US-12620691-B2 - Base station antennas having radiating elements with active and/or cloaked directors for increased directivity

US12620691B2US 12620691 B2US12620691 B2US 12620691B2US-12620691-B2

Abstract

Base station antenna include an RF port, a reflector, a linear array of radiating elements mounted to extend forwardly from the reflector, and a feed network that electrically connects the RF port to each of the radiating elements in the linear array. The radiating elements are configured to operate in a first frequency band. A first of the radiating elements is a cross-dipole radiating element that includes a feed stalk, a cross-dipole radiator that includes a first −45° polarization dipole radiator and a first +45° polarization dipole radiator mounted on the feed stalk, and an active director that includes a second −45° polarization dipole radiator and a second +45° polarization dipole radiator mounted forwardly of the cross-dipole radiator. Both the cross-dipole radiator and the active director are coupled to the feed network.

Inventors

Bo Wu

Assignees

Outdoor Wireless Networks LLC

Dates

Publication Date: 20260505
Application Date: 20220216

Claims (20)

1 . A base station antenna, comprising: a reflector; a first linear array of lower-band radiating elements mounted to extend forwardly from the reflector, the lower-band radiating elements configured to transmit and receive radio frequency (“RF”) signals in a first frequency band; and a second linear array of higher-band radiating elements mounted to extend forwardly from the reflector, the higher-band radiating elements configured to transmit and receive RF signals in a second frequency band that is at higher frequencies than the first frequency band, wherein a first of the lower-band radiating elements includes first and second dipole radiators and a director mounted forwardly of the first and second dipole radiators, wherein both the first and second dipole radiators and the director are cloaked using resonant circuits to reduce or eliminate scattering of RF energy emitted by the higher-band radiating elements, and wherein the director comprises a first dipole arm and a second dipole arm.
2 . The base station antenna of claim 1 , wherein the first of the lower-band radiating elements comprises a feed stalk, and the first and second dipole radiators comprise a −45° polarization dipole radiator and a +45° polarization dipole radiator that form a cross-dipole radiator that is mounted on the feed stalk.
3 . The base station antenna of claim 2 , further comprising a lower-band feed network that couples a first RF port and a second RF port to each of the lower-band radiating elements in the first linear array, wherein the director is a passive director that is not coupled to the lower-band feed network.
4 . The base station antenna of claim 2 , further comprising a lower-band feed network that couples a first RF port and a second RF port to each of the lower-band radiating elements in the first linear array, wherein the director is an active director that includes a −45° polarization dipole radiator and a +45° polarization dipole radiator that are each coupled to the lower-band feed network.
5 . A base station antenna, comprising: a reflector; a first linear array of lower-band radiating elements mounted to extend forwardly from the reflector, the lower-band radiating elements configured to transmit and receive radio frequency (“RF”) signals in a first frequency band; and a second linear array of higher-band radiating elements mounted to extend forwardly from the reflector, the higher-band radiating elements configured to transmit and receive RF signals in a second frequency band that is at higher frequencies than the first frequency band, wherein a first of the lower-band radiating elements includes first and second dipole radiators and a director mounted forwardly of the first and second dipole radiators, wherein both the first and second dipole radiators and the director are cloaked using resonant circuits to reduce or eliminate scattering of RF energy emitted by the higher-band radiating elements, wherein the first of the lower-band radiating elements comprises a feed stalk, and the first and second dipole radiators comprise a −45° polarization dipole radiator and a +45° polarization dipole radiator that form a cross-dipole radiator that is mounted on the feed stalk, wherein the feed stalk extends through a central portion of the cross-dipole radiator, and the director is mounted on the feed stalk.
6 . The base station antenna of claim 2 , wherein the director is mounted forwardly of the cross-dipole radiator by at least ⅛ th of a wavelength corresponding to a center frequency of the first frequency band.
7 . The base station antenna of claim 6 , wherein the director is mounted forwardly of the cross-dipole radiator by no more than ¼ th of the wavelength corresponding to the center frequency of the first frequency band.
8 . The base station antenna of claim 2 , wherein a shape of the director is substantially the same as a shape of the cross-dipole radiator.
9 . The base station antenna of claim 2 , wherein the director is configured to narrow azimuth beamwidths of antenna beams generated by the cross-dipole radiator.
10 . The base station antenna of claim 2 , wherein the cross-dipole radiator is formed on a first dipole radiator printed circuit board and the director is formed on a second dipole radiator printed circuit board.
11 . The base station antenna of claim 1 , further comprising a third linear array of lower-band radiating elements mounted to extend forwardly from the reflector and configured to transmit and receive RF signals in the first frequency band, wherein the lower-band radiating elements of the first and third linear arrays of lower-band radiating elements are arranged in first and second vertically-extending columns, with all but a last of the lower-band radiating elements in the first vertical column and a last of the lower-band radiating elements in the second vertical column constituting the first linear array of lower-band radiating elements, and all but the last of the lower-band radiating elements in the second vertical column and the last of the lower-band radiating elements in the first vertical column constituting the third linear array of lower-band radiating elements.
12 . The base station antenna of claim 1 , wherein the first frequency band comprises the 617-960 MHz frequency band or a portion thereof, and the second frequency comprises the 1427-2690 MHz frequency band or a portion thereof.
13 . A base station antenna, comprising: a reflector; a first column of lower-band radiating elements mounted to extend forwardly from the reflector, the lower-band radiating elements configured to transmit and receive radio frequency (“RF”) signals in a first frequency band; a second column of lower-band radiating elements mounted to extend forwardly from the reflector; a third column of higher-band radiating elements mounted to extend forwardly from the reflector, the higher-band radiating elements configured to transmit and receive RF signals in a second frequency band that is at higher frequencies than the first frequency band; a first RF port; and a second RF port, wherein the lower-band radiating elements in the first column and at least a first additional lower-band radiating element form a first array of lower-band radiating elements, each of the lower-band radiating elements in the first array of lower-band radiating elements coupled to the first RF port, and wherein the lower-band radiating elements in the second column and at least a second additional lower-band radiating element form a second array of lower-band radiating elements, each of the lower-band radiating elements in the second array of lower-band radiating elements coupled to the second RF port, wherein a first of the lower-band radiating elements includes first and second dipole radiators and a director mounted forwardly of the first and second dipole radiators, wherein both the first and second dipole radiators and the director are cloaked using resonant circuits to reduce or eliminate scattering of RF energy emitted by the higher-band radiating elements.
14 . The base station antenna of claim 13 , wherein the first additional lower-band radiating element is closer to a second vertical axis defined by the second column of lower-band radiating elements than it is a first vertical axis defined by the first column of lower-band radiating elements, and the second additional lower-band radiating element is closer to the first vertical axis than it is the second vertical axis.
15 . The base station antenna of claim 13 , wherein the first additional lower-band radiating element is positioned above or below the second column of lower-band radiating elements, and the second additional lower-band radiating element is positioned above or below the first column of lower-band radiating elements.
16 . The base station antenna of claim 13 , wherein the first additional lower-band radiating element is aligned along the second vertical axis, and the second additional lower-band radiating element is aligned along the first vertical axis.
17 . The base station antenna of claim 13 , wherein the first additional lower-band radiating element is fed substantially in antiphase with respect to the lower-band radiating elements in the first column.
18 . The base station antenna of claim 17 , wherein the first array of lower-band radiating elements is an L-shaped array of radiating elements.
19 . The base station antenna of claim 17 , wherein the first array of lower-band radiating elements is a Y-shaped array of radiating elements.
20 . The base station antenna of claim 17 , wherein the first additional lower-band radiating element is rotated 180° with respect to the lower-band radiating elements in the first column.

Description

CROSS-REFERENCE TO RELATED APPLICATION The present application is a 35 U.S.C. § 371 national stage application of PCT Application No. PCT/CN2022/076395, filed on Feb. 16, 2022, the disclosure of which is hereby incorporated herein in its entirety as if set forth fully herein. FIELD The present invention relates to radio communications and, more particularly, to base station antennas for cellular communications. BACKGROUND Cellular communications systems are well known in the art. In a typical cellular communications system, a geographic area is divided into a series of regions that are referred to as “cells,” and each cell is served by a base station. The base station may include baseband equipment, radios and base station antennas that are configured to provide two-way radio frequency (“RF”) communications with subscribers that are positioned throughout the cell. In many cases, the cell may be divided into a plurality of “sectors,” and separate base station antennas (which may be referred to as “sector” base station antennas) provide coverage to each of the sectors. The base station antennas are often mounted on a tower, with the radiation beam (“antenna beam”) that is generated by each base station antenna directed outwardly to serve a respective sector. Typically, a base station antenna includes one or more phase-controlled arrays of radiating elements, with the radiating elements arranged in one or more vertical columns when the antenna is mounted for use. Herein, “vertical” refers to a direction that is perpendicular the plane defined by the horizon. Reference will also be made to the azimuth plane, which is a plane that bisects the base station antenna that is parallel to the plane defined by the horizon, and to the elevation plane, which is a plane extending along the boresight pointing direction of the antenna that is perpendicular to the azimuth plane. A very common base station configuration is a so-called “three sector” configuration in which the cell is divided into three 120° sectors in the azimuth plane. A sector base station antenna is provided for each sector. In a three sector configuration, the antenna beams generated by each base station antenna typically have a Half Power Beamwidth (“HPBW”) in the azimuth plane of about 65° so that the antenna beams provide good coverage throughout a 120° sector. Three of these base station antennas will therefore provide full 360° coverage in the azimuth plane. Typically, each base station antenna will include a so-called linear array of radiating elements that includes a plurality of radiating elements that are arranged in a vertically-extending column. Each radiating element may have a HPBW of approximately 65°. By providing a column of radiating elements extending along the elevation plane, the elevation HPBW of the antenna beam may be narrowed to be significantly less than 65°, with the amount of narrowing increasing with the length of the column in the vertical direction. As demand for cellular service has grown, cellular operators have upgraded their networks to increase capacity and to support new generations of service. When these new services are introduced, the existing “legacy” services typically must be maintained to support legacy mobile devices. Thus, as new services are introduced, either new cellular base stations must be deployed or existing cellular base stations must be upgraded to support the new services. In order to reduce cost, many cellular base stations support two, three, four or more different types or generations of cellular service. However, due to local zoning ordinances and/or weight and wind loading constraints, there is often a limit as to the number of base station antennas that can be deployed at a given base station. To reduce the number of antennas, many operators deploy antennas that communicate in multiple frequency bands to support multiple different cellular services. There is considerable interest in base station antennas that include two linear arrays of “low-band” radiating elements that are used to support service in some or all of the 617-960 MHz frequency band. The antenna beams generated by such low-band linear arrays tend to penetrate buildings and other structures much more readily than arrays of radiating elements that operate in higher cellular frequency bands, and hence low-band service may be very important for providing high quality service. Base station antennas that include two low-band linear arrays typically also include at least two additional linear arrays of “mid-band” radiating elements that are used to provide service in some or all of the 1427-2690 MHz frequency band, and may also include one or more multi-column arrays of radiating elements that operate in the higher portion of the mid-band frequency range (e.g., the 2.3-2.7 GHz frequency range) or in a portion of the 3.2-5.8 GHz “high-band” frequency range. FIG. 1 is a schematic front view of a conventional base station antenna 10 (with