Patent Publication Number: US-2023155667-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 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 
     PTL 1: JP 5425826 B 
     SUMMARY OF THE INVENTION 
     Technical Problem 
     Although the satellite communication earth station adjusts and fixes the direction of the antenna to the communication satellite before communication, the position of the satellite communication earth station may change during communication, or the rotation angle set by each control motor may be changed by force applied to the antenna. At this time, the antenna may be directed to a direction different from the communication satellite, and unfortunately, the satellite communication earth station may give radio wave interference for other satellites. 
     An object of the present disclosure is to provide a satellite communication earth station and a communication control method capable of preventing radio wave interference from being provided to other satellites when the direction of the antenna changes due to disturbance. 
     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, a determination unit that determines whether the longitude, the latitude, the altitude, the azimuth, or the inclination detected by the detection unit or the azimuth angle, the elevation angle, or the polarization angle driven by the drive unit makes a change from an initial setting value to a predetermined threshold value or more, and a stop processing unit that stops transmission of the radio wave from the antenna when the determination unit determines that the change from the initial setting value to the predetermined threshold value or more is made. 
     Also, 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, performing driving the antenna to adjust the azimuth angle, the elevation angle, and the polarization angle of the antenna to the communication satellite, determining whether the longitude, the latitude, the altitude, the azimuth, or the inclination detected or the azimuth angle, the elevation angle, or the polarization angle driven makes a change from an initial setting value to a predetermined threshold value or more, and stopping transmission of the radio wave from the antenna when it is determined that the change from the initial setting value to the predetermined threshold value or more is made. 
     Effects of the Invention 
     The present disclosure allows for preventing radio wave interference from being given to other satellites when the direction of the antenna changes due to disturbance. 
    
    
     
       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, each value stored in a detection data storage unit. 
         FIG.  4    is a diagram illustrating, as an example, each value stored in a control value storage 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 . 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 . 
     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 . In addition, it is assumed that the detection data storage unit  15  stores a threshold value (which will be described later) of the amount of change for each detection result of the detection unit  14  in advance. 
       FIG.  3    is a diagram illustrating, as an example, each value stored in the detection data storage unit  15 . The detection data storage unit  15  stores an initial setting value, a periodic detection value, and a change amount threshold value for each of the GNSS receiver  141 , the azimuth sensor  142 , and the acceleration sensor  143 , for example. 
     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  may perform the driving to adjust the direction of the antenna  13  based on the latitude, the longitude, the altitude, the azimuth, and the inclination detected by the detection unit  14 . In other words, 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 . 
       FIG.  4    is a diagram illustrating, as an example, each value stored in the control value storage unit  17 . The control value storage unit  17  stores an initial setting value, a periodic detection value, and a change amount threshold value for each of the azimuth angle control motor  161 , the elevation angle control motor  162 , and the polarization angle control motor  163 , for example. 
     The control unit  18  includes a determination unit  181 , a stop processing unit  182 , and a recovery control 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 unit  181  determines whether or not at least any of the longitude, the latitude, the altitude, the azimuth, or the inclination detected by the detection unit  14  or the azimuth angle, the elevation angle, or the polarization angle driven by the drive unit  16  has experienced a change that is equal to or greater than a predetermined threshold value from an initial setting value. 
     In a case in which the determination unit  181  determines that there has been a change that is equal to or greater than the predetermined threshold value from the initial setting value, the stop processing unit  182  stops the transmission of radio waves (the main signals and the control signals) from the antenna  13  (wave stop processing). Note that the stop processing unit  182  may cause the antenna  13  to stop the transmission of radio waves or may stop the transmission/reception unit  12  to stop the transmission. Moreover, the stop processing unit  182  may lower a transmission level such that no radio wave interferences are provided to other satellites by lowering a transmission power from the antenna  13  by  50  dB, for example, instead of performing the wave stop processing. 
     The recovery control unit  183  controls such that the drive unit  16  drives the antenna to adjust the azimuth angle, the elevation angle, and the polarization angle of the antenna  13  to the communication satellite  20  after elapse of a predetermined time after the stop processing unit  182  stops the transmission of radio waves from the antenna  13 . 
     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. 
     When the satellite communication earth station  10  receives data from the connected communication device  30 , for example, then the direction of the antenna  13  is set to be directed to the communication satellite  20  under control of the control unit  18 , and communication with the communication satellite  20  is started (S 100 ). 
     When the detection unit  14  detects the latitude, the longitude, and the altitude, the azimuth, and the inclination of the antenna  13  or the satellite communication earth station  10 , then the detection data storage unit  15  stores each of the detection results of the detection unit  14  as an initial setting value (S 102 ). For example, as illustrated as an example in  FIG.  3   , the detection data storage unit  15  stores the value “193.2” degrees as an initial setting value of the azimuth. 
     Also, if the drive unit  16  performs driving to direct the antenna  13  to the communication satellite  20 , then the control value storage unit  17  stores each control value of the drive unit  16  as an initial setting value (S 104 ). 
     Next, the determination unit  181  compares the periodic detection result of the detection unit  14  with the initial setting value (S 106 ) and determines whether or not a change in the detection result with respect to the initial setting value is equal to or greater than a threshold value (S 108 ). The determination unit  181  moves on to the processing in S 114  in a case in which it is determined that the change is equal to or greater than the threshold value (S 108 : Yes), or the determination unit  181  moves on to the processing in S 110  in a case in which it is determined that the change is not equal to or greater than the threshold value (S 108 : No). 
     In a case in which the initial setting value of the azimuth is “193.2” degrees, and the detection data storage unit  15  stores “2” as a change amount threshold value of the azimuth, and if the detection unit  14  detects a value “193.5” degrees as a detection value of the azimuth as illustrated in  FIG.  3   , for example, the determination unit  181  determines that the change is not equal to or greater than the threshold value. 
     Also, the determination unit  181  compares the periodic control value (adjustment value) of the drive unit  16  with the initial setting value (S 110 ) and determines whether or not the change of the control value with respect to the initial setting value is equal to or greater than a threshold value (S 112 ). The determination unit  181  moves on to the processing in S 114  in a case in which it is determined that the change is equal to or greater than the threshold value (S 112 : Yes), or the determination unit  181  returns to the processing in S 106  in a case in which it is determined that the change is not equal to or greater than the threshold value (S 112 : No). 
     In a case in which the initial setting value of the polarization angle is “10.7”, and the control value storage unit  17  stores “1.5” as a change amount threshold value of the polarization angle, and when the control value of the drive unit  16  in regard to the polarization angle is “10.6” as illustrated in  FIG.  4   , for example, the determination unit  181  determines that the change is not equal to or greater than the threshold value. 
     In the processing in S 114 , the stop processing unit  182  causes the transmission of radio waves (the main signals and the control signals) from the antenna  13  to be stopped. 
     Then, the recovery control unit  183  waits for a predetermined time ( 10  seconds, for example) in a state in which the transmission of radio waves from the antenna  13  is stopped (S 116 ) and then returns to the processing in S 110 . 
     In this manner, because the stop processing unit  182  stops the transmission of radio waves from the antenna  13  in a case where the determination unit  181  determines that a change from the initial setting value to the predetermined threshold value or more is made, the satellite communication earth station  10  can prevent radio wave interference from being given to other satellites when the direction of the antenna  13  changes due to disturbance. 
     Also, the satellite communication earth station  10  may be configured to include a camera sensor for capturing surroundings images, detect the amount of change in the images, and perform wave stop processing. In this case, the satellite communication earth station  10  may ignore some of changes in the images such as crossing of a person or a car, for example, in an image and detect changes in the images such as a change in background due to falling over of the host satellite communication earth station  10 . 
     Also, the satellite communication earth station  10  may be configured to include a distance sensor, measure the distances to surrounding buildings at a predetermined cycle, detect the amounts of change in distances, and perform wave stop processing. 
     Moreover, the changes regarding the antenna  13  are not limited to those of detection inside the satellite communication earth station  10 , and other devices mounted in the surroundings, a control center placed at a remote location, or the like may detect the changes. In this case, the changes detected by other devices or the control center are transmitted to the satellite communication earth station  10  via a communication line or the like, and the satellite communication earth station  10  performs wave stop processing. 
     Thus, the satellite communication system  1  can prevent the communication from being continued with a degraded communication quality due to a change in direction of the antenna  13  included in the satellite communication earth station  10 . 
     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. 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 unit 
           182  Stop processing unit 
           183  Recovery control unit