Patent Publication Number: US-2023142947-A1

Title: Satellite communication earth station and communication control method

Description:
TECHNICAL FIELD 
     The present disclosure relates to a satellite communication earth station and a communication control method. 
     BACKGROUND ART 
     An existing satellite communication earth station that performs wireless communication with a communication satellite includes a global navigation satellite system (GNSS) receiver, an azimuth sensor, and an acceleration sensor and detects a latitude, a longitude, and an altitude where the satellite communication earth station is located, an azimuth, and an inclination of a ground surface. 
     The GNSS includes a system that receives radio waves from satellites to measure the position, such as a global positioning system (GPS) and a quasi-zenith satellite system (QZSS). 
     Also, the satellite communication earth station holds in advance the position (the latitude, the longitude, and the altitude) of the communication satellite in a satellite position storage unit and calculates a direction directed from the satellite communication earth station to the communication satellite (satellite direction) in accordance with the latitude, the longitude, and the altitude of the communication satellite that is a communication counterpart and the latitude, the longitude, and the altitude of the satellite communication earth station, the azimuth, and the inclination of the ground surface when the satellite communication earth station starts communication. 
     Then, the satellite communication earth station calculates a rotation angle of an azimuth angle control motor of an antenna, a rotation angle of an elevation angle control motor, and a rotation angle of a polarization angle control motor such that the antenna is directed to the direction of the communication satellite and performs setting to direct the antenna to the communication satellite. This allows the satellite communication earth station to communicate with the communication satellite (see PTL 1, for example). 
     CITATION LIST 
     Patent Literature 
     
         
         Patent Document 1: Japanese Patent No. 5592983 
       
    
     SUMMARY OF THE INVENTION 
     Technical Problem 
     A GNSS receiver included in the satellite communication earth station receives signals transmitted by a navigation satellite and calculates the latitude, the longitude, and the altitude of the satellite communication earth station. However, if the number of satellites from which signals can be received is small, for example, a difference (error) may be caused between the calculated latitude, the longitude, and the altitude of the satellite communication earth station and an actual position (the latitude, the longitude, and the altitude). 
     Also, the satellite communication earth station adjusts the direction of the antenna to the communication satellite before communication in accordance with the position of the satellite communication earth station. In other words, if a difference is caused between the calculated position of the satellite communication earth station and the actual position, then the satellite communication earth station cannot accurately direct the antenna to the communication satellite and cannot perform communication. 
     An object of the present disclosure is to provide a satellite communication earth station and a communication control method capable of preventing time taken to direct an antenna to a communication satellite from increasing due to calculation accuracy of the position of the satellite communication earth station. 
     Means for Solving the Problem 
     A satellite communication earth station according to an aspect of the present disclosure for adjusting an azimuth angle, an elevation angle, and a polarization angle of an antenna to a communication satellite and then transmitting and receiving a radio wave between the antenna and the communication satellite includes a detection unit that detects a longitude, a latitude, an altitude, an azimuth, and an inclination of the antenna, a drive unit that drives the antenna to adjust the azimuth angle, the elevation angle, and the polarization angle of the antenna to the communication satellite in accordance with the longitude, the latitude, the altitude, the azimuth, or the inclination detected by the detection unit, a determination information acquisition unit that acquires determination information necessary to determine accuracy of detection of the longitude, the latitude, and the altitude of the antenna detected by the detection unit, a determination unit that determines whether the accuracy of detection of the longitude, the latitude, and the altitude detected by the detection unit is in a necessary and sufficient level in accordance with the determination information acquired by the determination information acquisition unit, and a stop processing unit that stops transmission of the radio wave from the antenna when the determination unit determines that the accuracy of detection of the longitude, the latitude, and the altitude is not in the necessary and sufficient level. The detection unit detects the longitude, the latitude, the altitude, the azimuth, and the inclination of the antenna also after elapse of a predetermined time after the stop processing unit stops the transmission of the radio wave from the antenna, and the drive unit drives the antenna to adjust the azimuth angle, the elevation angle, and the polarization angle of the antenna to the communication satellite in accordance with the longitude, the latitude, the altitude, the azimuth, and the inclination of the antenna detected by the detection unit after elapse of the predetermined time after the stop processing unit stops the transmission of the radio wave from the antenna. 
     A communication control method according to an aspect of the present disclosure for controlling communication of a satellite communication earth station for adjusting an azimuth angle, an elevation angle, and a polarization angle of an antenna to a communication satellite and then transmitting and receiving a radio wave between the antenna and the communication satellite includes detecting a longitude, a latitude, an altitude, an azimuth, and an inclination of the antenna, driving the antenna to adjust the azimuth angle, the elevation angle, and the polarization angle of the antenna to the communication satellite in accordance with the detected longitude, latitude, altitude, azimuth, or inclination, acquiring determination information necessary to determine accuracy of detection of the detected longitude, latitude, and altitude of the antenna, determining whether the accuracy of detection of the longitude, the latitude, and the altitude is in a necessary and sufficient level in accordance with the acquired determination information, stopping transmission of the radio wave from the antenna when it is determined that the accuracy of detection of the longitude, the latitude, and the altitude is not in the necessary and sufficient level, detecting the longitude, the latitude, the altitude, the azimuth, and the inclination of the antenna also after elapse of a predetermined time after the transmission of the radio wave from the antenna is stopped, and driving the antenna to adjust the azimuth angle, the elevation angle, and the polarization angle of the antenna to the communication satellite in accordance with the longitude, the latitude, the altitude, the azimuth, and the inclination of the antenna detected after elapse of the predetermined time after the transmission of the radio wave from the antenna is stopped. 
     Effects of the Invention 
     The present disclosure allows for preventing time taken to direct the antenna to the communication satellite from increasing due to calculation accuracy of the position of the satellite communication earth station. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG.  1    is a diagram illustrating, as an example, an overview of a satellite communication system according to an embodiment. 
         FIG.  2    is a functional block diagram illustrating, as an example, an overview of functions that a satellite communication earth station has according to the embodiment. 
         FIG.  3    is a diagram illustrating, as an example, determination information acquired by a determination information acquisition unit. 
         FIG.  4    is a diagram illustrating, as an example, a threshold value held by a determination unit. 
         FIG.  5    is a flowchart illustrating an operation example of the satellite communication earth station according to the embodiment. 
         FIG.  6    is a diagram illustrating a hardware configuration example of the satellite communication earth station according to the embodiment. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, an embodiment of a satellite communication system will be described using the drawings.  FIG.  1    is a diagram illustrating, as an example, an overview of a satellite communication system  1  according to an embodiment. The satellite communication system  1  is, for example, a system in which a plurality of satellite communication earth stations  10  perform wireless communication via a communication satellite  20 . 
     Also, communication devices  30  are connected to each satellite communication earth station  10 . In other words, the satellite communication system  1  is a system that enables the plurality of communication devices  30  to perform communication via the satellite communication earth stations  10  and the communication satellite  20 . In addition, the satellite communication earth stations  10  adjust azimuth angles, elevation angles, and polarization angles of antennas that the satellite communication earth stations  10  themselves include in accordance with the communication satellite  20  and then transmit and receive radio waves to and from the communication satellite  20 . 
       FIG.  2    is a functional block diagram illustrating, as an example, an overview of functions that each satellite communication earth station  10  has according to the embodiment. As illustrated in  FIG.  2   , the satellite communication earth station  10  includes a satellite position storage unit  11 , a transmission/reception unit  12 , an antenna  13 , a detection unit  14 , a detection data storage unit  15 , a drive unit  16 , a control value storage unit  17 , and a control unit  18 . 
     The satellite position storage unit  11  stores, for example, the position (the latitude, the longitude, and the altitude) of the communication satellite  20  ( FIG.  1   ), which is a stationary satellite, in advance. Note that the communication satellite  20  is not limited to a stationary satellite and may be a moving satellite. 
     The transmission/reception unit  12  transmits and receives signals to and from the communication satellite  20  via the antenna  13 . For example, the transmission/reception unit  12  modulates data transmitted from the satellite communication earth station  10  to the communication satellite  20  into a radio signal and outputs the radio signal to the antenna  13 . Also, the transmission/reception unit  12  demodulates the radio signal received by the antenna  13  from the communication satellite  20 . 
     Note that signals transmitted and received by the transmission/reception unit  12  include data (main signal) and control signals used to control line setting and the like among the plurality of satellite communication earth stations  10 . 
     The antenna  13  is provided at an upper portion of the satellite communication earth station  10 , for example, such that the azimuth angle, the elevation angle, and the polarization angle thereof become variable, and transmits and receives radio waves to and from the communication satellite  20 . 
     The detection unit  14  includes, for example, a GNSS receiver  141 , an azimuth sensor  142 , and an acceleration (gravity) sensor  143 . 
     The GNSS receiver  141  detects the latitude, the longitude, and the altitude of the antenna  13  or the satellite communication earth station  10  through reception of signals from navigation satellites, such as a GPS and a QZSS, for example, and outputs the detected latitude, the longitude, and the altitude to the control unit  18 . For example, a GNSS such as a GPS specifies the reception position by simultaneously receiving GNSS signals from four or more navigation satellites. 
     The azimuth sensor  142  detects an azimuth in which the antenna  13  or the satellite communication earth station  10  is directed and outputs the detected azimuth to the control unit  18 . The acceleration sensor  143  detects the inclination of the antenna  13  or the satellite communication earth station  10  with respect to an installation surface and outputs the detected inclination to the control unit  18 . 
     Although it is assumed that the detection unit  14  detects each value regarding the antenna  13  here, the detection unit  14  may detect values regarding the satellite communication earth station  10  and regard the values substantially as values for the antenna  13  or may detect values that can be converted into values for the antenna  13 . 
     Also, the detection unit  14  performs the detection at a predetermined cycle when the satellite communication earth station  10  performs communication with the communication satellite  20 . Moreover, the detection unit  14  detects the latitude and the longitude, the azimuth, and the inclination of the antenna  13  even after elapse of a predetermined time after a stop processing unit  183 , which will be described below, causes the transmission of radio waves from the antenna  13  to stop (detection process after elapse of time). 
     The detection data storage unit  15  stores the latitude, the longitude, the altitude, the azimuth, and the inclination detected by the detection unit  14 . Note that because the detection unit  14  detects the latitude, the longitude, the altitude, the azimuth, and the inclination at the predetermined cycle when the satellite communication earth station  10  performs communication, the detection data storage unit  15  periodically stores each of the latitude, the longitude, the altitude, the azimuth, and the inclination detected by the detection unit  14 . 
     The drive unit  16  includes an azimuth angle control motor  161 , an elevation angle control motor  162 , and a polarization angle control motor  163 . 
     The azimuth angle control motor  161  drives the antenna  13  such that the azimuth (a rotation angle from the initial setting) in which the antenna  13  is directed is adjusted in accordance with the communication satellite  20  that is a target of communication in accordance with control performed by the control unit  18 . The elevation angle control motor  162  drives the antenna  13  such that the elevation angle (a rotation angle from the initial setting) of the antenna  13  is adjusted in accordance with the communication satellite  20  that is a target of communication in accordance with control performed by the control unit  18 . The polarization angle control motor  163  drives the antenna  13  such that the polarization angle (a rotation angle from the initial setting) of radio waves transmitted and received by the antenna  13  is adjusted in accordance with the communication satellite  20  that is a target of communication in accordance with control performed by the control unit  18 . 
     For example, the drive unit  16  performs driving such that the azimuth angle, the elevation angle, and the polarization angle of the antenna  13  are adjusted in accordance with the communication satellite  20  based on the latitude, the longitude, and the altitude, the azimuth, and the inclination detected by the detection unit  14 . Also, the drive unit  16  performs driving such that the azimuth angle, the elevation angle, and the polarization angle of the antenna  13  are adjusted in accordance with the communication satellite  20  based on the longitude and the latitude, the azimuth, and the inclination of the antenna  13  detected by the detection unit  14  even after elapse of predetermined time after the stop processing unit  183 , which will be described below, causes the transmission of radio waves from the antenna  13  to stop (drive process after elapse of time). Moreover, the drive unit  16  may drive (adjust) the antenna  13  at a predetermined cycle when the satellite communication earth station  10  performs communication with the communication satellite  20 . 
     The control value storage unit  17  stores each control value (a rotation angle from the initial setting) indicating the amount by which the drive unit  16  has driven the antenna  13 . 
     The control unit  18  includes, for example, a determination information acquisition unit  181 , a determination unit  182 , and a stop processing unit  183  and controls each component constituting the satellite communication earth station  10 . Also, it is assumed that the control unit  18  has a function of calculating a direction directed from the antenna  13  to the communication satellite  20  based on the latitude, the longitude, the altitude, the azimuth, and the inclination of the antenna  13  (or the satellite communication earth station  10 ). 
     The determination information acquisition unit  181  acquires determination information necessary to determine the accuracy of the detection of the longitude and the latitude of the antenna  13  detected by the detection unit  14 . For example, the determination information acquisition unit  181  may acquire, as determination information necessary to determine the accuracy of GNSS positioning, at least any of the number of communication satellites that have received GNSS signals, reception levels of radio waves received from each communication satellite (reception intensity), and the elevation angles and the azimuth relative to the communication satellites. 
       FIG.  3    is a diagram illustrating, as an example, determination information acquired by the determination information acquisition unit  181 . As illustrated in  FIG.  3   , the determination information acquisition unit  181  acquires the number of communication satellites that receive GNSS signals by acquiring identification numbers (satellite numbers) of the communication satellites. Then, the determination information acquisition unit  181  acquires the radio wave reception level and the elevation angle and the azimuth relative to the communication satellites for each identification number of the communication satellites. 
     The determination unit  182  determines whether the accuracy of the detection of the longitude and the latitude detected by the detection unit  14  is in a necessary sufficient level based on the determination information acquired by the determination information acquisition unit  181 . For example, the determination unit  182  determines whether the accuracy of the detection of the longitude and the latitude detected by the detection unit  14  is in a necessary sufficient level based on at least any of the number of communication satellites, from which the satellite communication earth station  10  receives radio waves, reception levels of radio waves received from the communication satellites, and the elevation angles and the azimuths relative to the communication satellites. 
     For example, the determination unit  182  holds a threshold value for determining whether the accuracy of the detection of the longitude and the latitude is in a necessary sufficient level and performs the determination using the threshold value. 
       FIG.  4    is a diagram illustrating, as an example, the threshold value held by the determination unit  182 . As illustrated in  FIG.  4   , the determination unit  182  holds a threshold value for each of the number of reception satellites, the reception level, and the elevation angle, for example. 
     For example, the determination unit  182  determines whether the number of communication satellites with reception levels of equal to or greater than 45 dB and with elevation angles of equal to or greater than 45 degrees is six or more and determines that the detection accuracy of the detection unit  14  is in a necessary sufficient level in a case where all values are equal to or greater than the threshold values. 
     Note that the satellite communication earth station  10  may image a zenith direction using a camera and determine whether the accuracy of the detection of the longitude and the latitude is in a necessary sufficient level using conditions of obstacles such as surrounding buildings and information regarding an imaging clock time. 
     The stop processing unit  183  causes the transmission of radio waves from the antenna  13  to stop in a case where the determination unit  182  determines that the accuracy of the detection of the longitude and the latitude is not in the necessary sufficient level. 
     Then, in a case where the accuracy of the detection of the longitude and the latitude is not in the necessary sufficient level (the measurement error of the satellite communication earth station is equal to or greater than a predetermined value), the control unit  18  performs control such that the drive unit  16  does not drive the antenna  13 . 
     In other words, in a case where it is predicted to be impossible to accurately adjust the direction of the antenna  13  in accordance with the communication satellite  20  based on the result of the GNSS positioning, the satellite communication earth station  10  causes the processing of adjusting the direction relative to the antenna  13  to stop. Also, in a case where it is expected to be possible to accurately adjust the direction relative to the antenna  13 , the satellite communication earth station  10  restarts the processing of adjusting the direction relative to the antenna  13  and shortens the final processing time. 
     Next, an operation example of the satellite communication earth station  10  will be described.  FIG.  5    is a flowchart illustrating an operation example of the satellite communication earth station  10  according to an embodiment. 
     As illustrated in  FIG.  5   , the detection unit  14  performs each kind of detection (S 100 ), and the determination information acquisition unit  181  acquires the determination information (S 102 ), in the satellite communication earth station  10 . 
     Then, the determination unit  182  determines whether the detection accuracy is in a necessary sufficient level (S 104 ) and moves on to processing in S 106  in a case where it is determined that the detection accuracy is not in the necessary sufficient level (S 104 : No), or moves on to processing in S 108  in a case where it is determined that the detection accuracy is in a necessary sufficient level (S 104 : Yes). 
     In the processing in S 106 , the detection unit  14  waits for elapse of a predetermined time after the stop processing unit  183  causes the transmission of radio waves from the antenna  13  to stop and returns to the processing in S 100 . 
     In the processing in S 108 , the GNSS receiver  141  detects the latitude, the longitude, and the altitude of the antenna  13  (S 108 ), the azimuth sensor  142  detects the azimuth of the antenna  13  (S 110 ), and the acceleration sensor  143  detects the inclination of the antenna  13  (S 112 ), in the satellite communication earth station  10 . 
     Then, the control unit  18  calculates a direction from the antenna  13  to the communication satellite  20  based on the detected latitude, longitude, and altitude, azimuth, and inclination of the antenna  13  (S 114 ). 
     Thereafter, the drive unit  16  performs driving such that the azimuth angle, the elevation angle, and the polarization angle of the antenna  13  are adjusted in accordance with the communication satellite  20  (S 116 ). In other words, the satellite communication earth station  10  sets the direction of the antenna  13  in accordance with the communication satellite  20 . 
     In this manner, the satellite communication earth station  10  causes the transmission of radio waves from the antenna  13  to stop in a case where it is determined that the accuracy of the detection of the longitude and the latitude is not in a necessary sufficient level and performs driving such that the azimuth angle, the elevation angle, and the polarization angle of the antenna  13  are adjusted in accordance with the communication satellite  20  based on the longitude and the latitude, the azimuth, and the inclination of the antenna  13  detected by the detection unit  14  after elapse of a predetermined time. The satellite communication earth station  10  can thus prevent the time taken to direct the direction of the antenna  13  to the communication satellite  20  from increasing due to accuracy of calculating the position of the satellite communication earth station  10 . 
     Also, the satellite communication earth station  10  may have a function of displaying the state of the antenna  13  and the state of each kind of processing to an operator. 
     Note that each function included in the satellite communication earth station  10 , the communication satellite  20 , and the communication device  30  may be partially or entirely configured with hardware or may be configured as a program to be executed by a processor such as a CPU. 
     In other words, the satellite communication system  1  according to the present disclosure can be achieved using a computer and the program, and it is possible to record the program in a storage medium or to provide the program through a network. 
       FIG.  6    is a diagram illustrating a hardware configuration example of the satellite communication earth station  10  according to the embodiment. As illustrated in  FIG.  6   , the satellite communication earth station  10  has functions of a computer with an input unit  50 , an output unit  51 , a communication unit  52 , a CPU  53 , a memory  54 , and an HDD  55  connected via a bus  56 , for example. Also, the satellite communication earth station  10  is adapted to be able to input and output data to and from the storage medium  57 . 
     The input unit  50  is, for example, a keyboard, a mouse, and the like. The output unit  51  is, for example, a display device such as a display. The communication unit  52  is, for example, a wireless network interface. 
     The CPU  53  controls each component constituting the satellite communication earth station  10  and performs the aforementioned processing. The memory  54  and the HDD  55  store data. The storage medium  57  is adapted to be able to store a received program and the like that causes the functions included in the satellite communication earth station  10  to be executed. Note that the architecture constituting the satellite communication earth station  10  is not limited to the example illustrated in  FIG.  6   . Also, the communication satellite  20  and the communication device  30  may also include configurations similar to that of the satellite communication earth station  10 . 
     REFERENCE SIGNS LIST 
     
         
           1  Satellite communication system 
           10  Satellite communication earth station 
           11  Satellite position storage unit 
           12  Transmission/reception unit 
           13  Antenna 
           14  Detection unit 
           15  Detection data storage unit 
           16  Drive unit 
           17  Control value storage unit 
           18  Control unit 
           20  Communication satellite 
           30  Communication device 
           50  Input unit 
           51  Output unit 
           52  Communication unit 
           53  CPU 
           54  Memory 
           55  HDD 
           56  Bus 
           57  Storage medium 
           141  GNSS receiver 
           142  Azimuth sensor 
           143  Acceleration sensor 
           161  Azimuth angle control motor 
           162  Elevation angle control motor 
           163  Polarization angle control motor 
           181  Determination information acquisition unit 
           182  Determination unit 
           183  Stop processing unit