Abstract:
A controller controls the automatic positioning of an antenna. The controller is arranged to position the antenna dependent upon a channel selected by a user, a location of a receiver tuned to the selected channel, and a location of a source of a signal associated with the selected channel.

Description:
TECHNICAL FIELD OF THE INVENTION 
     The present invention relates to the automatic positioning of an antenna in response to channel selection. 
     BACKGROUND OF THE INVENTION AND PRIOR ART 
     Antennas are provided as accessories of RF receivers in order to provide the receivers with the capability of receiving RF signals that are transmitted over the air. Typical antennas that are used in connection with RF receivers, such as televisions, are more sensitive to the signal emitted by a transmitter in some orientations than in others. Thus, when installing an antenna in an area serviced by a plurality of transmitters, the antenna is moved to various orientations in an effort to find the one orientation that provides acceptable reception from all appropriate transmitters. 
     Unfortunately, while one orientation is best for one transmitter, that orientation is seldom best for other transmitters. This problem escalates as the number of possible transmitters increases. Accordingly, it is known to provide antennas with motors that may be remotely controlled by a user. Thus, when the user selects an RF channel for reception, the user remotely controls the motor in order to rotate the antenna until reception by the RF receiver is optimized. This manual approach to the aiming of an antenna is time consuming because the acquisition of optimized reception usually requires a trial and error manual rotation of the antenna each time that a new channel is selected. 
     The present invention is directed to the automatic rotation of an antenna. 
     SUMMARY OF THE INVENTION 
     In accordance with a first aspect of the invention, a system for automatically positioning an antenna comprises a motor and a controller. The motor is arranged to be coupled to the antenna. The controller is coupled to the motor, and the controller is arranged to control the motor in response to selection of a channel so as to automatically drive the antenna to a position at which the antenna is aimed at a source of a signal associated with the selected channel. The controller drives the motor to the position based upon a location of the signal source and a location of the antenna. 
     In accordance with another aspect of the invention, a controller controls the automatic positioning of an antenna. The controller is arranged to drive the antenna to a position dependent upon (i) a channel selected by a user, (ii) a location of the antenna, and (iii) a location of a source of a signal associated with the selected channel. 
     In accordance with still another aspect of the invention, a method of positioning an antenna comprises a) automatically computing a path through which an antenna is to be moved from a first position to a second position, wherein the automatic computation is based upon a location of a remote source corresponding to a channel to which a tuner is tuned by a user and upon a location of the tuner, wherein the first position of the antenna is a current position of the antenna, and wherein the second position of the antenna is a position at which the antenna is aimed at the remote source, and b) moving the antenna through the automatically computed path. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other features and advantages of the invention will be apparent upon reading the following description in conjunction with the single figure of the drawing which illustrates an exemplary automatic antenna rotation arrangement according to an embodiment of the present invention. 
    
    
     DESCRIPTION OF THE INVENTION 
     As shown in the drawing, an RF receiver  10 , such as a television, is provided with an antenna array  12 . The antenna array  12  includes a low VHF antenna  14 , a high VHF antenna  16 , and a UHF antenna  18 . The low VHF antenna  14 , the high VHF antenna  16 , and the UHF antenna  18  are mechanically mounted on a common mast  20  driven by a motor  22 . Accordingly, when the motor  22  is energized, it drives the common mast  20  in order to rotate the low VHF antenna  14 , the high VHF antenna  16 , and the UHF antenna  18  in unison. 
     Each of the low VHF antenna  14 , the high VHF antenna  16 , and the UHF antenna  18  is electrically coupled to a switch  24 . Depending upon the channel selected by the user, the switch  24  selectively couples one of the low VHF antenna  14 , the high VHF antenna  16 , and the UHF antenna  18  to a low noise, variable gain amplifier  26  whose output is electrically coupled to a variable frequency FM trap  28  of the RF receiver  10 . The variable frequency FM trap  28  notches out signals from any unwanted FM station in the receiving path of the antenna corresponding to a selected channel. The variable frequency FM trap  28  provides the signal from the selected one of the low VHF antenna  14 , the high VHF antenna  16 , and the UHF antenna  18  to a tuner  30  of the RF receiver  10 . The tuner  30  tunes to the channel selected by the user of the RF receiver  10  under control of a microprocessor  32 . 
     The microprocessor  32  stores the known locations of all wanted transmitters providing RF signals that can be received by the RF receiver  10 . For example, the microprocessor  32  may store these locations in memory by latitude and longitude. A global position sensor  34  is provided with the RF receiver  10 . Accordingly, when the user selects a channel corresponding to one of the known transmitters whose location is stored in memory by the microprocessor  32 , the microprocessor  32  operates the switch  24  to select the one of the low VHF antenna  14 , the high VHF antenna  16 , and the UHF antenna  18  which is appropriate to the selected channel. The microprocessor  32  also calculates an angle of rotation based upon the stored global location of the transmitter corresponding to the selected channel and upon the global position of the RF receiver  10  as provided by the global position sensor  34 . The microprocessor  32  then drives the motor  22  to rotate the low VHF antenna  14 , the high VHF antenna  16 , and the UHF antenna  18  of the antenna array  12  through that angle of rotation so that the antenna corresponding to the selected channel is aimed at the transmitter transmitting the signal for that selected channel. 
     The microprocessor  32  can also store the locations of all known FM stations as well as other offending sources. Accordingly, when the microprocessor  32  causes the low VHF antenna  14 , the high VHF antenna  16 , and the UHF antenna  18  to be aimed at a transmitter corresponding to a selected channel, the microprocessor  32  also controls the variable frequency FM trap  28  to notch out the signal from any unwanted FM station that is effectively in the receiving path of the positioned antenna. 
     Similarly, the microprocessor  32  can also store the locations of airports and geographical topography. Accordingly, when the microprocessor  32  causes the low VHF antenna  14 , the high VHF antenna  16 , and the UHF antenna  18  to be aimed at a transmitter corresponding to a selected channel, the microprocessor  32  also increases AGC speed through an AGC speed control  36  in order to minimize airplane flutter when an airplane flight path is in the receiving path of the positioned antennas. Also, the microprocessor  32  can control a ghost canceller  38  and/or an adaptive equalizer  40  in order to cancel ghosts caused by multipath transmissions (reflections) when ghost producing geographical topography is effectively in the receiving path of the positioned antenna. 
     Moreover, when the microprocessor  32  causes the low VHF antenna  14 , the high VHF antenna  16 , and the UHF antenna  18  to be aimed at a transmitter corresponding to a selected channel, the microprocessor  32  calculates the received signal strength associated with the selected channel and adjusts the gain of the low noise, variable gain amplifier  26  appropriately. For example, the microprocessor  32  can store in its memory the known transmission powers of the transmitters whose locations are also stored in its memory. The microprocessor  32  can also calculate the distance between the RF receiver  10  and the transmitter corresponding to the selected channel based upon the stored location of this transmitter and the location of the receiver  10  as supplied by the global position sensor  34 . The microprocessor  32  can then determine the received power based upon the stored transmitted power for that transmitter and the calculated distance. Thus, if the received power is too strong because the RF receiver  10  is close to the transmitter corresponding to the selected channel, the microprocessor  32  can reduce the gain of the low noise, variable gain amplifier  26 . Conversely, if the received power is too weak because the RF receiver  10  is far from the transmitter corresponding to the selected channel, the microprocessor  32  can increase the gain of the low noise, variable gain amplifier  26 . 
     Alternatively, optimum gain may be determined at installation by automatically adjusting the gain of the low noise, variable gain amplifier  26  as the antenna array  12  is aimed at each transmitter, and by storing the optimum gain for each transmitter in the memory of the microprocessor  32 . Thus, when the low VHF antenna  14 , the high VHF antenna  16 , and the UHF antenna  18  are aimed at a transmitter, the microprocessor  32  retrieves the corresponding gain from memory and adjusts the gain of the low noise, variable gain amplifier  26  accordingly. 
     Certain modifications and alternatives of the present invention have been discussed above. Other modifications and alternatives will occur to those practicing in the art of the present invention. For example, the RF receiver  10  is provided with the antenna array  12  which includes the low VHF antenna  14 , the high VHF antenna  16 , and the UHF antenna  18 . Instead, the antenna array  12  may include any combination of one or more of these antennas. Alternatively, the functions of the low VHF antenna  14 , the high VHF antenna  16 , and/or the UHF antenna  18  may be combined in fewer antennas, such as a single antenna. 
     Also, as described above, the RF receiver  10  includes the global position sensor  34  to supply the global position of the RF receiver  10  to enable the microprocessor  32  to calculate an angle of rotation for the motor  22 . Instead, the global position sensor  34  may be eliminated from the RF receiver  10  by storing the global position of the RF receiver  10  in the memory of the microprocessor  32  such as at the time that the RF receiver  10  is installed. 
     Moreover, as described above, the position of an antenna is controlled based upon the global positions of the transmitter corresponding to a selected channel and of the RF receiver. Other arrangements may be provided, however, to aim an antenna at a transmitter corresponding to a selected channel. For example, the microprocessor  32  may store compass directions of the various transmitters servicing the RRF receiver  10 . The microprocessor  32  may be arranged then to rotate the antenna to the stored compass direction corresponding to a selected channel, using a compass  42  as feedback during rotation of the antenna to the desired compass direction. Alternatively, the microprocessor  32  may be arranged to calculate the proper angle of rotation based upon the stored compass direction corresponding to the selected channel and upon the current reading of the compass  42 , which is mounted so as to rotate with the antenna array  12 . In any event, the stored compass directions may be input to the microprocessor  32  for storage at the time of installation by rotating each of the low VHF antenna  14 , the high VHF antenna  16 , and the UHF antenna  18  for each of the possible channels and noting the direction of the antenna at which reception is best for the corresponding channel. 
     As another example, the angles of rotation from a reference point can be computed at the time of installation for each transmitter by rotating each of the low VHF antenna  14 , the high VHF antenna  16 , and the UHF antenna  18  from the reference point to a position producing the best reception for the corresponding channel. Each angle of rotation so computed may then be stored in the memory of the microprocessor  32 . Other similar arrangements are possible. This reference point can be periodically calibrated by reference to the compass  42  mounted so as to rotate with the antenna array  12 . Alternatively, the reference point can be periodically calibrated by seeking the angle of rotation at which reception is best for a known transmitter. For this purpose, the known transmitter may correspond to the reference point. Gain can also be periodically calibrated by varying the gain of the low noise, variable gain amplifier  26  at each of the antenna positions and by re-storing in memory the gain corresponding to maximum signal strength for each of these positions. 
     In addition, the present invention has been described above in connection with aiming antennas at transmitters. Such transmitters may be ground-based transmitters or other sources of television and/or radio transmissions. 
     Moreover, as described above, the locations of the transmitters to which the antenna array  12  may be aimed are stored in the memory of the microprocessor  32 . Instead, these transmitter locations could be transmitted by the transmitters to which the antenna array  12  is to be aimed. 
     Also, the compass  42  may be used for calibration. Accordingly, at the time of installation, the motor  22  is controlled so as to point the antenna array  12  in a specified direction, such as north, based upon a reading of the compass  42 . The microprocessor  32  then uses this position as a reference position for subsequent calculations of rotation. 
     Furthermore, as described above, the low VHF antenna  14 , the high VHF antenna  16 , and the UHF antenna  18  are mechanically mounted on a common mast  20  so that, when the motor  22  is energized, the low VHF antenna  14 , the high VHF antenna  16 , and the UHF antenna  18  rotate in unison. Instead, the low VHF antenna  14 , the high VHF antenna  16 , and the UHF antenna  18  may be selectively coupled to the motor  22  in response to channel selection. Thus, when a channel is selected, only the antenna corresponding to the selected channel is coupled to the motor  22  which then rotates only that antenna. Alternatively, each of the low VHF antenna  14 , the high VHF antenna  16 , and the UHF antenna  18  may be provided with its own motor so that, when a channel is selected, only the motor coupled to the antenna corresponding to the selected channel is energized. 
     Accordingly, the description of the present invention is to be construed as illustrative only and is for the purpose of teaching those skilled in the art the best mode of carrying out the invention. The details may be varied substantially without departing from the spirit of the invention, and the exclusive use of all modifications which are within the scope of the appended claims is reserved.