JP2016111605A - Array antenna device and array antenna control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an array antenna device capable of reducing suppression caused by a grating lobe, and an array antenna control method.SOLUTION: A plurality of antennas 101-1 to 101-N are disposed at such positions that a path difference in a desired direction and a path difference in a suppression direction are related to be longer than wavelengths of information signals. A plurality of delay circuits 102-1 to 102-N delay a plurality of branched and inputted information signals. An information signal beamforming calculation circuit 103 controls delay amounts of the plurality of delay circuits 102-1 to 102-N.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an array antenna device and an array antenna control method.

  Since satellite communication has a wide service area and strong characteristics in disasters, it is widely used in offshore and digital divide areas where terrestrial links are difficult to use, and in the construction of communication environments during disasters. However, when relaying and communicating with geostationary satellites at an altitude of 36,000 km, the propagation loss is very large. 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, in order to realize this, communication performance (EIRP) : Equivalent Isotropic Radiated Power, G / T: Earth station equipment with high gain to noise temperature ratio)) is required.

  As a technique for realizing such an earth station device at a low cost, as described in Non-Patent Document 1, introduction of an array antenna composed of a plurality of transmission / reception devices is being studied. FIG. 9 shows the basic configuration of such an array antenna. As shown in FIG. 9, a plurality of antennas 501-1 to 501-N (N is an integer) are arranged to constitute an array antenna. Transmission / reception devices 502-1 to 502-N are provided for the antennas 501-1 to 501-N, respectively. At the time of transmission, the information signal is modulated by the modem 503. A signal from the modem 503 is supplied to the transmission / reception devices 502-1 to 502-N via the phase control device 504, and a transmission signal is radiated from the antennas 501-1 to 501-N.

  At the time of reception, the reception signals of the antennas 501-1 to 501-N are supplied to the transmission / reception devices 502-1 to 502-N. Output signals of the transmission / reception devices 502-1 to 502-N are supplied to the modulation / demodulation device 503 via the phase control device 504. The modem 503 demodulates the information signal from the received signal.

  In such an array antenna, the phase control device 504 controls the phase of the carrier wave and performs beam forming of the carrier wave. That is, the phase of the carrier wave signal to be transmitted is controlled by the phase control device 504 so that the carrier wave signals from the plurality of antennas 501-1 to 501-N are in phase during transmission. At the time of reception, the phase of the received carrier signal is controlled by the phase control device 504 so that the received signal is subjected to maximum ratio combining (or in-phase combining). Thereby, improvement of EIRP and G / T can be aimed at.

Suzuki, Susaki, Hirose, Kobayashi, “Study on application of fixed array antenna to fixed station” IEICE Tech. Reports, SAT2011-36, Aug 2011.

  In the antennas 501-1 to 501-N constituting the array antenna as described above, the opening diameter is at least 60 cm. For this reason, the distance between the antennas needs to be physically 60 cm or more. On the other hand, the Ku band (12 to 18 GHz) used for satellite communication has a wavelength of about 20 mm. Thus, when the antenna interval is large with respect to the wavelength, interference called a grating lobe occurs.

  FIG. 10 is a diagram illustrating generation of grating lobes. In FIG. 10, the horizontal axis indicates the azimuth angle, and the vertical axis indicates the transmission power. The grating lobe is an interference paper with the same energy as the main lobe. The grating lobe can be masked to some extent by the antenna pattern of a single directional antenna used. However, as shown in FIG. 10, even if the gain in the main direction is increased by using the directional antenna, the grating lobe rises from the antenna pattern of the single antenna by the same amount as the gain in the main direction, and the side lobe direction. Will cause unnecessary interference.

  In view of the above problems, an object of the present invention is to provide an array antenna apparatus and an array antenna control method that can reduce suppression due to grating lobes.

  In order to solve the above-described problem, an array antenna apparatus according to an aspect of the present invention branches an information signal into a plurality of paths, modulates a carrier wave with the branched information signal, and transmits the modulated signal with a plurality of antennas. A plurality of antennas arranged at positions where the relationship between the path difference in the desired direction and the path difference in the suppression direction cannot be ignored with respect to the wavelength of the information signal; A plurality of delay circuits that respectively delay the inputted information signals, and an information signal beamforming arithmetic circuit that controls delay amounts of the plurality of delay circuits.

  Also, the present invention is characterized in that the information signal beamforming arithmetic circuit controls the delay amount of each of the delay circuits so that the information signal is synchronized in the desired direction.

  Also, the present invention is characterized in that the information signal beamforming arithmetic circuit controls the delay amount of each of the delay circuits using the estimated delay profile.

  Also, the present invention is characterized in that the delay circuit delays the information signals branched and input by delaying the carrier wave modulated by the information signal.

  The array antenna control method according to one aspect of the present invention includes a plurality of antennas arranged at positions where the relationship between the path difference in the desired direction and the path difference in the suppression direction cannot be ignored with respect to the wavelength of the information signal. An array antenna control method performed by an array antenna apparatus, wherein the information signal is branched into a plurality of paths, a carrier wave is modulated with the branched information signal, and transmitted by the plurality of antennas. And a delay step for delaying the inputted information signals, and an information signal beam forming calculation step for controlling the delay amounts of the plurality of delay circuits.

  According to the present invention, it is possible to reduce the suppression due to the grating lobe in the array antenna.

It is a block diagram which shows the structure of the array antenna apparatus which shows the 1st Embodiment of this invention. It is explanatory drawing of the interference by a grating lobe in the 1st Embodiment of this invention. It is explanatory drawing of the beam forming of an information signal. It is a functional block diagram of the calculating part in the 1st Embodiment of this invention. It is a flowchart which shows the process of arrangement | positioning control of the array antenna in the 1st Embodiment of this invention. It is a graph which shows the average EIRP pattern in the 1st Embodiment of this invention. It is a block diagram which shows the structure of the array antenna apparatus which shows the 2nd Embodiment of this invention. It is a block diagram which shows the structure of the array antenna apparatus which shows the 3rd Embodiment of this invention. It is a block diagram which shows the basic composition of an array antenna. It is a graph which shows generation | occurrence | production of a grating lobe.

<First Embodiment>
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a configuration of an array antenna apparatus showing a first embodiment of the present invention.

  In FIG. 1, antennas 101-1, 101-2, ..., 101-N (N is an integer) constitute an array antenna. The antennas 101-1 to 101-N are arranged at positions where the relationship between the path difference in the desired direction and the path difference in the suppression direction is longer than the wavelength of the information signal. The arrangement of the antennas 101-1 to 101-N will be described in detail later. The antennas 101-1 to 101-N communicate with geostationary satellites using, for example, a Ku band (12 to 18 GHz) carrier wave. As the antennas 101-1 to 101 -N, for example, those having an opening diameter of 60 cm or more can be used.

  The delay circuits 102-1, 102-2,..., 102-N delay each information signal that is branched and input into a plurality of paths. Each delay amount of the delay circuits 102-1 to 102-N is set by the information signal beamforming arithmetic circuit 103. The delay circuits 102-1 to 102-N and the information signal beamforming arithmetic circuit 103 perform beamforming of the information signal. In this example, the information signal beamforming arithmetic circuit 103 controls the delay amount of each of the delay circuits 102-1, 102-2,..., 102-N so that the phase of the information signal is synchronized in a desired direction.

  .., 104-N modulates the carrier wave from the carrier wave generation circuit 105 with the information signals passed through the delay circuits 102-1, 102-2,..., 102-N. . The carrier wave from the carrier wave generation circuit 105 is, for example, in the Ku band (12 to 18 GHz).

  The carrier phase shift circuits 106-1, 106-2, ..., 106-N shift the phase of the carrier signal from the modulation circuits 104-1, 104-2, ..., 104-N. The phase shift amounts of the carrier phase shift circuits 106-1, 106-2,..., 106-N are set by the carrier beam forming arithmetic circuit 107. The carrier phase shift circuits 106-1 to 106-N and the carrier beam forming arithmetic circuit 107 perform carrier beam forming. In this example, the carrier beamforming arithmetic circuit 107 controls the phase shift amount of each of the carrier phase shift circuits 106-1, 106-2,..., 106-N so that the phase of the carrier wave is synchronized in a desired direction. .

  The calculation unit 108 calculates the positions of the antennas 101-1, 101-2, ..., 101-N. The computing unit 108 can be configured using a personal computer or the like. Further, an external computer system may be used as the calculation unit 108.

  Thus, in the first embodiment of the present invention, the antennas 101-1 to 101-N are arranged at positions where the relationship between the path difference in the desired direction and the path difference in the suppression direction is longer than the wavelength of the information signal. The Also, delay circuits 102-1 to 102-N for performing beam forming of information signals and an information signal beam forming arithmetic circuit 103 are provided. Further, carrier wave phase shift circuits 106-1 to 106-N for performing beam forming of the carrier wave signal and a carrier beam forming arithmetic circuit 107 are provided. Thereby, unnecessary interference due to the grating lobe can be reduced.

  FIG. 2 is an explanatory diagram of interference due to grating lobes in the first embodiment of the present invention. As described above, in the first embodiment of the present invention, the antennas 101-1 to 101-N constitute an array antenna. In the following description, the carrier frequency is fb and the frequency of the information signal is fbb. The antennas 101-1 to 101-N perform communication with geostationary satellites and have a large aperture diameter (about 60 cm or more). The carrier frequency fb is the Ku band and is 12 to 18 GHz. The frequency fbb of the information signal is assumed to be several kHz to MHz. The direction of the main lobe from each antenna 101-1 to 101-N toward the stationary satellite for communication is referred to as a desired direction, and the direction from each antenna 101-1 to 101-N toward the side lobe is referred to as an interference direction. Shall. In FIG. 2, an arrow A1 indicates a desired direction, and an arrow A2 indicates an interference direction.

  In FIG. 2, two antennas, antenna 101-1 and antenna 101-K (K is an arbitrary integer) constituting the array antenna, are shown. From the antenna 101-1, a main lobe signal S11 is radiated in a desired direction A1. Further, side lobe signal S12 is radiated from antenna 101-1 in the interference direction A2. From the antenna 101-K, a main lobe signal S21 is radiated in a desired direction A1. Further, a sidelobe signal S22 is radiated from the antenna 101-K toward the interference direction A2.

  While the carrier frequency is on the order of GHz, the frequency of the information signal is kHz to MHz, and the wavelength of the information signal is 1000 times longer than the wavelength of the carrier signal. In a general array antenna, the distance between the antennas is close to about a half interval of the wavelength of the carrier wave. As described above, when the antenna is disposed close to the length shorter than the wavelength, the interference wave of the information signal can be ignored. On the other hand, if the distance between the antennas is increased by 1/4 to 1/2 wavelength difference or more with respect to the wavelength, the interference of the information signal cannot be ignored. Therefore, intersymbol interference occurs due to the path length difference.

  The signal waveform changes in the signals S11 and S12, S21, and S22 in FIG. 2 schematically show changes in the information signal. In FIG. 2, the main lobe signal S21 radiated from the antenna 101-K is interfered by the side lobe signal S12 from the antenna 101-1 in the portion Q10. Here, if the beam forming of the information signal is performed so that the signal S21 and the signal S12 are in phase, the average power in the desired direction A1 increases. On the other hand, in the directions other than the desired direction A1, the interference components become uncorrelated with each other and are averaged. Therefore, in the case of two antennas, by performing beam forming of the information signal, the power in the interference direction can be suppressed up to 3 [dB] in comparison with the power in the main lobe direction when the average power is viewed.

FIG. 3 is an explanatory diagram of beamforming of information signals. As described above, the main lobe signal S21 from the antenna 101-K is interfered by the side lobe signal S12 from the antenna 101-1 in the portion Q10. In the part Q10, the side lobe signal S12 from the antenna 101-1 is different from the main lobe signal S21 from the antenna 101-K in the desired direction and in the suppression direction | D1-D2 | Only the difference in path length occurs. Since the orbit position of the geostationary satellite is known in advance, the angles of the desired direction A1 and the interference direction A2 are uniquely determined. The angle of desired direction A1 is (elevation angle θ ₁ , azimuth angle φ ₁ ), the angle of interference direction A2 is (elevation angle θ ₂ , azimuth angle φ ₂ ), and the position of antenna 101-1 is (0, 0, 0). _Assuming that the position of the antenna 101-K is (d _xK , d _yK , d _zK ), the path difference D1 in the desired direction and the path difference D2 in the suppression direction are expressed by the following equations.

The wavelength λbb of the information signal is λbb = c / fbb (c is the speed of light) when the symbol rate of the baseband signal that is the information signal is fbb. Therefore, (| D1-D2 |> = c / fbb) position satisfying the relation of _{(d xK, d yK, d} zK) by arranging the antenna 101-K in the suppression direction path difference in the desired direction The relationship of the path difference | D1-D2 | is longer than the wavelength of the information signal.

  As shown in FIG. 1, in this embodiment, delay circuits 102-1 to 102-N and an information signal beamforming arithmetic circuit 103 that perform beamforming of information signals are provided. The information signal beamforming arithmetic circuit 103 controls the values of the delay circuits 102-1 to 102-N so that the information signals are synchronized in the desired direction A1. As a result, when the average power is viewed, it is possible to suppress the power in the interference direction by up to 3 [dB] compared to the power in the main lobe direction.

When the interference suppression value may be 3 [dB] or less, the interference suppression value Y [dB] is set to Y = 10 · log ₁₀ [1 {| D1-D2 | fbb / c} +0.5 {| c / fbb−D1 + D2 | fbb / c}] [dB]
The position of the antenna K (d _xK , d _yK , d _zK ) may be arranged so as to satisfy the above.

  Also, if the antenna spacing cannot be as designed (it cannot be physically separated by the above procedure), the amount of delay achieved is shifted from the optimum value to suppress the grating lobe at the expense of the main beam gain. May be. At this time, beam forming of the information signal is performed so that the suppression amount becomes a desired interference suppression value Y [dB]. The amount of beam forming may be given the following delay amount D_delay in the suppression direction.

Y = 10 · log ₁₀ [1 {| X−D2 | fbb / c} +0.5 {| c / fbb−X + D2 | fbb / c}]
X = (2 · 10 (Y / 10) −1) c / fbb + D2
D_delay = X / c

  At that time, the main beam is attenuated by the following amount.

10 · log ₁₀ [1 {(X−D1) fbb / c} +0.5 {(c / fbb−X + D1) fbb / c}]

FIG. 4 is a functional block diagram of the calculation unit 108 for determining the position of the antenna. In FIG. 4, a direction determining unit 51 determines a desired direction and an interference direction. The route calculation unit 52 calculates the route length difference | D1−D2 | by the equations (1) and (2). The antenna position calculation unit 53 calculates the wavelength λbb of the information signal as (λbb = c / fbb) and obtains a position (d _xK , d _yK , d) such that (| D1-D2 |> = c / fbb). _zK ), the position of the antenna 101-K is calculated.

  FIG. 5 is a flowchart showing processing of array antenna arrangement control according to the first embodiment of the present invention. In FIG. 5, a desired direction, an interference direction, and an interference suppression value are input to the calculation unit 108 (step ST1). When the desired direction, interference direction, and interference suppression value are input, operation unit 108 determines the position of the antenna (step ST2). That is, the calculation unit 108 calculates the path length difference | D1-D2 | based on the above-described formulas (1) and (2) so that the path length difference | D1-D2 | becomes longer than the wavelength of the information signal. The position of the antenna is determined so as to satisfy the following relationship (step ST2).

  Next, the information signal beamforming arithmetic circuit 103 estimates the delay amount of the information signal in the desired direction at the determined antenna position (step ST3). Then, the information signal beamforming arithmetic circuit 103 determines whether or not the interference suppression value has been achieved to the desired value (step ST4). If the interference suppression value has not been achieved to the desired value, the information signal beamforming calculation circuit 103 controls the delay amount and information Signal beam forming is performed (step ST5). By repeating step ST3 to step ST5, the interference suppression value approaches the desired value. When the desired interference suppression value is achieved in step ST4, the information signal beamforming arithmetic circuit 103 sets a delay value in the delay circuits 102-1 to 102-N (step ST6).

  Next, the carrier beam forming arithmetic circuit 107 sets the phase shift amount of the carrier phase shift circuits 106-1 to 106-N. That is, the carrier beam forming arithmetic circuit 107 determines the phase control amount of the carrier signal so that the carrier signals from the plurality of antennas 101-1 to 101-N are in phase (step ST7).

  FIG. 6 shows an average EIRP pattern in the first embodiment of the present invention when the desired direction is 40 degrees. In FIG. 6, the horizontal axis indicates the directivity direction, and the vertical axis indicates the gain. From the characteristics of FIG. 6, it can be seen that the average power in the other direction is suppressed while maintaining a gain of 40 degrees in the desired direction. In this way, unnecessary interference due to grating lobes can be achieved by placing the antenna at a position where the relationship between the path difference in the desired direction and the path difference in the suppression direction is longer than the wavelength of the information signal, and performing beam forming of the information signal. Can be reduced.

  In the above example, since the communication with the geostationary satellite is performed, the desired direction and the interference direction are known, but the desired direction and the interference direction may be detected by estimating the arrival direction.

<Second Embodiment>
FIG. 7 is a block diagram showing a second embodiment of the present invention. As shown in FIG. 7, in the second embodiment of the present invention, the antennas 201-1 to 201-N constitute an array antenna, and the antennas 101-1 to 101-N in the first embodiment are the same as those in the first embodiment. Similarly, it is arranged at a position where the relationship between the path difference in the desired direction and the path difference in the suppression direction is longer than the wavelength of the information signal. The calculation unit 208 calculates the positions of the antennas 201-1 to 201-N. Delay circuits 202-1 to 202-N, information signal beam forming arithmetic circuit 203, modulation circuits 204-1 to 204-N, carrier wave generating circuit 205, carrier wave phase shifting circuits 206-1 to 206-N, carrier beam beam forming arithmetic circuit Reference numeral 207 denotes the delay circuits 102-1 to 102-N, the information signal beamforming arithmetic circuit 103, the modulation circuits 104-1 to 104-N, the carrier wave generation circuit 105, and the carrier phase shift circuit 106- of the first embodiment. 1 to 106-N and the same configuration as the carrier beam forming arithmetic circuit 107.

  In the present embodiment, a delay profile estimation unit 209 is further provided. The delay profile estimation unit 209 estimates a delay profile from the received signal. The information signal beamforming arithmetic circuit 203 sets the delay amount of the delay circuits 202-1 to 202-N using the delay profile estimated by the delay profile estimation unit 209. About another structure, it is the same as that of the above-mentioned 1st Embodiment.

<Third Embodiment>
FIG. 8 is a block diagram showing a third embodiment of the present invention. As shown in FIG. 8, in the third embodiment of the present invention, the antennas 301-1 to 301-N constitute an array antenna, and the antennas 101-1 to 101-N of the first embodiment described above. In the same manner as described above, the path difference in the desired direction and the path difference in the suppression direction are arranged so as to be longer than the wavelength of the information signal. The calculation unit 308 calculates the positions of the antennas 301-1 to 301-N. The modulation circuits 304-1 to 304-N, the carrier generation circuit 305, the carrier phase shift circuits 306-1 to 306-N, and the carrier beam forming arithmetic circuit 307 are the modulation circuits 104-1 to 104-104 of the first embodiment described above. -N, carrier wave generation circuit 105, carrier wave phase shift circuits 106-1 to 106-N, and carrier beam forming arithmetic circuit 107.

  In the present embodiment, delay circuits 302-1 to 302-N are provided after the modulation circuits 304-1 to 304-N. As the delay circuits 302-1 to 302-N, variable delay lines that delay the carrier wave by analog processing can be used. The delay amount of the delay circuits 302-1 to 302-N is set by the information signal beamforming arithmetic circuit 303. In the present embodiment, the delay circuits 302-1 to 302-N perform processing equivalent to that obtained by delaying and modulating the information signal by adding a delay to the carrier wave modulated by the information signal. In the present embodiment, beam forming of an information signal can be performed by analog processing. About another structure, it is the same as that of the above-mentioned 1st Embodiment.

  As described above, the plurality of antennas are arranged at positions where the relationship between the path difference in the desired direction and the path difference in the suppression direction is longer than the wavelength of the information signal. In addition, a delay circuit for performing beam forming of the information signal and an information signal beam forming arithmetic circuit are provided. Thereby, unnecessary interference due to the grating lobe can be reduced.

  Each unit is recorded by recording a program for realizing all or part of the functions of the array antenna apparatus on a computer-readable recording medium, causing the computer system to read and execute the program recorded on the recording medium. You may perform the process of. Here, the “computer system” includes an OS and hardware such as peripheral devices. Further, the “computer system” includes a homepage providing environment (or display environment) if a WWW system is used. The “computer-readable recording medium” refers to a storage device such as a flexible medium, a magneto-optical disk, a portable medium such as a ROM and a CD-ROM, and a hard disk incorporated in a computer system. Furthermore, the “computer-readable recording medium” dynamically holds a program for a short time like a communication line when transmitting a program via a network such as the Internet or a communication line such as a telephone line. In this case, a volatile memory in a computer system serving as a server or a client in that case, and a program that holds a program for a certain period of time are also included. The program may be a program for realizing a part of the functions described above, and may be a program capable of realizing the functions described above in combination with a program already recorded in a computer system.

  The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and includes design changes and the like without departing from the gist of the present invention.

101-1 to 101-N: antennas 102-1 to 102-N: delay circuit 103: information signal beamforming arithmetic circuits 104-1 to 104-N: modulation circuit 105: carrier wave generation circuits 106-1 to 106-N: Carrier phase shift circuit 107: Carrier beam forming calculation circuit 108: Calculation unit

Claims (5)

An array antenna apparatus for branching an information signal into a plurality of paths, modulating a carrier wave with the branched information signal, and transmitting with a plurality of antennas,
A plurality of antennas arranged at positions where the relationship between the path difference in the desired direction and the path difference in the suppression direction cannot be ignored with respect to the wavelength of the information signal;
A plurality of delay circuits that respectively delay the information signals branched and input;
An information signal beam forming arithmetic circuit for controlling a delay amount of the plurality of delay circuits;
An array antenna apparatus comprising:   The array antenna apparatus according to claim 1, wherein the information signal beamforming arithmetic circuit controls each delay amount of the delay circuit so that the information signal is synchronized in the desired direction.   The array antenna apparatus according to claim 1, wherein the information signal beamforming arithmetic circuit controls the delay amount of each of the delay circuits using the estimated delay profile.   2. The array antenna according to claim 1, wherein the delay circuit delays the information signals branched and input by delaying the carrier wave modulated by the information signal. 3. apparatus. A plurality of antennas arranged at positions where the relationship between the path difference in the desired direction and the path difference in the suppression direction cannot be ignored with respect to the wavelength of the information signal, the information signal is branched into a plurality of paths, and the branched An array antenna control method performed by an array antenna apparatus that modulates a carrier wave with a received information signal and transmits the modulated signal using the plurality of antennas,
A delay step for delaying each of the information signals branched and input;
An information signal beam forming calculation step for controlling a delay amount of the plurality of delay circuits;
An array antenna control method comprising:

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