JP2014099755A - Earth station device and method for controlling earth station device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the amount of interference to an adjacent communication satellite in an earth station device communicating with a communication satellite by operating a plurality of antennas in cooperation, even when the earth station device uses an antenna having so small an opening diameter that an adjacent communication satellite exists in the main beam.SOLUTION: The earth station device is provided with means for adjusting a plurality of antennas to a prescribed antenna interval corresponding to the opening diameter and the number of transmission signal frequencies, and thereby having the zero point of the composite radiation pattern of the plurality of antennas matched to the direction of a communication satellite adjacent to a communication satellite with which communicating. Furthermore, the earth station device is provided with means which, when the plurality of antennas have an error regarding the prescribed antenna interval, performs phase compensation suitable for the error regarding the prescribed antenna interval on transmitted signals from the plurality of antennas, and thereby causes the zero point of the composite radiation pattern of the plurality of antennas to match with the direction of the adjacent communication satellite.

Description

  The present invention provides a plurality of transmission / reception devices having low communication capability (EIRP: product of antenna gain and transmission power, G / T: ratio of antenna gain G and noise temperature T obtained by temperature conversion of noise figure) in satellite communication. The present invention relates to an earth station apparatus and an earth station apparatus control method for a satellite communication system that improve communication capability by appropriately operating them together and enable transmission / reception of wideband and large-capacity transmission signals.

  In a satellite communication system, when it is required to transmit a broadband / large-capacity signal such as a base station to which a plurality of users are connected or a user station that desires transmission / reception of rich content, etc. Requires an earth station device with high communication capability (EIRP, G / T).

  In order to transmit a predetermined signal in a conventional satellite communication system, EIRP and G / T corresponding to the circuit design are required. The required EIRP increases in proportion to the communication capacity when the modulation method is fixed. In addition, multi-value processing can improve the number of transmission bits per 1 Hz and reduce the frequency, but more EIRP is required. Also, assuming the same signal transmission, EIRP and G / T between earth stations that communicate with each other have a complementary relationship.

  An improvement in EIRP requires either an increase in antenna gain or an increase in transmission power, or both. In order to improve the antenna gain, it is necessary to increase the aperture area of the antenna. On the other hand, the increase in transmission output has a limit although the maximum output power is improved year by year. Furthermore, with regard to an increase in transmission output, power durability is required for the components constituting the transmitter. On the other hand, in order to improve G / T, it is necessary to improve the antenna gain, reduce the noise of the receiver, or both. The antenna gain is as described above, and the current situation is that no further noise reduction can be expected for the receiver noise reduction. For the above reasons, in order to improve the communication performance of the earth station, both the transmitter and the receiver need to be significantly modified.

Thus, as a technique for flexibly improving the communication performance of the earth station, as described in Non-Patent Document 1, an approach for improving communication performance using a plurality of antennas has been reported. In this technique, as shown in FIG. 7 (a), the modulation signal output from the modulator 71 is distributed into a plurality of signals according to the number of antennas by the signal distributor 72, and the satellite station antenna on the receiving side by the phase setting unit 73. The communication performance is improved by controlling the phase so as to be in-phase in the direction and inputting it to the transmitter 74, transmitting from a plurality of antennas, and spatially synthesizing. Further, as shown in FIG. 7 (b), the return signals from the communication satellites are received by the receiver 76 from a plurality of antennas, and synthesized by adjusting the amplitude and phase by the amplitude / phase setting unit 77 and the signal synthesizer 78. Control that maximizes the S / N is performed and input to the demodulator 79. According to this technique, assuming that the communication performance of the transceiver is the same, EIRP is N ² times and G / T is N times the number of antennas N.

Suzuki et al., “Study on Fixed Station Application of Distributed Array Antenna System”, IEICE, Satellite Communication Society, SAT2011-36, pp.111-116 Kikuma, Adaptive Antenna Technology, Ohm, 2003

  The earth station apparatus shown in FIG. 7 realizes a predetermined gain by operating a plurality (N) of small antennas in cooperation. Since the antenna gain is proportional to the aperture area, the aperture diameters of the N small antennas are 1 / √N when the same gain is obtained with a single antenna, and the antenna pattern during in-phase synthesis is the antenna pattern of each small antenna. Is multiplied by the array factor.

  FIG. 8 shows the analysis value of the radiation pattern of the single antenna. FIG. 8 (1) is an approximation of a first-order Bessel function as an analysis value of a radiation pattern of an antenna having an aperture diameter of 75 cm. FIG. 8 (2) shows the analysis value of the radiation pattern of an antenna having an aperture diameter of 54 cm. The gain of an antenna with an aperture diameter of 75 cm is equivalent to the gain when two antennas with an aperture diameter of 54 cm are used. When both are compared, it can be confirmed that the larger the aperture diameter, the smaller the beam width (the angle at which the power is halved).

  Since general communication satellites are arranged at geochronous intervals of 2 degrees on a geostationary orbit about 36,000km above the equator, in order to communicate without interfering with other adjacent communication satellites, communication satellites are correct. Need to be oriented. In the radiation pattern of the antenna having an aperture diameter of 75 cm shown in FIG. 8 (1), a communication satellite (an angle of separation of 2 degrees) adjacent to the edge portion of the main beam is located, and the relative gain with respect to the peak gain is −30 dB or less (FIG. 8). It can be confirmed that there is almost no interference. On the other hand, in the antenna radiation pattern shown in Fig. 8 (2), the relative gain at an angle of 2 degrees from the front of the main beam is -10.8 dB (arrow in Fig. 8 (2)), and adjacent communication satellites. It can be said that it is a value that can not be ignored as interference with. That is, with an antenna having a small aperture diameter, an adjacent communication satellite is located in the main beam, which causes interference.

  If the antenna aperture diameter of the antenna is further reduced, the beam width is further expanded. Therefore, when a predetermined gain is realized by using a plurality of antennas having a small aperture diameter as described in Non-Patent Document 1, there is a problem that the possibility of an increase in the amount of interference with adjacent communication satellites is increased.

  An example of controlling the amplitude and phase of an array antenna used in wireless communication or the like so as to form a zero point so as not to cause interference has been reported. However, since the distance between the array antennas is fixed, there is a problem that the gain of the main beam may be reduced when the null is formed.

  The present invention uses a small-aperture antenna in which there is an adjacent communication satellite in the main beam in a satellite communication system in which a plurality of antennas of the earth station device operate in cooperation with each other to communicate with a communication satellite. It is an object of the present invention to provide an earth station apparatus and an earth station control apparatus control method that can reduce the amount of interference with adjacent communication satellites even when the earth station is connected.

  In a first aspect of the present invention, in an earth station device that performs communication with a communication satellite by operating a plurality of antennas in a coordinated manner, the plurality of antennas are adjusted to a predetermined antenna interval according to an aperture diameter and a transmission signal frequency, and communication is performed. Means are provided for matching the zero points of the combined radiation patterns of the plurality of antennas in the direction of the communication satellite adjacent to the communication satellite as the counterpart.

  In the earth station device of the first invention, when a plurality of antennas have an error with respect to a predetermined antenna interval, phase compensation is performed on transmission signals from the plurality of antennas according to the error with respect to the predetermined antenna interval, Means are provided for matching the zero points of the combined radiation pattern of the plurality of antennas in the direction of the adjacent communication satellite. Further, there is provided means for applying an arrival wave direction estimation algorithm, estimating an antenna interval from a known direction of an adjacent communication satellite, and calculating an error with respect to a predetermined antenna interval.

  According to a second aspect of the present invention, there is provided an earth station apparatus control method for performing communication with a communication satellite by operating a plurality of antennas in a coordinated manner, and adjusting the plurality of antennas to a predetermined antenna interval according to an aperture diameter and a transmission signal frequency. And a processing step of matching the zero points of the combined radiation patterns of the plurality of antennas in the direction of the communication satellite adjacent to the communication satellite which is the communication partner.

  In the earth station apparatus control method according to the second invention, when a plurality of antennas have an error with respect to a predetermined antenna interval, phase compensation according to the error with respect to the predetermined antenna interval is performed on transmission signals from the plurality of antennas. And a processing step of matching the zero points of the combined radiation patterns of the plurality of antennas in the direction of the adjacent communication satellite. In addition, there is a processing step of applying an arrival wave direction estimation algorithm, estimating an antenna interval from a known direction of an adjacent communication satellite, and calculating an error with respect to a predetermined antenna interval.

  The earth station apparatus of the present invention can form a zero point in the main beam by adjusting the antenna interval appropriately even when using a plurality of small antennas where adjacent communication satellites exist in the main beam. The amount of interference with the communication satellite can be reduced. Furthermore, even when some error occurs with respect to the predetermined antenna interval, by performing phase compensation according to the error with respect to the predetermined antenna interval for the transmission signal of each antenna, a zero point is formed with a slight gain reduction, The amount of interference with adjacent communication satellites can be reduced.

  Therefore, a signal can be transmitted with a higher EIRP by applying the present invention to the limitation of transmission EIRP in which the amount of interference with adjacent communication satellites is the main factor.

It is a figure which shows the Example structure of the earth station apparatus of this invention. It is a figure which shows the array factor and synthetic | combination radiation pattern of 2 antennas (30 wavelength intervals, the same phase). It is a figure which shows the array factor and synthetic | combination radiation pattern of 2 antennas (43 wavelength intervals, the same phase). It is a figure which shows the synthetic | combination radiation pattern of 2 antennas (40 wavelength intervals, the same phase). It is a figure which shows the synthetic | combination radiation pattern of 2 antennas (40 wavelength space | interval, phase difference 25 degree | times). It is a flowchart which shows the example of a process sequence of the earth station apparatus control method of this invention. It is a figure which shows the structural example of the earth station apparatus using a some antenna. It is a figure which shows the analysis value of the radiation pattern of a single antenna.

  FIG. 1 shows an embodiment of the earth station apparatus according to the present invention. In this embodiment, an antenna for suppressing interference to a communication satellite adjacent to a communication satellite that is a communication partner in an earth station apparatus that performs communication with a communication satellite by operating a plurality of antennas having a small aperture diameter. The arrangement and control method is shown.

  In FIG. 1, the modulated signal output from the modulator 11 is distributed into a plurality according to the number of antennas by the signal distributor 12, and the phase control unit 13 generates the same phase or a predetermined phase difference in the direction of the satellite station antenna on the receiving side. The phase is controlled so as to be input to the transmitter 14 and transmitted from a plurality of antennas 15. The return signal from the communication satellite of the signal transmitted by the local station is received by the receiver 16 via the plurality of antennas 15 and is synthesized by adjusting the amplitude and phase by the amplitude / phase setting unit 17 and the signal synthesizer 18. Control is performed to maximize / N and the result is input to the demodulator 19.

  A feature of the present invention is that a plurality of antennas 15 are installed so as to have a predetermined antenna interval that reduces the amount of interference with adjacent communication satellites, and the antenna interval is measured or measured using the antenna interval estimation unit 20. The antenna interval is estimated, the phase difference calculated according to the error with respect to the predetermined antenna interval is set in the phase control unit 13, and the phase compensation of the signal transmitted from each antenna 15 is performed.

  Here, the antenna spacing of the plurality of antennas 15 is determined such that the amount of interference with adjacent communication satellites is small according to the aperture diameter and the transmission signal frequency. For example, when the transmission signal frequency is 14.25 GHz (wavelength is 2.10 cm) and two antennas with an aperture diameter of 54 cm (25.7 wavelengths) are arranged so as not to overlap, the amount of interference with adjacent communication satellites depends on the antenna spacing. It changes as follows.

  2 (1) and 2 (2) show the analysis values of the array factor and the combined radiation pattern of two antennas (30 wavelength intervals, in-phase). When the antenna interval of an antenna having an aperture diameter of 54 cm is 30 wavelengths, the array factor at 2 degrees corresponding to the position of the adjacent communication satellite is almost 0 dB, and the gain reduction from the peak is 10.8 dB in the combined radiation pattern as well. Become. This is equivalent to the case where an antenna having an aperture diameter of 54 cm shown in FIG. 8 (2) is used alone.

  3 (1) and 3 (2) show the analysis values of the array factor and the combined radiation pattern of two antennas (43 wavelength intervals, in-phase). When the antenna interval of an antenna with an aperture diameter of 54 cm is 43 wavelengths, the array factor at 2 degrees is -50 dB or less, and the gain reduction from the peak is 60 dB even in the combined radiation pattern, giving almost interference to adjacent communication satellites. It can be confirmed that there is not.

  FIG. 4 shows an analysis value of a combined radiation pattern of two antennas (40 wavelength intervals, in-phase). When the antenna interval of an antenna having an aperture diameter of 54 cm is 40 wavelengths, the gain reduction from the peak is 20 dB in the combined radiation pattern at 2 degrees. That is, when the antenna interval is 40 wavelengths, the amount of interference is better than that of the 30 wavelengths shown in FIG. 2 (2), but is deteriorated compared to the case of the antenna interval 43 wavelengths shown in FIG. 3 (2). Thus, the amount of interference changes due to the change of the array factor according to the error with respect to the predetermined antenna interval, and there is an optimum value of the antenna interval (43 wavelengths in the above example).

  Therefore, in order to secure the gain equivalent to an antenna with an aperture diameter of 75 cm by using two antennas with an aperture diameter of 54 cm and to reduce interference with adjacent communication satellites, the antenna is used when the transmission signal frequency is 14.25 GHz. It is desirable to set the interval to 43 wavelengths (90.5 cm). However, if the error is 3 wavelengths (6.3 cm) or less as shown in FIG. 4 with respect to the original 43-wavelength of the antenna, adjust the phase difference between the transmission signals of the two antennas as shown below. Thus, it is possible to reduce interference with adjacent communication satellites.

  Here, when the phase amount for forming the zero point is controlled in the direction of the adjacent communication satellite and a phase difference of 25 degrees is given to the transmission signals of the two antennas, the relative gain at 2 degrees is as shown in FIG. It can be improved to -30 dB or less. Since the peak gain at this time can be slightly degraded by about 0.25 dB due to the influence of the phase error of 25 degrees, even if there is a slight error (about 3 wavelengths) with respect to a predetermined antenna interval at the time of antenna installation, phase adjustment can be performed. Can respond. That is, in the above example, even if the antenna interval is not strictly set to 43 wavelengths, it is possible to suppress the interference by electrical processing such as phase adjustment of the transmission signal within the allowable error range. It is. Furthermore, the degree of freedom of adjustment can be increased by adjusting the amplitude.

  In the present invention, the antenna interval is important for suppressing interference. As a method other than actually measuring the antenna interval, an arrival wave estimation algorithm such as the MUSIC algorithm described in Non-Patent Document 2 can be applied. The antenna interval estimation unit 20 shown in FIG. 1 is configured to use this method. The arrival wave direction estimation algorithm originally estimates the direction of the arrival wave in a state where the antenna configuration (antenna interval) is known. However, since the antenna interval estimation unit 20 knows the direction of the adjacent satellite, The interval is given as an unknown, and the antenna interval is estimated so that the result of the arrival wave direction estimation algorithm matches the direction of the adjacent satellite. By estimating the antenna interval in this way, it is possible to feed back to the phase difference determination for adjusting the antenna interval or forming the zero point.

FIG. 6 shows a processing procedure example of the earth station controller control method of the present invention.
In FIG. 6, steps S <b> 1 to S <b> 4 show a procedure for installing antennas so that a predetermined antenna interval at which the amount of interference with adjacent communication satellites becomes small. Steps S5 to S8 show a procedure for performing phase compensation of signals transmitted from the respective antennas in accordance with an error with respect to a predetermined antenna interval.

  First, antennas are installed so as to have a predetermined antenna interval (S1), and the antenna interval is actually measured, or signals are transmitted to and received from a communication satellite (S2), and an arrival direction estimation algorithm is applied. The antenna interval is estimated (S3). The antenna interval is adjusted until the error with respect to the predetermined antenna interval at this time is within an allowable value (S4, S1).

  Next, in accordance with an error with respect to a predetermined antenna interval, a phase difference to be added to a phase amount to be controlled for zero point formation in the adjacent communication satellite direction is calculated (S5). After that, the phase of the transmission signal is controlled so that the reception level of the satellite return signal of the local station is maximized so that the transmission signal from the antenna is in phase (S6, S7), and then calculated in step S5. A phase difference corresponding to an error with respect to a predetermined antenna interval is given (S8). As a result, it is possible to simultaneously suppress the amount of interference while forming the main beam.

DESCRIPTION OF SYMBOLS 11 Modulator 12 Signal distributor 13 Phase control part 14 Transmitter 15 Antenna 16 Receiver 17 Amplitude / phase setting part 18 Signal synthesizer 19 Demodulator 20 Antenna interval estimation part 81 Modulator 82 Signal distributor 83 Phase setting part 84 Transmission Machine 86 Receiver 87 Amplitude / phase setting section 88 Signal synthesizer 89 Demodulator

Claims (6)

In an earth station device that communicates with a communication satellite by operating multiple antennas in cooperation,
Means for adjusting the plurality of antennas to a predetermined antenna interval according to the aperture diameter and the transmission signal frequency so that the zeros of the combined radiation patterns of the plurality of antennas coincide with the direction of the communication satellite adjacent to the communication satellite as the communication partner An earth station device characterized by comprising: The earth station device according to claim 1,
When the plurality of antennas have an error with respect to the predetermined antenna interval, phase compensation is performed on the transmission signals from the plurality of antennas according to the error with respect to the predetermined antenna interval, and the direction of the adjacent communication satellite And means for matching the zero points of the combined radiation patterns of the plurality of antennas. The earth station device according to claim 2,
An earth station apparatus comprising: means for applying an arrival wave direction estimation algorithm, estimating the antenna interval from a known direction of the adjacent communication satellite, and calculating an error with respect to the predetermined antenna interval. In the earth station device control method for communicating with a communication satellite by operating a plurality of antennas in cooperation,
A process of adjusting the plurality of antennas to a predetermined antenna interval according to an aperture diameter and a transmission signal frequency, and matching zero points of a combined radiation pattern of the plurality of antennas in a direction of a communication satellite adjacent to a communication satellite as a communication partner An earth station apparatus control method comprising: steps. In the earth station apparatus control method according to claim 4,
When the plurality of antennas have an error with respect to the predetermined antenna interval, phase compensation is performed on the transmission signals from the plurality of antennas according to the error with respect to the predetermined antenna interval, and the direction of the adjacent communication satellite And a processing step of matching zero points of the combined radiation patterns of the plurality of antennas. In the earth station apparatus control method according to claim 5,
An earth station apparatus control method comprising a processing step of applying an arrival wave direction estimation algorithm, estimating the antenna interval from a known direction of the adjacent communication satellite, and calculating an error with respect to the predetermined antenna interval .

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