Radar system
Patent Information
- Application Number
- JP2021135596
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- Filing Date
- 2021-08-23
- Publication Date
- 2025-06-02
- Estimated Expiration
- 2041-08-23
AI Technical Summary
Existing radar systems face challenges in stably monitoring areas beyond the line-of-sight range from land due to the instability of radio wave curtains formed by omnidirectional antenna beams, which are affected by ocean waves and wind, and the high power requirements for offshore radar stations.
A radar system comprising a plurality of floating bodies with phased array antennas and passive radars, forming a stable curtain-like radar beam over the ocean, using position holding mechanisms and communication units to maintain a constant relative positional relationship, and deploying monitoring beams parallel to the vertical and extending direction of the floating bodies, with ground equipment receiving detection information.
The system enables stable monitoring of areas outside the line-of-sight range at a low cost by forming a stable radio wave curtain using phased array antennas and passive radars, minimizing power consumption and extending the monitoring range with minimal energy, suitable for both battery and engine-powered unmanned ships.
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Abstract
Description
Technical Field
[0005]
[0001] Embodiments of the present invention relate to a radar system.
Background Art
[0002] Detecting a target approaching from afar is an important theme in radar technology. The farther the detectable target, the better. However, extending the monitoring distance leads to an increase in transmission output and ultimately results in a trade-off with cost. Therefore, there is a need for a radar system that can detect targets outside the line of sight from land by arranging multiple radars on the ocean.
Prior Art Documents
Patent Documents
[0003]
Patent Document 1
Summary of the Invention
Problems to be Solved by the Invention
[0004] If the radar wave irradiation areas individually developed by radars arranged in a row are combined, a curtain-shaped radio wave area can be formed over a long distance. That is, by forming a radio wave curtain on the ocean and detecting that a target has passed through the curtain, targets in areas that cannot be seen from land can also be captured.
[0005] However, it is very difficult to stably maintain the radio wave curtain. For example, a curtain formed by overlapping non-directional antenna beams is easily affected by ocean waves and winds. In addition, the power required to operate a radar transmitting station on the ocean needs to be minimized as much as possible even when self-supplied by a fuel cell or the like. There is a need for a technology that further concretizes known technologies and enables stable monitoring of areas beyond the line of sight from land. Therefore, the objective is to provide a low-cost radar system that can reliably monitor areas outside the line of sight. [Means for solving the problem]
[0006] According to one embodiment, the radar system comprises a plurality of floating bodies arranged in a row on the ocean, and ground equipment installed on land that can communicate wirelessly with each floating body. Each floating body is equipped with a position-holding means for maintaining a constant relative positional relationship with other floating bodies in the row, a radar device, and a communication unit. The radar device deploys a curtain-like radar beam parallel to the plane formed by the vertical direction and the direction of extension of the row between adjacent floating bodies. The communication unit notifies the ground equipment of detection information when the radar device detects a target. The ground equipment is equipped with a receiving unit that receives detection information from the floating bodies. [Brief explanation of the drawing]
[0007] [Figure 1] Figure 1 shows an example of a radar system according to the embodiment. [Figure 2] Figure 2 is an external view showing an example of an unmanned vessel 10. [Figure 3] Figure 3 is a side view of the phased array radar 11. [Figure 4] Figure 4 is a perspective view showing an example of the appearance of the phased array radar 11. [Figure 5] Figure 5 shows an example of the gimbal section 11c. [Figure 6] Figure 6 is a functional block diagram showing an example of the functions provided by the unmanned vessel 10. [Figure 7] Figure 7 shows the state of the monitoring beam when the unmanned vessel 10 is in a horizontal position. [Figure 8] Figure 8 shows the state of the monitoring beam when the unmanned vessel 10 rolls. [Figure 9] Figure 9 shows the unmanned vessel 10 in the state of being at the first yaw angle (1). [Figure 10] Figure 10 shows the unmanned vessel 10 in the state of being at the second yaw angle (2). [Figure 11] Figure 11 is a functional block diagram showing an example of ground equipment 20. [Figure 12] Figure 12 shows an example of the initial phase involved in target detection. [Figure 13] Figure 13 shows the aircraft 200 after passing through the radio wave curtain. [Figure 14] Figure 14 shows an example of the initial phase involved in detecting target information. [Modes for carrying out the invention]
[0008] Figure 1 shows an example of a radar system according to an embodiment. This system comprises multiple unmanned surface vehicles (USVs) 10 as floating bodies deployed on the ocean, and ground equipment 20 installed on land that can communicate wirelessly with the USVs 10. The USVs 10 are arranged in a line in an area beyond the line of sight from land.
[0009] The unmanned vessel 10 and the ground equipment 20 can communicate via a wireless link. If direct communication between them is difficult, the wireless link can be extended by, for example, placing a relay ship 30 within line of sight from land. Furthermore, by using a satellite link via satellite 100, the distance between the unmanned vessel 10 and the ground equipment 20 can be extended even further.
[0010] The unmanned vessel 10 forms a radio wave curtain between itself and an adjacent unmanned vessel 10. In other words, each unmanned vessel 10 is equipped with a radar device that deploys its own surveillance beam, and by combining these individual surveillance beams, a large curtain-like radar beam (radio wave curtain) is formed. That is, the surveillance beams constitute a part of the radar beam.
[0011] The radio wave curtain is deployed parallel to the plane formed by the extending direction and the vertical direction of the line of the unmanned boats 10. For example, if each of the unmanned boats 10 forms a monitoring beam with a size of 20 km in the horizontal direction and about 30,000 ft in the vertical direction, three unmanned boats 10 can form a radio wave curtain with a width of 120 km and a vertical height of 30,000 ft. The coverage area of the radar system is formed by this radio wave curtain.
[0012] FIG. 2 is an external view showing an example of the unmanned boat 10. The unmanned boat 10 includes a phased array radar 11 and a passive radar 12. Among these, the phased array radar 11 deploys a monitoring beam and forms a radio wave curtain jointly with other unmanned boats 10. The passive radar 12 includes, for example, an omnidirectional pole antenna, and can receive radar waves radiated from other unmanned boats 10 and capture a target by passive radar operation.
[0013] FIG. 3 is a side view of the phased array radar 11. Further, FIG. 4 is a perspective view showing an example of the appearance of the phased array radar 11. In FIG. 3, the phased array radar 11 includes an antenna unit ANT and a gimbal unit 11c that spatially stabilizes this antenna unit ANT. Also, as shown in these figures, the antenna unit ANT includes a first phased array antenna 11a and a second phased array antenna 11b. Each of the phased array antennas 11a, 11b is arranged such that their antenna apertures face each other's backs (back-to-back configuration). Each aperture is fixed at an inclination of, for example, 45° with respect to the vertical.
[0014] FIG. 5 is a diagram showing an example of the gimbal unit 11c. The gimbal unit 11c is, for example, a single-axis gimbal, and includes a gimbal motor 9 that rotationally drives the antenna unit ANT around the azimuth axis shown by the dashed-dotted line in the figure.
[0015] FIG. 6 is a functional block diagram showing an example of the functions provided in the unmanned ship 10. In addition to the configuration shown in FIGS. 2 to 5, the unmanned ship 10 includes a GPS (Global Positioning System) device 13, an attitude detection unit 14, a motor unit 15, a communication unit 16, and a passive radar 12.
[0016] The GPS device 13 receives positioning signals from GPS satellites and calculates the position information of the unmanned ship 10. The position information is notified to the attitude detection unit 14 and the motor unit 15. Among these, the motor unit 15 is a moving device having an engine or an electric motor, a screw, a steering mechanism, etc., and includes a course keeping function 15a and a fixed point holding function 15b. The course keeping function 15a moves the unmanned ship 10 to the deployment position on the ocean along a preset course. The fixed point holding function 15b keeps the position of the unmanned ship that has arrived at the deployment position constant without being affected by ocean currents, winds, etc. That is, the fixed point holding function 15b keeps the relative positional relationship with other unmanned ships 10 in the row of the unmanned ship 10 constant based on the calculated own position information.
[0017] The attitude detection unit 14 detects the attitude around the three axes of the unmanned ship 10 and the change in attitude by, for example, a gyro mechanism. The detected information (attitude information) is passed to the control unit 18 of the phased array radar 11.
[0018] The control unit 18 spatially stabilizes the monitoring beam deployed by the antenna unit ANT. That is, the control unit 18 electronically controls the gimbal unit 11c and the monitoring beam so as to cancel the change in the attitude of the hull based on the attitude information of the unmanned ship 10.
[0019] Figure 7 shows the state of the monitoring beam when the unmanned vessel 10 is in a horizontal position. Suppose the vessel rotates (rolls) around the roll axis from this state, as shown in Figure 8. When this happens, the attitude detection unit 14 detects this movement and notifies the control unit 18 of the attitude information. In response, the control unit 18 instantly directs the monitoring beam of the tilted phased array antenna vertically upward, and the monitoring beam of the other phased array antenna vertically downward. As a result, the radio wave curtain is maintained stably regardless of the rolling motion of the unmanned vessel 10. As shown in Figure 8, it can be seen that a rolling of, for example, about 30 degrees can be sufficiently corrected.
[0020] Furthermore, the control unit 18 also performs control to stabilize the beam plane in response to rotation (yawing) around the yaw axis of the hull. Specifically, the control unit 18 controls the gimbal section 11c to counteract changes in the hull's attitude based on the attitude information of the unmanned vessel 10.
[0021] Figure 9 shows the state in which the unmanned vessel 10 is at the first yaw angle (1). The radio wave curtain (Figure 1) is assumed to be stable in this state. Suppose that the bow direction of the unmanned vessel 10 changes from this state and reaches the state shown in Figure 10, which is the second yaw angle (2). When this happens, the attitude detection unit 14 detects this motion and notifies the control unit 18 of the attitude information. In response, the control unit 18 provides a drive signal to the gimbal motor 9 (Figure 5) of the gimbal unit 11c, keeping the spatial orientation of the antenna unit ANT constant. As a result, the radio wave curtain is maintained stably regardless of the yaw motion of the unmanned vessel 10.
[0022] Returning to Figure 6, let's continue the explanation. The communication unit 16 is a platform for wireless communication with the ground equipment 20. When the phased array radar 11 detects a target, the communication unit 16 notifies the ground equipment 20 of the detection information.
[0023] The passive radar 12 detects targets by receiving direct and reflected radar waves (target echoes) emitted from other unmanned vessels 10 using a pole antenna 17. Here, the source of the radar waves can be identified by a simple pulse analysis, and interference separation can be performed using the results of the pulse analysis. In other words, by setting the waveform of the radar pulses of the phased array radar 11 to a different frequency and modulation method for each unmanned vessel 10, the source and location of each radar pulse can be uniquely identified. The position information of each source (unmanned vessel 10), the direction of arrival of the target echo, and angle measurement processing can be used to determine the position of the target in three dimensions. The position information of the source can be shared between unmanned vessels 10 using a dedicated data link line.
[0024] Even when a target is detected by the passive radar 12, the communication unit 16 notifies the ground equipment 20 of the detection information. Thus, in this embodiment, monostatic operation using the phased array radar 11 is the basis, and by further using the passive radar 12 in combination, the coverage area monitoring capability can be improved complementaryly.
[0025] Figure 11 is a functional block diagram showing an example of ground equipment 20. The ground equipment 20 can be mounted on a vehicle, for example, and comprises an antenna unit 41, a data link unit 42, a detection information processing unit 43, an operation display unit 44, and a control unit 45. The antenna unit 41 forms a wireless link with each unmanned vessel 10 to send and receive data link signals and receives detection information notified by each unmanned vessel 10.
[0026] The data link unit 42 extracts received data and self-position data from the data link signals sent from each unmanned vessel 10 and sends them to the detection information processing unit 43. The data link unit 42 also acquires beam control information and the like from the control unit 45 and sends it to each unmanned vessel 10 via the antenna unit 41.
[0027] The detection information processing unit 43 processes the detection information to extract target information and passes it to the operation display unit 44. The operation display unit 44 visually displays the target information and receives various instructions and operations from operators, etc., and forwards them to the respective units. The control unit 45 generates beam control and other commands for the unmanned vessel 10 based on the instructions and operations from operators, etc., received by the operation display unit 44, and the operating status of each part of the radar system.
[0028] Figure 12 shows an example of the initial phase of target detection. In the state shown in Figure 12, the aircraft 200 is approaching the radio wave curtain, but target detection has not yet occurred. Subsequently, as shown in Figure 13, once the aircraft 200 passes through the radio wave curtain, target information (3D position of the target, time of passage, etc.) is acquired by the phased array radar 11 of the unmanned vessel 10, and detection information including this target information is notified to the ground equipment 20. Figure 13 shows an example in which detection information is notified to the ground equipment 20 via the relay ship 30 and satellite 100. This allows the ground equipment 20 to immediately know when the aircraft 200 passes through the radio wave curtain and to take appropriate action early. In other words, the ground equipment 20 can recognize the aircraft 200 approaching from outside the line of sight while it is still outside the line of sight.
[0029] Figure 14 is a schematic diagram illustrating passive rayder operation. Three unmanned vessels 10 are labeled USV1, USV2, and USV3 for explanation. For example, for passive rayder operation between USV1 and USV2, pulse calibration should be performed between USV1 and USV2. Similarly, for passive rayder operation between USV2 and USV3, pulse calibration should be performed between USV2 and USV3. In this way, interference can be avoided.
[0030] As described above, in this embodiment, the unmanned vessel 10 is equipped with a back-to-back phased array antenna, and a radio wave curtain is formed by extending plate-shaped surveillance beams to the left and right between adjacent unmanned vessels 10. By configuring the surveillance range as a shape close to a plate-like surface, rather than as a volume with three-dimensional distance, azimuth width, and depth, the radar coverage area can be formed with the minimum necessary energy, and an energy-saving system can be constructed. This is a particularly significant advantage when the unmanned vessel 10 is powered by batteries. Of course, the advantages remain the same even when the unmanned vessel 10 is powered by an engine. Energy saving not only provides cost benefits but also makes it possible to extend the operating time from the time the system is deployed.
[0031] In another embodiment, the antenna is mounted on a rotating gimbal to stabilize the radio wave curtain by physically canceling out changes in the attitude of the unmanned vessel 10. Furthermore, by using a phased array antenna whose beam shape can be electronically controlled, changes in the attitude of the unmanned vessel 10 can be electronically canceled out, further stabilizing the radio wave curtain. Based on these considerations, according to this embodiment, it is possible to provide a radar system that can reliably monitor areas outside the line of sight from land, at a low cost.
[0032] It should be noted that this invention is not limited to the embodiments described above. For example, the unmanned vessel 10 does not need to be strictly unmanned and may be manned. Alternatively, a buoy anchored to the seabed can be used instead of the unmanned vessel 10. Using a buoy allows the motor unit 15 to be omitted from the functional block in Figure 6, further reducing costs.
[0033] Furthermore, although the embodiment shows unmanned vessels 10 arranged in a single line, it is of course possible to form multiple lines. By arranging the lines of unmanned vessels 10 one after another, the range in which targets can be detected can be successively expanded. In addition, although the embodiment shows a communication line via satellite 100, it is also possible to use airships located at lower altitudes, stratospheric platforms, unmanned aerial vehicles, etc., as data link platforms.
[0034] While embodiments have been described, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications are permitted without departing from the spirit of the invention. These embodiments and their variations are included within the scope and spirit of the invention, as well as within the scope of the claims and their equivalents. [Explanation of Symbols]
[0035] 9...Gimbal motor, 10...Unmanned vessel, ANT...Antenna unit, 11...Phased array radar, 11a,11b...Phased array antenna, 11c...Gimbal unit, 12...Passive radar, 13...GPS device, 14...Attitude detection unit, 15...Motor unit, 15a...Route keeping function, 15b...Fixed point keeping function, 16...Communication unit, 17...Pole antenna, 18...Control unit, 20...Ground equipment, 30...Relay ship, 41...Antenna unit, 42...Data link unit, 43...Detection information processing unit, 44...Operation display unit, 45...Control unit, 100...Satellite, 200...Aircraft.
Claims
1. a plurality of floating bodies arranged in a row on the ocean; a ground facility installed on land and capable of wireless communication with the plurality of floating bodies; Each of the floating bodies is a position maintaining means for maintaining a constant relative positional relationship with other floating bodies in the row; a radar device that deploys a curtain-like radar beam between adjacent floating bodies and that is parallel to a plane formed by a vertical direction and an extension direction of the row; a communication unit that notifies the ground equipment of detection information when a target is detected by the radar device, The ground equipment includes: A radar system comprising a receiving unit that receives the detection information from the floating body.
2. The radar device an antenna unit including a phased array antenna that deploys a surveillance beam that forms a part of the radar beam; 10. The radar system of claim 1, further comprising: a controller for spatially stabilizing the surveillance beam.
3. 3. The radar system according to claim 2, wherein the antenna section comprises first and second phased array antennas arranged back to back with their antenna apertures at a predetermined angle.
4. The floating body includes an attitude detection unit that detects a change in attitude, The radar system of claim 2 , wherein the control unit electronically controls the surveillance beam to counteract the detected attitude change.
5. The floating body includes an attitude detection unit that detects a change in attitude, the radar device includes a gimbal unit that spatially stabilizes the antenna unit, The radar system according to claim 2 , wherein the control unit controls the gimbal unit so as to counteract the detected change in attitude.
6. The radar system according to claim 1 , wherein the floating body is provided with a passive radar that receives reflected waves of radar waves emitted from another floating body and captures the target.
7. 7. The radar system according to claim 1, wherein the floating body is an anchored buoy.
8. The radar system according to claim 1 , wherein the floating body is a vessel having a fixed position keeping function.