JP5251908B2 - Satellite communication device - Google Patents

Description

  The present invention relates to a satellite communication device that performs satellite communication with a partner station satellite communication device via a satellite station by a forward link transmitted to the partner station satellite communication device and a return link received from the partner station satellite communication device. is there.

  The transmission power of the satellite communication device in the satellite communication system is generally designed with a certain margin for the power value required by the desired line in consideration of changes in communication location and weather. In this case, when used in a good environment, this margin value becomes surplus power, so it cannot be said that it is efficient considering the use efficiency of the satellite repeater. Therefore, a method of performing efficient power management by calculating this surplus power and reflecting it in the transmission power value and the transmission line speed is used. As a conventional method, there is a method of transmitting a reception power margin value to a transmission side using a control line as described in JP-A-2003-278004. Japanese Patent Laid-Open No. 2002-335198 discloses a method of measuring the beacon level from a satellite and controlling the transmission power of the downlink of the satellite, and Japanese Patent Laid-Open No. 2005-268773 discloses a method in which a controlling station is a transmitting station. Describes a method of knowing the position of and transmitting the transmission power value to the transmitting station.

JP 2003-278004 A JP 2002-335198 A JP 2005-268773 A

  In the method described in Patent Document 1 or Patent Document 3, transmission power control information is exchanged between the local station satellite communication device and the partner station satellite communication device in addition to the audio / video and data to be originally transmitted. There is a problem that it is necessary to secure a separate line, which leads to an increase in extra overhead. In addition, the method described in Patent Document 2 requires a function of controlling the downlink in the satellite body, and there is a problem that the parts and cost are increased due to the functionalization of such a satellite. Furthermore, the existing satellite ( There is a possibility that the satellite communication apparatus needs to have a control interface with a satellite that does not perform downlink control, and a cost increase due to complicated functions becomes a problem.

  The present invention has been made to solve the above-described problems, and provides a satellite communication device capable of performing transmission power control without using a line for transmission power and line speed control. Objective.

According to a first aspect of the present invention, there is provided a satellite communication apparatus that communicates with a partner satellite communication apparatus via a satellite station by a forward link transmitted to the partner station satellite communication apparatus and a return link received from the partner station satellite communication apparatus. In the satellite communication device that performs the above, the counterpart satellite communication device is capable of transmission power control , demodulates the received signal received by the return link, and measures the power level, and the forward link Modulates the transmission signal to be transmitted in accordance with the above, and modulates the transmission power and calculates the power margin value from the power level measured by the demodulator and subtracts the specified power difference between the return link and the forward link to control the transmission power and calculates the value and a control unit for commanding to the modulation unit, the control unit again, regulations of the return link and the forward link And calculates the transmission power control value by subtracting the electric power difference, after a lapse of a predetermined time is a time to absorb the time difference between the embodiment of transmission power control in the other station satellite communication apparatus, those which direct to the modulation unit It is.

According to a second aspect of the present invention, there is provided a satellite communication device that communicates with a partner satellite communication device via a satellite station using a forward link transmitted to the partner satellite communication device and a return link received from the partner satellite communication device. In a satellite communication device that performs the above, a demodulation unit that demodulates a reception signal received by the return link and measures a power level, a modulation unit that modulates a transmission signal transmitted by the forward link, and varies transmission power, and Calculating a power margin value from the power level measured by the demodulator, calculating a transmission line speed control value based on a value obtained by subtracting a specified power difference between the return link and the forward link, and instructing the modulator to provided, the control unit is again sent line speed system based on the value obtained by subtracting the prescribed power difference between the return link and the forward link By calculating the value, after a predetermined time, it instructs to said modulation unit is for carrying out periodically transmitted line speed control.
3. The satellite communication apparatus according to claim 3, wherein the control unit calculates a power margin value from an average of the power level measured by the demodulation unit over the predetermined time. Is .

  According to the present invention, since the transmission power control of the forward link is performed based on the power level of the received signal received by the return link, a line for notifying the transmission power information with the partner station satellite communication device is unnecessary. It is possible to prevent the occurrence of overhead due to excess control data occupying the bandwidth of the satellite line.

It is a functional block diagram showing the structure of the satellite communication apparatus which concerns on Embodiment 1 of this invention. It is a schematic diagram of transmission power control by the satellite communication apparatus according to Embodiment 1 of the present invention. It is a schematic diagram explaining a regulation power difference with the transmission / reception beam of a satellite station. It is a process sequence diagram which shows the whole process of the satellite communication terminal which concerns on Embodiment 1 of this invention. It is a flowchart figure which shows the control processing flow in a transmission power control sequence. It is a flowchart figure of the transmission power control sequence start determination part in a transmission power control sequence. It is a flowchart figure of the transmission power control sequence implementation part in a transmission power control sequence. It is a flowchart figure of the transmission power change sequence implementation part. It is a flowchart figure of the transmission power control sequence continuation determination part in a transmission power control sequence. It is a functional block diagram showing the structure of the satellite communication apparatus which concerns on Embodiment 2 of this invention. It is a schematic diagram of transmission line speed control by the satellite communication apparatus according to Embodiment 2 of the present invention. It is a process sequence diagram which shows the whole process of the satellite communication terminal which concerns on Embodiment 2 of this invention. It is a flowchart figure which shows the control processing flow in a transmission line speed control sequence. It is a flowchart figure of the transmission line speed control sequence start determination part in a transmission line speed control sequence. It is a flowchart figure of the transmission line speed control sequence implementation part in a transmission line speed control sequence. It is a flowchart figure of the transmission line speed change sequence implementation part. It is a flowchart figure of the transmission line speed control sequence continuation determination part in a transmission line speed control sequence. It is a functional block diagram showing the structure of the satellite communication apparatus which concerns on Embodiment 3 of this invention.

  Embodiment 1

  A satellite communication apparatus according to Embodiment 1 of the present invention will be described with reference to FIGS. 1 is a functional block diagram showing a configuration of a satellite communication apparatus according to Embodiment 1 of the present invention. In FIG. 1, 1 is an antenna that transmits and receives radio waves to and from a satellite, 2 is a receiving unit, 3 is a demodulating unit that demodulates a received wave and outputs it to the terminal 4, and 5 is a modulating unit that modulates transmission data from the terminal 4. , 6 are transmission units, and 7 is a control unit that controls the demodulation unit 3 and the modulation unit 5. In the control unit 7, 8 is a reception C / N margin calculation unit that calculates a reception C / N margin based on the reception C / N data measured by the demodulation unit 3, and 9 is a transmission power control value based on the reception C / N margin. It is the transmission power calculating part which calculates.

  The operation of this satellite communication apparatus will be described. Received waves are received by the demodulator 3 via the receiver 2. The demodulator 3 exchanges control / status information with the controller 7, demodulates the received wave, and sends received data to the terminal 4. The demodulator 3 measures the received C / N data and outputs it to the received C / N margin calculator 8 of the controller 7. In the control unit 7, the reception C / N margin calculated by the reception C / N margin calculation unit 8 is input to the transmission power calculation unit 9, the transmission power calculation unit 9 calculates the transmission power control value, and the transmission power value is calculated. By setting the modulation unit 5, the power of the transmission wave is controlled. The modulation unit 5 receives control from the control unit 7, modulates transmission data input from the terminal 4, and transmits a transmission wave to the satellite line through the transmission unit 6.

  Next, the outline of transmission power control by the satellite communication apparatus will be described with reference to FIG. FIG. 2 is a schematic diagram of transmission power control by the satellite communication apparatus according to Embodiment 1 of the present invention. In FIG. 2, 10 is a satellite station, 11 is a local station satellite communication apparatus (hereinafter referred to as the local station 11), and 12 is a counterpart station satellite communication apparatus (hereinafter referred to as a counterpart station 12). The own station 11 and the partner station 12 communicate with each other via the satellite station 10, and the transmission line from the own station 11 to the partner station 12 is a forward link, and the transmission line from the partner station 12 to the host station 11 is a return link. It describes as. Transmission power control generally consists of the following procedures (1) to (4). (1) The own station 11 receives the transmission wave from the partner station 12 through the return link line. (2) The own station 11 calculates the margin value of the transmission power of the forward link of the own station from the reception margin of the return link. (3) The local station 11 reflects the calculated transmission power margin value in the transmission power of the local station. (4) The local station 11 emits radio waves with the reflected transmission power of the local station. In particular, it is one feature of the present invention that the specified power difference ΔP is taken into account in the calculation of the transmission power margin value in (2).

  The specified power difference ΔP will be described with reference to FIG. FIG. 3 is a schematic diagram illustrating the specified power difference ΔP using the transmission / reception beam of the satellite station 12. FIG. 3A shows the beam coverage of the transmission antenna 13 mounted on the satellite station 10, and the gain Qt of the transmission antenna 13 is expressed as a function Qt (θ, φ) of the elevation angle θ and the azimuth angle φ fixed to the transmission antenna 13. I can express. FIG. 3B shows the beam coverage of the receiving antenna 14 mounted on the satellite station 10, and the gain Qr of the receiving antenna 14 is a function Qr (θ, φ) of the elevation angle θ and the azimuth φ fixed to the receiving antenna 14. ). For convenience, it is assumed that the elevation angle θ and the azimuth angle φ, which are coordinate systems fixed to the transmission antenna 13 and the reception antenna 14, are the same. In this coordinate system, it is assumed that the own station 11 is located at (θ1, φ1) and the counterpart station 12 is located at (θ2, φ2). At this time, the gain contribution Q1 of the antenna mounted on the satellite station 10 in the power of the received signal received by the own station 11 through the return link of FIG. 2 is Q1 = Qr (θ1, φ1) + Qt (θ2, φ2). On the other hand, the gain contribution Q2 of the antenna mounted on the satellite station 10 in the power of the received signal received by the counterpart station 12 via the forward link in FIG. 2 is Q2 = Qr (θ2, φ2) + Qt (θ1, φ1).

  Then, it can be seen that a power difference of at least Q1-Q2 can occur between the reception level of the local station 11 on the return link and the reception level of the counterpart station 12 on the forward link. Here, the functions Qt (θ, φ) and Qr (θ, φ) are known from the theoretical solution in antenna design or the performance test data after the antenna is manufactured. By examining [theta] 1, [phi] 1) and ([theta] 2, [phi] 2) by changing them to all arbitrary positions, the maximum value of the power difference (Q1-Q2) can be obtained. One method for predetermining the prescribed power difference ΔP is to set the maximum value of the power difference (Q1−Q2) to ΔP.

Another method for predetermining the specified power difference ΔP is to set the upper 3σ value of the power difference (Q1−Q2) to ΔP. Further, a margin amount is added to the maximum value or the upper 3σ value to obtain a specified power difference ΔP, and other elements of the return link and the forward link (for example, frequency characteristics of the amplifier in the satellite station 12) are added. Various methods for determining the prescribed power difference ΔP can be considered. The setting of the specified power difference ΔP described above is an example, and it can be said that the specified power difference ΔP is set based on the gain difference of the relay by the satellite station 10.

  Next, the transmission power control procedure will be described in detail with reference to FIGS. FIG. 4 is a processing sequence diagram showing the entire processing of the satellite communication terminal according to Embodiment 1 of the present invention. The processing sequence shown in FIG. 4 is defined as a transmission power control sequence, and the processes according to the steps (1) to (7) shown in FIG. 4 are performed. (1) is a stage for determining the start of transmission power control. The start condition of this processing sequence is conditional on the radio emission of the own station 11 and the reception synchronization in the demodulator 3 of the own station 11. (2) is a step of measuring the received C / N, and after the start of the transmission power control sequence, a matching timer is provided for t1 time in order to absorb the time difference from the start of the transmission power control sequence of the counterpart station 12, and then t2 time. The reception C / N averaging process is performed through (3) is a step of performing transmission power control, and calculates a margin of reception C / N from reception C / N measured over time t2 and known required power, and controls transmission power of the own station 11. carry out.

  (4) is a step of measuring the received C / N again. After the transmission power control is performed, a matching timer t3 time is provided to absorb the time difference from the transmission power control of the partner station 12, and then the reception C / N is received over t4 time. / N averaging process is performed. (5) is a step of performing transmission power control after step (4). The reception C / N margin is calculated from the reception C / N measured over time t4 and the known required power, and the own station 11 The transmission power is controlled. (6) is a further repetition stage, and transmission power control is performed periodically by repeating steps (4) and (5). (7) is a stage for determining termination, and the termination of the transmission power control sequence is performed on the condition that reception asynchronism is confirmed upon reception of either one of the own station 11 or the partner station 12. At this time, if reception demodulation is in an asynchronous state, the wave is automatically stopped.

  FIG. 5 is a flowchart showing a control processing flow in the transmission power control sequence. After the operation is started, the transmission power control sequence start determination in step S1 is performed, and the process proceeds to the execution of the transmission power control sequence in step S2. Further, the transmission power control sequence execution in step S2 and the transmission power control sequence continuation determination in step S3 are processed in parallel. The control processing flowcharts shown in FIGS. 5 to 9 are executed in each satellite communication apparatus.

  FIG. 6 is a flowchart of the transmission power control sequence start determination part in step S1 in the transmission power control sequence shown in FIG. In step S11, the control unit 7 sets a nominal value as a known required power as an initialization process to the demodulation unit 3 and the modulation unit 5, and emits radio waves from the own station 11 (step S12) and the demodulation unit 3 of the own station 11. The reception synchronization (step S13) is determined as the start determination of the transmission power control sequence execution (step S2).

  FIG. 7 is a flowchart of the transmission power control sequence implementation part of step S2 in the transmission power control sequence shown in FIG. The control unit 7 provides a time t1 (step S21) after the matching timer that absorbs the timing difference until the start of the transmission power control sequence with the counterpart station 12, and is then input from the demodulation unit 3 for t2 hours. The received C / N margin calculation unit 8 performs an averaging process on the received C / N data (step S22). After the time t2, the reception C / N margin calculation unit 8 calculates the reception C / N margin from the measured reception C / N average value and the known required power, and changes the transmission power of the own station 11 (step) S23). After the change of the transmission power, a matching timer t3 time is provided to absorb again the timing error of the transmission power control with the counterpart station 12 (step S24), and then the reception C / N margin for t4 time. The calculation unit 8 performs reception C / N averaging processing (step S25). By repeating the steps S23, S24, and S25, transmission power control is performed periodically.

  FIG. 8 is a flowchart of the transmission power change sequence execution part of step S23 shown in FIG. In the flowchart described with reference to FIG. 8, the above-described specified power difference ΔP is used, and this ΔP is used as a level difference that is not controlled. First, in step S231, when the absolute value of the reception C / N margin ΔC / N is smaller than or equal to ΔP, the transmission power calculation unit 9 proceeds to step S232 and does not control the transmission power of the modulation unit 5. In step S231, when the absolute value of the reception C / N margin ΔC / N is larger than ΔP, the transmission power calculation unit 9 proceeds to step S233 and branches the process according to the sign of the reception C / N margin. The transmission power calculation unit 9 reflects the value obtained by subtracting ΔP from the reception C / N margin in the modulation unit 5 (steps S234 and S235). Since the reception margin from the known required power received on the return link is reflected as the margin of the forward link in which the local station 11 emits radio waves, if the transmission power is changed beyond the specified power difference ΔP, the margin of the forward link or more May be changed. Therefore, ΔP is set as a level difference that is not controlled.

  FIG. 9 is a flowchart of the transmission power control sequence continuation determination portion in step S3 in the transmission power control sequence shown in FIG. The continuation of the transmission power control sequence is determined based on the reception synchronization (step S31) of the demodulator 3 in the own station 11 when the transmission power control sequence is performed. Next, the modulation unit 5 is stopped (step S32), and then the process proceeds to transmission power control sequence start determination (step S1).

  As described above, by the satellite communication apparatus according to Embodiment 1 of the present invention, the local station 11 considers the specified power difference ΔP as the power difference that does not control the reception C / N margin of the return link, and transmits the transmission power of the forward link. Since control is performed, it is possible to prevent a reception error of the counterpart station 12 due to excessive control of transmission power. In addition, this method eliminates the need for a control line for notifying the margin value of transmission power between the own station 11 and the partner station 12, thereby generating overhead due to extra control data that occupies the bandwidth of the satellite line. Can be prevented.

  Embodiment 2

  A satellite communication apparatus according to Embodiment 2 of the present invention will be described with reference to FIGS. FIG. 10 is a functional block diagram showing the configuration of the satellite communication apparatus according to Embodiment 2 of the present invention. In FIG. 10, reference numeral 15 denotes a transmission line speed control value for controlling the transmission line speed of the transmission wave by calculating a transmission line speed control value based on the input reception C / N margin and setting this value in the modulator 5. Part. At this time, the modulation unit 5 receives the control from the control unit 7, modulates transmission data input from the terminal 4, and transmits a transmission wave to the satellite line through the transmission unit 6. In FIG. 10, the circuits and components denoted by the same reference numerals as those in FIG. 1 are the same or corresponding circuits and components as those circuits and components in FIG.

  Next, the outline of transmission power control by the satellite communication apparatus will be described with reference to FIG. FIG. 11 is a schematic diagram of transmission line speed control by the satellite communication apparatus according to Embodiment 2 of the present invention. Transmission line speed control generally consists of the following procedures (1) to (4). (1) The own station 11 receives the transmission wave from the partner station 12 through the return link line. (2) The own station 11 calculates the margin value of the transmission power of the forward link of the own station from the reception margin of the return link. (3) The own station 11 reflects the calculated transmission power margin value on the transmission line speed of the own station. (4) The own station 11 emits radio waves at the reflected transmission line speed of the own station. In particular, it is one feature of the present invention that the specified power difference ΔP is taken into account in the calculation of the transmission power margin value in (2). The specified power difference ΔP is as described with reference to FIG. 3 in the first embodiment, and thus the description thereof is omitted in the present embodiment.

  Next, the transmission line speed control procedure will be described in detail with reference to FIGS. FIG. 12 is a processing sequence diagram showing the entire processing of the satellite communication terminal according to Embodiment 2 of the present invention. The processing sequence shown in FIG. 12 is defined as a transmission line speed control sequence, and the processes according to the steps (1) to (7) shown in FIG. 12 are performed. (1) is a stage for determining the start of transmission line speed control. The start condition of this processing sequence is conditional on the radio emission of the own station 11 and the reception synchronization in the demodulator 3 of the own station 11. (2) is a step of measuring the reception C / N. After the transmission line speed control sequence is started, the reception C / N averaging process is performed over a time period T1. (3) is a stage for performing transmission line speed control. The reception C / N margin is calculated from the reception C / N measured over time T1 and the known required power, and the transmission line speed of the own station 11 is calculated. Implement control.

  (4) is a step of measuring the received C / N again, and the received C / N is averaged over time T2. (5) is a step of performing transmission line speed control after step (4), and calculates the reception C / N margin from the received C / N measured over T2 time and the known required power, 11 transmission line speed is controlled. (6) is a further iterative stage, and transmission line speed control is performed periodically by repeating stages (4) and (5). (7) is a stage for determining termination, and the termination of the transmission line speed control sequence is performed on the condition that reception asynchronism is confirmed upon reception of either one of the own station 11 or the partner station 12. At this time, if reception demodulation is in an asynchronous state, the wave is automatically stopped.

  FIG. 13 is a flowchart showing a control processing flow in the transmission line speed control sequence. After the operation is started, after the transmission line speed control sequence start determination in step S4, the process proceeds to the execution of the transmission line speed control sequence in step S5. In addition, the transmission line speed control sequence in step S5 and the transmission line speed control sequence continuation determination in step S6 are processed in parallel. Note that the control processing flowcharts shown in FIGS. 13 to 17 are executed in each satellite communication apparatus.

  FIG. 14 is a flowchart of the transmission line speed control sequence start determination part in step S4 in the transmission line speed control sequence shown in FIG. In step S41, the control unit 7 sets a nominal value as a known line speed as an initialization process to the demodulation unit 3 and the modulation unit 5, and emits radio waves from the own station 11 (step S42) and the demodulation unit 3 of the own station 11. The reception synchronization (step S43) is determined as the start determination of the transmission line speed control sequence (step S5).

  FIG. 15 is a flowchart of the transmission line speed control sequence implementation portion of step S5 in the transmission line speed control sequence shown in FIG. The control unit 7 performs an averaging process on the received C / N data input from the demodulating unit 3 by the received C / N margin calculating unit 8 for a time T1 (step S51). After time T1, the reception C / N margin calculation unit 8 calculates the reception C / N margin from the measured reception C / N average value and the known required power, and changes the transmission line speed of the own station 11 ( Step S52). After the change of the transmission line speed, the reception C / N margin calculation unit 8 performs the reception C / N averaging process again for T2 time (step S53). By repeating the steps S52 and S53, the transmission line speed control is performed periodically.

  FIG. 16 is a flowchart of the transmission line speed change sequence execution part of step S52 shown in FIG. In the flowchart described with reference to FIG. 16, the above-mentioned specified power difference ΔP is used, and this ΔP is used as an uncontrolled level difference. First, in step S521, when the absolute value of the reception C / N margin ΔC / N is smaller than or equal to ΔP, the transmission line speed calculation unit 15 proceeds to step S522 and controls the transmission line speed of the modulation unit 5. do not do. In step S521, when the absolute value of the reception C / N margin ΔC / N is larger than ΔP, the transmission line speed calculation unit 15 proceeds to step S523, and the modulation unit 5 subtracts ΔP from the reception C / N margin. Reflects the transmission line speed based on. In order to reflect the reception margin from the known required power received on the return link as the margin of the forward link where the own station 11 emits radio waves, if the transmission line speed is changed beyond the specified power difference ΔP, the margin of the forward link The above changes are likely to occur. Therefore, ΔP is set as a level difference that is not controlled.

  FIG. 17 is a flowchart of the transmission line speed control sequence continuation determining portion in step S6 in the transmission line speed control sequence shown in FIG. The continuation of the transmission line speed control sequence is determined based on the reception synchronization (step S61) of the demodulator 3 in the own station 11 when the transmission line speed control sequence is performed. The modulation unit 5 of the station 11 is stopped (step S62), and then the process proceeds to a transmission power control sequence start determination (step S4).

  As described above, the satellite communication apparatus according to Embodiment 2 of the present invention allows the own station 11 to consider the power difference that does not control the specified power difference ΔP in the reception C / N margin of the return link, and to transmit the forward link transmission line. Since speed control is performed, it is possible to prevent a reception error of the partner station 12 due to excessive control of the transmission line speed. In addition, this method eliminates the need for a control line for notifying the margin value of transmission power between the own station 11 and the partner station 12, thereby generating overhead due to extra control data that occupies the bandwidth of the satellite line. Can be prevented.

  Embodiment 3

  A satellite communication apparatus according to Embodiment 3 of the present invention will be described with reference to FIG. FIG. 18 is a functional block diagram showing the configuration of the satellite communication apparatus according to Embodiment 3 of the present invention. In the satellite communication apparatus shown in FIG. 18, the control unit 7 includes both the transmission power calculation unit 9 and the transmission line speed calculation unit 15. In FIG. 15, the circuits and components denoted by the same reference numerals as those in FIG. 1 are the same or corresponding circuits and components as those circuits and components in FIG.

In the satellite communication apparatus shown in FIG. 18, the control unit 7 uses the reception C / N margin calculated by the reception C / N margin calculation unit 8 for transmission power control by the transmission power calculation unit 9 or calculates the transmission line speed. Whether to use for transmission line speed control by the unit 15 is selected. The selection itself may be set from the user I / F to the satellite communication device depending on whether the operator of the device gives priority to transmission power or line speed, and a preferable transmission power and transmission line speed are set in advance in the satellite. It may be set in the communication device, and the control with the larger ratio of the deviation amount from the current value may be selected, and selection of which control is performed can be performed by various methods.

  As described above, the respective controls in a state where either the transmission power control or the transmission line speed control is selected by the control unit 7 are as described in the first embodiment and the second embodiment.

DESCRIPTION OF SYMBOLS 3 Demodulation part 5 Modulation part 7 Control part 8 Reception C / N margin calculation part 9 Transmission power calculation part 10 Satellite station 11 Local station satellite communication apparatus 12 Counter station satellite communication apparatus 15 Transmission line speed calculation part

Claims (3)

In a satellite communication device that performs satellite communication with a partner station satellite communication device via a satellite station by a forward link that is transmitted to the partner station satellite communication device and a return link that is received from the partner station satellite communication device ,
The partner station satellite communication device is capable of transmission power control,
A demodulator that demodulates a received signal received by the return link and measures a power level; a modulator that modulates a transmission signal that is transmitted by the forward link and varies transmission power; and a power level that is measured by the demodulator A power margin value is calculated from, a control unit that calculates a transmission power control value by subtracting a specified power difference between the return link and the forward link and commands the modulation unit, and
The control unit again calculates the transmission power control value by subtracting the specified power difference between the return link and the forward link, and absorbs the time difference from the execution of the transmission power control in the partner station satellite communication device. A satellite communication device that commands the modulation unit after a predetermined time elapses .   In a satellite communication device that performs satellite communication with a partner station satellite communication device via a satellite station by a forward link transmitted to the partner station satellite communication device and a return link received from the partner station satellite communication device,
A demodulator that demodulates a received signal received by the return link and measures a power level; a modulator that modulates a transmission signal that is transmitted by the forward link and varies transmission power; and a power level that is measured by the demodulator A control unit that calculates a power margin value from the value, calculates a transmission line speed control value based on a value obtained by subtracting a specified power difference between the return link and the forward link, and instructs the modulation unit,
The control unit again calculates a transmission line speed control value based on a value obtained by subtracting the specified power difference between the return link and the forward link, and after a predetermined time has passed, instructs the modulation unit to periodically Performs transmission line speed controlSatellite communication device.   3. The satellite communication device according to claim 1, wherein the control unit calculates a power margin value from an average of the power level measured by the demodulation unit over the predetermined time.

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