Abstract
A base station antenna (BSA) includes a reflector having a main reflector surface thereon, which extends between first and second sidewalls thereof. First and second choke-within-a-choke assemblies are provided on first and second sides of the reflector, respectively. The first choke-within-a-choke assembly includes: a first relatively low-band choke defined on one side thereof by the first sidewall of the reflector, and a first relatively high-band choke contacting on two sides thereof a rear surface of the reflector and an inner surface of the first sidewall. The second choke-within-a-choke assembly includes: a second relatively low-band choke defined on one side thereof by the second sidewall of the reflector, and a second relatively high-band choke contacting on two sides thereof the rear surface of the reflector and an inner surface of the second sidewall.
Claims
1. A base station antenna, comprising: a reflector having a first plurality of radiating elements on a main reflector surface thereof, said reflector comprising a first rearwardly projecting sidewall on a first side thereof, and a first choke-within-a-choke assembly that comprises at least a portion of the first rearwardly projecting sidewall and wraps behind the main reflector surface so that a first choke opening is provided between a rear surface of said reflector and a portion of a first choke within the first choke-within-a-choke assembly.
2. The antenna of claim 1, wherein said reflector further comprises a second rearwardly projecting sidewall on a second side thereof, and a second choke-within-a-choke assembly that comprises at least a portion of the second rearwardly projecting sidewall and wraps behind the main reflector surface so that a second choke opening is provided between the rear surface of said reflector and a portion of a first choke within the second choke-within-a-choke assembly.
3. The antenna of claim 2, wherein a width of said reflector is equivalent to a width of the main reflector surface, as measured between the first and second rearwardly projecting sidewalls; and wherein the first and second choke-within-a-choke assemblies extend entirely within a space between the first and second rearwardly projecting sidewalls.
4. The antenna of claim 1, wherein the first choke-within-a-choke assembly comprises a first relatively high-band choke within a first relatively low-band choke.
5. The antenna of claim 4, wherein the first relatively low-band choke is configured as an at least three-sided choke; and wherein the first relatively high-band choke is configured as an at least four-sided choke.
6. The antenna of claim 5, wherein the first relatively high-band choke contacts an inner surface of the first rearwardly projecting sidewall.
7. The antenna of claim 6, wherein the first relatively high-band choke contacts the rear surface of said reflector.
8. The antenna of claim 5, wherein the first relatively high-band choke is a five-sided choke; and wherein four of the five sides of the first relatively high-band choke are configured to lie along respective sides of a rectangle when viewed in transverse cross-section.
9. The antenna of claim 8, wherein the first relatively high-band choke abuts an inner surface of the first rearwardly projecting sidewall and the rear surface of said reflector.
10. The antenna of claim 5, wherein the first relatively high-band choke is a five-sided choke with three sides extending parallel to the first rearwardly projecting sidewall and two sides extending parallel to the main reflector surface.
11. The antenna of claim 10, wherein a width of the first relatively high-band choke is in a range from about 0.4 times to about 0.7 times a width of the first relatively low-band choke, when they are viewed in transverse cross-section.
12. The antenna of claim 4, wherein the first rearwardly projecting sidewall has a first slot therein that exposes an opening in the first relatively high-band choke.
13. The antenna of claim 4, wherein said reflector has a first slot therein that exposes an opening in the first relatively high-band choke.
14. The antenna of claim 5, wherein a width of the first relatively high-band choke is in a range from about 0.4 times to about 0.7 times a width of the first relatively low-band choke, when they are viewed in transverse cross-section.
15. The antenna of claim 4, wherein the first relatively low-band choke is the first choke within the first choke-within-a-choke assembly.
16.-54. (canceled)
55. A base station antenna, comprising: a reflector having a main reflector surface thereon, which extends between first and second sidewalls thereof; and a tri-choke assembly, comprising: a relatively low-band choke adjacent the first sidewall of said reflector; a relatively mid-band choke within at least a portion of the relatively low-band choke; and a relatively high-band choke within at least a portion of the relatively mid-band choke.
56. A base station antenna, comprising: a reflector having a non-planar main reflector surface thereon, which is defined by a raised and rigidity-enhancing rib extending at least a majority of the length of the reflector, said reflector comprising a first rearwardly projecting sidewall on a first side thereof, and a first choke that comprises at least a portion of the first rearwardly projecting sidewall and wraps behind the main reflector surface so that a first choke opening is provided between a rear surface of said reflector and a portion of the first choke.
57. The antenna of claim 56, wherein said reflector further comprises a second rearwardly projecting sidewall on a second side thereof, and a second choke that comprises at least a portion of the second rearwardly projecting sidewall and wraps behind the main reflector surface so that a second choke opening is provided between the rear surface of said reflector and a portion of the second choke.
58. The antenna of claim 57, wherein a width of said reflector is equivalent to a width of the main reflector surface, as measured between the first and second rearwardly projecting sidewalls; and wherein the first and second chokes extend entirely within a space between the first and second rearwardly projecting sidewalls.
59. The antenna of claim 58, wherein a width of the rigidity-enhancing rib is in a range from 0.2 to 0.3 times the width of said reflector.
60.-62. (canceled)
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] FIG. 1A is a cross-sectional view of a conventional reflector with RF chokes, which is configured for use in a base station antenna.
[0020] FIG. 1B is an enlarged cross-sectional view of an RF choke implemented within the reflector of FIG. 1A.
[0021] FIG. 1C is a cross-sectional view of an RF choke and a choke cover, which may be utilized to improve performance of the reflector of FIG. 1A.
[0022] FIG. 1D is a cross-sectional view of an RF choke with a choke cover having horizontal and vertical segments, which may be utilized to improve performance of the reflector of FIG. 1A.
[0023] FIG. 1E is a cross-sectional view of a reflector with higher band (HB) and lower band (LB) chokes.
[0024] FIG. 2A is a plan view of a base station antenna reflector having backside multi-choke assemblies integrated therein, according to an embodiment of the invention.
[0025] FIG. 2B is a cross-sectional view of the reflector of FIG. 2A, taken along line 2B-2B.
[0026] FIG. 2C is an enlarged cross-sectional view of the left side higher band (HB) choke of FIG. 2B.
[0027] FIG. 2D is a partial cross-sectional view of the reflector of FIG. 2B as modified to include a tri-choke (e.g., choke-within-a-choke-within-a-choke) assembly, according to an embodiment of the invention.
[0028] FIG. 3A is a perspective view of a base station antenna reflector having backside multi-choke assemblies integrated therein, according to an embodiment of the invention.
[0029] FIG. 3B is a cross-sectional view of the reflector of FIG. 3A taken along line 3B-3B.
[0030] FIG. 3C is an enlarged cross-sectional view of the left side higher band (HB) choke of FIG. 3B.
[0031] FIG. 3D is a partial cross-sectional view of the reflector of FIG. 3B as modified to include a tri-choke (e.g., choke-within-a-choke-within-a-choke) assembly, according to an embodiment of the invention.
[0032] FIG. 3E is a partial side view of the reflector of FIG. 3A as modified to include the tri-choke assembly of FIG. 3D.
[0033] FIG. 4A is a plan view of the reflector of FIG. 2A prior to definition of the left side and right side lower band chokes.
[0034] FIG. 4B is a schematic plan view of base station antenna (BSA) containing side-by-side linear arrays of relatively lower band (LB) and higher band (HB) radiating elements mounted on the reflector of FIG. 2A, according to an embodiment of the invention.
[0035] FIG. 5A is a perspective view of a base station antenna reflector having a raised and rigidity-enhancing rib and a pair of rearwardly-extending chokes, according to an embodiment of the invention.
[0036] FIG. 5B is a cross-sectional view of the reflector of FIG. 5A, taken along line 5B-5B.
DETAILED DESCRIPTION OF EMBODIMENTS
[0037] Referring now to FIG. 1C, the effective path length L1 of the choke 12a of FIGS. 1A-1B may be increased by including a choke cover 18a, which extends over and partially covers the upwardly facing opening in the U-shaped channel 16a and thereby facilitates the design of more compact chokes 12a′ that can support lower frequency bands (i.e., signals having longer wavelengths). Accordingly, by including a choke cover 18a, as shown, the left RF choke 12a′ of FIG. 1C may have a relatively narrow and front facing choke opening 22a and an extended electrical path length L2, which is equivalent to 2×D1+W1+C1.
[0038] Referring now to FIG. 1D, the effective path length L2 of the choke 12a′ of FIG. 1C may be further increased by including a modified and nonplanar choke cover 18a′ attached to a choke 12a″. This modified choke cover 18a′, which extends over an asymmetric U-shaped channel 16a′ having unequal height sides D1 and D2, includes laterally and curved rearwardly extending cover segments C2, C3, as shown. These cover segments C2 and C3 collectively define a modified forwardly-directed choke opening 22a′ that is spaced rearwardly relative to the back 14b of the reflector 10. Based on these segments, the effective path length of the modified choke 12a″ is equivalent to L3, which is the sum of the length of five (5) segments: D1+D2+W1+C2+C3.
[0039] Finally, as shown by FIG. 1E, another conventional antenna reflector 10′, which is configured to support multiple columns of relatively higher band and relatively lower band radiating elements (not shown) on a main reflective surface 20 thereof, may utilize modified U-shaped channels 16a″ that are configured to provide both higher band (HB) chokes and lower band (LB) chokes having different electrical path lengths. As will be understood by those skilled in the art, these HB and LB chokes preferably provide respective 180° phase shifts for RF signals having relatively high and low frequencies associated with the higher band and lower band radiating elements.
[0040] Referring now to FIGS. 2A-2C and 4B, a reflector 100 for a base station antenna (BSA) may be provided with RF choke assemblies, which are integrated into a rear side of the reflector 100, and a dense collection of radiating elements on a front side of the reflector 100. As shown in FIG. 4B, this dense collection of radiating elements may include linear arrays of low-band (LB) radiating elements 220, mid-band (MB) radiating elements 210 and possibly high-band (HB) radiating elements 230, arranged in columns as shown, however, other arrangements and relative placement of columns are possible. In some embodiments of a BSA, one or more groups (e.g., columns) of radiating elements 210, 220 and/or 230 can extend closely to the edges of the reflector 100 in order to make full use of the antenna width for multi-column, multi-band applications. Moreover, because one or more LB, MB and HB arrays of radiating elements may suffer from poor radiation patterns in terms of front-to-back ratio (F/B) and cross polarization ratio (CPR) when they are mounted too close to the edges of the reflector 100, the reflector 100 is preferably provided as a multi-choked reflector 100 with rear side choke-within-a-choke (CWC) assemblies, as defined more fully hereinbelow.
[0041] In particular, the multi-choked reflector 100 is illustrated in FIGS. 2A-2C as including a main reflector surface 102 on a front side 104a of the reflector 100, which is defined on opposing left and right sides by rearwardly extending reflector sidewalls 106a, 106b. As shown best by FIG. 2B, these sidewalls 106a, 106b define respective sides of a pair of 3-sided and relatively long low-band (LB) chokes. These LB chokes on the left and right sides of the reflector 100 include respective “bottoms” 108a, 108b and interior sidewalls 110a, 110b, which extend opposite a rear side 104b of the reflector 100. The exposed ends of interior sidewalls 110a, 110b define opposing choke openings 114a, 114b that face each other adjacent the rear side 104b of the reflector 100. Based on this configuration, the electrical lengths L.sub.LB of these LB chokes are equivalent to the sum of the length of the three sides shown in FIG. 2B (i.e., L.sub.LB=D1+W1+D2). Moreover, because the LB chokes may run the entire length of the reflector 100 as shown by FIG. 2A, they may also contribute significantly to the structural integrity of the antenna, which may be important as the current trends are to include more linear arrays of radiating elements and other components (e.g., diplexers, filters) in order to support advanced communications technologies.
[0042] In addition, a plurality of spaced-apart relatively “higher-band” (HB) chokes 120a, 120b are distributed within the opposing low-band chokes, along the length of the reflector 100, as shown by FIGS. 2A-2B, where the term “higher-band” refers to a higher frequency range relative to the frequency range associated with LB radiating elements 220. Each of these higher-band chokes 120a, 120b is illustrated as a five-sided choke, with vertical sides D3, D4 and D5 and horizontal sides W2 and W3 that collectively yield respective choke lengths L.sub.HB=D5+W3+D4+W2+2(D3), which may correspond to λ/2 where λ is the wavelength of the center frequency of the frequency range associated with the MB radiating elements 210. Although not wishing to be bound by any theory, the relatively high-band chokes 120a, 102b may be configured so that the width dimension W3 is in a range from about 0.4 times to about 0.7 times a width W1 of the low-band chokes along the bottoms 108a, 108b.
[0043] As shown by FIGS. 2B-2C, the ten (10) HB chokes 120a, 120b are configured so that four of the five sides: D3, D4, W2 and W3 lie along edges of a rectangle when these chokes are viewed in transverse cross-section. Moreover, each pair of vertical sides D3 and D5 define respective choke openings, which are exposed to (and receive RF energy from) corresponding elongate openings/slots 112a, 112b within the reflector 100, at corners between the main reflector surface 102 and the reflector sidewalls 106a, 106b. As shown by FIG. 2A, these through-slots 112a, 112b in the reflector 100 expose underlying portions of the rearwardly extending reflector sidewalls 106a, 106b (shown as dark line segments) and underlying portions of the vertical sides D5 of the HB chokes 120a, 120b (shown by speckled shading).
[0044] In addition, as illustrated by the partial cross-sectional view of FIG. 2D, according to still further embodiments of the invention, a respective tri-choke assembly may be provided adjacent each of the pair of rearwardly extending reflector sidewalls of a reflector 100′. In particular, as shown, a relatively high band (HB) choke 122b may be provided at least partially within a relatively mid-band (MB) choke 124b, which may be provided at least partially within a relatively low-band (LB) choke defined by reflector segments 106b, 108b and 110b and choke opening 114b. As further shown by FIG. 2D, elongate choke openings/slots 112b, 116b, which are preferably aligned to each other, are provided to support coupling of RF energy into each of the HB and MB chokes (122b, 124b). As explained more fully hereinbelow with respect to the tri-band antenna 200 of FIG. 4B, the dimensions of the multi-sided LB, MB and HB chokes may be established to support the respective frequency bands associated with the LB, MB and HB radiating elements (220, 210 and 230).
[0045] Referring now to FIGS. 3A-3C, an alternative reflector 100′ may be provided with somewhat enhanced structural integrity relative to the reflector 100 of FIGS. 2A-2C. In particular, as shown by FIGS. 3A-3B, the multiple elongate through-slots 112a, 112b of FIGS. 2A-2B may be moved away from the corners between the main reflector surface 102 and the reflector sidewalls 106a, 106b, to locations in the sidewalls 106a, 106b that are spaced from the structurally supportive corners. As shown by FIGS. 3B-3C, these modified slots 112a′, 112b′ result in a concomitant change in the locations of the openings and the dimensions of the HB chokes 120a′, 120b′, whereby each HB choke 120a′, 120b′ has a somewhat modified length L.sub.HB=D5′+W3+D4+W2+D3+D6, where D5′<D5 (in FIG. 2C) and D6<D3.
[0046] In addition, as illustrated by the partial cross-sectional view of FIG. 3D and the reflector side view of FIG. 3E, a modified tri-choke assembly may be provided adjacent each of the pair of rearwardly extending sidewalls of a reflector 100″. According to this multi-choke assembly, a relatively high band (HB) choke 122b′ is provided, which is nested within and adjacent a relatively mid-band (MB) choke 124b′, which itself is nested within a relatively low-band (LB) choke defined by reflector segments 106b, 108b and 110b and choke opening 114b. As further shown by FIGS. 3D-3E, elongate choke openings/slots 112b′, 118b, which are aligned to expose an interior of a respective one of the MB and HB chokes, are preferably distributed along the reflector sidewall 106b to thereby support coupling of RF energy into each of the MB and HB chokes (124b′, 122b′).
[0047] Furthermore, as shown by FIGS. 5A-5B, a base station antenna reflector 100′″ may be provided with a raised and rigidity-enhancing rib 124 intermediate the front side 104a of the reflector 100′″, which advantageously enables the use of thinner reflectors 100′″ (e.g., 25% thinner). According to some embodiments of the invention, the rigidity-enhancing rib 124 may have a width (W.sub.rib) in a range from about 0.2 to about 0.3 times the width (W.sub.ref) of the reflector 100′″. For example, a rib 124 having a width of 75 mm may be provided for a reflector 100′″ having a width of 287 mm and thickness of 1.2 mm (reduced from 1.6 mm).
[0048] As shown, the reflector 100′″ also includes a pair of rearwardly-extending chokes, which are defined by rearwardly extending sidewalls 106a, 106b, choke bottoms 108a, 108b, and interior choke sidewalls 110a, 110b that extend opposite a rear side 104b of the reflector 100′″. The exposed ends of interior sidewalls 110a, 110b define opposing choke openings 114a, 114b, which face each other adjacent the rear side 104b of the reflector 100′″. These rearwardly-extending chokes may be utilized independently, as shown by FIGS. 5A-5B, or may be utilized in combination with the multi-choke assemblies illustrated in cross-section by FIGS. 2B, 3B and 3D.
[0049] Referring now to FIGS. 4A-4B, the main reflector surface 102 and the pair of LB chokes associated with the reflector 100 of FIGS. 2A-2B, may be formed from a single sheet of electrically conductive material (e.g., aluminum (Al)) having a width W, a length L, and two columns of elongate slots (S.sub.1-S.sub.N), as through-holes of predetermined length L.sub.S. As shown by FIG. 4A, the width W is equivalent to a sum of the width W1 of the desired main reflector surface 102, and the “electrical” lengths of the left and right LB chokes (i.e., D1+W1+D2=W.sub.2L=W.sub.2R), and the dotted lines represent the bend/fold lines associated with manufacturing the metal sheet into a structurally rigid antenna reflector 100 for the antenna 200 of FIG. 4B. This antenna 200 is configured to support linear arrays of mid band MB radiating elements 210 (e.g., f.sub.MB=1427-2690 MHz), relatively low band LB radiating elements 220 (f.sub.LB=e.g., 694-960 MHz) and possibly even high-band HB radiating elements 230 (e.g., f.sub.HB=3300-3800 MHz) on a densely populated reflector 100 having a width W.sub.R.
[0050] The present invention has been described above with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as being 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.
[0051] 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. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the present invention.
[0052] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present invention. As used herein, the singular forms “a,” “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprising”, “including”, “having” and variants thereof, when used in this specification, specify the presence of stated features, elements, and/or components, but do not preclude the presence or addition of one or more other features, elements, components, and/or groups thereof. In contrast, the term “consisting of” when used in this specification, specifies the stated features, elements, and/or components, and precludes additional features, elements and/or components.
[0053] 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 the present invention 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.
[0054] 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.
