Multiband antenna with highly integrated cross-polarized dipole radiating elements therein

Abstract

The multiband antenna comprises a relative low-frequency-band cross dipole radiation element, wherein the relative low-frequency-band cross dipole radiation element comprises a first radiation arm, a second radiation arm, a third radiation arm and a fourth radiation arm; and first to fourth relative high-band cross-dipole radiation arms in respective first to fourth openings within the first to fourth radiation arms. The first to fourth relative high-band cross-dipole radiation arms and the first to fourth radiation arms of the relative low-band cross-dipole radiation element are coplanar. The first to fourth isolation frames are disposed in the first to fourth openings, respectively. The invention provides a dielectric substrate. On the dielectric substrate: (i) the first to the fourth relative high-band cross-dipole radiation arms, (ii) the first to the fourth radiation arms of the relative low-band cross-dipole radiation element, and (iii) the first to fourth isolation frames within the first to fourth openings are respectively patterned as metallization traces.

Description

Technical Field

[0001] The present invention relates generally to cellular communication systems and, more particularly, to base station antennas (BSA) utilized in cellular and other communication systems. Background Art

[0002] Cellular communication systems are well known in the art. In a cellular communication system, a geographic area is typically divided into a series of areas called "cells" that are served by corresponding base stations. A base station may include one or more base station antennas that are configured to provide two-way radio frequency ("RF") communications with mobile users within the cell served by the base station. In many cases, each base station is divided into "sectors." In perhaps the most common configuration, a hexagonal-shaped cell is divided into three 120º sectors, and each sector is served by one or more base station antennas having an azimuth half-power beamwidth (HPBW) of approximately 65º. Typically, the base station antenna is mounted on a tower or other elevated structure, with the radiation pattern (also referred to herein as an "antenna beam") generated by the base station antenna pointing outward. The base station antenna is typically implemented as a linear or planar phased array of radiating elements.

[0003] To accommodate the growing volume of cellular communications, cellular operators have added cellular service in a variety of new frequency bands. While in some cases, service in multiple frequency bands can be provided using linear arrays of so-called "wideband" or "ultra-wideband" radiating elements, in other cases, different linear arrays (or planar arrays) of radiating elements must be used to support service in different frequency bands. In the early days of cellular communications, each linear array was typically implemented as a separate base station antenna.

[0004] As the number of frequency bands has proliferated, and as increased sectorization has become more common (e.g., dividing a cell into six, nine, or even twelve sectors), the number of base station antennas deployed at a typical base station has increased significantly. However, there is often a limit to the number of base station antennas that can be deployed at a given base station due to, for example, local zoning regulations and / or weight and wind load constraints on antenna towers. In order to increase capacity without further increasing the number of base station antennas, so-called multi-band base station antennas have been introduced in recent years, in which multiple linear arrays of radiating elements are included in a single antenna. A very common multi-band base station antenna design is the RVV antenna, which includes: one linear array of "low-band" radiating elements for providing services in some or all of the 694-960 MHz band (commonly referred to as the "R band"), and two linear arrays of "high-band" radiating elements for providing services in some or all of the 1695-2690 MHz band (commonly referred to as the "V band"). These linear arrays are mounted in a side-by-side manner.

[0005] There is also great interest in R2V4 base station antennas, which refer to base station antennas having two linear arrays of low-band radiating elements and four linear arrays of high-band radiating elements. However, R2V4 antennas are challenging to implement in a commercially acceptable manner because achieving a 65° azimuth HPBW antenna beam in the low band typically requires low-band radiating elements that are at least 200 mm wide. When two low-band linear arrays are placed side by side, with two high-band linear arrays arranged in between, and another two high-band linear arrays arranged outside the two low-band linear arrays, the base station antenna may have a width of approximately 600-760 mm. Such a large antenna may have very high wind loading, may be very heavy, and / or may be expensive to manufacture. Operators will prefer base station antennas with narrower widths based on a higher degree of multi-band array integration. Summary of the invention

[0006] A highly integrated multi-band antenna according to an embodiment of the present invention includes: (i) a first dipole radiating element having a first pair of radiating arms extending in front of a reflector below; and (ii) a second dipole radiating element having a second pair of radiating arms extending within an opening (e.g., a closed loop) in a first radiating arm of the first pair of radiating arms. According to some of these embodiments, a conductive (and "floating") isolation frame is also provided, the conductive isolation frame surrounding the second pair of radiating arms, and the first pair of radiating arms and the second pair of radiating arms are coplanar. In addition, the first pair of radiating arms and the second pair of radiating arms and the isolation frame can be patterned on a front-facing surface of a dielectric substrate (e.g., a PCB board). The first radiating arm of the first pair of radiating arms and the conductive isolation frame can also be configured as a polygonal (e.g., rectangular) ring.

[0007] According to further embodiments, a multi-band antenna may include: (i) a dipole radiating element having a first radiating arm and a second radiating arm extending forward of an underlying reflector, (ii) a first cross-polarized dipole radiating element having a pair of radiating arms extending within an opening in the first radiating arm, (iii) a second cross-polarized dipole radiating element having a pair of radiating arms extending within an opening in the second radiating arm, and (iv) a first isolation frame surrounding the pair of radiating arms of the first cross-polarized dipole radiating element and extending within the opening in the first radiating arm. In addition, the first and second radiating arms, the pair of radiating arms of the first cross-polarized dipole radiating element, and the first isolation frame are patterned as coplanar metal traces on a front-facing surface of a dielectric substrate. Furthermore, in some of these embodiments, the forward-facing surface of the reflector may have a first region that is spatially closer to the radiating arm of the first cross-polarization radiating element and the radiating arm of the second cross-polarization radiating element than a second region that extends opposite to the first and second radiating arms, thereby functioning as a frequency selective surface (FSS).

[0008] According to another embodiment of the present invention, the multi-band antenna includes: a relatively low-band cross-dipole radiating element, the relatively low-band cross-dipole radiating element including first to fourth radiating arms; and first to fourth relatively high-band cross-dipole radiating arms extending within corresponding first to fourth openings within the first to fourth radiating arms. In some of these embodiments, the first to fourth relatively high-band cross-dipole radiating arms and the first to fourth radiating arms of the relatively low-band cross-dipole radiating element are coplanar. In addition, in order to improve the electrical characteristics of the multi-band antenna and provide a certain degree of stealth to the relatively low-band cross-dipole radiating element, the first to fourth "electrically floating" isolation frames can be respectively arranged within the first to fourth openings. Additionally, the first to fourth radiating arms of the relatively low-band cross-dipole radiating element (e.g., operating in the frequency range of 694 MHz to 960 MHz) may operate to provide stealth relative to radiation provided by the first to fourth relatively high-band cross-dipole radiating arms (e.g., operating in the frequency range of 1695 MHz to 2690 MHz).

[0009] According to further aspects of these embodiments, a dielectric substrate (e.g., a PCB board) may be provided on which: (i) the radiating arms of the first relatively high-band cross-dipole radiating element to the radiating arms of the fourth relatively high-band cross-dipole radiating element, (ii) the first radiating arms to the fourth radiating arms of the relatively low-band cross-dipole radiating element, and (iii) the first isolation frame to the fourth isolation frame within the first opening to the fourth opening are patterned as metallized traces, respectively. And, in further embodiments, this dielectric substrate may be supported by a feed handle that extends in front of the reflector below. The forward-facing surface of the reflector may also have a first region (e.g., a floating "ground" box) that is spatially closer to the first relatively high-band cross-dipole radiating arm to the fourth relatively high-band cross-dipole radiating arm relative to a "grounded" second region that extends relative to the first radiating arm to the fourth radiating arm of the relatively low-band cross-dipole radiating element. Additionally, the first (second, third and fourth) isolation frame may be spatially closer to an outer perimeter of the first (second, third and fourth) relatively high-band cross-dipole radiating arms relative to an inner perimeter of the first (second, third and fourth) radiating arms of the relatively low-band cross-dipole radiating element. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1A is a plan view of a multi-band antenna according to an embodiment of the present invention.

[0011] Figure 1B It consists of a "ground" plane box positioned behind the relatively high-band crossed dipole radiating arms. Figure 1A Side view of the multi-band antenna.

[0012] Figure 1C Is Figure 1B A perspective view of a quadrilateral arrangement of "ground" plane boxes is shown.

[0013] Figure 2A is a front perspective view of a multi-band antenna with a feeding handle according to an embodiment of the present invention.

[0014] Figure 2B yes Figure 2A Rear perspective view of the multi-band antenna.

[0015] Figure 3 According to an embodiment of the present invention, Figure 1A A plan view of a base station antenna with multiple columns of multi-band antennas (integrated with relatively high-band radiating elements).

[0016] Figure 4A is a method for using the invention according to an embodiment of the present invention Figure 2A-2BA perspective view of an array of modified “ground” plane boxes with cutouts in a multi-band antenna.

[0017] Figure 4B is a method that can be used according to an embodiment of the present invention Figure 2A-2B A perspective view of an array of modified “ground” plane boxes with cutouts in a multi-band antenna.

[0018] Figures 5A-5D is a plan view of a metal plate reflector segment that may be used to form a frequency selective surface (FSS) of a reflector according to an embodiment of the present invention. DETAILED DESCRIPTION

[0019] The present invention will now be described more fully with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. However, the present invention may be implemented in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete and will fully convey the scope of the invention to those skilled in the art. Like reference numerals refer to like elements throughout.

[0020] It will be understood that although the terms first, second, third, etc. may be used herein to describe various elements, components, regions, layers, and / or sections, these elements, components, regions, layers, and / or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer, or section from another region, layer, or section. Therefore, without departing from the teachings of the present invention, the first element, component, region, layer, or section discussed below may be referred to as the second element, component, region, layer, or section.

[0021] The terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention. As used herein, unless the context clearly indicates otherwise, the singular forms "a", "an" and "said" are also intended to include plural forms. It will also be understood that the terms "include", "comprise", "have" and their variations, when used in this specification, refer to the presence of the described features, steps, operations, elements and / or parts, but do not exclude the presence or addition of one or more other features, steps, operations, elements, parts and / or their groupings. On the contrary, the term "consisting of...", when used in this specification, refers to the described features, steps, operations, elements and / or parts, and excludes additional features, steps, operations, elements and / or parts.

[0022] Unless otherwise defined, all terms (including technical terms) used herein have the same meaning as commonly understood by those skilled in the art to which the present invention belongs. It will also be understood that terms such as those defined in common dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant art, and should not be interpreted in an idealized or overly formal sense unless explicitly defined as such in this article.

[0023] Reference now Figures 1A-1C , the multi-band antenna 100 according to an embodiment of the present invention is shown to include a relatively low-band cross-dipole radiating element 10, and first to fourth relatively high-band cross-dipole radiating arms 20a, 20b, 20c, 20d respectively associated with the quadrilateral arrangement of the first to fourth relatively high-band radiating elements 20. As shown in the figure, the relatively low-band cross-dipole radiating element 10 includes a first dipole radiating element (e.g., +45 o ) associated with the first and third polygonal radiating arms 10a, 10c, and the second dipole radiating element (eg, -45 o) The second and fourth polygonal radiating arms 10b, 10d associated with the first and fourth relatively high-band cross-dipole radiating arms 20a, 20b, 20c, 20d are respectively positioned within the first to fourth openings 12 within the first to fourth radiating arms 10a, 10b, 10c, 10d together with the corresponding first to fourth "electrically floating" isolation frames 14a, 14b, 14c, 14d. Advantageously, these isolation frames 14a, 14b, 14c, 14d, which may be spatially closer to the relatively high-band cross-dipole radiating arms 20a, 20b, 20c, 20d relative to the relatively low-band cross-dipole radiating arms 10a, 10b, 10c, 10d, may operate to improve the electrical characteristics (e.g., beam patterns, cross-band isolation) of the relatively low-band and relatively high-band radiating elements 10, 20, and to provide a degree of stealth to the relatively low-band cross-dipole radiating element 10. The size of the isolation frames 14a-14d may also affect the impedance matching with the corresponding ones of the high-band cross-dipole radiating arms 20a, 20b, 20c, 20d, but the spacing therebetween should be sufficient to suppress strong coupling by being slightly larger than the spacing between each of the four generally square radiating arms and the corresponding ones of the high-band cross-dipole radiating arms 20a, 20b, 20c, 20d. Although not wishing to be bound by any particular embodiment, the four radiating arms 10a, 10b, 10c, 10d of the relatively low-band cross-dipole radiating element 10 can be configured and dimensioned to operate in a frequency range of approximately 694 MHz to approximately 960 MHz, while the first to fourth relatively high-band cross-dipole radiating arms 20a, 20b, 20c, 20d can be configured and dimensioned to operate in a frequency range of approximately 1695 MHz to approximately 2690 MHz, however, other frequency bands and frequency ranges are also possible.

[0024] As Figure 1A-1BAs best shown, a planar substrate 30, such as a dielectric printed circuit board (PCB), is provided, and the first to fourth radiating arms 10a, 10b, 10c, 10d, the first to fourth cross-dipole radiating arms 20a, 20b, 20c, 20d, and the first to fourth isolation frames 14a, 14b, 14c, 14d are patterned as metallized traces on a forward-facing surface of the substrate 30. In particular, the first to fourth radiating arms 10a, 10b, 10c, 10d and the first to fourth isolation frames 14a, 14b, 14c, 14d may be patterned as rectangular metal rings, while the first to fourth relatively high-band cross-dipole radiating arms 20a, 20b, 20c, 20d may be patterned to have a generally rectangular outer perimeter with a square corner patch 22 and a cross-shaped (and inwardly directed) arm extension 24 within each radiating arm. However, other configurations of radiating arms are possible according to other embodiments of the invention. Additionally, crisscross metal jumpers 32, 34 on the front-facing surface of substrate 30 may be used for analog modeling / testing, but are otherwise omitted from commercial embodiments.

[0025] The multi-band antenna 100 may also be provided with a hybrid reflector 40 extending relative to the rearward-facing surface of the substrate 30, such as by Figure 1B-1C This hybrid reflector 40 is shown as including a planar ground plane reflector 42 and a quadrilateral arrangement of conductive boxes 44a-44d (or elevated metal plate segments) that may be mounted to extend more closely adjacent the rearward facing surface of the substrate 30. In particular, each box 44a, 44b, 44c, 44d may extend diametrically opposite and below a corresponding arrangement of high-band cross-dipole radiating arms 20a, 20b, 20c, 20d, respectively. In some embodiments, these boxes 44a-44d can be configured to function as a three-dimensional (3D) electrically "floating" ground plane segment, which is spatially closer to the substrate 30 relative to the ground plane reflector 42, so that the first region of the hybrid reflector 40 is spatially closer to the first relatively high-band cross-dipole radiating arm 20a, 20b, 20c, 20d relative to the "grounded" second region extending relative to the first to fourth radiating arms 10a, 10b, 10c, 10d.

[0026] In addition, each of the boxes 44a-44d can be configured with hardware and apertures (not shown) therein that support vertical routing of feed signal lines (e.g., 2x coaxial cables, etc.) from the adjacent planar reflector 42 to the substrate 30 and corresponding feed signal traces associated with the relatively high-band cross-dipole radiating arms 20a, 20b, 20c, 20d. For example, in some of these embodiments, the outer conductor of each of a pair of coaxial cables (associated with each of the four high-band radiating elements) can be electrically connected or otherwise sufficiently coupled to a corresponding one of the four boxes 44a, 44b, 44c, 44d, which can remain electrically "floating" relative to a corresponding one of the first to fourth radiating arms 10a, 10b, 10c, 10d (and each other). According to further embodiments, the boxes 44a, 44b, 44c, 44d may be provided with slots or cutouts (not shown) to enhance their frequency selective surface (FSS) and stealth characteristics, and may have lateral dimensions corresponding to (or larger than) the lateral dimensions of the isolation frames 14a-14d but smaller than the lateral dimensions of the first to fourth radiating arms 10a, 10b, 10c, 10d (e.g., to prevent excessive coupling therebetween).

[0027] In addition, if Figure 2A-2B As shown, vertical feed signal routing associated with a relatively low-band cross-dipole radiating element 10 may be provided by a conventional feed stem 50 that is provided below a ground plane reflector 42 (see, e.g., Figure 1B ) (and possibly extending through an underlying ground plane reflector). In an alternative embodiment of the present invention, this feed handle 50 may be modified to include additional signal routing (not shown) to feed signal traces associated with relatively high-band cross-dipole radiating arms 20a, 20b, 20c, 20d. And, as indicated by Figure 2B As best shown, in order to accommodate the lateral dimensions of the vertical feed handle 50, the centrally located corners may be omitted from the quadrilateral arrangement of the conductive boxes 44a'-44d'.

[0028] Reference now Figure 3 , showing that including Figures 1A-1C 2A-2B and three rows of multi-band antennas 100 and two relatively narrow base station antennas (BSA) 300 arranged side by side. Within each column, three separate rows of relatively high-band radiating elements 20 (i.e., excluding the low-band) are also provided with an underlying "ground" plane box (not shown). Advantageously, the use of the multi-band antenna 100 enables the BSA 300 to fit within a narrower housing (not shown) while still maintaining relatively high cross-band isolation.

[0029] Finally, if Figure 4A-4B As shown, Figure 1CThe "ground" plane boxes 44a-44d can be modified to include corner "cutouts" 46 of varying sizes to improve high-band isolation between relatively high-band cross-dipole radiating elements 20 within each multi-band antenna 100. In addition, as shown by Figures 5A-5D As shown, sheet metal reflector segments 52a, 52b, 52c, and 52d with cutouts of varying shapes can be used to form a frequency selective surface (FSS) of the reflector, wherein each planar segment (52a, 52b, 52c, or 52d) replaces an elevated "ground" plane box 44a-44d, and each cutout includes a centrally located and generally polygonal opening 54a and four radially extending openings 54b (e.g., arrow-shaped, Y-shaped, V-shaped) pointing to the four corners of each segment. In addition, in an alternative embodiment, the sheet metal reflector segments 52a, 52b, 52c, and 52d can be configured using patterned metallization (single-sided or double-sided) on a planar dielectric substrate (e.g., a PCB board).

[0030] In the drawings and specification, there have been disclosed typical preferred embodiments of the invention, and although specific terms are employed, they are used in a generic and descriptive sense only and not for purposes of limitation, the scope of the invention being set forth in the following claims.

Claims

1. An antenna, comprising: a first dipole radiating element having a first pair of radiating arms extending forwardly of the reflector; a second dipole radiating element having a second pair of radiating arms extending within an opening in a first radiating arm of the first pair of radiating arms; as well as A conductive isolation frame surrounds the second pair of radiating arms.

2. The antenna of claim 1, wherein the first pair of radiating arms and the second pair of radiating arms are coplanar.

3. The antenna of claim 1, wherein the first pair of radiating arms, the second pair of radiating arms and the isolation frame are coplanar.

4. The antenna of claim 3, wherein the first and second pairs of radiating arms and the isolation frame are patterned on a front-facing surface of a dielectric substrate. 5 . The antenna of claim 3 , wherein the first radiating arm of the first pair of radiating arms is configured as a rectangular loop. The antenna of claim 5 , wherein the conductive isolation frame is configured as a rectangular ring.

7. A multi-band antenna, comprising: a dipole radiating element comprising a first radiating arm and a second radiating arm extending in front of the reflector; as well as A first cross-polarization dipole radiating element having a pair of radiating arms extending within an opening in the first radiating arm.

8. The antenna according to claim 7, further comprising: A first isolation frame surrounds a pair of radiating arms of the first cross-polarization dipole radiating element and extends within the opening in the first radiating arm.

9. The antenna according to claim 7, further comprising: A second cross-polarization dipole radiating element having a pair of radiating arms extending within an opening in the second radiating arm.

10. The antenna of claim 8, wherein the first and second radiating arms, a pair of radiating arms of the first cross-polarized dipole radiating element, and the first isolation frame are patterned on a front-facing surface of a dielectric substrate.

11. The antenna of claim 8, wherein the first radiating arm and the second radiating arm, a pair of radiating arms of the first cross-polarized dipole radiating element, and the first isolation frame are coplanar.

12. The antenna of claim 9, wherein the first radiating arm and the second radiating arm and the radiating arm of the first cross-polarization dipole radiating element and the radiating arm of the second cross-polarization dipole radiating element are coplanar; and wherein the forward-facing surface of the reflector has a first region that is spatially closer to the radiating arm of the first cross-polarization radiating element and the radiating arm of the second cross-polarization radiating element relative to a second region that extends opposite to the first radiating arm and the second radiating arm.

13. The antenna of claim 12, wherein the forward facing surface of the reflector functions as a frequency selective surface (FSS).

14. A multi-band antenna, comprising: A relatively low-band cross-dipole radiating element, the relatively low-band cross-dipole radiating element comprising first to fourth radiating arms; as well as First to fourth relatively high-band cross-dipole radiating arms in the corresponding first to fourth openings in the first to fourth radiating arms.

15. The antenna of claim 14, wherein the first to fourth relatively high-band cross-dipole radiating arms and the first to fourth radiating arms of the relatively low-band cross-dipole radiating element are coplanar. 16 . The antenna according to claim 15 , further comprising first to fourth isolation frames respectively within the first to fourth openings.

17. The antenna according to claim 16, further comprising a dielectric substrate, on which: (i) the first relatively high-band cross-dipole radiating arm to the fourth relatively high-band cross-dipole radiating arm, (ii) the first radiating arm to the fourth radiating arm of the relatively low-band cross-dipole radiating element, and (iii) the first isolation frame to the fourth isolation frame within the first opening to the fourth opening are respectively patterned as metallized traces.

18. The antenna of claim 17, wherein the dielectric substrate is supported by a feed stem extending forward of a reflector below; and wherein a forward-facing surface of the reflector has a first region that is spatially closer to the first to fourth relatively high-band cross-dipole radiating arms relative to a second region extending relative to the first to fourth radiating arms of the relatively low-band cross-dipole radiating element.

19. The antenna of claim 18, wherein the forward facing surface of the reflector functions as a frequency selective surface (FSS).

20. The antenna of claim 16, wherein the first isolation frame is spatially closer to an outer periphery of the first relatively high-band cross-dipole radiating arm than to an inner periphery of the first radiating arm of the relatively low-band cross-dipole radiating element.

21. A multi-band antenna, comprising: Reflector; a first relatively low-band radiating element comprising a first radiating arm extending forwardly of the reflector; a second relatively high-band radiating element, the second relatively high-band radiating element comprising a second radiating arm extending forward of the reflector and coplanar with the first radiating arm; as well as A frequency selective surface extends intermediate the forward facing surface of the reflector and the second radiating arm.

22. The antenna of claim 21, wherein the frequency selective surface comprises a conductive box extending between the second relatively high-band radiating element and the reflector.

23. The antenna of claim 21, wherein the frequency selective surface comprises a planar substrate having a conductive surface thereon facing the second relatively high-band radiating element.

24. The antenna of claim 21, wherein the frequency selective surface comprises a planar metal plate substrate.

25. The antenna of claim 23, wherein the conductive surface has a centrally located and generally polygonal opening therein and four radially extending openings directed toward four corners of the planar substrate.

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