CN212848827U

CN212848827U - Antenna element and antenna structure with same

Info

Publication number: CN212848827U
Application number: CN202022361833.4U
Authority: CN
Inventors: 赵慈旭; 穆乐思
Original assignee: Hong Kong University of Science and Technology HKUST
Current assignee: Hong Kong University of Science and Technology HKUST
Priority date: 2019-10-22
Filing date: 2020-10-21
Publication date: 2021-03-30
Anticipated expiration: 2030-10-21

Abstract

The utility model relates to an antenna element. The antenna element includes: a ground plane; a feed patch supported on the ground plane by the probe and the pin; and a radiator disposed above the feed patch and having a snowflake-shaped top patch having an unfolded branch member and a folded branch member, the folded branch member and the unfolded branch member being alternately arranged along an edge of the top patch, the radiator being suspended with respect to a ground plane.

Description

Antenna element and antenna structure with same

Technical Field

The present invention relates to an antenna element and an antenna structure having the same, and particularly to a compact patch antenna for broadband operation.

Background

In large scale Multiple Input Multiple Output (MIMO) applications, the size of the MIMO antenna array formed by multiple antenna elements (typically 100 or more) is very large. It is therefore desirable to reduce the size of the antenna array, particularly in the case of the conventional mobile frequency band (i.e. below 6 GHz). One solution for size reduction is to utilize a multimode antenna as a unit to allow more antenna ports to be implemented in a given area. However, in an ideal case, the radiation pattern of each antenna port in a massive MIMO antenna array should be omnidirectional or cover the desired base station sector, so that each antenna port can receive as many multipath signals as possible. For outdoor base station antennas this usually means that a broadside radiation pattern is required that is wide enough to cover the sector of interest. Generally, the resulting overlap in the broadside direction radiation patterns generally increases mutual coupling. In this case, in order to suppress mutual coupling, it is necessary to separate the antenna elements far apart or an additional technique is required.

SUMMERY OF THE UTILITY MODEL

One aspect of the present disclosure provides an antenna element, including: a ground plane; a feed patch supported on the ground plane by the probe and the pin; and a radiator disposed above the feed patch and having a snowflake-shaped top patch having an unfolded branch member and a folded branch member, the folded branch member and the unfolded branch member being alternately arranged along an edge of the top patch, the radiator being suspended with respect to a ground plane.

In an embodiment of the present disclosure, the top patch has three unfolding leg members and three folding leg members.

In an embodiment of the present disclosure, the unfolding leg member protrudes outwardly along an edge of the top patch, and the folding leg member is folded from the edge of the top patch towards the ground plane.

In an embodiment of the disclosure, the radiator further comprises a bottom lower layer, the folded branch member being located between and interconnecting the top patch and the bottom lower layer.

In an embodiment of the disclosure, the radiator has a rotationally symmetric physical geometry.

In an embodiment of the present disclosure, the radiator is spaced apart from the feeding patch by a predetermined distance.

In an embodiment of the present disclosure, the ground plane has a circular or polygonal shape.

In an embodiment of the present disclosure, the ground plane has a regular hexagonal shape.

According to another aspect of the present disclosure, there is provided an antenna structure comprising one or more of the above-described antenna elements.

In an embodiment of the present disclosure, the plurality of antenna elements are arranged in a honeycomb shape.

Various embodiments of the present disclosure may have at least one of the following benefits:

1) the size of the antenna (e.g. a three-port antenna) is about the same as a conventional dual-port dual-polarized patch antenna, allowing for an increase of e.g. 50% of the antenna elements for the same array aperture; and

2) by cutting the ground plane into a hexagonal shape, standard antennas can be connected together to form a massive MIMO antenna array, where all radiation patterns of the antenna array point in broadside directions with low mutual coupling.

Drawings

The accompanying drawings, which are included to provide a further understanding of the disclosure, constitute a part of this specification and illustrate preferred embodiments of the disclosure, and together with the description serve to explain the principles of the disclosure. The drawings depict some embodiments of the present disclosure and from which others may be derived by those skilled in the art without the exercise of inventive faculty.

Fig. 1 shows the general structure of a prior art patch antenna.

Fig. 2(a) and 2(b) illustrate an example of a broadband compact three-mode patch antenna according to an embodiment of the present disclosure

Fig. 3(a) and 3(b) show simulation and measurement diagrams of the variation of the S-parameter with frequency for different antenna ports.

Fig. 4(a) and 4(b) show simulation and measurement diagrams of the gain versus frequency for the shown examples of different antenna ports.

Fig. 5(a) and 5(b) show simulation and measurement diagrams of the efficiency as a function of frequency for the shown examples of different antenna ports.

Fig. 6(a) to 6(f) show simulated and measured radiation patterns at 3.4GHz, 3.6GHz and 3.8GHz for the illustrated example of port 1 in the xz plane.

Fig. 7(a) to 7(f) show simulated and measured radiation patterns for the illustrated example of port 1 in the yz plane at 3.4GHz, 3.6GHz and 3.8 GHz.

Fig. 8(a) to 8(f) show simulated and measured radiation patterns for the shown example of port 1 in the xy plane at 3.4GHz, 3.6GHz and 3.8 GHz.

Fig. 9(a) and 9(b) show examples of two sets of antenna elements with a regular hexagonal ground plane according to an embodiment of the present disclosure.

Fig. 10 shows an example of antenna elements of one embodiment of the present disclosure joined together to form a massive MIMO antenna array.

Detailed Description

For a better understanding of the present disclosure, various aspects of the present disclosure will be described in more detail with reference to the accompanying drawings. It should be understood that the detailed description is merely illustrative of exemplary embodiments of the disclosure and is not intended to limit the scope of the disclosure in any way. Like reference numerals refer to like elements throughout the specification. The expression "and/or" includes any and all combinations of one or more of the associated listed items.

It should be noted that the expressions first, second, etc. in this specification are used only to distinguish one feature from another feature, and do not indicate any limitation on the features. Thus, a first body discussed below may also be referred to as a second body without departing from the teachings of the present disclosure.

In the drawings, the thickness, size, and shape of an object have been slightly exaggerated for convenience of explanation. The figures are purely diagrammatic and not drawn to scale.

It will be further understood that the terms "comprises," "comprising," "includes," "including," "has," "including," and/or "including," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. Moreover, when a statement such as "at least one of" appears after a list of listed features, the entirety of the listed features is modified rather than modifying individual elements in the list. Furthermore, when describing embodiments of the present disclosure, the use of "may" mean "one or more embodiments of the present disclosure. Also, the term "exemplary" is intended to refer to an example or illustration.

As used herein, the terms "substantially," "about," and the like are used as terms of table approximation and not as terms of table degree, and are intended to account for inherent deviations in measured or calculated values that will be recognized by those of ordinary skill in the art.

Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

It should be noted that, in the present disclosure, the embodiments and features of the embodiments may be combined with each other without conflict. The present disclosure will be described in detail below with reference to the accompanying drawings in conjunction with embodiments.

Embodiments of the present disclosure relate to an antenna element. The patch element may be a broadband compact three-mode patch antenna. All radiation of the antenna is directed in the broadside direction. The impedance bandwidth of the antenna of the present disclosure is at least, for example, 18%, and the antenna can have low mutual coupling while supporting three-port excitation. The present disclosure is not limited to a particular resonant frequency, which is determined by the size of the antenna. For example, a lower resonant frequency can be obtained by amplifying the entire antenna element. The present disclosure also does not limit the geometry of the antenna as long as it is rotationally symmetric.

Fig. 1 shows the general structure of a prior art patch antenna 100. The antenna 100 comprises a patch radiator 10, a feed patch 11 and a ground plane 14. The radiator 10 has a single-layer structure and is rotationally symmetric. The radiator 10 is made of metal and is suspended in air. The radiator 10 is not limited to a particular geometry and may be circular, hexagonal or any other shape that is rotationally symmetric. Further, the radiator 10 is not limited to a single-layer structure, and may be a multi-layer structure having a folded structure.

In the present embodiment, the feeding patch 11 is disposed under the radiator 10 and spaced apart from the radiator 10. In the present embodiment, the number of the feeding patches may be, for example, three, but the present disclosure is not limited thereto, and the number of the feeding patches may be adjusted as needed. In the present embodiment, since there is no physical connection between the feeding patch 11 and the radiator 10, the radiator 10 can be capacitively fed by three feeding patches 11 made of metal. The capacitive feeding of the antenna port excitation can cancel out some of the probe inductance, resulting in better impedance matching. The feeding patch 11 is not limited to a particular geometric shape, and may be circular, rectangular, or any other shape. The feed patch 11 is supported on a ground plane 14 made of metal by an antenna probe 12 and a shorting pin 13. The shorting pin 13 is not limited to a particular geometry. The separation distance between the radiator 10 and the feed patch 11, the position of the shorting pin 13, etc. help determine the impedance matching of the antenna.

Fig. 2(a) and 2(b) illustrate an example of a broadband compact three-mode patch antenna according to an embodiment of the present disclosure.

In the present embodiment, the antenna element has a patch radiator 20, a feed patch 25, and a ground plane 26. As shown in the drawing, the radiator 20 has a snowflake-like shape of the top patch, and has unfolded branches and folded branches alternately arranged along the edge of the top patch. As shown in fig. 2(a), the unfolded branch projects outwardly along the edge of the top patch, and the folded branch is folded from the edge of the top patch toward the ground plane 26, but does not contact the ground plane 26. That is, the radiator 20 is suspended as the ground plane 26. In the present embodiment, the shape of the top patch and the number of folding branches and unfolding branches are not limited thereto, and other shapes of the top patch and other numbers of folding branches and unfolding branches may be provided as needed without departing from the principles of the present disclosure. As shown in fig. 2(a), the radiator 20 has a rotationally symmetric physical geometric profile and is made of, for example, metal.

In this embodiment the folded branch comprises a lower structure 22 and a vertical structure 21, wherein the vertical structure 21 is located between the top patch of the radiator 20 and the lower structure 22 and connects the top patch and the lower structure 22 to each other. That is, in the present embodiment, the antenna element has a two-layer structure (the snowflake patch and the lower layer structure 22 on the top, respectively), in which the lower layer structure 22 is not in contact with the ground plane 26. Further, in a plan view (for example, when viewed in the z-axis direction), the unfolded branches are located between the folded branches adjacent to each other. In the present disclosure, due to this distributed structure of the folded and unfolded branches, it is helpful to generate two nearby antenna resonances for broadband operation. Folding the branches may reduce the overall antenna projected area in the xy plane.

Fig. 2(b) shows a perspective view of an example in which the radiator 20 is removed. It should be understood that the purpose of removing the top patch of the antenna element is merely to facilitate the illustration of the internal structure of the antenna element, and the top patch is not removed in actual use. Similar to the antenna element described in fig. 1, the feed patch 25 is disposed below the radiator 20 and spaced apart from the radiator 20. Since there is no physical connection between the feed patch 25 and the radiator 20, the radiator 20 can be capacitively fed by the feed patch 25 made of metal. The feed patch 25 is supported on the ground plane 26 by the antenna probes 23, 27 and 28 and the shorting pin 24. In the present embodiment, the number of the feeding patches 25 is, for example, three, and thus, the number of the antenna probes and the shorting pins is also three, but any number of the feeding patches, the antenna probes, and the shorting pins may be selected by those skilled in the art as needed. The three feed patches 25 are excited by three

probes

23, 27 and 28 corresponding to the three ports, respectively. The shorting pin 24 is connected to a circular ground plane 26 printed on an FR-4 epoxy board. It should be noted that the connection structure between the feed patch 25, the antenna probe and the shorting pin may be any one of those known in the art without departing from the principles of the present disclosure, which is not limited by the present disclosure as long as the shorting pin and the antenna probe can support the feed patch on the ground plane.

In the present embodiment, the ground plane 26 is illustrated as a circle, but the present disclosure is not limited thereto, and may also have other polygonal shapes such as a regular hexagonal shape as described later with reference to fig. 9(a) and 9 (b).

As shown in fig. 2(a) and 2(b), the top patch, the lower layer structure 22, the feed patch 25 and the ground plane 26 of the radiator 20 are parallel or substantially parallel to each other.

Fig. 3(a) shows a simulated schematic of the variation of the S-parameter with frequency for different antenna ports. Since the entire antenna structure is rotationally symmetric, the reflection coefficients S11, S22, and S33 should be the same in theory. Furthermore, the mutual coupling between the ports should be the same. The slight difference between ports is caused by meshing in Electromagnetic (EM) computation. In this example, the 10dB impedance bandwidth is 18.2%, and the coupling coefficient between any two ports in this band is below-14.2 dB.

Fig. 3(b) shows a measurement diagram of the variation of the S-parameter with frequency for different antenna ports. The slight differences between the ports are due to manufacturing tolerances. By prototyping in a commercial shop, manufacturing accuracy can be improved. When compared to fig. 3(a), good agreement is obtained between the simulation results and the measurement results.

Fig. 4(a) shows a simulated schematic of the gain versus frequency for the illustrated example for different antenna ports. Note that the three curves are very close to each other. The antenna gain varies between 7.08dBi and 7.97dBi within the 10dB impedance bandwidth.

Fig. 4(b) shows a measurement diagram of gain versus frequency for the illustrated example for different antenna ports. The slight differences between the ports are due to manufacturing tolerances. By prototyping in a commercial shop, manufacturing accuracy can be improved. When compared with fig. 4(a), good agreement is obtained between the simulation results and the measurement results.

Fig. 5(a) shows a simulated schematic of the efficiency of the illustrated example as a function of frequency for different antenna ports. Note that the three curves are very close to each other. The overall antenna efficiency varies between 81.7% and 97.5% over a 10dB impedance bandwidth.

Fig. 5(b) shows a measurement diagram of the efficiency versus frequency for the shown example for different antenna ports. The slight differences between the ports are due to manufacturing tolerances. By prototyping in a commercial shop, manufacturing accuracy can be improved. When compared with fig. 5(a), good agreement is obtained between the simulation results and the measurement results.

Fig. 6(a) to 6(f) show simulated and measured radiation patterns at 3.4GHz, 3.6GHz and 3.8GHz for the illustrated example of port 1 in the xz plane. Fig. 6(a), 6(c) and 6(e) are simulated radiation patterns at 3.4GHz, 3.6GHz and 3.8GHz, respectively. Fig. 6(b), 6(d) and 6(f) are measured radiation patterns at 3.4GHz, 3.6GHz and 3.8GHz, respectively. Note that

ports

2 and 3 terminate with a 50 Ω load during the measurement. Solid black and dash-marked gray lines correspond to

And E theta. The consistency of the simulation result and the measurement result is better. The radiation patterns of

ports

2 and 3 are the same, but rotated +/-120 degrees about the z-axis due to the rotationally symmetric antenna geometry. When the radiation pattern of port 1 is pointing broadside, the radiation patterns of

ports

2 and 3 are also pointing broadside. The characteristics of broadside radiation are obtained and maintained over a wide frequency range.

Fig. 7(a) to 7(f) show simulated and measured radiation patterns at 3.4GHz, 3.6GHz and 3.8GHz for the illustrated example of port 1 in the yz plane. Fig. 7(a), 7(c) and 7(e) are simulated radiation patterns at 3.4GHz, 3.6GHz and 3.8GHz, respectively. FIG. 7(b) and FIG. 7(b)(d) And FIG. 7(f) is the measured radiation patterns at 3.4GHz, 3.6GHz and 3.8GHz, respectively. Note that

ports

ports

Fig. 8(a) to 8(f) show simulated and measured radiation patterns at 3.4GHz, 3.6GHz and 3.8GHz for the shown example of port 1 in the xy plane. Fig. 8(a), 8(c) and 8(e) are simulated radiation patterns at 3.4GHz, 3.6GHz and 3.8GHz, respectively. Fig. 8(b), 8(d) and 8(f) are measured radiation patterns at 3.4GHz, 3.6GHz and 3.8GHz, respectively. Note that

ports

ports

2 and 3 are the same, but rotated +/-120 degrees about the z-axis due to the rotationally symmetric antenna geometry.

Fig. 9(a) and 9(b) show examples of two sets of antenna elements with a regular hexagonal ground plane. The structure, material and size are the same as those of the antenna element in fig. 2(a) and 2(b) except that the ground plane 30 becomes a regular hexagon. Since the antenna elements of the present disclosure are rotationally symmetric about the z-axis at 120 degrees, the regular hexagonal ground plane allows two antenna elements to be cascaded together. Note that as shown in fig. 9(b), the unfolded branch of one antenna element points to the folded branch of the other antenna element.

Fig. 10 shows an example of seven groups of antenna elements with a regular hexagonal ground plane. The structure, material and size are the same as those of the antenna element in fig. 2(a) and 2(b) except that the ground plane 30 becomes a regular hexagon. The example of fig. 10 is a further extension of the example of fig. 9. Note that as shown in fig. 10, the unfolded branches of one antenna element are arranged to point to the folded branches of the other antenna elements, respectively. The present disclosure is not limited to the number of antenna elements, and may be applied to any number of antenna elements without departing from the technical idea of the present disclosure. The mutual coupling between the antenna elements depends mainly on the spacing between the elements. The smaller the pitch, the higher the mutual coupling.

Embodiments of the present disclosure provide compact antenna structures for broadband operation. The three antenna ports are capable of simultaneously exhibiting broadside radiation while maintaining low mutual coupling. The maximum dimension in the projected area of the antenna element of the present disclosure is 0.45 λ₀(λ₀Is a wavelength in air) similar to a standard half-wavelength dual-polarized dual-port patch antenna. This means that antenna port increments of, for example, 50% can be achieved. The Antenna of the present disclosure is a broadband version of the prior U.S. patent "Compact Integrated Three Broadside-Mode Patch Antenna" in which the 10dB impedance bandwidth has been tripled. In the present disclosure, by changing a regular snowflake radiator with six branches folded towards the ground to an irregular snowflake radiator with three unfolded branches and three folded branches, the mutual coupling can be kept low while broadside radiation is present. In the present disclosure, the folded and unfolded branches alternate, and this particular configuration helps to create two nearby antenna resonances for broadband operation. This helps to achieve better impedance matching over the frequency band of interest, since the shape and arrangement of the branches is optimized. Due to the rotationally symmetric geometry with respect to the three antenna ports, the antenna elements of the present disclosure can be expanded to any number in azimuth to meet the needs of a massive MIMO system. Furthermore, the hexagonal antenna geometry facilitates suppression of mutual coupling between elements after cascading. The antenna of the present disclosure is capable of covering a range of up to 3GHz used in a 5G communication system.

Those skilled in the art will appreciate that the embodiments of the present disclosure may be implemented in other specific forms without changing the technical spirit or essential characteristics thereof. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive. The scope of the embodiments of the present disclosure is defined by the appended claims, rather than the above detailed description, and all changes and modifications that come within the meaning and range of equivalency of the claims are intended to be embraced therein.

Claims

1. An antenna element, comprising:

a ground plane;

a feed patch supported on the ground plane by a probe and a pin; and

a radiator disposed above the feed patch and having a snowflake-shaped top patch with unfolded branch members and folded branch members alternately arranged along an edge of the top patch, the radiator being suspended with respect to the ground plane.

2. The antenna element of claim 1, wherein said top patch has three said unfolded branch members and three said folded branch members.

3. The antenna element of claim 2, wherein the unfolding branch member protrudes outward along an edge of the top patch, and the folding branch member is folded from the edge of the top patch toward the ground plane.

4. An antenna element according to claim 3, wherein the radiator further comprises a bottom lower layer, the folded branch member being located between and interconnecting the top patch and the bottom lower layer.

5. The antenna element of claim 1, wherein the radiator has a rotationally symmetric physical geometry.

6. The antenna element of claim 1, wherein the radiator is spaced a predetermined distance from the feed patch.

7. The antenna element of claim 1, wherein the ground plane has a circular or polygonal shape.

8. The antenna element of claim 7, wherein the ground plane has a regular hexagonal shape.

9. An antenna structure, characterized in that it comprises a plurality of antenna elements as claimed in any one of claims 1 to 8.

10. An antenna structure according to claim 9, wherein the plurality of antenna elements as claimed in any one of claims 1 to 8 are arranged in a honeycomb pattern.