JP7062299B2 - Signal processing equipment, signal processing systems, signal processing methods, and programs - Google Patents

Description

The present invention relates to a signal processing device, a signal processing system, a signal processing method, and a program.

As a system for collecting position information of ships in the ocean, there is an automatic identification system (hereinafter referred to as "AIS"). As a device used for AIS, for example, there is an AIS receiver that receives and collects an AIS signal transmitted by a ship or the like (see, for example, Patent Document 1). The antenna in the conventional AIS is installed in a land station on the coast, for example, and its coverage area is about 20 to 30 nautical miles (37 to 55 km), which is hard to say. On the other hand, there is an AIS receiver in which an antenna is provided on an artificial satellite (see, for example, Non-Patent Document 1). Since this AIS receiver receives the AIS signal transmitted from the ship in the ocean by the AIS antenna provided on the artificial satellite, it can be received in a wide range of about 5000 km in diameter.

Since the AIS receiver equipped with an antenna on the artificial satellite receives the AIS signal transmitted from a wide range, the AIS signal interferes in the area where the ship is overcrowded and the received AIS signal cannot be extracted. was there. Therefore, there is a technique for reducing the number of colliding signals by, for example, increasing the directivity of the antenna.

Japanese Unexamined Patent Publication No. 2015-197779

"Satellite Automatic Identification System (AIS) Experiment" SPAISE "", [online], [Search on August 29, 2019], Internet <URL: http://www.satnavi.jaxa.jp/experiment/spaise/ ＞

However, when the number of signals M is close to or greater than the number of antennas N, such as an AIS receiver equipped with an antenna on an artificial satellite, the performance deteriorates in principle and the separation effect is limited in principle. In some cases, the signal cannot be detected. In particular, when the antenna mounted on the artificial satellite is a VHF antenna, the size becomes large, so that it is difficult to mount a large number of antennas on the artificial satellite, which has many restrictions on mounting.

The present invention has been made in consideration of such circumstances, and is to provide a signal processing device, a signal processing system, a signal processing method, and a program capable of detecting a large number of AIS signals.

One aspect of the present invention is a sparse array including a plurality of antenna elements transmitted by a plurality of vessels, respectively, mounted on one artificial satellite, or a plurality of antenna elements mounted on each of a plurality of artificial satellites in a group of satellites. Katri Lao with respect to the signal detected by the detection unit based on the detection unit that detects a plurality of signals received by the antenna, the position information of the artificial satellite, and the distribution information of the plurality of vessels. By performing product expansion, an expansion unit that expands at least one of the number of antenna arrays, the execution aperture length, and the degree of array freedom in the sparse array antenna, and the signal detected by the detection unit and the expansion unit. It is a signal processing device including a determination unit for determining a signal detection direction using an assumed signal that is assumed to be received by a virtual antenna element in the expanded sparse array antenna.

According to one aspect of the present invention, a large number of AIS signals can be detected.

It is a figure which shows an example of the structure of the signal processing system which concerns on embodiment. It is a figure which shows an example of the structure of the receiving equipment 10. It is a figure which shows an example of the arrangement of the 1st antenna element 21 to the 7th antenna element 27. It is a flowchart which shows an example of the processing of a signal processing apparatus 30. It is a figure which shows an example of the arrangement of the antenna element and the virtual antenna element of a sparse array antenna. It is a figure which shows an example of the arrangement of the antenna element and the virtual antenna element of a sparse array antenna.

Hereinafter, the signal processing apparatus, signal processing system, signal processing method, and program of some embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a diagram showing an example of a configuration of a signal processing system according to an embodiment. As shown in FIG. 1, the signal processing system 1 has a receiving facility 10 mounted on the artificial satellite 2. The signal processing system 1 receives, for example, an AIS signal transmitted by each of the plurality of vessels 3 when the plurality of vessels 3 navigate the predetermined observation sea area 4.

FIG. 2 is a diagram showing an example of the configuration of the receiving equipment 10. The receiving equipment 10 includes, for example, a sparse array antenna 20 and a signal processing device 30. The receiving equipment 10 receives the AIS signal transmitted by the plurality of vessels 3 by the sparse array antenna 20. For example, the signal processing device 30 receives a plurality of AIS signals by the sparse array antenna 20. The signal processing device 30 receives the AIS signal transmitted by each of the plurality of vessels 3 by adjusting the signal detection direction of the sparse array antenna 20.

As shown in FIG. 2, the sparse array antenna 20 in the receiving equipment 10 includes a plurality of antenna elements, the first antenna element 21 to the seventh antenna element 27, which are seven antenna elements in the embodiment. The first antenna element 21 to the seventh antenna element 27 are non-uniformly arranged at appropriate positions on the artificial satellite 2 of 1. The portion of the artificial satellite 2 to which the first antenna element 21 to the seventh antenna element 27 are attached may be any portion, for example, a solar cell paddle or another satellite structure. Further, the antenna element in the sparse array antenna 20 may be mounted not only on one artificial satellite but also on each of a plurality of artificial satellites in the satellite group. In a plurality of artificial satellites, one antenna element may be provided or a plurality of antenna elements may be provided.

FIG. 3 is a diagram showing an example of the arrangement of the first antenna element 21 to the seventh antenna element 27. As shown in FIG. 3, the first antenna element 21 to the seventh antenna element 27 are arranged in three rows when viewed from one direction, and the first antenna element 21 to the fourth antenna element 24 are arranged in the first row L1. The fifth antenna element 25 is arranged unevenly in the second row L2, and the sixth antenna element 26 and the seventh antenna element 27 are arranged in the third row L3. The arrangement of the first antenna element 21 to the seventh antenna element 27 in the sparse array antenna 20 is merely an example, and other arrangements may be used. Further, the number of antenna elements in the sparse array antenna 20 may be less than 7, or may be 8 or more. The first antenna element 21 to the seventh antenna element 27 may be arranged on the same plane, or the first antenna may be placed on a surface other than the plane formed by a part of the first antenna element 21 to the seventh antenna element 27. Other parts of the elements 21 to the seventh antenna element 27 may be arranged.

The signal processing device 30 includes, for example, an acquisition unit 31, a detection unit 32, an expansion unit 33, a determination unit 34, an extraction unit 35, and a storage unit 36. The acquisition unit 31 acquires satellite orbit information provided by a downlink station or the like on the ground, information such as ship distribution based on past results and analysis, and the like. Information such as ship distribution includes intensity and frequency of noise interference received together with AIS signals in satellite orbit, and position information of ships and the like. The acquisition unit 31 stores the acquired satellite orbit information and ship distribution information in the storage unit 36.

The detection unit 32 includes seven first AIS sampling circuits 41 to 47 corresponding to the first antenna element 21 to the seventh antenna element 27. The first AIS sampling circuit 41 to the seventh AIS sampling circuit 47 include, for example, a low noise amplifier (LNA), a downsize converter (DC), and an AD converter (AD). The first AIS sampling circuit 41 to the seventh AIS sampling circuit 47 independently sample the AIS signal received by the first antenna element 21 to the seventh antenna element 27, respectively. In this way, the detection unit 32 detects the AIS signal.

The expansion unit 33 calculates the position information of the artificial satellite 2 based on the satellite orbit information acquired by the acquisition unit 31 and stored in the storage unit 36. The expansion unit 33 obtains a high spatial resolution viewing angle and a non-interference viewing angle based on the calculated position information of the artificial satellite 2 and the information such as the ship distribution acquired by the acquisition unit 31 and stored in the storage unit 36. demand.

The required high spatial resolution viewing angle is, for example, an antenna viewing angle that includes a target area for observing a signal in the field of view, and is an antenna viewing angle that is desired to receive signals with high resolution. The target area for signal observation is, for example, a signal dense area, and the signal dense area is an area where the AIS signal is likely to be transmitted, for example, an area where the distribution density of the ship 3 is high or near the coastline of a port. be.

The non-interfering viewing angle is an antenna viewing angle including a signal depopulated region in the field of view, and is an antenna viewing angle in which the grating lobe is in the non-interfering direction. The signal depopulated area is, for example, a ship depopulated area such as a land area or outer space where an AIS signal is not transmitted or is unlikely to be transmitted. The non-interfering direction is a direction in which the AIS signal transmitted by the ship 3 is less likely to interfere or is non-interfering, such as a direction in a non-horizon such as the open sea or space. The expansion unit 33 expands the AIS signal detected by the detection unit 32 by the Katri-Lao product expansion (hereinafter, also referred to as “KR expansion”), so that at least one of the number of antenna arrays, the execution aperture length, and the degree of freedom of the array is one. Extend one. At the time of KR expansion, the expansion unit 33 expands the Katri-Lao product only in the direction of the antenna array, which is effective for the signal obtained by the acquisition unit 31, for example, in order to reduce the overall calculation load. Set conditions such as antenna array direction to reduce the calculation load.

The determination unit 34 generates an assumed signal that is expected to be received by the virtual antenna element in the sparse array antenna expanded by the expansion unit 33. The determination unit 34 determines the signal detection direction of the sparse array antenna 20 based on the AIS signal detected by the detection unit 32 and the generated assumed signal.

The determination unit 34, for example, adjusts the direction of the main lobe of the sparse array antenna 20 to determine the signal detection direction of the sparse array antenna 20. Therefore, for example, the determination unit 34 digitally performs an antenna forming process on the AIS signal detected by the detection unit 32 and the generated assumed signal, and gives a weight to the AIS signal and the assumed signal to synthesize the antenna. Form a beam.

The determination unit 34, for example, separates a plurality of AIS signals by spatial diversity processing and performs digital beamforming. For example, when weights are given to an AIS signal and an assumed signal for synthesis, the determination unit 34 simultaneously forms a multi-beam by parallel processing using a combination of different weights. The determination unit 34 adaptively forms each multi-beam according to a predetermined condition. Digital beamforming is not limited to the procedure of determining the weight according to the gain, beam width, and direction, and means signal separation by a multi-antenna in general. Digital beamforming includes a general method of calculating a situation in which the direction of null, the gain of the main lobe, the position of the side lobes, etc. are convenient for signal separation.

For example, the determination unit 34 arbitrarily determines one target AIS signal among the plurality of AIS signals detected by the detection unit 32, and has a main lobe in a direction of increasing the detection sensitivity of the target AIS signal with respect to the formed antenna beam. Adjust the direction of to determine. The determination unit 34 determines the direction of the main lobe within the high spatial resolution viewing angle, and determines the unnecessary sensitivity direction of the grating lobe, side lobe, etc. within the range of the non-interfering viewing angle as much as possible, or the orbital condition that is satisfied. To be consistent with.

The extraction unit 35 extracts information about the target AIS signal after the determination unit 34 completes the adjustment of the direction of the main lobe. When the extraction unit 35 can extract the information about the target AIS signal, the extraction unit 35 stores the extracted information in the storage unit 36. When the information about the target AIS signal can be extracted, the extraction unit 35 performs angle measurement processing on the ship (hereinafter referred to as “target ship”) that transmits the target AIS signal. The extraction unit 35 calculates the angle of the target ship with respect to the reference direction by the angle measurement process. The reference direction is, for example, a direction orthogonal to the reference plane defined by the first antenna element 21 to the seventh antenna element 27 in the sparse array antenna 20.

Further, the extraction unit 35 causes the determination unit 34 to perform the same processing by using another AIS signal among the plurality of AIS signals as the target AIS signal. When the information about the target AIS signal cannot be extracted, the determination unit 34 is made to adjust the direction of the main lobe again. According to the instruction of the extraction unit 35, the determination unit 34 performs the same processing using another AIS signal as the target AIS signal, or adjusts the direction of the main lobe again.

As shown in FIG. 1, the signal processing system 1 forms a virtual multi-beam (digital multi-beam) from a plurality of areas 5 when receiving an AIS signal transmitted by a plurality of vessels 3. Each receives an AIS signal. In this case, the first antenna element 21 to the seventh antenna element 27 in the sparse array antenna 20 independently receive, for example, AIS signals from a plurality of ships 3 in the observation sea area 4 in a predetermined unidirectional manner.

Next, the processing in the signal processing apparatus 30 will be described. FIG. 4 is a flowchart showing an example of processing of the signal processing device 30. The signal processing device 30 acquires information such as satellite orbit information provided by a downlink station or the like, ship distribution based on past results and analysis, and the like in the acquisition unit 31 (step S201). The acquisition unit 31 stores the acquired satellite orbit information, ship distribution, and other information in the storage unit 36.

Next, the detection unit 32 samples the AIS signal received by the first antenna element 21 to the seventh antenna element 27 in the first AIS sampling circuit 41 to the seventh AIS sampling circuit 47 (step S203). The detection unit 32 performs phase / amplitude processing of the sampled AIS signal (step S205).

Subsequently, the expansion unit 33 generates a correlation function matrix for each of the first antenna element 21 to the seventh antenna element 27 based on the sampling result detected by the detection unit 32 and subjected to phase / amplitude processing (step). S207). Subsequently, the expansion unit 33 reads out the satellite orbit information and the ship distribution information stored in the storage unit 36, extracts the signal dense region to obtain a high spatial resolution viewing angle, and extracts the signal depopulated region to prevent interference. The viewing angle is calculated (step S209).

Subsequently, the expansion unit 33 generates a Katri-Lao product expansion correlation matrix using the generated correlation function matrix for each of the first antenna element 21 to the seventh antenna element 27, and creates the generated Katri-Lao product correlation matrix. By performing the space averaging process, the number of antenna arrays of the sparse array antenna 20 is virtually expanded (step S211). The expansion unit 33 may virtually expand the execution aperture length and the degree of freedom of the array of the sparse array antenna 20 in place of or in addition to the number of antenna arrays. By expanding the number of antenna arrays, the execution aperture length, and the degree of array freedom of the sparse array antenna 20, the number of AIS signals that can be received by the signal processing device 30 is made larger than the number of antenna elements in the sparse array antenna 20. For example, the maximum achievable degree of freedom can be from 2N-1 to the maximum (N2-1) / ² + N with respect to the number of antenna elements N depending on the arrangement of the antenna elements.

Subsequently, the determination unit 34 identifies the number of ships 3 that transmit the AIS signal from the plurality of AIS signals, and determines an arbitrary AIS signal as the target AIS signal from the plurality of AIS signals. Subsequently, the determination unit 34 performs digital beamforming to form an antenna beam, and adjusts the direction of the main lobe of the sparse array antenna 20 to the direction of the ship 3 that transmits the target AIS signal (step S213). The target AIS signal determined here may be determined in any way, and for example, the AIS signal having the highest radio field strength may be used as the target AIS signal. The direction of the main lobe is, for example, within the high spatial resolution viewing angle required, and unnecessary sensitivity directions such as grating lobes and side lobes are determined within the non-interfering viewing angle as much as possible, or are matched with the established orbital conditions. ..

After adjusting the direction of the main lobe of the sparse array antenna 20, the extraction unit 35 performs angle measurement processing on the target ship, calculates the angle of the target ship with respect to the reference direction, and performs processing for extracting the target AIS signal. (Step S215). Subsequently, the extraction unit 35 stores the calculated angle of the target ship with respect to the reference direction and the extracted target AIS in the storage unit 36 (step S217).

Subsequently, the determination unit 34 calculates the angle of the target ship with respect to the reference direction, and determines whether or not there is a remaining ship that has not been processed to extract the target AIS signal (step S219). When it is determined that there are still vessels that have not been processed to extract the target AIS signal while calculating the angle of the target vessel with respect to the reference direction, the determination unit 34 has not performed the process of extracting the target AIS signal. Determines an arbitrary target AIS signal from the AIS signals transmitted by the determination unit 34, and the determination unit 34 and the extraction unit 35 repeat the processes of steps S213 to S217.

When the determination unit 34 performs a process of extracting the target AIS signal with all the ships transmitting the AIS signal as the target ships, and in step S219, it is determined that there is no remaining ship that has not been processed to extract the target AIS signal. In addition, the signal processing device 30 ends the process shown in FIG.

The receiving equipment 10 in the signal processing system 1 of the embodiment receives the AIS signal transmitted by the ship 3 by the sparse array antenna 20 provided in the artificial satellite 2. In the sparse array antenna 20, since the antenna elements are arranged non-uniformly, the aperture length as an antenna for receiving the AIS signal can be expanded.

Further, the signal processing device 30 in the signal processing system 1 of the embodiment performs Katri-Lao product expansion on the AIS signal received by the sparse array antenna 20 to form a virtual antenna element. The signal processing device 30 determines the signal detection direction of the sparse array antenna 20 using the AIS signal received by the sparse array antenna 20 and the assumed signal expected to be received by the virtual antenna element, and determines the signal detection direction of the sparse array antenna 20 to obtain the AIS signal. I'm receiving. Therefore, it is possible to receive more AIS signals than the number of antenna elements provided in the sparse array antenna 20, for example, a number of AIS signals close to the square of the number of antenna elements at the maximum. Therefore, a large number of AIS signals can be detected.

An example of the arrangement of virtual antenna elements by expanding the number of antenna arrays of the sparse array antenna 20 will be described. For example, in the sparse array antenna 20 shown in FIG. 3, as shown in FIG. 5, a plurality of virtual antenna elements VA may be arranged side by side on both outer sides of the first antenna element 21 to the fourth antenna element 24. Alternatively, as shown in FIG. 6, the row in which the first antenna element 21 to the fourth antenna element 24 are arranged, the row in which the fifth antenna element 25 is arranged, and the sixth antenna element 26 and the seventh antenna element 27 are arranged. The virtual antenna element VA may be arranged side by side in each of the three rows of the provided rows, and the virtual antenna element VA may be arranged in a row outside these three rows.

In this way, when arranging the virtual antenna element VA, for example, the determination unit 34 may arrange the position of the virtual antenna element VA at a position where the signal transmitted from the signal dense region can be received. .. The determination unit 34 is, for example, when the signal dense region exists outside the region where the signal can be received in the sparse array antenna 20 before arranging the virtual antenna element VA, as shown in FIG. 5, the first antenna element A plurality of virtual antenna elements VA may be arranged side by side on both outer sides of the 21st to 4th antenna elements 24. Further, when the area receivable by the sparse array antenna 20 before arranging the virtual antenna element VA is between the first antenna element 21 to the seventh antenna element 27, the virtual antenna element VA fills the space between the first antenna elements 21 and the seventh antenna element 27. May be placed.

Further, in the signal processing system 1 of the embodiment, the signal detection direction of the sparse array antenna is determined according to the amount of the received AIS signal. For example, the signal detection direction of the sparse array antenna 20 is determined so that the generation direction of the grating lobe of the sparse array antenna 20 is the direction in which the AIS signal transmitted by the ship 3 does not interfere. Therefore, unnecessary expansion processing can be suppressed, so that the calculation load of the KR product expansion array processing can be efficiently reduced. Furthermore, by reducing the computational load, the feasibility of satellite-mounted processing can be improved and the latency can be improved.

Further, in the signal processing system 1 of the embodiment, the signal detection direction of the sparse array antenna 20 is densely set only within the high spatial resolution viewing angle where it is desired to include the signal dense region and detect the signal with high spatial resolution. Set and process repeatedly. Therefore, the computational load of the KR product expansion array processing can be efficiently reduced.

In the above embodiment, the signal processing device 30 is provided in the receiving equipment 10 so as to be mounted on the artificial satellite 2. However, the signal processing device 30 is provided in a land region other than the artificial satellite 2, for example. May be good. In this case, the sparse array antenna 20 is mounted on the artificial satellite 2, and the signal received by the sparse array antenna 20 mounted on the artificial satellite 2 may be transmitted to the signal processing device 30 as it is via the downlink station.

Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other embodiments, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and variations thereof are included in the scope of the invention described in the claims and the equivalent scope thereof, as are included in the scope and gist of the invention. For example, it can be used for radio wave information collection, radar, or the like by a satellite having an array antenna or a group of satellites having at least one antenna.

1 ... Signal processing system 2 ... Artificial satellite 3 ... Ship 20 ... Sparse array antennas 21 to 27 ... 1st antenna to 7th antenna 30 ... Signal processing device 31 ... Acquisition unit 32 ... Detection unit 33 ... Expansion unit 34 ... Determination unit 35 ... Extraction unit 36 ... Storage units 41 to 47 ... 1st AIS sampling circuit to 7th AIS sampling circuit VA ... Virtual antenna element

Claims (8)

Multiple antenna elements transmitted by multiple vessels, respectively, or received by a sparse array antenna containing multiple antenna elements mounted on one satellite or multiple antenna elements mounted on each of multiple satellites in a satellite group. A detector that detects signals and
The number of antenna arrays in the sparse array antenna by performing Katri-Lao product expansion on the signal detected by the detection unit based on the position information of the artificial satellite and the distribution information of the plurality of vessels. , Execution opening length, and an extension that extends at least one of the array degrees of freedom.
A determination unit that determines the signal detection direction using the signal detected by the detection unit and the assumed signal that is assumed to be received by the virtual antenna element in the sparse array antenna extended by the expansion unit.
To prepare
Signal processing device. The expansion unit expands the sparse array antenna toward a position where signals transmitted from the signal dense region can be received.
The signal processing apparatus according to claim 1. The expansion unit expands the Katri-Lao product only in the direction of the antenna array that is effective for the signal detected by the detection unit, and the number of antenna arrays in the sparse array antenna so as to reduce the overall computational load. Extends at least one of the execution aperture length and the array degree of freedom,
The signal processing apparatus according to claim 1. The determination unit determines the signal detection direction of the sparse array antenna so that the generation direction of the grating lobe of the sparse array antenna is a direction in which the signal transmitted by the ship is non-interfering.
The signal processing apparatus according to any one of claims 1 to 3. The determination unit determines the signal detection direction of the sparse array antenna within the viewing angle of the antenna including the signal dense region.
The signal processing apparatus according to any one of claims 1 to 4. The signal processing device according to any one of claims 1 to 5.
A sparse array antenna that includes a plurality of antenna elements mounted on one artificial satellite or a plurality of antenna elements mounted on each of a plurality of artificial satellites in a group of satellites and receives signals transmitted by a plurality of vessels. , Equipped with
Signal processing system. The computer of the signal processing device
Multiple antenna elements transmitted by multiple vessels, respectively, or received by a sparse array antenna containing multiple antenna elements mounted on one satellite or multiple antenna elements mounted on each of multiple satellites in a satellite group. Detect the signal and
By performing Katri-Lao product expansion on the detected signal based on the position information of the artificial satellite and the distribution information of the plurality of vessels, the number of antenna arrays and the execution opening length in the sparse array antenna are performed. , And at least one of the array degrees of freedom
The signal detection direction is determined using the detected signal and the assumed signal expected to be received by the virtual antenna element in the extended sparse array antenna.
Signal processing method. To the computer of the signal processing device,
Multiple antenna elements transmitted by multiple vessels, respectively, or received by a sparse array antenna containing multiple antenna elements mounted on one satellite or multiple antenna elements mounted on each of multiple satellites in a satellite group. Detect the signal,
Based on the position information of the artificial satellite and the distribution information of the plurality of vessels, the Katri-Lao product expansion is performed on the detected signal, so that the number of antenna arrays in the sparse array antenna and the execution opening are executed. To execute a process that expands at least one of the length and the degree of freedom of the array,
Using the detected signal and the assumed signal expected to be received by the virtual antenna element in the extended sparse array antenna, the signal detection direction is determined.
program.

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