JP4955738B2 - Helicopter-mounted communication device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a communication device mounted on a helicopter that improves continuity of communication by performing diversity reception of a transmitted wave transmitted from a ground station through a communication satellite by switching a plurality of antennas. <P>SOLUTION: A time diversity signal is transmitted to the helicopter from the ground station through the communication satellite, and received by a first antenna 6 or second antenna 7. A switching control circuit 10 estimates a rotation blocking mode wherein a reception beam is cut off by rotary blades and a structure blocking mode caused by presence of a rotary blade or a cockpit in a direction of the reception beam. When the structure blocking mode is caused, the switching timing of the antennas is determined based upon a frame timing signal from a modem device 14 and a blocking timing made by the rotary blade, and a switching control signal is output to the antenna switching circuit 13. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a helicopter-mounted communication device that is mounted on a helicopter and receives a signal transmitted from a ground station via a communication satellite.

  When communication is performed between a helicopter-equipped communication device and a ground station via a communication satellite, when the helicopter-equipped communication device is placed below the rotor blade, the communication between the communication satellite and the helicopter-equipped communication device As the helicopter rotor blade crosses the propagation path, the communication is interrupted. In the transmission from the ground station to the helicopter-equipped communication device, the ground station cannot predict the timing of communication interruption by the rotor blades, so the same information is transmitted to the ground so that it can be demodulated even if there is an interruption. A time diversity method is used in which a station transmits a plurality of times and a helicopter-mounted communication device synthesizes the received signal. Patent Document 1 shows an example of communication by a conventional time diversity method. The helicopter-equipped communication device described in Patent Document 1 receives a transmission wave by a time diversity method transmitted from a ground station via a communication satellite, and the timing at which the received beam is blocked by a rotor blade, The reception level is monitored and estimated, and the amplitude level of the reception signal at the estimated cutoff timing is corrected to zero. After this processing, time diversity combining is performed to eliminate uncertain noise signals in the received signal caused by the received beam being blocked by the rotor blades, and to take measures with a good C / N ratio. It is.

JP 2004-235845 A

  In order for the communication described in Patent Document 1 to be established, it is assumed that the helicopter-mounted communication device is capable of receiving by time diversity reception, although the receiving beam is blocked by the rotor blades. Here, the antenna unit of the communication device mounted on the helicopter may be disposed around the main body cockpit, for example, on both sides of the cockpit (lower part of the rotor blade) from the viewpoint of structural stability of the helicopter, In this case, a receiving beam blocking mode by the rotor blade (hereinafter referred to as “rotary blade blocking mode”) occurs, and a receiving beam blocking mode by the cockpit or rotating blade rotating shaft (hereinafter “structure blocking mode”). Will be generated). In order to avoid this structure blocking mode, for example, by providing one antenna on each side of the cockpit part, when the structure blocking mode occurs during reception with one antenna, the structure A multi-antenna switching reception method is used in which reception is continued by switching to another antenna that does not have an object blocking mode, but the received signal for a fixed time is demodulated due to the phase discontinuity of the received signal before and after antenna switching. Can not do it. When performing time diversity reception using such a multi-antenna switching reception method, the received signal is demodulated and reproduced even if the received signal is lost due to the rotor blade cutoff mode and the received signal is lost due to antenna switching. Whether the discontinuity of information can be suppressed has become a problem.

  The present invention has been made to solve the above-described problems. A transmission wave transmitted from a ground station via a communication satellite is received by switching a plurality of antennas to receive time diversity, thereby improving communication continuity. The purpose is to obtain a helicopter-equipped communication device that can do this.

  A helicopter-mounted communication device according to a first aspect of the present invention is a helicopter-mounted communication device that is mounted on a helicopter and communicates with a ground station via a communication satellite, and is transmitted from the ground station via the communication satellite. First and second antennas for receiving the incoming time diversity signal, an antenna switching circuit for switching the first and second antennas to output the received signal, and modulation / demodulation for demodulating the received signal by combining the time diversity And a cutoff timing at which the received beam of the first antenna is blocked by the rotor blade of the helicopter, and a structure blocking mode is generated in the received beam of the first antenna at the time of reception by the first antenna. In the state where it is determined that the structure blocking mode occurs and the structure blocking estimation determination is performed to determine whether or not to A switching timing determination is performed to determine the switching timing from one antenna to the second antenna based on the frame timing signal of the demodulated signal demodulated by the modem and the cutoff timing, and the antenna switching circuit receives the switching timing determination. A switching control circuit for generating a switching control signal for instructing switching from the first antenna to the second antenna.

  A helicopter-mounted communication device according to a second aspect of the present invention is the helicopter-mounted communication device according to the first aspect of the present invention, wherein the switching control circuit is arranged in the frame of data having the last ordinal number of the repetition of the time diversity signal. When a single antenna is blocked by the rotor blades, it is determined that the start point of the cutoff is the switching timing from the first antenna to the second antenna.

  A helicopter-mounted communication device according to a third aspect of the present invention is the helicopter-mounted communication device according to the first aspect of the present invention, wherein the switching control circuit is a data frame having an ordinal number one last before the repetition of the time diversity signal. In this case, when the first antenna is blocked by the rotor blades, it is determined that the start point of the blocking is the switching timing from the first antenna to the second antenna.

  According to the present invention, the structure demodulator estimation determination for determining whether or not the structure blocking mode occurs is performed, and in the state in which it is determined that the structure blocking mode is generated, the modulation / demodulator Since the switching timing determination is performed based on the frame timing signal of the demodulated signal and the blocking timing by the rotor blade, data loss can be suppressed and communication continuity can be improved.

It is a block diagram which shows the whole apparatus regarding the helicopter satellite communication which concerns on Embodiment 1 of this invention. It is an external view showing an example of the mounting state of the antenna part of the helicopter mounting communication apparatus concerning Embodiment 1 of this invention. It is a block diagram which shows the structure of the communication apparatus mounted in helicopter concerning Embodiment 1 of this invention. It is a signal timing chart in the helicopter mounting communication apparatus concerning Embodiment 1 of this invention.

  Embodiment 1

  A helicopter-mounted communication device according to Embodiment 1 of the present invention will be described with reference to FIGS. FIG. 1 is a block diagram showing the entire apparatus related to helicopter satellite communication according to Embodiment 1 of the present invention, and FIG. 2 shows an example of the mounting state of the antenna portion of the helicopter-mounted communication apparatus according to Embodiment 1 of the present invention. FIG. 3 is a block diagram showing a configuration of the helicopter-mounted communication device according to Embodiment 1 of the present invention. In FIG. 1, 1 is a helicopter, 2 is a ground station, 3 is a communication satellite, and a transmission line 4 from the ground station 2 to the helicopter 1 is provided via the communication satellite 3. In the helicopter 1, 5 is a rotor blade, 6 is a first antenna provided on the right side of the cockpit of the helicopter 1, and 7 is a second antenna provided on the left side of the cockpit of the helicopter 1.

  In the example shown in FIG. 2, the first antenna 6 and the second antenna 7 are mounted on the horizontal plate by attaching a horizontal plate from the upper structure of the cockpit toward both sides, and the swirling of the rotor blade 5 is performed. The face is up. For example, if the communication satellite 3 is a geostationary satellite that is almost just south of Japan on a geostationary orbit over the equator, the elevation angle at which the communication satellite 3 is viewed from Japan is about 48 degrees. When the helicopter 1 flies over Japan with the nose in the north-south direction, the received beams of the first antenna 6 and the second antenna 7 are in the nose direction where the communication satellite 3 is viewed or at an elevation angle of about 48 degrees behind the fuselage. The received beam is not interrupted by the cockpit or the rotating shaft of the rotor blade, and the transmitted wave transmitted from the ground station 3 via the communication satellite 3 is received by one of the antennas. Can continue. On the other hand, when the helicopter 1 flies over Japan with the nose in the east-west direction, one of the reception beams of the first antenna 6 and the second antenna 7 is directed in the direction in which the center line of the helicopter exists. The received beam is blocked by the cockpit or the rotating blade rotating shaft. Since the other receiving beam is irradiated in the direction opposite to the direction in which the fuselage center line exists, the cockpit and the rotating shaft of the rotor blade are not blocked. As for antenna switching, for example, when a helicopter flying with the south direction as the nose direction is receiving a transmission wave transmitted from the ground station 3 via the communication satellite 3 by the first antenna 6 (rotation) If the nose direction is turned to the west direction while the nose wing blocking mode is occurring), the direction of the received beam of the first antenna 6 (the direction of the communication satellite 3) is changed from the certain turning angle to the cockpit or rotary shaft of the rotor blade. In order to continue reception, switching from the first antenna 6 to the second antenna 7 is necessary, for example, starting to shut off (in addition to the rotor blade shutoff mode, the structure shutoff mode also starts to occur). Such a structure blocking mode appears more conspicuously when the antenna elevation angle (the elevation angle based on the antenna fixing portion) is lowered by changing the posture of the helicopter by roll rotation.

  Next, the configuration of the helicopter-mounted communication device will be described with reference to FIG. 8 is a position / direction sensor that measures the position and direction of the helicopter (including roll, pitch, and yaw postures) by GPS, gyro, etc., and 9 is a rotor timing sensor that detects the rotor at a specific position. is there. 10 calculates the direction in which the antenna should face (reception beam direction) based on the position and direction information from the position / direction sensor 8 and the satellite position, and outputs an antenna direction command. The timing signal from the rotor blade timing sensor 9 is received. This is a switching control circuit that performs antenna switching control based on the beam direction and the demodulated monitor signal. 11 is a first satellite tracking circuit that drives the first antenna 6 based on an antenna direction command from the switching control circuit 10, and 12 is a second satellite tracking that drives the second antenna 7 based on an antenna direction command from the switching control circuit 10. Circuit. The first satellite tracking circuit 11 and the second satellite tracking circuit 12 independently perform antenna tracking control. Reference numeral 13 denotes an antenna switching circuit that switches and outputs reception signals from the first antenna 6 and the second antenna 7 based on a switching control signal from the switching control circuit 10, and reference numeral 14 demodulates the received signal by combining time diversity. Then, it is a modem that monitors the frame structure of the demodulated signal and outputs the frame timing signal to the switching control circuit 10.

  Next, time diversity reception and antenna switching operation by the helicopter-equipped communication device will be described with reference to FIG. FIG. 4 is a signal timing chart in the helicopter-mounted communication apparatus according to Embodiment 1 of the present invention. FIG. 4A shows an example in which demodulated data becomes discontinuous, and FIG. 4B shows a case where switching control is performed in consideration of demodulated data according to the present invention. 4A and 4B, stage A is the data structure of the time diversity signal sent from the ground station 2 via the communication satellite 3, and stage B is the first antenna by the rotor 5. 6, the stage C represents the timing for switching the reception from the first antenna 6 to the second antenna 7, and the stage D represents the timing for shutting off the second antenna 7 by the rotor 5. In the case of the transmission signal in the time diversity system, the same data is transmitted a plurality of times, but in the case of FIGS. 4A and 4B, an example in which the same data is transmitted four times is shown. That is, the data a1 to a4 represent the same data a, and similarly b1 to b4, c1 to c4, and d1 to d4 represent the same data b, c, and d, respectively. Further, it is assumed that the data a1 to d4 are stored for each frame as a data delimiter. 4A and 4B, the signal timings of the A stage, the B stage, and the C stage are the same, but the antenna switching timings of the C stage are different.

  For example, if each frame length is 4096 bits at a transmission rate of 256 kbps, the time length of one frame is 16 ms. If the rotational speed of the four rotor blades is about 5 Hz, one period in which the rotor blades block the received beam of the antenna is 50 ms. In this case, the rotor blades are interrupted approximately every three frames. Further, although it depends on the width of the receiving beam, the distance of the receiving beam from the rotor blade center on the rotating blade swivel surface, and the width of the rotor blade, the cutoff period in FIGS. 4 (a) and 4 (b) is One frame is assumed, and data for two frames is lost in antenna switching. Furthermore, the antenna switching is determined to be several tens to several hundred times longer than the frame time length (for example, the above 16 ms) if the time for the helicopter to turn 90 degrees in the nose direction is about several seconds. It can be done during the time.

  With reference to FIG. 4 (a), it will be described that switching that causes data loss occurs when antenna switching is performed at an arbitrary position in the data structure of the time diversity signal. First, it is assumed that the antenna switching circuit 13 is connected to the modem 14 with the received signal from the first antenna 6 and can receive data a3 and a4 that arrive during the receivable period with reference to stage B. However, a1, a2, and b1 overlap the cutoff period and are missing. As the helicopter turns, switching from the first antenna 6 to the second antenna 7 is necessary, and it is assumed that the antenna switching is performed immediately after arrival of the head portion of the data b1 in the received signal. Since antenna switching is performed at an arbitrary position, this means that antenna switching may occur at such timing. Since it is assumed that two frames of data are lost in antenna switching, reception of data b1, b2, and b3 is lost. If the interruption period of the second antenna 7 occurs simultaneously with the start of reception by the second antenna 7 as shown in the D stage of FIG. 4A, the data b3 and b4 are also missing. Thereafter, the data c and d received within the receivable period in the second antenna 7 are received, but the data b1, b2, b3, and b4 are all missing, so the data b is missing and the communication Discontinuity / discontinuity occurs.

  The antenna switching according to the present invention shown in FIG. In the switching control circuit 10, in real time, the direction (received beam direction) that the antenna should face is calculated based on the position and direction information from the position / direction sensor 8 and the satellite position, and the structure is blocked by the rotating blade rotating shaft or cockpit. The structure blocking judgment is performed by estimating whether the mode will occur in the near future. For example, the direction of the received beam after a predetermined several hundred ms is extrapolated from the current and past received beam directions to determine whether or not the structure blocking mode occurs. As a result of this estimation determination, if it is determined that the structure blocking mode occurs, it is necessary to switch the antenna. From the time of reception of a1 shown in stage A of FIG. 4B, the switching control circuit 10 determines where the switching timing is to be set in the state where the structure blocking mode is determined by the structure blocking estimation determination described above. The switching timing is determined based on the frame timing signal of the demodulated signal by the modem 14. The frame timing signal indicates a frame delimiter position, and also indicates the number of repeated positions (referred to as “data ordinal number”) of data sent a plurality of times. For example, in the example shown in FIG. 4, such a frame timing signal can be represented by a 2-bit signal. When data a1 is received, 00 is received. When data a2 is received, 01, data a3 is received. It is possible to take various signal forms such as 10 when the data is received and 11 when the data a4 is received. For the data ordinal, the modem 13 determines the start position of the new data (data ordinal 1) by looking at the change in the data value after demodulation, and the known repetition number and frame length negotiated in the communication system. It is also possible to detect the data by specifying the ordinal number 2 or later of the data or inserting a frame synchronization word between the frames.

  In FIG. 4B, the switching control circuit 10 determines whether or not the interruption shown in the B stage occurs in the frame of data having the last ordinal number of repetition based on the frame timing signal. The start of the instantaneous interruption is set as the antenna switching timing, and a switching control signal is generated and output to the antenna switching circuit 13. Based on this switching control signal, the antenna switching circuit 13 switches from the first antenna 6 to the second antenna 7 and outputs the received signal to the modem 14. Data b4, c1, c2, and c3 are lost due to the communication interruption for two frames of antenna switching and the instantaneous interruption of the received beam at the second antenna 7 after switching, but the data b is received data b1 (Part in b1), b2 (part in b2), b3 and b4 (part in b4) can be demodulated by time diversity combining, and data c is received by c3 (in c3) Part) and c4 can be demodulated by time diversity combining. Note that data b and c can be received even if data partially missing is discarded and time diversity synthesis is performed.

  Further, the switching control circuit 10 determines whether or not the interruption shown in the B stage occurs in the data frame having the last ordinal number of the last repetition based on the frame timing signal. It is also possible to output the switching control signal to the antenna switching circuit 13 with the momentary disconnection start time as the antenna switching timing. Specifically, the data c3 shown in the A stage in FIG. 4B is the data immediately before the last ordinal number, and as shown in the B stage, the instantaneous interruption of the received beam at the first antenna 6 during this reception. Will occur. When the antenna is switched at the start of the instantaneous interruption that occurs during reception of the data c3, the data c3, c4, Although d1 and d2 are missing, data c can be demodulated by time diversity combining with received data c1 (part of c1), c2 and c3 (part of c3), and data d Then, time diversity combining is performed by receiving d3 and d4, and demodulation is possible.

  As described above, in the switching control circuit 10, the structure blocking estimation determination is performed to determine whether the structure blocking mode will occur in the near future. By performing switching timing determination that determines where the switching timing is based on the frame timing signal of the demodulated signal by the modem 14 and the occurrence of interruption by the rotor blades, data loss is suppressed and communication continuity is improved can do.

DESCRIPTION OF SYMBOLS 1 Helicopter 2 Ground station 3 Communication satellite 5 Rotor blade 6 1st antenna 7 2nd antenna 10 Switching control circuit 13 Antenna switching circuit 14 Modem

Claims (3)

In a helicopter-mounted communication device mounted on a helicopter and communicating with a ground station via a communication satellite, first and second receiving time diversity signals sent from the ground station via the communication satellite The antenna, an antenna switching circuit for switching the first and second antennas to output a received signal, a modem for demodulating the received signal by time diversity combining, and a received beam of the first antenna Estimating the shutoff timing shut off by the helicopter rotor blades, and performing a structure shutoff estimation judgment to determine whether or not a structure shutoff mode occurs in the received beam of the first antenna at the time of reception by the first antenna In the state where it is determined that the structure blocking mode occurs, the switching type from the first antenna to the second antenna is set. Switching timing determination is performed based on the frame timing signal of the demodulated signal demodulated by the modem and the cutoff timing, and the antenna switching circuit is connected to the second antenna from the first antenna to the second antenna. A helicopter-equipped communication device comprising a switching control circuit that generates a switching control signal for instructing switching. In the data frame having the last ordinal number of the repetition of the time diversity signal, the switching control circuit is configured to determine a cutoff start time from the first antenna when the first antenna is blocked by the rotor blades. The helicopter-equipped communication device according to claim 1, wherein it is determined that it is a switching timing to the second antenna. In the frame of data having the ordinal number of the last one before the repetition of the time diversity signal, the switching control circuit determines the cutoff start time when the first antenna is blocked by the rotor blades. The helicopter-mounted communication device according to claim 1, wherein it is determined that it is a switching timing from one antenna to the second antenna.

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