Abstract:
In one embodiment a communications system includes an unmanned vehicle and a communications station located remote from the unmanned vehicle. The unmanned vehicle has a first wireless communications system and a first directional antenna for wirelessly communicating with the remote communications station. A first antenna control system tracks the remote communications station and aims the first directional antenna, in real time, at the remote communications station during wireless communications with the remote communications station. The remote communications station has a second wireless communications system having a second directional antenna for wirelessly communicating with the unmanned vehicle. A second antenna control system of the remote communications station tracks the unmanned vehicle and aims the second directional antenna at the unmanned vehicle, in real time, during wireless communications with the unmanned vehicle.

Description:
FIELD 
     The present disclosure relates to the operation of unmanned vehicles, and more particularly to a system and method for optimizing the RF telemetry capability of a UAV. 
     BACKGROUND 
     The statements in this section merely provide background information related to the present disclosure and may not constitute prior art. 
     Unmanned Aerial Vehicles (UAVs), alternatively Unmanned Air Vehicles, are growing in importance for both military and non-military applications. UAVs typically make use of an on-board antenna, and more typically an omnidirectional on-board antenna, to wirelessly transmit information back to a ground station or base station. Typically, extra power is used to transmit Radio Frequency (RF) signals from the UAV beyond what might otherwise be needed because of various factors that might negatively influence the integrity of the RF link between the base station and the UAV. Such factors could be the changing attitude of the UAV as it flies, or possibly topographic obstructions, or even localized weather conditions (e.g., thunderstorms), that can be expected to significantly degrade the RF link between the UAV and the base station. For this reason, the transmit power used for the RF transmitter is set to a value that, during many times of use of the UAV, will be significantly more than what is needed. This factor limits the range of the UAV because excess electrical power from the UAV&#39;s on-board battery will be utilized by the on-board RF system during a given mission or operation. 
     The need to use extra power with an omnidirectional antenna on a UAV also gives rise to another, sometimes undesirable feature, and that is the detectability of the UAV (or interception of RF communications radiated from it) by other electronic detection systems. The use of an omnidirectional antenna broadcasts the RF signals transmitted by the UAV in an omnidirectional pattern that may facilitate radio-location of the vehicle and/or interception of communications. 
     SUMMARY 
     In one embodiment the system comprises an unmanned vehicle and a communications station located remote from the unmanned vehicle. The unmanned vehicle may include a first wireless communications system and a first directional antenna for wirelessly communicating with the remote communications station. A first antenna control system on the unmanned vehicle tracks the remote communications station and aims the first directional antenna, in real time, at the remote communications station during wireless communications with the remote communications station. The remote communications station may include a second wireless communications system and a second directional antenna for wirelessly communicating with the unmanned vehicle, and a second antenna control system that tracks the unmanned vehicle and aims the directional antenna at the unmanned vehicle, in real time, during wireless communications with the unmanned vehicle. 
     In another aspect of the present disclosure an unmanned vehicle is disclosed. The unmanned vehicle comprises a wireless communications system and a directional antenna for facilitating wireless communications with a remote subsystem. An antenna control system is included that aims the directional antenna to track the remote subsystem during wireless communications with the remote subsystem. 
     In another aspect of the present disclosure a base station for wirelessly communicating with a remote mobile vehicle is disclosed. The base station includes a wireless communications system and a directional antenna for wirelessly communicating with the remote mobile vehicle. An antenna control system is included that tracks the remote mobile vehicle and maintains the second directional antenna aimed at the remote mobile vehicle during wireless communications with the remote mobile vehicle. 
     In another aspect of the present disclosure a method for communicating between a moving unmanned vehicle and a remote communications station is disclosed. The method may include using an unmanned vehicle to wirelessly communicate with the remote communications station and controlling a first directional antenna of the unmanned vehicle such that the first directional antenna tracks the remote communications station in real time. A second directional antenna is used at the remote communications station to track the unmanned vehicle in real time. 
     In still another aspect of the present disclosure a method for wirelessly communicating with an unmanned vehicle is disclosed. The method may comprise using a directional antenna on the unmanned vehicle for facilitating wireless communications with a remote subsystem. An antenna control system on the unmanned vehicle may be used to aim the directional antenna to track the remote subsystem during wireless communications with the remote subsystem. 
     Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. 
         FIG. 1  is a high level block diagram of an overall system in accordance with one embodiment of the present disclosure; and 
         FIG. 2  is a flowchart illustrating major operations performed by the system of  FIG. 1  when communicating between an unmanned vehicle and a remote communications station. 
     
    
    
     DETAILED DESCRIPTION 
     The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. 
     Referring to  FIG. 1 , there is shown a communications system  10  for enabling communications between an unmanned vehicle  12  and a remote communications station  14 . In this example the unmanned vehicle is shown as an unmanned aerial/air vehicle (hereafter referred to as a “UAV”), although it will be appreciated that the present disclosure could just as readily be employed with land vehicles or marine vessels. Thus, the following discussion and claims will be understood as encompassing any type of mobile vehicle, whether of the airborne, land-based or sea-based type. Similarly, the communications station  14  is shown as a non-moving, terrestrial based communications station located on the Earth  16 , and may be thought of as a “base” station. However, the communications station  14  could be located on some form of mobile platform as well, and therefore need not be stationary. Both implementations are contemplated by the present disclosure. 
     The UAV  12  includes an electromagnetic wave (i.e., wireless) communications system  18 , which for convenience will be referred to as the “RF communications system”. The UAV  12  also includes an antenna control system  20  that is used to aim a directional antenna  22  at desired elevation and azimuth angles needed to track the communications station  14 . A servo motor system  20   a  including one or more servo motors may be used for this purpose to control the elevation and azimuth positioning of the directional antenna  22 . A battery  24  provides electrical power for the RF communications system  12  and other electrically powered components of the UAV  12 . The communications station  14  similarly includes a wireless communications system  26  (hereinafter simply the “RF communications system”), an antenna control system  28 , a directional antenna  30 , and optionally a network  32 , such as a wide area network (WAN) or a local area network (LAN), for communicating information between the systems  26  and  28  and the antenna  30 . 
     Each of the directional antennas  22  and  30  may comprise mechanically scanned reflector antennas or phased array antennas. Any type of antenna that can electrically or mechanically aim a directional beam at the communications station  14  is contemplated by the present disclosure. Similarly, while it is expected that electromagnetic wave transmissions may be the medium that is typically used with the system  10 , the use of optical signals is also contemplated. For example, the use of optical transmitting and receiving devices could just as readily be implemented with the present system. 
     In  FIG. 1  a satellite  34  is shown orbiting the Earth  16 . In an alternative implementation, it is contemplated that the satellite  34  could be used to transpond location information relating to the UAV  12  to the communications station  14 . In this manner, the communications station  14  may use the received location information to track the UAV  12  so that possible intermittent interference does not adversely affect the tracking of the UAV by the communications station  14 . Such intermittent interference may result from topographic conditions, for example from buildings, mountains, etc. Another source of intermittent interference may involve weather anomalies such as localized thunder storms. 
     In general operation, the RF communications system  18  of the UAV  12  generates information, certain portions of which may comprise location information obtained from its own on-board navigation equipment. This information is transmitted via the directional antenna  22  to the directional antenna  30  of the communications station  14 . The directional antenna  22  on the UAV  12  is controlled by the antenna control system  20  preferably via a closed loop arrangement. Alternatively, an open loop control arrangement could be implemented if a memory subsystem  36  is employed to store the location coordinates, such as latitude and longitude, of the communications station  14 . In this manner aiming of the directional antenna  22  could still be accomplished but in an open loop fashion. In either implementation, the directional antenna  22  on the UAV  12  closely tracks the antenna  30  of the communications station  14 , in real time (i.e., essentially instantaneously) while communicating with the communications station  14 . 
     The communications station  14  uses its RF communications system  26  to wirelessly communicate with the UAV  12 . The antenna control system  28  forms a real time system, and in one implementation a real time closed loop system, that controls the pointing of the directional antenna  30  so that the directional antenna  30  continuously tracks the UAV  12  as it travels. Data may be communicated directly from the RF communications system  26  via suitable cabling (e.g., coaxial cabling) connecting the antenna control system  28  and the antenna  30 , or also via the network  32 . 
     Thus, it will be appreciated that the above arrangement forms two independent, real time, antenna pointing control loops: one that is carried out by the components  18 ,  20  and  20   a  of the UAV  12  and the other that is carried out by the communications station  14 . This provides significant redundancy and ensures that if either the UAV  12  antenna control system  20  or the antenna control system  28  of the communications station  14  becomes inoperable for any reason, that the communications station  14  will still be able to track the UAV  12  with its antenna  30 . 
     Referring to  FIG. 2 , a flow chart  100  of major operations performed by the system  10  is shown. At operation  102  the UAV  12  uses its navigation system or information from a GPS satellite, as well as info on the location of the communications station  14 , to control the servo motor system  20   a  to aim its directional antenna  22  at the communications station  14 . At operation  104  the communications station  14  uses its RF communications system  26  to receive the RF transmissions from the UAV  12 . At operation  106 , information in the RF transmissions relating to the real time location of the UAV  12  is provided to the antenna control system  28  which uses this information to aim the directional antenna  30  at the UAV  12 . Thereafter, the antenna control system  20  uses navigation information from its onboard navigation system (not shown), or information provided by a GPS satellite system, and the known location of the communications station  14 , to adjust pointing of the directional antenna  22  as needed to maintain the antenna  22  pointed at the antenna  30  of the communications station. Similarly, the communications station  14  uses real time information received from the UAV  12  as to the UAV&#39;s present location to cause the antenna control system  28  to aim the directional antenna  30  as needed to maintain the antenna  30  pointed at the UAV  14 . 
     The system  10  and methodology described herein thus enables both the UAV  12  and the communications station  14  to implement independent antenna pointing control loops. This enables electrical power from the battery  24  to be used more effectively since the RF energy transmitted by the UAV  12  is focused directly at the communications station  14 , rather than being radiated in an omnidirectional pattern. This can enable the effective communication range between the UAV  12  and the communications station  14  to be extended over what would be possible with a an omnidirectional antenna radiating an RF signal of comparable power. The reduced amount of electrical power needed for transmitting RF signals over a given distance also enables the UAV  12  to stay airborne for longer times before the battery  24  is depleted. The dual but independent antenna pointing control loops of the system  10  further provide added insurance that the RF communications link between the UAV  12  and the communications station  14  will be maintained in the event of temporary topographic or weather disturbances. 
     The system and method of communication described herein could also be used between several unmanned vehicles with the possibility of one acting as a relay between the more distant unmanned vehicle (in a peer-to-peer manner) and the ground station. The unmanned vehicle acting as a relay may either be configured with both an omnidirectional antenna and a directional-tracking antenna, so that the omnidirectional antenna may be used to communicate short range with another unmanned vehicle, while the tracking antenna could be used to communicate with the ground station, or a variation of this configuration. Alternatively, the unmanned vehicle that is acting as a relay could be equipped with several tracking antennas and may be configured to essentially act as an aerial communications relay. 
     It should be also be noted that in the event of a failure of either of the remote communications station  14  or the UAV  12  antenna tracking system components  20 ,  20   a ,  22 , the ability to transfer communications to an omnidirectional antenna system is also possible via the use of an RF amplifier. An RF amplifier could be used in the emergency case of needing to switch to the omnidirectional antenna in order to get close to the same reception/transmission range. In the event of the UAV  12  antenna tracking system components  20 ,  20   a ,  22  failing, reception/transmissions could be transferred to an omnidirectional antenna on the UAV  12  while the remote communications station directional antenna  30  remains in an active tracking mode. The same method could also be applied in the event that the communications  14  station directional antenna  30  becomes inoperable. 
     Predictive tracking can also potentially be used if there is a high latency in the communications link. By “predictive tracking” it is meant that the communications station  14  or the UAV  12  could estimate where the UAV  12  will be, relative to the communications station  14 , by taking into account the velocity vector of the UAV  12  and the position of the communications station  14 . The communications station  14  could continue to track the UAV&#39;s  12  velocity vector until the next communications packet from the UAV  12  is received. 
     It will also be appreciated that various advanced control methods may be used in the antenna tracking systems of both the UAV  12  and the communications station  14 . Such advanced control methods may include neural networks, fuzzy logic, or other adaptive and intelligent control techniques. 
     While various embodiments have been described, those skilled in the art will recognize modifications or variations which might be made without departing from the present disclosure. The examples illustrate the various embodiments and are not intended to limit the present disclosure. Therefore, the description and claims should be interpreted liberally with only such limitation as is necessary in view of the pertinent prior art.