JP2005295094A - Mobile communication apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mobile communication apparatus capable of attaining efficient and sure communication in response to a change in an antenna scanning gain attended with a change in the position and the attitude of a mobile body such as an aircraft. <P>SOLUTION: The mobile communication apparatus is provided with: a modulation demodulation section mounted on the mobile body and applying modulation processing to a communication signal transmitted to a satellite to output a modulation signal; an antenna section for directing an antenna beam within a range at a prescribed angle from a direction of a normal of a transmission/reception face to transmit a modulation signal outputted from the modulation demodulation section; a beam direction detection section for detecting a direction of directing the antenna beam to the satellite on the basis of positional information and attitude information outputted from a state detection section for detecting the position and the attitude of the mobile body and controlling the directive direction of the antenna beam depending on the directive direction; and a transmission rate control section for switching the transmission rste in the modulation demodulation section in response to the directive direction of the antenna beam detected by the beam direction detection section. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a mobile communication device that communicates with another communication device via a communication satellite such as a geostationary satellite.

  In recent years, various satellite communication systems using communication satellites have been developed. For example, geostationary satellites that move in geostationary orbit appear to be stationary at all times when viewed from the ground, so there is an advantage that they can always communicate, such as satellite mobile communications such as Inmarsat, BS, CS Are used for satellite communication systems such as VSAT (Very Small Aperture Terminal). In such satellite communications, the signal-to-noise ratio, called the C / N ratio, decreases due to the attenuation of signals due to weather conditions such as rain or noise generated by the communication device itself.

  For example, when the C / N value of the transmission signal decreases due to such deterioration of the line condition, there is a method of increasing the transmission power and increasing the C / N value. However, the transmission power of the transmission signal is increased. Therefore, it is necessary to provide a high-power high-power amplifier, and although it is possible to reduce the signal reception error rate, the equipment scale becomes large and an extra cost is also required.

  On the other hand, the level of the beacon signal extracted from the received signal is detected, and the status of the communication satellite is determined by comparing the level signal with a preset threshold value. In such a case, it has been proposed to increase the C / N ratio by setting the transmission rate to a low speed. According to this method, for example, when the line condition deteriorates due to weather conditions such as rainfall, the C / N value can be increased without providing a high-power high-power amplifier or the like. Reliable communication can be performed.

  In addition, as antennas used for satellite communication and the like, there are rotating antennas such as parabona antennas and electronic scanning antennas such as phased array antennas. In a mobile communication device used in a mobile body such as a vehicle whose mounting space is limited, it can be reduced in weight and thickness, so that it is more like a phased array antenna than a rotary antenna such as a parabona antenna. It is desirable to use a simple electronic scanning antenna.

Japanese Patent Laid-Open No. 2000-252902 (page 2, column of conventional technology, column of problems to be solved by the invention, etc.)

  However, in the conventional mobile communication device, since the position and orientation of the mobile body change, when the electronic scanning antenna is used, the pointing direction of the antenna beam directed to the satellite is the position and orientation of the mobile body. In accordance with the change, there is a problem that the inclination is greatly tilted from the normal direction, and the scanning gain of the antenna beam and thus the C / N ratio of the transmission signal are greatly reduced.

  That is, in an electronic scanning antenna, the scanning gain tends to decrease as the antenna beam directivity direction tilts from the normal direction of the transmission / reception surface. When the antenna beam scanning gain decreases, the C / N value of the transmission signal is reduced. Also decreases. Therefore, when an electronic scanning antenna is used, even if the transmission rate is changed according to the line condition, it is difficult to perform reliable communication in a state where the scanning gain of the antenna beam is reduced.

  For example, in the case of a geostationary satellite, the satellite is moving in a geostationary orbit above the equator, so in high latitude areas such as Japan, the satellite is positioned in a low elevation direction, and the antenna beam is greatly increased from the normal direction. The tilt and scanning gain are also greatly reduced.

  In the case of an aircraft, etc., set operational restrictions, for example, a condition that communication continuation is not possible if the aircraft movement range or bank (tilt) etc. exceeds a predetermined angle, and within the scope of the operational restrictions. By setting a transmission rate (fixed) that enables reliable communication if there is, reliable communication is ensured regardless of changes in the position or attitude of the aircraft, etc. In this case, the transmission rate is fixed. For this reason, there is a problem that the transmission speed cannot be increased even in a flight posture in which the scanning gain is high, the margin of the communication line is increased, and efficient communication cannot be performed.

  The present invention has been made to solve the above-described problems, and is capable of performing efficient and reliable communication according to a change in antenna scanning gain without providing a high-power amplifier or the like. An object of the present invention is to obtain a simple mobile communication device.

  A mobile communication device according to the present invention includes a modem that is mounted on a mobile and outputs a modulated signal by performing a modulation process on a communication signal transmitted to a satellite, and an antenna within a predetermined angle range from the normal direction of the transmission surface. An antenna unit for directing a beam and transmitting a modulated signal output from the modulation / demodulation unit; a phase control unit for changing a direction of the antenna beam by giving a phase amount based on phase information to the antenna unit; A direction in which the antenna beam is directed to the satellite is detected from position information and posture information output from a state detection unit that detects the position and posture of the body, and phase information corresponding to the pointing direction is output to the phase control unit. And a transmission rate for switching the transmission rate in the modulation / demodulation unit according to the directivity direction of the antenna beam detected by the beam direction detection unit. It is obtained by a control unit.

  According to the present invention, since the transmission speed in the modulation / demodulation unit is switched in accordance with the change in the scanning gain of the antenna beam, the position and orientation of the moving body change, and the C / V of the transmission signal is changed in accordance with the change in the scanning gain of the antenna beam. Even if N changes, it is possible to select an optimum transmission rate according to the value of C / N, and it is possible to perform efficient and reliable communication via a communication satellite.

Embodiment 1 FIG.
Embodiment 1 of the present invention will be described below with reference to FIGS. FIG. 1 is a block diagram showing the configuration of the mobile communication device according to the first embodiment, FIG. 2 is a partial block diagram showing a specific configuration of the modem 5 shown in FIG. 1, and FIG. 3 is a mobile device 1 shown in FIG. It is a moving body schematic diagram which shows the example of the moving body which mounts. As shown in FIG. 1, the mobile communication device according to the first embodiment communicates with other communication devices 3 a and the like via a communication satellite 2. In FIG. 1, 1 is a mobile communication device mounted on a mobile body such as an aircraft or a vehicle, 2 is a communication satellite such as a geostationary satellite, orbiting satellite, 3a and 3b are other communication devices, and in FIG. An aircraft equipped with a mobile device 1. Note that the communication satellite 2 is not limited to a geostationary satellite moving on a geostationary orbit, but an orbiting satellite orbiting on a low altitude orbit, other quasi-zenith satellites, and the like can be used. The other communication devices 3a and 3b are not limited to mobile communication devices, but may be fixed communication devices using parabolic antennas or the like, and are intended for all communication devices configured to be capable of satellite communication. It is.

  In FIG. 1, 4 is a communication means for outputting a communication signal to be transmitted to a satellite such as an audio signal and a data signal, 5 is a modulation / demodulation unit such as a variable rate modem having a plurality of modulation / demodulation processing units, and 6 is a modulation / demodulation unit 5 An amplifying unit for amplifying the output modulation signal to a predetermined signal level and outputting the amplified signal, 7 is an electronic scanning antenna such as a phased array antenna, and the modulation signal output from the amplifying unit 6 is directed to the antenna beam. 8 is an antenna beam formed on a transmission / reception surface constituted by antenna elements of the antenna unit 7, and 9 is a phase for adjusting the phase amount of the antenna element to direct the antenna beam 8 in a predetermined direction. The control unit 10 is a state detection unit such as an inertial navigation device that detects the position, posture, and the like of the mobile body on which the mobile communication device 1 is mounted, and 11 is output from the state detection unit. A beam direction detecting unit that detects a direction in which the antenna beam 8 is directed to the communication satellite 2 from the position information and posture information of the moving object, and outputs phase information corresponding to the pointing direction to the phase control unit 9, and 12 is a beam direction detecting unit. 11 is a transmission rate control unit that switches the modulation processing unit provided in the modulation / demodulation unit 5 in accordance with the directivity direction of the antenna beam 8 detected from the signal 11.

  In FIG. 1, a state detection unit 10 for detecting the position, posture, etc. of the moving body is provided in the mobile communication device 1, but in the case of a large aircraft, the moving body such as an inertial navigation device is provided. In some cases, a means for detecting the position or the like is separately provided. In such a case, the position information and the posture information of the moving body may be acquired from the separately provided state detection unit, and the state detection is performed in the mobile communication apparatus 1. There is no need to provide a section. The beam direction detection unit 11 can detect the direction in which the antenna beam 8 is directed to the communication satellite 2 from the position information and posture information of the moving object output from such a separately provided state detection unit.

  In FIG. 2, 5a is a modulation / demodulation processing unit set to a high transmission rate, 5b is a modulation / demodulation processing unit set to a medium transmission rate, 5c is a modulation / demodulation processing unit set to a low transmission rate, and 5d. Is a selection means for selecting any modulation / demodulation processing unit from among the modulation / demodulation processing units 5a to 5c provided in the modulation / demodulation unit 5. In the first embodiment, a case in which three modulation / demodulation processing units are provided will be described. In the first embodiment, the selection unit 5d is used to select any one of the modulation / demodulation processing units from the plurality of modulation / demodulation processing units. However, one modulation / demodulation processing unit that can change the transmission rate is provided and intermittently provided. Or you may comprise so that a transmission rate may be switched continuously.

  Next, the operation will be described. The user of the mobile communication device 1 communicates with other communication devices 3a, 3b, etc. while moving by the mobile body 13 as shown in FIG. In FIG. 3, reference numeral 13 a denotes an antenna mounting position of the aircraft 13, and the antenna unit 7 of the mobile communication device 1 is disposed at an appropriate place according to the type and shape of the mobile body. In FIG. 3, the aircraft 13 is shown as an example of a mobile body on which the mobile body device 1 is mounted. However, even if the aircraft 13 is mounted on a vehicle such as an automobile, communication can be performed in the same manner.

  First, the communication unit 4 outputs a communication signal to be transmitted to the satellite such as an audio signal or a data signal. The modem 5 performs a predetermined modulation process on the communication signal output from the communication unit 4 and outputs a modulated signal. Specifically, the modulation / demodulation processing unit selected by the transmission rate control unit 12 among the plurality of modulation / demodulation processing units provided in advance modulates the communication signal and outputs the modulation signal. Each modulation / demodulation processing unit provided in the modulation / demodulation unit 5 has a different transmission rate, that is, a transmission rate, and the modulation / demodulation unit 5 outputs a modulation signal having a transmission rate corresponding to each modulation processing unit. The amplification unit 6 amplifies the modulation signal output from the modulation / demodulation unit 5 to a predetermined level and outputs the amplified signal to the antenna unit 7.

  The antenna unit 7 adjusts the phase amount of the antenna element by the phase control unit 9, forms an antenna beam 8 so as to be directed in the direction of the communication satellite 2, and uses the modulated signal amplified by the amplification unit 6 as a transmission signal. 2 to send. The phase control unit 9 adjusts the phase amount of the antenna element based on the phase information output from the beam direction detection unit 11. The beam direction detection unit 11 calculates a direction in which the antenna beam 8 is directed to the communication satellite 2 from the position information and posture information of the moving body detected by the state detection unit 10 and directs the antenna beam 8 in that direction. Is output to the phase controller 9. The state detection unit 10 is, for example, an inertial navigation system (INS) mounted on a mobile body, and the position of the mobile body on which the mobile communication device 1 is mounted by the state detection unit 10. Attitude (bank angle, pitch angle), speed, traveling direction, etc. are detected.

  In addition, in order to direct the antenna beam 8 toward the communication satellite 2, it is necessary to grasp not only the position information of the mobile body but also the position information of the communication satellite 2, but if the communication satellite 2 is a geostationary satellite, Since the position of the communication satellite 2 does not change, the beam direction detection unit 11 determines the antenna beam from the position information of the stationary satellite stored in the storage unit or the like in advance and the position information and attitude information of the moving body on which the mobile communication device 1 is mounted. The direction in which 8 is directed is detected. When the communication satellite 2 is an orbiting satellite or the like, the position of the communication satellite always changes, so the orbit information of the corresponding orbiting satellite is stored in advance in the storage unit, and the current position of the orbiting satellite and the mobile object The direction in which the antenna beam 8 is directed is detected from the position information and posture information of the moving body on which the communication device 1 is mounted.

  Finally, the operation of the transmission rate control unit 12 will be described in detail with reference to FIG. FIG. 4 is a data table showing the relationship between the directivity direction of the antenna beam 8 and its scanning gain, and shows an example of a conversion table provided in the storage means (not shown) of the transmission rate control unit 12, for example. It is conversion table explanatory drawing. In FIG. 4, 0 ° is the normal direction of the transmitting / receiving surface of the antenna unit 7, the horizontal axis is the inclination (beam angle) of the antenna beam 8 from the normal direction, and the vertical axis is the beam angle of the antenna beam 8, that is, the antenna. The scanning gain of the antenna unit 7 with respect to the directing direction of the beam 8 is shown. As shown in FIG. 4, the scanning gain decreases as the antenna beam 8 tilts from the normal direction. Note that Ra is a scanning gain when the directivity direction of the antenna beam 8 is 45 °, Rb is a scanning gain when the directivity direction of the antenna beam 8 is around 60 °, and Rc is a directivity direction of the antenna beam 8 near 70 °. The scanning gain in the case.

  The transmission rate control unit 12 obtains the scanning gain of the antenna unit 7 from the directivity direction of the antenna beam 8 detected by the beam direction detection unit 11 and the conversion table as shown in FIG. 4, and a selection signal corresponding to the scanning gain. Thus, the switching means 5d of the modem unit 5 is switched. For example, a high-speed modulation / demodulation processing unit 5A is selected when the scanning gain is Ra or higher, a medium-speed modulation / demodulation processing unit 5B is selected between Ra and Rb, and a low-speed modulation / demodulation processing unit 5C is selected between Rb and Rc. Thus, the switching means 5d of the modem unit 5 is controlled. In this manner, the modulation / demodulation processing unit that performs modulation processing on the communication signal is switched by the transmission rate control unit 12, and the communication signal that is modulated by the switched modulation / demodulation processing unit is output to the amplification unit 6 as the modulation signal. When the scanning gain is Rc or less, it is difficult to continue communication, and it may be displayed on a display unit (not shown) that communication continuation is difficult.

  For example, when the position or posture of the mobile body on which the mobile communication device 1 is mounted changes and the pointing direction of the antenna beam 8 is changed to another direction, the beam direction detection unit 11 receives the position information from the state detection unit 10 and Based on the attitude information, a direction in which the antenna beam 8 is directed toward the communication satellite 2 is detected, and information on the direction of the antenna beam is output to the transmission rate control unit 12. The transmission rate control unit 12 transmits the antenna beam 8 in the direction detected by the beam direction detection unit 11 from the information on the directivity direction of the antenna beam output from the beam direction detection unit 11 and the conversion table stored in advance in the storage unit. The switching gain 5d of the modulation / demodulation unit 5 is switched so as to perform modulation / demodulation processing of the communication signal by the modulation / demodulation processing unit having a transmission rate corresponding to the scanning gain. When the modulation / demodulation processing unit is switched by the switching unit 5d, the modulation / demodulation unit 5 performs modulation processing on the communication signal output from the communication unit 4 by the modulation / demodulation processing unit after switching, and outputs a modulation signal.

  As described above, in the mobile communication device according to the first embodiment, when the position or posture of the mobile body on which the mobile communication device 1 is mounted changes and the pointing direction of the antenna beam 8 is changed to another direction, The beam direction detector 11 detects the direction in which the antenna beam is directed to the communication satellite 2, and the antenna beam 8 is directed in the direction detected by the beam direction detector 11 from the information and the conversion table stored in advance. Since the scanning gain is obtained and the modulation / demodulation processing unit of the modulation / demodulation unit 5 is switched so that the modulation / demodulation processing of the communication signal is performed by the modulation / demodulation processing unit of the transmission rate according to the scanning gain, the position and orientation of the moving body changes, and the antenna beam Even if the C / N of the transmission signal changes in accordance with the change in the scanning gain, the optimum transmission rate can be selected in accordance with the value of C / N. It is possible to perform efficient and reliable communication.

Embodiment 2. FIG.
The second embodiment of the present invention will be described below. In the first embodiment, the case where the communication satellite 2 is a geostationary satellite has been described as an example. However, in a high latitude region such as Japan, the geostationary satellite is located in the low elevation angle direction, so the transmission / reception surface of the antenna unit 7 is parallel to the ground When the antenna beam 8 is disposed at the position, the directivity direction of the antenna beam 8 is substantially the low elevation angle direction. In general, the higher the C / N, the higher the transmission speed. Therefore, when an electronic scanning antenna is used, it is desirable to transmit the transmission signal to the communication satellite by directing the antenna beam in the normal direction of the transmission / reception surface. . In the second embodiment, a mobile communication apparatus in which the antenna beam directing direction is substantially the normal direction of the transmission / reception surface will be described.

  Specifically, a quasi-zenith satellite that moves near the zenith direction in Japan is used as the communication satellite 2. The quasi-zenith satellite system is a satellite system in which at least one communication satellite composed of a plurality of communication satellites is always located near the zenith direction in Japan, and the communication satellite 2 that transmits a transmission signal is almost true. Since it is located above, the antenna beam 8 can be directed substantially in the normal direction of the transmission / reception surface of the antenna unit 8 by arranging the transmission / reception surface of the antenna unit 7 in parallel with the ground.

  FIG. 5 is a comparative explanatory diagram comparing the directivity directions of the antenna beams 8 when the quasi-zenith satellite is the communication satellite 2 and when the stationary satellite is the communication satellite 2 in the satellite system as shown in FIG. It is. In FIG. 5, 7b is a transmission / reception surface of the antenna unit 7, 8a is an antenna beam formed in the normal direction of the transmission / reception surface 7b, and 8j is an antenna formed in the lowest elevation angle direction when the quasi-zenith satellite is the communication satellite 2. A beam 8s is an antenna beam formed in the lowest elevation direction when the geostationary satellite is the communication satellite 2.

  As shown in FIG. 5, when the quasi-zenith satellite is the communication satellite 2, the lowest elevation angle is a high elevation angle, and therefore a high transmission rate is set among the plurality of modulation / demodulation processing units provided in the modulation / demodulation unit 5. Modulation processing can be performed by the modulation / demodulation processing unit, and high-speed transmission of communication signals can be realized. In addition, since the posture (bank angle, pitch angle) of the moving body can be increased, it is possible to provide a margin for operation restrictions of the moving body. In the second embodiment, the so-called quasi-zenith satellite has been described when the mobile communication device according to the present invention is used in the country and its surrounding areas. However, the same applies to the case where the mobile communication apparatus is used in an overseas area. Even when applied to a satellite system using a communication satellite similar to the quasi-zenith satellite moving in the vicinity of the zenith direction of the area where the mobile communication device 1 as shown in FIG.

1 is a block diagram showing a configuration of a mobile communication device according to Embodiment 1. FIG. It is a partial block diagram which shows the specific structure of the modem part 6 shown in FIG. It is a mobile body schematic diagram which shows the example of the mobile body which mounts the mobile body apparatus 1 shown in FIG. It is conversion table explanatory drawing which shows the example of the data table which shows the relationship between the directivity direction of the antenna beam 8 shown in FIG. 1, and a scanning gain. It is explanatory drawing of the mobile communication apparatus 1 by Embodiment 2, Comprising: When the quasi-zenith satellite was used as the communication satellite 2, the directivity direction of each antenna beam 8 with the case where the geostationary satellite was used as the communication satellite 2 was compared It is comparative explanatory drawing.

Explanation of symbols

1 mobile communication device, 2 communication satellite, 3 other communication device, 4 communication means,
5 modulation / demodulation unit, 5a modulation / demodulation processing unit A, 5b modulation / demodulation processing unit B,
5c modulation / demodulation processing unit C, 6 amplification unit, 7 antenna unit, 7b transmission / reception surface,
8 antenna beam, 9 phase controller, 10 state detector, 11 beam direction detector,
12 Transmission rate control unit, 13 Mobile.

Claims (4)

A modulation / demodulation unit mounted on a mobile unit that modulates a communication signal transmitted to a satellite and outputs the modulation signal; and directs an antenna beam within a predetermined angle range from the normal direction of the transmission surface and outputs from the modulation / demodulation unit An antenna section for transmitting the modulated signal, a phase control section for changing the directivity direction of the antenna beam by giving a phase amount based on the phase information to the antenna section, and a state detection for detecting the position and posture of the moving body A beam direction detection unit that detects a direction in which the antenna beam is directed to the satellite from the position information and attitude information output from the unit, and outputs phase information corresponding to the pointing direction to the phase control unit, and the beam direction A transmission rate control unit that switches a transmission rate in the modulation / demodulation unit according to a directivity direction of the antenna beam detected by the detection unit; Body communication device. 2. The mobile communication apparatus according to claim 1, wherein the modulation / demodulation unit is a variable rate modem having a plurality of modulation / demodulation processing units. 2. The mobile communication according to claim 1, wherein the transmission rate control unit switches the transmission rate in the modulation / demodulation unit based on a conversion table for converting a directivity direction of the antenna beam into a scanning gain of the antenna unit. apparatus. The mobile communication device according to claim 1, wherein the satellite is a quasi-zenith satellite that moves in the vicinity of the zenith direction in Japan.

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