Radar device and signal processing method

Abstract

To provide a radar device with which performance for capturing drones is enhanced.SOLUTION: A radar device according to one embodiment comprises a fused array antenna, a transmission / reception unit, a beam control unit, a selection processing unit, a data acquisition unit, and a target information calculation unit. The transmission / reception unit transmits / receives a radar wave from the fused array antenna. The beam control unit electronically controls transmitted and received beams of a radar wave. The selection processing unit selects either a first scheme for scanning a space with a pencil beam or a second scheme for forming a multi-beam at the time of reception, on the basis of a preset reference value. The data acquisition unit acquires radar data related to a target by the selected scheme. The target information calculation unit calculates target information from the acquired radar data.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] An embodiment of the present invention relates to a radar device and a signal processing method. [Background technology]

[0002] An unmanned aerial vehicle (UAV) is an object that can move through the air by radio control or autonomously, and so-called drones also fall into this category. In recent years, drone technology has developed remarkably and is now being used in a wide range of fields, such as understanding the situation after a disaster and inspecting infrastructure. On the other hand, there have also been cases of drones being used for malicious purposes, such as intrusions into airports that resulted in runways being closed for long periods of time, intrusions into power plants causing disruption of operations, and terrorist acts targeting important people.

[0003] Known technologies to counter harmful drones (counter-drone technologies) include emitting powerful electromagnetic waves to disrupt approaching drones, physically destroying them, and capturing them with a cast net. In any case, it is important to be able to detect drones from as far away as possible in order to have enough time for a response sequence. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5586292 Summary of the Invention [Problem to be solved by the invention]

[0005] Drones are so small that even large radars have difficulty detecting them from a distance. For example, some products have an RCS (Radar Cross Section) of only 0.01 square meters. In addition, drones behave erratically, flying in zigzags and making sudden stops / turns around, making it difficult to use existing radar equipment for monitoring aircraft and flying objects as is.

[0006] Therefore, the objective is to provide a radar device and a signal processing method that have improved drone capture performance. [Means for solving the problem]

[0007] According to an embodiment, a radar device includes a phased array antenna, a transmitting / receiving unit, a beam control unit, a selection processing unit, a data acquisition unit, and a target information calculation unit. The transmitting / receiving unit transmits and receives radar waves from the phased array antenna. The beam control unit electronically controls the transmission beam and the reception beam of the radar waves. The selection processing unit selects either a first method of scanning a space with a pencil beam or a second method of forming multiple beams during reception based on a preset reference value. The data acquisition unit acquires radar data related to the target using the selected method. The target information calculation unit calculates target information from the acquired radar data. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a block diagram showing an example of a radar device according to an embodiment. [Diagram 2] FIG. 2 is a functional block diagram illustrating an example of the radar device of FIG. [Diagram 3] FIG. 3 is a functional block diagram showing an example of the signal processing unit 12. As shown in FIG. [Figure 4] FIG. 4 is a schematic diagram showing an example of a beam shape and an antenna aperture in a holographic radar system. [Diagram 5]FIG. 5 is a schematic diagram showing another example of a beam shape and an antenna aperture in a holographic radar system. [Figure 6] FIG. 6 is a flowchart illustrating an example of a processing procedure of the radar device according to the embodiment. [Figure 7] FIG. 7 is a flowchart showing an example of a processing procedure in the preset mode. [Figure 8] FIG. 8 is a flowchart illustrating an example of a processing procedure in the variable mode. [Figure 9] FIG. 9 is a flowchart illustrating another example of the processing procedure of the radar device according to the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] <Summary> First, an overview will be given. Generally, a pulse radar system is used for radar that detects targets over long distances. In this type of radar, the antenna aperture is used for both transmission and reception, and transmission and reception are performed using pencil beams. The radar's signal processing unit is one position, and it sequentially scans azimuth and elevation angles to monitor the required search range within the required search time. Here, the signal processing unit is a unit of 1 CPI (Coherent Pulse Interval), which is the space of azimuth and elevation angles determined by the beam width.

[0010] <Progressive scan method> In the embodiment, this scanning method of scanning the space with a pencil beam is called a sequential scanning method. In this method, since a high gain can be obtained by transmitting and receiving using the full aperture, it is possible to detect a target at a long distance. However, there is a gap in the search time until the beam is irradiated again at a certain position. In other words, the sequential scanning method is suitable for detecting small targets at a long distance with high gain, but the time required to monitor the entire search range (scan rate) is long. For this reason, the observation rate cannot be increased, making it difficult to apply to highly maneuverable targets such as drones.

[0011] By the way, by using DBF (Digital Beam Forming) technology, it is possible to form multiple beams simultaneously. When transmitting, radar waves are sent as a wide beam such as a fan beam, and when receiving, beams pointing in various directions are simultaneously formed using DBF, making it possible to scan a wide space in a short period of time. In other words, the entire search area can be monitored in far fewer attempts than with the sequential scanning method. Depending on the transmission and reception method, it is even possible to cover the entire search range at once.

[0012] <Holographic radar method> In the embodiment, this method of forming multiple beams during reception is called a holographic radar method. In the holographic radar method, data of the entire search range is updated as if viewing a hologram. Since a wide beam is used during transmission, the transmission gain is lower than when using a full aperture, and there is a weakness in detection ability at long distances compared to the sequential scan method. In the embodiment, a technology for effectively applying these two scan methods and tracking a highly maneuverable target such as a drone is disclosed.

[0013] The radar device of the embodiment mainly has the following functions. Pencil beam transmission and reception are possible using the full aperture. By using the full aperture and sequential scanning method, the required search area can be searched in the required search time. It is possible to transmit a wide beam using a portion of the aperture. Pencil beam reception using the entire aperture enables simultaneous multi-beam formation using DBF. The <holographic radar method> enables simultaneous searching of multiple positions using a multi-beam formed receiving beam. The <sequential scan method> is used on the far side of the search range, and the holographic radar method is used on the near side of the search range, and the boundary between the two can be set by the operator. The above functions will now be described in detail.

[0014] <Configuration> Next, the configuration of the radar device according to the embodiment will be described. 1 is a block diagram showing an example of a radar device according to an embodiment. The radar device according to the embodiment includes a radar main body having an antenna unit 10, and a signal processing unit 12. The signal processing unit 12 is a computer, and communicates with the radar main body via a network 30 to obtain radar data.

[0015] The radar main body further includes a transceiver unit 11 that transmits and receives radar waves from the antenna unit 10, and a beam control unit 14 that electronically controls the transmission beam and reception beam of the radar waves. The antenna unit 10 is a phased array antenna that includes multiple antenna elements, and is capable of electronically scanning the beam direction by controlling the wavefront of the radar waves. The signal processing unit 12 generates a radar video signal from the radar data acquired from the radar main body, and displays it on the display unit 13.

[0016] Fig. 2 is a functional block diagram showing an example of the radar device of Fig. 1. The antenna unit 10 radiates radar transmission waves from the transceiver unit 11 into space, and sends received echo pulse signals to the transceiver unit 11. The transceiver unit 11 digitally converts the received signals to generate radar data, which it passes to the signal processing unit 12. The signal processing unit 12 processes the radar data to generate a radar video signal, which it passes to the display unit 13 for visual display. The signal processing unit 12 also controls the beam control unit 14 to control the shape and direction of the transmission beam and reception beam of the antenna unit 10.

[0017] 3 is a functional block diagram showing an example of the signal processing unit 12. The signal processing unit 12 as a computer includes a processor 21, a ROM 22, a RAM 23, a storage unit 24, a communication unit 25, and an operation unit 26. Among these, the communication unit 25 is connected to a network 30 and communicates with the radar main body. The operation unit 26 is a man-machine interface such as a mouse and a keyboard, and accepts user operations. The RAM 23 stores basic software such as a BIOS (Basic Input Output System) used at startup.

[0018] The storage unit 24 stores a program 24a for causing the computer to function as the signal processing unit 12, as well as preset reference values ​​24b and radar data 24c.

[0019] The reference value 24b is information that is a threshold (or boundary) for switching between the <sequential scan method> and the <holographic radar method>, and can be set in advance by the user using the operation unit 26. Of course, a predetermined value may be preset. The reference value 24b may be determined, for example, based on the usage environment of the radar device, the characteristics of the assumed drone, and the resources (weight, dimensions, power capacity, etc.) allocated to the radar. For example, if the operational concept places emphasis on capturing highly maneuverable targets, the boundary should be shifted to the long-distance side, but it is not advisable to reduce the aperture gain too much (to a small aperture). The boundary is determined by a trade-off between ensuring the transmit aperture gain and the allowable search rate.

[0020] The radar data 24c is data acquired from the radar main body via the network 30, and the signal processing unit 12 processes the radar data 24c to calculate target information.

[0021] The processor 21 loads a program 24a stored in the storage unit 24 into the RAM 23 and executes the program 24a to realize functions according to the embodiment. That is, the processor 21 includes a selection processing unit 21a, a data acquisition unit 21b, a target information calculation unit 21c, and a setting unit 21d.

[0022] The selection processing unit 21a selects either the <sequential scanning method> or the <holographic radar method> based on the reference value 24b. In the <sequential scanning method>, a pencil beam is used for transmission and reception, while in the <holographic radar method>, a wide beam is used during transmission and multiple beams are formed during reception. The beam control unit 14 (FIG. 2) switches between these beam shapes by switching the number of driven antenna elements of the antenna unit 10. In other words, the beam can be controlled by using the entire aperture of the antenna unit 10 to form a pencil beam and using only a portion of the aperture to form a wide beam. Furthermore, during reception in the <holographic radar method>, the beam control unit 14 simultaneously forms multiple beams by DBF.

[0023] Figure 4 is a schematic diagram showing an example of a beam shape and antenna aperture in a holographic radar system. Figure 4(a) shows the transmission beam shape, and by using only the central part (shown by the dotted line) of the antenna aperture in Figure 4(b), for example, a wide beam in a fan beam shape can be formed. During reception, as shown in Figure 4(c), multiple beams are formed by DBF, and the independent beams are directed to different azimuths and elevation angles to cover the entire search range simultaneously. In this case, data for the entire search range can be obtained every 1 CPI, and target information can be obtained at a rate that is overwhelmingly higher than the scan rate of the <sequential scan method>. This allows for high performance tracking of targets with irregular or high maneuvering movements.

[0024] Figure 5 is a schematic diagram showing another example of the beam shape and antenna aperture in the holographic radar system. A wide beam as shown in Figure 5(a) can also be formed by separately providing a transmission aperture smaller than the aperture of the antenna unit 10 as shown in Figure 5(b) and transmitting a transmission pulse from this transmission aperture. When receiving, the entire aperture of the antenna unit 10 is used to form the multiple beams shown in Figure 5(c), allowing high-rate observation.

[0025] Returning to Fig. 3, the description will continue. The data acquisition unit 21b acquires radar data 24c relating to the target using the selected method.

[0026] The target information calculation unit 21c calculates target information from the acquired radar data 24c. The target information calculation unit 21c calculates, for example, the distance to the target as the target information. The selection processing unit 21a selects the <sequential scan method> if the distance to the target exceeds a reference value 24b, and selects the <holographic radar method> if the distance is equal to or less than the reference value 24b.

[0027] In addition, the target information calculation unit 21c calculates, for example, the mobility characteristics of the target as the target information. The selection processing unit 21a selects the <sequential scan method> if the mobility characteristics of the target are equal to or less than the reference value 24b, and selects the <holographic radar method> if the mobility characteristics exceed the reference value 24b.

[0028] Here, maneuvering characteristics are, for example, the degree of irregular movement (irregular maneuvering), or a quantity that quantitatively indicates the magnitude of angular velocity relative to distance and the degree of change. A sudden change in speed during movement (speed change maneuvering) can also be quantitatively evaluated using maneuvering characteristics as a measure. In other words, a target that moves irregularly at close range can be said to have high maneuvering characteristics, and the <holographic radar method> is advantageous for capturing such targets. The setting unit 21d accepts the setting of the reference value 24b by the user.

[0029] <effect> Next, the operation of the above configuration will be described. In the following description, it is assumed that a drone flying from a distance is to be detected, and the <sequential scan method> is selected first. 6 to 9 are flowcharts showing an example of a processing procedure of the radar device according to the embodiment. In Fig. 6, the radar device judges whether it is set to a preset mode or a variable mode (step S1). If it is in the preset mode, the processing procedure proceeds to the flowchart in Fig. 7, and if it is in the variable mode, the processing procedure proceeds to the flowchart in Fig. 8.

[0030] <Preset Mode> The preset mode is a mode in which a reference value 24b for switching the scanning method is set in advance as a fixed value, for example, the distance to the target.

[0031] In Fig. 7, the radar device acquires radar data by the <sequential scan method> (step S3) and calculates target information (step S4). If the calculated distance to the target does not exceed a reference value (No in step S5), the <sequential scan method> is selected (step S6) and the radar device forms a pencil beam (step S7) and transmits and receives radar pulses (step S8). The transmission / reception of pulses is repeated while gradually changing the azimuth and elevation angles until the entire search area is scanned (step S9). When radar data of the search area is acquired by the <sequential scan method> in this way (step S10), the process returns to step S4 and the target information is calculated.

[0032] While the above procedure is repeated, it is assumed that the target approaches and reaches a distance equal to or less than the reference value. Then, the result of the determination in step S5 is Yes, and the radar device selects the <holographic radar method> (step S11). Then, as shown in FIG. 4 or FIG. 5, a wide transmission beam is formed using antenna elements with a number smaller than the total aperture of the antenna unit 10 (step S12), and a radar pulse is transmitted (step S13). When the transmission period ends, the radar device immediately forms multiple beams (step S14) and receives a pulse echo (step S15). In this way, when radar data of the search area by the <holographic radar method> is acquired (step S16), the process returns to step S4 again to calculate the target information.

[0033] <Variable mode> The variable mode is a mode in which the reference value can be varied by user operation even during operation. 8, the radar device accepts a reference value set by the user (step S2). The set value is stored in the storage unit 24 (reference value 24b), and the processes from step S3 onward are executed based on the reference value 24b.

[0034] <Effects> As described above, in the embodiment, the two scanning methods, the <sequential scanning method> and the <holographic radar method>, are selectively used according to the target distance to improve the detection performance, particularly for highly maneuverable and slow-moving targets such as drones. In other words, it is possible to detect small targets such as drones at a distance, and to continue to capture highly maneuverable targets such as drones even at close range. In other words, it is possible to improve both the target detection performance and the target tracking performance.

[0035] The <Sequential Scan Method> has a long scan rate, so it is difficult to track irregular or highly maneuvering targets. However, at long distances, these maneuvers are unlikely to occur because they do not produce large angular velocities for the radar, so this is not a fatal problem. Even if the tracking filter (such as the Kalman filter) cannot respond to maneuvers at long distances and loses track, it is possible to resume target tracking by going through the process of detecting the target at long distances and re-establishing the track.

[0036] In the <holographic radar system>, the aperture is made smaller to widen the transmission beam, so the transmission aperture gain is lower than in the sequential scan system, which tends to make target detection difficult at long distances. However, in this embodiment, the <holographic radar system> is applied at short distances, so an environment with a sufficiently high S / N ratio can be maintained, so this does not pose a problem.

[0037] In this way, it is possible to build a radar device that satisfies the conflicting demands of reliably detecting targets with a small RCS (radar cross section) such as drones at long distances, while at the same time successfully tracking targets with irregular maneuvering and high maneuverability at close distances. In other words, according to the embodiment, the weaknesses of the <sequential scanning method> and the <holographic radar method> are mutually complemented, and the performance of detecting drones can be improved.

[0038] In the embodiment, the user can select between a <preset mode> in which a reference value for switching between the two scanning methods is preset in advance, and a <variable mode> in which the reference value can be changed during operation. This makes it possible to change the reference values ​​for the distance and behavior (maneuvering characteristics, etc.) of the target of interest according to the user's desire.

[0039] As a result, according to the embodiments, it is possible to provide a radar device and a signal processing method with improved drone capture performance.

[0040] It should be noted that the present invention is not limited to the above-described embodiment. For example, the reference value for switching between the <sequential scan method> and the <holographic radar method> is not limited to a single value, and multiple reference values ​​may be set according to the size and importance of the monitored area, for example.

[0041] Also, instead of the distance to the target, the maneuvering characteristics of the target may be used as a reference value. 9, if the maneuvering characteristic calculated in step S4 is equal to or less than the reference value (Yes in step S50), the <sequential scan method> is subsequently selected (step S6). On the other hand, if the maneuvering characteristic of the target exceeds the reference value (No in step S50), the radar device selects the <holographic radar method> (step S11).

[0042] Although an embodiment has been described, this embodiment is presented as an example and is not intended to limit the scope of the invention. This novel embodiment can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. This embodiment and its modifications are included in the scope and spirit of the invention, and are included in the scope of the invention and its equivalents described in the claims. [Explanation of symbols]

[0043] 10...antenna unit, 11...transmitter / receiver unit, 12...signal processing unit, 13...display unit, 14...beam control unit, 21...processor, 21a...selection processing unit, 21b...data acquisition unit, 21c...target information calculation unit, 21d...setting unit, 22...ROM, 23...RAM, 24...memory unit, 24a...program, 24b...reference value, 24c...radar data, 25...communication unit, 26...operation unit, 30...network.

Claims

1. A phased array antenna; A transceiver unit that transmits and receives radar waves from the phased array antenna; a beam control unit that electronically controls a transmission beam and a reception beam of the radar wave; a selection processing unit that selects, based on a preset reference value, either a first method of scanning a space with a pencil beam or a second method of forming multiple beams during reception; a data acquisition unit that acquires radar data relating to a target in the selected manner; and a target information calculation unit that calculates target information from the acquired radar data.

2. The phased array antenna comprises a plurality of antenna elements; The radar device according to claim 1 , wherein the beam control unit switches the number of driven antenna elements between when transmitting in the first system and when transmitting in the second system.

3. The beam control unit includes: forming a wide beam by using fewer antenna elements than in the first method during transmission in the second method; The radar device according to claim 2 , wherein the multi-beams are formed by DBF (Digital Beam Forming) processing during reception of the second system.

4. The target information calculation unit calculates a distance to the target, The radar device according to claim 1 , wherein the selection processing unit selects the first method if the distance exceeds the reference value, and selects the second method if the distance is equal to or smaller than the reference value.

5. The target information calculation unit calculates a maneuvering characteristic of the target, The radar device according to claim 1 , wherein the selection processing unit selects the first method if the maneuvering characteristic is equal to or smaller than the reference value, and selects the second method if the maneuvering characteristic exceeds the reference value.

6. The radar device according to claim 4 , further comprising a setting unit that accepts a setting of the reference value by a user.

7. A computer of a radar device including a transmitting / receiving unit that transmits and receives radar waves from a phased array antenna, and a beam control unit that electronically controls a transmission beam and a reception beam of the radar waves, Selecting either a first method of scanning a space with a pencil beam or a second method of forming multiple beams at the time of reception based on a preset reference value; acquiring radar data relating to the target in the selected manner; and calculating target information from the acquired radar data.

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