Conformal antenna

Abstract

An antenna device is presented. The antenna device comprises: a conformal antenna body which has a desired geometry corresponding to a front portion of a platform on which the antenna device is to be mounted, and an antenna unit carried by the antenna body. The antenna unit comprises at least one phased array of antenna elements. The antenna elements of each array are arranged in a spaced-apart relationship in a closed loop path along a circumference of the antenna body having a desired geometry corresponding to a front portion of platform on which the antenna unit is to be mounted. Each of the antenna elements is configured as an end-fire antenna element capable of emitting linearly polarized radiation, the array of the antenna elements being thereby operable as a forward looking end-fire antenna array, enabling electronic steering of an antenna beam by controllably modifying phases of the antenna elements of each array.

Claims

1. An antenna device, comprising: a conformal antenna body which has a desired geometry corresponding to a front portion of a platform on which the antenna device is to be mounted; an antenna unit carried by the antenna body, the antenna unit comprising at least one phased array of antenna elements, the antenna elements of each phased array being arranged in a spaced-apart relationship in a closed loop path along a circumference of the antenna body having a desired geometry corresponding to a front portion of platform on which the antenna unit is to be mounted, each of the antenna elements is configured as an end-fire antenna element capable of emitting linearly polarized radiation, the array of the antenna elements being thereby operable as a forward looking end-fire antenna array; and a phase controller circuit configured and operable to control phases of all the antenna elements in each antenna array to provide a desired boresight of the antenna array in accordance with a selected radiation direction, thereby enabling electronic steering of an antenna beam produced by all the antenna elements of said at least one phased array by controllably modifying phases of the antenna elements of said at least one phased array.

2. The antenna device according to claim 1, wherein the antenna body has a substantially cylindrical shape, and the antenna unit is spaced a predetermined distance from a base region of the cylindrical antenna body.

3. The antenna device according to claim 1, wherein the antenna body has a substantially conical shape, and the antenna unit is spaced a predetermined distance from an apex region of the antenna body.

4. The antenna device according to claim 1, wherein the antenna body is configured as at least a part of a substantially spherical shape.

5. The antenna device according to claim 1, wherein the antenna body is made of a metallic material.

6. The antenna device according to claim 1, wherein the antenna elements in the antenna array are equally spaced from one another along said closed loop path.

7. The antenna device according to claim 1, wherein the antenna unit comprises two or more of the antenna arrays arranged in a spaced-apart relationship along the antenna body.

8. The antenna device according to claim 7, wherein the different antenna arrays have the same number of antenna elements.

9. The antenna device according to claim 7, wherein the antenna arrays comprise arrays having different number of antenna elements.

10. The antenna device according to claim 1, wherein the phase controller is configured and operable for providing a predetermined phase pattern of the antenna array resulting in a circular polarization of the antenna radiation of said antenna elements.

11. The antenna device according to claim 1, wherein the phase controller is configured and operable to control the phases of all the antenna elements in the antenna array such that the phases of the antenna elements in the array are shifted one with respect to the other along a circular direction, and each successive antenna element in said direction has a phase shifted by a predetermined value with respect to a preceding antenna element.

12. The antenna device according to claim 11, wherein the phase shift Δφ between each two successive antenna elements is determined as Δφ=2 π/n for the antenna array of n elements.

13. The antenna device according to claim 11, wherein said phase pattern corresponds to the antenna unit operation in a forward-looking direction.

14. The antenna device according to claim 1, wherein the phase controller is configured and operable to control the phases of all the antenna elements to be substantially the same, for each radiation direction in an angular range of up to 30 degrees of radiation directions.

15. The antenna device according to claim 1, wherein the phase controller is configured and operable to control the phases of all the antenna elements to be substantially the same, for each radiation direction in an angular range of 30 degrees or higher, for circular or arbitrary linear polarization of the antenna radiation.

16. An antenna device, comprising: a conformal antenna body which has a desired geometry corresponding to a front portion of a platform on which the antenna device is to be mounted; an antenna unit carried by the antenna body, the antenna unit comprising at least one phased array of antenna elements, the antenna elements of each array being arranged in a spaced-apart relationship in a closed loop path along a circumference of the antenna body having a desired geometry corresponding to a front portion of platform on which the antenna unit is to be mounted, each of the antenna elements is configured as an end-fire antenna element capable of emitting linearly polarized radiation, the array of the antenna elements being thereby operable as a forward looking end-fire antenna array; and a phase controller circuit configured and operable to control phases of all of the antenna elements in the antenna array providing a predetermined phase pattern of the antenna array resulting in a circular polarization of the antenna radiation of said antenna elements of said array, to provide a desired boresight of the antenna array in accordance with a selected radiation direction, thereby enabling electronic steering of an antenna beam by controllably modifying phases of the antenna elements of the array.

17. An antenna device, comprising: a conformal antenna body which has a desired geometry corresponding to a front portion of a platform on which the antenna device is to be mounted; an antenna unit carried by the antenna body, the antenna unit comprising at least one phased array of antenna elements, the antenna elements of said at least one phased array being arranged in a spaced-apart relationship in a closed loop path along a circumference of the antenna body having a desired geometry corresponding to a front portion of platform on which the antenna unit is to be mounted, each of the antenna elements is configured as an end-fire antenna element capable of emitting linearly polarized radiation, the array of the antenna elements being thereby operable as a forward looking end-fire antenna array; and a phase controller circuit configured and operable to control phases of all the antenna elements in each antenna array to provide a desired boresight of the phased array in accordance with a selected radiation direction, thereby enabling electronic steering of an antenna beam produced by all the antenna elements of said at least one phased array by controllably modifying phases of the antenna elements of said at least one phased array; wherein the phase controller is configured and operable to control the phases of all the antenna elements to be substantially the same, for each radiation direction in an angular range of up to 30 degrees of radiation directions.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In order to better understand the subject matter that is disclosed herein and to exemplify how it may be carried out in practice, embodiments will now be described, by way of non-limiting example only, with reference to the accompanying drawings, in which:

(2) FIGS. 1A and 1B schematically illustrate an example of an antenna device of the present invention;

(3) FIG. 2 is a schematic illustration of another possible example of an antenna device of the present invention;

(4) FIG. 3 schematically illustrates the principles of a phase shift technique utilized in the present invention for the antenna operation in forward-looking direction;

(5) FIGS. 4A-4B and 4C-4E exemplify simulation results for the performance of the antenna device of the invention utilizing an antenna unit configuration of FIG. 1, for respectively zero-degree and 10 degree angular orientations of the antenna boresight; and

(6) FIGS. 5A-5D exemplify simulation results for the performance of the antenna device of the invention utilizing an antenna unit configuration of FIG. 2 for zero-degree orientation of the antenna boresight.

DETAILED DESCRIPTION OF EMBODIMENTS

(7) Reference is made to FIGS. 1A-1B and 2 shown two specific but not limiting examples of an antenna device of the present invention utilizing two different configurations of the antenna unit. To facilitate illustration and understanding, the same reference numbers are used to indicate components that are common in all the examples of the invention.

(8) In both examples, the antenna device 10 includes a conformal antenna unit mounted on a supporting antenna body 14 having a curved surface corresponding to that of a platform on which the antenna device is to be mounted. In these examples, the antenna body 14 has a substantially conical geometry. It should, however, be understood that the invention is not limited to any specific geometry of the curved surface carrying the antenna unit, in which antenna elements are arranged in one or more circular antenna arrays, i.e. antenna elements are arranged in a spaced apart relationship along one or more closed-loop paths. FIG. 1A also includes a phase controller circuit PCC for controlling phases of all the antenna elements in each antenna array to provide a desired boresight of the antenna array in accordance with a selected radiation direction.

(9) The antenna device of the invention is particularly useful for placing on a front portion of a platform and is configured and operable for operating in a so-called “forward-looking mode”, namely having a general forward-looking radiation direction D with an ability to be electronically steered within a wide angular range around this general radiation direction. In the example of FIGS. 1A-1B the antenna unit 12 includes one phased array 18, and in the example of FIG. 2 the antenna unit 112 includes two phased arrays 18 and 118.

(10) It should be noted that the principles of the invention are not limited to a number of phased arrays of antenna elements, as well as are not limited to number(s) of the antenna elements in the array(s). Thus, generally, the antenna unit 12 may include m antenna arrays, m≥1, such that multiple antenna arrays are located in a spaced-apart relationship along the longitudinal axis of the body 14, and each of the antenna arrays includes multiple antenna elements located in a spaced-apart relationship along a circumferential path. In these specific examples, where the antenna body 14 has a conical geometry, the number of the elements in the arrays increases with the array's distance from a cone tip/apex 16. For example, the antenna array 18 (which is the single array in the example of FIGS. 1A-1B, and is the first array located closer to the tip portion 16 in the example of FIG. 2) has eight antenna elements AE.sub.1-AE.sub.8, and in the second antenna array 118 in the example of FIG. 2, located farer from the tip portion 16 includes sixteen antenna elements.

(11) The antenna elements of the same array are preferably equally spaced from one another. In case more than one antenna arrays are used, the distance between the antenna elements of one array may or may not be equal to the distance of the antenna elements in one or more other arrays. The number(s) of the antenna elements in the array(s) is/are selected in accordance with the dimensions and shape of the antenna body, i.e. of the platform, and frequency and gain requirements for the antenna operation. The antenna body may be a metallic body. The metallic tip portion 16 of the body contributes to the antenna radiation pattern. Such parameters as the longitudinal dimension a of the tip portion 16 (i.e. a distance of the antenna array from the tip of the antenna body), as well as a distance b between the antenna elements in the array, and possibly also a distance c between the antenna arrays, are selected/optimized in accordance with the frequency and gain requirements for the antenna operation. For example, when higher operational frequencies are to be used, the distance a may be lower than that preferred for lower operational frequencies of the antenna device.

(12) Each antenna element AE is an end-fire antenna element, whose boresight BS (shown in FIG. 1A), being the axis of maximum gain of the antenna element, is substantially parallel to the surface of the antenna element. Reference is now made to FIG. 3 schematically illustrating the structural and operational principles of the antenna array, e.g. array 18, for the forward-looking direction in the antenna unit of the invention. As known, the polarization components P of the radiation emitted by the antenna element are perpendicular to the boresight direction of the antenna element. Hence, in order to provide desired orientation of the boresight of the antenna array 18 (to provide desired directional operation of the antenna), while effectively utilizing the radiation emitted by all the antenna elements in the array (i.e. maximizing the performance) for each required direction, the phases of the antenna elements in the array are appropriately controlled.

(13) It should be understood, although not specifically illustrated, that the antenna device includes suitable phase shifters/controllers, and is associated with a control unit configured and operable to analyze input data about the operational direction and generate corresponding phase control data with respect to each antenna element in each array. The phase shifters utilize this control data to adjust the phases for the antenna elements. If the antenna operation with relatively small-angle steering, angular range of up to 30 degrees, is needed, the phases of all the elements in the array are controlled to be substantially the same for each direction within this angular range for circular polarization of the beam. For the antenna operation with relatively wide-angle steering, i.e. angular range of 30 degrees or higher, the phases of all the elements in the array are controlled to be substantially the same for each direction in this angular range for circular or arbitrary linear polarization of the beam.

(14) For substantially forward direction D, zero-steering from this direction, a phase, φ.sub.i+1, of each successive antenna element AE.sub.i+1 is shifted from the phase, φ.sub.I, of the preceding antenna element AE.sub.i in a direction along the circular path (as shown in FIG. 3) by the same value of the phase shift, Δφ=φ.sub.i−φ.sub.i+1, such that the antenna beam of the entire array 18 is of circular polarization. A phase shift Δφ between the phases of each two neighboring elements, considered as the successive elements in the direction along the circular path, in the array of n antenna elements is determined as Δφ=2 π/n. For example, for 8-element array 18, the phase shift Δφ is 45 degrees, and for the 16-elements array 118, the phase shift is 22.5 degrees.

(15) Reference is made to FIGS. 4A-4E and FIGS. 5A-5D illustrating simulation results for the performance of the antenna device according to the invention. Here, FIGS. 4A-4B and 4C-4E correspond to the antenna device utilizing an antenna unit configuration of FIG. 1; and FIGS. 5A-5B and 5C-5D correspond to the antenna device utilizing an antenna unit configuration of FIG. 2.

(16) More specifically, the simulation results illustrated in FIGS. 4A-4E correspond to the antenna unit configuration of FIG. 1 with the following parameters: the platform diameter of 4.2λ, the antenna element length and width of 4.4λ and 0.5λ respectively, and the distance a between the end of the of platform and the antenna unit (first array) of 2.1λ. The simulation illustrated in FIGS. 5A-5D correspond to the antenna unit configuration of FIG. 2 with the following parameters: the platform diameter of 3.8λ, the antenna element length and width of 1.2λ and 0.5λ respectively, the distance a between the end of the of platform and the antenna unit (first array) of 2.1λ, and the distance c between the first and second antenna arrays of 1.4λ.

(17) FIG. 4A exemplifies simulation of the antenna unit operation (in a receiving mode), and shows the sum signal pattern versus azimuth angle of a target (graph G.sub.1) and the azimuth difference signal pattern versus azimuth angle of a target (graph G.sub.2), in the azimuth plane, when the boresight angle is substantially zero, the antenna received signals have circular polarization. It should be understood that for the antenna operation in a transmitting mode, there is no such azimuth difference signal pattern vs azimuth angle, while the sum signal pattern vs azimuth angle is substantially the same as for the receiving mode operation. FIG. 4B illustrates the dependencies of the monopulse ratio on the azimuth angle obtained for the transceiver elements (antenna elements) of the array that receive signals having circular polarization, when the antenna boresight angle is zero degrees.

(18) FIG. 4C exemplify simulation for the sum signal pattern (graph G.sub.1) and the azimuth difference signal pattern (graph G.sub.2) in the azimuth plane versus azimuth angle of a target, when the boresight angle is 10 degrees and the received signal have circular polarization. FIG. 4D is a zoom on the specific angular segment of the graphs in FIG. 4C. FIG. 4E shows dependencies of the monopulse ratio on the azimuth angle obtained for the transceiver elements of the array that receive signals having circular polarization, when the antenna boresight angle is at 10 degrees orientation.

(19) FIGS. 5A and 5B show the sum signal pattern (graph H.sub.1) and the azimuth difference signal pattern (graph H.sub.2) in the azimuth plane versus azimuth angle of a target (FIG. 5A), and the dependencies of the monopulse ratio on the azimuth angle (FIG. 5B), for the circular polarization and the zero angle of boresight orientation. FIGS. 5C and 5D show similar results in the elevation plane, for the circular polarization and the zero angle of boresight orientation: FIG. 5C shows the sum signal pattern in the elevation plane versus elevation angle of a target (graph P.sub.1), and the elevation difference signal pattern in the elevation plane versus elevation angle of a target (graph P.sub.2), and FIG. 5D shows the dependencies of the monopulse ratio on the elevation angle.

(20) Thus, by using the above described configuration and operation of the antenna unit, all the antenna elements, as well as the radiating portion 16 of the antenna body, positively contribute to the antenna pattern in each selected radiation direction within the wide angular range of steering. The present invention advantageously provides for maximizing the performance of the conformal antenna for the forward-looking operation, with the electronic steering within the wide angular range (i.e. such that all the antenna elements contribute in the antenna pattern for each angular direction), for a wide frequency band. The antenna device can operate in high-temperature environmental conditions. The antenna can be incorporated in a metallic body. The antenna device of the present invention can be mounted on a small-diameter platform body. The antenna device of the invention may be used without a radome, which significantly simplifies the device configuration. The conformal antenna device of the present invention can be used in any communication and telemetric application, being mounted on a suitable platform.