Radar device, scan correlation processing method, and scan correlation processing program

Abstract

In radar systems that perform scan correlation processing, sea surface clutter is suppressed more reliably. [Solution] The radar device includes a transmitting unit that transmits radio waves to a detection target area, a receiving unit that receives reflected waves, a calculation unit that calculates the Doppler velocity width of the reflection position of the reflected waves, and a scan correlation unit that performs scan correlation processing of the second reflected wave received at a second time after the first time using the first reflected wave received at a first time, performs weighted addition of the intensity of the second reflected wave and the intensity of the first reflected wave after the scan correlation processing in the scan correlation processing of the second reflected wave, and changes the weighting coefficient used for the weighted addition based on the degree of variation of the Doppler velocity width between a plurality of scans.

Description

Technical Field

[0001] The present disclosure relates to a radar device, a scan correlation processing method, and a scan correlation processing program.

Background Art

[0002] Conventionally, in a radar device, techniques for suppressing clutter by performing scan correlation processing have been developed. For example, Patent Document 1 (Japanese Patent Application Laid-Open No. 2014-29284) discloses a detection image generation device as follows. That is, the detection image generation device includes a reception unit that generates echo data from a reception signal based on a detection signal, a speed detection unit that detects a speed based on the echo data at a target position, and a current echo data at the target position and the previous scan correlation processing data at the target position are weighted and added to calculate the current scan correlation processing data at the target position, and an image data generation unit that generates detection image data from the current scan correlation processing data, and the weighting is determined using the speed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Beyond the technology described in Patent Document 1, a technology that can more reliably suppress sea clutter in a radar device that performs scan correlation processing is desired.

[0005] The present disclosure has been made to solve the above problems, and an object thereof is to provide a radar device, a scan correlation processing method, and a scan correlation processing program that can more reliably suppress sea clutter in a radar device that performs scan correlation processing. [Means for solving the problem]

[0006] (1) The radar device of the present disclosure is a radar device for detecting a target in a detection target area, comprising: a transmitting unit that transmits radio waves to the detection target area; a receiving unit that receives reflected waves from the radio waves reflected in the detection target area; a calculation unit that calculates the Doppler velocity width of the reflection position of the reflected waves based on the phase of the reflected waves; and a scan correlation unit that performs scan correlation processing of a second reflected wave received at a second time after the first time using a first reflected wave received at a first time, and in the scan correlation processing of the second reflected wave, performs weighted addition of the intensity of the second reflected wave and the intensity of the first reflected wave after the scan correlation processing, and changes the weighting coefficient used for the weighted addition based on the degree of variation of the Doppler velocity width between a plurality of scans.

[0007] Thus, in scan correlation processing, by configuring the system to vary the weighting coefficients used for weighted addition based on the degree of variation in Doppler velocity width between multiple scans, it is possible to vary the weighting coefficients assigned to the intensity of the first reflected wave and the weighting coefficients assigned to the intensity of the second reflected wave according to the occurrence of sea surface clutter, etc. Therefore, by scan correlation processing, for example, the intensity of sea surface clutter can be suppressed relative to the intensity of the reflected wave at the detection target. Consequently, sea surface clutter can be suppressed more reliably in radar equipment that performs scan correlation processing.

[0008] (2) In (1) above, the scan correlation unit may further vary the weighting coefficient based on the relative magnitudes of the intensity of the first reflected wave and the intensity of the second reflected wave.

[0009] This configuration allows for increasing or decreasing the intensity of the weighted reflected wave obtained through scan correlation processing.

[0010] (3) In (2) above, the scan correlation unit may increase the weighting coefficient given to the intensity of the second reflected wave as the degree of variation increases when the intensity of the second reflected wave is less than the intensity of the first reflected wave, and the scan correlation unit may decrease the weighting coefficient given to the intensity of the second reflected wave as the degree of variation increases when the intensity of the second reflected wave is equal to or greater than the intensity of the first reflected wave.

[0011] This configuration allows for a smaller weighting coefficient to be applied to the higher intensity of the first and second reflected waves, and a larger weighting coefficient to the lower intensity of the first and second reflected waves, when the reflected waves are likely to be sea surface clutter. This makes it more difficult to reflect the intensity of sea surface clutter in the reflected wave intensity after weighting.

[0012] (4) In any of (1) to (3) above, the scan correlation unit may determine the weighting coefficient such that, if the degree of variation between a plurality of consecutive scans is less than a predetermined value, the sum of the weighting coefficient multiplied by the intensity of the second reflected wave and the weighting coefficient multiplied by the intensity of the first reflected wave after the scan correlation processing is greater than 1.

[0013] With this configuration, the intensity of reflected waves at the detection target can be increased through scan correlation processing. Therefore, based on the echo data obtained through scan correlation processing, it is possible to generate an echo image in which the detection target is enhanced against sea surface clutter.

[0014] (5) The scan correlation processing method of the present disclosure is a scan correlation processing method for a radar device that detects a target in a detection target area, comprising: transmitting radio waves to the detection target area; receiving reflected waves from the radio waves reflected in the detection target area; calculating the Doppler velocity width of the reflection position of the reflected waves based on the phase of the reflected waves; performing scan correlation processing of the second reflected wave received at a second time after the first time using the first reflected wave received at a first time; performing weighted addition of the intensity of the second reflected wave and the intensity of the first reflected wave after the scan correlation processing in the scan correlation processing of the second reflected wave; and changing the weighting coefficient used in the weighted addition based on the degree of variation of the Doppler velocity width between a plurality of scans.

[0015] Thus, in scan correlation processing, by varying the weighting coefficient used for weighted addition based on the degree of variation in Doppler velocity width between multiple scans, the weighting coefficients assigned to the intensity of the first reflected wave and the weighting coefficients assigned to the intensity of the second reflected wave can be varied according to the occurrence of sea surface clutter, etc. Therefore, by scan correlation processing, for example, the intensity of sea surface clutter can be suppressed relative to the intensity of reflected waves at the detection target. Consequently, sea surface clutter can be suppressed more reliably in radar equipment that performs scan correlation processing.

[0016] (6) The scan correlation processing program of the present disclosure is a scan correlation processing program for a radar device that detects a target in a detection target area, and is a program that causes a computer to perform the following: a process of transmitting radio waves to the detection target area; a process of receiving reflected waves that have been reflected by the radio waves in the detection target area; a process of calculating the Doppler velocity width of the reflection position of the reflected waves based on the phase of the reflected waves; a process of performing scan correlation processing of a second reflected wave received at a second time after the first time using the first reflected wave received at a first time; a process of performing weighted addition of the intensity of the second reflected wave and the intensity of the first reflected wave after the scan correlation processing in the scan correlation processing of the second reflected wave; and a process of changing the weighting coefficient used for the weighted addition based on the degree of variation of the Doppler velocity width between a plurality of scans.

[0017] Thus, in scan correlation processing, by configuring the system to vary the weighting coefficients used for weighted addition based on the degree of variation in Doppler velocity width between multiple scans, it is possible to vary the weighting coefficients assigned to the intensity of the first reflected wave and the weighting coefficients assigned to the intensity of the second reflected wave according to the occurrence of sea surface clutter, etc. Therefore, by scan correlation processing, for example, the intensity of sea surface clutter can be suppressed relative to the intensity of the reflected wave at the detection target. Consequently, sea surface clutter can be suppressed more reliably in radar equipment that performs scan correlation processing. [Effects of the Invention]

[0018] According to this disclosure, a radar system that performs scan correlation processing can more reliably suppress sea surface clutter. [Brief explanation of the drawing]

[0019] [Figure 1] Figure 1 is a diagram showing the configuration of a radar device according to an embodiment of the present disclosure. [Figure 2]FIG. 2 is a diagram showing an example of a detection target area of a radar device according to an embodiment of the present disclosure. [Figure 3] FIG. 3 is a diagram showing an example of a coefficient of variation calculated by a signal processing unit in a radar device according to an embodiment of the present disclosure. [Figure 4] FIG. 4 is a diagram showing an example of a detection target flag given by a signal processing unit in a radar device according to an embodiment of the present disclosure. [Figure 5] FIG. 5 is a diagram showing an example of coefficient information stored in a storage unit in a radar device according to an embodiment of the present disclosure. [Figure 6] FIG. 6 is a diagram showing an example of coefficient information stored in a storage unit in a radar device according to an embodiment of the present disclosure. [Figure 7] FIG. 7 is a flowchart showing an operation procedure when a radar device according to an embodiment of the present disclosure displays an echo image. [Figure 8] FIG. 8 is a flowchart showing an operation procedure when a radar device according to an embodiment of the present disclosure performs scan correlation processing. [Figure 9] FIG. 9 is a flowchart showing an operation procedure when a radar device according to an embodiment of the present disclosure assigns a detection target flag.

MODE FOR CARRYING OUT THE INVENTION

[0020] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and their descriptions will not be repeated. Also, at least a part of the embodiments described below may be arbitrarily combined.

[0021] [Configuration and Basic Operation] Figure 1 shows the configuration of a radar device according to an embodiment of the present disclosure. Referring to Figure 1, the radar device 101 comprises a transmitting unit 11, a transmitting antenna 12, a receiving antenna 13, a receiving unit 14, a signal processing unit 15, a display processing unit 16, and a storage unit 17. The radar device 101 is mounted on a ship 1. The signal processing unit 15 is an example of a calculation unit and an example of a scan correlation unit. Some or all of the transmitting unit 11, the receiving unit 14, the signal processing unit 15, and the display processing unit 16 are implemented by a processing circuit (Circuitry) including, for example, one or more processors. The storage unit 17 is, for example, a non-volatile memory included in the above-mentioned processing circuit.

[0022] The radar device 101 is, for example, a pulse-type radar. However, the radar device 101 is not limited to a pulse-type radar; it may also be a radar of a different type, such as an FM-CW (Frequency Modulated Continuous Wave) type.

[0023] Figure 2 shows an example of a detection area of ​​a radar device according to an embodiment of the present disclosure. Referring to Figure 2, the radar device 101 detects targets S such as other ships and land L in the detection area Ta. For example, the detection area Ta is the area inside a circle of a predetermined size centered on the ship 1. In the example shown in Figure 2, the detection area Ta includes land L and a stationary target S. The radar device 101 processes an echo image showing the positions of the detected targets S and land L and displays it on a display device (not shown).

[0024] (Transmission of radio waves and reception of reflected waves) Referring again to Figure 1, the transmitting unit 11 transmits radio waves to the detection target area Ta. More specifically, the transmitting unit 11 transmits pulsed radio waves via the transmitting antenna 12 during a sweep period St of a predetermined length.

[0025] The receiving unit 14 receives the reflected wave Rw that is reflected from the radio waves transmitted by the transmitting unit 11 in the detection target area Ta. More specifically, the receiving unit 14 receives the reflected wave Rw via the receiving antenna 13 during the sweep period St. The receiving unit 14 generates a digital reflected signal Ds1 by digitally converting the echo signal indicating the received reflected wave Rw, and outputs the generated digital reflected signal Ds1 to the signal processing unit 15. The receiving unit 14 generates a digital reflected signal Ds1 based on the received reflected wave Rw for each sweep period St and outputs it to the signal processing unit 15.

[0026] The transmitting antenna 12 rotates so that the azimuth angle of the radio wave transmission direction changes by a predetermined angle with each sweep period St. The receiving antenna 13 rotates together with the transmitting antenna 12 so that the azimuth angle of the sensitivity direction changes by a predetermined angle with each sweep period St. Hereinafter, the rotation direction of the transmitting antenna 12 and the receiving antenna 13 will also be referred to as the "azimuth direction," and the direction away from the radar device 101 will also be referred to as the "distance direction." The operation of rotating the receiving antenna 13 360 degrees to receive the reflected wave Rw will also be referred to as "scanning." The azimuth angle of the sensitivity direction of the receiving antenna 13 will also be referred to as the "azimuth angle θw."

[0027] (Calculation of Doppler velocity width Dw and clutter fit Dc1) The signal processing unit 15 calculates the Doppler velocity width Dw of the reflection position Rp of the reflected wave Rw based on the phase of the reflected wave Rw.

[0028] More specifically, the signal processing unit 15 receives a digital reflected signal Ds1 from the receiving unit 14 and calculates the phase difference of the reflected wave Rw during two consecutive sweep periods St based on the received digital reflected signal Ds1 and the digital reflected signal Ds1 received from the receiving unit 14 immediately prior to the said digital reflected signal Ds1. Based on the calculated phase difference, the signal processing unit 15 calculates the Doppler velocity width Dw of multiple reflection positions Rp at an azimuth angle θw.

[0029] Furthermore, the signal processing unit 15 calculates a clutter fit score Dc1, which is an indicator of the likelihood that the reflected wave Rw at the calculated reflection position Rp is sea surface clutter, by applying a membership function F1 to the Doppler velocity width Dw of the calculated reflection position Rp. The clutter fit score Dc1 is, for example, a value within the range of zero to 1.

[0030] The signal processing unit 15 stores the calculated Doppler velocity width Dw and clutter fit Dc1 in the storage unit 17, in association with the scan timing, azimuth angle θw, and reflection position Rp.

[0031] Furthermore, the signal processing unit 15 generates echo data D1 based on the digital reflection signal Ds1, which shows the correspondence between multiple reflection positions Rp at an azimuth angle θw and the intensity Ain of the reflected wave Rw at each reflection position Rp. The signal processing unit 15 stores the generated echo data D1 in the storage unit 17, associating it with the scan timing and azimuth angle θw.

[0032] (Calculation of the coefficient of variation Cv and the clutter fit Dc2) The signal processing unit 15 calculates a coefficient of variation Cv, which indicates the degree of variation in the Doppler velocity width Dw between multiple scans. More specifically, the signal processing unit 15 calculates the Doppler velocity width Dw of the reflection position Rp and stores it in the storage unit 17, and then retrieves the Doppler velocity width Dw of the reflection position Rp for the most recent N scans from the storage unit 17. Then, the signal processing unit 15 calculates the coefficient of variation Cv of the Doppler velocity width Dw between N scans for each reflection position Rp according to the following equation (1). Here, N is an integer of 2 or more.

number

[0033] Here, the standard deviation σ and the mean μ are expressed by equations (2) and (3), respectively.

number

number

[0034] Here, Dwi represents the Doppler velocity width Dw in the i-th scan out of N scans.

[0035] For example, the signal processing unit 15 performs an averaging process in which it averages the calculated coefficient of variation Cv of the reflection position Rp using the coefficient of variation Cv of the reflection position Rp corresponding to the most recent M scans. Here, M is an integer of 2 or greater. Furthermore, for example, the signal processing unit 15 performs a filtering process using a median filter on the coefficient of variation Cv after the averaging process.

[0036] The signal processing unit 15 calculates a clutter fit score Dc2, which is an indicator of the likelihood that the reflected wave Rw at the reflection position Rp is sea surface clutter, by applying a membership function F2 to the coefficient of variation Cv of the reflection position Rp after filtering. The clutter fit score Dc2 is, for example, a value within the range of zero to 1.

[0037] Figure 3 shows an example of a coefficient of variation calculated by the signal processing unit in a radar device according to an embodiment of the present disclosure. In Figure 3, the hatched area is the area where the coefficient of variation Cv is greater than or equal to a predetermined value and the clutter fit Dc2 is greater than or equal to a predetermined value.

[0038] The signal processing unit 15 stores the calculated coefficient of variation Cv and clutter fit Dc2 in the storage unit 17, in association with the scan timing, azimuth angle θw, and reflection position Rp.

[0039] (Assignment of detection target flag fg) The signal processing unit 15 refers to the storage unit 17 and compares the clutter fit indices Dc1 and Dc2 for the reflection position Rp in the same scan, and determines the larger of the two clutter fit indices Dc1 and Dc2 as the clutter fit indices Dcmax. The signal processing unit 15 stores the determined clutter fit indices Dcmax in the storage unit 17, associating it with the scan timing, azimuth angle θw, and reflection position Rp.

[0040] The signal processing unit 15 detects, for example, at a processing timing according to the scan cycle, a reflection position Rp in the detection target area Ta from among multiple reflection positions Rp, where the clutter fit Dcmax consistently takes a low value. The signal processing unit 15 assigns a 1-bit detection target flag fg to the detected reflection position Rp, indicating that a stationary detection target exists.

[0041] More specifically, the signal processing unit 15 refers to the storage unit 17 and performs a comparison process to compare the clutter fit Dcmax with a predetermined threshold ThDc for each reflection position Rp. If, among the L clutter fit Dcmax values ​​corresponding to each of the most recent L scans of the reflection position Rp, K or more clutter fit Dcmax values ​​are less than the threshold ThDc, the signal processing unit 15 assigns a detection target flag fg indicating "1" to the reflection position Rp. Here, L is an integer greater than or equal to 2. K is an integer greater than or equal to 2 and less than or equal to L.

[0042] On the other hand, the signal processing unit 15 assigns a detection target flag fg indicating "zero" to the reflection position Rp if, among the L clutter fitness Dcmax values ​​for the reflection position Rp corresponding to each of the most recent consecutive L scans, there are fewer than K clutter fitness Dcmax values ​​that are less than the threshold ThDc.

[0043] Once the signal processing unit 15 has completed the comparison process for all reflection positions Rp in the detection target area Ta, it performs a filtering process using a minimum value filter on the detection target flag fg for each reflection position Rp. This allows the detection target flag fg for reflection positions Rp that were incorrectly determined to have a detection target based on the clutter fit score Dcmax, even though no detection target exists, to be replaced with "zero".

[0044] The signal processing unit 15 performs a restoration process on the detected target flag fg after filtering to expand the region where the detected target flag fg is "1". For example, the signal processing unit 15 performs an azimuth direction restoration process and a distance direction restoration process as part of the restoration process.

[0045] More specifically, in the azimuthal direction restoration process, the signal processing unit 15 counts the number of reflection positions Rp where the clutter fit Dcmax is less than a predetermined value among a plurality of reflection positions Rp aligned in the azimuthal direction from the reflection position Rp of interest, and performs an azimuthal direction comparison process by comparing the count value with a predetermined threshold Th1. If the count value is greater than or equal to the threshold Th1, the signal processing unit 15 replaces the clutter fit Dcmax of the plurality of reflection positions Rp with the smallest clutter fit Dcmax among the plurality of reflection positions Rp. The signal processing unit 15 repeatedly performs the azimuthal direction comparison process using the clutter fit Dcmax before replacement while shifting the reflection position Rp of interest, and terminates the azimuthal direction comparison process when it has performed the azimuthal direction comparison process for all reflection positions Rp.

[0046] Furthermore, in the distance direction reconstruction process, the signal processing unit 15 counts the number of reflection positions Rp where the clutter fit Dcmax is less than a predetermined value among a plurality of reflection positions Rp aligned in the distance direction from the reflection position Rp of interest, and performs a comparison process that compares the count value with a predetermined threshold Th2. If the count value is greater than or equal to the threshold Th2, the signal processing unit 15 replaces the clutter fit Dcmax of the plurality of reflection positions Rp with the smallest clutter fit Dcmax among the plurality of reflection positions Rp. The signal processing unit 15 repeats the comparison process using the clutter fit Dcmax before replacement while shifting the reflection position Rp of interest, and terminates the distance direction comparison process when the comparison process has been performed for all reflection positions Rp.

[0047] Figure 4 shows an example of a detection target flag assigned by the signal processing unit in a radar device according to an embodiment of the present disclosure. In Figure 4, the hatched area indicates the reflection position Rp where the detection target flag fg is "1" after the restoration process.

[0048] Referring to Figure 4, when the signal processing unit 15 finishes the restoration process, it updates the detection target flag fg for the reflection position Rp based on the clutter fit Dcmax of the reflection position Rp after the restoration process. In the example shown in Figure 4, the detection target flag fg for the reflection position Rp corresponding to the target S and the reflection position Rp corresponding to the land L is "1".

[0049] (Scan correlation processing) The signal processing unit 15 performs scan correlation processing on reflected wave Rw(m), which is the reflected wave Rw received in the m-th scan performed at time t2, using reflected wave Rw(m-1), which is the reflected wave Rw received in the (m-1)-th scan performed at time t1. Here, m is an integer greater than or equal to 2. Time t2 is a time later than time t1. Time t1 is an example of a first time. Time t2 is an example of a second time. Reflected wave Rw(m-1) is an example of a first reflected wave. Reflected wave Rw(m) is an example of a second reflected wave.

[0050] The signal processing unit 15 generates echo data D2 by performing a weighted summation of the reflected wave Rw(m) and the reflected wave Rw(m-1) after scan correlation processing for each reflection position Rp during scan correlation processing. Echo data D2 is the data obtained by scan correlation processing of echo data D1.

[0051] More specifically, the signal processing unit 15 generates echo data D1(m), which is echo data D1, based on the digital reflected signal Ds1 corresponding to the azimuth angle θw in the m-th scan, and then acquires echo data D1(m-1), which is echo data D1 corresponding to the (m-1)-th scan and the azimuth angle θw, from the storage unit 17. Using echo data D1(m-1), the signal processing unit 15 performs scan correlation processing on echo data D1(m) to generate echo data D2(m), which is echo data D2 corresponding to the azimuth angle θw in the m-th scan.

[0052] For example, the signal processing unit 15 performs weighted addition using different calculation formulas for reflection position Rpoff, which is a reflection position Rp where the detection target flag fg is off, and reflection position Rpon, which is a reflection position Rp where the detection target flag fg is on.

[0053] (1) Weighted addition of reflection position Rpoff The signal processing unit 15 extracts the intensity Ain corresponding to the reflection position Rpoff from the generated echo data D1(m). The intensity Ain extracted from the echo data D1(m) is an example of the intensity of the second reflected wave.

[0054] The signal processing unit 15 uses the extracted intensity Ain to calculate the weighted summed intensity Acor(m) corresponding to the reflection position Rpoff according to the following equation (4).

number

[0055] Here, Acor(m-1) is the intensity of the reflected wave Rw at the reflection position Rp, as indicated by echo data D2(m-1), which is the echo data D2 from the (m-1)th scan. Intensity Acor(m-1) is an example of the intensity of the first reflected wave after scan correlation processing. CoeA1 and CoeA2 are weighting coefficients used for weighted addition for the reflection position Rpoff. The weighting coefficient CoeA2 is (1-CoeA1). The signal processing unit 15 calculates intensity Acor(m) for each reflection position Rpoff according to equation (4) above.

[0056] The signal processing unit 15 varies the weighting coefficients CoeA1 and CoeA2 used for weighted summation for the reflection position Rpoff based on the coefficient of variation Cv of the reflection position Rpoff. The signal processing unit 15 further varies the weighting coefficients CoeA1 and CoeA2 based on the relative magnitudes of the intensity Ain of the reflected wave Rw(m) in echo data D1(m-1) and the intensity Ain of the reflected wave Rw(m-1) in echo data D1(m-1).

[0057] More specifically, the memory unit 17 stores coefficient information F that shows the correspondence between the clutter fitness score Dc2 and the weighting coefficients CoeA1 and CoeA2.

[0058] Figures 5 and 6 show examples of coefficient information stored in the memory unit of a radar device according to an embodiment of the present disclosure. Figure 5 shows coefficient information Frise used when the intensity Ain is on an upward trend. Figure 6 shows coefficient information Ffall used when the intensity Ain is on a downward trend. In Figures 5 and 6, the horizontal axis is the clutter fitness index Dc2, and the vertical axis is the weighting coefficient CoeA1.

[0059] Referring to Figures 5 and 6, the memory unit 17 stores coefficient information Frise and coefficient information Ffall as coefficient information F. In coefficient information Frise, the larger the clutter fitness Dc2, the larger the weighting coefficient CoeA1 and the smaller the weighting coefficient CoeA2. On the other hand, in coefficient information Ffall, the larger the clutter fitness Dc2, the smaller the weighting coefficient CoeA1 and the larger the weighting coefficient CoeA2.

[0060] For example, if the intensity Ain of the reflected wave Rw(m) is less than the intensity Ain of the reflected wave Rw(m-1), the signal processing unit 15 increases the weighting coefficient CoeA2 assigned to the intensity Ain of the reflected wave Rw(m) as the coefficient of variation Cv is higher. On the other hand, if the intensity Ain of the reflected wave Rw(m) is greater than or equal to the intensity Ain of the reflected wave Rw(m-1), the signal processing unit 15 decreases the weighting coefficient CoeA2 assigned to the intensity Ain of the reflected wave Rw(m) as the coefficient of variation Cv is higher.

[0061] More specifically, the signal processing unit 15 compares the intensity Ain corresponding to the reflection position Rpoff in the echo data D1(m) with the intensity Ain corresponding to the same reflection position Rpon in the echo data D1(m-1). The signal processing unit 15 also obtains the clutter fit Dc2 corresponding to the reflection position Rpoff from the storage unit 17.

[0062] The signal processing unit 15 determines weighting coefficients CoeA1 and CoeA2 using the coefficient information Ffall if the intensity Ain corresponding to the reflection position Rpoff in echo data D1(m) is less than the intensity Ain corresponding to the reflection position Rpon in echo data D1(m-1). Specifically, the signal processing unit 15 obtains the weighting coefficient CoeA1 corresponding to the clutter fit Dc2 by referring to the coefficient information Ffall. The signal processing unit 15 also determines the weighting coefficient CoeA2 to be the value obtained by subtracting the weighting coefficient CoeA1 from 1.

[0063] On the other hand, the signal processing unit 15 determines weighting coefficients CoeA1 and CoeA2 using the coefficient information Frise if the intensity Ain corresponding to the reflection position Rpoff in echo data D1(m) is greater than or equal to the intensity Ain corresponding to the reflection position Rpon in echo data D1(m-1). Specifically, the signal processing unit 15 obtains the weighting coefficient CoeA1 corresponding to the clutter fit Dc2 by referring to the coefficient information Frise. The signal processing unit 15 also determines the weighting coefficient CoeA2 to be the value obtained by subtracting the weighting coefficient CoeA1 from 1.

[0064] Then, the signal processing unit 15 uses the weighting coefficients CoeA1 and CoeA2 to calculate the intensity Acor(m) according to equation (4) described above.

[0065] (2) Weighted addition of reflection position Rpon The signal processing unit 15 extracts the intensity Ain corresponding to the reflection position Rpon from the generated echo data D1(m).

[0066] The signal processing unit 15 uses the extracted intensity Ain to calculate the weighted summed intensity Acor(m) corresponding to the reflection position Rpon according to the following equation (5).

number

[0067] Here, CoeB1 and CoeB2 are weighting coefficients used for weighted addition of the reflection position Rpon. The signal processing unit 15 calculates the intensity Acor(m) for each reflection position Rpon according to equation (5) above.

[0068] The signal processing unit 15 determines the weighting coefficients CoeB1 and CoeB2 such that the sum of the weighting coefficient CoeB1 multiplied by the intensity Acor(m-1) and the weighting coefficient CoeB2 multiplied by the intensity Ain is greater than 1, if the coefficient of variation Cv is less than a predetermined value between multiple consecutive scans.

[0069] More specifically, the signal processing unit 15 determines the weighting coefficients used in the weighted sum of the reflection position Rpon to be predetermined weighting coefficients CoeB1 and CoeB2 such that their sum is greater than 1. Then, the signal processing unit 15 uses these weighting coefficients CoeB1 and CoeB2 to calculate the intensity Acor(m) according to equation (5) described above.

[0070] (Display processing) Once the signal processing unit 15 has completed weighting and summing all reflection positions Rp in the echo data D1(m), it generates echo data D2(m) showing the correspondence between the reflection position Rp and the intensity Acor(m). The signal processing unit 15 outputs the generated echo data D2(m) to the display processing unit 16.

[0071] The display processing unit 16 receives echo data D2(m) from the signal processing unit 15 and generates an echo image based on the received echo data D2(m). The display processing unit 16 then displays the generated echo image on a display device (not shown).

[0072] [Operation Flow] The radar device according to the embodiment of this disclosure includes a computer including memory, and a processor such as a CPU in the computer reads and executes a program from the memory that includes some or all of the steps in the following flowchart. The program for this device can be installed externally. The program for this device is distributed either stored on a recording medium or via a communication line.

[0073] Figure 7 is a flowchart showing the operation procedure when a radar device according to an embodiment of the present disclosure displays an echo image. For example, the radar device 101 performs the process shown in Figure 7 for each sweep period St.

[0074] Referring to Figure 7, first, the radar device 101 transmits radio waves via the transmitting antenna 12 in the direction of the azimuth angle θw during the sweep period St (step S11).

[0075] Next, during the sweep period St, the radar device 101 receives the reflected wave arriving from the direction of azimuth angle θw via the receiving antenna 13 (step S12).

[0076] Next, the radar device 101 calculates the Doppler velocity width Dw and the clutter fit Dc1 of multiple reflection positions Rp at an azimuth angle θw (step S13).

[0077] Next, the radar device 101 calculates the coefficient of variation Cv of the Doppler velocity width Dw and the clutter fit Dc2 for each reflection position Rp over N scans (step S14).

[0078] Next, the radar device 101 generates echo data D2 corresponding to the azimuth angle θw by performing scan correlation processing (step S15).

[0079] Next, the radar device 101 generates an echo image based on the echo data D2 and performs a process to display the generated echo image (step S16).

[0080] Figure 8 is a flowchart showing the operation procedure of the radar device according to the embodiment of this disclosure when performing scan correlation processing. Figure 8 shows details of step S15 in Figure 7. The radar device 101 generates echo data D2 by performing the processing shown in Figure 8 for each reflection position Rp.

[0081] Referring to Figure 8, first, the radar device 101 checks the detection target flag fg of the reflection position Rp that is the target of the scan correlation processing, and determines whether the reflection position Rp is a reflection position Rpoff where the detection target flag fg is off, or a reflection position Rpon where the detection target flag fg is on (step S21).

[0082] Next, if the reflection position Rp is reflection position Rpoff (YES in step S22), the radar device 101 determines weighting coefficients CoeA1 and CoeA2 based on the clutter fit Dc2 and coefficient information F of the reflection position Rp (step S23).

[0083] Next, the radar device 101 calculates the intensity Acor(m) according to equation (4) described above, using the weighting coefficients CoeA1 and CoeA2 (step S24).

[0084] On the other hand, if the reflection position Rp is the reflection position Rpon (NO in step S22), the intensity Acor(m) is calculated according to equation (5) above using the pre-set weighting coefficients CoeB1 and CoeB2 (step S25).

[0085] Figure 9 is a flowchart showing the operation procedure when a radar device according to an embodiment of the present disclosure assigns a detection target flag. For example, the radar device 101 executes the process shown in Figure 9 at a processing timing according to the scan cycle.

[0086] Referring to Figure 9, first, the radar device 101 determines the larger of the clutter fit factors Dc1 and Dc2 as the clutter fit factor Dcmax for each reflection position Rp (step S31).

[0087] Next, the radar device 101 performs a comparison process to compare each clutter fit Dcmax with the threshold ThDc (step S32).

[0088] Next, the radar device 101 assigns a detection target flag fg to each reflection position Rp based on the comparison results in the comparison process. More specifically, the radar device 101 assigns a detection target flag fg indicating "1" to the reflection position Rp if the condition is met that K or more clutter fit Dcmax values ​​are less than the threshold ThDc among the L clutter fit Dcmax values ​​corresponding to each of the most recent L scans of the reflection position Rp. On the other hand, if the radar device 101 does not meet this condition, it assigns a detection target flag fg indicating "zero" to the reflection position Rp (step S33).

[0089] Next, the radar device 101 performs a filter operation using a minimum value filter on the detection target flag fg of each reflection position Rp (step S34).

[0090] Next, the radar device 101 performs a restoration process on the detected target flag fg after filtering (step S35).

[0091] In the radar device 101 according to the embodiment of this disclosure, the storage unit 17 is configured to store coefficient information F showing the correspondence between the clutter fitness Dc2 and the weighting coefficients CoeA1 and CoeA2, but it is not limited to this configuration. The storage unit 17 may also be configured to store coefficient information F showing the correspondence between the coefficient of variation Cv and the weighting coefficients CoeA1 and CoeA2 instead of the clutter fitness Dc2. In this case, the signal processing unit 15 determines the weighting coefficients CoeA1 and CoeA2 to be used in the weighting addition for the reflection position Rp based on the coefficient of variation Cv of the reflection position Rp and the coefficient information F.

[0092] Furthermore, in the radar device 101 according to the embodiment of this disclosure, the signal processing unit 15 may, in addition to scan correlation processing, perform processing to correct the intensity Ain of the reflected wave Rw based on at least one of the detection target flag fg and clutter fitness Dc1, Dc2. Specifically, the signal processing unit 15 may increase the intensity Ain of the reflected wave Rw at a reflection position Rp where the detection target flag fg is on by multiplying or adding a predetermined value to the intensity Ain of the reflected wave Rw. Alternatively, the signal processing unit 15 may decrease the intensity Ain of the reflected wave Rw at a reflection position Rp where the clutter fitness Dc1, Dc2 is equal to or greater than a predetermined value by subtracting a predetermined value from the intensity Ain of the reflected wave Rw, or by replacing the intensity Ain with zero.

[0093] The embodiments described above should be considered in all respects to be illustrative and not restrictive. The scope of the present invention is indicated by the claims rather than the above description, and all modifications within the meaning and scope equivalent to the claims are intended to be included. [Explanation of symbols]

[0094] 1 ship 11 Transmitter 12 Transmitting Antennas 13 Receiving antenna 14 Receiving Unit 15 Signal Processing Unit 16 Display Processing Unit 17 Memory section 101 Radar equipment Ta detection target area S target L land

Claims

1. A radar device for detecting targets in a target area, A transmitting unit that transmits radio waves to the detection target area, A receiving unit that receives reflected waves reflected in the detection target area of ​​the aforementioned radio waves, A calculation unit that calculates the Doppler velocity width of the reflection position of the reflected wave based on the phase of the reflected wave, A radar device comprising: a scan correlation unit that uses the first reflected wave received at a first time to perform scan correlation processing on the second reflected wave received at a second time later than the first time; performs weighted addition of the intensity of the second reflected wave and the intensity of the first reflected wave after the scan correlation processing in the scan correlation processing of the second reflected wave; and varies the weighting coefficient used in the weighted addition based on the degree of variation of the Doppler velocity width between a plurality of scans.

2. The radar apparatus according to claim 1, wherein the scan correlation unit further varies the weighting coefficient based on the relative magnitudes of the intensity of the first reflected wave and the intensity of the second reflected wave.

3. The scan correlation unit, when the intensity of the second reflected wave is less than the intensity of the first reflected wave, increases the weighting coefficient assigned to the intensity of the second reflected wave as the degree of variation increases. The radar apparatus according to claim 2, wherein the scan correlation unit, when the intensity of the second reflected wave is greater than or equal to the intensity of the first reflected wave, reduces the weighting coefficient given to the intensity of the second reflected wave as the degree of variation increases.

4. The radar apparatus according to any one of claims 1 to 3, wherein the scan correlation unit determines the weighting coefficient such that, when the degree of variation between a plurality of consecutive scans is less than a predetermined value, the sum of the weighting coefficient multiplied by the intensity of the second reflected wave and the weighting coefficient multiplied by the intensity of the first reflected wave after the scan correlation processing is greater than 1.

5. A scan correlation processing method for a radar device that detects targets in a target area, A radio wave is transmitted to the aforementioned detection target area, The radio waves are received from the reflected waves that have been reflected in the detection target area. Based on the phase of the reflected wave, the Doppler velocity width of the reflection position of the reflected wave is calculated. A scan correlation processing method comprising: performing scan correlation processing on a second reflected wave received at a second time after the first time using a first reflected wave received at a first time; performing weighted addition of the intensity of the second reflected wave and the intensity of the first reflected wave after the scan correlation processing in the scan correlation processing of the second reflected wave; and varying the weighting coefficient used in the weighted addition based on the degree of variation of the Doppler velocity width between a plurality of scans.

6. A scan correlation processing program for a radar device that detects targets in a target area, The process of transmitting radio waves to the detection target area, The process of receiving the reflected wave that was reflected in the detection target area of ​​the aforementioned radio wave, A process for calculating the Doppler velocity width of the reflection position of the reflected wave based on the phase of the reflected wave, A scan correlation processing program for causing a computer to perform scan correlation processing on a second reflected wave received at a second time after the first time, using a first reflected wave received at a first time; performing weighted addition of the intensity of the second reflected wave and the intensity of the first reflected wave after the scan correlation processing in the scan correlation processing of the second reflected wave; and changing the weighting coefficient used in the weighted addition based on the degree of variation of the Doppler velocity width between multiple scans.

Images