Abstract:
An antenna device with a system for automatic stabilization and positioning control. The antenna device incorporates micro-electromechanical (MEMs)-based accelerometer and gyroscopic integrated circuit (IC) sensors directly into the antenna base in a vehicle-mounted antenna application. The sensors enable the antenna device to automatically stabilize the antenna to achieve a desired beam sweep region, independent of vehicle movement, without requiring external sensor input. The invention eliminates the need for a communication interface to externally mounted orientation sensors, reduces cable I/O, and eases the installation procedure.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    A vehicle-mounted antenna typically requires stabilization in order to keep the antenna device facing a specified direction, or tracing a specified sweep region, independent of the movements of the vehicle on which it is mounted. This requirement dictates that such an antenna receive input from at least one orientation sensor, so that the antenna can respond to changes in vehicle orientation. 
         [0002]    Orientation sensors often consist of some combination of accelerometers and gyroscopes. Due to size and weight constraints, these sensing devices are typically mounted on the vehicle in a location physically remote from the antenna unit itself. As a result, typically there must be a physical electrical connection and coordinated communication protocol between the orientation sensors and the antenna to convey to the antenna unit orientation information. 
         [0003]    There are several negative consequences of this design. One is the need to match the communication protocols of the antenna and the orientation sensors. Because at the time of design and manufacture it is not necessarily known to what orientation sensors the antenna will be connected, antennas are often designed to accept many different communication protocols. This adds to unit complexity and design/development costs. 
         [0004]    A second consequence is the need to match the physical I/O port. This requirement dictates that antennas be built either to accept multiple I/O port configurations, or be restricted in the number of orientation sensors with which the antenna can be used. 
         [0005]    Finally, having the antenna and the orientation sensors physically separated means that a precise calibration must occur during their installation in order to ensure that the antenna base and the vehicle share the same orientation. 
       SUMMARY OF THE INVENTION 
       [0006]    An antenna device with a system for automatic stabilization and positioning control is disclosed. The antenna device incorporates micro-electromechanical sensor (MEMs)-based accelerometer and gyroscopic integrated circuit (IC) sensors directly into the antenna base in a vehicle-mounted antenna application. The sensors enable the antenna device to automatically stabilize the antenna to achieve a desired beam sweep region, independent of vehicle movement, without requiring external orientation sensor input. 
         [0007]    The invention takes advantage of the increasing capability and decreasing size and cost of MEMS devices. In the specific application of a weather radar antenna mounted in an aircraft, the MEMS devices enable orientation sensors integral with the antenna, with the effect of reducing communication protocol complexity, reducing wiring and physical interfaces, and simplifying antenna installation. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    Preferred and alternative embodiments of the present invention are described in detail below with reference to the following drawings: 
           [0009]      FIG. 1  illustrates a partial x-ray view of an aircraft having a self-stabilizing antenna formed in accordance with an embodiment of the present invention; 
           [0010]      FIG. 2  illustrates a block diagram showing the components of a self-stabilizing antenna; and 
           [0011]      FIG. 3  is a perspective drawing illustrating a vehicle-mounted self-stabilizing weather radar antenna. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0012]      FIG. 1  shows a vehicle  10  having a nose section  12  and a structural element  16 . To the structural element  16  is fastened an antenna device  18  which during operation surveys a beam sweep region  14 . Because electromagnetic radiation can penetrate physical bodies, the structural element  16  and the mounting point of the antenna device  18  could occur at any point on or within the vehicle  10 . The nose section  12  is just one of several convenient locations within vehicle  10  where the antenna device  18  could be conveniently mounted. 
         [0013]    During a normal horizontal scanning process, the antenna device  18  seeks to maintain an orientation that maintains a specified beam sweep region  14 . Because antenna device  18  is mounted to structural element  16 , and therefore fastened to vehicle  10 , when the orientation of vehicle  10  changes, so does the beam sweep region  14  from which the antenna device  18  collects electromagnetic fields. This consequence leads to the need for stabilization of the antenna device  18 . 
         [0014]      FIG. 2  shows the relationship between functional components of the antenna device  18 . The antenna device  18  includes a base  20 , an antenna  22 , a control device  34  and a display memory device  36 . Within base  20  are orientation motors  24 , micro-electromechanical sensor (MEMS)-based orientation sensors  26 , a processor  28 , a data input/output port  30  and a transmit/receive circuit  32 . 
         [0015]    The base  20  serves as both a mechanical and electrical connection point between the antenna  22  and the remotely located control device  34  and display memory  36 . Mechanically, referring back to  FIG. 1 , the base  20  is fixed to the structural element  16 , and therefore to the rest of the vehicle  10 . In  FIG. 2 , the antenna  22  is connected to the base  20  through mechanical linkages (not shown) at the orientation motors  24 . The MEMs-based orientation sensors  26  are mechanically referenced to the orientation motors  24  through their common mounting point, base  20 . 
         [0016]    The antenna  22  is in signal communication with the processor  28  through transmit/receive circuitry  32 . The control device  34  and display memory  36  are in signal communication with the processor  28  through the data input/output port  30 . Both the orientation motors  24  and the MEMS-based orientation sensors  26  are in direct, signal communication with the processor  28 . 
         [0017]    In operation, specification of the desired sweep region  14  (i.e. a directional signal) is conveyed to the processor  28  from the control device  34  through the data input/output port  30 . But because the base  20  is connected through the structural element  16  to the vehicle  10 , as the vehicle  10  travels through space the orientation of the antenna  22  varies in terms of roll and pitch. By its mechanical connection to the base  20 , the MEMS-based orientation sensors  26  measure the parameters of roll and pitch experienced by the base  20  (i.e., the vehicle  10  (e.g., aircraft)), and continuously feeds the results of these measurements to the processor  28 . The processor  28  receives the specification of the desired beam sweep region  14  from the control device  34  and the measurements of roll and pitch from the orientation sensors  26 . In the processor  28 , the measurements of roll and pitch from the orientation sensors  26  are factored into the specification of the desired beam sweep region  14  from the control device  34  and are forwarded to the orientation motors  24 . Through conventional mechanical linkage (not shown) the orientation motors  24  direct the antenna  22  to achieve the beam sweep region  14  specified at the control device  34  despite changes in the orientation of the base  20  to which it is mounted. For the desired beam sweep region  14 , the antenna  22  captures and collects the desired electromagnetic radiation field and passes it through the transmit/receive circuitry  32  to the processor  28 , and from there through the data input/output port  30  to the display memory  36 . 
         [0018]    In other words, the processor  28  has knowledge of the antenna position in the horizontal scan plane as part of the horizontal scan drive processing. In the processor  28 , measurements of roll and pitch from the orientation sensors  26  and the position within the horizontal scan are factored with the scan elevation specified by the control device  34  to provide a pitch and/or roll compensated modification to accomplish the desired beam sweep region  14 . 
         [0019]    In one embodiment, the base  20 , the antenna  22 , the control device  34 , and the display memory  36  make up an aircraft-mounted weather-radar antenna device  18 . The vehicle  10  is an aircraft with the antenna device  18  mounted to the structural element  16  in the nose section  12 . The vehicle  10  passes through the atmosphere with the antenna  22  directed outward from the nose section  12  to establish the desired beam sweep region  14 . Information about the weather is collected by the antenna  22  and passed through the transmit/receive circuit  32  to the processor  28 . As vehicle attitude changes, the MEMS-based orientation sensors  26  measure the deviation from a previous orientation, and transmit the difference in orientation between the old and new orientations back to the processor  28 . The processor  28  passes this new orientation information to the orientation motors  24 , which respond mechanically to adjust the antenna  22  in order to maintain the beam sweep region  14  specified at the control device  34 . 
         [0020]    Orientation adjustments of the antenna  22  due to movements in the vehicle  10  are achieved without any input from outside the base  20  once specification of the desired beam sweep region  14  is received from the control device  34 . There is no requirement for input to the orientation measurements from orientation sensors external to the antenna device  18 . This simplifies the cabling and physical interface requirements at the data input/output port  30 . 
         [0021]    Integration of the MEMS-based orientation sensors  26  within the base  20  eliminates the requirement for multiple communication protocols to be installed in the processor  28 . This is a step forward from current antenna device processors, which must be configured with a variety of communication protocols in order to accommodate the range of orientation sensors to which they could be connected, or are limited in the orientation sensors with which the antenna device can be used. 
         [0022]    Integration of the MEMS-based orientation sensors  26  within the base  20  also eliminates a previously required calibration at the time of installation. The calibration requirement comes from the need for: (1) the antenna base  20  and the vehicle  10  to share the same orientation coordinates, so that the output of the heretofore remotely located orientations sensors is meaningful to the antenna base  20 , and (2) the orientation motors  24  and the vehicle  10  to share the same orientation coordinates, so that the orientation of the beam sweep region  14  corresponds with the vehicle  10  orientation. The benefit of integrating the orientation sensors  26  into the base  20  is that the first calibration requirement is entirely eliminated, and the second calibration requirement can be satisfied by a factory calibration, rather than one at the time of antenna device  18  installation. 
         [0023]      FIG. 3  shows an embodiment of an antenna device  18 - 1  mounted to a bulkhead  16 - 1  of a nose cone section of an aircraft. The base  20  is mounted to the structural element  16  and the antenna  22  is connected to the base  20  through a linkage (not specifically shown) to the orientation motors  24 . Within the base  20  are the orientation motors  24 , the MEMS-based orientation sensors  26 , the processor  28 , the data input/output port  30  and the transmit/receive circuitry  32 . The orientation motors  24 , the MEMS-based orientation sensors  26 , the processor  28 , the data input/output port  30  and the transmit/receive circuitry  32  are all integrated within the base  20 . 
         [0024]      FIG. 3  also shows that the base  20  exists as a common mechanical reference point for both the orientation motors  24  and the MEMS-based orientation sensors  26 . This enables these two components to be factory calibrated to one another, a periphery benefit to the invention of the self-stabilizing antenna device  18 .  FIG. 3  also shows the compact data input/output port  30  which contains no I/O pins for the orientation sensors  26 , because the orientation sensors  26  are integrated into the base  20  with the processor  28 . This reduces the cable count in the data input/output port  30 , which now requires pins for connection only to the control device  34  and display memory  36 . Not visible in  FIG. 3  is the simplification of the processor  28  due to the elimination of multiple communication protocols for communicating between the orientation sensors  26  and the processor  28 . 
         [0025]    In one embodiment, the MEMS accelerometers and MEMS gyroscopes are made by Honeywell, Inc., including the Air Data Attitude Heading Reference System (ADAHRS) used in the Apex integrated cockpit. In alternative embodiments, commercial off-the-shelf suppliers of MEMS accelerometers and MEMS gyroscopes are used. 
         [0026]    In embodiments requiring extreme accuracy, the orientation sensors  26  include up to three rotational (gyroscopic) MEMS integrated circuits and four accelerometer integrated circuits (IC&#39;s). Accelerometer IC packages exist that measure three axes in one package, and since antenna stabilization typically must account for only two axes of rotation, it is conceivable that self-stabilization could be accomplished with as few as three ICs (one three-axis accelerometer MEMS IC and two one-axis rotational MEMS ICs). In one embodiment, a three-axis accelerometer MEMS IC and two one-axis rotational MEMS ICs package is installed in the antenna base  20 . Using one of a number of accepted communication protocols, each IC package transmits orientation data to the processor  28 . Based on the received orientation data, and the specified beam sweep region  14  from the control device  34 , the processor  28  commands the orientation motors  24  to adjust the antenna  22  to maintain the requested beam sweep region  14  independent of the orientation of the vehicle  10 . 
         [0027]    In another embodiment, the transmit/receive circuit  32  includes a transmitter and a receiver and the processor  28  includes a radar processor. The transmitter, receiver and radar processor may be similar to those provided in the RDR4000 weather radar system produced by Honeywell, Inc. 
         [0028]    While the preferred embodiment of the invention has been illustrated and described, as noted above, many changes can be made without departing from the spirit and scope of the invention. For example, using alternatively fabricated orientation measurement sensors is still considered within the invention disclosed here. Accordingly, the scope of the invention is not limited by the disclosure of the preferred embodiment. Instead, the invention should be determined entirely by reference to the claims that follow.