The present invention relates generally to wireless communications, and in particular embodiments, to a mixed structure dual-band dual-beam three-column phased array antenna.
Modern day wireless cellular antennas may emit a single or multiple beam signal. Single beam antennas emit a single beam signal pointing at the bore-sight direction of the antenna, while dual-beam antennas emit two asymmetric beam signals pointing in two different directions in opposite offset angles from the mechanical boresight of the antennas. In a fixed coverage cellular network, azimuth beam patterns of a dual-beam antenna are narrower than that of a single beam antenna. For example, a dual-beam antenna may emit two beams having a half power beam width (HPBW) of about thirty-three degrees in the azimuth direction, while a single beam antenna may emit one beam having a (HPBW) of about sixty-five degrees in the azimuth direction. The two narrow beams emitted by the dual-beam antenna may typically point in offset azimuth directions, e.g., plus and minus twenty degrees to minimize the beam coupling factor between the two beams and to provide 65 deg HPBW coverage in a three-sector network.
Technical advantages are generally achieved, by embodiments of this disclosure which describe a mixed structure dual-band dual-beam three-column phased array antenna.
In accordance with an embodiment, a dual-band radiating element is provided. In this example, the dual-band radiating element comprises an antenna reflector, a low-band radiating patch mounted to the antenna reflector, and a high-band radiating patch positioned above the low-band radiating patch.
In accordance with an embodiment, a dual-band antenna is provided. In this example, the dual-band antenna comprises a plurality of single-band antenna elements configured to radiate in a first frequency band, and a plurality of dual-band antenna elements configured to radiate in both the first frequency band and a second frequency band. The single-band antenna elements and the dual-band antenna elements are arranged in a three-column array of radiating elements.
In accordance with another embodiment, a method for operating a three-by-two (3×2) azimuth beam forming network (AFBN) is provided. In this example, the method comprises receiving a left-hand beam and a right-hand beam, applying a first phase shift to a duplicate of the left-hand beam to obtain a phase-shifted left-hand beam, applying a second phase shift to a duplicate of the right-hand beam to obtain a phase-shifted right-hand beam, mixing the right-hand beam with the phase shifted left-hand beam to obtain a first mixed signal, mixing the left-hand beam with the phase shifted right-hand beam to obtain a second mixed signal, mixing a duplicate of the first mixed signal and a duplicate of the second mixed signal to obtain a third mixed signal, and transmitting the first mixed signal, the second mixed signal, and the third mixed signal over an antenna array.
In accordance with yet another embodiment, an apparatus comprising a three-by-two (3×2) azimuth beam forming network (AFBN) structure is provided. In this example, the 3×2 AFBN structure is configured to receive a left-hand beam and a right-hand beam, to apply a first phase shift to a duplicate of the left-hand beam to obtain a phase-shifted left-hand beam, and to apply a second phase shift to a duplicate of the right-hand beam to obtain a phase-shifted right-hand beam. The 3×2 AFBN structure is further configured to mix the right-hand beam with the phase shifted left-hand beam to obtain a first mixed signal, to mix the left-hand beam with the phase shifted right-hand beam to obtain a second mixed signal, and to mix a duplicate of the first mixed signal and a duplicate of the second mixed signal to obtain a third mixed signal. The 3×2 AFBN structure is further configured to transmit the first mixed signal, the second mixed signal, and the third mixed signal over an antenna array.
For a more complete understanding of the present disclosure, and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:
Corresponding numerals and symbols in the different figures generally refer to corresponding parts unless otherwise indicated. The figures are drawn to clearly illustrate the relevant aspects of the embodiments and are not necessarily drawn to scale.
The making and using of embodiments of this disclosure are discussed in detail below. It should be appreciated, however, that the concepts disclosed herein can be embodied in a wide variety of specific contexts, and that the specific embodiments discussed herein are merely illustrative and do not serve to limit the scope of the claims. Further, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of this disclosure as defined by the appended claims.
Base station antennas are often mounted in high traffic metropolitan areas, and consequently compact modules are typically desired as they tend to be more aesthetically pleasing (e.g., less-noticeable) as well as easier to install and service. Moreover, base station antennas often use arrays of antenna elements in order to achieve enhanced spatial selectivity (e.g., through beamforming) as well as higher spectral efficiency. Concepts for creating three-column single-beam antenna arrays are discussed in U.S. patent application Ser. No. 12/175,425, which is incorporated by reference herein as if reproduced in its entirety. However, those concepts are inappropriate for dual-beam applications. Accordingly, mechanisms and architectures for providing a three-column antenna array capable of dual-beam functionality are desired.
Aspects of this disclosure provide a dual-band antenna element that can be used to construct a dual-beam three-column antenna array. More specifically, the dual-band antenna element includes both a high-band and a low-band radiating element, which allows it to radiate signals in two frequency bands. The dual-band antenna element also includes a resonating box to isolate the co-located radiating elements from one another, and mitigate inter-band distortion. Additional aspects of this disclosure provide additional features for constructing the dual-band antenna element, as well as features for constructing the dual-beam three-column array.
Aspects of this disclosure provide a dual-band radiating element that is configured to operate in two distinct frequency bands.
The embodiment dual-band radiating element configurations provided herein allow for a three-column dual-beam antenna array to be achieved.
Aspects of this disclosure provide an apparatus for Azimuth antenna beam patterns that can be advantageously modified by varying amplitude and phase of RF signals applied to respective radiating elements in the azimuth direction. Many modern day cellular base-station antennas are designed to have a single main lobe with azimuth radiation half-power beam-width (HPBW) of 65 degrees or 90 degrees. Aspects of this disclosure introduce a three-column dual-band dual-beam antenna for high-capacity cellular operations. The proposed dual-band dual-beam antenna array produces two highly orthogonal spatial beams in two or more frequency bands using a common antenna aperture. Therefore, as an example, a total of four orthogonal azimuth beams, each with thirty-three degrees half-power beam width (HPBW), can be produced in a single dual-band dual-beam per signal polarization, as compared to only two beams by a standard sixty-five degrees dual-band array.
Aspects of this disclosure provide a methodology for fabrication of a commercially viable dual-band dual-beam array using interleaving three-column antenna array structures. Some embodiments make use of mixed configurations of three-column linear arrays to form the dual-beam array which results in improved aperture efficiency with less inter-band interference as compared to other array configurations. Embodiment antenna arrays produce four isolated asymmetric beams in the azimuth direction in two closely spaced frequency bands, e.g., one in the Universal Mobile Telecommunications System (UMTS) band (1710 MHz to 2170 MHz) and the other in a slightly higher frequency band of long term evolution (LTE) 2.5 GHz (2500 MHz to 2700 MHz). Two three-column arrays include a plurality of radiating elements operating in two separate frequency bands that are arranged in an interleaving fashion to allow proper radiations of a signal in two frequency bands. The radiating elements for the lower frequency three-column array may be arranged in staggered array configuration, while the radiating elements for the higher frequency band takes a rectangular three-column array structure in order to achieve the increased aperture efficiency with improved azimuth beam patterns and reduced inter-band interference between the two bands. Tailor made non-Butler, non-uniform 3×2 azimuth beam forming network (ABFN) are provided for satisfying the relatively complex excitations for these multi-column arrays. The ABFN circuitry may be formed such that all the orthogonal beams can operate simultaneously with low beam coupling factor, which may be beneficial for reducing network interference. In addition to the delivery of accurate amplitudes and phases to radiators, the positioning of the radiating elements may also be helpful for improving the overall beam patterns. To achieve compact size, in dual-band array structures, radiating elements of both bands sometimes occupy the same space. In this case, the high-band patch must be stacked on top of a low-band element to form a new dual-band element which allows simultaneous radiation of signals in both bands.
An embodiment of this disclosure provides an antenna array comprising a plurality of radiating elements arranged to form a plurality of columns, each column comprising at least one radiating element, each radiating element operating in at least one of a plurality of non-overlapping frequency bands, wherein within said at least one operating frequency band, each radiating element is configurable to produce a plurality of radiation beams, wherein at least one of the radiation beams is asymmetrical.
Aspects of this disclosure introduce the concept of a mixed-structure three-column antenna arrays architecture, containing a plurality of driven radiating elements that are spatially interleaved between two different types of radiating elements operating in two separate frequency bands. For each frequency band of operation, two slightly overlapping asymmetric beams with extremely low beam coupling factor are produced in the azimuth plane to provide optimum wireless cellular performance. To achieve proper dual-band operations, a new dual-band patch is also introduced here to allow simultaneous operation of the two independent arrays.
Aspects of this disclosure achieve patterns having a high roll-off rate at points in which the two component beams intersect, low azimuth sidelobes, beam cross-over from −5 dB to −9 dB between the patterns, front to back ratio of typically over 30 dB in the back of the antenna. Through the virtue of orthogonality of the BFN and spectrum isolation between the two bands, the four asymmetric beams produced by the dual-band BSA are inherently isolated. Therefore, aspects of this disclosure significantly improve network performances without having the penalty of increasing the overall size of a base-station antenna.
Aspects of this disclosure provide dual-band radiating elements. Embodiment radiating elements may use broadband stacked patch radiators, which provide relatively good broadband characteristics and produce highly polarized fields with relatively simple feed system. Aspects of this disclosure introduce a new type of dual-band patch element which allows for the radiation of signals in both bands with minimum interference between bands.
Embodiments of this disclosure provide a dual-band microstrip feed assembly to allow proper feeding of dual-polarized high-band RF signals from the bottom of the dual-band element.
Aspects of this disclosure provide a 3×2 Azimuth Beam Forming Network. This may include a non-Butler, non-uniform azimuth beam forming network (ABFN). A Butler matrix may be used in forming a 2N multi-beam array, where N is an integer number. In this case, the array may include a non-binary number of columns, e.g., the number of columns ≠2N. A non-Butler ABFN is developed for the three-column array to produce the desired dual-beam patterns with relatively good orthogonality between the component beams. For example, 3×2 ABFNs may be used to form a 3×10 low-band array and a 3×20 high-band array.
Although the description has been described in detail, it should be understood that various changes, substitutions and alterations can be made without departing from the spirit and scope of this disclosure as defined by the appended claims. Moreover, the scope of the disclosure is not intended to be limited to the particular embodiments described herein, as one of ordinary skill in the art will readily appreciate from this disclosure that processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed, may perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.
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