System and method for helicopter satellite communication

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Technical field to which the invention belongs]

The present invention relates to a helicopter satellite communication system and a helicopter satellite communication method in which a communication path is formed between a directional antenna mounted on a helicopter and a satellite to transmit and receive data.

【0002】

[Conventional technology]

Figure 5 shows a conceptual diagram of a helicopter satellite communication system. This helicopter satellite communication system is a system that relays communication satellites such as geostationary satellite 1 or orbiting satellite 2 at an altitude of 1000 km to send and receive data between helicopter 3 (hereinafter abbreviated as helicopter) and users on the ground. Is. In such a system, if high-speed data such as video (for example, several Mbps or more) is to be transmitted from the helicopter 3, it is necessary to provide the helicopter 3 with a directional antenna having a high directional gain (for example, 30 dBi). It is necessary to accurately track the directional antenna toward the communication satellite according to the movement of the communication satellite and the orbit of the communication satellite.

【0003】

A directional antenna as described above usually has a considerable size and mass. For example, in the case of an antenna with a carrier frequency of 26 GHz and a gain of 30 dBi, the diameter is about 30 cm and the mass is about 30 kg in terms of parabola. Such a large directional antenna that requires precise tracking is usually installed on the roof of a helicopter 3, but such a mounting position has a problem that the communication path with the communication satellite is blocked by a rotor (rotor blade). Produces.

【0004】

The communication path is cut off by the rotor for a length of about several ms, and when receiving compressed image high-speed data with low redundancy such as information compression, burst errors (random and sporadic) that cannot be repaired by the error correction function etc. Here, it means something like data loss that continues for a certain period of time.), And the received data becomes useless.

【0005】

As a technique for avoiding the influence of the rotor, there is a method of adopting a space diversity receiving method using a plurality of antennas. In this method, an antenna having a good received wave is selected from a plurality of antennas by utilizing the space diversity receiving function, and the antenna having a good receiving state is used for transmission.

【0006】

Various techniques have been proposed in addition to the method of adopting the space diversity reception described above. Below are some examples of techniques that have been proposed so far.

【0007】

For example, Japanese Patent Application Laid-Open No. 6-125287 is equipped with a satellite communication antenna under the rotor surface of a moving body, detects the rotation angle of the rotor, determines the period during which the rotor crosses the transmission radiation range of the antenna, and determines this determination. Based on the result, the baseband signal is time-axis compressed outside the rotor crossing period, and when the carrier signal is modulated by this compressed baseband signal, the carrier signal is on / off controlled inside and outside the rotor crossing period based on the rotor crossing discrimination result. However, a satellite communication device has been proposed in which the modulated signal is frequency-converted, the power is amplified, and the signal is transmitted to the antenna.

【0008】

Further, in Japanese Patent No. 2503883 (Japanese Unexamined Patent Publication No. 7-22993), by detecting the shielding of radio waves that occur periodically and performing communication within a time excluding the timing synchronized with the shielding of the radio waves. A satellite communication device that can eliminate the influence of radio wave shielding has been proposed.

【0009】

Further, in Japanese Patent Application Laid-Open No. 7-212122, when the beam of one antenna of at least a pair of antennas for satellite communication installed in a helicopter is blocked by the rotor of the helicopter, the beam of the other antenna is transferred to the rotor of the helicopter. By arranging it in an unobstructed position, signals with different shielding timings by the rotor exist independently in both the transmission and reception systems for each antenna, and by outputting and synthesizing multiple communication channel signals, the rotor moves. A satellite communication device has been proposed that maintains a full-duplex communication line regardless of.

【0010】

Further, in Japanese Patent Application Laid-Open No. 10-76999, the position of the rotor is detected, the average instantaneous interruption time of the antenna with the communication path is calculated from the detection result, and a plurality of antennas are switched based on the average instantaneous interruption time. It has been proposed to send and receive.

【0011】

Further, in Japanese Patent Application Laid-Open No. 5-167344, when the direction of viewing the communication satellite from at least one antenna is blocked by the rotor of the helicopter, the direction of viewing the communication satellite from the other antenna is not blocked by the rotor of the helicopter. It has been proposed that the antenna is arranged, the position of the rotor is detected, and the antenna is switched based on the detection result.

【0012】

[Problems to be Solved by the Invention]

In the method of adopting the space diversity reception described above, the transmission power is small, the burden on the transmission changeover switch for switching the output destination to the antenna is small (the one with sufficient power resistance or capable of high-speed switching can be used, etc.) ), Transmission speed is also low, etc., it is applicable when the error due to switching can be relieved by error control method etc., but data that requires high output radiation such as anti-communication satellite and does not tolerate data error In the case of transmission, the following problems occur.

【0013】

When transmitting data such as images from a helicopter to a satellite, the data rate is high, power of several tens of watts to several hundreds of watts is usually output, and the rotor of the helicopter continuously blocks the communication path many times during flight. For this reason, in the space diversity reception method in which hot switching is performed such as turning the switch on and off while the transmission output is on, the power resistance of the switch makes the load on the changeover switch excessive, and the switch lasts for a long time. Absent. Further, in the space diversity reception method, the switch is switched after the transmission output is cut, but such switching takes a time of about several tens of ms, so that the data transmission speed is restricted. For this reason, when the space diversity reception method is adopted for a communication satellite, there is a problem that it is difficult to construct a system.

【0014】

The one described in Japanese Patent Application Laid-Open No. 6-125287 is premised on low-speed data transmission, and since an antenna having a low directional gain is used, there is a problem that it cannot be applied to high-speed data transmission such as an image. In addition, there are the following problems.

【0015】

The relative position of the helicopter and the satellite changes every moment according to the movement / attitude of the helicopter and the orbit of the communication satellite, and the position where the rotating surface of the rotor intersects with the antenna beam also changes accordingly. It is also necessary to control the timing of turning ON / OFF according to the change. However, in the above-mentioned publication, since the timing at which the rotor passes directly above the antenna is calculated from only the rotation angle information of the rotor to control the ON / OFF of data transmission, the above-mentioned changes are made. It is not possible to control the transmission timing with. As described above, in the above-mentioned publication, since it is not possible to accurately determine the timing at which the communication path is shielded by the rotor, transmission data may be lost, resulting in deterioration of communication quality.

【0016】

The one described in Japanese Patent No. 2503883 (Japanese Unexamined Patent Publication No. 7-22993) is designed to derive the transmission timing from the helicopter by using the received wave. It is not possible to control the signal transmission timing according to changes in the relative position and the attitude / orientation of the helicopter.

【0017】

The ones described in JP-A-7-212122 and JP-A-5-167344 are designed to avoid the influence of rotor shielding only by the antenna arrangement, and those of these publications are also the same as the above publications. Similarly, it is not possible to control the signal transmission timing according to the relative position between the helicopter and the satellite and the change in the attitude and direction of the helicopter.

【0018】

The one described in JP-A No. 10-76999 is designed to calculate the average instantaneous interruption time from the position of the rotor and control the switching of the antenna based on the average instantaneous interruption time. However, after all, it is not possible to control the signal transmission timing according to the relative position between the helicopter and the satellite and the change in the attitude / direction of the helicopter.

【0019】

An object of the present invention is to solve the above problems, to perform data transmission such as a communication satellite that requires high-power radiation and tolerate data errors, and to obtain a relative position between a helicopter and a satellite. It is an object of the present invention to provide a satellite communication system and a satellite communication method of a helicopter having high communication quality, which can control the signal transmission timing according to a change in the attitude and orientation of the helicopter.

【0020】

[Means for solving problems]

In order to achieve the above object, the helicopter satellite communication system of the present invention is a helicopter satellite communication system in which a directional antenna is mounted on a helicopter and a communication path is formed between the directional antenna and the satellite to transmit and receive data. In the helicopter, the antenna angle detecting means for detecting the antenna angle of the directional antenna with the aircraft as a reference, the attitude / orientation detecting means for detecting the attitude / orientation of the aircraft, and the relative position between the helicopter and the satellite. The relative position detecting means for detecting the above, the rotor rotating position detecting means for detecting the rotation position of the rotor, the antenna angle detected by the antenna angle detecting means, the relative position detected by the relative position detecting means, and the above. A shielding timing determining means for determining the timing at which the rotor blocks the communication path based on the attitude / orientation detected by the attitude / orientation detecting means and the rotating position of the rotor detected by the rotor rotating position detecting means. It is characterized by having a signal transmitting means for asynchronously transmitting a transmission signal from the directional antenna based on the shielding timing determined by the shielding timing determining means.

【0021】

Further, the helicopter satellite communication system of the present invention is a helicopter satellite communication system in which a plurality of directional antennas are mounted on a helicopter and a communication path is formed between the plurality of directional antennas and the satellite to transmit and receive data. The helicopter has an attitude / orientation detecting means for detecting the attitude / orientation of the aircraft, a relative position detecting means for detecting the relative position between the helicopter and the satellite, and a rotor rotating position detecting means for detecting the rotating position of the rotor. And, based on the relative position detected by the relative position detecting means and the attitude / orientation detected by the attitude / orientation detecting means, the antenna pointing directions of the plurality of directional antennas are controlled and these directional directions are controlled. The antenna directional control means that selects an antenna suitable for transmission from the antennas and sends out the antenna directional direction information of the selected antenna, the antenna directional direction information sent from the antenna directional control means, and the relative position detecting means. Between the selected antenna and the satellite based on the relative position detected by the antenna, the attitude / orientation detected by the attitude / orientation detecting means, and the rotation position of the rotor detected by the rotor rotating position detecting means. A signal transmission that asynchronously transmits a transmission signal from the selected antenna based on the shielding timing determining means for determining the timing at which the rotor blocks the communication path formed in the above and the shielding timing determined by the shielding timing determining means. It is characterized by having means and.

【0022】

The helicopter satellite communication method of the present invention is a satellite communication method performed in a helicopter in which a directional antenna is mounted and a communication path is formed between the directional antenna and the satellite to transmit and receive data. The antenna angle based on the body of the sex antenna, the attitude / orientation of the body, the relative position between the helicopter and the satellite, and the rotation position of the rotor are detected, and based on these detection results, the rotor traverses the communication path. It is characterized in that the timing of blocking is determined, and the transmission signal is asynchronously transmitted from the directional antenna based on the blocking timing.

【0023】

Further, the helicopter satellite communication method of the present invention is a satellite communication method performed in a helicopter in which a plurality of directional antennas are mounted and a communication path is formed between the directional antennas and the satellite to transmit and receive data. The attitude and orientation of the aircraft and the relative position between the helicopter and the satellite are detected, and based on these detection results, the antenna pointing directions of the plurality of directional antennas are controlled and transmitted from among these directional antennas. The antenna suitable for the above is selected, the antenna angle with respect to the aircraft is detected for the selected antenna, the rotation position of the rotor is detected, and based on these detection results and the detected posture / orientation and relative position, the above-mentioned It is characterized in that the timing at which the rotor blocks the communication path formed between the selected antenna and the satellite is determined, and the transmission signal is asynchronously transmitted from the selected antenna based on the blocking timing.

【0024】

(Action) As mentioned in the above-mentioned issues, in a helicopter in flight, the antenna pointing direction changes every moment according to the relative position between the helicopter and the satellite and the change in the attitude and orientation of the helicopter. The timing at which the rotor blocks the communication path between the antenna and the satellite also changes. Therefore, in order to accurately determine the timing at which the rotor shields the communication path, it is necessary to detect the shielding timing according to the change in the antenna directivity direction.

【0025】

In the present invention as described above, the timing at which the rotor blocks the communication path is determined based on the antenna angle, the rotation position of the rotor, the attitude / orientation of the airframe, and the relative position between the helicopter and the satellite. It depends on the change in the direction of direction. Therefore, in the present invention, the timing at which the transmission signal is cut off is adjusted according to the change in the antenna directivity direction, and the transmission data is not lost.

【0026】

Further, in the present invention, since the timing at which the rotor shields the communication path is detected and the transmission signal is transmitted asynchronously based on the shielding timing, the transmission signal is transmitted asynchronously, as in the transmission adopting the conventional space diversity reception method. Hot switching such as turning the switch ON / OFF is not performed while the transmission output is ON. Therefore, in the present invention, there is no burden on the transmitting antenna switching mechanism and restrictions on the data transmission speed as in the conventional case.

【0027】

BEST MODE FOR CARRYING OUT THE INVENTION

Next, an embodiment of the present invention will be described with reference to the drawings. Here, since the outline of the helicopter satellite communication system is as shown in the system of FIG. 5 described above, the description of the outline is omitted, and the configuration of the helicopter transmission / reception system, which is a feature of the present invention, will be described in detail.

【0028】

FIG. 1 shows the format of a signal transmitted from a helicopter in the helicopter satellite communication system according to the embodiment of the present invention and the transmission timing thereof. As shown in FIG. 1, in the helicopter satellite communication system of the present embodiment, the transmission timing of high-speed transmission data from the helicopter is the time zone in which the rotor of the helicopter blocks the transmission path with the satellite (hereinafter referred to as "GT"). High-speed burst (asynchronous) communication is performed between GTs at a timing that avoids.

【0029】

Here, the cycle between GTs (the cycle in which the communication path is blocked by the rotor, hereinafter this cycle is referred to as "Ti") differs because the number of rotors, the number of rotations, etc. differ depending on the type of helicopter and the like. Specifically, as shown in FIG. 2, when two directional antennas 6 and 7 are provided on the roof of the helicopter, for example, the steering of the directional antenna 7, that is, the relative positional relationship between the helicopter and the satellite. The positions 4 and 5 where the rotor surface and the communication paths of the communication satellites 1a and 1b intersect are faster or slower with respect to the rotation direction of the rotor. In consideration of this, the helicopter transmitter of the present embodiment has a function of additionally detecting the rotation position (angle) of the rotor blade, a function of detecting the angle of the antenna, and a relative position between the helicopter and the satellite. It has a function to detect the attitude and orientation of the aircraft, and a transmission signal based on the antenna angle with respect to the aircraft, the relative position between the helicopter and the satellite, the attitude and orientation of the helicopter, the rotation position of the rotor blade, etc. It is configured to adjust by speeding up or slowing down the timing of cutting off. This adjustment is performed based on the transmission control signal Ti (cycle between GTs) transmitted from the following transmission control signal generation system.

【0030】

Figure 3 shows the main configuration of the transmission control signal generation system. The transmission control signal generation system includes a control device 11, an attitude orientation device 12, a Ti control device 13, a position detection device 14, an antenna direction control device 15, and a rotor position detection, each of which is connected via a helicopter control signal bus 10. It consists of device 16.

【0031】

The control device 11 controls each component. The attitude orientation device 12 detects the attitude and orientation of the helicopter, the position detection device 14 detects the relative position between the helicopter and the satellite, and the rotor position detection device 16 detects the position of the rotor.

【0032】

The antenna directional control device 15 controls the directions of a plurality of directional antennas provided on the roof of the helicopter based on the relative positions of the helicopter and the satellite and the attitude / orientation of the helicopter, and transmits from among these directional antennas. A suitable antenna is selected, and the antenna directivity information (antenna angle) of the selected antenna is transmitted onto the helicopter control signal bus 10. The timing of switching the selected antenna by the antenna directional control device 15 is the GT timing.

【0033】

The Ti control device 13 is a shielding timing determining means for determining the timing at which the rotor blocks the communication path between the directional antenna and the satellite, and is an antenna angle transmitted on the helicopter control signal bus 10, the helicopter and the satellite. The shielding timing is determined based on the relative position of the helicopter, the attitude / direction of the helicopter, and the position of the rotor, and the transmission control signal Ti (cycle between GTs) corresponding to the shielding timing is output.

【0034】

In the helicopter transmitter equipped with the above transmission control signal generation system, when transmitting high-speed data such as images to the satellite, the antenna on the side without obstacles based on the relative position of the helicopter and the attitude of the helicopter. At the same time, the data transmission and transmission output are cut off when the communication path is interrupted by the rotor, and the data transmission and transmission output are turned on when the communication path is not interrupted by the rotor.

【0035】

In this data transmission, the timing of securing the communication path changes due to continuous changes in the relative positional relationship between the helicopter and the satellite, changes in the attitude of the helicopter, etc., and control is performed according to this timing change, but the receiving side Then, it is difficult to detect the timing. Therefore, the transmission signal in the communication path securing time after the communication path cutoff time by the rotor is for burst communication including a signal for synchronization (preamble) in the header. As a result, the receiving side can also respond to the above-mentioned change in timing.

【0036】

On the other hand, regarding the helicopter reception system, it is difficult to control the transmission to the helicopter side on the ground side according to the timing of transmission from the helicopter side because the transmission line is long and the signal delay is large. It is also difficult to prevent reception on the helicopter side from blocking the communication path by the rotor of the helicopter. Therefore, the receiving unit of the helicopter in this embodiment adopts a normal space diversity receiving method, and is configured to select and receive an antenna in a good receiving state from a plurality of antennas.

【0037】

Since the incoming power, demodulation output, and the like are very small in the reception in this receiving unit, the withstand power is not required even if the switching of the antenna is controlled via the changeover switch. Therefore, even in a situation where switching is frequently performed, reliability can be ensured and high-speed switching can be easily performed. However, when receiving data that is fast and does not tolerate errors, the reception / demodulation system is configured so that the data can be demodulated, frame synchronization can be detected, and antenna switching control can be performed using the frames. There is a need.

【0038】

Next, the specific configuration and operation of the above-mentioned helicopter transmission / reception system will be described in detail.

【0039】

FIG. 4 is a block diagram showing a configuration of a helicopter transmission / reception device in the helicopter satellite communication system of the present invention. The transmitter / receiver is roughly divided into a transmitter 20, a receiver 30, a directional antenna 44a, 44b controlled by an antenna directional control device 40, a circulator 42a, 42b for transmitting and receiving these directional antennas 44a, 44b, and a transmitter. It consists of a changeover switch 41.

【0040】

The transmitter 20 includes an encoder 21, a modulation unit 22, a Ti control device 23, a switch 24, a mixer 25, a filter 26, an amplification unit 27, and a local oscillator 28, and has a configuration that operates as follows.

【0041】

The image data captured by the image pickup device mounted on the helicopter is input to the encoder 21, and the encoder 21 performs processing such as compression processing of the input image data, temporary storage, multiplexing with other data, and error control code addition. Is performed and incorporated into the required signal frame. The signal incorporated in the required signal frame by the encoder 21 is input to the modulation unit 22.

【0042】

The signal transmission timing from the encoder 21 is controlled by the Ti control device 23, whereby the encoder 21 sends out the transmission signal as a set (block) in frame units. At this time, a preamble (signal for synchronization) is added to the beginning of the block so that resynchronization is possible on the receiving side (see the signal format in FIG. 1).

【0043】

The Ti control device 23 takes in data such as the helicopter position, attitude / orientation, antenna pointing direction, and rotor rotation position (angle) via the helicopter signal control bus, and based on the data, the next Ti (start time, The end time) is calculated, and the Ti control signal 101 for controlling the frame configuration / blocking is output to the encoder 21 according to the calculated Ti.

【0044】

The signal input to the modulation unit 22 is subjected to the required modulation processing similar to the modulation processing in a known transmitter. The modulated signal becomes high frequency through the switch 24, the mixer 25 that mixes with the signal from the local oscillator 28, and the filter 26, is amplified by the amplification unit 27, and is sent to the transmission changeover switch 41.

【0045】

The encoder 21 outputs a synchronization signal 102 synchronized with the transmission block when the transmission signal is sent out as a set (block) for each frame. This synchronization signal 102 is input to each of the switch 24, the amplification unit 27, and the antenna directional control device 40 provided in the input stage of the mixer 25, whereby the switch 24, the amplification unit 27, and the antenna directional control device 40 are turned on. OFF control is performed.

【0046】

The output of the transmitter 20 (the output of the amplification unit 27) described above is input to the directional antennas 44a and 44b via the transmission changeover switch 41. The transmission changeover switch 41 is connected to the most suitable antenna side under the control of the antenna directivity control device 40, and the antenna is switched at the timing when the transmission signal is interrupted.

【0047】

The antenna directivity control device 40 takes in data such as the position, attitude / orientation, and satellite orbit of the helicopter through the helicopter signal bus 50, and together with data such as the antenna angle status, outputs a signal for controlling the directivity direction of each antenna. The output of the transmitter 20 is input to the optimum one of the directional antennas 44a and 44b in synchronization with the synchronization signal 102 from the encoder 21 while outputting to the drive units 43a and 43b of the directional antennas 44a and 44b. The transmission changeover switch 41 is controlled so as to be.

【0048】

The directional antennas 44a and 44b transmit and receive radio waves to the geostationary satellite 1 (or orbiting satellite 2), and are also directed in the required direction by the control of the antenna directional control device 40, and the directional antennas 44a and 44b are directed to the antenna directional control device 40. Output the angle status data.

【0049】

The circulators 42a and 42b send the output signal from the transmitter 20 described above to any of the directional antennas 44a and 44b, and also send the received signal from these directional antennas 44a and 44b to the receiver 30. In addition, the circulators 42a and 42b also function to attenuate the high power signal from the transmitter 20 so that it does not go directly to the receiver 30.

【0050】

The receiver 30 has a receiving system for each directional antenna. Here, the received signal from the directional antenna 44a is input to one input terminal of the changeover switch 37 via the amplification unit 31a, the mixer 32a, the filter 33a, the mixer 32b, and the amplification unit 31c, and is received from the directional antenna 44b. A signal is input to the other input terminal of the changeover switch 37 via the amplification unit 31b, the mixer 32c, the filter 33b, the mixer 32d, and the amplification unit 31d, and the comparison unit 36 compares the reception levels in the amplification units 31c and 31d. The input switching in the changeover switch 37 is controlled, and the output of the changeover switch 37 is input to the demodulation unit 27. In the receiver 30, the comparison unit 36 compares the reception levels of each reception system, and the comparison unit 36 switches the changeover switch 37 so as to demodulate the signal of a good reception system.

【0051】

The receiver 30 is controlled so that the receiving system is switched between frames of the demodulated signal when the received signal is high speed and error is not tolerated.

【0052】

In the transmitter / receiver configured as described above, when transmitting high-speed data such as images to the geostationary satellite 1 (or orbiting satellite 2), the antenna can be switched to the antenna on the non-obstructive side by the control of the antenna directional control device 40. At the same time, the transmitter 20 is controlled so that the data transmission and transmission output are cut off when the communication path is interrupted by the rotor, and the data transmission and transmission output are turned on when the communication path is not interrupted by the rotor. When the transmission data from this helicopter is received on the ground side via satellite, it is resynchronized using the preamble (signal for synchronization) added to the beginning of the blocks that make up each frame of the transmission signal. Is taken.

【0053】

When receiving the signal sent from the geostationary satellite 1 to the helicopter, the signal is received by the directional antennas 44a and 44b, and the received signal from the antenna in good reception is demodulated by the normal space diversity method. ..

【0054】

(Other Embodiments) When a short-range aerial relay device such as an aircraft or an airship is used instead of a satellite, the transmission power can be reduced to about several watts. In this case, in the transmission / reception device shown in FIG. 4 described above, hot switching can be applied to the transmission changeover switch 41, and the space diversity reception method can be adopted for the transmission system. Here, in the transmission / reception device shown in FIG. 4, a configuration in which the space diversity reception method is used in combination with the transmission system will be described.

【0055】

The amplification unit 27 of the transmitter 20 is configured to switch the transmission power to a small value, and the comparison unit 34 of the receiver 30 inputs information 104 regarding the antenna in a good reception state to the antenna directional control device 40 to input the antenna. The directional control device 40 has a control mode for switching to an antenna of a system with good reception. The encoder 21 has a function capable of configuring a signal frame or a set (block) thereof in units of the minimum duration (for example, ms order) of the transmission switching state suitable for transmission switching in the control mode, and a frame or block-to-block time. It has a function to make the switching time longer than the required time, and outputs this frame or inter-block signal to the antenna directional control device 40. The antenna directional control device 40 controls the switching timing in the transmission changeover switch 41 based on the signal (frame or block-to-block signal) input from the encoder 21.

【0056】

According to the configuration in which the space diversity reception method is used in combination with the transmission system of this embodiment, it is possible to configure a better transmission line by using the reception signal as a monitor signal of the transmission line in the helicopter.

【0057】

[Effect of the invention]

According to the present invention configured as described above, the timing at which the transmission signal is cut off is adjusted according to the change in the attitude / direction of the aircraft and the change in the antenna direction due to the change in the relative position between the helicopter and the satellite. Since the transmitted data is not lost, a good communication path can be secured, and there is an effect that a satellite communication system having higher communication quality than the conventional one can be constructed.

【0058】

In addition, antenna selection at the time of transmission is usually based on the relative position of the helicopter and the satellite and the attitude / orientation of the helicopter, and a system with good reception is compared with multiple reception systems such as space diversity reception. Since the control for switching to the antenna of the above is not performed, the operation of the transmission system to which a large power is applied can be simplified, the burden on the switching system and the like can be reduced, and the reliability of communication can be improved.

[Simple explanation of drawings]

[Figure 1]

It is a figure which shows the format of the transmission signal in the helicopter satellite communication system of one Embodiment of this invention, and the transmission timing thereof.

[Figure 2]

It is a figure which shows the intersection position of the antenna beam direction of a directional antenna and a rotor surface.

[Fig. 3]

It is a block diagram which shows the main structure of the transmission control signal generation system of a helicopter in the helicopter satellite communication system of this invention.

[Fig. 4]

It is a block diagram which shows the structure of the helicopter transmission / reception device in the helicopter satellite communication system of this invention.

[Fig. 5]

It is a conceptual diagram which shows the outline of a helicopter satellite communication system.

[Explanation of symbols]

1 Geostationary satellite 1a, 1b communication satellite 2 orbiting satellite 3 helicopter 4,5 Crossing position 6,7 directional antenna GT helicopter rotorcraft shielding time zone Ti helicopter rotorcraft shielding cycle