US-12620725-B2 - Low cost high performance multiband cellular antenna with cloaked monolithic metal dipole

US12620725B2US 12620725 B2US12620725 B2US 12620725B2US-12620725-B2

Abstract

Disclosed is a high performance low cost multiband antenna configuration that has a low band dipole having dipole arms formed of stamped sheet metal with a plurality of inductor structures. The plurality of inductor structures are oriented along a longitudinal axis of the low band dipole arm, and others are oriented orthogonal to the longitudinal axis. The plurality of the inductor structures act as cloaking structures that make the low band dipole substantially transparent to high band RF energy without inhibiting the performance of the dipole in the low band.

Inventors

Niranjan Sundararajan
CHARLES BUONDELMONTE
Andrew LITTEER
Wengang Chen

Assignees

John Mezzalingua Associates, LLC

Dates

Publication Date: 20260505
Application Date: 20231215

Claims (8)

1 . A dipole, comprising: four identical dipole arms arranged in a cross pattern, whereby each of the four identical dipole arms is formed of a single piece of metal, whereby the four identical dipole arms have a first dipole arm pair arranged opposite each other, and a second dipole arm pair arranged opposite each other, whereby the first dipole arm pair are configured to radiate a first RF (Radio Frequency) signal and the second dipole arm pair are configured to radiate a second RF signal; a first balun stem plate that is mechanically and electrically coupled to the first dipole arm pair; and a second balun stem plate that is mechanically and electrically coupled to the second dipole arm pair, wherein the first balun stem plate and the second balun stem plate are mechanically coupled in a cross pattern, and wherein each of the four identical dipole arms comprise a plurality of slot-shaped holes, and wherein the plurality of slot-shaped holes comprises on-axis slots and orthogonal slots.
2 . The dipole of claim 1 , wherein each dipole arm comprises a balun connection point.
3 . The dipole of claim 2 , wherein the balun connection point comprises a slot in the dipole arm.
4 . The dipole of claim 1 , further comprising a pedestal having four pedestal fasteners.
5 . The dipole of claim 4 , wherein each of the four identical dipole arms comprises a fastener insertion slot mechanically coupled to a corresponding pedestal fastener.
6 . The dipole of claim 1 , wherein each of the four identical dipole arms comprises a plurality of inductor structures.
7 . The dipole of claim 1 , wherein each of the four identical dipole arms is stamped from a single piece of metal.
8 . The dipole of claim 7 , wherein the single piece of metal comprises one of aluminum, sheet metal, and brass.

Description

This application is a Continuation of application Ser. No. 17/494,329, filed Oct. 5, 2021, which is a Continuation of application Ser. No. 16/758,094, filed Apr. 22, 2020, now U.S. Pat. No. 11,145,994, which is a 371 National Stage Application of PCT/US2018/057453, filed Oct. 25, 2018, expired, which claims the benefit of U.S. Provisional Patent Application Ser. No. 62/577,407, filed Oct. 26, 2017, expired, which applications are hereby incorporated by this reference in their entireties for all purposes as if fully set forth herein. BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to antennas for wireless communications, and more particularly, to multiband antennas that have low band and high band dipoles located in close proximity. Related Art There is considerable demand for cellular antennas that can operate in multiple bands and at multiple orthogonal polarization states to make the most use of antenna diversity. A solution to this is to have an antenna that operates in two orthogonal polarization states in the low band (LB) (e.g., 698-960 MHz) and in two orthogonal polarization states in the high band (HB) (e.g., 1.695-2.7 GHZ). A typical set of orthogonal polarization states includes +/−45 deg. There is further demand for the antenna to have minimal wind loading, which means that it must be as narrow as possible to present a minimal cross sectional area to oncoming wind. Another demand is for an antenna to have a fast rolloff gain pattern in both the High Band (HB) and Low Band (LB) to mitigate inter-sector interference. Conventional antennas have gain patterns with considerable side and rear lobes. These antennas are typically mounted on a single cell tower, each covering a different sector, which results in the side and rear lobes of their respective gain patterns overlapping, causing interference in the overlapping gain regions. Therefore it is desirable for an antenna to have a fast-rolloff gain pattern, whereby beyond a given angle (e.g., 45° or 60°), the antenna gain pattern falls off rapidly, thereby minimizing overlapping gain patterns between multiple sector antennas mounted on a single cell tower. Further, interference between the LB and HB dipoles can contaminate their respective gain patterns, thus degrading the performance of the antenna. The need for both a compact array face and a fast rolloff gain pattern causes a conflict in objectives because the best way to achieve a fast rolloff gain pattern is to broaden the array face of the antenna, and broadening the antenna array face increases wind loading. Conversely, the more closely LB and HB dipoles are spaced together on a single array face, the more they suffer from interference whereby transmission in either the HB or the LB is respectively picked up by the LB and HB dipoles, causing coupling and re-radiation that contaminates the gain pattern of the transmitting band. This problem can be solved with dipoles that are designed to be “cloaked”, whereby they radiate and receive in the band for which they are designed yet are transparent to the other band that is radiated by the other dipoles sharing the same compact array face. Cloaked dipoles are typically divided into conductive segments that are coupled by intervening inductor and/or capacitor structures. The conductive segments have a length that is less than one half wavelength of the RF energy (cloaked wavelength) for which induced current is to be prevented. The inductor and/or capacitor structures are tuned so that they resonate at and above this cloaked wavelength, being substantially open circuited above the cloaked wavelength and substantially short circuited below the cloaked wavelength. LB dipoles are typically cloaked to prevent HB induced current from occurring in the LB dipole conductors. Otherwise, HB energy emitted by the HB dipole would induce a current in the LB dipole, which would subsequently re-radiate and interfere with the HB gain pattern. As mentioned above, cloaked dipole structures involve inductors and/or capacitors located between conductive elements within the dipole arm. These structures may be complex and require additional PCB and metal layers, adhesives, and ancillary components that must be attached to or integrated into the dipole structure. As such, cloaked dipoles can be complicated, expensive and time consuming to manufacture, and may incur reliability issues. Accordingly, there is a need for a multiband antenna, with a minimal array face but with strong multiband performance (e.g., clean gain patters with minimal interference and fast rolloff), and that has LB dipoles that are simple and easy to manufacture. SUMMARY OF THE INVENTION Accordingly, the present invention is directed to a low cost high performance multiband cellular antenna with cloaked monolithic metal dipole that obviates one or more of the problems due to limitations and disadvantages of the related art. In an aspect of the present invention, a multiba