Satellite communication device, its transmitter and transmission method

Abstract

To perform such a control that output power of satellite communication equipment does not exceed application power even when a modem with a test function that demands the BUC output characteristics of a transmitter by changing the output level irregularly during operation is used.SOLUTION: In satellite communication equipment according to an embodiment, a modem includes: a modulation / demodulation function that modulates communication data from a communication terminal into an IF band communication signal, transmits and outputs the modulated signal, demodulates the IF band communication signal obtained by receiving radio waves from a communication satellite, and outputs the signal to the communication terminal; and a test function that demands the BUC transmission output characteristics by changing the output level of the communication signal that is transmitted and output irregularly. A transmitter includes a BUC that receives the IF band communication signal from the modem and converts the signal to the RF band, amplifies the power of the communication signal converted to the RF band, and outputs the signal, detects the power value of the amplified output, and control the input level of the IF band communication signal from the modem such that the detected power value does not exceed a power upper limit threshold.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present embodiment relates to a satellite communication device, its transmitter and transmission method. [Background technology]

[0002] VSAT (Very Small Aperture Terminals: ultra-small satellite communication) devices are communication devices for communicating with geostationary satellites, and have a relatively small antenna aperture. In recent years, VSAT devices have become even smaller, and now, for example, not only vehicle-mounted devices but also portable devices are provided, and their mobility has led to their use in disaster sites and other places. They are also often used in conjunction with mobile communication infrastructure. By connecting communication terminals such as telephones and TVs to each MODEM (Modulator-Demodulator) of this VSAT device, communication via satellite line becomes possible, and communication such as telephone, TV conference, and e-mail can be carried out between control stations and disaster sites, or between disaster sites.

[0003] The main components of the above VSAT equipment are a MODEM connected to a transmitting and receiving antenna via a transmitter and receiver that includes frequency converters such as a BUC (Block Up-Converter) for transmission and an LNC (Low Noise block down-Converter) for reception.

[0004] In VSAT equipment, the modem output level is usually adjusted first when establishing satellite communications. If the reception level changes significantly during operation, the modem output level may be changed manually, but once operation has begun, the modem output level is generally not changed.

[0005] In response to this, some recent modems are equipped with a test function that changes the output level at irregular intervals to determine the BUC's P1dB (1 dB gain compression point: an output characteristic that indicates the linearity of a linear amplifier, and represents the output level at which the gain drops by 1 dB relative to the ideal characteristic of the gain line) in order to ensure communication quality.

[0006] In contrast, existing transmitters are designed on the assumption that the modem will not change its output level during operation, and are not equipped with a function to adjust the output power.As a result, if the P1dB of the transmitter's BUC is higher than the output power approved by application (hereinafter referred to as the applied power), when the modem's output level, i.e., the BUC input level, is increased by the test function during modem operation, the BUC output power will exceed the applied power, resulting in the transmission of illegal radio waves. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2012-95196 A [Patent Document 2] Japanese Patent Application Publication No. 6-104777 [Patent Document 3] Japanese Patent Application Publication No. 5-191184 Summary of the Invention [Problem to be solved by the invention]

[0008] As described above, in conventional ultra-small satellite communication devices, when a modem with a test function is used that changes the output level irregularly during operation to obtain P1dB as the output characteristic of the up-converter in the transmitter, if the P1dB of the up-converter is large compared to the applied power, the device will transmit radio waves that exceed the applied power.

[0009] The objective of this embodiment is to provide a satellite communications device, a transmitter thereof, and a transmission method thereof that can control the output power so as not to exceed the applied power, even when a modem with a test function is used that changes the output level irregularly during operation to determine the output characteristics of the upconverter of the transmitter, and that can suppress the transmission of radio waves that exceed the applied power. [Means for solving the problem]

[0010] In order to solve the above problems, the satellite communication device according to this embodiment comprises a modem, a transmitter, an antenna, and a receiver. The modem has a modulation / demodulation function for modulating communication data from a communication terminal into an intermediate frequency band communication signal and transmitting and outputting it, and a demodulation function for receiving radio waves from a communication satellite and demodulating the intermediate frequency band communication signal obtained, and outputting it to the communication terminal, and a test function for irregularly changing the output level of the communication signal to be transmitted and outputted to obtain the transmission output characteristics. The transmitter has an output controller which compares the detected power value detected by the detector with a power upper limit threshold, and when the detected power value exceeds the power upper limit threshold, instructs the variable attenuator to increase the attenuation amount stepwise from an initial setting value until the detected power value falls below the power upper limit threshold, and after the detected power value falls below the power upper limit threshold, instructs the variable attenuator to return the attenuation amount stepwise to the initial setting value. The antenna transmits the radio frequency communication signal output from the transmitter to a communication satellite and receives the radio frequency communication signal from the communication satellite. The receiver amplifies the radio frequency communication signal received by the antenna, converts it to an intermediate frequency band, and outputs it to the modem. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a diagram showing an example of a satellite communication system to which an embodiment is applied. [Diagram 2] FIG. 2 is a plan view showing the external configuration of a satellite communication device used in a fixed station of the satellite communication system shown in FIG. 1 as a first embodiment. [Diagram 3] FIG. 3 is a block diagram showing a schematic configuration of a main body of the satellite communication device shown in FIG. [Figure 4] FIG. 4 is a block diagram showing the configuration of a communication processing system and a control processing system of the satellite communication device shown in FIG. [Diagram 5] FIG. 5 is a block diagram showing the configuration of a transmitter used in the satellite communication device shown in FIG. [Figure 6]FIG. 6 is a flowchart showing a control process for limiting the output power to the requested power in the transmission output controller of the transmitter shown in FIG. [Figure 7] FIG. 7 is a plan view showing an outer configuration of a satellite communication device used in a vehicle-mounted station or a portable station in the satellite communication system shown in FIG. 1 as a second embodiment. [Figure 8] FIG. 8 is a block diagram showing the configuration of a signal processing system and a control processing system of the satellite communication device shown in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, embodiments will be described with reference to the drawings.

[0013] A satellite communication system comprises multiple earth stations that communicate with each other via satellites in geostationary orbit. This satellite communication system is applied as a wide-area disaster prevention radio system, for example, to the disaster prevention system of a wide area municipality such as a prefecture. Specifically, live images taken at a disaster site can be transmitted from the satellite communication device to an earth station in a prefectural capital or the like via a satellite line. This allows the disaster situation to be known quickly and accurately.

[0014] FIG. 1 is a diagram showing an example of a satellite communication system to which an embodiment is applied. This system is formed with a communication satellite SAT in geostationary orbit as its core. On the ground side, fixed stations FS1 to FSn are installed in, for example, prefectural capitals. A vehicle-mounted station MS1 ​​or a portable station MS2 can also be installed in a disaster site or the like. The fixed stations FS1 to FSn, the vehicle-mounted station MS1, and the portable station MS2 each include a communication satellite device, and are capable of communicating with each other via the communication satellite SAT.

[0015] For example, images of the disaster site can be sent via satellite to the main base (fixed station FS1) and each base (fixed stations FS2 to FSn) to help grasp the disaster situation. In addition, satellite-based VoIP (Voice over IP) calls and TV conferences can be used to share information between related departments and hold disaster response discussions.

[0016] This type of system is often constructed as one of the disaster prevention systems of local governments. The method of allocating lines to satellite communication equipment is called DAMA (Demand Assignment Multiple Access). Control stations installed at several points on the ground are responsible for controlling DAMA.

[0017] (First embodiment) Fig. 2 is a plan view showing the external configuration of a fixed type satellite communication device 10 used in a fixed station of the satellite communication system shown in Fig. 1 as a first embodiment, where (a) is a top view, (b) is a side view of (a) seen from the top in the figure, (c) is a side view of (a) seen from the bottom in the figure, (d) is a side view of (a) seen from the left in the figure, and (e) is a bottom view. The satellite communication device 10 shown in Fig. 2 is a so-called VSAT device, and is composed of a main body unit 20 and an antenna unit 30, and although details are not shown, the antenna pointing direction of the antenna unit 30 is fixed in a state facing the communication satellite SAT.

[0018] The main body 20 contains a signal processing board 21 in a housing 22, to which electronic components such as a power switch 23, a power connector 24, a LAN connector 25, and a transmission / reception monitor 26 are attached, and the signal processing board 21 is connected to each electronic component inside the housing 22.

[0019] The power switch 23 is a switch that controls the start and stop of the device by turning the power on and off. The power connector 24 is a connector that is connected to an AC 100V power line, and turns on and off the connection to the power line in response to the on / off operation of the power switch 23. The LAN connector 25 is a connector that is connected to a wireless or wired network. The transmission / reception monitor 26 is a display that monitors and displays the power value of the signal distributed from the communication signal during transmission and reception.

[0020] The antenna unit 30 is a flat transmitting / receiving antenna in which an antenna board 31, on which antenna elements are arranged in an array, is housed in a radome 32. A power feeding end of the antenna board 31 is connected to an RF transmitting / receiving end of the signal processing board 21 of the main body unit 20.

[0021] FIG. 3 is a block diagram showing a schematic configuration of the main body 20 of the satellite communication device 10 shown in FIG.

[0022] 3, the signal processing board 21 of the main body 20 includes a modem 211, a wireless unit 212, a processor 213, a two-way distributor (two types for transmission and reception) 214, a filter 215, and an AC / DC converter 216.

[0023] The MODEM 211 is a modulation / demodulation unit connected to the LAN connector 25. The MODEM 211 modulates communication data from a communication terminal connected to the LAN connector 25, generates a baseband IF band communication signal, outputs it to the wireless unit 212, receives the IF band communication signal from the wireless unit 212, demodulates the communication data, and outputs it to the communication terminal.

[0024] The radio unit 212 frequency-converts (up-converts) the baseband IF band communication signal sent from the MODEM 211 to an RF band signal using the BUC, power-amplifies the signal, and sends it to the antenna section 20. The radio unit 212 also low-noise-amplifies the RF band communication signal received from the communication satellite SAT by the antenna section 30, and frequency-converts (down-converts) the signal to a baseband IF band signal using the LNC, and sends it to the MODEM 211.

[0025] The processor 213 is configured with an arithmetic processing device such as a CPU (Central Processing Unit) or an MPU (Micro Processing Unit), and is a control unit that controls the signal processing of the modem 211 and the wireless unit 212.

[0026] The two-way distributor 214 distributes the communication signal from the modem 211 to the radio unit 212 and the communication signal from the radio unit 212 to the modem 211 into two signals and sends them to the transmission / reception monitor 26 .

[0027] The filter 215 is a filter that cuts out noise components that are mixed in from the AC 100V power line connected to the power connector 24 .

[0028] The AC / DC converter 216 is a conversion section that converts the AC 100V AC voltage input through the filter 215 into a DC voltage, adjusts the voltage appropriately, and supplies it to the modem 211, the wireless unit 212, the processor 213, the 2-way distributor 214, and the transmission / reception monitor 26.

[0029] FIG. 4 is a block diagram showing the configuration of a communication processing system and a control processing system of the satellite communication device 10 shown in FIG.

[0030] 4, a Wi-Fi (registered trademark for wireless LAN) router 200 is connected to the LAN connector 25 to which the modem 211 is connected. As a result, the modem 211 is wirelessly connected to communication terminals such as a notebook PC 201, a VoIP phone 202, and a tablet 203 via the Wi-Fi router 200. The modem 211 has a modulation / demodulation function of modulating communication data from the communication terminal, generating a baseband IF band communication signal, outputting the signal to the wireless unit 212 via a two-way distributor 214, inputting the IF band communication signal supplied from the wireless unit 212 via the two-way distributor 214, demodulating the communication data, and outputting the signal to the communication terminal, and a test function of irregularly changing the output level to obtain the output characteristics of the frequency conversion.

[0031] The radio unit 212 sends the baseband IF band communication signal sent from the modem 211 via the two-way distributor 214 to the transmitter 2121. The transmitter 2121 has a BUC that frequency converts (up-converts) the IF band communication signal into an RF band signal. The transmitter 2121 power-amplifies the RF band communication signal obtained by frequency-converting the IF band communication signal from the modem 21 in the BUC, and sends the amplified signal to the antenna section 30 via the RF branch / combiner 2122. The antenna section 30 transmits the RF band communication signal output from the radio unit 212 toward the communication satellite SAT.

[0032] Furthermore, the antenna unit 30 receives an RF band communication signal transmitted from the communication satellite SAT, and transmits the RF band communication signal to the radio unit 212. The radio unit 212 transmits the RF band communication signal received by the antenna unit 30 from the communication satellite SAT to the receiver 2123 via the RF branch / combiner 2122. The receiver 2123 includes an LNC that frequency converts (down-converts) the RF band communication signal to a baseband IF band signal. The receiver 2123 performs low-noise amplification on the RF band communication signal from the antenna unit 30, frequency converts the signal to an IF band communication signal in the LNC, and transmits the signal to the MODEM 211 via the two-way distributor 214. The MODEM 211 demodulates communication data from the input baseband IF band communication signal, and transmits the demodulated data to a designated communication terminal. This enables data communication via the communication satellite SAT.

[0033] Here, in order to ensure communication quality, the modem 211 is equipped with a test function that irregularly changes the output level and obtains the P1dB of the BUC in the transmitter 2121. In this case, if the P1dB of the BUC being used is large compared to the applied power, the modem 211 will transmit radio waves that exceed the applied power when it increases the output level. Therefore, in this embodiment, the transmitter 2121 is equipped with a function that suppresses the output power to below the applied power.

[0034] FIG. 5 is a block diagram showing a specific configuration of the transmitter 2121. As shown in FIG.

[0035] In Fig. 5, the transmitter 2121 is a transmitter that amplifies an IF band communication signal from the MODEM 211 with a predetermined gain using a first stage amplifier T1, and further attenuates the signal based on a control signal that specifies the amount of attenuation using a digital variable attenuator (DATT) T2, and outputs the signal to the BUC. The BUC is composed of a middle stage amplifier T3 and a mixer T4. The BUC amplifies the IF band communication signal from the variable attenuator T2 with a predetermined gain using the middle stage amplifier T3, mixes the IF band communication signal with a local oscillation signal LO in the mixer T4, frequency converts (up-converts) the signal to an RF band communication signal, and outputs the signal to the final stage amplifier T5. The final stage amplifier T5 power-amplifies the RF band communication signal from the BUC with a predetermined gain, and outputs the signal to the antenna unit 30 via a splitter T6. Here, the splitter T6 splits a part of the input RF band communication signal and sends it to an RF power detector T7. The RF power detector T7 receives the RF band communication signal branched by the brancher T6, periodically detects the power of the signal, and notifies the power value to the transmission output controller T8. When the processor 213 gives an operation instruction to the transmission output controller T8 upon connection to the communication line, the transmission output controller T8 sets the attenuation of the variable attenuator T2 to an initial value.

[0036] FIG. 6 is a flowchart showing a control process in the transmission output controller T8 for limiting the output power to the requested power.

[0037] In FIG. 6, when an RF detection power value (hereinafter, detection power value) Pd detected by an RF power detector T7, for example, on a second-by-second basis, is input (step S11), the transmission output controller T8 compares the detection power value Pd with a previously registered upper allowable value (hereinafter, upper limit threshold) Pref for the applied power, and determines whether the detection power value Pd exceeds the upper limit threshold Pref (step S12).

[0038] In step S12, if the detected power value Pd exceeds the upper threshold Pref (YES), the transmission output controller T8 increases the attenuation of the variable attenuator T2 by 0.5 dB from the initial setting value (the previous setting value for the next time) (step S13), reduces the power of the IF band communication signal before upconversion, controls the detected power value Pd of the RF band communication signal after upconversion to be equal to or lower than the upper threshold Pref, and waits (1 second) for input of the next detected power value Pd (step S14).

[0039] In step S12, while the detected power value Pd is below the upper threshold Pref (NO), the transmission output controller T8 determines whether the attenuation amount of the variable attenuator T2 is the initial setting value (step S15).

[0040] In step S15, if it is the initial setting value (YES), the process waits (1 second) for the input of the next detected power value Pd (step S16), and returns to step S11.

[0041] In step S15, if the attenuation of the variable attenuator T2 is not the initial setting value (NO), the transmission output controller T8 reduces the attenuation of the variable attenuator T2 by 0.5 dB (step S17), proceeds to step S16, and thereafter gradually returns it to the initial setting value in 0.5 dB steps.

[0042] On the other hand, in step S12, if the detected power value Pd exceeds the upper threshold Pref (YES), the transmission output controller T8 increases the attenuation of the variable attenuator T2 (step S13) to reduce the power of the IF band communication signal before upconversion, and controls so that the detected power value Pd of the RF band communication signal after upconversion becomes equal to or less than the upper threshold Pref. Then, the controller waits for one second (step S14) and returns to step S11.

[0043] That is, in this embodiment, the modem 211 and the transmitter 2121 are configured not to perform mutually coordinated control. The transmitter 2121 normally converts the frequency of the IF band communication signal output from the modem 211 to an RF signal using the BUC, amplifies the signal with a predetermined gain, and transmits the signal to the antenna unit 30. Therefore, whether the IF output level of the modem 211 has changed is detected by detecting the RF output level inside the transmitter 2121. Since the IF output level of the modem 211 changes irregularly, the RF output level of the transmitter 2121 is constantly detected. When the RF output level of the transmitter 2121 exceeds a set upper threshold level, the attenuation amount of the digital variable attenuator T2 inside the transmitter 2121 is controlled so that the RF output level does not exceed the set threshold level.

[0044] As described above, according to the satellite communication device of this embodiment, if the modem 211 is equipped with a function for irregularly changing the output level to obtain P1 dB of the BUC of the transmitter 2121, when it is detected that the output power of the transmitter 2121 exceeds the upper limit threshold for the applied power when the output level of the modem 211 is increased, the power of the IF band communication signal before up-conversion is reduced and the detected power value Pd of the RF band communication signal after up-conversion is controlled to be equal to or lower than the upper limit threshold value Pref of the applied power, thereby reliably suppressing the transmission of radio waves exceeding the applied power.

[0045] Incidentally, while the test function is being executed, the modem 211 does not actually measure the power of the transmitter 2121, but communicates with the control station to simply check the C / N ratio. In other words, when the RF communication signal output from the transmitter 2121 increases by 1 dB, the C / N ratio also increases by 1 dB where linearity is achieved. Based on this, the C / N ratio is simply regarded as the output power of the transmitter 2121, and the P1dB point is found. For this reason, even if the output power of the transmitter 2121 is suppressed while the test function of the modem 211 is being executed, this does not affect the processing of the test function of the modem 2121.

[0046] (Second Example) FIG. 7 is a side plan view showing the exterior of a portable satellite communication device 40 used in the vehicle-mounted station MS1 ​​or portable station MS2 of the satellite communication system shown in FIG. 1 as a second embodiment, and FIG. 8 is a functional block diagram showing the communication processing system and control processing system of the satellite communication device 40 shown in FIG. 7.

[0047] The satellite communication device 40 is a so-called VSAT device, and also functions as a satellite capture device. Its size is compact enough for users to carry it around, and its weight is also kept low. This satellite communication device 40 can be carried to a disaster site, for example, and used as an emergency communication station.

[0048] The satellite communication device 40 comprises a main body unit 50 which modulates and demodulates communication signals, an azimuth angle control unit 60 which controls the antenna azimuth angle located at the top of the main body unit 50, an elevation angle control unit 70 which controls the antenna elevation angle located at the top of the main body unit 50, a polarization angle control unit 80 which controls the antenna polarization angle, a radio unit 90 which transmits and receives communication signals, and an antenna unit 100 which is integrated with the radio unit 90 and transmits and receives radio waves to and from the communication satellite SAT via a planar antenna.

[0049] The main body 50 has a signal processing board 51 housed in a housing 52, and a LAN connector 53 is attached to the side of the housing 52. Furthermore, a position sensor 54, a tilt sensor 55, and a memory 56 are provided inside. Also, three or more support legs 57 are provided on the bottom surface of the housing 51.

[0050] The signal processing board 51 includes a modem 511 as a communication processing system, and a processor (such as a CPU (Central Processing Unit) or an MPU (Micro Processing Unit)) 512 as a control processing system.

[0051] The modem 511 is a modulation / demodulation unit having modulation / demodulation functions and test functions similar to those of the modem 211 of the first embodiment. The modem 511 is connected to the LAN connector 53, modulates communication data from a communication terminal connected to the LAN connector 53, generates a baseband IF band communication signal, outputs it to the wireless unit 90, receives the IF band communication signal from the wireless unit 90, demodulates the communication data, and outputs it to the communication terminal.

[0052] The processor 512 is composed of an arithmetic processing device such as a CPU (Central Processing Unit) or an MPU (Micro Processing Unit). The processor 512 has a function of controlling signal processing of the modem 511 and the radio unit 90, as well as a function of executing a pointing control process S1 for controlling the pointing direction of the antenna unit 100, a satellite capture process S2 for capturing radio waves from the communication satellite SAT, and a line control process S3 for connecting a communication line with the communication satellite SAT.

[0053] The position sensor 54 is a sensor that acquires, for example, by a Global Positioning System (GPS), position information (for example, latitude and longitude) of the installation location of the satellite communication device 40. The position information acquired by the position sensor 54 is passed to the processor 512.

[0054] The tilt sensor 55 is a sensor that acquires tilt information including the amount of tilt of the main body 50 at the installation location. The amount of tilt can be acquired, for example, by using an acceleration sensor to detect the gravitational acceleration of the earth at the installation location. The information on the amount of tilt, etc. can be used as an index showing the attitude of the satellite communication device 40. The acquired tilt information is passed to the processor 512.

[0055] The memory 56 is a storage unit that stores tilt information 561 and a satellite target angle table 562. The tilt information 561 is tilt information sensed by the tilt sensor 55. The satellite target angle table 562 is a table that associates satellite target angles (azimuth angle, elevation angle, polarization angle) of a communication satellite SAT to be captured with terrestrial position information (e.g., latitude, longitude) sensed by the position sensor 54. For example, it is shown that the latitude of Sapporo city in Hokkaido is 141.4° and the longitude is 43.1°, and that at this position, the target angles (azimuth angle, elevation angle, polarization angle) of a certain communication satellite SAT are (151.2°, 36.1°, 10.4°).

[0056] Each of the three or more support legs 57 has a height adjustment mechanism. When installing the satellite communication device 40, the height of each of the three or more support legs 57 is adjusted so that the reference plane (the upper surface of a turntable 61 described later) is horizontal.

[0057] The azimuth angle control section 60 includes a turntable 61 and an azimuth angle control unit 62. The azimuth angle control unit 62 includes an azimuth angle control motor controller 621 and an azimuth angle control motor 622 therein.

[0058] The turntable 61 is disposed on the upper part of the housing 52 of the main body 50 so as to be rotatable about a rotation axis (azimuth axis or AZ (Azimuth) axis) A1. An azimuth angle control motor 622 is engaged with the turntable 61. An azimuth angle control motor control unit 621 drives and controls the azimuth angle control motor 622, thereby rotating the turntable 61 to a specified antenna azimuth angle.

[0059] The elevation angle control section 70 includes a support column 71 , a bearing 72 , and an elevation angle control unit 73 .

[0060] The support column 71 supports the housing of the polarization angle control section 80 from both sides, and physically connects the main body section 50 and the rear housing of the radio section 90 through the polarization angle control section 80. The bearing 72 is disposed on the upper surface of the turntable 61, and one end side of the support column 71 is attached so as to be freely rotatable around a rotation axis (elevation axis or EL (Elevation) axis) A2. The elevation angle control unit 73 includes an elevation angle control motor controller 731 and an elevation angle control motor 732 therein. The rotation axis of the elevation angle control motor 732 is engaged with the bearing 72. The elevation angle control motor controller 731 drives and controls the elevation angle control motor 732, thereby allowing the support column 71 to rotate around the rotation axis A2 to a specified antenna elevation angle.

[0061] The polarization angle control unit 80 includes a coupler 81 and a polarization angle control unit 82. The coupler 81 connects the housing of the polarization angle control unit 82 to the rear surface of the integrated unit of the radio unit 90 and the antenna unit 100 so as to be rotatable about a rotation axis (polarization axis or POL (Polarization) axis) A3. The polarization angle control unit 82 includes a polarization axis control motor control unit 821 and a polarization axis control motor 822 therein.

[0062] The rotating shaft of the polarization angle control motor 822 is engaged with the coupler 81. The polarization angle control motor control unit 821 drives and controls the polarization angle control motor 822, thereby allowing the coupler 81 to rotate to a specified antenna polarization angle.

[0063] The radio section 90 includes a housing 91 integrated with the rear surface of the antenna section 100, and is housed therein a radio unit 92, two 2-way distributors 93, a transmission / reception monitor 94, and a received radio wave intensity detector 95.

[0064] The radio unit 92 has the same configuration as the radio unit 212 of the first embodiment, and includes a transmitter 921, an RF branching / combining unit 922, and a receiver 923, and frequency-converts a baseband intermediate frequency band (hereinafter, IF band) signal sent from the modem 511 of the main body unit 50 to a radio frequency band (hereinafter, RF band) signal by a BUC included in the transmitter 921 and outputs the signal to the antenna unit 100, and frequency-converts the RF band signal from the antenna unit 100 to an IF band signal by an LNC included in the receiver 923 and outputs the signal to the modem 511. The specific configuration of the transmitter 922 is similar to that of the transmitter 2121 of the first embodiment shown in Fig. 4, and therefore a description thereof will be omitted here.

[0065] The two-way distributor 93 , like the two-way distributor 214 in the first embodiment, distributes communication signals from the modem 511 to the radio unit 92 and from the radio unit 92 to the modem 511 in two directions, and sends the signals to the transmission / reception monitor 94 .

[0066] The transmission / reception monitor 94, like the transmission / reception monitor 26 in the first embodiment, is a display device that displays a monitor of the power value of a signal distributed from a communication signal during transmission and reception.

[0067] The received radio wave intensity detector 95 detects the received radio wave intensity from the antenna reception signal obtained by the receiver 923 of the wireless unit 92 , and sends it to the processor 512 of the main body 50 .

[0068] The antenna section 100 is a flat type transmitting / receiving antenna in which an antenna substrate 101, on which antenna elements are arranged in an array, is housed in a radome 102, similar to the antenna section 30 of the first embodiment.

[0069] The power supply end of the antenna board 101 is connected to an RF transmitting / receiving end of the radio section 90. That is, the antenna section 100 transmits an RF band communication signal output from the radio unit 92 toward the communication satellite SAT, receives an RF band communication signal transmitted from the communication satellite SAT, and transmits the RF band communication signal to the radio unit 92.

[0070] Here, the size of the antenna unit 100 is, for example, 50 cm×50 cm. In addition to the planar antenna shown in the figure, for example, a parabolic antenna can also be used. The antenna unit 100 is designed to have a sharp directivity in order to minimize the energy loss of radio waves. For this reason, the satellite communication device 40 includes an azimuth angle control unit 60, an elevation angle control unit 70, and a polarization angle control unit 80 as an antenna pointing control system for accurately aligning the azimuth angle (AZ), elevation angle (EL), and polarization angle (POL) to the communication satellite SAT, which are three different axes.

[0071] A method for connecting the satellite communication device 40 having the above configuration to the communication satellite SAT after the device is installed at an arbitrary location will be described.

[0072] When the main body unit 50 is started, the processor 512 directs the antenna of the antenna unit 100 to the communication satellite SAT by a direction control process S1, captures radio waves from the communication satellite SAT by a satellite capture process S2, adjusts the direction of the direction so that the radio wave strength is at a sufficient level, and then connects a communication line with the communication satellite SAT by a line control process S3 to communicate with the communication terminal. The processing contents of the direction control process S1, the satellite capture process S2, and the line control process S3 will be explained in order below.

[0073] First, in the above-mentioned pointing control process S1, the direction of the communication satellite SAT is determined by referring to the satellite target angle table 562 in the memory 56 based on the position information sensed by the position sensor 54 and the tilt information stored in the memory 56, and the azimuth angle control unit 60, the elevation angle control unit 70, and the polarization angle control unit 80 are instructed of the target azimuth angle, elevation angle, and polarization angle. Upon receiving the instruction of the target azimuth angle, the azimuth angle control unit 60 drives and controls the azimuth angle control motor 622 by the azimuth angle control motor controller 621 to rotate the turntable 61 around the A1 axis, and align the antenna azimuth angle with the target azimuth angle. Upon receiving the instruction of the target elevation angle, the elevation angle control unit 70 drives and controls the elevation angle control motor 732 by the elevation angle control motor controller 731 to rotate the support column 71, the end of which is attached to the bearing 72, around the rotation axis A2, and align the antenna elevation angle with the target elevation angle. Upon receiving an instruction for the target polarization angle, the polarization angle control unit 80 controls the driving of the polarization angle control motor 822 by the polarization angle control motor controller 821 to rotate the coupler 81 around the rotation axis A3 and align the antenna polarization angle with the target polarization angle.

[0074] Here, in the above-mentioned directivity control process S1, the elevation angle of the antenna unit 100 is changed in conjunction with the rotation of the antenna unit 100 in the azimuth direction. At this time, the elevation angle of the antenna unit 100 is changed so that the elevation angle of the antenna unit 100 is constant regardless of the inclination of the main body unit 50, with reference to the inclination information 561 of the satellite communication device 40 sensed by the inclination sensor 55. The elevation angle of the antenna unit 100 corresponding to the rotation angle of the antenna unit 100 in the azimuth direction at this time is calculated based on the inclination information 561. Also, the rotation speed of the elevation angle control motor 732 corresponding to the calculated elevation angle is calculated.

[0075] That is, in the above-mentioned pointing control process S1, a 360-degree search is performed in the azimuth direction, the tilt of the satellite communication device 40 is measured by the tilt sensor 55, and tilt information is obtained. Then, based on the tilt information, an equation for calculating a simple elevation axis angle (ELVSAT) is derived from a linear algebra three-dimensional rotation equation. Furthermore, it is simplified to a six-point sampling algorithm. This relaxes the restrictions on software implementation, and makes it possible to reliably capture satellites with minimal resources.

[0076] In this case, the elevation (ELSAT) between the satellite communication device 40 and the satellite SAT is calculated from the position information of the satellite communication device 40, and the inclination of the satellite communication device 40 is corrected so that a 360-degree search can always be performed at the same elevation angle (ELSAT). In this way, it is possible to capture the satellite SAT without relying on a direction sensor.

[0077] Next, in the satellite capture process S2, the radio wave reception strength detected by the received radio wave intensity detector 95 of the radio unit 90 is monitored, and the angle at which the reception strength of the received signal peaks is detected. The azimuth angle, elevation angle, and polarization angle of the antenna unit 100 are then instructed to the azimuth angle control unit 60, elevation angle control unit 70, and polarization angle control unit 80, so that radio waves from the target communications satellite SAT are captured with sufficient gain.

[0078] In addition, in the line control process S3, after the satellite capture process S2 is completed, a communication line connection instruction is sent to the modem 511, the transmitter 921, and the receiver 922, and a communication line is established between the communication terminal connected to the modem 511 and the communication satellite SAT.

[0079] In the above configuration, the communication process after the communication line is established and the control process for limiting the output power in the transmission output controller T8 of the transmitter 921 to the requested power are the same as those in the first embodiment, so that the description thereof will be omitted here.

[0080] That is, in this embodiment as well, the modem 511 and the transmitter 921 are configured not to control each other in cooperation with each other. The transmitter 921 normally converts the frequency of the IF band communication signal output from the modem 511 to an RF signal using the BUC, amplifies the signal with a predetermined gain, and transmits the signal to the antenna unit 100. Therefore, whether the IF output level of the modem 511 has changed is detected by detecting the RF output level inside the transmitter 921. Since the IF output level of the modem 511 changes irregularly, the RF output level of the transmitter 921 is constantly detected. When the RF output level of the transmitter 921 exceeds a set upper threshold level, the attenuation amount of the digital variable attenuator T2 inside the transmitter 921 is controlled so that the RF output level does not exceed the set threshold level.

[0081] As described above, according to the satellite communication device 40 of this embodiment, if the MODEM 511 is equipped with a function for irregularly changing the output level to obtain P1dB of the BUC of the transmitter 921, when it is detected that the output power of the transmitter 921 exceeds the upper limit threshold for the applied power when the output level of the MODEM 511 is increased, the power of the IF band communication signal before upconversion is reduced and the detected power value Pd of the RF band communication signal after upconversion is controlled to be equal to or lower than the upper limit threshold value Pref of the applied power, thereby reliably suppressing the transmission of radio waves exceeding the applied power.

[0082] Incidentally, even in this embodiment, while the modem 511 is executing the test function, it does not accurately measure the power of the transmitter 921, but communicates with the control station to simply check the C / N ratio. In other words, when the RF communication signal output from the transmitter 921 increases by 1 dB, the C / N ratio also increases by 1 dB where linearity is achieved. Based on this, the C / N ratio is simply regarded as the output power of the transmitter 921, and the P1dB point is found. For this reason, even if the output power of the transmitter 921 is suppressed while the modem 511 is executing the test function, the processing of the modem 511 test function is not affected.

[0083] The present invention is not limited to the above-described embodiment as it is, and the components can be modified and embodied in the implementation stage without departing from the gist of the invention. In addition, various inventions can be formed by appropriately combining the multiple components disclosed in the above-described embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, components from different embodiments may be appropriately combined. [Explanation of symbols]

[0084] SAT...communication satellite, FS1~FSn...fixed station, MS1...vehicle station, MS2...portable station, 10...Satellite communication device (VSAT device), 20...main body, 21...signal processing board, 211...MODEM, 212...radio unit, 2121...transmitter, T1...first stage amplifier, T2...variable attenuator (DATT), T3...middle stage amplifier, T4...mixer, T5...final stage amplifier, T6...splitter, T7...RF power detector, T8...transmission output controller, 2122...RF splitter / combiner, 2123...receiver, 213...processor, 214...2-way splitter, 215...filter, 216...AC / DC converter, 22...housing, 23...power switch, 24...power connector, 25...LAN connector, 26...transmission / reception monitor, 30...antenna unit, 31...antenna board, 32...radome, 200...Wi-Fi router, 201...notebook PC, 202...VoIP phone, 203...tablet, 40...satellite communications device (VSAT device), 50...main body, 51...signal processing board, 511...modem, 512...processor, S1...pointing control processing, S2...satellite capture processing, S3...line control processing, 52...housing, 53...LAN connector, 54...position sensor, 55...tilt sensor, 56...memory, 561...tilt information, 562...satellite target angle table, 57...support legs, 60: Azimuth angle control section, 61: Turntable, 62: Azimuth angle control unit, 621: Azimuth angle control motor controller, 622: Azimuth angle control motor, 70: elevation control section, 71: support column, 72: bearing, 73: elevation control unit, 731: elevation control motor controller, 732: elevation control motor, 80: polarization angle control section, 81: coupler, 82: polarization angle control unit, 821: polarization axis control motor control section, 822: polarization axis control motor, 90...radio section, 91...housing, 92...radio unit, 921...transmitter, 922...RF branch / combiner, 923...receiver, 93...2-way distributor, 94...transmission / reception monitor, 95...received radio wave intensity detector, 100...antenna portion, 101...antenna board, 102...radome.

Claims

1. a modem having a modulation / demodulation function for modulating communication data from a communication terminal into an intermediate frequency band communication signal, transmitting and outputting the signal, and demodulating the intermediate frequency band communication signal obtained by receiving radio waves from a communication satellite and outputting the signal to the communication terminal, and a test function for irregularly changing the output level of the communication signal to be transmitted and outputted, to determine transmission output characteristics; a variable attenuator for attenuating an input level of the upconverter by an attenuation amount according to a command, an amplifier for power-amplifying and outputting the communication signal converted to the radio frequency band by the upconverter, a detector for detecting a power value of the output power-amplified by the amplifier, and an output controller for comparing the detected power value detected by the detector with a power upper limit threshold, and when the detected power value exceeds the power upper limit threshold, for instructing the variable attenuator to increase the attenuation amount stepwise from an initial setting value until the detected power value falls below the power upper limit threshold, and for instructing the variable attenuator to return the attenuation amount stepwise to the initial setting value after the detected power value falls below the power upper limit threshold; an antenna that transmits a radio frequency band communication signal output from the transmitter to a communication satellite and receives a radio frequency band communication signal from the communication satellite; a receiver for amplifying a radio frequency communication signal received by the antenna, converting the signal into an intermediate frequency band, and outputting the signal to the modem; A satellite communication device comprising:

2. A transmitter for use in a satellite communication device using a modem having a modulation / demodulation function for modulating communication data from a communication terminal into an intermediate frequency band communication signal, transmitting and outputting the signal, and demodulating the intermediate frequency band communication signal obtained by receiving radio waves from a communication satellite and outputting the signal to the communication terminal, and a test function for irregularly changing the output level of the communication signal to determine transmission output characteristics, an up-converter for converting an intermediate frequency band communication signal output from the modem into a radio frequency band; a variable attenuator for attenuating the input level of the up-converter by an attenuation amount according to a command; an amplifier that amplifies the power of the communication signal converted into the radio frequency band by the upconverter and outputs the amplified signal; a detector for detecting a power value of the output amplified by the amplifier; an output controller which compares the detected power value detected by the detector with a power upper limit threshold, and when the detected power value exceeds the power upper limit threshold, instructs the variable attenuator to increase the attenuation amount stepwise by a constant amount from an initial setting value until the detected power value falls below the power upper limit threshold, and instructs the variable attenuator to return the attenuation amount stepwise by a constant amount to the initial setting value after the detected power value falls below the power upper limit threshold; A transmitter for a satellite communication device comprising:

3. A transmission method for a transmitter used in a satellite communication device using a modem having a modulation / demodulation function for modulating communication data from a communication terminal into an intermediate frequency band communication signal, transmitting and outputting the signal, and demodulating the intermediate frequency band communication signal obtained by receiving radio waves from a communication satellite and outputting the signal to the communication terminal, and a test function for irregularly changing the output level of the communication signal to be transmitted and outputted, comprising: The transmitter includes: a frequency conversion step of converting an intermediate frequency band communication signal output from the modem into a radio frequency band by an up-converter; an attenuation step of attenuating an input level of an intermediate frequency band communication signal from said modem by a variable attenuator according to an instruction; an amplifying step of power-amplifying and outputting the communication signal converted into a radio frequency band in the frequency converting step by an amplifier; a detection step of detecting a power value of the output amplified by the amplifier by a detector; an output control step of comparing the detected power value detected by the detector with a power upper threshold by an output controller, and when the detected power value exceeds the power upper threshold, instructing the variable attenuator to increase the attenuation amount from an initial setting value in steps by a constant amount until the detected power value falls below the power upper threshold, and after the detected power value falls below the power upper threshold, instructing the variable attenuator to return the attenuation amount to the initial setting value in steps by a constant amount; A transmission method for a satellite communication device comprising:

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