Abstract:
The present invention is directed to, in a first aspect, an antenna array stimulation system. In one embodiment the system comprises an array of radiating elements, a conductive layer adjacent the array of radiating elements adapted to receive electrical energy from, or couple electrical energy to, the array, and at least one connection device adapted to couple the electrical energy between the conductive layer and a test unit, wherein antenna performance degradation due to potential losses in coupling the energy between the conductive layer and the test unit are minimized.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention is generally related to antenna array systems and, more particularly, to a test system for an antenna array.  
           [0003]    2. Brief Description of Related Developments  
           [0004]    Antenna arrays are generally tested using source and reception devices that are located external to the antenna array. For example, the antenna array is placed on an antenna range and electrical and electromagnetic energy is transmitted to the array using a test source or received from the array. The test source is generally not part of the antenna system itself and can include its own antennas for radiating or receiving the test signals. This type of system does not allow for self-testing of the antenna array and tend to be large and cumbersome to use. A test range is generally a highly specialized and dedicated test facility.  
         SUMMARY OF THE INVENTION  
         [0005]    The present invention is directed to, in a first aspect, an antenna array stimulation system. In one embodiment the system comprises an array of radiating elements, a conductive layer adjacent the array of radiating elements adapted to receive electrical energy from, or couple electrical energy to, the array, and at least one connection device adapted to couple the electrical energy between the conductive layer and a test unit, wherein antenna performance degradation due to potential losses in coupling the energy between the conductive layer and the test unit are minimized.  
           [0006]    In another aspect, the present invention is directed to a method of testing an antenna array. In one embodiment, the method comprises the steps of coupling a test signal from a test source to a conductive layer of the antenna. The conductive layer comprises a series of conducting elements, each conducting element having an individual connection point for receiving or transmitting the test signal from the test source. The output of the array responsive to the test signal is monitored to determine a performance level of the array.  
           [0007]    In a further aspect, the present invention is directed to a built-in stimulator system for an antenna array. In one embodiment, the system comprises a polarizer device including a plurality of conductive elements arranged in a meandering pattern on the device. Each element is not electrically connected to another element. At least one impedance transformer electrically connected to each element and a coupler device adapted to electrically connect the impedance transformer to a test system and allow electrical signals to be passed between the polarizer and the test system.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]    The foregoing aspects and other features of the present invention are explained in the following description, taken in connection with the accompanying drawings, wherein:  
         [0009]    [0009]FIG. 1 is an elevational view of a system incorporating features of the present invention.  
         [0010]    [0010]FIG. 2 is an elevational view of an embodiment of a system incorporating features of the present invention using external transformers with a polarizer.  
         [0011]    [0011]FIG. 3 is an elevational view of an embodiment of a system incorporating features of the present invention using integrated transformers with a polarizer.  
         [0012]    [0012]FIG. 4 is an elevational view of an embodiment of a system incorporating features of the present invention using external transformers and a test coupler.  
         [0013]    [0013]FIG. 5 is an elevational view of an embodiment of a system incorporating features of the present invention using integrated transformers with a test coupler. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0014]    Referring to FIG. 1, there is shown an elevational view of a system  10  incorporating features of the present invention. Although the present invention will be described with reference to the embodiment shown in the drawings, it should be understood that the present invention can be embodied in many alternate forms of embodiments. In addition, any suitable size, shape or type of elements or materials could be used.  
         [0015]    As shown in FIG. 1, the system  10  generally comprises an antenna array  12 , a conducting layer or device  16  and a test signal connection device  20 . The system  10  is generally adapted to couple electrical energy received or transmitted by the antenna array  12  to a test system  80  in order to test the behavior and performance of the antenna array  12 . In an alternate embodiment the system  10  could include such other suitable components for built-in stimulation of an antenna array. It is a feature of the present invention to test polarized antenna arrays without the use of external radiating test equipment.  
         [0016]    The antenna array  12  generally comprises an array or series of radiators  14 , or smaller antennas. Generally any suitable antenna array  12  can be used and the user&#39;s design or application only limits the choice of antenna array.  
         [0017]    The conducting layer or device  16  generally comprises a sheet of electrically conducting material that can be placed over the array  12  and is designed to work in conjunction with the array of radiators  14  to generate polarized energy in the direction to which the array  12  is pointed or oriented. The conducting layer  16  can include one or more elements or strips  18  of an electrically conductive material, such as for example, metal. The elements  18  can be positioned on, or embedded in, any suitable medium, such as for example, a dielectric material. In one embodiment, the conductive layer  16  can comprise a sheet of printed circuit material with thin strips of conductive elements  18  affixed thereon. In an alternative embodiment, the conductive layer  16  can be designed in any suitable manner that allows polarized energy to be radiated to or received from the direction to which the array  12  is pointed.  
         [0018]    Referring to FIG. 1, the test connection device  20  generally comprises a mechanism or device adapted to couple or connect the conductive layer  16  to the test source  80 . Although only one test connection device  20  is shown in FIG. 1, it will be understood by those of skill in the art that one or more test connection devices  20  can be used if the elements  18  are individual lines and are not electrically connected or coupled together or that the array of radiators  14  cannot be accessed by a single element  18 . The test connection device  20  is generally adapted to couple a test signal  22  either being inputted into the elements  18  of the conducting layer  16  from the test source, or couple energy  82  coming from the conducting layer  16  in response to a radiated test signal  24  received by the array  12 . In one embodiment, the test connection device  20  can comprise a impedance transformer that is adapted to convert the impedance that is useful for the test source or equipment. In an alternate embodiment, any suitable connection device can be used that allows a test signal  22  to be inputted to the conducting layer  16  from the test source  80 , or allows electrical energy from a signal received by the conducting layer  16  to be transmitted back to the test source  80 , shown as signal  82 . It is a feature of the present invention to prevent or minimize antenna performance degradation due to the test connection  20  and related connections.  
         [0019]    The system  10  can also include a test interface point  26  adapted to couple the test connection device  20  to one or more of the elements  18  of the conductive layer  16 . In one embodiment, as shown in FIG. 1, the conducting layer  16  includes a test interface point  26  that couples or electrically connects each of the lines  18  together. In an alternate embodiment, as shown for example in FIG. 2, a separate test interface point  26  can be used for each line  18 , resulting in a plurality of test interface points  26 , where each element  18  is not coupled to another element  18 . Generally, the test interface point  26  is chosen so as to maximize the number of signal pathways through the antenna array  14 . In this fashion, each connection point  26  and corresponding line  18  can be energized individually or monitored to determine how well the array  12  is working.  
         [0020]    A test signal connection port  30  can be used to couple the test source  80  to the test connection device  20 . The test connection port  30  can comprise any suitable electrical connection device that can be used to couple an electrical signal from one point to another point with minimal loss and signal degradation.  
         [0021]    Referring to FIGS. 2 and 3, in one embodiment, the conducting layer  16  comprises a polarizer device  36 . Preferably, the polarizer  36  comprises a meanderline polarizer with a series of rows of patterns of conductive elements  38 . In one embodiment, the rows can run in a diagonal manner across the polarizer  36 , but any suitable direction and pattern can be used. Generally, it is preferred that each conductive element  18  is not connected to another one of the elements  18  on the polarizer  36 . Each element  18  can be a separate line. The polarizer  36  is generally designed and adapted so that it can be positioned adjacent to, or on top of, the array  12 . If needed, a suitable distance between the array  12  and polarizer  36  can be incorporated into the design. The polarizer  36  should be positioned so that polarization of energy received from the array  12  or transmitted to the array  12  is achieved. In an alternate embodiment, any suitable polarizer can be used that can be located adjacent to or near the array  12  and manipulate the electromagnetic energy or signals received from the array  12  or electrical signals transmitted to the array  12 . It is a feature of the present invention that the polarizer  36  be an inherent or permanent part of the system  10  design so that the array  12  can be tested in its final application and environment without the need for external stimulation equipment.  
         [0022]    As shown in FIGS. 4 and 5, in an alternate embodiment, the conductive layer  16  can comprise a test coupler device  46 . The test coupler device  46  can include a series of conductive metal strips  48  on, or embedded in, a dielectric material, for example. The test coupler device  46  is generally adapted to be removable from the array  12 . Alternatively, the test coupler device is not removable. It is a feature of the present invention that the test coupler device is not used in the final application, but generally only for testing of the array prior to the final application and environment of the array. Although as shown in FIGS. 4 and 5, the elements  48  are shown as straight lines, it will be understood by those of skill in the art that any suitable pattern can be used, such as for example meandering lines, a zig zag pattern, or an alternating or high-low pattern.  
         [0023]    Referring to FIGS. 2 and 4, in one embodiment, the test connection devices  20  include a plurality of impedance transformers  44  that are mounted or located external to the polarizer device  36  and test coupler device  32 , respectively. In alternate embodiments, such as that shown for example in FIGS. 3 and 5, the test connection devices  20  can include impedance transformers  40  that are embedded in, or located internal to the polarizer device  36  or test coupler device  32 , respectively.  
         [0024]    In operation, the system  10  provides for built-in test (“BIT”) stimulation of the antenna array  12 . The polarizer layer  36  is an inherent point of the design of the antenna array  12  and allows for the antenna and related equipment to be tested in-situ. Generally, a test signal  22 ,  24  is injected or coupled to the polarizer layer  36 . A test source can be used to inject a test signal  22  into the polarizer  36  via the test signal port  30 . Although one or more test signal ports can be used, single injection may be used depending on the array or sub-array  12  configuration to provide stimulation to all key elements  18  of the polarizer  36 . Similarly, energy, or a radiated test signal  24 , can be received by the array  12  and the polarizer  36  can receive electrical energy or radiation from the array  12 . The energy coupled to the polarizer  36  can be transmitted back to the test source through the test signal ports  30  for evaluation. The system  10  can utilize an existing antenna design feature for generation of the test signal  22 . This provides a built-in feature that is inherently part of the antenna design. In this manner, degradation of the antenna performance can be minimized.  
         [0025]    The system  10  generally provides in-situ stimulation of an antenna array  12 . Test performance and health measurements can be evaluated without the need for external radiating test equipment, such as for example, hats and probes. There is generally no degradation to polarizer performance. The system  10  can generally comprises a passive circuit, no bias, and does not need to contain any active devices. The system  10  can be mechanically rugged and safe to electrostatic discharge (“ESD”).  
         [0026]    It should be understood that the foregoing description is only illustrative of the invention. Various alternatives and modifications can be devised by those skilled in the art without departing from the invention. Accordingly, the present invention is intended to embrace all such alternatives, modifications and variances that fall within the scope of the appended claims.