An omnidirectional circularly polarized antenna with dual frequency bands

Abstract

The present invention discloses an omnidirectional circularly polarized antenna with dual frequency bands, comprising a dielectric substrate, an upper surface metal radiating patch, and a lower surface metal radiating patch; the upper surface metal radiating patch comprises a first circular central patch and six first L-shaped auxiliary patches; the first circular central patch is provided with 12 first rectangular slots; the first circular central patch is provided with six metal posts; the six metal posts are evenly distributed between the 12 first rectangular slots; the upper surface metal radiating patch is connected to the lower surface metal radiating patch via the metal posts; the lower surface metal radiating patch comprises a second circular central patch and six second L-shaped auxiliary patches; the second circular central patch is provided with six evenly distributed second rectangular slots; the second rectangular slots are provided near the connection between the second circular central patch and the second L-shaped auxiliary patches. The antenna proposed by the present invention has the advantages of high operating frequency band availability, a wide operating frequency band, a simple structure, ease of manufacture, and stable polarization.

Description

Technical Field

[0001] The present invention relates to the field of antenna technology, and more particularly to an omnidirectional circularly polarized antenna with dual frequency bands. Background Art

[0002] The electromagnetic waves radiated by antennas can be mainly divided into three polarization modes, namely linear polarization, circular polarization, and elliptical polarization, which is between linear polarization and circular polarization. The projection of the trajectory drawn by the end of the electric field vector of a linearly polarized wave on a plane with its propagation direction as the normal vector is a line. Similarly, the projection of the trajectory of the electric field vector of a circularly polarized wave is a circle, and the projection of an elliptically polarized wave is an ellipse. In engineering practice, most of the antennas actually used are not absolutely linearly polarized antennas or circularly polarized antennas, but are mostly elliptically polarized. Researchers will define whether the electromagnetic waves radiated by the antenna are circularly polarized waves or linearly polarized waves based on the ratio of the major axis to the minor axis of the ellipse projected by its polarization orbit, that is, the axial ratio (AR). Circularly polarized antennas and linearly polarized antennas are two commonly used antenna types in wireless communication systems. Compared to linearly polarized antennas, circularly polarized antennas offer several technical advantages: 1) Circularly polarized waves have two rotational directions: left-handed and right-handed. These two rotational directions are orthogonal to each other. This means that a left-handed circularly polarized antenna can only receive left-handed circularly polarized waves, but not right-handed ones, and vice versa. This characteristic helps mitigate the adverse effects of multipath on wireless communication systems and can also be used in polarization diversity design. 2) Circularly polarized antennas have excellent polarization compatibility. While they cannot receive circularly polarized waves with the opposite polarization to their own, they can receive linearly polarized waves of all angles. 3) Circularly polarized waves experience minimal attenuation in rainy and snowy weather and have strong ionosphere penetration. This characteristic helps mitigate the depolarization effects caused by rain, snow, fog, and other weather conditions. In summary, compared to linearly polarized antennas, circularly polarized antennas offer superior polarization compatibility, interference immunity, signal stability, and multipath suppression. Consequently, they are widely used in fields such as satellite communications, wireless communications, and radio measurement.

[0003] Currently, there are many types of circularly polarized antennas. Designing dual-band omnidirectional circularly polarized antennas is a key research and development direction in this field. Dual-band omnidirectional circularly polarized antennas can operate simultaneously in two frequency bands, both with omnidirectional radiation characteristics. Compared with single-band omnidirectional circularly polarized antennas, they can be more effectively applied to complex wireless communications, achieving multi-band omnidirectional transmission. Therefore, dual-band omnidirectional circularly polarized antennas have attracted the attention of many researchers. For example, reference 1 (D. Yu, S. -X. Gong, Y. -T. Wan and W. -F. Chen, "Omnidirectional DualBand Dual Circularly Polarized Microstrip Antenna Using TM01 and TM02 Modes," in IEEE Antennas and Wireless Propagation Letters, vol. 13, pp. 1104-1107, 2014, doi: 10.1109 / LAWP.2014.2328020) discloses an omnidirectional circularly polarized antenna with dual frequency bands, but its operating frequency band is not within the commonly used frequency band, and its gain is low, with a maximum of only 0 dBic; reference 2 (J. -X. Su and F. -S. Zhang, "Capacitive Probe Fed Broadband Circularly Polarized Omnidirectional Antenna," 2018 Cross Strait Quad-Regional Radio Science and Wireless Technology Conference (CSQRWC), Xuzhou, China, 2018, pp. 1-3, doi: 10.1109 / CSQRWC.2018.8455671.) also disclosed an omnidirectional circularly polarized antenna with dual frequency bands, but its operating frequency band is relatively high, and the structure of the antenna cross section is relatively complex, making it difficult to process.

[0004] Therefore, how to provide a dual-band omnidirectional circularly polarized antenna with advantages such as a simple structure and the ability to operate in commonly used frequency bands is a problem that those skilled in the art urgently need to solve. Summary of the Invention

[0005] In view of this, an object of the present invention is to provide an omnidirectional circularly polarized antenna with dual frequency bands, which has the advantages of simple structure and can operate in commonly used frequency bands.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] An omnidirectional circularly polarized antenna with dual frequency bands, comprising a dielectric substrate, an upper surface metal radiation patch, and a lower surface metal radiation patch;

[0008] The upper surface metal radiation patch includes a first circular central patch and six first L-shaped auxiliary patches;

[0009] The six first L-shaped subsidiary patches are equally spaced around the first circular central patch;

[0010] The six first L-shaped subsidiary patches are all connected to the first circular central patch through their radial branches;

[0011] The first circular center patch is provided with 12 first rectangular slots;

[0012] The 12 first rectangular slots are evenly distributed in a spoke shape;

[0013] Six metal pillars are provided on the first circular center patch;

[0014] The six metal pillars are evenly distributed between the twelve first rectangular slots;

[0015] The upper surface metal radiation patch is connected to the lower surface metal radiation patch through a metal column;

[0016] The lower surface metal radiation patch includes a second circular central patch and six second L-shaped subsidiary patches; the six second L-shaped subsidiary patches are equally spaced around the second circular central patch;

[0017] The six second L-shaped subsidiary patches are all connected to the second circular central patch through their radial branches;

[0018] The second circular center patch is provided with 6 second rectangular slots evenly distributed;

[0019] The distance from the outer edge of the second rectangular slot to the connection between the second circular center patch and the second L-shaped auxiliary patch is m, where m is less than or equal to 2 mm;

[0020] Preferably, the first circular center patch is provided with 6 triangular slots;

[0021] The six triangular slots are evenly distributed among the twelve first rectangular slots;

[0022] The six triangular slots and the six metal pillars are staggered with each other;

[0023] Preferably, the distance from the triangular slot to the center of the first circular center patch is greater than the distance from the first rectangular slot to the center of the first circular center patch;

[0024] Preferably, the six metal pillars are evenly distributed between the six second rectangular slots;

[0025] Preferably, a via hole is opened in the center of the dielectric substrate to penetrate the upper surface metal radiation patch and the lower surface metal radiation patch, and the inner conductor of the SMA port is connected to the upper surface metal radiation patch through the via hole; a circular groove is opened in the center of the lower surface metal radiation patch, and the circular groove is used to place the SMA port, and the outer conductor of the SMA port is connected to the lower surface metal radiation patch.

[0026] Preferably, the upper surface metal radiation patch is coated on the upper surface of the dielectric substrate; and the lower surface metal radiation patch is coated on the lower surface of the dielectric substrate.

[0027] Preferably, the diameter of the first circular center patch is equal to the diameter of the second circular center patch.

[0028] Preferably, the six first L-shaped subsidiary patches and the six second L-shaped subsidiary patches have opposite rotation directions.

[0029] Preferably, the metal column, the upper surface metal radiation patch and the lower surface metal radiation patch are all made of copper.

[0030] Preferably, the dielectric substrate is circular, made of FR-4, and has a relative dielectric constant of 4.4.

[0031] Preferably, the outer tangential branch of the first L-shaped accessory patch is arc-shaped.

[0032] Preferably, the outer tangential branch of the second L-shaped accessory patch is arc-shaped.

[0033] It can be seen from the above technical solution that, compared with the prior art, the present invention provides an omnidirectional circularly polarized antenna with dual frequency bands, which can achieve the following beneficial technical effects:

[0034] 1. The antenna of the present invention has a high availability of operating frequency band (i.e., the operating frequency band is a commonly used operating frequency band) and a wide operating frequency band: the 3.6 GHz WiMAX band covers the bandwidth of 3.57 GHz-3.64 GHz; the 5.8 GHz ISM band covers the bandwidth of 5.725 GHz-5.875 GHz; the antenna of the present invention can generate omnidirectional circularly polarized radiation in both frequency bands;

[0035] 2: The antenna of the present invention has a simple structure, is easy to manufacture, and has stable polarization, and can be applied in the field of wearable device technology for the human body. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are merely embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0037] Figure 1 1 is a schematic diagram of the overall structure of a dual-band omnidirectional circularly polarized antenna in one embodiment of the present invention;

[0038] Figure 2 is a top view of a dual-band omnidirectional circularly polarized antenna in one embodiment of the present invention;

[0039] Figure 3 is a bottom view of a dual-band omnidirectional circularly polarized antenna according to an embodiment of the present invention;

[0040] Figure 4 is a graph showing how the reflection coefficient varies with frequency in an embodiment of the present invention;

[0041] Figure 5 is a graph showing the change of axial ratio with frequency in an embodiment of the present invention;

[0042] Figure 6 is the E-plane right-hand circularly polarized radiation pattern of a certain embodiment of the present invention at a frequency of 3.6 GHz;

[0043] Figure 7 is the H-plane right-hand circularly polarized radiation pattern of a certain embodiment of the present invention at a frequency of 3.6 GHz;

[0044] Figure 8 is the E-plane right-hand circularly polarized radiation pattern of a certain embodiment of the present invention at a frequency of 5.8 GHz;

[0045] Figure 9 is the H-plane right-hand circularly polarized radiation pattern of a certain embodiment of the present invention at a frequency of 5.8 GHz;

[0046] Figure 10 This is a graph showing how the right-hand circular polarization gain varies with frequency in an embodiment of the present invention.

[0047] Figures 1 to 3 In the table, each number represents:

[0048] 1. Dielectric substrate; 2. First circular center patch; 3. First L-shaped auxiliary patch; 4. First rectangular slot; 5. Metal column; 6. Triangular slot; 7. Central axis of dielectric substrate; 8. Second circular center patch; 9. Second L-shaped auxiliary patch; 10. Second rectangular slot; 11. Via hole; 12. Circular slot. DETAILED DESCRIPTION

[0049] 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 the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0050] The embodiment of the present invention discloses an omnidirectional circularly polarized antenna with dual frequency bands, comprising a dielectric substrate, an upper surface metal radiation patch, and a lower surface metal radiation patch;

[0051] The upper surface metal radiation patch includes a first circular central patch and six first L-shaped auxiliary patches;

[0052] The six first L-shaped subsidiary patches are equally spaced around the first circular central patch;

[0053] The six first L-shaped subsidiary patches are all connected to the first circular central patch through their radial branches;

[0054] The first circular center patch is provided with 12 first rectangular slots;

[0055] The 12 first rectangular slots are evenly distributed in a spoke shape;

[0056] Six metal pillars are provided on the first circular center patch;

[0057] The six metal pillars are evenly distributed between the twelve first rectangular slots;

[0058] It should be noted that the purpose of distributing 12 first rectangular slots radially in the present invention is to limit the current distribution of the metal column in the horizontal direction, so as to avoid the metal column generating a horizontal polarization component while generating a vertical polarization component, thereby affecting the axial ratio of the antenna, that is, affecting the generation of circularly polarized waves.

[0059] The upper surface metal radiation patch is connected to the lower surface metal radiation patch through a metal column;

[0060] The lower surface metal radiation patch includes a second circular central patch and six second L-shaped auxiliary patches;

[0061] The six second L-shaped subsidiary patches are equally spaced around the second circular central patch;

[0062] The six second L-shaped subsidiary patches are all connected to the second circular central patch through their radial branches;

[0063] The second circular center patch is provided with 6 second rectangular slots evenly distributed;

[0064] The distance from the outer edge of the second rectangular slot to the connection point between the second circular center patch and the second L-shaped auxiliary patch is m, where m is less than or equal to 2 mm.

[0065] It should be noted that the second rectangular slot is mainly used to limit the current distribution of the short-circuit metal column along the tangential direction, so that it cannot generate an electric field component along the tangential direction in the horizontal plane, so as to avoid the short-circuit metal column generating a horizontal polarization component while generating a vertical polarization component, thereby affecting the axial ratio of the antenna, that is, affecting the generation of circularly polarized waves.

[0066] Furthermore, the first circular center patch is provided with 6 triangular slots;

[0067] The six triangular slots are evenly distributed among the twelve first rectangular slots;

[0068] The six triangular slots and the six metal pillars are distributed in an interlaced manner.

[0069] Furthermore, the distance from the triangular slot to the center of the first circular central patch is greater than the distance from the first rectangular slot to the center of the first circular central patch.

[0070] Furthermore, the six metal pillars are evenly distributed among the six second rectangular slots.

[0071] Furthermore, a via hole is opened in the center of the dielectric substrate to penetrate the upper surface metal radiation patch and the lower surface metal radiation patch, and the inner conductor of the SMA port is connected to the upper surface metal radiation patch through the via hole; a circular groove is opened in the center of the lower surface metal radiation patch, and the circular groove is used to place the SMA port, and the outer conductor of the SMA port is connected to the lower surface metal radiation patch.

[0072] Furthermore, the upper surface metal radiation patch is coated on the upper surface of the dielectric substrate; and the lower surface metal radiation patch is coated on the lower surface of the dielectric substrate.

[0073] Furthermore, the diameter of the first circular center patch is equal to the diameter of the second circular center patch.

[0074] Furthermore, the six first L-shaped subsidiary patches and the six second L-shaped subsidiary patches have opposite rotation directions.

[0075] Furthermore, the metal pillar, the upper surface metal radiation patch and the lower surface metal radiation patch are all made of copper.

[0076] Furthermore, the dielectric substrate is circular, made of FR-4, and has a relative dielectric constant of 4.4.

[0077] Furthermore, the outer tangential branch of the first L-shaped auxiliary patch is arc-shaped.

[0078] Furthermore, the outer tangential branch of the second L-shaped auxiliary patch is arc-shaped.

[0079] Furthermore, the structure obtained by rotating the upper surface metal radiation patch 60° clockwise or counterclockwise with the center of the first circular center patch as the center point completely overlaps with the original structure.

[0080] Furthermore, the structure obtained by rotating the lower surface metal radiation patch clockwise or counterclockwise by 60° with the center of the second circular center patch as the center point completely overlaps with the original structure.

[0081] Furthermore, the center of the second circular central patch and the center of the first circular central patch are both located on the central axis of the dielectric substrate.

[0082] In one embodiment, the dielectric substrate has a loss tangent of 0.02, a radius of 27.3 mm, and a thickness of 1.6 mm.

[0083] In one embodiment, the conductivity of the upper surface metal radiation patch and the lower surface metal radiation patch are both 5.8×10 7 S / m, thickness is 0.035mm.

[0084] In one embodiment, the radius of the first circular center patch is 14.8 mm; the radial branches of each of the first L-shaped subsidiary patches are 10 mm in length and 1 mm in width; and the outer tangential branches of each of the first L-shaped subsidiary patches have a central angle of 29.4° and a width of 2.5 mm.

[0085] In one embodiment, the distance from the inner side of each first rectangular slot to the center of the first circular center patch is 5 mm; the length of each first rectangular slot is 6.22 mm, and the width is 0.6 mm.

[0086] In one embodiment, the distance from the bottom edge of each triangular slot to the center of the first circular center patch is 13 mm, and the height of each triangular slot is 1 mm.

[0087] In one embodiment, the radius of each metal pillar is 0.5 mm, and the conductivity is 5.8×10 7 S / m, 6 metal pillars are distributed symmetrically around the center.

[0088] In one embodiment, the radius of the second circular center patch is 14.8 mm, and the radial branches of each of the second L-shaped subsidiary patches are 10 mm in length and 1 mm in width; the outer tangential branches of each of the second L-shaped subsidiary patches have a central angle of 29.4° and a width of 2.5 mm.

[0089] In one embodiment, the radius of the circular slot is 2 mm, and the radius of the via hole is 0.605 mm.

[0090] In one embodiment, the distance from the inner side of each second rectangular slot to the center of the second circular center patch is 9 mm; the length of each second rectangular slot is 4 mm, and the width is 1 mm.

[0091] like Figure 4 As shown, the present invention conducts simulation experiments based on the above parameters to obtain a relationship curve between the reflection coefficient and frequency of the antenna, wherein the horizontal axis is the frequency and the vertical axis on the left is the reflection coefficient; it can be seen from the figure that the impedance bandwidth of the reflection coefficient of the present invention below -10dB is: 3.58GHz~3.66GHz and 5.68GHz~5.94GHz.

[0092] like Figure 5 As shown in the figure, simulation experiments based on the above parameters yielded a curve showing how the antenna's axial ratio varies with frequency, with the horizontal axis representing frequency and the vertical axis representing axial ratio. The figure shows that the circularly polarized bandwidths for which the axial ratio is less than 3dB are 3.57GHz to 3.64GHz and 5.72GHz to 6.02GHz.

[0093] like Figure 6 and Figure 7 As shown in the figure, the present invention conducts simulation experiments based on the above parameters to obtain the radiation patterns of the E-plane and H-plane of the antenna at 3.6 GHz. It can be seen from the figure that the present invention can achieve omnidirectional right-handed circularly polarized radiation on its horizontal plane at 3.6 GHz.

[0094] like Figure 8 and Figure 9 As shown, the present invention conducts simulation experiments based on the above parameters to obtain the radiation patterns of the E-plane and H-plane of the antenna at 5.8 GHz. It can be seen from the figure that the present invention can achieve omnidirectional right-handed circularly polarized radiation on its horizontal plane at 5.8 GHz.

[0095] like Figure 10As shown in the figure, simulation experiments based on the above parameters yielded a curve showing the relationship between the antenna's right-hand circular polarization gain and frequency, with frequency plotted on the horizontal axis and the right-hand circular polarization gain plotted on the left. The figure shows that the gain of the present invention is approximately -3dBi in the 3.6GHz band and approximately 0dBi in the 5.8GHz band.

[0096] In summary, the antenna of the present invention can achieve omnidirectional circularly polarized radiation in two frequency bands: 3.57 GHz to 3.64 GHz and 5.72 GHz to 6.02 GHz.

[0097] The working principle of the present invention is as follows: the principle of generating omnidirectional circularly polarized radiation is to first generate a monopole to radiate a vertically polarized wave, and then generate a circular current to radiate a horizontally polarized wave at the same geometric center. By adjusting the phase difference between the two to be close to 90°, omnidirectional circularly polarized radiation waves can be achieved.

[0098] In the 3.6GHz WiMAX frequency band of the present invention, the metal column acts as a monopole antenna, forming a monopole radiating vertically polarized waves (the triangular slots provided by the present invention can weaken the current distribution between the first rectangular slots where no metal column is provided, thereby enhancing the current on the metal column and ensuring that it has sufficient radiation intensity). At the same time, the horizontally polarized wave is radiated by the outer tangential branches of the first L-shaped auxiliary patch, and the outer tangential branches of the six first L-shaped auxiliary patches form a circular current radiating horizontally polarized waves; by adjusting the radial branch length of the first L-shaped auxiliary patch, the phase difference between the horizontally polarized wave radiated by the above-mentioned circular current and the vertically polarized wave radiated by the monopole generated by the metal column is about 90°, thereby generating omnidirectional circularly polarized radiation. Similarly, on the lower surface of the antenna, the working principles and functions of the second circular center patch, the six second rectangular slots and the six second L-shaped auxiliary patches are similar to those of the structure on the upper surface and will not be repeated here.

[0099] In the ISM band of 5.8 GHz, the surface current distribution of the first central circular patch is TM due to the fact that the first rectangular slot and the triangular slot are not completely closed. 01 Mode, TM 01 The vertically polarized wave will be radiated in the mode, while the task of generating the horizontally polarized wave is still generated by the outer tangential part of the L-shaped branch.

[0100] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. Reference can be made to the common and similar parts between the various embodiments. For the devices disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple, and the relevant parts can be referred to the method description.

[0101] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An omnidirectional circularly polarized antenna with dual frequency bands, characterized in that: It includes a dielectric substrate, an upper surface metal radiation patch and a lower surface metal radiation patch; The upper surface metal radiation patch includes a first circular central patch and six first L-shaped subsidiary patches; the six first L-shaped subsidiary patches surround the first circular central patch at equal intervals; The six first L-shaped subsidiary patches are all connected to the first circular central patch through their radial branches; The first circular center patch is provided with 12 first rectangular slots; The 12 first rectangular slots are evenly distributed in a spoke shape; Six metal pillars are provided on the first circular center patch; The six metal pillars are evenly distributed between the twelve first rectangular slots; The upper surface metal radiation patch is connected to the lower surface metal radiation patch through a metal column; The lower surface metal radiation patch includes a second circular central patch and six second L-shaped auxiliary patches; The six second L-shaped subsidiary patches are equally spaced around the second circular central patch; The six second L-shaped subsidiary patches are all connected to the second circular central patch through their radial branches; The second circular center patch is provided with 6 second rectangular slots evenly distributed; The distance from the outer edge of the second rectangular slot to the connection point between the second circular center patch and the second L-shaped auxiliary patch is m, where m is less than or equal to 2 mm.

2. The dual-band omnidirectional circularly polarized antenna according to claim 1, wherein: The first circular center patch is provided with 6 triangular slots; The six triangular slots are evenly distributed among the twelve first rectangular slots; The six triangular slots and the six metal pillars are distributed in an interlaced manner.

3. The dual-band omnidirectional circularly polarized antenna according to claim 2, wherein: The distance from the triangular slot to the center of the first circular central patch is greater than the distance from the first rectangular slot to the center of the first circular central patch.

4. The dual-band omnidirectional circularly polarized antenna according to claim 1, wherein: The six metal pillars are evenly distributed among the six second rectangular slots.

5. The dual-band omnidirectional circularly polarized antenna according to claim 1, wherein: A via hole is opened in the center of the dielectric substrate to penetrate the upper surface metal radiation patch and the lower surface metal radiation patch. The inner conductor of the SMA port is connected to the upper surface metal radiation patch through the via hole; a circular slot is opened in the center of the lower surface metal radiation patch. The circular slot is used to place the SMA port. The outer conductor of the SMA port is connected to the lower surface metal radiation patch.

6. The dual-band omnidirectional circularly polarized antenna according to claim 1, wherein: The upper surface metal radiation patch is coated on the upper surface of the dielectric substrate; the lower surface metal radiation patch is coated on the lower surface of the dielectric substrate.

7. The dual-band omnidirectional circularly polarized antenna according to claim 1, wherein: The diameter of the first circular center patch is equal to the diameter of the second circular center patch.

8. The dual-band omnidirectional circularly polarized antenna according to claim 1, wherein: The six first L-shaped subsidiary patches and the six second L-shaped subsidiary patches have opposite rotation directions.

9. The dual-band omnidirectional circularly polarized antenna according to claim 1, wherein: The metal column, the upper surface metal radiation patch and the lower surface metal radiation patch are all made of copper.

10. The dual-band omnidirectional circularly polarized antenna according to claim 1, wherein: The dielectric substrate is circular, made of FR-4, and has a relative dielectric constant of 4.4.

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