The present disclosure is generally related to antennas and more particularly to current sheet arrays.
The development of two-dimensional planar broadband antennas has long been investigated. Current sheet arrays may be chosen over Vivaldi and loaded slot designs because they have a reduced depth, dual polarization (i.e., horizontal and vertical polarization) and small two-dimensional element spacing. Conventional current sheet arrays comprise three modes: a radiating resonant mode, a non-radiating common mode, and a radiating dipole mode. The radiating resonant mode is generally driven by the height of the array, the lattice spacing, and the capacitance between elements. The dipole mode is driven by the lattice spacing. Generally, the lattice size is chosen to fix the dipole mode, and the height and capacitance are chosen to fix the resonant mode. Under normal circumstances, the non-radiating common mode existing in conventional current sheet arrays occurs at a frequency between the radiating resonant and dipole modes. This common mode thus reduces the effective bandwidth of the antenna. Many attempts have been made to reduce or eliminate the common mode in order to connect the two radiating modes and produce an extremely wideband antenna.
For example, some conventional current sheet arrays have been developed with vias disposed so as to move the resonant and common modes above the dipole mode to provide wideband performance. By doing this, the antenna is no longer electrically small compared to its radiation band (i.e., the dipole forms the low end of the radiation band). Constructing current sheet arrays with vias configured in this way can come at the expense of high band grating lobes when placed on larger lattices.
In order to increase the bandwidth of a current sheet array, one approach is to increase the capacitance between elements. This has been done by overlapping elements or by interleaving or interdigitating portions of the planar elements in a horizontal plane. However, the increases in capacitance and in antenna performance using such approaches has been limited.
Other conventional current sheet arrays have been developed using BALUN-fed current sheet arrays in which the common mode is removed, allowing for wideband performance. However, this wideband performance comes at the expense of increased circuitry, a more difficult build procedure and a larger depth of the current sheet array. The inclusion of a BALUN with a current sheet array makes the integration with a complex feed network very difficult to manufacture.
What is needed is a current sheet array in which the common mode is eliminated without the negative aspects existing in conventional current sheet arrays. In addition, a current sheet array that is also dual polarized, small in size, easy to manufacture, capable of being curved to fit conformal applications, with no non-radiating common mode is desired.
Embodiments of the present disclosure provide array antennas, and in particular a current sheet array antennas, with broadband characteristics, and methods to broadband current sheet array antennas, by providing antenna elements having increased inter-element capacitance as compared to alternative designs. Configurations in accordance with embodiments of the present disclosure can enable the provision of antennas having a relatively broad operational bandwidth.
In accordance with embodiments of the present disclosure, an antenna array or current sheet array antenna is provided in which inter-element capacitance is increased through the inclusion of capacitive structures or features that extend in a direction that is at an angle to a plane of the dipole elements themselves. In accordance with at least some embodiments of the present disclosure, the capacitive structures are in the form of vertically facing walls or vias between the dipole arms or dipoles of each element. More particularly, each element may include orthogonally coupled dipole arms, which enables horizontally polarized (H-pol) and vertically polarized (V-pol) transmit or receive capability. The capacitive features, such as vertically facing walls or vias, between adjacent H-pol and V-Pol dipole arms, increase the capacitance between the arms. This in turn enables the bandwidth of the element to be extended as compared to a configuration in which a lower capacitance is provided. Moreover, this configuration provides a higher maximum capacitance for a given element area as compared to alternative designs. In addition, embodiments of the present invention can provide an antenna that is electrically small as compared to alternative designs.
An element incorporating dipole arms and capacitive structures as disclosed herein can be manufactured singly or as part of an array of elements using common printed circuit board (PCB) techniques. For example, a ground plane and dipole elements can be formed from conductive layers of a multi-layer board or structure. The capacitive structures or features are generally disposed perpendicular to the ground plane. The capacitive structures can be formed as plated vias. In accordance with further embodiments of the present disclosure, the capacitive structures can be formed by plating the edges of walls formed on a substrate or insulating layer. Accordingly, embodiments of the present disclosure can be manufactured simply and inexpensively using traditional PCB build processes.
Additional features and advantages of embodiments of the disclosed antennas, antenna systems, and me34thods will become more readily apparent from the following description, particularly when taken together with the accompanying drawings.
As depicted in
The elements 108 of an array antenna 104 in accordance with embodiments of the present disclosure can be operated to receive, transmit, or transmit and receive electromagnetic signals or beams 132. The electromagnetic signals 132 can include communication signals sent between the antenna 104 and communication system base stations 136, mobile devices 140, or other communication devices, signals sent as part of radar systems to determine the presence and location of distant objects 144, signals received from other transmission sources that the antenna is operational to detect as part of a signal or threat warning system, or any other purpose. In accordance with at least some embodiments of the present disclosure, signals associated with individual elements 108 can be phased relative to other elements to steer the beam 132. In accordance with still other embodiments of the present disclosure, signals associated with different dipole arm pairs 124 and 128 are orthogonally polarized from one another.
In some embodiments, a current sheet array antenna 104 may be a computer-controlled array of antenna elements 108 configured to create a beam of radio waves which may be electronically steered to point in a wide range of directions without requiring the array antenna 104 to be physically moved. Accordingly, an array antenna 104 as described herein may be configured as an active phased array. Alternatively or in certain operating modes, an array antenna 104 in accordance with embodiments of the present disclosure can be configured or operated as a passive phased array. Beamforming or spatial filtering may be used for directional signal transmission or reception by the array antenna 104. In some embodiments, adaptive beamforming may be used to detect and estimate a signal of interest. It should be appreciated that in some embodiments the array antenna 104 may be designed to be physically moveable or stationary. The signals 132 transmitted or received by the array antenna 104 may be of various wavelengths or bands of wavelengths.
An array antenna 104 as described herein may be in communication with a computer or other control system. The computer system may execute software configured to control signals transmitted by the array antenna 104 via a feed network. The computer system may further be capable of processing signals received by the array antenna 104. In some embodiments, the array antenna 104 may be used to transmit and/or receive signals in a variety of directions at a single time. As described herein, the array antenna 104 may utilize a wide bandwidth and be capable of transmitting signals 132 at frequencies or ranges of frequencies not capable of being transmitted by conventional current sheet arrays. For example, each of the signals 132 may be one of a low-, mid-, and high-frequency signal. The array antenna 104 may further be capable of detecting and receiving signals 132 over a wide range of frequencies. For example, in addition to or as opposed to transmitting signals, an array antenna 104 as described herein may further be configured to detect and/or receive signals. An array antenna 104 in accordance with at least some embodiments of the present disclosure can lower the frequency of the resonant mode of the antenna elements 108 as compared to alternative configurations by providing for increased capacitance between the dipole arms 120.
An example of an antenna element 108 in accordance with embodiments of the present disclosure is shown in a top plan view in
With continued reference to the top plan view of the antenna element shown in
As shown in
In accordance with embodiments of the present disclosure, the dipole arms 120 include capacitive elements 404 that are electrically connected to and extend from each of the branch portions 208 of those dipole arms 120, towards the ground plane 308. More particularly, the capacitive elements 404 extend at an angle to (e.g. in a direction perpendicular to) the top surface 304 of the antenna substrate 112. Moreover, the capacitive element 404 extending from any one branch portion 208 is adjacent and parallel to the capacitive element 404 extending from an adjacent branch portion 208, thereby forming a capacitive structure 504. As can be appreciated by one of skill in the art after consideration of the present disclosure, the capacitive elements 404 enable the capacitance between adjacent branch portions 208 of the elements 108 of the array antenna 104 to be increased as compared to a configuration in which conductive portions of the dipole arms 120 are confined to conductors that are on or adjacent the surface 304 of the substrate 112.
As shown in
As depicted in
In accordance with at least some embodiments of the present disclosure, the shape and area of the capacitive element 404 connected to a branch 208 of a first dipole arm 120 mirrors the shape and area of the capacitive element 404 connected to an adjacent arm portion or branch 208 of a second dipole arm 120. For example, where capacitive elements 404 include a plurality of plated vias 408, the size and number of the plated vias 408 of facing capacitive elements 404 can be the same. Although particular examples of configurations of capacitive elements 404 included as part of capacitive structures 504 in accordance with embodiments of the present disclosure have been illustrated, other configurations are possible. For example, as an alternative to having a generally rectangular form, free edges of the capacitive elements 404 can be curved, can include a number of curved or angled segments, or can otherwise be configured in a desired shape. In addition, the facing capacitive elements 404 within a capacitive structure 504 are, in various embodiments of the present disclosure, parallel to one another. Alternatively, embodiments of the present disclosure can include capacitive structures 504 in which the capacitive elements are non-parallel to one another in one or more planes. In accordance with still further embodiments of the present disclosure, the capacitive elements 404 need not be perpendicular to the ground plane 308. Furthermore, an antenna array 104 in accordance with embodiments of the present disclosure can be disposed across more than one planar surface, and/or can be at least partially disposed across a curved surface. Where at least portions of the array antenna 104 are disposed across a first surface 304 of a substrate 112 that is itself curved, components of the antenna elements 108 can also be curved, to conform to the surface 304.
Accordingly, the elements 108 of the array antenna 104 in accordance with embodiments of the present disclosure may be formed using orthogonal-coupled dipole elements 120, for example dipole arms or dipoles. Moreover, horizontal polarized and vertical polarized resonant loops may be formed by balancing the capacitance between elements with the inductance of the loops.
Aspects of a method for providing an array antenna 104 in accordance with embodiments of the present disclosure are depicted in
At step 708, a first conductive layer can be patterned to provide at least the planar portions of the antenna elements 108 on a first surface 304 side of a dielectric, which dielectric corresponds to the antenna substrate 112. Patterning the first conductive layer can include an additive process, where a conductive material, such as aluminum or some other metal, is printed, deposited, or otherwise applied to the first surface 304 of the substrate 112. Alternatively or in addition, pattering the first conductive layer can include a subtractive process in which conductive material is removed from a conductive layer applied across all or portions of the first surface 304 of the substrate 112, to obtain the desired patterns of at least the trunk 204 and branch 208 portions of the dipole arms 120 included in each of the elements 108. As can be appreciated by one of skill in the art after consideration of the present disclosure, a ground plane 308 in the form of a conductive sheet can be formed or placed on a second side 312 of the substrate 112, opposite the first side 304 of that substrate. As can further be appreciated by one of skill in the art, the process of patterning a first conductive layer and of providing a ground plane can include utilizing conventional printed circuit board (PCB) materials and processes.
At step 712, voids that extend from the first surface 304 side of the substrate 112 and towards the second side of the substrate, are formed between adjacent dipole element branches 208. For example, a trench can be formed adjacent an edge of each branch 208 that faces another branch within each element 108. Accordingly, a pair of trenches can be formed. Alternatively, a single trench that in a width direction extends between the facing edges of adjacent branches 208 within an element 108 can be formed. The trench can be formed by various methods, such as chemical etching or mechanical removal. As still another example, a series of holes or vias can be etched or drilled adjacent an edge of each branch 208 that faces another branch 208 within each element 108. Where a series of holes that are spaced apart from one another are formed, a fence like capacitive element 404 will be formed. Alternatively, a series of holes can be formed such that neighboring holes overlap one another, enabling a contiguous capacitive element 404 to be formed.
A conductive material is then placed in the voids to form capacitive elements 404 that are electrically joined to a corresponding branch 208 (step 716). For example, where trenches or a series of vias are formed adjacent an edge of each branch 208, the resulting voids can be filled with a conductive material, for example as a liquid or a paste that later hardens. As another example, such as where a single trench is formed between adjacent branches, conductive material can be plated on the facing sidewalls of the trench. Regardless of how the conductive material is disposed within the trenches or vias, it is placed in direct, electrical contact with the respective branches 208, thus forming the capacitive elements 404 of the array antenna 104.
The elements 108 can then be connected to a feed network, and in turn to transmit and/or receive electronics, forming an operational array antenna 104 (step 720). The array antenna 104 can then be associated with a platform and deployed.
Although various steps of a method have been presented in a particular sequence, it should be appreciated that the steps discussed herein can be rearranged. For example, voids for receiving conductive material to form capacitive elements 404 can be formed prior to or during the patterning of the first conductive layer. Moreover, other or additional processes can be used to form an array antenna 104 as described herein.
The foregoing discussion of the disclosed systems and methods has been presented for purposes of illustration and description. Further, the description is not intended to limit the disclosed systems and methods to the forms disclosed herein. Consequently, variations and modifications commensurate with the above teachings, within the skill or knowledge of the relevant art, are within the scope of the present disclosure. The embodiments described herein are further intended to explain the best mode presently known of practicing the disclosed systems and methods, and to enable others skilled in the art to utilize the disclosed systems and methods in such or in other embodiments and with various modifications required by the particular application or use. It is intended that the appended claims be construed to include alternative embodiments to the extent permitted by the prior art.
This application claims the benefit of U.S. Provisional Patent Application Ser. No. 63/120,585, filed Dec. 2, 2020, the entire disclosure of which is hereby incorporated herein by reference.
Number | Name | Date | Kind |
---|---|---|---|
20040104860 | Durham et al. | Jun 2004 | A1 |
20170338558 | West | Nov 2017 | A1 |
20180205134 | Khan | Jul 2018 | A1 |
20180316098 | Amadjikpe | Nov 2018 | A1 |
20210013627 | Goto | Jan 2021 | A1 |
Number | Date | Country |
---|---|---|
WO 2018077408 | May 2018 | WO |
Entry |
---|
Official Action for U.S. Appl. No. 16/876,941, dated Feb. 14, 2022 19 pages. |
Official Action for U.S. Appl. No. 16/876,941, dated Jun. 1, 2022 20 pages. |
Notice of Allowance for U.S. Appl. No. 16/876,941, dated Aug. 24, 2022 7 pages. |
Number | Date | Country | |
---|---|---|---|
63120585 | Dec 2020 | US |