Patent Publication Number: US-10309999-B2

Title: Compact test range system with adjustable feed horn locations

Description:
FIELD 
     The disclosed system and method relate to a compact test range system and, more particularly, to a compact test range system including a reflector and a feed horn, where a position of the feed horn is offset from a focus of the reflector in a vertical and a horizontal direction in a test position that corresponds to a unique field angle. 
     BACKGROUND 
     Various techniques currently exist for testing antennas or determining a radar cross section (RCS) of an object such as, for example, a small-scale aircraft. Far-field range testing involves placing a test article at a relatively long distance away from instrumentation. Since far-field range testing requires a large amount of space due to the long distances between the test article and the instrumentation, outdoor facilities are typically used. Compact ranges are an alternative to traditional far-field ranges. Any test that is capable of being accomplished on a far-field range may also be done using a compact test range. A compact range allows an operator to test indoors, thereby avoiding issues such as unfavorable weather conditions that are often encountered when testing outdoors. 
     In compact range testing, a horn antenna conveys radio waves towards a parabolic reflector. The horn antenna is often referred to as a feed horn. The feed horn is placed at the focus of the parabolic reflector. The reflector may be a portion of the parabola that is offset from the axis of the parabolic reflector. A radio wave originating at the feed horn may include an infinite number of rays that are reflected off of a surface of the reflector. The rays of the radio wave are reflected from the surface of the reflector are then directed towards the test article. The rays of the radio wave are reflected off of the surface of the reflector are each parallel to one another, and are aligned with a horizontal axis. Moreover, the rays of the radio wave define a path from the feed horn to the axis of the paraboloid, where each path of each ray is equal in length to the other remaining rays of the radio wave. Since the rays of the radio wave are horizontal, parallel, and equal in length with respect to one another, a flat phase front is created within the testing zone. The flat phase front is representative of far-field conditions. Therefore, although the testing zone is positioned at a near-field distance from the reflector, the compact range testing arrangement is capable of producing the flat phase front created in far-field testing. 
     Although compact range testing provides numerous advantages and benefits, there are still challenges that exist. Specifically, the test article is rotated during compact range testing to create a matrix of measurements. However, the test article needs to be re-positioned each time a measurement is collected. Therefore, compact range testing may be cumbersome and may also take a relatively long time to complete. 
     SUMMARY 
     In one example, a compact test range system for testing an article located within a test zone is disclosed. The system comprises a reflector defining a surface and a focus, a feed horn configured to emit a radio wave, one or more processors, and a memory coupled to the processor. The radio wave includes an infinite number of rays, where the rays of the radio wave include an uppermost ray, a middle ray, and a lowermost ray directed towards the surface of the reflector. The memory stores data comprising a database and program code that, when executed by processors, causes the compact range test system to receive as input a plurality of field tilt angles. In response to receiving the plurality of field tilt angles, the system determines three points of intersection between the uppermost ray, the middle ray, and the lowermost ray at a first field tilt angle, where the three points of intersection define a triangle. The system is also caused to determine a centroid of the triangle, and set the centroid of the triangle as a first test position of the feed horn. The first test position is offset in an x-direction and a y-direction from the focus of the reflector, and the first field tilt angle corresponds to the first test position. 
     In another example, a method for testing an article within a test zone by a compact test range system is disclosed. The method includes receiving, by a computer, a plurality of field tilt angles. The computer is in communication with a feed horn. The method further includes emitting, by the feed horn, radio waves. The radio wave includes an infinite number of rays, where the rays of the radio wave include an uppermost ray, a middle ray, and a lowermost ray directed towards the surface of the reflector. In response to receiving the plurality of field tilt angles, the method includes determining three points of intersection between the uppermost ray, the middle ray, and the lowermost ray at a first field tilt angle by the computer. The three points of intersection define a triangle. The method also includes determining, by the computer, a centroid of the triangle. Finally, the method includes setting the centroid of the triangle as a first test position of the feed horn. The first test position is offset in an x-direction and a y-direction from a focus of the reflector, and the first field tilt angle corresponds to the first test position. 
     Other objects and advantages of the disclosed method and system will be apparent from the following description, the accompanying drawings and the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an exemplary schematic diagram illustrating a side view of the disclosed system that includes a reflector and a feed horn, where the feed horn is located at a focus of the reflector and emits a radio wave including an infinite number of rays; 
         FIG. 2A  is one embodiment of the system shown in  FIG. 1 , where the feed horn is steered from the focus of the reflector and into a plurality of positions along a feed path rail; 
         FIG. 2B  is another embodiment of the system shown in  FIG. 1 , where multiple feed horns are provided and are activated one at a time; 
         FIG. 3  is an schematic diagram illustrating the system shown in  FIG. 1 , where a location of the feed horn (not illustrated) is offset in both a vertical and a horizontal plane and an imaginary line is drawn at a field tilt angle; 
         FIG. 4  is an enlarged view of Area A shown in  FIG. 3 , where a plurality of intersections between rays of the radio wave are illustrated; 
         FIG. 5  is an exemplary schematic diagram of the feed horn located at three different positions, where each position is based on a unique field tilt angle; and 
         FIG. 6  is a diagram of a computer system used in the embodiments shown in  FIGS. 1-5 . 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  is an exemplary schematic diagram illustrating a compact range testing system  10 . The system  10  is used to measure a test article (not illustrated in  FIG. 1 ). In one embodiment, the test article is an antenna. However, the test article is not limited to an antenna. Instead, the disclosed system  10  may be used to determine a radar cross section (RCS) of another object such as, for example, a conductive sphere or small-scale aircraft. The system  10  includes a control module  20 , a horn antenna or feed horn  22  and a reflector  24 . The reflector  24  may also be referred to as a main reflector. The feed horn  22  is configured to emit radio waves  28  towards a surface  26  defined by the main reflector  24 . As seen in  FIG. 1 , the radio wave  28  is illustrated as a plurality of rays. The surface  26  of the main reflector  24  is configured to reflect the rays of the radio wave  28  towards a test zone  30 . The test zone  30  contains the test article. 
     The radio wave  28  includes an infinite number of rays. However,  FIG. 1  illustrates the radio wave  28  including only five rays for purposes of clarity and simplicity. The rays of the radio wave  28  are reflected off of the surface  26  of the main reflector  24 . The rays of the radio wave  28  are substantially parallel and are spaced at equal horizontal distances with respect to one another in order to create a flat phase front  32  within the test zone  30 . In the embodiment as shown in  FIG. 1 , an imaginary line L is drawn that is normal to the rays of the radio wave  28  and parallel with a vertical or x-axis of the system  10 , and is located within the test zone  30 . The feed horn  22  is positioned at a focus F of the main reflector  24 . The flat phase front  32  includes rays of a uniform phase and of a uniform amplitude within the test zone  30 . As explained in greater detail below, during testing the feed horn  22  is offset from the focus F of the main reflector  24  in both the x-axis as well as a vertical or y-axis direction of the system  10 . 
       FIGS. 2A and 2B  illustrate two different approaches to offset the feed horn  22 , and  FIG. 3  illustrates the feed horn  22  offset in both the x-axis and y-axis direction. As seen in  FIG. 3 , the line L is now tilted at a field tilt angle θ. The field tilt angle θ is measured between the y-axis and the line L, where the line L is still normal with respect to the rays of the radio wave  28 . As seen in  FIG. 3 , the flat phase front  32  is maintained even as the feed horn  22  is steered or offset from the focus F of the main reflector  24  in the x-axis and the y-axis directions. During testing, the feed horn  22  is positioned into a plurality of test positions, where each test position is offset from the focus F of the main reflector  24  along both the x-axis and the y-axis. Each test position of the feed horn  22  corresponds to a unique field tilt angle θ. The field tilt angles θ are based on the particular type of testing to be performed by the system  10 . That is, a specific number of field tilt angles θ as well as values of the field tilt angles are based on the type of test performed by the system  10 . For example, some types of testing may only require three or four different measurements in a limited range, while some other types of testing may require many measurements that are taken along a wide span. 
       FIG. 2A  is one embodiment of the system  10  where the feed horn  22  is steered from the focus F into a plurality of positions  18   a ,  18   b ,  18   c  along a feed path rail  44  by an actuator  46 . The positions of the feed horn  22  are shown in phantom line along the feed path rail  44 . Although three positions are shown, the feed horn  22  may be positioned into any number of positions along the feed path rail  44 . Indeed, only three positions are illustrated in  FIG. 2A  for purposes of simplicity and clarity. 
       FIG. 2B  is an alternative embodiment of the system  10  where a plurality of feed horns  22   a ,  22   b ,  22   c  are provided and are each in communication with the control module  20  ( FIG. 1 ). As explained below, the feed horns  22   a ,  22   b ,  22   c  are activated one at a time by the control module  20 . Referring to  FIGS. 1, 2A, and 2B , the control module  20  is in communication with either the actuator  46  shown in  FIG. 2A  or the multiple feed horns  22   a ,  22   b ,  22   c  shown in  FIG. 2B . 
     Turning back to  FIG. 1 , the system  10  is illustrated as a prime-focus compact range testing system, and the feed horn  22  is a low gain feed horn. A low gain feed horn creates a broad beam width. Accordingly, the radio wave  28  emitted by the feed horn  22  includes a relatively broad beam width W. Specifically, the beam width W is defined by an uppermost ray R U  and a lowermost ray R L  defined by the radio wave  28 . A middle ray R M  is located between the uppermost ray R U  and the lowermost ray R L , where the middle ray R M  is equidistant between the uppermost ray R U  and the lowermost ray R L . Although a low gain feed horn is described, in an alternative embodiment the feed horn  22  is a high gain feed horn that produces a narrower beam width. Moreover, although  FIG. 1  only illustrates a single main reflector  24 , in another embodiment a second, sub-reflector may be used as well. For example, a shaped-Cassegrain dual-reflector configuration would include a main reflector, a sub-reflector, and a high gain feed horn. Furthermore, although a prime-focus compact range is disclosed in the figures, the disclosure may apply to other compact range configurations as well such as, but not limited to, a Gregorian dual-reflector, the shaped-Cassegrain dual-reflector, and a dual singly-curved reflector configuration. 
     The main reflector  24  is shaped as a portion or a section of paraboloid of revolution. The paraboloid of revolution defines the focus F. Since the main reflector  24  is shaped as a section of a paraboloid of revolution, the radio waves  28  that emanate from the feed horn  22 , which is located at the focus F, reflect off of the surface  26  of the reflector  24  as rays that are substantially parallel with respect to one another. Moreover, the rays of the radio wave  28  terminate at the line L and are all of equal length. 
     The testing of antennas and measurement of the RCS of an object requires that the antenna or object under test be illuminated by a uniform or flat phase front. During testing, a matrix of measurements representing a series of different positions of the test article is required. Conventional systems require that the test article be physically rotated in order to collect the required measurements. As explained in greater detail below, the disclosed feed horn  22  is offset from the focus F of the main reflector  24  in the x-axis and the y-axis direction during testing to collect the required measurements, and therefore the test article does not need to be physically rotated. 
     It is to be appreciated that if the main reflector  24  is only offset in vertical direction or the y-axis, then two issues occur. First, the rays of the radio wave  28  that reflect off of the surface  26  of the reflector  24  are not substantially parallel with respect to one another. Instead, the rays may diverge from one another. Moreover, the rays that reflect off of the surface  26  of the reflector  24  do not create a flat phrase front, thereby creating a less than ideal far-field condition. 
       FIG. 3  is an illustration of the system  10  in  FIG. 1 , where the feed horn  22  (not visible in  FIG. 2 ) is offset in both the x-axis and the y-axis direction from the focal F of the main reflector  24 , and the line L located within the test zone  30  is positioned at the field tilt angle θ. As seen in  FIG. 3 , the flat phase front  32  is maintained with respect to the field tilt angle θ. As explained below, the control module  20  determines the position of the feed horn  22  ( FIG. 1 ) offset from the focus F in both the x-axis and the y-axis direction. 
     The control module  20  ( FIG. 1 ) receives as input a plurality of field tilt angles θ. As mentioned above, the specific number of field tilt angles θ as well as values of the field tilt angles θ are based on the particular type of test performed by the system  10 . In response to receiving the field tilt angles θ, the control module  20  determines a test position for each of the field tilt angles θ. Each test position represents a location of the feed horn  22  offset from the focus F of the main reflector  24  along both the x-axis and the y-axis. Accordingly, each test position of the feed horn  22  corresponds to a unique field tilt angle θ. The position of the feed horn  22  is changed by either steering the feed horn  22  along the feed path rail  44  (shown in  FIG. 2A ). In the embodiment as shown in  FIG. 2B  the feed horns  22   a ,  22   b ,  22   c  are activated one-by-one based on a raster scan. 
     Continuing to refer to  FIG. 3 , the control module  20  ( FIG. 1 ) determines a first test position P 1  based on a first field tilt angle θ. It is to be appreciated that the approach described in  FIGS. 3, 4, and 5  below is repeated for each field tilt angle θ. As seen in  FIG. 3 , the test zone  30  is defined by a top point P H , a middle point P M , and a lower point P L , where the top point P H  is representative of the uppermost ray R U  of the radio wave  28  and the lower point P L  is representative of the lowermost ray R L  of the radio wave  28 . The middle point P M  is representative of a midpoint between the top point P H  and the lower point P L . 
     The points P H , P M , P L  each lie along the line L. The control module  20  ( FIG. 1 ) determines the line L based on Equation 1. The control module  20  also stores in memory Equation 2, which expresses the shape of the reflector&#39;s surface  26 :
 
 y−p   y =−tan(θ)( x−p   x )  (1)
 
 y   2 =4 fx   (2)
 
where p x  and p y  represent the x and y coordinates of either the top point P H , the middle point P M , and the lower point P L . For Equation 2, f is the focal point of a paraboloid that is rotated in order to create the paraboloid of revolution of the main reflector  24 , and x and y represent the points on the x-axis and the y-axis.
 
       FIG. 3  also illustrates ray reflection points RR H , RR M , and RR L  are located along the surface  26  of the reflector  24 . The ray reflection points RR H , RR M , and RR L  each correspond to either the top point P H , the middle point P M , and the lower point P L . The ray reflection points RR H , RR M , and RR L  each represent either the uppermost ray R U  reflecting off the surface  26 , the middle ray R M  reflecting off the surface  26 , or the lowermost ray R L  reflecting off the surface  26 . The top reflection point RR H , the middle reflection point RR M , and the lower reflection point RR L  are each expressed in x and y coordinates. Equation 3 expresses the x coordinate and Equation 4 expresses the y coordinate for the three reflection points RR H , RR M , RR L : 
     
       
         
           
             
               
                 
                   
                     r 
                     y 
                   
                   = 
                   
                     
                       
                         2 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         f 
                       
                       
                         tan 
                         ⁡ 
                         
                           ( 
                           θ 
                           ) 
                         
                       
                     
                     ⁡ 
                     
                       [ 
                       
                         
                           
                             
                               
                                 
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                                   x 
                                 
                                 ⁢ 
                                 
                                   
                                     tan 
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                                   ⁡ 
                                   
                                     ( 
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                               + 
                               
                                 
                                   p 
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                                   tan 
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                                     ( 
                                     θ 
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                               + 
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                             f 
                           
                         
                         - 
                         1 
                       
                       ] 
                     
                   
                 
               
               
                 
                   ( 
                   3 
                   ) 
                 
               
             
             
               
                 
                   
                     r 
                     x 
                   
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                         r 
                         y 
                         2 
                       
                       
                         4 
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                         f 
                       
                     
                     . 
                   
                 
               
               
                 
                   ( 
                   4 
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     Equation 5 expresses a unit-normal vector {circumflex over (n)} that is normal to the surface  26  of the main reflector  24  at one of the ray reflection points RR H , RR M , RR L . Equation 6 expresses an incident ray unit-vector î at one of the ray reflection points RR H , RR M , RR L : 
                     n   ^     =       1         4   ⁢           ⁢     f   2       +     r   y   2           ⁢     (       2   ⁢           ⁢   f   ⁢     x   ^       -       r   y     ⁢     y   ^         )               (   5   )                 i   ^     =         -     cos   ⁡     (   θ   )         ⁢     x   ^       +       sin   ⁡     (   θ   )       ⁢     y   ^                 (   6   )               
Equation 7 expresses a reflected ray unit-vector {circumflex over (v)} at one of the ray reflection points RR H , RR M , RR L , which is found in terms of the unit-normal vector {circumflex over (n)} and the incident ray unit-vector î, where:
 
 {circumflex over (v)}=î− 2( î·{circumflex over (n)} ) {circumflex over (n)}=v   x   {circumflex over (x)}+v   y   ŷ   (7)
 
A line through one of the ray reflection points RR H , RR M , RR L  and aligned with the reflected ray unit-vector {circumflex over (v)} is expressed in Equation 8 as
 
     
       
         
           
             
               
                 
                   
                     y 
                     - 
                     
                       r 
                       y 
                     
                   
                   = 
                   
                     s 
                     ⁡ 
                     
                       ( 
                       
                         x 
                         - 
                         
                           r 
                           x 
                         
                       
                       ) 
                     
                   
                 
               
               
                 
                   ( 
                   8 
                   ) 
                 
               
             
             
               
                 
                   
                     Where 
                     ⁢ 
                     
                       : 
                     
                     ⁢ 
                     
                         
                     
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                   = 
                   
                     
                       v 
                       y 
                     
                     
                       v 
                       x 
                     
                   
                 
               
               
                 
                     
                 
               
             
           
         
       
     
     Equations 9 and 10 express an intersection point Q: 
                     q   x     =         r     y   ⁢           ⁢   2       -     r     y   ⁢           ⁢   1       +       s   1     ⁢     r     x   ⁢           ⁢   1         -       s   2     ⁢     r     x   ⁢           ⁢   2               s   1     -     s   2                 (   9   )                 q   y     =           s   1     ⁢     r     y   ⁢           ⁢   2         -       s   2     ⁢     r     y   ⁢           ⁢   1         +       s   1     ⁢       s   2     ⁡     (       r     x   ⁢           ⁢   1       -     r     x   ⁢           ⁢   2         )               s   1     -     s   2                 (   10   )               
where q x  and q y  represent the x and y coordinates of the intersection point Q. The intersection point Q represents either an intersection point Q HM , an intersection point Q HL , or an intersection point Q ML , which are each illustrated in  FIG. 4  and are described in greater detail below. The intersection points Q HM , Q HL , Q ML  are used to determine the first test position P 1  of the feed horn  22  ( FIG. 1 ).
 
     Referring now to  FIG. 4 , an enlarged portion of Area A in  FIG. 3  is illustrated. Area A represents an area where the various rays of the radio wave  28  intersect one another. Referring to  FIGS. 3 and 4 , the various rays intersect one another within a plane in order to create a triangular profile or triangle T. The control module  20  determines three points of intersection between the uppermost ray R U , the middle ray R M , and the lowermost ray R L , where the three points of intersection define the triangle T. Specifically, the triangle T is defined by the intersection point Q HM , the intersection point Q HL , and the intersection point Q ML . The intersection point Q HM  represents an intersection between the uppermost ray R U  and the middle ray R M  of the radio wave  28 . The intersection point Q HL  represents an intersection point between the uppermost ray R U  and the lowermost ray R L  of the radio wave  28 . The intersection point Q ML  represents an intersection point between the middle ray R M  and the uppermost ray R U  of the radio wave  28 . 
     The control module  20  ( FIG. 1 ) then determines a centroid of the triangle T created by the intersecting rays. The centroid of the triangle T represents the first test position P 1  ( FIG. 3 ). Once the control module  20  determines the first test position P 1 , then the control module  20  determines another test position based on another field tilt angle θ. Turning now to  FIG. 5 , an exemplary schematic diagram illustrating three different test positions of the feed horn  22  along a feed path  58  is illustrated. A first position of the feed horn  22  is determined at a field tilt angle of about −10°, a second position of the feed horn  22  is determined at a field tilt angle of about 0°. The second position of the feed horn  22  is located at the focus F of the main reflector  24 . The third position of the feed horn  22  is determined at a field tilt angle of about 10°. Thus, the pitch angle of the exemplary system shown in  FIG. 5  is +/−10°. 
       FIG. 5  also illustrates only the middle ray R M  generated by the feed horn  22  at each of the three test positions. Accordingly, a front face  60  of the test zone  30  experiences three unique data points  62 ,  64 ,  66  that are collected by the middle ray R M  of the radio wave  28 . Referring now to  FIGS. 2A and 5 , in one embodiment the feed horn  22  is actuated into one of the first position, the second position, or the third position by steering the feed horn  22  along the feed path rail  44  by the actuator  46 . Referring now to  FIGS. 2B and 5 , in another embodiment the feed horns  22   a ,  22   b ,  22   c  are each positioned at a unique location, where each unique location is offset in both the x-direction and the y-direction from the focus F. The feed horns  22   a ,  22   b ,  22   c  are activated one by one or one at a time by the control module  20  (not shown in  FIG. 2B ). Specifically, the feed horns  22   a ,  22   b ,  22   c  are each activated for a very short amount of time such as, for example about 1 millisecond. In other words, each feed horn  22   a ,  22   b ,  22   c  are each activated one by one for a period of time. The period of time is short or brief enough such that activation of the plurality of feed horns  22   a ,  22   b ,  22   c  appears instantaneous to an ordinary observer. 
     If the test requires relatively few measurements, then the configuration as shown in  FIG. 2B  may be used. This is because a separate feed horn is required for each measurements. Thus, a test requiring hundreds of measurements would require just as many feed horns and would therefore be impractical. In one non-limiting example, if a test requires five or less measurements, then the configuration illustrated in  FIG. 2B  is used. 
     Referring generally to the figures, technical effects and benefits of the disclosed compact test range system include the ability to obtain multiple measurements of an antenna or another object without the need to physically rotate the test article. Instead, the feed horn is offset into one of a plurality of test positions, where each test position corresponds to a unique field tilt angle. The conventional approach to obtain multiple measurements during testing involves re-positioning the test article each time a measurement was collected. Thus, conventional compact range testing sometimes takes a relatively long time to complete. In contrast, the disclosed system allows for the test article to remain stationary, and instead controls the testing position of the feed horn. The disclosed approach may significantly reduce the amount of time required to perform certain types of testing. For example, one type of test that includes a relatively high data density may require about a week to test using the traditional approach of rotating the test object, but the disclosed compact range testing system only requires about a day of testing time. 
     Referring now to  FIG. 6 , the control module  20  in  FIG. 1  is implemented on one or more computer devices or systems, such as exemplary computer system  184 . The computer system  184  includes a processor  185 , a memory  186 , a mass storage memory device  188 , an input/output (I/O) interface  189 , and a Human Machine Interface (HMI)  190 . The computer system  184  is operatively coupled to one or more external resources  191  via a network  192  or I/O interface  189 . External resources may include, but are not limited to, servers, databases, mass storage devices, peripheral devices, cloud-based network services, or any other suitable computer resource that may be used by the computer system  184 . 
     The processor  185  includes one or more devices selected from microprocessors, micro-controllers, digital signal processors, microcomputers, central processing units, field programmable gate arrays, programmable logic devices, state machines, logic circuits, analog circuits, digital circuits, or any other devices that manipulate signals (analog or digital) based on operational instructions that are stored in the memory  186 . Memory  186  includes a single memory device or a plurality of memory devices including, but not limited to, read-only memory (ROM), random access memory (RAM), volatile memory, non-volatile memory, static random access memory (SRAM), dynamic random access memory (DRAM), flash memory, cache memory, or any other device capable of storing information. The mass storage memory device  188  includes data storage devices such as a hard drive, optical drive, tape drive, volatile or non-volatile solid state device, or any other device capable of storing information. 
     The processor  185  operates under the control of an operating system  194  that resides in memory  186 . The operating system  194  manages computer resources so that computer program code embodied as one or more computer software applications, such as an application  195  residing in memory  186 , has instructions executed by the processor  185 . In an alternative embodiment, the processor  185  executes the application  195  directly, in which case the operating system  194  may be omitted. One or more data structures  198  may also reside in memory  186 , and may be used by the processor  185 , operating system  194 , or application  195  to store or manipulate data. 
     The I/O interface  189  provides a machine interface that operatively couples the processor  185  to other devices and systems, such as the network  192  or external resource  191 . The application  195  thereby works cooperatively with the network  192  or external resource  191  by communicating via the I/O interface  189  to provide the various features, functions, applications, processes, or modules comprising embodiments of the invention. The application  195  has program code that is executed by one or more external resources  191 , or otherwise rely on functions or signals provided by other system or network components external to the computer system  184 . Indeed, given the nearly endless hardware and software configurations possible, persons having ordinary skill in the art will understand that embodiments of the invention may include applications that are located externally to the computer system  184 , distributed among multiple computers or other external resources  191 , or provided by computing resources (hardware and software) that are provided as a service over the network  192 , such as a cloud computing service. 
     The HMI  190  is operatively coupled to the processor  185  of computer system  184  in a known manner to allow a user to interact directly with the computer system  184 . The HMI  190  may include video or alphanumeric displays, a touch screen, a speaker, and any other suitable audio and visual indicators capable of providing data to the user. The HMI  190  may also include input devices and controls such as an alphanumeric keyboard, a pointing device, keypads, pushbuttons, control knobs, microphones, etc., capable of accepting commands or input from the user and transmitting the entered input to the processor  185 . 
     A database  196  resides on the mass storage memory device  188 , and may be used to collect and organize data used by the various systems and modules described herein. The database  196  may include data and supporting data structures that store and organize the data. In particular, the database  196  may be arranged with any database organization or structure including, but not limited to, a relational database, a hierarchical database, a network database, or combinations thereof. A database management system in the form of a computer software application executing as instructions on the processor  185  may be used to access the information or data stored in records of the database  196  in response to a query, where a query may be dynamically determined and executed by the operating system  194 , other applications  195 , or one or more modules. 
     While the forms of apparatus and methods herein described constitute preferred examples of this invention, it is to be understood that the invention is not limited to these precise forms of apparatus and methods, and the changes may be made therein without departing from the scope of the invention.