Dual Band Interleaved Phased Array Antenna

The height of crossed-dipoles antenna elements can be reduced by including an additional bend/segment in the feed-line and/or tuning-stub of the antenna dipole having the upper slot. The extra bend allows the crossed-dipoles antenna element to be shortened by as much as twenty percent without reducing the feed-line length. Additionally, the height of crossed-dipoles antenna elements can be reduced by shaping a winged portion of the balun-fed dipoles to match the contour of a radome contour, which allows the crossed-dipoles antenna element to accommodate a shallower radome and achieve a thinner antenna module. Additionally, the height of crossed-dipoles antenna elements can be reduced by positioning periodic structures around the base of low-band radiating elements to provide artificial magnetic conductor (AMC) functionality, which enables constructive interference between reflected and non-reflected signals at profile spacings of less than one-quarter wavelength.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

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.

Portions of this disclosure relate to crossed-dipoles antenna element architectures, which typically include a pair of balun-fed dipoles having one antenna dipole with an upper slot and another antenna dipole with a lower slot. The slots allow the respective dipoles to be mounted perpendicularly to one another by sliding the lower slot over the upper slot such that the respective slots intersect.

Aspects of this disclosure provide techniques for reducing the height of crossed-dipoles antenna elements, which may allow for thinner base station antenna modules as well as provide a larger housing for active antenna circuitry. In one embodiment, an additional bend/segment is included in the feed-line and/or tuning-stub of the antenna dipole having the upper slot to allow the length of that feed-line/tuning-stub to be maintained when the height of the crossed-dipoles antenna element is reduced. Indeed, the extra bend allows the crossed-dipoles antenna element to be shortened by as much as twenty percent without reducing the feed-line length. Another embodiment conforms the winged portion of the balun-fed dipoles to match the radome's contour, which allows the crossed-dipoles antenna element to accommodate a shallower radome and achieve a thinner antenna module. In yet another embodiment, periodic structures are positioned at the base of radiating elements to provide artificial magnetic conductor (AMC) functionality. The AMC functionality enables constructive interference between reflected and non-reflected signals to be achieved at profile spacings of less than one-quarter wavelength, thereby allowing for thinner base station antennas. The periodic structures also provide an electromagnetic band gap (EBG) function for improved isolation between radiating elements.

Additional aspects of this disclosure provide techniques for achieving improved crossed-dipoles antenna element performance. In one embodiment, improved return loss bandwidth is achieved by including an additional conductive layer above the feed-line on the winged portion of the balun-fed dipoles. In another embodiment, the bottom most edges of the conductive layer are notched to provide a more reliable conductive interconnection between the conductive layer and the ground plane.

Aspects of this disclosure also provide techniques for improving the performance of interleaved antenna arrays. One such technique utilizes non-uniform spacings between high and low-band radiating elements to increase inter-band isolation, as well as to reduce the grating lobe effect and mitigate beam-narrowing/dispersion that results from fixed element spacings. The non-uniform spacings may include wider spacings between low-band radiating elements than between high-band radiating elements. Another such technique utilizes conductive fences positioned in-between horizontally adjacent columns of radiating elements to provide increased intra-band isolation. The central fences may include voids to prevent the propagation of unwanted modes. Additionally, edge fences may be positioned on either side of the array to reduce front to back radiation.

FIG. 1illustrates a network100for communicating data. The network100comprises an access point (AP)110having a coverage area112, a plurality of user equipments (UEs)120, and a backhaul network130. The AP110may comprise any component capable of providing wireless access by, inter alia, establishing uplink (dashed line) and/or downlink (dotted line) connections with the UEs120, such as a base station, an enhanced base station (eNB), a femtocell, and other wirelessly enabled devices. The UEs120may comprise any component capable of establishing a wireless connection with the AP110. The backhaul network130may be any component or collection of components that allow data to be exchanged between the AP110and a remote end (not shown). In some embodiments, the network100may comprise various other wireless devices, such as relays, femtocells, etc.

FIG. 2illustrates a conventional base station antenna200for performing wireless communications. As shown, the conventional base station antenna200comprises crossed-dipoles antenna elements210, a radome220, and an antenna reflector225. The crossed-dipoles antenna elements210are mounted to the antenna reflector225, and the radome220encases the crossed-dipoles antenna elements210to shield them from the environment. The conventional base station antenna200further includes a compartment230for housing active antenna components. The height (H1) of the conventional base station antenna200depends largely on the height (h1) of the traditional crossed-dipoles antenna elements210as well as on the depth (d1) of the compartment230. Accordingly, the height (H1) of the conventional base station antenna200may be reduced by either reducing the height (h1) of the traditional crossed-dipoles antenna elements210, or by reducing the depth (d1) of the compartment230. However, reducing the depth (d1) of the compartment230may require implementing less-advanced active antenna components (e.g., due to space restrictions), and therefore may restrict the performance of the conventional base station antenna200. Accordingly, techniques for reducing the height (h1) of the traditional crossed-dipoles antenna elements210are desired.

Aspects of this disclosure provide techniques for reducing the height of crossed-dipoles antennas.FIG. 3illustrates an embodiment base station antenna300for performing wireless communications. As shown, the embodiment base station antenna300comprises embodiment crossed-dipoles antenna elements310, a radome320, and an antenna reflector325. The radome320and the antenna reflector325may be configured similarly to the radome220and the antenna reflector225. Further, the crossed-dipoles antenna elements310may radiate at similar frequencies to the crossed-dipoles antenna elements210. However, aspects of this disclosure allow a height (h2) of the crossed-dipoles antenna elements310to be less than the height (h1) of the crossed-dipoles antenna elements210without significantly affecting its performance characteristics. By way of example, the crossed-dipoles antenna elements310may exhibit an additional bend/segment in the feed-line and/or the tuning-stub to allow the overall length of the feed-line and/or tuning-stub to be maintained after reducing the height (h2) of the crossed-dipoles antenna elements310. As another example, the dipole arms of the crossed-dipoles antenna elements310may conform to a contour of the radome320. Aspects of this disclosure may also provide techniques for improving performance of crossed-dipoles antenna elements. For example, the crossed-dipoles antenna elements310may have an additional conductive layer on the feed-line side to improve return loss bandwidth.

FIGS. 4A-4Eillustrate a conventional crossed-dipoles antenna element400. As shown inFIG. 4A, the conventional crossed-dipoles antenna element400comprises a pair of balun-fed dipoles410,420. As shown inFIGS. 4B-4C, a front-side411of the balun-fed dipole410includes a feed-line412, while a rear-side415of the balun-fed dipole410includes a rear-side conductive layer416and a tuning-slot417. As shown inFIGS. 4D-4E, a front-side421of the balun-fed dipole420includes a feed-line422, while a rear-side425of the balun-fed dipole420includes a rear-side conductive layer426and a tuning-slot427. The balun-fed dipole410comprises a lower-cut slot413, while the balun-fed dipole420comprises an upper-cut slot423. The substrate-cut slots413,423allow the balun-fed dipoles410,420to be joined with one another to form the crossed-dipoles antenna element400.

Aspects of this disclosure provide several mechanisms for reducing the height of crossed-dipoles antenna elements, such as conforming the shapes of the dipole wings to the radome, and bending the feed-line and/or tuning-stub. Another aspect of this disclosure provides an additional conductive layer on the front-side (or feed-line side) of one or both of the balun-fed dipoles to achieve improved return loss bandwidth.FIGS. 5A-5Eillustrate an embodiment crossed-dipoles antenna element500comprising a pair of balun-fed dipoles510,520. Notably, the embodiment crossed-dipoles antenna element500is shorter than the conventional crossed-dipoles antenna element400, while still exhibiting similar performance characteristics, e.g., radiating frequency, etc. As shown inFIG. 5A, the embodiment crossed-dipoles antenna element500includes front-side conductive layers514,524as well as dipole wings that conform to a radome (not shown). As shown inFIGS. 5B-5C, a front-side511of the balun-fed dipole510includes a feed-line512and a front-side conductive layer514, while a rear-side515of the balun-fed dipole510includes a rear-side conductive layer516and a tuning-slot517. As shown inFIGS. 5D-5E, a front-side521of the balun-fed dipole520includes a feed-line522and a front-side conductive layer524, while a rear-side525of the balun-fed dipole520includes a rear-side conductive layer526and a tuning-bent-slot527. The balun-fed dipoles510,520include substrate-cut slots513,523that allow the balun-fed dipoles510,520to be joined with one another to form the crossed-dipoles antenna element500. The front-side conductive layers514and524allow the crossed-dipoles antenna element500to achieve improved return-loss bandwidth. Furthermore, as depicted inFIG. 5D, the feed-line522includes one more bend/segment than the feed-line512, thereby allowing the feed-line522to have additional length without extending off the edge of the balun-fed dipole's520substrate. Similarly, the tuning-stub527includes an extra bend/segment when compared to the tuning-stub517. To further decease the effective height of the crossed-dipoles antenna element500, the dipole wings are conformed to match (or resemble) the contour of a radome (not shown).

FIG. 6illustrates a plurality of embodiment dipole wing shapes610-690. Different dipole wing shapes may exhibit different performance characteristics. For example, a given dipole wing shape may be selected to match a termination/load of the dipole wings to the balun input. As another example, dipole wing shapes may be manipulated to widen or narrow the radiation frequency band of the base station antenna or to achieve a resonance level, e.g., single or dual resonance, etc. As another example, a dipole wing shape may be chosen to control current distribution on the dipole wing surface and/or to achieve various polarization patterns, e.g., co-polarization, cross-polarization, etc.

Additional aspects of this disclosure reduce the likelihood of intermodulation distortion in crossed-dipoles antenna elements by notching the ends of rear-side conductive layer. More specifically, intermodulation distortion may occur when a conductive interconnection or joint between a conductive layer and the ground plane (or antenna reflector) is non-contiguous, as may result from solder float during the manufacturing process. Aspects of this disclosure notch the bottom-most ends of the conductive layer to reduce the length (or surface area) of the conductive interconnection/joint between the conductive layer and the ground plane, thereby reducing the likelihood of conductivity gaps in that interconnection/joint.FIGS. 7A-7Eillustrate an embodiment crossed-dipoles antenna element700that includes a pair of balun-fed dipoles710,720. As shown inFIGS. 7B-7C, a front-side711of the balun-fed dipole710includes a feed-line712and a front-side conductive layer714, while a rear-side715of the balun-fed dipole710includes a rear-side conductive layer716. As shown inFIGS. 7D-7E, a front-side721of the balun-fed dipole720includes a feed-line722and a front-side conductive layer724, while a rear-side725of the balun-fed dipole720includes a rear-side conductive layer726. The rear-side conductive layers716,726include notched ends718,728(respectively) for bonding to the ground plane.

A multiband, phased-array antenna with an interleaved tapered-element and waveguide radiators is disclosed by U.S. Pat. No. 5,557,291, which is incorporated herein by reference as if reproduced in its entirety. In an array of elements with fixed locations, the characteristics of the radiated pattern vary with frequency. For instance, the main beam narrows and grating lobes appear as the frequency increases, and if a full-bandwidth element is used, the beam narrowing can be excessive. In addition, isolation between array input ports can be achieved with a diplexer, which introduces loss as well as expense and complexity. Coupling between adjacent elements decreases antenna isolation and is an indication that the element is being perturbed, e.g., there is a degraded individual element pattern in the array environment.

In an embodiment with two separate frequency bands, separate radiating elements are used for each band, with the respective elements being arranged with different spacings. For example, wider spacings may separate low-band elements, while narrower spacings may separate high-band elements. When compared to interleaved arrays having fixed/uniform element spacing, interleaved arrays having non-uniform element spacings may have better inter-band isolation, reduced grating lobe effects, and less beam narrowing/dispersion.FIG. 8illustrates an embodiment interleaved array803and an embodiment wideband array804. The embodiment interleaved array803is achieved by combining a low-band array801and a high-band array802. In an embodiment, periodic structures are placed at the base of the radiating elements. The periodic structures provide an electromagnetic band gap (EBG) function for the high-band as well as an artificial magnetic conductor (AMC) function for the low-band elements. The EBG function decreases coupling between high-band elements. The AMC function allows for constructive interference between reflected and non-reflected signals at profile spacings less than one quarter wavelength. This allows the low-band elements to be lowered to achieve a reduced base station antenna thickness. Embodiments may be implemented in wireless access networks and devices, such as access points, base stations, and the like.FIGS. 9A-9Billustrate different approaches to achieve port isolation.FIG. 9Aillustrates isolation for a full bandwidth element, andFIG. 9Billustrates isolation for an embodiment interleaved approach.

Embodiment dual-band interleaved array architectures may have ratios between the high-band and low-band frequencies of about 1.3:1 or 1.5:1, which is significantly less than the 2:1 ratio exhibited by conventional architectures. In various embodiments the frequency ratio may be between 2.0 and 1.9, between 1.9 and 1.8, between 1.8 and 1.7, between 1.7 and 1.6, between 1.6 and 1.5, between 1.5 and 1.4, between 1.4 and 1.3, between 1.3 and 1.2, or between 1.2 and 1.1. In other embodiments, the frequency ratio is less than one of these ratios and greater than about 1.1, greater than about 1.2, greater than 1.3, or greater than 1.4. Unlike with the frequency ratio of 2:1, which is conducive to co-locating some of the individual radiating elements of the two arrays, no individual radiating elements are co-located in various embodiments. In another embodiment, the frequency ratio is set at about 1:1, which basically is an implementation of two independent arrays on the same enclosure, which is useful for various applications.

An embodiment interleaving array provides well-controlled beam patterns that are useful in network planning and optimization, especially when operating over multiple bands. In an embodiment, inherent isolation between frequency bands relaxes or eliminates the need for multiple diplexers and the associated losses. An embodiment enables the implementation of two or more independent arrays in one enclosure. An embodiment provides small element size (droop dipoles+EBG), yielding a low-profile antenna. An embodiment provides low inter-element coupling (mutual coupling).

An embodiment uses separate elements for each of two frequency bands with independent spacings not multiples of one another, where the frequency bands are not multiple factors of one another. In one embodiment with 1800 MHz or 2100 MHz low-band and a 2690 MHz high-band, the, 2100 MHz low-band and the high-band are relatively close to one another. In an embodiment, different element spacings are used for low-band (e.g., 85 mm) and high-band (e.g., 63 mm), resulting in elements that are not co-located elements as well as an asymmetric array. This provides independent element spacing in each band. Selecting separate elements takes advantage of the isolation inherent between elements to increase the isolation between bands at the antenna input ports, thereby reducing filtering requirements.

An embodiment of this disclosure limits the effects of the closely-spaced elements on adjacent elements, which includes mutual coupling as well as perturbation of the individual element patterns. An embodiment is useful for relatively closely spaced frequency bands in the same antenna, with a ratio of about 1.3:1 or 1.5:1. Embodiment dipoles and feeding baluns are more compact with a lower profile.FIG. 10illustrates a graph of simulated azimuth antenna patterns, where an interleaved antenna avoids grating lobes and has less beam narrowing.FIG. 11illustrates an embodiment dual band array including interleaved high and low-band radiating elements as well as a periodic structure that performs electromagnetic band gap (EBG) functionality. Low-profile dipole elements include EBG and conductive fences. A power distribution network (e.g., cables, beam forming networks, phase shifters) is located behind the reflector. The array elements have a low profile, and low mutual coupling.FIG. 12illustrates the two interleaved arrays with 12-rows×4-columns for each array. There are eight input ports (with 50 ohms impedance).

FIG. 13illustrates a base station antenna1300comprising an interleaved array of low-band radiating elements1310and high-band radiating elements1320mounted on an antenna reflector1305. The base station antenna1300further comprises periodic structures1330, central conductive fences1340, and edge fences1350. The periodic structures1330are arranged around the base of the low-band radiating elements1310and the high-band radiating elements1320, and are configured to provide Artificial Magnetic Conductor (AMC) functionality to the low-band radiating elements1310and EBG functionality to the high-band radiating elements1320. The central conductive fences1340are positioned in-between columns of low-band radiating elements1310, and are configured to reduce mutual coupling between horizontally adjacent low-band radiating elements as well as to reduce mutual coupling between horizontally adjacent high-band radiating elements. The central conductive fences1340include conductive segments1341,1342separated by a void1343. The void1343may prevent unwanted modes from propagating between the conductive segments1341,1342. The edge fences1350may run contiguously along the vertical length of the antenna reflector1305, and may be substantially free of voids. The edge fences1350may prevent radiated signals from leaking behind the antenna reflector1305.

In some embodiments, the low-band radiating elements1310have crossed-dipoles arms with non-uniform widths, while the high-band radiating elements1320may have crossed-dipole arms with uniform widths. The characteristics/properties of the periodic structures1330can be manipulated/selected to achieve constructive interference for different low-band element profiles. In some embodiments, the periodic structures1330cover the entire surface of the antenna reflector1305. The antenna reflector1305may provide the ground plane. Edge fences1350may improve the front to back radiation ratio. Central conductive fences1340provide a finite number of fence segments1341,1342along the reflector, and may improve the radiation pattern as well as reduce coupling between horizontally adjacent rows of elements.

FIG. 14illustrates a radiating element configuration1400comprising a plurality of periodic structures1430and a low-band radiating element affixed to an antenna reflector1405. The periodic structures1430are positioned around the base of a low-band radiating element1410and are configured to provide AMC functionality by reflecting signals emitted from the low-band radiating element1410in a manner that causes the reflected signals to constructively interfere with the non-reflected signals. Indeed, the AMC functionality may provide constructive interference when a profile of the low-band radiating element1410is less than or equal to one-quarter of the low-band signal's wavelength. The term “profile” refers to a vertical separation or distance between the dipole arms and the ground plane (or antenna reflector).

The periodic structures1430achieve the AMC functionality by applying a different phase shift than would otherwise have been applied by the antenna reflector. For instance, the antenna reflector may typically apply a λ/2 phase shift to reflected signals, thereby causing the reflected signals to destructively interfere with non-reflected signals when a profile is less than λ/4. Conversely, the periodic structures1430may apply a substantially smaller phase shift (e.g., a zero degrees phase shift) to the reflected signals, thereby providing constructive interference for profiles less than or equal to one-quarter of the low-band signal's wavelength.FIG. 15illustrates a diagram for obtaining constructive interference in a conventional dipole configuration1500. As shown, the conventional configuration1501requires a profile distance (d) between the dipole and the ground plane (e.g., an antenna reflector) in excess of λ/4 to achieve constructive interference.FIG. 16illustrates a diagram for obtaining constructive interference in an embodiment dipole configuration1600. As shown, the embodiment dipole configuration1600achieves constructive interference when a profile distance (d) is less than one-quarter wavelength.FIG. 17illustrates a unit cell designed using a phase of reflection coefficient.FIG. 18illustrates a graph of phase angle versus frequency.FIG. 19illustrates a suspended micro-strip line. EBG stop-band function decreases coupling between the elements in the high frequency band. Otherwise, coupling between adjacent elements decreases antenna isolation and is an indication that the element is being perturbed (e.g., degraded individual element pattern in the array environment).FIG. 20illustrates a transmission coefficient of a suspended micro strip line.

FIG. 21illustrates a block diagram of an embodiment manufacturing device2100, which may be used to perform one or more aspects of this disclosure. The manufacturing device2100includes a processor2104, a memory2106, and a plurality of interfaces2110-2112, which may (or may not) be arranged as shown inFIG. 21. The processor2104may be any component capable of performing computations and/or other processing related tasks, and the memory2106may be any component capable of storing programming and/or instructions for the processor2104. The interface2110-2112may be any component or collection of components that allows the device2100to communicate control instructions to other devices, as may be common in a factory setting.