Indoor target detection method based on millimeter wave radar

Abstract

The invention discloses an indoor target detection method based on a millimeter-wave radar, and the method comprises the steps: obtaining data obtained through the detection of the millimeter-wave radar for an indoor space, and analyzing the position and speed information of an indoor target detected at a current moment t from the data; predicting the position information of the detected target at the current moment t according to the stored path information and speed information of the detected target; and when it is determined that the predicted position information of the detected target is matched with the position information of the indoor target detected at the current moment t, determining the indoor target detected at the current moment t as the detected target. By applying the method, the detection precision and reliability of the indoor target can be further improved through path rationality judgment.

Description

Technical Field

[0001] The present invention relates to the field of computer technology, and in particular to an indoor target detection method based on millimeter wave radar. Background Art

[0002] Millimeter-wave radar personnel positioning is a frontier field that integrates radar technology and indoor positioning technology. In recent years, it has shown great application potential in many scenarios such as smart home, security monitoring, personnel and asset management. Its research background mainly stems from the growing demand for high-precision and real-time indoor positioning, especially in complex and changing indoor environments, where traditional positioning methods often cannot meet the requirements of accurate tracking. The basic principle of millimeter-wave radar is to transmit and receive electromagnetic wave signals, and use the reflection and scattering characteristics of the target object to achieve high-precision measurement and tracking of the target position, speed and even posture. Its core goal is to improve the accuracy, stability and reliability of the indoor positioning system, while reducing the system deployment cost and maintenance complexity. Millimeter-wave radar technology has irreplaceable value in improving user experience, optimizing space management, and enhancing security. It is one of the key technologies to promote the construction of smart cities and realize the in-depth application of the Internet of Things.

[0003] The accuracy and reliability of current indoor target (personnel) detection and counting methods are restricted by many factors, including environmental factors, signal propagation characteristics, positioning algorithm performance, and hardware equipment accuracy. Environmental factors such as indoor layout, obstacle distribution, and wall materials will significantly affect the propagation path and strength of wireless signals, interfere with the positioning results of indoor targets (personnel), and thus affect the detection and counting accuracy of indoor targets (personnel); in addition, signal propagation characteristics, such as multipath effects and non-line-of-sight propagation, are also important causes of positioning errors. Summary of the invention

[0004] In view of this, the purpose of the present invention is to propose an indoor target detection method based on millimeter wave radar, which further improves the detection accuracy and reliability of indoor targets through path rationality judgment.

[0005] Based on the above purpose, the present invention provides an indoor target detection method based on millimeter wave radar, comprising:

[0006] Obtain the data obtained by the millimeter-wave radar for detecting the indoor space, and parse the position and speed information of the indoor target detected at the current time t;

[0007] Predict the position information of the detected target at the current time t based on the stored path information and speed information of the detected target;

[0008] When it is determined that the predicted position information of a detected target matches the position information of an indoor target detected at the current time t, the indoor target detected at the current time t is confirmed as the detected target.

[0009] Furthermore, the method further comprises:

[0010] The detection state of the detected target at time t is set to detected.

[0011] Furthermore, the method further comprises:

[0012] According to the position and speed information of the indoor target detected at the current time t, the path information and speed information of the detected target are updated.

[0013] Furthermore, the method further comprises:

[0014] If the position information of an indoor target detected at the current time t does not match the predicted position information of any detected target, then:

[0015] For the indoor target detected at the current time t, detection of entering and exiting the indoor space is performed;

[0016] If it is determined that the indoor target enters the room, the indoor target detected at the current time t is taken as a new detected target, and the path information and speed information of the new detected target are created based on the position and speed information of the indoor target detected at the current time t.

[0017] Furthermore, the method further comprises:

[0018] If it is determined that the indoor target has not entered the indoor space, the indoor target is defined as a false alarm, and its path information is not retained.

[0019] Furthermore, the method further comprises:

[0020] If the predicted position information of a detected target does not match the position information of any indoor target detected at the current time t, then:

[0021] Performing detection of entering and exiting the indoor space according to the path information of the detected target;

[0022] If it is determined that the detected target leaves the room, the path information of the detected target is cleared.

[0023] Furthermore, the method further comprises:

[0024] If it is determined that the detected target has not left the room, the detection status of the detected target at time t is set to missed detection.

[0025] Furthermore, the method further comprises:

[0026] Counting the number of times the detected target is in a missed detection state or detected state at each moment;

[0027] If the counted missed detection times are greater than the detected times, the path information of the detected target is cleared.

[0028] The present invention also provides a computer device, which includes a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor is used to implement the steps of the above-mentioned indoor target detection method based on millimeter wave radar when executing the computer program.

[0029] The present invention also provides a computer-readable storage medium, in which a computer program is stored. The computer program can be executed by at least one processor so that the at least one processor performs the steps of the above-mentioned indoor target detection method based on millimeter-wave radar.

[0030] In the technical solution of the present invention, the data obtained by the millimeter wave radar for detecting the indoor space is obtained, and the position and speed information of the indoor target detected at the current time t is parsed therefrom; the position information of the detected target at the current time t is predicted according to the stored path information and speed information of the detected target; when it is determined that the predicted position information of a detected target matches the position information of an indoor target detected at the current time t, the indoor target detected at the current time t is confirmed as the detected target. The present invention can optimally estimate the state of the target (such as position, speed, etc.) through the prediction step, and then based on the path rationality judgment, the accuracy and reliability of indoor target detection can be further improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0032] Figure 1 A flow chart of an indoor target detection method based on millimeter wave radar provided by an embodiment of the present invention;

[0033] Figure 2 A schematic diagram of a path for tracking target records provided by an embodiment of the present invention;

[0034] Figure 3a , 3bA comparison diagram of simulation experiment results of the present invention and the prior art;

[0035] Figure 4a , 4b Another comparison diagram of simulation experiment results of the present invention and the prior art;

[0036] Figure 5 A schematic diagram of the hardware structure of a computer device provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0037] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings.

[0038] It should be noted that, unless otherwise defined, the technical terms or scientific terms used in the embodiments of the present invention should be understood by people with ordinary skills in the field to which the present disclosure belongs. The "first", "second" and similar words used in the present disclosure do not represent any order, quantity or importance, but are only used to distinguish different components. "Including" or "comprising" and similar words mean that the elements or objects appearing in front of the word cover the elements or objects listed after the word and their equivalents, without excluding other elements or objects. "Connect" or "connected" and similar words are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0039] The inventors of the present invention consider that Kalman filtering, as an efficient recursive filter, can optimally estimate the state of a target (such as position, speed, etc.) through prediction and update steps in the presence of noise and uncertainty. It can not only effectively integrate redundant information from different sensors (such as Wi-Fi, Bluetooth, UWB, RFID, etc.) to improve the accuracy and robustness of people counting, but also dynamically adapt to environmental changes and reduce counting errors caused by environmental factors;

[0040] Through the prediction and update steps, the state of the target (such as position, speed, etc.) is optimally estimated. The technical solution of the present invention is based on the judgment of path rationality to further improve the accuracy and reliability of indoor target detection; more preferably, the technical solution of the present invention can also be combined with the life cycle algorithm to further improve the accuracy and reliability of indoor target detection.

[0041] The technical solutions of the embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0042] An indoor target detection method based on millimeter wave radar is proposed in an embodiment of the present invention. The specific process is as follows: Figure 1 As shown, the following steps are included:

[0043] Step S101: acquiring data obtained by detecting the indoor space using a millimeter wave radar, and parsing the data to obtain the position and speed information of the indoor target detected at the current time t;

[0044] In this step, the millimeter wave radar can be used to detect the information of the indoor space. After the program preprocessing of the millimeter wave radar module, the serial port data output through the serial port includes the two-dimensional position coordinates, radial velocity and height information of the detected target; specifically, the radar module used preprocesses the point cloud data and outputs the hexadecimal serial port data. The protocol is: 2byte frame header check code, 1byte control word, 1byte command word, 2byte effective data length, multiple target points, each target point has 1byte index, 1byte target size, 1byte target feature, 2byte X-axis position information, 2byte Y-axis position information, 2byte height information, 2byte speed, 2byte check field, 2byte frame tail. The data are all hexadecimal data, and the 16-bit data has positive and negative, the first bit is 0 for positive data, the first bit -1 for negative data, the effective data length = 11 × number of targets, and the check code is the sum of the other data and the last two bits.

[0045] From the data detected by the millimeter-wave radar, the position and speed information of the indoor target detected at the current time t can be parsed; usually, a frame of data sent by the millimeter-wave radar can include the position and speed information of multiple indoor targets detected at the current time t; therefore, by parsing the data sent by the millimeter-wave radar, the position and speed information of multiple indoor targets can be obtained;

[0046] The target list Targetlist=[target1,target2,...,target n ]; where n is the number of detected indoor targets; the nth indoor target target n =[x,y,z,speed,isDetected=1]; wherein x,y,z represent the three-dimensional position information of the nth indoor target, speed represents the speed information of the nth indoor target, and isDetected is 1, indicating that it has been detected.

[0047] Step S102: predicting the position information of the detected target at the current time t according to the stored path information and speed information of the detected target;

[0048] Specifically, for indoor targets previously detected by the millimeter-wave radar, their path information and speed information have been stored as detected targets; and the path information of the detected targets is composed of the position information of the detected targets at each time before the current time t; that is, the path of the nth detected target can be expressed as: Wherein, T is a natural number greater than 0;

[0049] For multiple detected targets, a path list is used to record the path information of all detected targets: Pathlist = [Path1, Path2, ..., Path m ]; where m is the number of detected targets, Path m Indicates the path information of the mth detected target that has been stored. Represents the position and speed information of the nth detected target at time t-τ.

[0050] According to Path n The path information and speed information in the Kalman filter are used to predict the position information target_pre n ; Predict all detected targets in Pathlist:

[0051] Targetlist_predict=[target_pre1,target_pre2,...,target_pre m ];

[0052] When the program starts in the initial stage, it is assumed that there is no one in the room, that is, the initial path list is empty Pathlist = []; the target detected in the first frame is the target that already exists in the room, that is:

[0053]

[0054] Pathlist=[Path1,Path2,...,Path n ];in

[0055] Step S103: Match the predicted position information of the detected target with the position information of an indoor target detected at the current time t; if it is the first matching situation, execute the following step S104; if it is the second matching situation, execute the following step S110; if it is the third matching situation, execute the following step S120;

[0056] In this step, the predicted position information of the detected target is subtracted from the position information of an indoor target detected at the current time t;

[0057] If the difference between the position information of the indoor target detected at the current time t and the position information of a predicted detected target is less than the set threshold, it indicates that the detected indoor target matches the detected target, which is the first matching situation; wherein, the setting of the threshold can be set according to the motion state of the target in the specific application scenario, for example, the threshold = maximum speed of the indoor target × data collection interval × K, and the sensitivity of the target trajectory tracking can be controlled by adjusting the coefficient K;

[0058] For the first matching situation, execute the following step S104;

[0059] For the second and third matching situations, the technical solution of the present invention can also be combined with the life cycle algorithm to further improve the accuracy and reliability of indoor target detection:

[0060] If the difference between the position information of an indoor target detected at the current time t and the position information of any detected target predicted is greater than the set threshold, it indicates that the detected indoor target does not match any detected target, which is the second matching situation; for the second matching situation, the following step S110 is executed;

[0061] If the difference between the predicted position information of a detected target and the position information of any indoor target detected at the current time t is greater than the set threshold, it indicates that the detected target does not match any indoor target detected at the current time t, and the following step S120 is executed;

[0062] Specifically, the position information of all indoor targets detected at the current time t is subtracted from the predicted position information of all detected targets to obtain the deviation matrix: Deviation = D m×n ; Through the deviation matrix, we can get the matching relationship between the newly detected target and the existing path, and record the matching relationship in the matching list Targetlist_match:

[0063] Targetlist_match=[target_match1,target_match2,...,target_match p ]; where p = m×n.

[0064] Step S104: confirming the indoor target detected at the current time t as the detected target;

[0065] Specifically, if the position information of the indoor target detected at the current time t matches the position information of a predicted detected target, then:

[0066] The indoor target detected at the current time t is confirmed as the detected target; and the detection state of the detected target at the time t is set to detected, that is, the isDetected of the detected target at the time t is set to 1;

[0067] Furthermore, according to the position and speed information of the indoor target detected at the current time t, the path information and speed information of the detected target are updated.

[0068] Step S110: for the indoor target detected at the current time t, detection of entering and exiting the indoor space is performed; if it is determined that the indoor target enters the room, the following step S111 is executed; otherwise, the following step S112 is executed;

[0069] Step S111: if it is determined that the indoor target has entered the room, the indoor target detected at the current time t is regarded as a new detected target;

[0070] Specifically, the indoor target detected at the current time t is taken as a new detected target, and according to the position and speed information of the indoor target detected at the current time t, the path information and speed information of the new detected target are created and stored.

[0071] Step S112: If it is determined that the indoor target has not entered the indoor space, the indoor target is defined as a false alarm, and the path information is not retained.

[0072] Step S120: Detection of entering and exiting the indoor space is performed according to the path information of the detected target; if it is determined that the detected target has left the room, step S121 is executed; otherwise, step S122 is executed.

[0073] Step S121: if it is determined that the detected target leaves the room, clearing the path information of the detected target;

[0074] Step S122: if it is determined that the detected target has not left the room, the detection state of the detected target at time t is set to missed detection;

[0075] Step S123: Clear the path information with the number of missed detections greater than 50%.

[0076] In this step, the number of times that the detection status of the detected target at each moment is missed detection and detected is counted respectively; if the counted number of missed detections is greater than the number of detections, the path information of the detected target is cleared.

[0077] Specifically, for the path information Path of the kth detected target kThe detection status of the target at different times isDetected is recorded, that is, whether the target is detected at different times; isDetected is 1, indicating detection. isDetected is 0, indicating missed detection; the number of detections and detection probability of the target within a certain period of time can be calculated based on this: Rate_check = num_Path_isDetected / num_Path_target;

[0078] Among them, num_Path_isDetected represents the number of times the detection state isDetected in the path information is 1, and num_Path_target represents the total number of times the detection state isDetected in the path information is 1 and the detection state isDetected is 0;

[0079] If the detection probability Rate_check of the path information is less than 50%, that is, the number of missed detections is greater than 50%, the path information is deleted; then, the updated Pathlist is output. new =[Path1,Path2,...,Path m ].

[0080] In a simulation experiment, two targets walked normally in the experimental room and entered and exited the room normally through the door. The target positions were detected by millimeter-wave radar, and the indoor target detection method based on millimeter-wave radar of the present invention was used to track the paths of the targets. Figure 2 The path of the target record tracked by the method of the present invention is shown. Figure 3a It shows that when the target leaves the room, the existing technology still has many false alarms. Figure 3b It shows that the method of the present invention can filter out false alarms while maintaining the detection of indoor targets. From the simulation results, it can be seen that the effectiveness of the algorithm proposed by the present invention can normally track the motion path of the detected target and effectively eliminate the influence of missed detection and false alarm, which reflects the advantages of the present invention.

[0081] In another simulation experiment, two targets walked normally in the experimental room, and a third person appeared in the room at an unset position to simulate the impact of multipath signals that suddenly appeared in the room. Figure 4a It shows that the existing technology cannot filter out the false alarm caused by multipath noise that suddenly appears inside the room. Figure 4b It shows that the method of the present invention can accurately filter out the multipath noise that suddenly appears inside the room. From the simulation results, it can be seen that the present invention can effectively remove the false alarm caused by the multipath signal that suddenly appears indoors, reduce the error generated when using millimeter wave radar for crowd counting, and make the crowd counting result more accurate.

[0082] In the technical solution of the present invention, the data obtained by the millimeter wave radar for detecting the indoor space is obtained, and the position and speed information of the indoor target detected at the current time t is parsed therefrom; the position information of the detected target at the current time t is predicted based on the stored path information and speed information of the detected target; when it is determined that the predicted position information of a detected target matches the position information of an indoor target detected at the current time t, the indoor target detected at the current time t is confirmed as the detected target. The present invention can optimally estimate the state of the target (such as position, speed, etc.) through the prediction step, and then based on the judgment of path rationality, the accuracy and reliability of indoor target detection can be further improved;

[0083] More preferably, the technical solution of the present invention can also be combined with a life cycle algorithm to further improve the accuracy and reliability of indoor target detection.

[0084] Figure 5 The hardware architecture diagram of the computer device 1300 according to the indoor target detection method based on millimeter wave radar according to the embodiment of the present application is schematically shown. In this embodiment, the computer device 1300 is a device that can automatically perform numerical calculations and / or information processing according to pre-set or stored instructions. For example, it can be a smart phone, a tablet computer, a laptop computer, a desktop computer, a rack server, a blade server, a tower server or a cabinet server (including an independent server, or a server cluster composed of multiple servers), etc. Figure 5 As shown, the computer device 1300 includes at least but is not limited to: a memory 1310, a processor 1320, and a network interface 1330 which can communicate with each other via a system bus. Among them:

[0085] The memory 1310 includes at least one type of computer-readable storage medium, and the readable storage medium includes a flash memory, a hard disk, a multimedia card, a card-type memory (e.g., an SD or DX memory, etc.), a random access memory (RAM), a static random access memory (SRAM), a read-only memory (ROM), an electrically erasable programmable read-only memory (EEPROM), a programmable read-only memory (PROM), a magnetic memory, a magnetic disk, an optical disk, etc. In some embodiments, the memory 1310 may be an internal storage module of the computer device 1300, such as a hard disk or a memory of the computer device 1300. In other embodiments, the memory 1310 may also be an external storage device of the computer device 1300, such as a plug-in hard disk equipped on the computer device 1300, a smart memory card (Smart Media Card, referred to as SMC), a secure digital (Secure Digital, referred to as SD) card, a flash card, etc. Of course, the memory 1310 may also include both the internal storage module of the computer device 1300 and its external storage device. In this embodiment, the memory 1310 is generally used to store an operating system and various application software installed on the computer device 1300, such as program code of an indoor target detection method based on millimeter wave radar, etc. In addition, the memory 1310 can also be used to temporarily store various data that have been output or will be output.

[0086] In some embodiments, the processor 1320 may be a central processing unit (CPU), a controller, a microcontroller, a microprocessor, or other data processing chip. The processor 1320 is generally used to control the overall operation of the computer device 1300, such as performing control and processing related to data interaction or communication with the computer device 1300. In this embodiment, the processor 1320 is used to run the program code stored in the memory 1310 or process data.

[0087] The network interface 1330 may include a wireless network interface or a wired network interface, and the network interface 1330 is generally used to establish a communication link between the computer device 1300 and other computer devices. For example, the network interface 1330 is used to connect the computer device 1300 to an external terminal through a network, and to establish a data transmission channel and a communication link between the computer device 1300 and the external terminal. The network may be a wireless or wired network such as an intranet, the Internet, the Global System of Mobile communication (GSM), Wideband Code Division Multiple Access (WCDMA), 4G network, 5G network, Bluetooth, Wi-Fi, etc.

[0088] It should be pointed out that Figure 5 Only a computer device having components 1310 - 1330 is shown, but it should be understood that implementing all of the components shown is not a requirement, and more or fewer components may alternatively be implemented.

[0089] In this embodiment, the millimeter-wave radar-based indoor target detection method stored in the memory 1310 can also be divided into one or more program modules and executed by one or more processors (processor 1320 in this embodiment) to complete the embodiment of the present application.

[0090] The computer-readable medium of this embodiment includes permanent and non-permanent, removable and non-removable media, and information storage can be implemented by any method or technology. Information can be computer-readable instructions, data structures, modules of programs, or other data. Examples of computer storage media include, but are not limited to, phase change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technology, read-only compact disk read-only memory (CD-ROM), digital versatile disk (DVD) or other optical storage, magnetic cassettes, magnetic tape magnetic disk storage or other magnetic storage devices or any other non-transmission media that can be used to store information that can be accessed by a computing device.

[0091] Those skilled in the art should understand that the discussion of any of the above embodiments is merely illustrative and is not intended to imply that the scope of the present disclosure (including the claims) is limited to these examples. Within the scope of the present invention, the above embodiments or technical features in different embodiments may be combined, the steps may be implemented in any order, and there are many other variations of the different aspects of the present invention as described above, which are not provided in detail for the sake of simplicity.

[0092] In addition, to simplify the description and discussion, and in order not to obscure the present invention, known power / ground connections to integrated circuit (IC) chips and other components may or may not be shown in the provided figures. In addition, the devices may be shown in the form of block diagrams to avoid obscuring the present invention, and this also takes into account the fact that the details of the implementation of these block diagram devices are highly dependent on the platform on which the present invention will be implemented (i.e., these details should be fully within the scope of understanding of those skilled in the art). Where specific details (e.g., circuits) are set forth to describe exemplary embodiments of the present invention, it will be apparent to those skilled in the art that the present invention may be implemented without these specific details or with variations in these specific details. Therefore, these descriptions should be considered illustrative rather than restrictive.

[0093] Although the invention has been described in conjunction with specific embodiments of the invention, many replacements, modifications and variations of these embodiments will be apparent to those skilled in the art from the foregoing description. For example, other memory architectures (e.g., dynamic RAM (DRAM)) may use the embodiments discussed.

[0094] The embodiments of the present invention are intended to cover all such substitutions, modifications and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for indoor target detection based on millimeter wave radar, characterized in that: include: Obtain the data obtained by the millimeter-wave radar for detecting the indoor space, and parse the position and speed information of the indoor target detected at the current time t; Predict the position information of the detected target at the current time t based on the stored path information and speed information of the detected target; When it is determined that the predicted position information of a detected target matches the position information of an indoor target detected at the current time t, the indoor target detected at the current time t is confirmed as the detected target.

2. The method according to claim 1, characterized in that Also includes: The detection state of the detected target at time t is set to detected.

3. The method according to claim 2, characterized in that Also includes: According to the position and speed information of the indoor target detected at the current time t, the path information and speed information of the detected target are updated.

4. The method according to claim 3, characterized in that Also includes: If the position information of an indoor target detected at the current time t does not match the predicted position information of any detected target, then: For the indoor target detected at the current time t, detection of entering and exiting the indoor space is performed; If it is determined that the indoor target enters the room, the indoor target detected at the current time t is taken as a new detected target, and the path information and speed information of the new detected target are created based on the position and speed information of the indoor target detected at the current time t.

5. The method according to claim 4, characterized in that Also includes: If it is determined that the indoor target has not entered the indoor space, the indoor target is defined as a false alarm, and its path information is not retained.

6. The method according to claim 3, characterized in that Also includes: If the predicted position information of a detected target does not match the position information of any indoor target detected at the current time t, then: Performing detection of entering and exiting the indoor space according to the path information of the detected target; If it is determined that the detected target leaves the room, the path information of the detected target is cleared.

7. The method according to claim 6, characterized in that Also includes: If it is determined that the detected target has not left the room, the detection status of the detected target at time t is set to missed detection.

8. The method according to claim 6, characterized in that Also includes: Counting the number of times the detected target is in a missed detection state or detected state at each moment; If the counted missed detection times are greater than the detected times, the path information of the detected target is cleared.

9. A computer device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the computer program, it is used to implement the steps of the indoor target detection method based on millimeter wave radar as described in any one of claims 1 to 6.

10. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a computer program, and the computer program can be executed by at least one processor so that the at least one processor performs the steps of the indoor target detection method based on millimeter-wave radar as described in any one of claims 1 to 6.

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