Patent Publication Number: US-2023155671-A1

Title: Transmitting radio wave confirmation method, mobile station device and transmitting radio wave confirmation program in satellite communication system

Description:
TECHNICAL FIELD 
     The present invention relates to technology for checking transmission radio waves when a portable ground station initially connects to a communications satellite in a satellite communication system in a situation where communication with a satellite telecommunications carrier is unavailable due to an event such as a large-scale disaster. 
     BACKGROUND ART 
     A very-small-aperture terminal (VSAT) system is known as satellite communication system provided with a portable ground station. A VSAT system uses a small, portable VSAT ground station provided with an antenna having a very small aperture to enable communication from locations where a communications satellite can be acquired, and consequently is utilized to secure communication during a disaster or the like. However, in the case of installing a portable ground station (referred to as a portable station), before putting the portable station into operation, it is necessary to adjust the antenna direction with respect to a target communications satellite and then perform an uplink access test (UAT) to check whether a connection with the target communications satellite is established with the correct antenna direction. In a UAT of the related art, the operator of the portable station adjusts properties such as the transmit level and the polarization angle of the portable station while receiving instructions from an operator of the satellite telecommunications carrier over a mobile phone or a satellite phone (for example, see Non-Patent Literature 1). Alternatively, a control station that controls settings and operations for the entire system, such as a plurality of portable stations and base stations constituting a satellite communication system, monitors properties such as the transmit level and the polarization angle through a test signal (UAT signal) transmitted from a portable station, and by remotely adjusting the transmit level and the polarization angle of the portable station using a dedicated control channel (common signaling channel (CSC)), the control station performs a remote UAT that does not require an operator of the portable station (for example, see Patent Literature 1). 
     CITATION LIST 
     Patent Literature 
     
         
         Patent Literature 1: Japanese Patent Laid-Open No. 2012-175217 
       
    
     Non-Patent Literature 
     
         
         Non-Patent Literature 1: Uplink Access Test Procedure (October 2009/SKY Perfect JSAT Corporation) 
       
    
     SUMMARY OF THE INVENTION 
     Technical Problem 
     In the technology of the related art, there is a problem of being unable to perform a UAT for a portable station in certain cases, such as when an operator of the satellite telecommunications carrier cannot be contacted due to an event such as a large-scale disaster, or in the case of a system in which the control station does not support all remote UAT functions. On the other hand, in cases where it is necessary to operate a portable station during a large-scale disaster, there is demand for a technology that checks whether properties such as the satellite acquisition state and transmission output are appropriate without affecting other radio communication users, even if a UAT cannot be performed with the satellite telecommunications carrier. 
     An objective of the present invention is to provide a transmission radio wave checking method for a satellite communication system, a portable station, and a transmission radio wave checking program capable of completing a UAT by receiving and checking a signal transmitted by a portable station and received back from a satellite, even in cases where a UAT cannot be performed with the satellite telecommunications carrier. 
     Means for Solving the Problem 
     One aspect of the present invention is a transmission radio wave checking method for a satellite communication system provided with a portable station, wherein the portable station executes a transmission process of transmitting a test signal and a control signal with a first polarization at a designated transmit level to a communications satellite, a reception process of receiving the test signal and the control signal transmitted back from the communications satellite with a second polarization orthogonal to the first polarization, and a control process of starting the transmission of the test signal and the control signal with the first polarization at a transmit level lower than a predetermined value, and raising the transmit level to a predetermined value while checking whether or not the test signal and the control signal received back from the satellite conform to a predetermined condition. 
     Another aspect of the present invention is a portable station used in a satellite communication system, the portable station comprising a transmission unit that transmits a test signal and a control signal with a first polarization at a designated transmit level to a communications satellite, a reception unit that receives the test signal and the control signal transmitted back from the communications satellite with a second polarization orthogonal to the first polarization, and a control unit that starts the transmission of the test signal and the control signal with the first polarization at a transmit level lower than a predetermined value, and raises the transmit level to a predetermined value while checking whether or not the test signal and the control signal received back from the satellite conform to a predetermined condition. 
     Also, a transmission radio wave checking program according to the present invention causes a computer to execute a process executed according to the transmission radio wave checking method. 
     Effects of the Invention 
     The transmission radio wave checking method for a satellite communication system, portable station, and transmission radio wave checking program according to the present invention is capable of completing a UAT by receiving and checking a signal transmitted by a portable station and received back from a satellite, even in cases where a UAT cannot be performed with the satellite telecommunications carrier. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG.  1    is a diagram illustrating an example of a satellite communication system common to the embodiments. 
         FIG.  2    is a diagram illustrating a configuration example for the case of an ordinary UAT. 
         FIG.  3    is a diagram illustrating another configuration example for the case of an ordinary UAT. 
         FIG.  4    is a diagram illustrating an example of a K u -band uplink channel. 
         FIG.  5    is a diagram illustrating a configuration example of a portable station (master station) according to a first embodiment. 
         FIG.  6    is a diagram illustrating a configuration example of a portable station (slave station) common to the embodiments. 
         FIG.  7    is a diagram illustrating an example of a UAT signal checking and adjustment process according to the first embodiment. 
         FIG.  8    is a diagram illustrating an example of a control signal checking and adjustment process according to the first embodiment. 
         FIG.  9    is a diagram illustrating a configuration example of a portable station (master station) according to a second embodiment. 
         FIG.  10    is a diagram illustrating an example of a UAT signal checking and adjustment process according to the second embodiment. 
         FIG.  11    is a diagram illustrating an example of a control signal checking and adjustment process according to the second embodiment. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, embodiments of a transmission radio wave checking method for a satellite communication system, a portable station, and a transmission radio wave checking program according to the present invention will be described with reference to the drawings. 
       FIG.  1    illustrates an example of a satellite communication system  100  common to the embodiments. Each of the embodiments herein assumes a satellite communication system  100  like the following, for example. Note that although a portable station  101  is described in the first embodiment and a portable station  101 - 1  is described in the second embodiment described later, but because the functions of the satellite communication system  100  are the same, the portable station is described herein as the portable station  101  which also includes the portable station  101 - 1 . The portable station  101  functions as a control station and also as a master station corresponding to a base station of an ordinary VSAT system, while a portable station  102  is a slave station corresponding to a VSAT ground station of an ordinary VSAT system. Additionally, the portable station  101  acting as a master station and the portable station  102  acting as a slave station construct a private network through P-P or P-MP communication, and the satellite communication system  100  is configured without an operation system provided by a control station or the like. For example, in the satellite communication system  100  in  FIG.  1   , the slave station (portable station  102 ) communicates with the master station by synchronizing with a control signal transmitted from the master station (portable station  101 ) through a communications satellite  103 . Note that in the case where there are a plurality of slave stations similar to the portable station  102 , the slave stations can communicate under control by the master station in a similar way. 
     In  FIG.  1   , because the satellite communication system  100  is provided with a plurality of portable ground stations (in  FIG.  1   , the portable station  101  and the portable station  102 ) that can be used if in a location where the communications satellite  103  is acquirable, the satellite communication system  100  is effective for securing communication during a disaster or the like. However, in the case of performing initial operations of a portable station, it is necessary to perform checking and adjustment work referred as an uplink access test (UAT) to check whether properties such as the satellite acquisition state and the transmission output are appropriate without affecting other satellite communication users. Note that in the case of using a portable station as a slave station, if a UAT is performed during initial operations and an acknowledgment is obtained from the satellite telecommunications carrier, a UAT does not have to be performed during later operations. However, in the case of using a portable station as a master station, it is necessary to perform a UAT every time operations are performed. For example,  FIG.  2    illustrates a configuration example for the case of an ordinary UAT. In an ordinary satellite communication system  800  provided with a portable station  801 , a base station  802 , a communications satellite  803 , and a satellite telecommunications carrier  804 , an operator of the portable station  801  contacts an operator of the satellite telecommunications carrier  804  over a mobile phone or a satellite phone, and the operator of the portable station  801  adjusts properties such as the transmit level and the polarization angle of a UAT signal (test signal) him- or herself. Alternatively,  FIG.  3    illustrates another configuration example for the case of an ordinary UAT. In the case of performing a UAT without an operator of the portable station  801 , an operator of a control station  805  contacts an operator of the satellite telecommunications carrier  804  and remotely controls the portable station  801  through a control signal (CSCO signal) from the base station  802  to adjust the transmit level and polarization angle of the UAT signal transmitted by the portable station  801 . 
     In contrast, in the satellite communication system  100  common to the embodiments illustrated in  FIG.  1   , even in cases where a UAT with the satellite telecommunications carrier cannot be performed due to a large-scale disaster or the like, one portable station (in  FIG.  1   , the portable station  101 ) from among a plurality of portable stations acts as a master station and performs the operations of a base station and a control station by itself, and receives a UAT signal and a control signal transmitted by the portable station  101  itself instead of the satellite telecommunications carrier and received back from the communications satellite  103 , and thereby can check and make adjustments similar to the case of an ordinary UAT. Here, the UAT includes two checking processes, namely a process of checking the UAT signal and a process of checking the control signal, and in the case where each signal conforms to a predetermined condition, the UAT is completed, and operation is started. Note that when the UAT is completed, the portable station  101  saves a UAT result together with the antenna direction and polarization angle state, which can be treated as evidence for starting operation of the portable station  101  on the basis of an appropriate UAT result. 
     In  FIG.  1   , the portable station  101  acting as the master station operates performs a UAT after completing adjustment of the antenna direction toward the communications satellite  103  every time the portable station  101  operates, whereas if the portable station  102  acting as a slave station has obtained an acknowledgment from the satellite telecommunications carrier, the portable station has performed a UAT according to a method of the related art during initial operations (when the device is used for the first time), the portable station  102  only has to adjust the antenna direction during subsequent operations, and does not need to perform a UAT every time the portable station  102  operates. The portable station  102  is an ordinary VSAT ground station that receives a control signal (CSCO signal) transmitted by the portable station  101  acting as the master station instead of the base station  802 , and is capable of adjusting the antenna direction and operating without a UAT according to a beacon signal from the communications satellite  103  and the control signal from the portable station  101 . 
     In  FIG.  1   , after the antenna direction adjustment is completed, the portable station  101  transmits a UAT signal and a control signal (CSCO signal) as the master station to the communications satellite  103 . The communications satellite  103  transmits the signals received from the portable station  101  back to ground after performing frequency conversion, thereby enabling the portable station  101  to receive the UAT signal and the control signal transmitted by the portable station  101  itself back from the communications satellite  103 , and perform adjustment and checking similar to an ordinary UAT. Note that the uplink from ground to satellite (the 14 GHz band, for example) and the downlink from satellite to ground (the 12 GHz band, for example) have a plurality of channels according to the satellite transponder of the communications satellite  103 , and each portable station uses a channel assigned by the satellite telecommunications carrier in advance to transmit a UAT signal and a control signal suited to the satellite telecommunications carrier. For example, properties such as the polarization (such as V-polarized transmission), the frequency (such as f1 GHz), and the level (such as β dBm) are determined as the information of the UAT signal suited to the satellite telecommunications carrier in advance. Similarly, properties such as the polarization (such as the V-polarized transmission), the center frequency (such as f2 GHz), the bandwidth (such as xx kHz), the level (such as α dBm), and the radio wave type (such as xx K0G1D) are determined as the information of the control signal suited to the satellite telecommunications carrier in advance. 
       FIG.  4    illustrates an example of a K u -band uplink channel. In  FIG.  4   , the vertical axis represents level (dBm), the horizontal axis represents frequency (GHz), and the graph illustrates a representation of a UAT signal having a frequency of f1 GHz and a level of β dBm, and a representation of a control signal having a center frequency of f2 GHz, a bandwidth (BW) of xx kHz, and a level of α dBm. Note that although  FIG.  4    illustrates representations of a UAT signal and a control signal, a predetermined bandwidth is also allocated similarly to a communication signal (user data communication such as telephony). Also, in  FIG.  1   , the uplink radio waves transmitted from the portable station  101  to the communications satellite  103  are V-polarized waves at 14 GHz for example, while the downlink radio waves transmitted back to the portable station  101  from the communications satellite  103  are H-polarized waves at 12 GHz, for example. Here, the signals transmitted or received between the ground and the satellite are for different users for each polarization even if the frequency is the same, and therefore correct polarization adjustment is important. 
     First Embodiment 
       FIG.  5    is a diagram illustrating a configuration example of a portable station  101  (master station) according to the first embodiment. The portable station  101  includes an antenna (ANT)  200 , a polarization duplexer (OMT (V/H))  201 , a transmit/receive demultiplexer (TX/RX)  202 , a transmitter (BUC)  203 , a low-noise amplifier (LNB-V)  204 , a low-noise amplifier (LNB-H)  205 , a divider (DIV)  206 , a modulator-demodulator (MODEM)  207 , an antenna driving unit  208 , and an automatic acquisition control unit  209 .  FIG.  5    illustrates an example in which the V polarization is the forward polarization in the transmit system and the H polarization is the forward polarization in the receive system. Note that forward polarization is the polarization in the direction of travel of the radio wave, and in the first embodiment, radio waves transmitted from the portable station  101  to the communications satellite  103  have the V polarization in the forward direction, and radio waves transmitted from the communications satellite  103  to the portable station  101  have the H polarization in the forward direction. Here, the V polarization corresponds to a first polarization and the H polarization orthogonal to the V polarization corresponds to a second polarization. 
     The ANT  200  is an antenna such as a parabolic antenna that includes an antenna driving mechanism for adjusting the direction under control by the antenna driving unit  208 , and transmits and receives wireless radio waves with respect to the communications satellite  103 . Note that ANT is an abbreviation of ANTenna. 
     The OMT (V/H)  201  is a polarization duplexer that splits radio waves into a V-polarized signal and an H-polarized signal, and functions bidirectionally for transmission and reception. For example, a signal received by the ANT  200  is outputted to the TX/RX  202  and the LNB-H  205 , while a signal transmitted from the TX/RX  202  is outputted to the TX/RX  202 . Note that OMT is an abbreviation of Ortho Mode Transducer. 
     The TX/RX  202  is a transmit/receive demultiplexer that splits a signal into a transmit signal and a receive signal. 
     The BUC  203  is a transmitter combining a high power amplification function with a function of frequency-converting a signal in the 1.2 GHz band outputted by the MODEM  207  to the 14 GHz band, for example. Note that BUC is an abbreviation of Block Up Converter. 
     The LNB-V  204  is a low-noise amplifier combining a function of amplifying with low noise a V-polarized signal in the 12 GHz band received by the ANT  200  with a function of converting the frequency to the 1.2 GHz band, for example. Note that LNB is an abbreviation of Low Noise Block converter. 
     The LNB-H  205  is a low-noise amplifier combining a function of amplifying with low noise an H-polarized signal in the 12 GHz band received by the ANT  200  with a function of converting the frequency to the 1.2 GHz band, for example. Here, the blocks from the ANT  200  to the LNB-V  204  and the LNB-H  205  correspond to a reception unit. 
     The DIV  206  is a divider that divides and outputs an inputted signal into two signals. Note that DIV is an abbreviation of DIVider. 
     The MODEM  207  is a modulator-demodulator that converts and transmits data signals at a communication rate of 384 kbit/s and also receives and demodulates a modulated signal into a data signal at a communication rate of 1.5 Mbit/s, for example. Note that MODEM is an abbreviation of MOdulator-DEModulator. Here, the blocks from the MODEM  207  and the BUC  203  to the ANT  200  correspond to a transmission unit. 
     The antenna driving unit  208  causes the antenna driving mechanism of the ANT  200  to operate on the basis of commands from the automatic acquisition control unit  209 , and thereby adjusts the three directions of the azimuth, the elevation, and the polarization angle. Note that the azimuth is an angle centered on the antenna and turning to the east from true north (corresponding to longitude), the elevation is an angle going upward from the horizontal plane, and the polarization angle is an angle obtained between the horizontal plane and the polarization plane of arriving radio waves. 
     The automatic acquisition control unit  209  has a computer function that executes a program stored in advance with a control unit  301 , and executes processes such as automatic acquisition of the communications satellite  103  and adjustment and checking during operations. For example, the automatic acquisition control unit  209  controls the transmit level of the BUC  203 , controls the modulation-demodulation processing by the MODEM  207 , controls the antenna driving unit  208 , and the like in the portable station  101 . 
     In  FIG.  5   , the automatic acquisition control unit  209  includes the control unit  301 , a direction sensor  302 , a position sensor  303 , a MON-H  304 , a MON-V  305 , and a satellite DB  306 . 
     The control unit  301  operates on the basis of a program stored internally in advance, and cooperates with the units of the direction sensor  302 , the position sensor  303 , the MON-H  304 , the MON-V  305 , and the satellite DB  306  to adjust the antenna direction with the antenna driving unit  208  and perform a UAT. In addition, the control unit  301  adjusts the transmit level of the BUC  203 , controls the MODEM  207  (such as transmitting a continuous wave (CW) and specifying the modulation-demodulation scheme), and the like. 
     The direction sensor  302  is a sensor that measures the azimuth (east longitude) of the ANT  200 . For example, the direction sensor  302  measures the current azimuth of the ANT  200  obtained from the antenna driving unit  208  on the basis of information obtained from an azimuth compass or the like. Here, the azimuth corresponds to longitude. 
     The position sensor  303  is a sensor that measures the installation location (latitude and longitude) of the portable station  101 . A system such as the Global Positioning System (GPS) is used, for example. 
     The MON-H  304  includes a measuring instrument (such as a spectrum analyzer, for example) capable of measuring the receive level, the frequency, and the bandwidth, and measures the receive level, the frequency, and the bandwidth of an H-polarized signal outputted from the DIV  206 . 
     Like the MON-H  304 , the MON-V  305  includes a measuring instrument (such as a spectrum analyzer, for example) capable of measuring the receive level, the frequency, and the bandwidth, and measures the receive level, the frequency, and the bandwidth of a V-polarized signal outputted from the LNB-V  204 . 
     The satellite DB  306  is a database including a storage medium such as a hard disk or a memory. For example, information such as position information (such as the east longitude) and beacon signal information (such as the polarization and frequency) of each satellite is stored as satellite information for a plurality of communications satellites including the communications satellite  103 . The satellite DB  306  also stores information about a UAT signal (such as the polarization, frequency, and level) suited to the satellite telecommunications carrier in advance and information about a control signal (such as the polarization, center frequency, bandwidth, level, and radio wave type) suited to the satellite telecommunications carrier in advance. 
     Here, because the core of the satellite communication system  100  according to the first embodiment is the technology related to the UAT performed after the adjustment of the antenna direction is completed, a detailed description of the method for adjusting the antenna direction is omitted. The control unit  301  of the automatic acquisition control unit  209  controls the three directions of the azimuth, the elevation, and the polarization angle of the ANT  200  with the antenna driving unit  208  while also measuring the installation location (latitude and longitude) of the ANT  200  acquired from the position sensor  303  and the direction (east longitude) of the ANT  200  acquired from the direction sensor  302 , and makes adjustments such that the ANT  200  points in the direction of a target communications satellite (communications satellite  103 ) stored in the satellite DB  306 . 
     In this way, the portable station  101  according to the first embodiment can adjust the antenna direction and perform a UAT as the master station on the basis of a program stored in advance in the control unit  301  of the automatic acquisition control unit  209 . 
       FIG.  6    illustrates a configuration of the portable station  102  (slave station). The portable station  102  acting as a slave station includes an antenna (ANT)  400 , a polarization duplexer (OMT (V/H))  401 , a transmitter (BUC)  402 , a low-noise amplifier (LNB-H)  403 , a modulator-demodulator (MODEM)  404 , an antenna driving unit  405 , and an automatic acquisition control unit  406 .  FIG.  6    illustrates an example in which transmit system has the V polarization in the forward direction and the receive system has the H polarization in the forward direction. 
     Note that the portable station  102  has a configuration similar to the ordinary portable station  801 , and communicates a control signal with the base station  802  to establish synchronization and thereby transmit and receive a communication signal. In the case where the base station  802  is nonfunctional, such as during a large-scale disaster, the portable station  102  can communicate a control signal with another portable station (in the first embodiment, the portable station  101 ) that operates as the master station instead of the base station  802  to establish synchronization and thereby transmit and receive a communication signal. Here, the portable station  102  acting as a slave station performs a remote UAT with the master station (portable station  101 ) when the portable station  102  is introduced, and if an acknowledgment is obtained from the satellite telecommunications carrier, the portable station  102  is exempted from performing the UAT for subsequent operations by automatically adjusting the antenna and then synchronizing with the control signal (CSCO signal) from the master station. 
     In  FIG.  6   , the ANT  400 , the OMT (V/H)  401 , the BUC  402 , the LNB-H  403 , the MODEM  404 , and the antenna driving unit  405  have functions similar to the ANT  200 , the OMT (V/H)  201 , the BUC  203 , the LNB-H  205 , the MODEM  207 , and the antenna driving unit  208  described in  FIG.  5   . The automatic acquisition control unit  406  includes a control unit  501 , a direction sensor  502 , and a position sensor  503 . Note that the direction sensor  502  and the position sensor  503  have functions similar to the direction sensor  302  and the position sensor  303  of the automatic acquisition control unit  209  described in  FIG.  5   . 
     The control unit  501  calculates the three directions of the azimuth, the elevation, and the polarization angle of the ANT  400  to be adjusted on the basis of the installation location (latitude and longitude) of the ANT  400  acquired from the position sensor  503  and the current direction (longitude) of the ANT  400  acquired from the direction sensor  502 , and adjusts the ANT  400  with the antenna driving unit  405  such that the direction of the ANT  400  points in the direction of the target communications satellite  103  stored in advance. Thereafter, the control unit  501  receives a control signal (CSCO signal) from the portable station  101  acting as the master station through the MODEM  404 , and establishes synchronization. 
     In this way, the portable station  102  acting as a slave station can adjust the antenna direction and establish synchronization with the portable station  101  acting as the master station, and communicate with the portable station  101  or another portable station. 
     Next, an example of a UAT process performed after the completion of the antenna direction adjustment in the portable station  101  according to the first embodiment will be described. 
     [Example of UAT Process According to First Embodiment] 
       FIG.  7    illustrates an example of a UAT signal checking and adjustment process according to the first embodiment. Note that the process in  FIG.  7    is performed between the portable station  101  and the communications satellite  103  illustrated in  FIG.  1   , and is executed by a program stored in advance in the control unit  301  of the automatic acquisition control unit  209  in the portable station  101  illustrated in  FIG.  5   . 
     In step S 101 , the operator of the portable station  101  completes adjustment of the antenna direction. Here, because the core of the satellite communication system  100  according to the first embodiment is the technology related to the UAT performed after the adjustment of the antenna direction is completed, a detailed description of the method for adjusting the antenna direction is omitted. For example, the control unit  301  of the automatic acquisition control unit  209  calculates the three directions of the azimuth, the elevation, and the polarization angle of the ANT  200  to be installed on the basis of the installation location (latitude and longitude) of the ANT  200  acquired from the position sensor  303  and the current azimuth of the ANT  200  acquired from the direction sensor  302 , and adjusts the ANT  200  with the antenna driving unit  208  to point in the direction (longitude) of the target communications satellite  103  stored in the satellite DB  306 . 
     In step S 102 , the control unit  301  of the portable station  101  starts a UAT. 
     In step S 103 , the control unit  301  references the satellite DB  306 , outputs a CW on a predetermined UAT signal frequency from the MODEM  207 , and transmits a V-polarized UAT signal to the communications satellite  103  at a predetermined level lower than a prescribed level from the BUC  203  (transmit process). Here, the communications satellite  103  converts the frequency of the UAT signal transmitted from the portable station  101 , and transmits the converted UAT signal back to ground. Note that when sending back the UAT signal, the polarization is converted from V polarization to H polarization. 
     In step S 104 , the control unit  301  uses the MON-H  304  to receive the UAT signal having the H polarization in the forward direction received back from the communications satellite  103  (receive process), and determines whether or not the frequency of the UAT signal is a prescribed frequency determined in advance. In the case where the reception of the UAT signal at the prescribed frequency is confirmed, the flow proceeds to the process in step S 105 , whereas in the case where the reception is not confirmed, the flow returns to step S 103 , and a similar process is repeated until the UAT signal is confirmed successfully. Note that if the UAT signal is not confirmed successfully within a certain time, an error notification may be issued to the operator. 
     In step S 105 , the control unit  301  controls the BUC  203  to raise the UAT signal to a prescribed level and transmit the UAT signal to the communications satellite  103 . 
     In step S 106 , the portable station  101  measures the receive level Cd of the UAT signal having the H polarization in the forward direction of the UAT signal received back from the communications satellite  103 . 
     In step S 107 , the control unit  301  uses the MON-V  305  to receive and measure the level Cx of cross-talk into the V polarization in the opposing direction of the UAT signal received back from the communications satellite  103 . 
     In step S 108 , the control unit  301  calculates the cross-polarization discrimination XPD according to Expression (1). 
       XPD= Cd−Cx   (1)
 
     Additionally, the control unit  301  determines whether or not the cross-polarization discrimination XPD is at or above a predetermined threshold (for example, XPD≥25 dB). In the case where XPD≥25 dB, the flow proceeds to the process in step S 110 , whereas in the case where XPD&lt;25 dB, it is determined that the adjustment of the antenna direction is incomplete and the flow proceeds to the process in step S 109  (control process). 
     In step S 109 , because the adjustment of the antenna direction has been determined to be incomplete in step S 108 , the control unit  301  readjusts the antenna direction, returns to the process in step S 101 , and executes a similar process. 
     In step S 110 , the control unit  301  controls the MODEM  207  and the BUC  203  to stop the transmission of the UAT signal (end transmission). 
     In step S 111 , the control unit  301  uses the MON-H  304  to confirm that the transmission of the UAT signal received back from the communications satellite  103  has ended, and proceeds to the process in (A). 
     In this way, even in the case where a UAT with the satellite telecommunications carrier cannot be performed, the portable station  101  according to the first embodiment can receive a UAT signal transmitted by the portable station  101  itself and received back from the communications satellite  103  to adjust and check the transmit level and the polarization, similarly to an ordinary UAT. At this point, because the checking of the UAT signal is completed, the portable station  101  performs a process of checking the control signal next. 
       FIG.  8    illustrates an example of a control signal checking and adjustment process. Note that the process in  FIG.  8    is performed between the portable station  101  and the communications satellite  103 , and is executed by a program stored in advance in the control unit  301  of the automatic acquisition control unit  209  in the portable station  101  illustrated in  FIG.  5   . 
     In step S 112 , the control unit  301  references the satellite DB  306 , outputs a control signal (CSCO signal) submitted to the satellite telecommunications carrier in advance from the MODEM  207 , and transmits the control signal as a V-polarized signal to the communications satellite  103  at a predetermined level lower than the operating level (here, a level 10 dB lower than the operating level) from the BUC  203  (transmit process). Here, the communications satellite  103  converts the frequency of the control signal transmitted from the portable station  101 , and transmits the converted control signal back to ground. Note that when sending back the control signal, the polarization is converted from V polarization to H polarization. 
     In step S 113 , the control unit  301  uses the MON-H  304  to receive the control signal having the H polarization in the forward direction received back from the communications satellite  103  (receive process), and measures the frequency (center frequency) and the bandwidth of the control signal. 
     In step S 114 , the control unit  301  determines whether or not the frequency and the bandwidth of the control signal measured in step S 113  conform to the information (prescribed values) of the control signal submitted to the satellite telecommunications carrier. If the control signal is in conformance, the flow proceeds to the process in step S 115 , and if not, the flow proceeds to the process in step S 122  (control process). 
     In step S 115 , the control unit  301  measures the level of cross-talk into the V polarization in the opposing direction of the H polarization in the forward direction included in the signal sent back from the communications satellite  103  and received by the MON-H  304 . At this point, a control signal having the V polarization is not measured if the polarization of the control signal has been adjusted correctly, but a control signal having the V polarization is measured if the polarization has not been adjusted correctly. 
     In step S 116 , the control unit  301  determines the presence or absence of a control signal having the V polarization in the opposing direction measured in step S 115 . If a control signal having the V polarization does not exist, the flow proceeds to the process in step S 117 , whereas if a control signal having the V polarization exists, the flow proceeds to the process in step S 122 . Note that a control signal having the V polarization may be determined not to exist in the case where the measured level of the control signal having the V polarization is below a preset threshold. 
     In step S 117 , the control unit  301  determines whether or not the transmit level of the transmitted control signal is less than the operating level. In the case where transmit level&lt;operating level, the flow proceeds to the process in step S 118 , whereas in the case where transmit level≥operating level, the flow proceeds to the process in step S 119  (control process). 
     In step S 118 , the control unit  301  controls the BUC  203  to raise the transmit level of the control signal 2 dB and transmit the control signal to the communications satellite  103 , then returns to the process in step S 113 . 
     In step S 119 , the control unit  301  uses the MON-H  304  to receive the control signal having the H polarization in the forward direction received back from the communications satellite  103 , and measures the frequency (center frequency) and the bandwidth of the control signal at the operating level. 
     In step S 120 , the control unit  301  determines whether or not the frequency and the bandwidth of the control signal at the operating level measured in step S 119  conform to the information (prescribed values) of the control signal submitted to the satellite telecommunications carrier. If the control signal is in conformance, the flow proceeds to the process in step S 121 , and if not, the flow proceeds to the process in step S 122  (control process). 
     In step S 121 , the control unit  301  completes the UAT started in step S 102  of  FIG.  7   , saves the measurement values of the UAT signal measured in steps S 106 , S 107 , and S 108  and the measurement values of the control signal measured in step S 119  to the satellite DB  306  as UAT evidence, and starts operations (control process). 
     In step S 122 , in the case where NO is determined in step S 114 , S 116 , or S 120 , the control unit  301 , the control unit  301  controls the MODEM  207  and the BUC  203  to stop the transmission of the control signal (end transmission). 
     In step S 123 , the control unit  301  uses the MON-H  304  to confirm that the transmission of the control signal received back from the communications satellite  103  has ended, and returns to the process in (B) of  FIG.  7    to perform the UAT again. 
     In this way, even in the case where a UAT with the satellite telecommunications carrier cannot be performed, the portable station  101  according to the first embodiment can receive a UAT signal and a control signal transmitted by the portable station  101  itself and received back from the communications satellite  103  to adjust and check the transmit level and the polarization of the UAT signal as described in  FIG.  7    and also adjust and check the frequency, the polarization, and the bandwidth of the control signal as described in  FIG.  8   , similarly to an ordinary UAT. In particular, because the portable station  101  according to the first embodiment raises the transmit level of the control signal gradually by 2 dB at a time while checking whether or not the control signal conforms to the control signal information submitted to the satellite telecommunications carrier, operations can be started without affecting other satellite communication users. Also, in the first embodiment, both the V polarization and the H polarization are measured through the signals sent back from the communications satellite  103 , and it can be confirmed that the polarization in the opposing direction (opposite polarization) is not being affected. 
     Here, a program corresponding to the processes described in  FIGS.  7  and  8    may also be executed by a computer. In addition, the program may be provided by being recorded onto a storage medium or may be provided over a network. 
     Second Embodiment 
       FIG.  9    is a diagram illustrating a configuration example of a portable station  101 - 1  (master station) according to the second embodiment. In  FIG.  9   , the blocks (ANT  200 , BUC  203 , DIV  206 , MODEM  207 , and antenna driving unit  208 ) having the same signs as the portable station  101  according to the first embodiment described in  FIG.  5    operate similarly to  FIG.  5   , and consequently a duplicate description is omitted. In addition to the blocks described above, the portable station  101 - 1  according to the second embodiment includes a low-noise amplifier (LNB)  205 - 1  that has a different name but the same operation as the first embodiment, an automatic acquisition control unit  209 - 1  that has the same name but slightly different operation from the first embodiment, and a power feed splitter  210  and a waveguide switch (WG-SW)  211  as new blocks. 
     The LNB  205 - 1  is a low-noise amplifier have a function similar to the LNB-V  204  and the LNB-H  205  in  FIG.  5   . The LNB  205 - 1  amplifies with low noise a V-polarized or H-polarized signal received by the ANT  200  and inputted through the power feed splitter  210  and the WG-SW  211 . Furthermore, the LNB  205 - 1  is a low-noise amplifier including an integrated function of frequency-converting a signal in the 12 GHz band to a signal in the 1.2 GHz band, for example. Here, the blocks from the ANT  200  to the LNB  205 - 1  correspond to a reception unit. 
     Like the automatic acquisition control unit  209  described in  FIG.  5   , the automatic acquisition control unit  209 - 1  has a computer function that executes a program stored in advance with a control unit  301 - 1 , and executes processes such as automatic acquisition of the communications satellite  103  and adjustment and checking during operations. For example, the automatic acquisition control unit  209 - 1  controls the transmit level of the BUC  203 , controls the modulation-demodulation processing by the MODEM  207 , controls the antenna driving unit  208 , controls the WG-SW  211 , and the like in the portable station  101 - 1 . Note that details about the automatic acquisition control unit  209 - 1  will be described later. 
     The power feed splitter  210  is a power feeding demultiplexer that splits a receive signal inputted from the ANT  200  into an H-polarized signal and a V-polarized signal, and outputs the split signals to the WG-SW  211 . Conversely, the power feed splitter  210  combines an inputted H-polarized transmit signal and an inputted V-polarized transmit signal, and outputs the combined signal to the ANT  200 . Note that in the example of  FIG.  9   , there is no H-polarized transmit signal, and therefore the power feed splitter  210  outputs only the V-polarized transmit signal outputted from the BUC  203  to the ANT  200 . 
     The WG-SW  211  is a waveguide switch that switches a physical connection in a waveguide under control by the automatic acquisition control unit  209 - 1 . In the example of  FIG.  9   , an H-polarized receive signal and a V-polarized receive signal outputted from the power feed splitter  210  are inputted into the WG-SW  211 . The WG-SW  211  outputs the H-polarized receive signal or the V-polarized receive signal to the LNB  205 - 1  under control by the automatic acquisition control unit  209 - 1 . Note that  FIG.  9    illustrates the state in which the H-polarized output signal from the power feed splitter  210  has been selected by the WG-SW  211 . 
     In  FIG.  9   , the automatic acquisition control unit  209 - 1  includes the control unit  301 - 1 , a direction sensor  302 , a position sensor  303 , a MON  304 - 1 , and a satellite DB  306 . In  FIG.  9   , the blocks (direction sensor  302 , position sensor  303 , and satellite DB  306 ) having the same signs as the automatic acquisition control unit  209  according to the first embodiment described in  FIG.  5    operate similarly to  FIG.  5   , and consequently a duplicate description is omitted. Here, the MON  304 - 1  and the control unit  301 - 1  will be described. 
     The automatic acquisition control unit  209  according to the first embodiment in  FIG.  5    includes the MON-H  304  that measures the receive level, the frequency, and the bandwidth of an H-polarized signal, and the MON-V  305  that measures the receive level, the frequency, and the bandwidth of a V-polarized signal. In contrast, in the automatic acquisition control unit  209 - 1  according to the second embodiment in  FIG.  9   , the single MON  304 - 1  measures the receive level, the frequency, and the bandwidth of an H-polarized or V-polarized signal selected by the WG-SW  211 . In this way, because the portable station  101  according to the first embodiment needs to be provided with separate systems for the H polarization and the V polarization as the receiving system lines, there is a problem of increased device scale of the portable station  101 . In contrast, it is sufficient for the portable station  101 - 1  according to the second embodiment to be provided with the WG-SW  211  having a simple configuration using only a waveguide switch, and because there is just one measuring instrument for measuring the receive level, the frequency, and the bandwidth, the device scale of the portable station  101 - 1  can be reduced. 
     Like the control unit  301  in  FIG.  5   , the control unit  301 - 1  operates on the basis of a program stored internally in advance, and cooperates with the units of the direction sensor  302 , the position sensor  303 , the MON  304 - 1 , and the satellite DB  306  to adjust the antenna direction with the antenna driving unit  208  and perform a UAT. In addition, the control unit  301 - 1  adjusts the transmit level of the BUC  203 , controls the MODEM  207 , switches the polarization of the WG-SW  211 , and the like. 
     Note that the direction sensor  302 , the position sensor  303 , and the satellite DB  306  are the same as  FIG.  5   . 
     In this way, by switching between the V polarization and the H polarization with the WG-SW  211 , the portable station  101 - 1  according to the second embodiment may be provided with only a single receiving system line, and the single MON  304 - 1  can be shared in common as a measuring instrument that measures the receive level, the frequency, and the bandwidth for each of H-polarized and V-polarized signals. With this arrangement, the device scale of the portable station  101 - 1  according to the second embodiment can be reduced compared to the portable station  101  according to the first embodiment. 
     Next, an example of a UAT process performed after the completion of the antenna direction adjustment in the portable station  101 - 1  according to the second embodiment will be described. 
     [Example of UAT Process According to Second Embodiment] 
       FIG.  10    illustrates an example of a UAT signal checking and adjustment process according to the second embodiment. Note that the process in  FIG.  10    corresponds to operations performed between the portable station  101 - 1  and the communications satellite  103  illustrated in  FIG.  1   , and is executed by a program stored in advance in the control unit  301 - 1  of the automatic acquisition control unit  209 - 1  in the portable station  101 - 1  illustrated in  FIG.  9   . 
     Here, in  FIG.  10   , steps having the same signs as the portable station  101  according to the first embodiment described in  FIG.  7    are the same as  FIG.  7   , and consequently a duplicate description is omitted. 
     In the second embodiment, the processes of steps S 106 - 1 , S 108 - 1 , and S 108 - 2  in  FIG.  10    are added. Note that before the process in  FIG.  10    is started, it is assumed that the control unit  301 - 1  of the automatic acquisition control unit  209 - 1  controls the WG-SW  211  to switch the receiving system line from the V polarization to the H polarization. Here, the receiving system line corresponds to the pathway from the LNB  205 - 1  to the MON  304 - 1  downstream from the WG-SW  211  described in  FIG.  9   . 
     The process from step S 101  to step S 106  is the same as the process by the portable station  101  according to the first embodiment in  FIG.  7   . In the second embodiment, the process in step S 106 - 1  is executed after the execution of the process in step S 106 . 
     In step S 106 - 1 , the control unit  301 - 1  controls the WG-SW  211  to switch the receiving system line from the H polarization to the V polarization. This arrangement makes it possible to measure the V-polarized signal on the receiving system line in the next step S 107 . 
     In step S 108 , the control unit  301  determines whether or not the calculated cross-polarization discrimination XPD is at or above a predetermined threshold (for example, XPD≥25 dB). In the case where XPD≥25 dB, the flow proceeds to the process in step S 108 - 1 , whereas in the case where XPD&lt;25 dB, it is determined that the adjustment of the antenna direction is incomplete and the flow proceeds to the process in step S 108 - 2  (control process). 
     In step S 108 - 1 , the control unit  301 - 1  controls the WG-SW  211  to switch the receiving system line from the V polarization to the H polarization. This arrangement makes it possible to measure the H-polarized signal on the receiving system line in the next step S 110 . 
     In step S 108 - 2 , the control unit  301 - 1  controls the WG-SW  211  to switch the receiving system line from the V polarization to the H polarization. With this arrangement, the receiving system line is switched to the H polarization of the initial state, and the process in the next step S 109  and thereafter can be performed. 
     In this way, like the first embodiment, even in the case where a UAT with the satellite telecommunications carrier cannot be performed, the portable station  101 - 1  according to the second embodiment can receive a UAT signal transmitted by the portable station  101 - 1  itself and received back from the communications satellite  103  to adjust and check the transmit level and the polarization, similarly to an ordinary UAT. Note that in the process of  FIG.  10   , because the checking of the UAT signal is completed, the portable station  101 - 1  performs a process of checking the control signal illustrated in  FIG.  11    next. 
       FIG.  11    illustrates an example of a control signal checking and adjustment process according to the second embodiment. Note that, like  FIG.  10   , the process in  FIG.  11    is executed by a program stored in advance in the control unit  301 - 1  of the automatic acquisition control unit  209 - 1  in the portable station  101 - 1  illustrated in  FIG.  9   . 
     Here, in  FIG.  11   , steps having the same signs as the portable station  101  according to the first embodiment described in  FIG.  8    are the same as  FIG.  8   , and consequently a duplicate description is omitted. 
     In the second embodiment, the processes of steps S 114 - 1 , S 116 - 1 , step S 117 - 1 , and S 107 - 2  in  FIG.  11    are added. 
     In  FIG.  11   , the process from step S 112  to step S 114  is the same as the process by the portable station  101  according to the first embodiment in  FIG.  8   . In the second embodiment, the process in step S 114 - 1  is executed in the case of YES in the process in step S 114 . 
     In step S 114 - 1 , the control unit  301 - 1  controls the WG-SW  211  to switch the receiving system line from the H polarization to the V polarization. This arrangement makes it possible to measure the V-polarized signal on the receiving system line in the next step S 115 . 
     Also, the process in step S 116 - 1  is executed in the case of NO in the process in step S 116  of  FIG.  11   . 
     In step S 116 - 1 , the control unit  301 - 1  controls the WG-SW  211  to switch the receiving system line from the V polarization to the H polarization. With this arrangement, the receiving system line is switched to the H polarization of the initial state, and the process in the next step S 122  and thereafter can be performed. 
     Furthermore, in the case of YES in step S 117  in  FIG.  11   , the process in step S 117 - 1  is executed, and in the case of NO, the process in step S 117 - 2  is executed. 
     In step S 117 - 1 , the control unit  301 - 1  controls the WG-SW  211  to switch the receiving system line from the V polarization to the H polarization. This arrangement makes it possible to measure the H-polarized signal on the receiving system line in the next step S 118 . 
     In step S 117 - 2 , the control unit  301 - 1  controls the WG-SW  211  to switch the receiving system line from the V polarization to the H polarization. This arrangement makes it possible to measure the H-polarized signal on the receiving system line in the next step S 119 . 
     Thereafter, the process from step S 118  to step S 123  is executed similarly to the first embodiment described in  FIG.  8   . 
     In this way, even in the case where a UAT with the satellite telecommunications carrier cannot be performed, the portable station  101 - 1  according to the second embodiment can receive a UAT signal and a control signal transmitted by the portable station  101 - 1  itself and received back from the communications satellite  103  to adjust and check the transmit level and the polarization of the UAT signal as described in  FIG.  10    and also adjust and check the frequency, the polarization, and the bandwidth of the control signal as described in  FIG.  11   , similarly to an ordinary UAT. Additionally, like the first embodiment, because the portable station  101 - 1  according to the second embodiment raises the transmit level of the control signal gradually by 2 dB at a time while checking whether or not the control signal conforms to the control signal information submitted to the satellite telecommunications carrier, operations can be started without affecting other satellite communication users. 
     Particularly, in the second embodiment, a simpler circuit configuration than the first embodiment can be used to measure both the V polarization and the H polarization through the signals sent back from the communications satellite  103  and confirm that the polarization in the opposing direction (opposite polarization) is not being affected. Specifically, by switching between the V polarization and the H polarization with the WG-SW  211 , the portable station  101 - 1  according to the second embodiment may be provided with only a single receiving system line, and because the measuring instrument that measures the receive level, the frequency, and the bandwidth of the H-polarized and V-polarized signals is shared in common, it is sufficient to provide just the single MON  304 - 1 . With this arrangement, the device scale of the portable station  101 - 1  according to the second embodiment can be reduced compared to the portable station  101  according to the first embodiment. 
     Here, a program corresponding to the processes described in  FIGS.  10  and  11    may also be executed by a computer. In addition, the program may be provided by being recorded onto a storage medium or may be provided over a network. 
     As described in the embodiments above, the transmission radio wave checking method for a satellite communication system, portable station, and transmission radio wave checking program according to the present invention is capable of completing a UAT by receiving and checking a UAT signal transmitted by a portable station and received back from a satellite, even in cases where a UAT cannot be performed with the satellite telecommunications carrier. 
     REFERENCE SIGNS LIST 
     
         
         
           
               100  satellite communication system 
               101 ,  101 - 1  portable station (master station) 
               102  portable station (slave station) 
               103  communications satellite 
               200 ,  400  ANT 
               201 ,  401  OMT 
               202  TX/RX 
               203 ,  402  BUC 
               204  LNB-V 
               205 ,  403  LNB-H 
               205 - 1  LNB 
               206  DIV 
               207 ,  404  MODEM 
               208 ,  405  antenna driving unit 
               209 ,  209 - 1 ,  406  automatic acquisition control unit 
               210  power feed splitter 
               211  WG-SW 
               301 ,  301 - 1 ,  501  control unit 
               302 ,  502  direction sensor 
               303 ,  503  position sensor 
               304  MON-H 
               304 - 1  MON 
               305  MON-V 
               306  satellite DB 
               800  satellite communication system 
               801  portable station 
               802  base station 
               803  communications satellite 
               804  satellite telecommunications carrier 
               805  control station