Patent Publication Number: US-2023163837-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 the satellite communication earth station may give radio wave interference for other satellites. 
     Unfortunately, in correcting the direction of the antenna such that no radio wave interference is given to other satellites and then resuming communication, the existing antenna needs to be reset from the position and the direction in an initial state, taking time for the setting. 
     An object of the present disclosure is to provide a satellite communication earth station and a communication control method capable of reducing time taken to reset the direction of an antenna, which has changed due to disturbance, to a predetermined direction. 
     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, a minimum control calculation unit that calculates control to minimize a drive amount driven by the drive unit to adjust the azimuth angle, the elevation angle, and the polarization angle of the antenna at present to the communication satellite when the determination unit determines that the change from the initial setting value to the predetermined threshold value or more is made, and an execution unit that executes the control calculated by the minimum control calculation unit. 
     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, 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, calculating control to minimize a drive amount driven to adjust the current azimuth angle, the elevation angle, and the polarization angle of the antenna to the communication satellite when it is determined that the change from the initial setting value to the predetermined threshold value or more is made, and executing the calculated control. 
     Effects of the Invention 
     The present disclosure allows for reducing time to set the direction of an antenna, which has changed due to disturbance, to a predetermined direction. 
    
    
     
       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 diagram illustrating control calculated by a minimum control calculation unit and stored in a control item storage unit. 
         FIG.  6    is a flowchart illustrating an operation example of the satellite communication earth station according to the embodiment. 
         FIG.  7    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 , a control unit  18 , and a control item storage unit  19 . 
     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 . Moreover, the detection unit  14  detects the longitude, the latitude, the altitude, the azimuth, and the inclination of the antenna  13  even after elapse of a predetermined time after a stop processing unit  182 , which will be described later, causes the transmission of radio waves from the antenna  13  to stop. 
     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  ( FIG.  2   ) 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  ( FIG.  2   ) includes, for example, a determination unit  181 , a stop processing unit  182 , a minimum control calculation unit  183 , and an execution unit  184  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. 
     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 minimum control calculation unit  183  calculates control (minimum control) to minimize the drive amount by which the drive unit  16  drives the current azimuth angle, the elevation angle, and the polarization angle of the antenna  13  in accordance with the communication satellite  20  and causes the control item storage unit  19  to store the calculation result. 
     For example, the minimum control calculation unit  183  performs an arithmetic operation to specify control of reducing the drive amounts of the azimuth angle control motor  161 , the elevation angle control motor  162 , and the polarization angle control motor  163  such that a time taken to adjust the current azimuth angle, the elevation angle, and the polarization angle of the antenna  13  in accordance with the communication satellite  20  is minimized. 
       FIG.  5    is a diagram illustrating control (control items) calculated by the minimum control calculation unit  183  and stored in the control item storage unit  19 . As illustrated in  FIG.  5   , in a case in which each of the GNSS receiver  141 , the azimuth sensor  142 , and the acceleration sensor  143  performs detection again, the minimum control calculation unit  183  calculates only the necessary minimum drive amount to reset the direction of the antenna  13 , which has changed due to disturbance, to a predetermined direction. 
     The control item storage unit  19  also stores a change (an item that requires to be redetected) due to disturbance of the antenna  13 . Also, the control item storage unit  19  also stores the control motor to control again. The circle (◯) illustrated in  FIG.  5    denotes a correspondence relationship. 
     In other words, the minimum control calculation unit  183  calculates control for driving only a control motor corresponding to the minimum drive amount from among the azimuth angle control motor  161 , the elevation angle control motor  162 , and the polarization angle control motor  163 . 
     In a case in which only the polarization angle control motor  163  has deviated from the initial setting value when each of the GNSS receiver  141 , the azimuth sensor  142 , and the acceleration sensor  143  performs detection again, for example, the minimum control calculation unit  183  calculates control to drive only the polarization angle control motor  163 . 
     In other words, in a case in which only the polarization angle control motor  163  that has deviated from the initial setting value is to be adjusted again, the minimum control calculation unit  183  acquires information regarding the latitude, the longitude, and the altitude again from the GNSS receiver  141  but does not acquire new information from the azimuth sensor  142  and the acceleration sensor  143 . Also, the minimum control calculation unit  183  drives only the polarization angle control motor  163  and calculates control of not driving the azimuth angle control motor  161  and the elevation angle control motor  162 . 
     Also, the minimum control calculation unit  183  may perform an arithmetic operation of specifying control to minimize the drive amounts themselves or the numbers of control items of the azimuth angle control motor  161 , the elevation angle control motor  162 , and the polarization angle control motor  163 . 
     Note that it is assumed that the minimum control calculation unit  183  calculates the control to minimize the drive amount based on the longitude, the latitude, the altitude, the azimuth, and the inclination of the antenna  13  detected by the detection unit  14  after elapse of a predetermined time after the stop processing unit  182  causes the transmission of radio waves from the antenna  13  to be stopped. 
     The execution unit  184  ( FIG.  2   ) reads the control calculated by the minimum control calculation unit  183  from the control item storage unit  19  and executes the control after elapse of the predetermined time after the stop processing unit  182  causes the transmission of radio waves from the antenna  13  to be stopped. 
     Next, an operation example of the satellite communication earth station  10  will be described.  FIG.  6    is a flowchart illustrating an operation example of the satellite communication earth station  10  according to an embodiment. 
     If the satellite communication earth station  10  starts communication with the communication satellite  20 , and the detection unit  14  detects the latitude, the longitude, 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 detection result of the detection unit  14  as an initial setting value (S 100 ). 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. 
     Then, the control unit  18  calculates a direction and the like (the azimuth angle, the elevation angle, and the polarization angle) 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 ) (S 102 ). 
     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. At this time, the minimum control calculation unit  183  waits for elapse of a predetermined time after the stop processing unit  182  causes the transmission of radio waves from the antenna  13  to be stopped. Here, the predetermined time is assumed to be a time until the aforementioned change is stabilized. 
     In the processing in S 116 , the detection unit  14  redetects the latitude, the longitude, the altitude, the azimuth, and the inclination of the antenna  13  (or the satellite communication earth station  10 ) after elapse of a predetermined time (detection process after elapse of time). For example, the detection unit  14  redetects the corresponding latitude, the longitude, the altitude, the azimuth, and the inclination based on the change (the item that requires to be redetected) stored in the control item storage unit  19 . 
     In the processing in S 118 , the minimum control calculation unit  183  calculates control (minimum control) to minimize the drive amount (a drive time, for example) based on the longitude, the latitude, the altitude, the azimuth, and the inclination of the antenna  13  detected by the detection unit  14  after elapse of a predetermined time after the stop processing unit  182  causes the transmission of radio waves from the antenna  13  to be stopped. Note that the minimum control calculation unit  183  causes the control item storage unit  19  to store the calculation result. 
     In the processing in S 120 , the control unit  18  executes the minimum control using the execution unit  184  based on the calculation result stored in the control item storage unit  19  and returns to the processing in S 106 . 
     In other words, the satellite communication earth station  10  identifies which of the detection results has changed from among the results detected by the GNSS receiver  141 , the azimuth sensor  142 , and the acceleration sensor  143  or identifies which of control values of control motors has changed. Then, the satellite communication earth station  10  redetects of only the value of the sensor that has changed or control only on the control motor, the control value of which has changed, again to minimize the control for readjustment performed on the antenna  13 . 
     Thus, the satellite communication earth station  10  can shorten the time taken to reset the direction of the antenna  13 , which has changed due to disturbance, to a predetermined direction by the minimum control calculation unit  183  calculating the minimum control and the execution unit  184  executing the minimum control. 
     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.  7    is a diagram illustrating a hardware configuration example of the satellite communication earth station  10  according to the embodiment. As illustrated in  FIG.  7   , 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.  7   . 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 
           19  Control item storage 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  Minimum control calculation unit 
           184  Execution unit