Patent Grant
7498989
This invention relates to antenna elements and especially to antennas suitable for use in antenna arrays.
Those skilled in the arts of antennas, antenna arrays and beamformers know that antennas are transducers which transduce electromagnetic energy between unguided and guided-wave forms. More particularly, the unguided form of electromagnetic energy is that propagating in “free space,” while guided electromagnetic energy follows a defined path established by a “transmission line” of some sort. Transmission lines include coaxial cables, rectangular circular hollow conductive waveguides, dielectric paths, and strip conductors over ground. and the like. Antennas in principle are totally reciprocal devices, which have the same beam characteristics in both transmission and reception modes. For historic reasons, the guided-wave port of an antenna is termed a “feed” port, regardless of whether the antenna operates for transmission or reception. The beam characteristics of an antenna are established, in part, by the size of the radiating portions of the antenna relative to the wavelength. In general, small antennas make for broad or nondirective beams, and large antennas make for small, narrow or directive beams. When more directivity (narrower beamwidth) is desired than can be achieved from a single antenna, several antennas may be grouped together into an “array” and fed together in a phase-controlled manner, to generate the beam characteristics of an antenna larger than that of any single antenna element. The structures which control the phase and apportionment of power to (or from) the antenna elements are termed “beamformers.” In general, a beamformer includes at least one beam port and a plurality of element ports. In a transmit mode, the signal to be transmitted is applied to the beam port and is distributed by the beamformer to the various element ports. In the receive mode, the unguided electromagnetic signals are received by the antenna elements and coupled in guided form to the element ports of the beamformer, and are combined in the beamformer to produce a beam signal at the beam port of the beamformer. A salient advantage of sophisticated beamformers is that they may include a plurality of beam ports, each of which distributes the electromagnetic energy in such a fashion that different antenna beams may be generated simultaneously.
Array antennas are well known for various communication and sensing purposes, and exhibit advantages over shaped-reflector antennas in that scanning of the beam or beams through spatial angles can be performed essentially instantaneously, without inertia problems associated with the moving of a discrete object. In order to perform its role of setting the direction of the antenna beam of an array, a beamformer must set the element-to-element phase of the signal being transduced. So long as the beam direction is fixed, fixed phase shifting elements may be used in the beamformer to set the element-to-element phase. Such phase shifting elements are ordinarily passive rather than active. Those skilled in the art know that passive elements are ordinarily very reliable. When the shape or direction of the array antenna beam must be controllable rather than fixed, it is customary to use controllable phase shifters in the beamformers. Controllable phase shifters may be analog or digital. Current designs prefer multibit digital types of phase shifters because they can be controlled by simple digital signals, and because the phase shifts can be readily and accurately set.
It will be appreciated that an array antenna, when used with a beamformer for transmitting signal, may require the application of significant power to the beam port(s) of the beamformer in order to achieve the desired power density in the radiated beam so formed. This power tends to be attenuated by the unavoidable “heating” or “ohmic” losses in the beamformer. It may be found to be desirable to distribute relatively small-amplitude signals through the beamformer, and to amplify the signal at the individual element ports of the beamformer before application to each element of the antenna array for transmission. Thus, the array antenna when used for transmission may require a “power” or “transmit” amplifier for each antenna array element or group of elements. When an array antenna is operated in a receiving mode, the signal received by each antenna element must pass through the beamformer before being combined with signals received by other antenna elements. Since the beamformer is subject to losses, the received signal tends to be attenuated by passage through the beamformer. This attenuation tends to undesirably reduce the signal-to-noise ratio of the combined received signal at the beam port of the beamformer. The signal-to-noise ratio can often be improved by amplifying the signal received by each antenna element in a low-noise amplifier before application of the signal to the beamformer.
Selection or control of the antenna beam of an array antenna also involves the “weighting” of the relative power applied to the various antenna elements of the array. The purpose of weighting is to establish the sidelobe level and the distribution of directivity as between the main antenna beam lobe(s) and unwanted subsidiary lobes. An unweighted distribution provides each antenna element of the array with equal weight, meaning that in a transmission mode of operation all antenna elements are excited with equal amplitude signals, and in a receive mode of operation the combining of the signals from the various antenna elements is made with equal amplitude. Such a uniform weighting may be desirable when maximum directivity or gain is desired. However, a uniform aperture distribution tends to result in significant sidelobe levels, which are about −13 dB to −18 dB relative to the peak of the main lobe. The sidelobes may be viewed as being an inherent defect of an antenna, in that they result in transmission of power in directions other than the desired direction, or reception of signals from directions other than that desired. Such transmission in unwanted directions can result in detection of the source of the signals by hostile forces, and in any case represents a waste of transmitter power toward regions of no interest. The reception of signals from undesired directions can expose the antenna to jamming signals from unknown directions. The prior art controls the sidelobe level of an antenna by weighting or adjusting the aperture field distribution. Examples of prior art weighting functions that produce low side lobe levels in the absence of element failures include raised-cosine weighting, Dolph-Tschebyscheff weighting, and Taylor weighting functions. Weighting in an array antenna is ordinarily a function of the beamformer. The distribution of signals in the beamformer may be accomplished by power dividers (or power combiners in receive mode) selected to give the desired array element weighting. In some instances, variable gain or attenuation may be used.
Thus, each antenna element of an array antenna may be associated with a “power” amplifier for use in a transmit mode, a “low-noise” amplifier for use in a receive mode, in addition to at least one phase shifter, and more than one phase shifter if the transmit beam direction may differ from the receive beam direction. The power amplifier, the low-noise amplifier, and the phase shifter(s) associated with each antenna element (or possibly subarray of antenna elements) are often combined into a “transmit-receive” (TR) module. This module, in addition to the amplifiers and phase shifter(s) may also include any controllable gain elements, radio-frequency (RF) switches for switching between transmit and receive modes of operation, controls for the switches, and power supplies for the various controls and active devices.
In the past, the term “radio frequency” was interpreted to mean a limited range of frequencies, such as, for example, the range extending from about 20 KHz to 2 MHz. Those skilled in the art know that “radio” frequencies as now understood extends over the entire frequency spectrum, including those frequencies in the “microwave” and “millimeter-wave” regions, and up to light-wave frequencies. Many of these frequencies are very important for commercial purposes, as they include the frequencies at which radar systems, global positioning systems, satellite cellular communications and ordinary terrestrial cellphone systems operate.
It will be appreciated that an array antenna, especially one containing thousands or tens of thousands of antenna elements, may be physically large. The large physical size, in turn, means that wind loading may impart strong forces to the structure and to the antenna elements themselves. It is common to protect the antenna elements by the use of a “radome.” The “dome” aspect of the term “radome” comes from a time at which physically movable antennas were used for scanning, and the protective radomes were generally at least partially spherical. The radome is intended to protect the antenna elements from the environment, and may be planar if appropriate. Antenna elements which project significantly from their feed points, such as the axial helix antenna elements described in U.S. Pat. No. 5,258,771 issued Nov. 2, 1993 in the name of Praba, may be difficult to protect with a simple radome structure. Praba describes an antenna array operating in two disparate frequency bands, which uses interleaved axial-mode “helical” antenna elements. Each such helical antenna includes an electrically conductive element helically disposed about a longitudinal axis, with a feed point adjacent a ground plane disposed orthogonal to the axis of the helix. Such helical antenna elements are well known, and have the advantage, when so fed against a ground plane, of providing moderately high gain, together with circular polarization. In order to reduce the interaction between the helical antenna elements of the arrays at the disparate frequencies as described by Praba, the helices of the two interleaved arrays are oppositely wound, so that a right-circularly-polarized antenna element is adjacent a left-circularly-polarized antenna element, which results in some degree of rejection of the cross-polarization signal from the adjacent elements, and thereby tends to reduce mutual coupling between the antenna elements of the two interleaved arrays.
Other types of antenna elements can be used in array antennas. So-called “patch” antennas are generally planar, and in the context of an array antenna lie in the plane of the array, without significant projections above (in the radiating direction relative to) the plane of the array. Such patch antennas have the salient advantage of low wind loading, and are easy to protect with a planar radome.
In order to transmit or receive electromagnetic signal, an antenna element must respond to an electromagnetic field traveling toward or from the desired direction. In order to respond to the electromagnetic signal, the antenna must have a finite physical extent or “aperture” in the desired polarization in order to interact with the field being transduced. One of the salient advantages of an arrangement such as that of the Praba patent is that it has finite extent in two dimensions. A planar array of planar patch antenna elements, when viewed from a direction orthogonal to the plane of the array, has a physical extent which substantially equals the patch dimension for the polarization in question. Viewed from a location within the plane of the array, however, each patch antenna has substantially zero projected extent or dimension, at least in one polarization. Consequently, the ability of a planar array of planar or patch antennas to transceive in the direction of the plane may be limited, or in antenna terms it may have relatively low “gain”. In addition to the problem of lack of projected dimension which results in low gain in the plane of the array, there is the problem that radiation to or from any one element of the array must pass by one or more adjacent antenna elements. These adjacent antenna elements tend to interact with so much field as may exist, which in turn tends to “block” the field to or from adjacent antenna elements. This interaction between mutually adjacent antenna elements of an array is termed “mutual coupling.” One manifestation of mutual coupling is a tendency of the impedance of the antenna element to be dependent on the signal transduced by the adjacent (and sometimes semi-adjacent) elements. Mutual coupling often has adverse consequences in the overall operation of the array, and may be undesired.
It is desirable to be able to produce as much radiated power as possible in the transmitting mode of the antenna array in order to maximize the power aperture efficiency. The passage of electromagnetic signal through the radome results in heating of the radome. Since the radome may also be subject to substantial solar loading, it is desirable to reduce the radome temperature.
Improved or alternative antenna arrays and elements therefor are desired.
An antenna element according to an aspect of the invention comprises a generally planar ground plane and an electrically conductive first planar disk lying parallel with the ground plane and spaced therefrom by a first distance. The first planar disk defines a feed side facing the ground plane. An electrically conductive second planar disk lies parallel with the ground plane and is spaced therefrom by a second distance, greater than the first distance. The second planar disk is registered with the first planar disk, at least in that they are concentric. An elongated thermally conductive element is thermally coupled to a first location on the ground plane, extends perpendicular to the ground plane along a central axis, and makes thermal contact with the center of the first planar disk and with the center of the second planar disk. At least first and second feed conductors make contact with the feed side of the first planar disk at first and second feed locations lying on a first line extending through the central axis. This antenna element may be associated with a locally planar radome overlying and thermally coupled to the second planar disk and the thermally conductive element. In a preferred embodiment of this antenna element, the elongated thermally conductive element is electrically conductive, and additionally makes electrical contact with centers of the first and second disks and with the ground plane. In one manifestation, the first and second feed locations are equidistant from the central axis. In a preferred version, the antenna element further comprises at least a first wing supported by the ground plane, the first wing is oriented so that the central axis lies in a plane thereof which is orthogonal to the ground plane. The first wing lies outside of the projection, parallel with the central axis, of the second planar disk, and the plane of the first wing lies equidistant from the first and second feed locations. A more preferred version further comprises at least a second wing, which may also define a plane, supported by the ground plane. The plane of the second wing lies in the same plane as that of the first wing. The second wing lies outside of the projection, parallel with the central axis, of the second planar disk, and diametrically opposite to the first wing about the central axis. In a most preferred embodiment, both wings are metallic or dielectric, or the first wing is metallic and the second wing is dielectric. The dielectric of the wings is high-dielectric-constant material. The first wing may have a generally rectangular outline.
The first and second feed conductors of the antenna element according to an aspect of the invention may comprise lesser conductors of first and second unbalanced feed transmission lines, each defining a greater conductor. The greater conductors of the first and second unbalanced feed transmission lines make electrical contact with the ground plane at first and second feedthrough locations, which first and second feedthrough locations are located at or centered on projections, parallel with the central axis, onto the ground plane from the first and second feed locations, respectively. More particularly, the first and second feed conductors may comprise center conductors of first and second feed coaxial transmission lines, each defining an outer conductor. The outer conductors of the first and second feed coaxial transmission lines make electrical contact with the ground plane at first and second feedthrough locations. The first and second feedthrough locations are located at or centered on projections, parallel with the central axis, onto the ground plane from the first and second feed locations, respectively. Thus, the first and second feedthrough locations are locations at which the center conductors of the first and second coaxial transmission lines extend through the ground plane without making electrical contact with the ground plane.
Another embodiment of the antenna element, includes third and fourth feed conductors. The third and fourth feed conductors make contact with the feed side of the first planar disk at third and fourth feed locations lying on a second line extending through the central axis and perpendicular to the first line extending from the first feed location to the second feed location. Ideally, the first and second feed locations are equidistant from the central axis, and if there are first, second, third, and fourth feed locations, all are equidistant from the central axis.
According to certain aspects of the invention, antenna element comprises at least a first wing supported by the ground plane. The first wing is oriented so that the central axis lies in the plane thereof. The first wing lies outside of the projection, parallel with the central axis, of the second planar disk, and the plane of the first wing lies equidistant from the first, second, third, and fourth feed locations. Some embodiments may further comprising a locally planar radome overlying and thermally coupled to the second planar disk andor to the thermally conductive element.
An antenna element according to another aspect of the invention may further comprise third and fourth feed conductors, making contact with the feed side of the first planar disk at third and fourth feed locations lying on a second line extending through the central axis, the second line extending perpendicular to the first line which extends from the first feed location to the second feed location. In this aspect of the invention, the first and second feed conductors comprise center conductors of first and second coaxial transmission feed lines each defining an outer conductor. The outer conductors of which first and second coaxial transmission lines make electrical contact with the ground plane at first and second particular locations, respectively, which are projections, parallel with the central axis, onto the ground plane from the first and second feed locations, respectively. The third and fourth feed conductors comprise center conductors of third and fourth coaxial transmission feed lines, each defining an outer conductor, the outer conductors of which third and fourth coaxial transmission lines make electrical contact with the ground plane at third and fourth particular locations which are projections, parallel with the central axis, onto the ground plane from the third and fourth feed locations, respectively. The antenna according to this aspect of the invention may further comprise at least a first wing supported by the ground plane. The first wing may be generally planar. The first wing is oriented so that the central axis lies in the plane of the first wing. The first wing lies outside of the projection, parallel with the central axis, of the second planar disk. The first wing may be electrically conductive. The antenna according to this aspect of the invention may further include a second wing supported by the ground plane. The second wing may define a plane lying in the same plane as that of the first wing. The second wing lies outside of the projection, parallel with the central axis, of the second planar disk, and diametrically opposite, relative to the central axis, the first wing. When two wings are provided, both wings are metallic or dielectric, or the first wing is electrically conductive or metallic and the second wing is dielectric. The dielectric of the wings is high-dielectric-constant material. In one embodiment, the maximum projection of the first wing from the ground plane is no greater than the maximum projection of the second planar disk from the ground plane. The plane of the first wing may lie equidistant from the first and second feed locations, or from the first, second, third, and fourth feed locations, if provided. If four feed locations are provided, the plane of the first wing may lie equidistant from the first, second, third, and fourth feed locations.
An antenna element according to another aspect of the invention comprises a generally planar ground plane, and an electrically conductive first planar disk lying parallel with the ground plane and spaced therefrom by a first distance. The first planar disk defines a feed side facing the ground plane and is centered on a central axis of the antenna element. An electrically conductive second planar disk (18) lies parallel with the ground plane and is spaced therefrom by a second distance, greater than the first distance. The second planar disk is centered on the central axis. The first and second planar disks may be of different sizes. At least first and second feed conductors make contact with the feed side of the first planar disk at first and second feed locations lying on a first line extending through the central axis. At least a first wing is supported by the ground plane. The first wing may be planar, and oriented so that the central axis lies in the plane thereof. In one embodiment of this aspect of the invention, the first wing is electrically conductive or includes a metallic component. The first and second feed locations may be equidistant from the central axis. The first wing may lie outside of the projection, parallel with the central axis, of the second planar disk, and the plane of the first wing may lie equidistant from the first and second feed locations. The first wing may have a generally rectangular outline. In one version of this aspect, the antenna element further comprises third and fourth feed conductors. The third and fourth feed conductors make contact with the feed side of the first planar disk at third and fourth feed locations, respectively, lying on a second line extending through the central axis and perpendicular to the first line extending from the first feed location to the second feed location. The first feed location and the second feed location are preferably equidistant from the central axis. Most preferably, the first, second, third, and fourth feed locations are equidistant from the central axis. The plane of the first wing preferably lies equidistant from the first, second, third, and fourth feed locations. The maximum projection of the first wing from the ground plane is no greater than the maximum projection of the second planar disk from the ground plane.
An antenna array according to an aspect of the invention comprises plural elemental antennas. Each of the elemental antennas includes a plurality (two illustrated) of stacked, concentric, generally planar antenna elements. Each of the elemental antennas includes a first wing generally defining a plane orthogonal to the plane (or planes) of the planar antenna elements and also includes a second wing generally defining a plane orthogonal to the plane of the planar antenna elements. The first and second wings are coplanar, with the axis of concentricity of the planar antenna elements lying in the plane of the first and second wings. The plurality of elemental antennas is arrayed in a planar manner, with no wing of any elemental antenna lying directly between the axes of concentricity of adjacent ones of the elemental antennas.
An antenna array according to another aspect of the invention comprises a plurality of elemental antennas arrayed in a plane. Each of the elemental antennas includes stacked, concentric, generally planar antenna elements. Each of the elemental antennas includes a first wing generally defining a plane orthogonal to the planes of the antenna elements and a second wing also generally defining a plane orthogonal to the planes of the antenna elements. The first and second wings are coplanar, with the axis of concentricity lying in the common plane of the first and second wings. The arraying of the plurality of elemental antennas is such that the wings of the elemental antennas lie at least partially between adjacent ones of the antenna elements, but not directly between the axes of concentricity thereof. When two wings are provided, both wings are metallic or dielectric, or the first wing is electrically conductive or metallic and the second wing is dielectric. The dielectric of the wings is high-dielectric-constant material.
In an antenna array or subarray according to an aspect of the invention, the antenna array or subarray comprises a plurality of elemental antennas. Each of the elemental antennas comprises:
a is a simplified representation of an unbalanced microstrip feed structure, and
In
The description herein includes relative placement or orientation words such as “top,” “bottom,” “up,” “down,” “lower,” “upper,” “horizontal,” “vertical,” “above,” “below,” as well as derivative terms such as “horizontally,” “downwardly,” and the like. These and other terms should be understood as to refer to the orientation or position then being described, or illustrated in the drawing(s), and not to the orientation or position of the actual element(s) being described or illustrated. These terms are used for convenience in description and understanding, and do not require that the apparatus be constructed or operated in the described position or orientation. Similarly, terms concerning mechanical attachments, couplings, and the like, such as “connected,” “attached,” “mounted,” refer to relationships in which structures are secured or attached to one another either directly or indirectly through intervening structures, as well as both movable and rigid attachments or relationships, unless expressly described otherwise.
The antenna 12 of
Another linear feed for antenna 10 of
It is also possible to excite the antenna 10 of
According to an aspect of the invention, an elongated thermally and electrically conductive element or rod 30 is thermally affixed to ground plane 12 concentric with central axis 8. Rod 30 extends through dielectric support element 16, and makes thermal and electrical contact with the underside of second conductive disk 18. Rod 30 also makes thermal and electrical contact with first conductive disk 14, either peripherally where rod 30 passes through disk 14, or by being separated into two parts, one of which extends from ground plane 12 to the underside of disk 14, and another of which extends from the upper side of disk 14 to disk 18.
A radome designated 60 is illustrated as overlying second conductive disk 18 in
According to an aspect of the invention, when two wings are provided, both wings are metallic or dielectric, or the first wing is electrically conductive or metallic and the second wing is dielectric. The dielectric of the wing or wings is high-dielectric-constant material. Such wings tend to reduce the flow of surface waves along an array of elements at large elevation scan angles, thereby tending to increase the bandwidth and scan ability of the antenna array.
In
When a plurality of tiles such as those of
It has been discovered that if both wings of each elemental antenna of an array are made from electrically conductive material, some resonances in the form of standing waves can occur at large elevation scan angles. The standing waves support the excitation of the even mode in the feed circuits and create almost full reflection. These surface wave resonances can be suppressed by making one of the wings of each pair, say wing 550a of
Thus, an antenna element (10) according to an aspect of the invention comprises a generally planar ground plane (12) and an electrically conductive first planar disk (14) lying parallel with the ground plane (12) and spaced therefrom by a first distance (S1). The first planar disk (14) defines a feed side (14ls) facing the ground plane (12). An electrically conductive second planar disk (18) lies parallel with the ground plane (12) and is spaced therefrom by a second distance (S2), greater than the first distance (S1). The second planar disk (18) is registered with the first planar disk (14), at least in that they are concentric. An elongated thermally and electrically conductive element (30) is thermally and electrically coupled to a first location (12R) on the ground plane (12), extends perpendicular to the ground plane (12) along a central axis (8), and makes thermal and electrical contact with the center of the first planar disk (14) and with the center of the second planar disk (18). At least first (20ac) and second (20bc) feed conductors make contact with the feed side (14ls) of the first planar disk (14) at first (14a) and second (14b) feed locations lying on a first line (210) extending through the central axis (8). This antenna element (10) may be associated with a locally planar radome (60) overlying and thermally coupled to the second planar disk (18) and the thermally conductive element (30). In a preferred embodiment of this antenna element (10), the elongated thermally conductive element (30) is electrically conductive, and additionally makes electrical contact with centers of the first (14) and second (18) disks and with the ground plane (12). In one manifestation, the first (14a) and second (14b) feed locations are equidistant from the central axis (8). In a preferred version, the antenna element (10 further comprises at least a first wing (50a) supported by the ground plane (12), the first wing (50a) being oriented so that the central axis (8) lies in a plane (50p) thereof which is orthogonal to the ground plane (12). The first wing (50a) lies outside of the projection, parallel with the central axis (8), of the second planar disk (18), and the plane (50P) of the first wing (50a) lies equidistant from the first (14a) and second (14b) feed locations. A more preferred version further comprises at least a second wing (50b), which may also define a plane (50P), supported by the ground plane (12). The plane (50P) of the second wing (50b) lies in the same plane as that of the first wing (50a). The second wing (50b) lies outside of the projection, parallel with the central axis (8), of the second planar disk (18), and diametrically opposite to the first wing (50a) about the central axis (8). In a most preferred embodiment, both wings are metallic or dielectric, or the first wing is metallic and the second wing is dielectric. The dielectric of the wings is high-dielectric-constant material. The first wing may have a generally rectangular outline.
The first (20ac) and second (20bc) feed conductors of the antenna element (10) according to an aspect of the invention may comprise lesser conductors of first (20a) and second (20b) unbalanced feed transmission lines, each defining a greater (outer) conductor. The greater conductors of the first (20a) and second (20b) unbalanced feed transmission lines make electrical contact with the ground plane (12) at first (12a) and second (12b) feedthrough locations, which first and second feedthrough locations are located at or centered on projections, parallel with the central axis (8), onto the ground plane (12) from the first (14a) and second (14b) feed locations, respectively. More particularly, the first and second feed conductors may comprise center conductors of first (20a) and second (20b) feed coaxial transmission lines, each defining an outer conductor (20aoc; 20boc). The outer conductors (20aoc; 20boc) of the first (20a) and second (20b) feed coaxial transmission lines make electrical contact with the ground plane (12) at first (12a) and (12b) second feedthrough locations. The first (12a) and second (12b) feedthrough locations are located at or centered on projections, parallel with the central axis (8), onto the ground plane (12) from the first (14a) and second (14b) feed locations, respectively. Thus, the first (12a) and second (12b) feedthrough locations are locations at which the center conductors (20ac; 20bc) of the first (20a) and second (20b) coaxial transmission lines extend through the ground plane (12) without making electrical contact with the ground plane.
Another embodiment of the antenna element (10), includes third (22ac) and fourth (22bc) feed conductors. The third (22ac) and fourth (22bc) feed conductors make contact with the feed side (14ls) of the first planar disk (14) at third (14c) and fourth (14d) feed locations lying on a second line (212) extending through the central axis (8) and perpendicular to the first line (210) extending from the first feed location (14a) to the second (14b) feed location. Ideally, the first and second feed locations are equidistant from the central axis (8), and if there are first (14a), second (14b), third (14c), and fourth (14d) feed locations, all are equidistant from the central axis (8).
According to certain aspects of the invention, antenna element (10) comprises at least a first wing (50a) supported by the ground plane (12). The first wing (50a) is oriented so that the central axis (8) lies in the plane thereof. The first wing (50a) lies outside of the projection, parallel with the central axis (8), of the second planar disk (18), and the plane of the first wing (50a) lies equidistant from the first, second, third, and fourth feed locations. Some embodiments may further comprising a locally planar radome (60) overlying and thermally coupled to the second planar disk (18) andor to the thermally conductive element (30).
An antenna element according to another aspect of the invention may further comprise third (22ac) and fourth (22bc) feed conductors, making contact with the feed side (14ls) of the first planar disk (14) at third (14c) and fourth (14d) feed locations lying on a second line (212) extending through the central axis (8), the second line (212) extending perpendicular to the first line (210) which extends from the first feed location (14a) to the second feed location (14b). In this aspect of the invention, the first (20ac) and second (20bc) feed conductors comprise center conductors of first (20a) and second (20b) coaxial transmission feed lines each defining an outer conductor (20aoc, 20boc). The outer conductors (20aoc, 20boc) of which first (20a) and second (20b) coaxial transmission lines make electrical contact with the ground plane (12) at first (12a) and second (12b) particular locations, respectively, which are projections, parallel with the central axis (8), onto the ground plane (12) from the first (14a) and second (14b) feed locations, respectively. The third (22ac) and fourth (22bc) feed conductors comprise center conductors of third (22a) and fourth (22bc) coaxial transmission feed lines, each defining an outer conductor (22aoc, 22boc), the outer conductors (22aoc, 22boc) of which third (22a) and fourth coaxial (22b) transmission lines make electrical contact with the ground plane (12) at third (12c) and fourth (12d) particular locations which are projections, parallel with the central axis (8), onto the ground plane (12) from the third (14c) and fourth (14d) feed locations, respectively. The antenna according to this aspect of the invention may further comprise at least a first wing (50a) supported by the ground plane (12). The first wing (50a) may be generally planar. The first wing (50a) is oriented so that the central axis (8) lies in the plane of the first wing (50a). The first wing (50a) lies outside of the projection, parallel with the central axis (8), of the second planar disk (18). The first wing (50a) may be electrically conductive. The antenna according to this aspect of the invention may further include a second wing (50b) supported by the ground plane (12). The second wing (50b) may define a plane lying in the same plane as that of the first wing (50a). The second wing (50b) lies outside of the projection, parallel with the central axis (8), of the second planar disk (18), and diametrically opposite, relative to the central axis (8), the first wing (50a). In a most preferred embodiment, both wings are metallic or dielectric, or the first wing is metallic and the second wing is dielectric. The dielectric of the wings is high-dielectric-constant material. The first wing may have a generally rectangular outline. In one embodiment, the maximum projection of the first wing (50a) from the ground plane (12) is no greater than the maximum projection of the second planar disk (18) from the ground plane (12). The plane of the first wing (50a) may lie equidistant from the first (14a) and second (14b) feed locations, or from the first (14a), second (14b), third (14c) and fourth (14d) feed locations, if provided. If four feed locations are provided, the plane of the first wing (50a) may lie equidistant from the first (14a), second (14b), third (14c), and fourth (14d) feed locations.
An antenna element according to another aspect of the invention comprises generally planar ground plane (12), and an electrically conductive first planar disk (14) lying parallel with the ground plane (12) and spaced therefrom by a first distance (S1). The first planar disk (14) defines a feed side (14ls) facing the ground plane (12) and is centered on a central axis (8) of the antenna element. An electrically conductive second planar disk (18) lies parallel with the ground plane (12) and spaced therefrom by a second distance (S2), greater than the first distance (S1). The second planar disk (18) is centered on the central axis (8). The first and second planar disks may be of different sizes. At least first (20ac) and second (20bc) feed conductors make contact with the feed side (14ls) of the first planar disk (14) at first (14a) and second (14b) feed locations lying on a first line (210) extending through the central axis (8). At least a first wing (50a) is supported by the ground plane (12). The first wing (50a) may be planar, and oriented so that the central axis (8) lies in the plane thereof. In one embodiment of this aspect of the invention, the first wing (50a) is electrically conductive or includes a metallic component. The first (14a) and second (14b) feed locations may be equidistant from the central axis (8). The first wing (50a) may lie outside of the projection, parallel with the central axis (8), of the second planar disk (18), and the plane of the first wing (50a) may lie equidistant from the first (14a) and second (14b) feed locations. The first wing (50a) may have a generally rectangular outline. In one version of this aspect, the antenna element further comprises third (22ac) and fourth (22bc) feed conductors. The third (22ac) and fourth (22bc) feed conductors make contact with the feed side (14ls) of the first planar disk (14) at third (14c) and fourth (14d) feed locations lying on a second line (212) extending through the central axis (8) and perpendicular to the first line (210) extending from the first feed (14a) location to the second (14b) feed location. The first feed (14a) location and the second (14b) feed location are preferably equidistant from the central axis (8). Most preferably, the first (14a), second (14b), third (14c), and fourth (14d) feed locations are equidistant from the central axis (8). The plane of the first wing (50a) preferably lies equidistant from the first, second, third, and fourth feed locations. The maximum projection of the first wing (50a) from the ground plane (12) is no greater than the maximum projection of the second planar disk (18) from the ground plane (12).
A antenna array according to an aspect of the invention comprises plural elemental antennas (10). Each of the elemental antennas (10) includes a plurality (two illustrated) of stacked, concentric, generally planar antenna elements (12, 14). Each of the antenna elements (12, 14) includes a first wing (50a) generally defining a plane orthogonal to the plane (or planes) of the planar antenna elements and also includes a second wing (50b) generally defining a plane orthogonal to the plane of the antenna elements. The first (50a) and second (50b) wings are coplanar, with the axis of concentricity (8) of the planar antenna elements (12, 14) lying in the plane of the first (50a) and second (50b) wings. The plurality of elemental antennas (10) is arrayed in a planar manner, with no wing (50a or 50b) of any elemental antenna (10) lying directly between the axes of concentricity (8) of adjacent ones of the elemental antennas.
An antenna array according to another aspect of the invention comprises a plurality of elemental antennas (10) arrayed in a plane. Each of the elemental antennas (10) includes stacked, concentric, generally planar antenna elements (12, 14). Each of the elemental antennas (10) includes a first wing (50a) generally defining a plane orthogonal to the planes of the antenna elements (12, 14) and a second wing (50b) also generally defining a plane orthogonal to the planes of the antenna elements. The first (50a) and second (50b) wings are coplanar, with the axis of concentricity (8) lying in the common plane of the first (50a) and second (50b) wings. The arraying of the plurality of elemental antennas (10) is such that the wings of the elemental antennas lie at least partially between adjacent ones of the antenna elements. In a most preferred embodiment, both wings are metallic or dielectric, or the first wing is metallic and the second wing is dielectric. The dielectric of the wings is high-dielectric-constant material. The first wing may have a generally rectangular outline.
In an antenna array or subarray according to an aspect of the invention, the antenna array or subarray comprises a plurality of elemental antennas. Each of the elemental antennas (10) comprises:
The generally planar ground plane (12) of the elemental antennas (10) is electrically continuous across the array or subarray. The first and second feed conductors of each of the elemental antennas of the array or subarray are fed with the same phase progression as other antenna elements of the array or subarray. In one embodiment of such an array or subarray, the elongated thermally conductive element (30) is additionally electrically conductive, and is electrically and thermally coupled to a first location on the ground plane (12) and makes electrical and thermal contact with the center (14c) of the first planar disk (14) and with the center (18c) of the second planar disk (18). An embodiment may further comprise a radome (60) extending over the second planar disk (18) of each elemental antenna of the array or subarray, which radome is in thermal communication with the second planar disk (18) and the thermal element (30) of each antenna element (10) of the array or subarray. In one version, each elemental antenna (10) of the antenna array (500) or subarray further comprises at least a first wing (50a) supported by the ground plane (12), which first wing (50a) is oriented so that the central axis (8) lies in a plane thereof. The first wing (50a) may lie outside of the projection, parallel with the central axis (8), of the second planar disk (18). The plane of the first wing (50a) may lie equidistant from the first (14a) and second (14b) feed locations. A second wing (50b) may be included, in which case the first wing (50a) may be electrically conductive and the second wing (50b) may be of a metal or dielectric material.
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