Abstract:
An antenna positioning system includes an outdoor unit with a rotating antenna driven by a motor, and an indoor unit connected to the outdoor unit via a communications link, such as a cable or a wireless link, that enables the indoor unit to control the outdoor unit. On startup, the processor of the indoor unit directs the antenna to search for available signals. The resulting signal information is stored and displayed on a user interface on the indoor unit. The user can then select a desired signal and the processor of the indoor unit will automatically rotate the antenna to the appropriate angular position. Both the search procedure and repositioning of the antenna rely on accurate calibration of the antenna&#39;s angular velocity to determine the antenna&#39;s angular position, rather than relying on a position sensor.

Description:
RELATED APPLICATION 
       [0001]    The present application is based on and claims priority to the Applicant&#39;s U.S. Provisional Patent Application 62/087,146, entitled “Antenna Positioning System,” filed on Dec. 3, 2014. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates generally to the field of antennas. More specifically, the present invention discloses an antenna positioning system that relies on accurate calibration of the rotational velocity of the antenna to determine its angular position. 
         [0004]    2. Statement of the Problem 
         [0005]    A wide variety of antennas have been invented in the past that rotate about at least one axis. Many antennas have patterns that are directional, and therefore benefit from positioning systems that can automatically point the antenna toward a desired transmitter/receiver, such as a satellite or a terrestrial signal source. Some antenna systems provide azimuth rotation (i.e., rotation about a vertical axis). Satellite antenna systems usually provide both azimuth and elevational rotation of the antenna. The following disclosure of the present invention is directly primarily to azimuth rotation of the antenna, as the simplest case. However, it should be understood that the present invention could be readily applied to antenna rotation about multiple axes. 
         [0006]    Antenna positioning systems typically include a controller and a drive motor that rotates the antenna (e.g., directly via a mounting spindle, or indirectly via a ring gear or other gear or belt-drive mechanism). Obviously, the controller must know the precise angular position of the antenna to accurately control its angular position and obtain optimal antenna performance. This is commonly done by a position sensor that detects the angular position of the antenna and provides feedback to the controller. Several types of position sensors have been used in the past, but the costs and complexity associated with conventional position sensors have been ongoing concerns. Therefore, a need exists for an antenna positioning system that does not require a position sensor. 
         [0007]    Solution to the Problem. The present invention eliminates the need for a position sensor by relying on accurate calibration of the angular velocity of the antenna to determine the angular position of the antenna. During initial startup, the present system measures the time required for the antenna to rotate between two known angular positions defined by a stop, which allows calculation of the antenna&#39;s angular velocity. During subsequent operation of the antenna system, the controller can accurately move the antenna from a known present angular position to a desired new angular position by determining the required travel time based on the angle between the two angular positions and the antenna&#39;s angular velocity. 
         [0008]    The present antenna system can also include a search mode in which the antenna searches for available signals over a predetermined range of rotation, or incrementally searches within sectors. In either case, the direction of any detected signals can be determined by the controller based on travel time and the antenna&#39;s angular velocity. The signal information (e.g., signal direction and strength) gathered during the search is stored and used during subsequent operation of the antenna system. 
         [0009]    Calculations of the antenna&#39;s angular position can be further refined by including temperature calibration, and to account to the acceleration and deceleration characteristics of the drive system, and the rotational inertia of the antenna and related components. 
       SUMMARY OF THE INVENTION 
       [0010]    This invention provides an antenna positioning system that relies on accurate calibration of the angular velocity of the antenna to determine the angular position of the antenna, and thereby eliminates the need for a position sensor. The present system includes an outdoor unit with a rotating antenna driven by a motor, and an indoor unit connected to the outdoor unit via a communications link, such as a cable or a wireless link, that enables the indoor unit to control the outdoor unit. On startup, the processor of the indoor unit directs the antenna to search for available signals. The resulting signal information is stored and displayed on a user interface on the indoor unit. The user can then select a desired signal and the processor of the indoor unit will automatically rotate the antenna to the appropriate angular position. Both the search procedure and repositioning of the antenna rely on accurate calibration of the antenna&#39;s angular velocity to determine the antenna&#39;s angular position. 
         [0011]    These and other advantages, features, and objects of the present invention will be more readily understood in view of the following detailed description and the drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    The present invention can be more readily understood in conjunction with the accompanying drawings, in which: 
           [0013]      FIG. 1  is a schematic block diagram of an embodiment of the present invention. 
           [0014]      FIG. 2  is a block diagram of the outdoor unit (ODU)  30  of the present invention. 
           [0015]      FIG. 3  is a block diagram of the indoor unit (IDU)  20  of the present invention. 
           [0016]      FIG. 4  is a diagram of the front panel of the IDU  20 . 
           [0017]      FIG. 5  is a flowchart of the search process used in the initial scan for available television signals. 
           [0018]      FIG. 6  is a flowchart of the calibration process for determining the angular velocity of the antenna. 
           [0019]      FIG. 7  is a flowchart of the calibration process for determining the motor resistance, which is subsequently used to determine whether the drive motor has stalled. 
           [0020]      FIG. 8  is a flowchart of the process used to rotate the antenna to a new desired location. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0021]    Turning to  FIG. 1 , a schematic block diagram is provided showing an embodiment of the present invention. The major components of the present system include a rotatable antenna  10 , an outdoor unit (ODU)  30 , and an indoor unit (IDU)  20 . A motor  12  is used to rotate the antenna  10  about an axis. For example, the motor  12  can directly drive the antenna  10 , or the antenna  10  can be driven via a drive gear, belt or transmission mechanism. Any of a wide variety of antennas can be employed. In the embodiment shown in  FIG. 1 , the drive gear  14  includes a mechanical stop  16 , or hard stop, that serves as a fixed point of reference regarding rotation of the antenna  10 , as will be described in greater detail below. This stop  16  limits further rotation of the antenna beyond a predetermined point. Other types of stops could be readily substituted. This embodiment is limited to antenna rotation about a vertical axis, which is typically sufficient for over-the-air TV reception. It should be understood that the present invention could be extended to accommodate antenna rotation about multiple axes, as is more typically required for satellite antennas. 
         [0022]      FIG. 2  is a block diagram of the outdoor unit (ODU)  30 . The ODU  30  in this embodiment includes a conventional balun and diplexer  31 , and amplifier  32  for processing the UHF and VHF signals from the antenna  10  that are output to the IDU  20  via a front connector  33  and cable  38 . The ODU  30  also includes a motor controller  35  and motor drive circuitry  37  that control operation of the motor  12  to rotate the antenna  10 . In the preferred embodiment of the present invention, the IDU  20  provides substantially all of the system intelligence, so these antenna drive functions are under the ultimate control of the IDU  20 , as will be described below. The motor controller  35  detects DC control signals sent by the IDU  20  over the cable  38 , and operates the motor  12  accordingly. For example, a DC signal of less than 6.5 volts can indicate a stop condition. A DC signal between 6.5V and 7.5V indicates clockwise antenna rotation, and a DC signal greater than 7.5V indicates counterclockwise antenna rotation. The motor drive circuitry  37  also monitors the input voltage (V IN ) and motor current (I M ) to enable the motor controller  35  to quickly shut down the motor  12  if either value exceed predetermined limits. 
         [0023]    Using a single cable  28  to both transmit the antenna signal from the ODU  30  to the IDU  20 , and transmit DC control signals from the IDU  20  to the ODU  30  simplifies wiring between these units  20 ,  30 . However, it should be understood that other control protocols could be substituted. In addition, other types of wired or wireless communications links could be used between the IDU  20  and ODU  30 . 
         [0024]      FIG. 3  is a block diagram of the indoor unit (IDU)  20 . This includes a processor  25  that effectively controls operation of the entire antenna system. In particular, the processor  25  controls operation of the ODU  30  and antenna  10 , controls the user interface  23  and LED displays  24  of the IDU  20 , and also stores data regarding the current antenna location and signal locations found during the search procedure. The IDU  20  also includes a user interface  23  with manual controls for operation of the system (e.g., moving the antenna and searching for available TV signals), and LED displays  24  indicating the system status for the user. In addition, the IDU  20  is equipped with a coaxial connector  21  for attaching the cable  38  to the ODU  30 , and another coaxial connector  22  for attaching a coaxial cable to a TV. A tuner  26  is included to allow the processor to measure signal strength from the ODU  30  during the search procedure. Optionally, the tuner could also be used to identify TV channels. If so, a channel display  29  can be employed to display this TV channel information for the user. 
         [0025]    A current sensor  28  enables the processor  25  to monitor the current drawn by the ODU  30  and motor  12  via the cable  38 . A current drop indicates that the motor  12  has stopped, which is typically as a result to hitting the hard stop  16  shown in  FIG. 1 . This enables the processor  25  in the IDU  20  to know when the antenna  10  has moved to the known stop position. In addition, the processor  25  can then respond by directing the motor  12  to stop. 
         [0026]    Finally, the IDU  20  includes DC power switching circuitry  27  controlled by the processor  25  that regulates the voltage (V OUT ) of the DC power supplied to the ODU  30  via the cable  38 . As discussed above, this DC voltage serves as a control signal to the motor controller  35  in the ODU  30  to either stop the motor  12 , rotate the antenna clockwise, or rotate the antenna counterclockwise. 
         [0027]      FIG. 4  is a diagram of the front panel of the IDU  20  illustrating one embodiment for the user interface  23 . A circular pattern of positional LEDs  46  are used both to indicate the angular position of the antenna  10  and the optimal pointing locations found during the search procedure. In particular, green LEDs indicate the antenna&#39;s angular position. If two green LEDs are lit, the antenna  10  is positioned between those positions. Red LEDs indicate the optimal pointing locations found during the search. If both the red and green LEDs are lit on the same spot, this indicates the current antenna angular position as well as an optimal pointing direction. 
         [0028]    The search button  42  initiates a new search after powering the antenna on. The processor  25  will automatically instruct the ODU  30  to move the antenna  10  to the best result. Pressing the search button  42  after a search has been completed causes the processor  25  to move the antenna  10  between the optimal antenna angular locations found in the last search. Pressing and holding the search button  42  clears memory and starts a new search. 
         [0029]    The readout display  48  shows the number of TV frequencies found at the current antenna position. This is the number of radio-frequency (RF) signals available and will usually differ from the number of virtual channels scanned on a TV because of multi-casting. Typically, a TV scan will result in two or three times more channels than RF signals. 
         [0030]    The “rotate antenna” buttons  44 ,  45  (clockwise and counter-clockwise) can be used to manually fine tune a channel that may be pixelating or weak. The “rotate antenna” buttons  44 ,  45  can also be used to manually point the antenna  10  toward a known antenna angular location. An on/off button  40  is used to turn the antenna system on and off. 
         [0031]      FIG. 5  is a flowchart of the signal search process used in the initial scan for available television signals  18 ,  19 . The search process is initiated when the user presses the search button  42  on the IDU  20  (step  50 ). If the speed of the antenna  12  has not been recently calibrated, the antenna speed calibration process shown in  FIG. 6  is executed. Otherwise, the antenna speed stored from the last calibration is used. It should be noted that the antenna speed calibration process in  FIG. 6  leaves the antenna in the known stop position, and the start-up procedure for the system also moves the antenna to the stop position, so the antenna can be assumed to be in the stop position when initially entering step  53  in  FIG. 5 . 
         [0032]    In step  53 , the processor  25  and tuner  26  scan for television signals within a predetermined arc segment of the antenna&#39;s range of rotation. For example, given a LED display  46  in  FIG. 4  with eight LEDs, each segment in step  53  of  FIG. 5  would be 360°/8, or 45°. This scan can be done in any of several possible ways. For example, the antenna  10  can be rotated through the segment at a constant angular velocity, while the tuner  26  and processor detect TV signals on the fly. The angular position of each TV signal can be calculated based on the elapsed run time for the antenna, given the calibrated antenna speed and the initial angular position of the antenna. Alternatively, the present system can actively seek TV signals within the segment, as outlined for example in U.S. Pat. No. 8,466,965 (Murphy et al.). In this case, the change in location of the antenna at any time can be calculated by multiplying the calibrated antenna speed by the elapsed run time for the antenna. The system then moves to the next segment in step  54  and repeats the search process (step  53 ) until the final location of the antenna is reached (step  55 ). The processor then evaluates and stores these search results in data storage (step  56 ) for subsequent use during normal operation of the antenna system. 
         [0033]      FIG. 6  is a flowchart of the calibration process for determining the angular speed of the antenna  10  in step  52  of  FIG. 5 . In step  60 , the antenna  10  is rotated counterclockwise until it hits the stop  16 , so that the antenna is in a known starting position for calibration. Next, the processor starts a timer (step  61 ) and rotates the antenna in the clockwise direction until it hits the stop  16  (step  62 ). The processor then stops the timer and calculates the elapsed time for the clockwise direction (step  63 ). Similarly, the processor starts the timer (step  64 ), rotates the antenna in the counterclockwise direction until it hits the stop  16  (step  65 ), and then stops the time and calculates the elapsed time for the counterclockwise direction (step  66 ). The elapsed times in the clockwise and counterclockwise directions can be readily converted in angular speeds for the antenna in these directions. 
         [0034]      FIG. 7  is a flowchart of the calibration process for determining the resistance of the motor  12  and cable  38 . The motor controller  35  of the ODU  30  controls motor movement by monitoring the voltage supplied to the ODU  30  from the IDU  20 . Therefore it is important to be able to measure this voltage accurately. Also, there is a DC voltage drop between the IDU and ODU that varies with current. This drop can be compensated for by adjusting the voltage thresholds that are set by the DC power switching circuitry  27  in the IDU  20  to determine motor movement if the cable resistance is known. In step  70  of  FIG. 7 , the input voltage V IN  supplied to the ODU  30  is initially measured by the ODU. The motor  12  is then run for a period of time in step  71 . In step  72 , the resulting input voltage V IN (M) and current Inn are measured while the motor  12  runs. In step  73 , the cable resistance is calculated by R SYS =(V IN −V IN (M))/I M . This enables the DC voltage windows used to control operation of the motor  12  to be varied depending on the current being drawn by the motor  12 . Finally in step  74 , the ODU processor  35  tests whether the measured values for R SYS , V IN , and I M  are within predetermined limits. 
         [0035]      FIG. 8  is a flowchart of the process used to rotate the antenna  10  to a new desired location from a known previous angular position. In response to user input selecting a desired external signal source, the processor  25  retrieves the stored angular direction associated with the desired signal source from data storage. In step  81 , the processor  25  calculates the difference in angular position (Δθ) between the two locations, and also determines whether the antenna  10  should rotate in a clockwise or counterclockwise direction to reach the new angular position. It should be noted that the antenna  10  cannot rotate through the stop  16 , and therefore the stop  16  must be avoided in selecting the direction of travel for the antenna  10 . 
         [0036]    In step  81 , the processor calculates the required travel time duration for the antenna  10  to move to the new angular position based on the direction of travel, and the angular difference (Δθ) between the previous angular position and desired angular position divided by the angular velocity of the antenna. The DC power switching circuitry  27  in the IDU  20  is set for the appropriate direction of travel (i.e., clockwise or counterclockwise) in step  82 . In step  83 , the motor  12  is directed to run for the calculated time duration and direction of travel to move the antenna  10  to the new angular position. 
         [0037]    The preceding disclosure has assumed a simple linear relationship in the change in angular position is determined by angular speed multiplied by time. This general concept can be extended to accommodate other factors. For example, the antenna speed can be temperature dependent. To some extent, this will be automatically picked up by the antenna speed calibration process at startup. However, the present system can also be equipped with a temperature sensor, and the processor can include a temperature compensation function in calculating the required travel time duration for moving the antenna. The processor can also programmed to include ramping functions that account for the acceleration and deceleration characteristics of the motor  12  and antenna  10 . 
         [0038]    The above disclosure sets forth a number of embodiments of the present invention described in detail with respect to the accompanying drawings. Those skilled in this art will appreciate that various changes, modifications, other structural arrangements, and other embodiments could be practiced under the teachings of the present invention without departing from the scope of this invention as set forth in the following claims.