Patent Publication Number: US-7218285-B2

Title: Metamaterial scanning lens antenna systems and methods

Description:
GOVERNMENT LICENSE RIGHTS 
   This invention was made with Government support under a U.S. government contract number: MDA972-01-2-0016. The Government has certain rights in this invention. 

   FIELD OF THE INVENTION 
   This invention relates to antennas, and, more particularly to more efficient and compact scanning lens antennas. 
   BACKGROUND OF THE INVENTION 
   High and medium gain antennas that can be scanned or can produce multiple simultaneous beams are needed for a variety of mobile communications and sensor applications. Typically, the mechanical or electronic systems required to scan the antenna or produce multiple beams are bulky, complex, and expensive. 
   Conventional scanning lens antennas use a dielectric lens to collimate the spherical wave from a small (low gain) radiator into a narrow beam (higher gain) plane wave. Shifting the location of the feed point of the radiator will scan the antenna beam over limited range of angles. Pattern quality is a function of the focal distance. A thin lens with a long focal length minimizes pattern distortions but will lose power due to spill over and will require a large rigid structure to support the lens and radiator. Shortening the focal distance requires a more complex series of lenses or results in spherical aberrations. 
   Therefore, there exists a need for a lens antenna that does not exhibit spherical aberrations, has minimal focal length and has a low level of complexity, thereby being cheaper to produce and implement. 
   SUMMARY OF THE INVENTION 
   The present invention is directed to systems and methods for radiating radar signals, communication signals, or other similar signals. In one embodiment, a system includes a controller that generates a control signal and an antenna coupled to the controller. The antenna includes a first component that generates at least one wave based on the generated control signal, and a metamaterial lens positioned at some predefined focal length from the first component. Metamaterial is a material that exhibits a negative index of refraction. A metamaterial with a negative index of refraction of n=−1 has the focusing power of an equivalent dielectric lens with n=3, based on the lensmaker equation, 
           f   =     1          n   -   1                  
The metamaterial lens directs at least one generated wave. Because the present invention uses a metamaterial lens with much larger focusing power, an antenna can be formed having a relatively small focal length, thereby allowing the antenna to be produced in a smaller overall package than conventional scanning lens antennas without requiring the additional complexity or exhibiting the usual amount of spherical aberrations.
 
   In accordance with further aspects of the invention, the system includes a user interface that is coupled to the controller. The user interface component allows a user to generate an instruction signal that the controller uses to generate the control signal. 
   In accordance with other aspects of the invention, the antenna further includes a sensor that senses waves received by the metamaterial lens. The sensor is coupled to the controller. The sensor may be a data storage device or an output device, such as a display. 
   In accordance with still further aspects of the invention, the antenna includes one or more actuators that receives at least a portion of the control signal from the controller and positions the first component or the metamaterial lens based on the received portion of the control signal. 
   In accordance with yet other aspects of the invention, the metamaterial lens includes a convex, concave, or gradient index lens. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The preferred and alternative embodiments of the present invention are described in detail below with reference to the following drawings. 
       FIG. 1  illustrates a block diagram of an exemplary system formed in accordance with an embodiment of the present invention; 
       FIGS. 2–4  illustrate side views of exemplary metamaterial lenses used as scanning antenna formed in accordance with embodiments of the present invention; and 
       FIGS. 5–7  illustrate portions of exemplary systems for using the lenses of  FIGS. 2–4  in a scanning lens antenna scenario. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   The present invention relates to antennas, and more specifically, to systems and methods for radiating radar signals, communication signals, or other similar signals. Many specific details of certain embodiments of the invention are set forth in the following description and in  FIGS. 1–7  to provide a thorough understanding of such embodiments. One skilled in the art, however, will understand that the present invention may have additional embodiments, or that the present invention may be practiced without several of the details described in the following description. 
     FIG. 1  illustrates a radar or communication system  20  for performing transmission and reception of signals. The system  20  includes an antenna  26 , a controller/processor  28 , an input/output device  30 , and a storage unit  32 . The controller processor  28  is operatively coupled to the antenna  26 , the input/output device  30 , and the storage unit  32 . 
   The controller processor  28  may be a radar or communications processor that converts signals for output by the antenna  26  as radar waves/communication signals or converts radar waves/communication signals received by the antenna  26  into data for output through the input/output device  30 . 
   Examples of the input/output device  30  include user interface devices such as mouse, keyboard, microphone, or any comparable control or data input device. Also, the input/output device  30  may include a display device, speakers, or other comparable device that outputs radar or communication data converted by the controller/processor  28 . 
   As further shown in  FIG. 1 , the antenna  26  includes a wave source/sensor  40  and a metamaterial lens  42 . The metamaterial lens  42  provides a focal length much smaller than that of traditional lenses. Thus, the wave source/sensor  40  is located closer to the lens  42  than in a conventional system, thereby allowing the antenna  26  to be packaged into a smaller unit than a traditional scanning antenna. Examples of metamaterial lenses  42  are described below with respect to  FIGS. 2–4 . 
   The term “metamaterial” is defined as negative-index-of-refraction materials. To produce a meta-material device a substrate material is provided and an array of electromagnetically reactive patterns of a conductive material are applied to a surface of the substrate material. Two of the substrate materials are joined together such that the surfaces bearing the electromagnetically reactive pattern are commonly oriented to form a substrate block. Each substrate block is sliced between elements of the array of electromagnetically reactive patterns in a plane perpendicular to a surface to which the electromagnetically reactive patterns were applied. An array of electromagnetically reactive patterns of a conductive material are applied to each surface of the substrate block. This is described in more detail in co-pending, commonly-owned U.S. patent application Ser. No. 10/356,934 filed Jan. 31, 2003, which is hereby incorporated by reference. 
   Referring to  FIG. 2 , a concave lens  60  formed of metamaterial is used as a collimating lens of waves produced by a wave source at points  64 . Similarly,  FIG. 3  illustrates a convex lens  70  formed with metamaterial for collimating waves produced at source points  74 . The metamaterial used in the lenses  60  and  70  has a negative index of refraction and responds to electromagnetic fields in a left-handed manner (i.e., negative permittivity and permeability), as described more fully in the above-referenced patent application. 
     FIGS. 4A and 4B  illustrate a thin slab lens  80  formed of a metamaterial to act as a gradient index lens, such as a Fresnel lens. In other words, the index of refraction varies away from the center point of the lens  80 . Thus, the lens  80  can act like a convex or concave lens at much less thickness. As shown in  FIG. 4A , the lens  80  acts as a collimator of waves produced by a source  82 . As shown in  FIG. 4B , the lens  80  acts as a collector of waves produced by sources  84 . 
   Referring now to  FIG. 5 , a first example system  88  is shown. A system  88  includes a metamaterial lens  90 , a wave source/sensor  92 , actuators  98 A–D, and a controller  96 . The actuators  98 A–D provide support and movement of the wave source/sensor  92 , and are controlled by signals from the controller  96 . The controller  96  also sends information to and from the storage unit  32  or the input/output device  30  ( FIG. 1 ). 
     FIG. 6  illustrates another embodiment of the present invention. In this embodiment, a system  99  includes a metamaterial lens  100  that directs signals produced by a source  102  as controlled by a controller  104 . The source  102  includes a switch  106 . The switch  106  is coupled to a plurality of feeds points at a predefined focal length from the lens  100 . The switch  106  receives instructions from the controller  104  and directs the generated wave to a desired feed point based on the instructions. In other words, the feed points are separately addressable by the switch  106 . Examples could be a array of PIN diodes patch antennas, dipoles, transmission lines, etc. 
     FIG. 7  illustrates another embodiment of the present invention. As shown in  FIG. 7 , a system  118  includes a metamaterial lens  120  that redirects a plurality of output waves produced by the source  122  as directed by the controller  124 . The source  122  includes a beam former  128  that simultaneously sends a plurality of wave forms to various feed points at a predefined focal length behind the lens  120 . In this embodiment, the system  118  is not a scanning antenna, but rather, may be any other suitable type of signal transmission and receiver system, including, for example, a set of PIN diodes that are on the ON state simultaneously thus enabling a multi-beam communication system. 
   The lenses  90 ,  100 , and  120  maybe any of the metamaterial lenses shown in  FIGS. 2–4  or any variation or combination of metamaterial based lenses. 
   Embodiments of systems and methods in accordance with the present invention may provide significant advantages over the prior art. For example, because systems in accordance with the present invention use a metamaterial lens, an antenna may be formed having a relatively small focal length in comparison with prior art systems. Thus, the antenna may be produced in a smaller overall package than conventional scanning lens antennas without requiring the additional complexity or exhibiting the usual amount of spherical aberrations. The resulting systems and methods may further have a low level of complexity, thereby being cheaper to produce and implement. 
   While preferred and alternate embodiments of the invention have been illustrated and described, as noted above, many changes can be made without departing from the spirit and scope of the invention. Accordingly, the scope of the invention is not limited by the disclosure of these preferred and alternate embodiments. Instead, the invention should be determined entirely by reference to the claims that follow.