Abstract
Dielectric-free, metal-only, dipole-coupled radiating array aperture with wide field of view.
Claims
1. A dipole-coupled radiator structure, comprising: a ground surface having first and second openings disposed therethrough; and a pair of antenna loops with each loop disposed in a respective plane perpendicular to the ground plane, a selected one of the loops having a first end shorted to the ground surface and a second end disposed in a respective one of the first and second openings, with the respective planes of the antenna loops oriented perpendicular to one another.
2. The dipole-coupled radiator structure according to claim 1, wherein each loop of the pair of antenna loops includes a loop having a first end shorted to the ground surface and a second end disposed in a respective one of the first and second openings.
3. The dipole-coupled radiator structure according to claim 1, wherein the loops comprise self-supporting metal structures.
4. The dipole-coupled radiator structure according to claim 1, comprising RF transmitter/receiver circuits below the ground surface in electrical communication with the second end of each loop.
5. A two-dimensional array of radiator structures according to any of the preceding claims, comprising first and second adjacent antenna loops in the array which are capacitively coupled to one another.
6. The two-dimensional array according to claim 5, wherein the array comprises dual-polarized differentially-fed shorted dipoles.
7. The two-dimensional array according to claim 5, wherein the array comprises a first pair of loops disposed in a first plane and a second pair of loops disposed in a second plane orthogonal to the first plane to provide a plus-shaped configuration of loops, where each of the loops of the first and second pairs comprises an end proximate the center of the plus-shape which ends are shorted to the ground surface.
8. The two-dimensional array according to claim 5, wherein the array comprises a first pair of loops disposed in a first plane and a second pair of loops disposed in a second plane orthogonal to the first plane to provide a plus-shaped configuration of loops, where each of the loops of the first and second pairs comprises an end proximate the center of the plus-shape which ends are disposed in an opening through the ground surface.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] The foregoing summary and the following detailed description of exemplary embodiments of the present invention may be further understood when read in conjunction with the appended drawings, in which:
[0008] FIGS. 1a-1c schematically illustrate an exemplary configuration of a unit cell of a single-polarized antenna in accordance with the present invention, in which FIG. 1a illustrates a top-down view of the unit cell, FIG. 1b illustrates a isometric view, and FIG. 1c illustrates a cross-sectional view of FIG. 1b taken down a midline of differentially-fed shorted arms of the antenna;
[0009] FIG. 1d schematically illustrates an alternative configuration of a unit cell of a single-polarized antenna in accordance with the present invention;
[0010] FIG. 2 schematically illustrates a four-element by four-element two-dimensional array of the single-polarized unit cell depicted in FIGS. 1a-1c;
[0011] FIGS. 3a-3c schematically illustrate another exemplary configuration of a unit cell of a single-polarized antenna similar to that of FIGS. 1a-1c but having a uniform cross-section in the antenna portions, in which FIG. 3a illustrates a top-down view of the unit cell, FIG. 3b illustrates a isometric view, and FIG. 3c illustrates a cross-sectional view of FIG. 3b;
[0012] FIGS. 4-6 illustrate the expected performance of an antenna of the present invention;
[0013] FIGS. 7a-7c schematically illustrate a two-dimensional, 4-element by 4-element array of dual-polarized, differentially-fed, shorted dipoles in accordance with the present invention, in which FIG. 7a illustrates a top-down view of a unit cell of the array, FIG. 7b illustrates a isometric view of the unit cell, and FIG. 7c illustrates an isometric view of the array;
[0014] FIGS. 8a-8c schematically illustrate a further two-dimensional, 4-element by 4-element array of dual-polarized, differentially-fed, shorted dipoles in accordance with the present invention, in which FIG. 8a illustrates a top-down view of a unit cell of the array, FIG. 8b illustrates a isometric view of the unit cell, and FIG. 8c illustrates an isometric view of the array;
[0015] FIG. 9 schematically illustrates a three-dimensional array comprising multiple two-dimensional arrays of the present invention, such as the arrays of FIGS. 2, 7, 8; and
[0016] FIGS. 10a, 10b schematically illustrate coupling between the adjacent dipoles using interleaved or interwoven arms, respectively.
DETAILED DESCRIPTION OF THE INVENTION
[0017] Referring now to the figures, wherein like elements are numbered alike throughout, FIGS. 1a-1c schematically illustrate an exemplary configuration of a unit cell 100 of a single-polarized antenna in accordance with the present invention. The antenna may include a differentially fed shorted arms 2, 8 of the antenna positioned above a ground surface (such as ground plane 6 or other surface shape, e.g., a conformal surface) and fed via a feed region 4, which may include one or more openings. (Though exemplary configurations of present invention may be illustrated as having a ground “plane”, other surface shapes, such as conformal surfaces, may be provided for grounding.) The arms 2, 8 may cooperate to provide a dipole. The feed region 4 may be provided with no wall separating the feed points for the two differentially-fed shorted arms 2, 8. Alternatively, a wall 30 may be provided as illustrated in FIGS. 3a-3b. The arms 2, 8 may have a cross-sectional dimension that varies along the arms 2, 8 and may or may not be identical to one another. Alternatively, the arms 22, 28 may be ‘U’-shaped of constant cross-sectional dimension depending on the requirements of the design or to optimize performance, FIGS. 3a-3c. Still further, opposing ends of the arms 2, 8 may be of the same height above the ground plane 6 with a horizontal leg 3, 5 therebetween, FIG. 1b. Instead, the opposing ends of the arms 12, 18 may be of different height above the ground plane 16 with a sloped leg 13, 15 therebetween, FIG. 1d. This may be done for impedance matching over a greater bandwidth than what would be typical for flat precisely horizontal legs.
[0018] Similar to FIGS. 1a-1c, the structure of FIGS. 3a-3c may include a ground plane 26 and feed region 24. In addition, an array 200 of the antennas 100 of FIGS. 1a-1c (or antennas 300 of FIGS. 3a-3c) may be provided as illustrated in FIG. 2. In such as case the field generated by a dipole (i.e., pair of arms 2, 8) of the array 200 may be couple adjacent dipoles. For stronger coupling between the adjacent dipoles 71, 72, the legs 73, 74 could be interdigitated in either the vertical or horizontal direction (or both), FIG. 10a, which could be formed, for example, by the PolyStrata® process. Alternatively, the coupling between the adjacent dipoles 81, 82 may be implemented with interwoven legs 83, 84 that could be formed by 3D metal printing. Such coupling using interwoven or interleaved legs could provide additional degrees of design freedom.
[0019] The expected performance of antenna designs of the present invention is illustrated in FIGS. 4-6 for a point design that should operate from roughly 40 GHz to 120 GHz. FIG. 4 illustrates the active reflection coefficient, comparing no scanning (BS) for an element in the array to when the element is driven to 45 degrees in the e plane (E45), or 45 degrees in the h plane of the antenna (H45), or 45 degrees in both planes (D45). FIG. 5 shows the active reflection coefficient, comparing no scanning (BS) for an element in the array to when the element is driven to 60 degrees in the e plane (E60), or 60 degrees in the h plane of the antenna (H60) or 60 degrees in both planes (D60). FIG. 6 shows the active reflection coefficient, comparing no scanning (BS) for an element in the array to when the element is driven to 75 degrees in the e plane (E75), or 75 degrees in the h plane of the antenna (H75) or 75 degrees in both planes (D75).
[0020] FIG. 7c shows a two-dimensional, 4-element by 4-element array 700 of dual-polarized differentially-fed shorted dipoles. The top view of the unit cell 710 that makes up the array 700 is shown in FIG. 7a. An isometric view of the unit cell 710 of the array 700 is shown in FIG. 7b. An isometric view of a representative 4×4 array 700 is shown in FIG. 7c. Arms 32 and 34 make up two halves of a first differentially-fed dipole element that is fed in polarization 1. Polarization 2 is orthogonal to polarization 1 and is fed by arms 40 and 42, which make up the two halves of a second differentially-fed dipole element. The shorted dipole elements that are oriented in the same direction as 32 and 34 throughout the array 700 also feed polarization 1. This polarization means that the electric field vectors for electromagnetic waves are oriented in the same direction as the long dimension of the physical components of arms 32 and 34 that are oriented parallel to ground plane 38. A coupling gap 46 may exist in the antenna array 700 between adjacent dipoles for Polarization 1, and a coupling gap 48 may exist in the array 700 between adjacent dipoles for Polarization 2. The phase center for the orthogonal polarizations associated with each unit cell is in the same location, because arms 32, 34 and arms 40, 42 are centered about the feed region, 36. Aperture 44 is the feed aperture for arm 34, but the whole feed region 36 could be a single aperture that allows all of the feeds from arms 32, 34, 40, 42 to pass through if the dimensions are too small to allow walls to exist between individual the dipole feeds.
[0021] FIG. 8c shows a two-dimensional, 4-element by 4-element array 800 of dual-polarized differentially-fed shorted dipoles. The top view of the unit cell 810 that makes up the array 800 is shown in FIG. 8a. An isometric view of the unit cell 810 of the array 800 is shown in FIG. 8b. An isometric view of a representative 4×4 array 800 is shown in FIG. 8c. Arms 50, 52 make up two halves of a differentially-fed dipole element that is fed in polarization 1. Polarization 2 is orthogonal to polarization 1 and is fed by arms 54, 56, which make up the two halves of a second differentially-fed dipole element. The shorted dipole elements that are oriented in the same direction as arms 50, 52 throughout the array 800 also feed polarization 1. This polarization means that the electric field vectors for electromagnetic waves are oriented in the same direction as the physical components of arms 50, 52 that are oriented parallel to ground plane 58. A coupling gap 64 may exist between the adjacent dipoles for both polarizations. These coupling gaps 64 could be simple, as shown in the drawing, or they could be interdigitated in such a way as to selectively couple between adjacent dipoles for a given polarization, FIGS. 10a, 10b. The phase center for each polarization is centered between the two dipole arms associated with said polarization and the two phase centers for each polarization are offset with respect to the other. Aperture 60 is a feed region for the differentially shorted dipole arms 54, 56. A separation wall 62 may or may not exist between the arms 54, 56. One may choose to use offset orthogonal elements, as shown in FIGS. 8a-8c, to make it easier to place the beam-forming electronics behind the array.
[0022] These and other advantages of the present invention will be apparent to those skilled in the art from the foregoing specification. For instance, a plurality of two-dimensional arrays, such as the arrays 200, 700, 800, may be combined to provide a three-dimensional array 900, FIG. 9. Accordingly, it will be recognized by those skilled in the art that changes or modifications may be made to the above-described embodiments without departing from the broad inventive concepts of the invention. It should therefore be understood that this invention is not limited to the particular embodiments described herein, but is intended to include all changes and modifications that are within the scope and spirit of the invention as set forth in the claims.
