Abstract:
An antenna system and a corresponding method for satellite lock-on applied to vehicles automatically lock on at least one satellite in the space by means of a lock-on signal. The technique features on a scan driving signal that initiates a space scan of the antenna system so as to obtain a scan data. According to peak values of the scan data, coordinates of a plurality of satellites in the space are realized and individually recorded. Then, after receiving a lock-on signal, the satellite coordinate of the satellite to be locked is retrieved so as to drive the antenna to point at the satellite to be locked.

Description:
[0001]    This application claims the benefit of Taiwan Patent Application Serial No. 097124574, filed Jun. 30, 2008, the subject matter of which is incorporated herein by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    (1) Field of the Invention 
         [0003]    The invention relates to a technology for locking on a specific satellite, and more particularly to the technology that utilizes scanned data to lock on the target satellites. 
         [0004]    (2) Description of the Prior Art 
         [0005]    Satellite technology has been promoting human life in various manifolds. In daily life, products in global positioning system (GPS), such as positioning apparatuses, mobile phones, broadcasting apparatuses, navigation devices, and so on, had drawn people closer geographically and had visualized the image of global village. In particular, the achievement in broadcasting via satellites has realized the “real-time” TV programs in broadcasting industry, and has made it possible to play varieties of programs at any corner around the world. 
         [0006]    In the prior art, the satellite broadcasting technology can be roughly classified into a type of stationary broadcasting or a type of mobile broadcasting. The type of stationary broadcasting is to have a satellite antenna system construct on the ground or a suitable fixed construction. Such type of broadcasting is to download satellite parameters firstly, then to actuate the antenna system so as to aim at the target satellite, and to establish a bi-directional signal and data link between the station and the satellite. Yet, the type of stationary broadcasting can only provide a limited space coverage, due to its less mobility instinct, and it is quite possibly that the signal broadcasted as DVB-T (Digital Video Broadcasting- Terrestrial) can not be reached wherever outside the field pattern according to the power transmitted. 
         [0007]    For the aforesaid disadvantage in limited space coverage is obvious to the stationary broadcasting, the mobile broadcasting, on the other hand, provides an alternative solution thereto. One of the main applications in the mobile broadcasting is the satellite news gathering (SNG) vehicle. The SNG vehicle provides an on-top antenna system for tracking satellites and for processing bi-directional signal and data communication as soon as the target satellite is locked on. 
         [0008]    In the case that the tracking target of the antenna system for mobile broadcasting is shifted from one to another satellite, the satellite parameters of the new satellite are needed to be pre-inputted to the database of the antenna system so as to establish an effective communication between the sky and the ground. In practice, the database of the antenna system can pre-store parameters of all prospective satellites in the space, and actually a change in the satellite tracking is as simple as a task of control choice in operating the antenna system. According to the satellite parameters (especially the coordinate parameters), the antenna dish of the antenna system can be precisely pivoted to direct the target satellite. Alternatively, the antenna system can also obtain the satellite parameters from an earth satellite transmission station or a satellite control center, while a new tracking starts. 
         [0009]    In practice, for the antenna system to successfully lock on an orbiting satellite, it mainly depends on the following three coordinate factors: celestial coordinates of the satellite including a right ascension (R.A.) angle (RA angle, hereinafter) and a declination (Decl.) angle (Decl angle, hereinafter), geographic coordinates of the antenna system (i.e. the SNG vehicle) including a longitude and a latitude, and the pointing angles of attitude related to the vehicle including an azimuth angle and an elevation angle. 
         [0010]    In the prior art, the final orientation pointing to the specified satellite is primarily decided by combining those satellite coordinates and those corrected parameters related to an azimuth angle and an elevation angle which had been initially integrated into a satellite antenna system. 
         [0011]    However, for the vehicle of the antenna system is kept moving arbitrarily and subjected to possible mechanical vibrations, certain deviations might be expected during the process of satellite tracking carried out by the antenna configured onboard at the vehicle by adopting those corrected parameters which had been accepted as reference values initially. 
         [0012]    Consequently, after a substantial period of operation by using the satellite data input and coordinate captured, the mobile satellite dish becomes hard to precisely lock on the target satellite. 
         [0013]    Therefore, an improved satellite lock-on technique for a mobile antenna system to precisely and promptly lock on an orbiting satellite definitely provides a technical solution to the ordinary person skilled in the art. 
       SUMMARY OF THE INVENTION 
       [0014]    Accordingly, it is an object of the present invention to provide an antenna system for satellite lock-on and a corresponding method for operating the antenna system, in which instant scan data of the antenna system mounted on a mobile vehicle can be used to refresh position states of the antenna system and the vehicle so as to precisely perform the tracking and locking-on of an orbiting satellite from various satellites in the space. 
         [0015]    In the present invention, the antenna system and the accompanying method can automatically lock on at least a satellite according to the respective lock-on signals. A scan-driving signal of the present invention is to drive the antenna device of the antenna system to perform a space scanning so as to obtain a scan data. By comparing peak values of the scan data to the respective pre-stored satellite parameters, the satellite coordinates of individual satellites in the space within the scanning range of the antenna device can be more precisely defined. At the same time, satellite coordinates for all those prospective satellites are recorded. After a target satellite is determined, the respective satellite coordinates of the target satellite are retrieved and thereby the antenna device can then be correctly directed to the target satellite. 
         [0016]    In the present invention, to have the antenna device more accurately direct to and lock on the target satellite, both the satellite coordinates and the vehicle coordinates of the antenna system are applied. 
         [0017]    By providing the system and the method for locking on the target satellite in means of pre-scanning according to the present invention, real-time states of the vehicle, the antenna device and the target satellite can be obtained. Thereby, adjustment upon the antenna device for precisely pointing the target satellite can be carried out immediately. Therefore, by the present invention, all possible mechanical deviations in the antenna tracking system can be properly compensated. Thus, quality in transmitting and/or receiving satellite signals of the antenna system can be substantially upgraded. 
         [0018]    All these objects are achieved by the antenna system for satellite lock-on and the method for operating the antenna system described below. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]    The present invention will be specified with reference to its preferred embodiments illustrated in the drawings, in which: 
           [0020]      FIG. 1  is a schematic view of a vehicle equipped with an antenna system in accordance with the first embodiment of the present invention; 
           [0021]      FIG. 2  is a functional block diagram of the first embodiment of the present invention; 
           [0022]      FIG. 3  illustrates a schematic view of a horizontal scanning adopted by DVB-S antenna to obtain scanned data in the first embodiment of the present invention; 
           [0023]      FIG. 4  illustrates how those scanned data are analyzed and the relative peak values and corresponding coordinates are determined by scanned from the first embodiment of the present invention; 
           [0024]      FIG. 5  illustrates the dynamic positioning signal transmitted by GPS to generate the coordinate of the vehicle in the first embodiment of the present invention; 
           [0025]      FIG. 6  demonstrates the azimuth angle defined by the vehicle in the first embodiment of the present invention; 
           [0026]      FIG. 7  demonstrates the elevation angle defined by the vehicle in the first embodiment of the present invention; 
           [0027]      FIG. 8  illustrates a table to record the satellites&#39; positions from performing the method for operating the antenna system in accordance with the present invention; 
           [0028]      FIG. 9  is a functional block diagram of the second embodiment of the present invention; and 
           [0029]      FIG. 10  and  FIG. 11  are integrated to illustrate a flowchart both applied to the first and the second embodiments in accordance with the present invention. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0030]    The invention disclosed herein is directed to an antenna system for satellite lock-on and a corresponding method for operating the antenna system. In the following description, numerous details are set forth in order to provide a thorough understanding of the present invention. It will be appreciated by one skilled in the art that variations of these specific details are possible while still achieving the results of the present invention. Under such a circumstance, there are two preferred embodiments described herein and a flowchart applied for both embodiments is provided to illustrate the present invention in details. 
         [0031]    Referring now to  FIG. 1  and  FIG. 2 , in the first embodiment of the present invention, an antenna system  100  constructed on a carrier vehicle  200  includes at least a signal control box  1 , an antenna unit  2  (for transmitting/receiving), a driving unit  3  and a positioning unit  4 . The carrier vehicle  200  of the present invention can be a craft applied in waters, at land, or in the air. Also shown in  FIG. 2 , three prospective satellites  300 ,  300   a , and  300   b  are feasible by the antenna system  100  in the space. 
         [0032]    In the following description, terminologies DVB-T, DVB-S and DVB-S/T are adopted. However, it is well known that, in some area of the planet, different terminologies might be used though the contents and elements involved are the same; for example, the DMB-T/H specs in China, and the ATSC (Advanced television systems committee) specs in USA 
         [0033]    The signal control box  1  coupled with the antenna unit  2  through the driving unit  3  further includes a processing unit  11 , an operational interface  12 , a driving-control circuit  13 , a control signal amplifier  14 , a control signal driving circuit  15 , a memory unit  16 , an encoder  17 , a digital video broadcasting-satellite/terrestrial (DVB-S/T) receiver  18 , and a digital video broadcasting-terrestrial (DVB-T) transmitter  19 . 
         [0034]    The processing unit  11  further includes a microprocessor  111  and a data processor  112 . The operational interface  12  coupled with the processing unit  11  can be configured as an operation panel. The driving-control circuit  13  is coupled with the processing unit  11  and the driving unit  3 . The control signal amplifier  14  is also coupled with the processing unit  11 . The control signal driving circuit  15  is coupled with the control signal amplifier  14 , the DVB-S/T receiver  18  and the antenna unit  2 . 
         [0035]    The memory unit  16  coupled with the processing unit  11  further includes an operational program  161 , a satellite coordinate memory area  162  and a vehicle coordinate memory area  163 . The encoder  17  is coupled with the processing unit  11 , DVB-S/T receiver  18  and the antenna unit  2 . The DVB-S/T receiver  18  is coupled with the processing unit  11 , the DVB-T transmitter  19  and the antenna unit  2 . 
         [0036]    In the embodiment shown in  FIG. 2 , the antenna unit  2  includes a digital video broadcasting-satellite (DVB-S) antenna  21  and a digital video broadcasting-terrestrial (DVB-T) antenna  22 , in which the DVB-S antenna  21  can be a dish antenna or a flat antenna. The driving unit  3  can be a step motor for driving the DVB-S antenna  21  and the DVB-T antenna  22 . In practice, the antenna unit  2  can only include the DVB-S antenna  21 , or can be a combination including at least one DVB-S antenna  21  and at least one DVB-T antenna  22 . 
         [0037]    Generally, the adjustment of the attitude related to an antenna includes its azimuth angle and elevation angle. The positioning unit  4  as shown includes a GPS system  41 , a GPS antenna  42  and a vehicle position-sensing unit  43 . The GPS system  41  couples in between with the GPS antenna  42  and the processing unit  11 . The vehicle position-sensing unit  43  couples the processing unit  11  and further includes a gyroscope  431  and a gravity-sensing element  432 . 
         [0038]    In this embodiment shown in  FIG. 2 , the operational interface  12  is utilized to set up a scan pattern (for example, a horizontal scan or a vertical scan) and related scan parameters (such as a range of a scan angle, an angular increment in scanning, a scan frequency and so on). The operational interface  12  can be triggered and generate a scan-driving signal S 1  to processing unit  11 . According to the signal S 1 , the processing unit  11  would activate the driving unit  3  through the driving-control circuit  13  to drive the DVB-S antenna  21  for a space scanning in accordance with the preset scan pattern and scan parameters. Consequently, a set of data via scanning can be obtained. 
         [0039]    Refer further to  FIG. 3  and  FIG. 4 , in which  FIG. 3  illustrates a horizontal scan of the first embodiment of the DVB-S antenna  21  and  FIG. 4  typically tables some peak values of signal strengths with respect to the specific scan coordinates. In the horizontal scanning of  FIG. 3 , the angular increment in the azimuth angle along the horizontal direction I 1  per a scan cycle is defined as a Δθ, while the angular increment in the elevation angle in the scan cycles is defined as ΔΦ. 
         [0040]    During the scanning, some specific scan coordinates would be defined in advance for recording the scan data, for example coordinates P 00 ˜P 33  in  FIG. 3 . While in scanning, the DVB-S antenna  21  would capture satellite signals S 2  upon meeting the preset scan coordinates. A typical example of the signal strengths with respect to corresponding scan coordinates is tabled in  FIG. 4 . In the art, the signal strength can be realized by the induced voltage or the power variation. 
         [0041]    For example in  FIG. 4 , a local maximum or peak signal strength is found in P 11  among the neighboring P 01 , P 10 , P 21  and P 12  (with signal strengths  5 ,  5 ,  6  and  7 , respectively). If a further analysis can confirm that the peak value in P 11  is not a result of local perturbation or signal interface, it is no doubt that the DVB-S antenna  21  at P 11  is pointing at a satellite (possible any of satellite  300 ,  3001  and  300   b ). Then, P 11  can be assigned to be one of the satellite coordinates. 
         [0042]    Similarly in  FIG. 4 , another satellite coordinate of another satellite can be confirmed to be the P 23 . In the present invention, the satellite coordinates with respect to the corresponding scan coordinates P 11  and P 23  can be defined as coordinates (Δθ, ΔΦ) and (2Δθ, 3ΔΦ), respectively, and further these two satellite coordinates can be stored into the satellite coordinate memory area  162  of the memory unit  16 . 
         [0043]    In the preceding description, each horizontal scanning follows a horizontal direction I 1  with the angular increment in the elevation. Alternatively, each scanning can be started along the vertical direction I 2  of  FIG. 3  with the angular increment in the azimuth. Furthermore, while analyzing the satellite coordinates, the result can be obtained by comparing preset reference values with those signal strength caught by the DVB-S antenna  21 . 
         [0044]    Refer further to  FIGS. 5-8 ; in which  FIG. 5  illustrates a relationship of a GPS satellite and a moving vehicle on the planet,  FIG. 6  illustrates the coordinate system defined for the vehicle,  FIG. 7  defines an elevation angle of the vehicle, and  FIG. 8  tables the vehicle coordinates defined by various satellites. 
         [0045]    With the satellite scanning in process, the vehicle  200  can be still in motion. Namely, the vehicle coordinate may be changing during the satellite scanning. To ensure the accuracy in locating the satellite, the real-time vehicle coordinate of the moving vehicle  200  shall be taken into calculation. 
         [0046]    In the scanning, the GPS system  41 , through the GPS antenna  42 , can receive a dynamic position signal S 3  from a GPS satellite  400 . The signal S 3  is then sent to the microprocessor  111  or the data processor  112  for generating a satellite position coordinate (L 0 , A 0 ) to coordinate the vehicle  200 . In general, the coordinate (L 0 , A 0 ) is defined by the longitude and the latitude. In the present invention, the vehicle position-sensing unit  43  determines a vehicle position for the vehicle  200 , and a dynamic position signal S 4  according to the vehicle position is formed and further sent to the microprocessor  111  or the data processor  112 . The vehicle position can include a vehicle azimuth ΔAZ 0  and a vehicle elevation ΔE 0 ; i.e., forming a vehicle position (ΔAZ 0 , ΔE 0 ), in which the ΔAZ 0  can be determined by the gyroscope  431  and the ΔE 0  by the gravity-sensing element  432 . In the present invention, both the satellite position coordinate (L 0 , A 0 ) and the vehicle position (ΔAZ 0 , ΔE 0 ) can be recorded into the vehicle coordinate memory area  163  of the memory  16 . Further, each of the satellite coordinates is assigned an individual satellite number as shown in  FIG. 8 . 
         [0047]    Referring back to  FIG. 2 , in the case that the vehicle  200  moves to a new location for the user to lock on another satellite after finishing the preceding scanning, detecting and recording, the operational interface  12  is used to select the satellite number ( 0001  for example) and to send a lock-on signal S 5  to the microprocessor  111 . Then, the microprocessor  111  and the data processor  112  would retrieve the satellite coordinate (Δθ, ΔΦ) from the satellite coordinate memory area  162 , and retrieve also the satellite position coordinate (L 0 , A 0 ) and the vehicle position (ΔAZ 0 , ΔE 0 ) from the vehicle coordinate memory area  163 . The microprocessor  111  thus applies the GPS system  41  to re-capture a new satellite position coordinate, and also the vehicle position-sensing unit  43  to re-capture a new vehicle position. 
         [0048]    According to the downloaded satellite coordinate (Δθ, ΔΦ), the satellite position coordinate (L 0 , A 0 ), the vehicle position (ΔAZ 0 , ΔE 0 ), the re-captured satellite position coordinate and the re-captured vehicle position, the microprocessor  111  or the data processor  112  utilizes the operational program  161  to compute the pointing direction of the DVB-S antenna  21 , and also further to send an antenna control signal S 6  to the driving-control circuit  13 . The driving-control circuit  13  would then send a driving signal S 7  to the driving unit  3  for properly driving the DVB-S antenna  21  to point at the satellite  0001  (or any of the satellite  300 ,  300   a  and  300   b ). 
         [0049]    Similarly, in the case that the satellite  0002  is the target satellite, the microprocessor  111  and the data processor  112  would retrieve the satellite coordinate (2Δθ, 3ΔΦ) from the satellite coordinate memory area  162 , and retrieve also the satellite position coordinate (L 0 , A 0 ) and the vehicle position (ΔAZ 0 , ΔE 0 ) from the vehicle coordinate memory area  163 . The microprocessor  111  thus applies the GPS system  41  to re-capture a new satellite position coordinate, and also the vehicle position-sensing unit  43  to re-capture a new vehicle position. 
         [0050]    According to the downloaded satellite coordinate (2Δθ, 3ΔΦ), the satellite position coordinate (L 0 , A 0 ), the vehicle position (ΔAZ 0 , ΔE 0 ), the re-captured satellite position coordinate and the re-captured vehicle position, the microprocessor  111  or the data processor  112  utilizes the operational program  161  to compute the pointing direction of the DVB-S antenna  21 , and also further to send an antenna control signal S 6  to the driving-control circuit  13 . The driving-control circuit  13  would then send a driving signal S 7  to the driving unit  3  for properly driving the DVB-S antenna  21  to point at the satellite  0002  (or any of the satellite  300 ,  300   a  and  300   b ). 
         [0051]    In the case that the user is to control the DVB-S/T receiver  18 , the operational interface  12  is applied to make the microprocessor  111  send a control signal S 8  to the control signal amplifier  14 . The control signal amplifier  14  would then amplify the control signal S 8  and further send the amplified signal to the control signal driving circuit  15  for accordingly control the DVB-S/T receiver  18 . 
         [0052]    Prior to receiving the satellite signal S 2 , the microprocessor  111  downloads at least a digital video data from the memory  16 . The digital video signal is transformed into a DVB-T video signal S 9  by the encoder  17 . Then, the DVB-S/T receiver  18  sends the signal S 9  to the DVB-T transmitter  19 , and the DVB-T transmitter  19  further broadcasts the signal S 9  for the digital TVs  500  and  500   a  to receive. Meanwhile, the DVB-T antenna  22  is used to receive the foreign DVB-T video signals and further to restore the DVB-T signals into the memory by the microprocessor  111 . Else, the DVB-T transmitter  19  can transform the foreign DVB-T video signal into the respective DVB-T video signal S 9  for further broadcasting. 
         [0053]    In the art, the DVB-S/T receiver  18  can work with an on-screen display (OSD) interface for performing aforesaid functions of the operational interface  12 . Namely, the user can work on the OSD interface to perform operations and controls of the antenna system  100 . 
         [0054]    As soon as the satellite signal S 2  is received, the microprocessor  111  downloads at least a digital video data from the memory  16 . The digital video signal is transformed into a DVB-S satellite signal S 2  or a  1 o DVB-T video signal S 9  by the encoder  17 . The DVB-S signal S 2  is sent to the locked-on satellite by the DVB-S antenna  21 , while the signal S 9  is sent to the DVB-T transmitter  19  by the DVB-S/T receiver  18 . The DVB-T transmitter  19  then broadcasts the signal S 9  for the digital TVs  500  and  500   a  to receive. 
         [0055]    Meanwhile, the locked-on satellite (any of satellite  300 ,  300   a  and  300   b ) sends the satellite signal S 2  to the signal control box  1  via the DVB-S antenna  21 . The signal S 2  is then decoded and further sent to the microprocessor  111  for being transformed into the respective digital satellite (program) data to be stored in the memory  16 . Also, the signal S 2  is received by the DVB-S/T receiver  18  and further to be transformed into the respective DVB-T video signal S 9 . The DVB-T transmitter  19  is then send out the DVB-T video signal S 9  to be received by the digital TVs  500  and  500   a . To the skill person in the art, the control signal S 8  for controlling the DVB-S/T receiver  18  is fully understood to be able to help control the transformation and transmission between the signal S 2  and the signal S 9 . 
         [0056]    In the preceding description, the first embodiment of the antenna system in accordance with the present invention is believed to be sufficiently understood. In the following description, a second embodiment of the antenna system will be introduced. A major difference between the first embodiment and the second embodiment would be that, in the second embodiment, the construction and functions of the signal control box are moved to another antenna system. 
         [0057]    Referring now to  FIG. 9 , the second embodiment of the antenna system in accordance with the present invention is shown. The antenna system  5  constructed on the carrier vehicle  200  (see  FIG. 1 ) includes at least a microprocessor  51 , an operational interface  52 , a driving system  53 , an antenna unit  54  (for transmitting/receiving), a satellite signal processing circuit  55 , a positioning unit  56 , a memory unit  57 , a control signal processing circuit  58  and a mobile digital signal receiving/transmitting unit  59 . Similarly, three prospective satellites  300 ,  300   a , and  300   b  are feasible in the space. 
         [0058]    The operational interface  52  coupled with the microprocessor  51  can be an operation panel. The driving system  53  includes a driving control circuit  531  and a driving unit  532 . The driving control circuit  531  is coupled electrically with the microprocessor  51 , and the driving unit  532  is coupled electrically with the driving control circuit  531  and the antenna unit  54 . The antenna unit  54  further includes a DVB-S antenna  541  and a DVB-T antenna  542 , in which the DVB-S antenna  541  can be a dish or flat antenna. In the present invention, the driving unit  532  can be a step motor for driving both the DVB-S antenna  541  and the DVB-T antenna  542 . 
         [0059]    The satellite signal processing circuit  55  includes a tuner  551  and a decoder  552 . The tuner  551  is coupled with the antenna unit  54 , and the decoder  552  is coupled in between with the tuner  551  and the microprocessor  51 . The positioning unit  56  includes a GPS system  561 , a GPS antenna  562  and a vehicle position-sensing unit  563 . The GPS system  561  couples in between with the GPS antenna  562  and the microprocessor  51 . The vehicle position-sensing unit  563  couples the microprocessor  51  and further includes a gyroscope  5631  and a gravity-sensing element  5632 . 
         [0060]    The memory unit  57  coupled with the microprocessor  51  further includes an operational program  571 , a satellite coordinate memory area  572  and a vehicle coordinate memory area  573 . The control signal processing circuit  58  includes a control signal amplifier  581  and a control signal driving circuit  582 . The control signal amplifier  581  is coupled with the microprocessor  51 . The control signal driving circuit  582  is coupled in middle with the control signal amplifier  581 , the mobile digital signal receiving/transmitting unit  59  and the antenna unit  54 . 
         [0061]    In this embodiment shown in  FIG. 9 , the operational interface  52  is utilized to set up a scanning pattern (for example, a horizontal scanning or a vertical scanning) and other related parameters (such as the range of a scanning angle, the angular increment in scanning, the scanning frequency and so on). The operational interface  52  purposely send a scan-driving signal S 1 ′ to the processing unit  51 . According to the signal S 1 ′, the processing unit  51  would activate the driving unit  532  through the driving-control circuit  531  to drive the DVB-S antenna  541  for a space scanning in accordance with the preset scan pattern and scan parameters. During the space scanning, proper scan data is obtained by receiving the satellite signal S 2 ′ sent from the satellite. Then, by analyzing the scanning data and the local peak values, the satellite coordinate of the target satellite can be realized. The satellite coordinate is further stored into the satellite coordinate memory area  572  of the memory  57 . For the scanning patterns and the definition of the satellite coordinate system are the same in the first and the second embodiments of the antenna system in accordance with the present invention, the related details would be omitted herein. 
         [0062]    Similarly, with the satellite scanning in process, the vehicle  200  can be still in motion. Namely, the vehicle coordinate may be altered from time to time during the satellite scanning. To ensure the accuracy in locating the satellite, the real-time vehicle coordinate of the moving vehicle  200  shall be taken into calculation. 
         [0063]    In the scanning, the GPS system  561 , through the GPS antenna  562 , receives a dynamic position signal S 3 ′ from a GPS satellite  400 . The signal S 3 ′ is then sent to the processing unit  51  for generating a satellite position coordinate to coordinate the vehicle  200 . In the mean time, the vehicle position-sensing unit  563  can determine a vehicle position for the vehicle  200 , and a dynamic position signal S 4 ′ according to the vehicle position is formed and further sent to the processing unit  51 . The vehicle position includes a vehicle azimuth angle and a vehicle elevation angle, in which the azimuth angle can be determined by the gyroscope  5631  and the elevation angle by the gravity-sensing element  5632 . Both the satellite position coordinate and the vehicle position are recorded into the vehicle coordinate memory area  573  of the memory unit  57 . Further, each of the satellite coordinates is assigned an individual satellite number as shown in  FIG. 8 . 
         [0064]    While the vehicle  200  moves to a new location for the user to lock on another satellite after finishing the preceding scanning, detecting and recording, the operational interface  52  is used to select the satellite number and send a lock-on signal S 5 ′ to the processing unit  51 . Then, by mimicking the aforesaid description about the first embodiment, an antenna control signal S 6 ′ is sent to the driving-control circuit  531 . The driving-control circuit  531  would then send a driving signal S 7 ′ to the driving unit  532  for properly driving the DVB-S antenna  541  to point at the purpose satellite. 
         [0065]    In the case that the user is to control the mobile digital signal receiving/transmitting unit  59 , the operational interface  52  is applied to make the processing unit  51  send a control signal S 8 ′ to the control signal amplifier  581 . The control signal amplifier  581  would then amplify the control signal S 8 ′ and send the amplified signal to the control signal driving circuit  582  for accordingly control the mobile digital signal receiving/transmitting unit  59 . 
         [0066]    Prior to receiving the satellite signal S 2 ′, the microprocessor  51  downloads at least a digital video data from the memory unit  57 . The digital video signal is transformed into a DVB-T video signal S 9 ′ by the mobile digital signal receiving/transmitting unit  59  to be further broadcasted to reach the digital TVs  500 ,  500   a  and  500   b . Meanwhile, the DVB-T antenna  542  is used to receive the foreign DVB-T video signals and further to restore the DVB-T signals into the memory unit  57  by the processing unit  51 . Else, the mobile digital signal receiving/transmitting unit  59  can transform the foreign DVB-T video signal into the respective DVB-T video signal S 9 ′ for further broadcasting. 
         [0067]    As soon as the satellite signal S 2 ′ is received, the processing unit  51  downloads at least a digital video data from the memory unit  57 . The digital video signal is transformed into a DVB-S satellite signal S 2 ′ or a DVB-T video signal S 9 ′ by the mobile digital signal receiving/transmitting unit  59 . Then, the DVB-S satellite S 2 ′ is sent to the locked-on satellite  300 ,  300   a  or  300   b , while the DVB-T video signal S 9 ′ is sent by the mobile digital signal receiving/transmitting unit  59  to be received by the digital TVs  500 ,  500   a  or  500   b.    
         [0068]    In the mean time, the locked-on satellite (any of satellite  300 ,  300   a  and  300   b ) sends the satellite signal S 2 ′ to the tuner  551  via the DVB-S antenna  541  for further modulation. The tuned signal S 2 ′ is then decoded by the decoder  552  and further sent to the processing unit  51  for being transformed into the respective digital satellite (program) data to be stored in the memory unit  57 . 
         [0069]    In addition, the locked-on satellite also send the satellite signal S 2 ′ via the DVB-S antenna  541  to the mobile digital signal receiving/transmitting unit  59  so as to have the signal S 2 ′ being transformed into the respective DVB-T video signal S 9 ′. The DVB-T video signal S 9 ′ is further broadcasted to be received by the digital TVs  500 ,  500   a  and  500   b . To the skill person in the art, the control signal S 8  for controlling the mobile digital signal receiving/transmitting unit  59  is fully understood to be able to help control the transformation and transmission between the signal S 2 ′ and the signal S 9 ′. 
         [0070]    Referring now to  FIG. 10  and  FIG. 11 , continuing flowcharts applicable to both the aforesaid first and second embodiments of the antenna system in accordance with the present invention are shown. Also, refer to  FIG. 2  for the following description. 
         [0071]    As shown, to work with the first embodiment, the operational interface  12  is firstly used to generate a scan-driving signal S 1  and further to send the S 1  to the processing unit  11  (Step  110 ). The S 1  is used to have the processing unit  11  to initiate the DVB-S antenna  21  to perform a space scanning (Step  120 ). 
         [0072]    Then, the DVB-S antenna  21  receives satellite signal S 2  from the satellite  300 ,  300   a  or  300   b  (Step  130 ). The received satellite signal S 2  is used to realize the individual signal strengths with respect to plural scan coordinates (P 00 -P 33  for example) (Step  140 ). A table as shown in  FIG. 4  to present the scan result is thus formed by pairing the signal strengths with the respective scan coordinates (Step  150 ). 
         [0073]    An analysis is performed upon the scan result (Step  160 ) so as to determine if or not a local peak value exists (Step  170 ). If negative, return back to perform Step  160  again. If positive, determine whether the peak value is a result of perturbation or signal interface (Step  180 ). If positive in Step  180 , then go back to perform Step  160  again. If negative in Step  180 , record/capture the scan coordinate with respect to the instant peak value (Step  190 ). 
         [0074]    Refer now to  FIG. 11 . As soon as the effective scan coordinate is confirmed, the satellite coordinate is then determined (Step  210 ) from the scan coordinate. Also, in Step  210 , the dynamic position signal S 3  from the GPS satellite and the dynamic position signal S 4  for the vehicle position are received for realizing the respective vehicle coordinate of the antenna, in which the vehicle coordinate includes the satellite position coordinate and the vehicle position. 
         [0075]    In Step  220 , store the satellite coordinate and the vehicle coordinate into the satellite coordinate memory area  162  and the vehicle coordinate memory area  163  of the memory unit  16 , respectively. 
         [0076]    Then, the operational interface  12  is used again to choose the target satellite to be locked on. As soon as the target satellite is determined, a lock-on signal S 5  is sent to the processing unit  11 . Accordingly, the processing  11  then captures the satellite coordinate with respect to the target satellite (Step  230 ). In the following Step  240 , the processing unit  11  sends the antenna control signal S 6  to the driving control circuit  13 , according to the satellite coordinate and the vehicle coordinate. In accordance with the S 6 , the driving control circuit  13  is then to send the driving signal S 7  to the driving unit  3  (Step  250 ). Finally, the driving unit  3  would drive the DVB-S antenna  21  to point at the target satellite, according to the S 7  (Step  260 ). 
         [0077]    By providing the antenna system of the present invention, real-time and precise coordinates of the antenna and the carrier vehicle can be obtained. Upon such an arrangement, possible position deviations resulted from aging, wearing and antenna movement can then be effectively compensated. Thereby, accuracy in tracking the satellite and quality in satellite communication can then be ensured. 
         [0078]    While the present invention has been particularly shown and described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes in form and detail may be without departing from the spirit and scope of the present invention.