, and a certain redundancy is also required for the impedance bandwidth and axial ratio bandwidth of the circularly polarized array antenna operating in the LTE band. Existing circularly polarized array antennas still have some deficiencies in this regard.

[0004] Therefore, it is necessary to improve the existing circularly polarized array antennas. Summary of the Invention

[0005] To overcome the above defects, the purpose of this application is to propose a miniaturized circularly polarized array antenna with a novel sequential rotation feeding network, which has the characteristics of circular polarization, low profile, simple structure, and easy processing and production.

[0006] To achieve the above purpose, the following technical solutions are adopted in this application:

[0007] A circularly polarized array antenna with sequential rotation feeding, characterized by comprising:

[0008] A radiation top plate, a feeding network, and a bottom plate,

[0009] The radiation top plate is connected to the feeding network at intervals through a first connector,

[0010] The radiation top plate includes a plurality of radiation ends, which are respectively coupled to the feeding network, and each radiation end includes 2 radiation units,

[0011] The bottom plate is arranged on the side of the feeding network away from the radiation top plate and serves as an antenna reflector.

[0012] Preferably, the radiation top plate includes 3 or 4 radiation ends, which are respectively coupled to the feeding network.

[0013] Preferably, each radiation end includes two symmetric radiation units, the centers of the radiation ends are on the same circle, and the radiation ends are sequentially rotated (such as clockwise / counterclockwise rotation, rotating 120° when there are 3 radiation ends, rotating 90° when there are 4 radiation ends, and rotating in a similar manner when there are other numbers) by the same angle and evenly distributed along the circle.

[0014] Preferably, the centers of the radiation units are on the same circle and are evenly distributed along the circle.

[0015] Preferably, the circularly polarized array antenna with sequential rotation feeding is characterized by comprising:

[0016] The radiation unit includes: a circular radiation patch and a parasitic unit with an arc-shaped cut corner,

[0017] The parasitic units are evenly arranged around the circular radiation patch.

[0018] Preferably, the circularly polarized array antenna is further characterized by comprising: rectangular stubs,

[0019] The rectangular stubs are arranged on the circular radiation patch and symmetrically arranged to change the current path and broaden the antenna impedance bandwidth.

[0020] Preferably, the radiation top plate uses M3 copper posts to connect the radiation top plate and the feeding network.

[0021] Preferably, the rectangular stubs are integrally designed with the radiation patch. Preferably, the feeding network includes: 7 three-order Wilkinson power dividers, 4 45° Schiffman phase shifters, 2 90° Schiffman phase shifters and 1 180° Schiffman phase shifter.

[0022] Preferably, the radiation top plate includes 8 radiation units sequentially rotated by 45°, which are respectively connected to the circular radiation patch through microstrip lines of equal length added to the matching ports.

[0023] Preferably, the bottom plate is an aluminum plate, and the edge of the aluminum plate is configured with a bending part bent toward the radiation top plate side.

[0024] Preferably, the aluminum plate is configured with rectangular stubs. The rectangular stubs are located at a preset position to the left of the center of the aluminum plate. Advantageous Effects

[0025] Compared with the prior art, the circularly polarized array antenna of the embodiment of the present application has: a relatively wide impedance bandwidth, axial ratio bandwidth, and good circular polarization performance; and the antenna has the advantages of simple structure, high gain, low profile, miniaturization, etc., and is convenient for installation. The circularly polarized array antenna can be used in application scenarios in limited spaces such as under-construction tunnels. Description of the Drawings

[0026] Figure 1 It is the antenna simulation model diagram of the embodiment of the present application;

[0027] Figure 2 It is the schematic diagram of the antenna structure of the embodiment of the present application;

[0028] Figure 3 It is the schematic diagram of the antenna element layout of the embodiment of the present application;

[0029] Figure 4 It is the top view of the feed network of the embodiment of the present application;

[0030] Figure 5 It is the performance simulation diagram of the feed network of the embodiment of the present application;

[0031] Figure 6 It is the antenna impedance simulation diagram of the embodiment of the present application

[0032] Figure 7 It is the antenna return loss simulation diagram of the embodiment of the present application;

[0033] Figure 8 It is the antenna gain and axial ratio simulation diagram of the embodiment of the present application;

[0034] Figure 9 It is the radiation pattern of the antenna at the 2.2 GHz frequency point of the embodiment of the present application. Specific embodiments

[0035] The above solution will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are for illustrating the present invention and not for limiting the scope of the present invention. The implementation conditions adopted in the embodiments can be further adjusted according to the conditions of specific manufacturers, and the implementation conditions not specified are usually the conditions in conventional experiments.

[0036] The present application provides a circularly polarized array antenna, which includes: a radiation top plate, a feed network and a bottom plate,

[0037] The radiating top plate is connected to the feeding network at intervals through a first connector. The radiating top plate includes a plurality of radiating ends, and each radiating end contains two symmetric radiating elements. The radiating ends are coupled to the feeding network. The bottom plate is disposed on the side of the feeding network away from the radiating top plate and serves as an antenna reflector. The radiating ends are arranged at intervals, and their centers are all on a circle with a radius of R. The first / second connectors are both copper posts. The circularly polarized array antenna can effectively excite the circular polarization characteristic of the antenna through a power division and phase shift network composed of a third-order Wilkinson and Schiffman phase shifter; the bandwidth can be effectively expanded by adding a T-shaped matching stub in the feeding network; a rectangular stub structure symmetric about the left and right is loaded on the antenna radiating element to extend the current path and effectively expand the bandwidth; by adding four parasitic elements, the circular radiation patch is coupled to the parasitic elements to increase the radiation area, and the axial ratio bandwidth and gain flatness can be adjusted by adjusting the distance between the parasitic elements and the circular radiation patch; a flange NKF RF coaxial connector is used for feeding, which is convenient for installation and fixing and has good matching characteristics.

[0038] The circularly polarized array antenna has the characteristics of small size, high gain, and low profile. It can be used in limited space application scenarios such as under-construction tunnels, and it is a circularly polarized array antenna with a sequential rotation feeding network that can operate in the LTE (1.7 - 2.7 GHz) frequency band. Applying the circularly polarized antenna to limited spaces such as under-construction tunnels can effectively reduce communication coverage blind spots, improve data communication quality, and reduce the bit error rate. By erecting a circularly polarized array antenna in the construction tunnel environment, walk from the antenna erection point into the tunnel, conduct field strength and data download rate tests at certain intervals, and conduct actual communication effect tests by making phone calls and WeChat video calls, etc.

[0039] Next, in combination with the attached Figure 1 and Figure 2 to describe the circularly polarized array antenna (hereinafter referred to as the antenna) proposed in this application.

[0040] As Figure 1 shown is the schematic diagram of the antenna simulation model, Figure 2 and is the schematic diagram of the antenna structure.

[0041] The antenna structure is as Figure 2 shown. The antenna includes: a radiating top plate 10, a feeding network 20, and a bottom plate 30.

[0042] There is an air gap between the radiating top plate 10 and the feeding network 20.

[0043] The radiating top plate 10 includes eight radiating elements 11, which are respectively connected to the radiating top plate and the feeding network through connectors (such as M3 copper posts).

[0044] The bottom plate 30 includes: an aluminum plate, which is located at the bottom of the antenna and is used as an antenna reflector.

[0045] In the embodiment of the present application, the parameter configuration is as follows: L1 = 70.5 mm, L2 = 280 mm, L3 = 350 mm, H1 = 0.8 mm, H2 = 1 mm, H3 = 7.5 mm, H4 = 8 mm, R1 = 120 Ω, R2 = 221 Ω, R3 = 324 Ω. Preferably, the centers of the eight-element radiation units are on the same circle and are evenly distributed along the circle. In one embodiment, the bottom plate (by means of coating, gluing, laminating or screw fixing, etc.) is disposed on one side of the dielectric substrate of the feeding network. The feeding network 20 includes a feeding port 21 for connecting to a feeding end.

[0046] The working principle of the antenna is as follows: The antenna is fed by a flange NKF radio frequency coaxial connector, and the input impedance at the antenna end at 2.2 GHz is: 61 + j*1.66 Ω. And a 50-ohm microstrip line with a width of 2.72 mm is used to connect a feeding network with the characteristic of phase sequence rotation, so as to realize the circular polarization characteristic. The feeding network satisfies the phase differences of 0°, 45°, 90°, 180°, 225°, 270°, 315°, 360°, etc.

[0047] The radiation unit includes: a circular radiation patch, and using a circular shape can effectively improve the antenna gain.

[0048] Parasitic units and rectangular stubs are arranged on the four sides of the circular radiation patch. By adding the parasitic units, the axial ratio and gain balance of the antenna can be improved. Configuring two left and right rectangular stubs can change the current path and broaden the antenna impedance bandwidth. The radiation unit uses four M3 copper posts to connect the radiation top plate and the feeding network, and such a design is convenient for production and assembly and is more reliable and stable.

[0049] The layout of the radiation units on the radiation top plate is as Figure 3 shown, and is composed of eight sequentially rotating radiation units.

[0050] Each radiation unit 11 includes: a circular radiation patch 11a, two first rectangular stubs 11c that are symmetric left and right, and four parasitic units 11b with arc-shaped cut corners. In this embodiment, the dielectric substrate is an FR4 substrate with a relative dielectric constant of 4.4, a loss tangent of 0.02, a thickness of h1, and a length and width of L1. The radiation unit 11 is square or quadrilateral (see Figure 3 ).

[0051] The radiation top plate and the feeding network are connected at intervals by a plurality of (such as 32 M3*h3) copper posts, and the interval is an air gap.

[0052] The feeding network includes a dielectric substrate, with a feeding layer disposed on one side and a bottom metal plane disposed on the side opposite to the feeding layer. Its top view is as Figure 4As shown. The feeding network (feeding layer) includes: 7 third-order Wilkinson power dividers 23, 4 45° Schiffman phase shifters 24, 2 90° Schiffman phase shifters 25, and 1 180° Schiffman phase shifter 26. Through Figure 4 The placement configuration can make the right-handed circularly polarized waves with equal amplitude and a phase difference of 45° in turn at the Port2-Port9 ports, realizing circular polarization. The feeding network also includes a T-type matching structure 22. Feeding is carried out through a flange NKF radio frequency coaxial connector (not shown in the figure). Adding a second-order T-type matching stub in the feeding network can obtain good impedance matching characteristics. This method uses a power divider connected to a phase shifter to form a power dividing phase shifter. The two output ports of the 180° power dividing phase shifter are connected to 2 90° power dividing phase shifters, and the two output ports of the 90° power dividing phase shifter are connected to two 45° power dividing phase shifters. In order to meet the phase difference of 45° in turn (see Figure 4 ). In this embodiment, the F4-B substrate is selected for the dielectric substrate, with a relative dielectric constant of 2.65, a loss tangent of 0.002, a thickness of H2, and both the length and width of L2. There is an aluminum plate with a thickness of 1.5 mm and both the length and width of L2 at the bottom of the antenna. Its main function is to serve as the reflector of the antenna, and its size affects the gain. The radiation top plate includes 8 radiation units configured to rotate 45° in turn, and they are respectively connected to the matching ports by adding microstrip lines of equal length (connected to the preset connection points of the circular radiation patch 11a), so as to ensure that the signals on the excited antenna can still meet the right-handed circularly polarized waves with equal amplitude and a phase difference of 45° in turn.

[0053] In one embodiment, in order to further reduce the antenna size, the four sides of the aluminum plate are bent, and the bending height is H4. The bent antenna array further improves the antenna gain. A rectangular stub with a width of 10 mm and a height of H4 is dug out at a preset position (such as the 15 mm position) slightly to the left of the center of the bent aluminum plate, which can make the gain of the entire LTE band stable above 15 dBi.

[0054] Next, in combination with Figures 5 - 9 to describe the performance of the above antenna.

[0055] Figure 5 The figure shows the performance diagram of the feeding network. The reflection coefficient of the feeding port is less than -10 dB within 1.5 - 2.9 GHz. S21, S31, S41, S51, S61, S71, S81, and S91 are all lower than 9.7 dB within the 1.7 - 2.7 GHz band. Considering that the loss of the third-order power divider is 9 dB, the internal loss brought by the feeding network is about 0.7 dB. Within 1.7 - 2.7 GHz, the phase can be maintained within the accuracy range of 45° ± 8°.

[0056] Figure 6It is the simulation diagram of the antenna impedance. At the center frequency of 2.2 GHz, the input impedance at the antenna end is: 61 + j*1.66 Ω.

[0057] Figure 7 It is the simulation diagram of the antenna return loss of the present invention. It can be seen from the figure that the -10 dB impedance bandwidth of the simulation result is 1.31 GHz, covering the entire LTE band from 1.52 GHz to 2.83 GHz.

[0058] Figure 8 It shows the simulation diagrams of the gain and axial ratio of the array antenna. It can be seen from the figure that the gain of the antenna is almost above 15 dBi from 1.7 GHz to 2.7 GHz, and the highest gain can reach about 17.6 dBi. Its axial ratio is within 3 dB from 1.5 GHz to 3 GHz, meeting the requirements of circular polarization.

[0059] Figure 9 It gives the radiation pattern of the antenna at the frequency point of 2.2 GHz. In the narrow and straight tunnel environment, the public network coverage distance is greater than 1 kilometer, which can meet the normal data transmission of mobile devices.

[0060] The above embodiments are only used to illustrate the technical concept and features of the present invention, and the purpose is to enable those who are familiar with this technology to understand the content of the present invention and implement it accordingly. It cannot be used to limit the protection scope of the present invention. Any equivalent transformation or modification made in the spirit of the present invention should be covered within the protection scope of the present invention.

Claims

1. A circularly polarized array antenna with sequential rotation feeding, characterized in that Comprising: A radiation top plate, a feeding network and a bottom plate, The radiation top plate and the feeding network are connected at intervals through a first connecting member, The radiation top plate includes a plurality of radiation ends, which are respectively coupled to the feeding network. Each radiation end includes: 2 radiation units. The centers of the radiation ends are on the same circle, and the radiation ends are evenly distributed along the circle in a sequential rotation by a uniform angle, The bottom plate is disposed on the side of the feeding network away from the radiation top plate and serves as an antenna reflector, The radiation unit includes: a circular radiation patch and a parasitic unit with an arc-shaped cut angle. The parasitic units are evenly arranged around the outside of the circular radiation patch. It also includes: a first rectangular stub, The first rectangular stub is disposed on the circular radiation patch and symmetrically arranged to change the current path and broaden the antenna impedance bandwidth. The first rectangular stub and the radiation patch are integrally designed.

2. The circularly polarized array antenna with sequential rotation feeding according to claim 1, wherein The radiation top plate includes 3 or 4 radiation ends, which are respectively coupled to the feeding network.

3. The circularly polarized array antenna with sequential rotation feeding as claimed in claim 1, wherein The centers of the radiation units are on the same circle and are evenly distributed along the circle.

4. The circularly polarized array antenna with sequential rotation feeding according to claim 1, wherein, The radiation top plate includes 8 radiation units sequentially rotated by 45°. They are respectively connected to the matching ports through microstrip lines of equal length to the circular radiation patch.

5. The circularly polarized array antenna with sequential rotation feeding as claimed in claim 1, wherein The bottom plate is an aluminum plate, and the edge of the aluminum plate is configured to have a bent portion bent toward the radiation top plate side.

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