US-12627034-B2 - Beamforming antennas with omnidirectional coverage in the azimuth plane

US12627034B2US 12627034 B2US12627034 B2US 12627034B2US-12627034-B2

Abstract

A base station antenna includes a plurality of pairs of RF ports, a tubular reflector, a plurality of columns of first frequency band radiating elements that are mounted to extend outwardly from the tubular reflector, the columns extending around a periphery of the tubular reflector and grouped into a plurality of column groups, where each column group includes at least three columns, and a plurality of feed networks, where each feed network connects one of the pairs of RF ports to a respective one of the column groups.

Inventors

XiaoHua Hou
Peter Bisiules
Sammit Patel
Ligang Wu
Haifeng Li

Assignees

Outdoor Wireless Networks LLC

Dates

Publication Date: 20260512
Application Date: 20220125
Priority Date: 20210201

Claims (14)

1 . A base station antenna, comprising: a plurality of pairs of radio frequency (“RF”) ports; a tubular reflector; a plurality of columns of first frequency band radiating elements that are mounted to extend outwardly from the tubular reflector, the columns extending around a periphery of the tubular reflector and grouped into a plurality of column groups, where each column group includes at least two columns; a first feed network that connects both of the RF ports in a first of the plurality of pairs of RF ports to each column in a first of the column groups; and a second feed network that connects both of the RF ports in a second of the plurality of pairs of RF ports to each column in a second of the column groups; wherein the plurality of column groups are configured to generate sector antenna beams that provide coverage to respective ones of a plurality of sectors.
2 . The base station antenna of claim 1 , wherein the tubular reflector includes a plurality of flat faces.
3 . The base station antenna of claim 2 , wherein each pair of adjacent flat faces define a respective angle within an interior of the tubular reflector, and the sum of the angles defined by the pairs of adjacent faces is equal to 360°.
4 . The base station antenna of claim 1 , wherein the column groups are arranged in pairs, and each pair of column groups is configured to be coupled to a respective one of a plurality of four-port radios.
5 . The base station antenna of claim 4 , wherein the first column group of each pair of column groups is configured to be coupled to first and second ports of the respective one of the four-port radios, and the second column group of each pair of column groups is configured to be coupled to third and fourth ports of the respective one of the four-port radios.
6 . The base station antenna of claim 4 in combination with the plurality of four-port radios, wherein each four-port radio is configured to support four-input-four-output multi-input-multi-output (“MIMO”) communications through a respective pair of adjacent column groups.
7 . The base station antenna of claim 1 , wherein the plurality of columns of first frequency band radiating elements comprises at least twelve columns of first frequency band radiating elements.
8 . The base station antenna of claim 1 , wherein the plurality of columns of first frequency band radiating elements comprises eighteen columns of first frequency band radiating elements that are divided into six column groups having three columns of first frequency band radiating elements each, wherein each column group is configured to provide coverage to a 60° sector in an azimuth plane.
9 . The base station antenna of claim 1 , further comprising a plurality of radios that are mounted within a center of the tubular reflector.
10 . The base station antenna of claim 9 , wherein each radio includes a plurality of inwardly extending heat fins that are configured to contact a pole on which the base station antenna is mounted.
11 . The base station antenna of claim 1 , wherein each feed network includes first and second phase shifters for each column of first frequency band radiating elements, and wherein a single respective remote electronic tilt actuator is provided to adjust the phase shifters associated with the columns of first frequency band radiating elements included in each column group.
12 . The base station antenna of claim 1 , wherein the tubular reflector has a substantially circular cross-section.
13 . The base station antenna of claim 1 , wherein the plurality of columns of first frequency band radiating elements comprises twenty-four columns of first frequency band radiating elements that are divided into eight column groups having three columns of first frequency band radiating elements each, wherein each column group is configured to provide coverage to a 45° sector in an azimuth plane.
14 . The base station antenna of claim 1 , wherein adjacent columns are spaced apart by less than 0.6 of a wavelength that corresponds to a center frequency of the first frequency band.

Description

RELATED APPLICATION The present application is a 35 U.S.C. § 371 national phase application of PCT Application PCT/US2022/013591, filed Jan. 25, 2022, which claims priority to Chinese Patent Application No. 202110135752.9, filed Feb. 1, 2021, the entire content of each of which is incorporated herein by reference. FIELD The present invention relates to cellular communications systems and, more particularly, to base station antennas that provide omnidirectional coverage in the azimuth plane. 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. Typically, a cell may serve users who are within a distance of, for example, 2-20 kilometers from the base station, although smaller cells are typically used in urban areas to increase capacity. The base station may include baseband equipment, radios and antennas that are configured to provide two-way radio frequency (“RF”) communications with mobile 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 provide coverage to each of the sectors. The base station antennas are often mounted on a tower or other raised structure, with the radiation beam (“antenna beam”) that is generated by each 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 relative to the plane defined by the horizon. The base station antenna may include a small mechanical downtilt (e.g. 1-10°), and hence it will be appreciated that the columns generally extend vertically as opposed to always being exactly perpendicular to the plane defined by the horizon. In order to increase capacity, cellular operators have, in recent years, been deploying base stations that provide coverage to smaller cells than conventional “macrocell” base stations. Base stations having reduced coverage areas are referred to using a variety of different names including small cell base stations, metrocell base stations, picocell base stations and the like. Herein, the term “small cell” will be used to refer to these smaller base stations and their associated antennas. Generally speaking, a small cell base station refers to a low-power base station that may operate in the licensed and/or unlicensed spectrum that has a much smaller range than a typical “macrocell” base station. A small cell base station may be designed to serve subscribers who are within short distances from the small cell base station (e.g., tens or hundreds of meters). Small cells may be used, for example, to provide cellular coverage to high traffic areas within a macrocell, which allows the macrocell base station to offload much or all of the traffic in the vicinity of the small cell to the small cell base station. Small cells may be particularly effective in Long Term Evolution (“LTE”) cellular networks in efficiently using the available frequency spectrum to maximize network capacity at a reasonable cost. Small cell base stations typically employ an antenna that provides full 360 degree or “omnidirectional” coverage in the azimuth plane and a suitable beamwidth in the elevation plane to cover the designed area of the small cell. With the introduction of various fourth generation (“4G”) and fifth generation (“5G”) cellular technologies, small cell base station antennas have been deployed that have multi-input-multi-output (“MIMO”) capabilities. As known to those of skill in the art, MIMO refers to a technique where a baseband data stream is sub-divided into multiple sub-streams that are used to generate multiple RF signals that are transmitted through multiple different antenna arrays. The antenna arrays are, for example, spatially separated from one another and/or at orthogonal polarizations so that the transmitted RF signals will be sufficiently decorrelated. The multiple RF signals are recovered at the receiver and demodulated and decoded to recover the original data sub-streams, which are then recombined. The use of MIMO transmission techniques may help overcome the negative effects of multipath fading, and may be particularly effective in urban environments where reflections of the transmitted RF signals may increase the level of decorrelation between the transmitted RF signals. FIG. 1A is a schematic diagram illustrating one conventional implementation of a small cell base station 10. As shown in FIG. 1A, the base station 10 includes three base station antennas 20-1, 20-2, 20-3 that are mounted on a raised structure (e.g., a light pole), with each antenna 20 pointing outwardly. Herein multiple