Clutter suppression apparatus and clutter suppression program

Abstract

To set parameters for clutter suppression processing for sweep data in a fully automatic manner without using a manual knob, regardless of presence or absence of a skilled sensation when suppressing clutter and recognizing a target using a radar.SOLUTION: Provided is a clutter suppression apparatus 2 that suppresses clutter and recognizes a target using a radar. The clutter suppression apparatus 2 comprises a parameter setting part 21 that, for sweep data "before clutter suppression", sets parameters for clutter suppression processing such that a clutter suppression effect becomes higher / lower as a "distribution length" of clutter from a position of a radar transmission / reception apparatus 1 as a starting point is longer / shorter; and a clutter suppression part 22 that suppresses clutter and recognizes a target on the basis of the parameters for clutter suppression processing set by the parameter setting part 21 for the sweep data "before clutter suppression".SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a technique for suppressing clutter and recognizing targets using radar. [Background technology]

[0002] A technology for suppressing clutter such as sea surface clutter or rain and snow clutter and recognizing targets such as ships or aircraft using radar mounted on ships or aircraft is disclosed in Patent Document 1. Patent Document 1 implements OS-CFAR (Order Statistic-Constant False Alarm Rate) or CA-CFAR (Cell-Averaging-Constant False Alarm Rate).

[0003] Here, in a situation where sea surface waves are high or rain and snow are heavy, the parameters of the clutter suppression process are automatically set so that the clutter suppression effect is high, and clutter is suppressed and targets are recognized based on the parameters of the clutter suppression process. On the other hand, in a situation where sea surface waves are low or rain and snow are light, the parameters of the clutter suppression process are automatically set so that the clutter suppression effect is low, and clutter is suppressed and targets are recognized based on the parameters of the clutter suppression process. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-170287 Summary of the Invention [Problem to be solved by the invention]

[0005] The issues with clutter suppression processing in the prior art are shown in Figure 1. In Figure 1, for radar image R, parameters for clutter suppression processing are automatically set regardless of the sweep direction.

[0006] As a result, in the left column of Figure 1, when the sea surface waves are high or there is heavy rain or snow, the clutter suppression effect in a certain sweep direction may be too low, resulting in clutter not being completely eliminated.On the other hand, in the right column of Figure 1, when the sea surface waves are low or there is light rain or snow, the clutter suppression effect in a certain sweep direction may be too high, resulting in targets being completely eliminated.

[0007] Therefore, for the radar image R, the parameters for the clutter suppression processing for each sweep direction must be set semi-automatically using the manual knob with an experienced sense; without an experienced sense, it is difficult to set semi-automatically using the manual knob, and in any case, it is not possible to set them fully automatically.

[0008] Therefore, in order to solve the above-mentioned problems, an object of the present disclosure is to fully automatically set parameters for clutter suppression processing of sweep data when using a radar to suppress clutter and recognize targets, without using manual knobs and regardless of whether the operator is skilled or not. [Means for solving the problem]

[0009] To solve the above problem, we focused on the fact that the clutter "distribution length" of the sweep data "before clutter suppression" is long / short when the sea surface waves are high / low or when there is heavy / weak rain / snow. Therefore, we set the parameters of the clutter suppression process so that the clutter suppression effect is higher / lower as the clutter "distribution length" of the sweep data "before clutter suppression" is longer / shorter, thereby suppressing clutter and recognizing targets.

[0010] Specifically, the present disclosure provides a clutter suppression device that uses a radar to suppress clutter and recognize targets, the clutter suppression device comprising: a parameter setting unit that sets parameters for clutter suppression processing so that the clutter suppression effect increases / decreases as the clutter distribution length starting from the position of the radar increases / decreases, respectively, for sweep data before clutter suppression; and a clutter suppression unit that suppresses clutter based on the parameters for clutter suppression processing set by the parameter setting unit for the sweep data before clutter suppression.

[0011] According to this configuration, the parameters for the clutter suppression process for the sweep data can be set completely automatically without using manual knobs, regardless of whether the user has a high level of experience.

[0012] The present disclosure also provides a clutter suppression device, wherein the parameter setting unit sets parameters for clutter suppression processing for each sweep direction for sweep data for each direction before clutter suppression, and the clutter suppression unit suppresses clutter for the sweep data for each direction before clutter suppression based on the parameters for clutter suppression processing for each sweep direction.

[0013] According to this configuration, the parameters of the clutter suppression process for each sweep direction can be set completely automatically without using manual knobs, regardless of whether the operator is experienced or not.

[0014] The present disclosure also provides a clutter suppression device, characterized in that the parameter setting unit sets parameters for clutter suppression processing for sweep data of a first system before clutter suppression while the radar is in constant operation, and the clutter suppression unit suppresses clutter based on the parameters for clutter suppression processing for sweep data of a second system before clutter suppression, which is separate from the sweep data of the first system before clutter suppression while the radar is in constant operation.

[0015] With this configuration, after the parameters for the clutter suppression process are set in the initial stage of radar operation, even if the environment, such as the sea surface or rain / snow, changes during regular radar operation, the parameters for the clutter suppression process can be adapted to the environmental changes.

[0016] The present disclosure also provides a clutter suppression device, characterized in that the parameter setting unit sets parameters for clutter suppression processing for sweep data of a first system before clutter suppression at an early stage of operation of the radar, and the clutter suppression unit suppresses clutter for sweep data of the first system before clutter suppression at all times during operation of the radar, based on parameters for clutter suppression processing that are the same as the parameters set at the early stage of operation of the radar.

[0017] According to this configuration, after the parameters for the clutter suppression process are set at the beginning of radar operation, the parameters for the clutter suppression process can be maintained at the initial settings during normal radar operation as long as there are no changes in the environment, such as the sea surface or rain / snow.

[0018] The present disclosure also provides a clutter suppression device, characterized in that the parameter setting unit sets, for the sweep data before clutter suppression, parameters for the clutter suppression process, such as which of the intensity of the reference cells surrounding the cell of interest to extract, a multiplication coefficient for that intensity, and an upper limit value for the multiplication value of that intensity and that coefficient, and the clutter suppression unit (1) when the multiplication value is larger than the upper limit value and the intensity of the cell of interest is larger / smaller than the upper limit value, maintains the intensity of the cell of interest as is / suppresses it as clutter, and (2) when the multiplication value is smaller than the upper limit value and the intensity of the cell of interest is larger / smaller than the multiplication value, maintains the intensity of the cell of interest as is / suppresses it as clutter.

[0019] According to this configuration, by setting an upper limit value when executing OS-CFAR, it is possible to prevent erroneous removal of targets, and it is also possible to set the OS-CFAR parameters fully automatically without using manual knobs, regardless of whether the operator has experience or not.

[0020] The present disclosure also provides a clutter suppression device, characterized in that the parameter setting unit sets, for sweep data before clutter suppression, parameters for clutter suppression processing: an offset value to the average value of intensities of reference cells surrounding a cell of interest, and a multiplication coefficient to the sum of the average value and the offset value; and the clutter suppression unit (1) maintains the intensity of the cell of interest as it is when the intensity is greater than the product of the sum and the multiplication coefficient, and (2) suppresses the intensity of the cell of interest as clutter when the intensity is smaller than the product of the sum and the multiplication coefficient.

[0021] According to this configuration, when executing CA-CFAR, by setting an offset value, it is possible to prevent clutter from being left behind, and the CA-CFAR parameters can be set fully automatically without using manual knobs, regardless of whether the user has experience or not.

[0022] The present disclosure also provides a clutter suppression program for causing a computer to sequentially execute the processing steps executed by the processing units included in the clutter suppression device described above.

[0023] According to this configuration, it is possible to provide a program having the above-described effects.

[0024] The above-disclosed inventions can be combined as much as possible. [Effects of the Invention]

[0025] In this way, the present disclosure enables the parameters of the clutter suppression process for sweep data to be set fully automatically without using manual knobs, regardless of whether the operator has a high level of expertise, when using a radar to suppress clutter and recognize targets. [Brief explanation of the drawings]

[0026] [Figure 1] 1 is a diagram illustrating a problem with clutter suppression processing in the prior art; [Figure 2] FIG. 1 is a diagram illustrating a configuration of a radar system according to the present disclosure. [Figure 3] FIG. 2 is a diagram showing a procedure of clutter suppression processing according to the present disclosure. [Figure 4] 10A and 10B are diagrams illustrating a specific example of clutter suppression processing according to the present disclosure. [Figure 5] 10A and 10B are diagrams illustrating a specific example of clutter suppression processing according to the present disclosure. [Figure 6] FIG. 10 is a diagram illustrating a specific example of a parameter setting process according to the present disclosure. [Figure 7] FIG. 10 is a diagram illustrating a specific example of a parameter setting process according to the present disclosure. [Figure 8] FIG. 10 is a diagram showing a specific example of one system of clutter suppression processing according to the present disclosure. [Figure 9] 10A and 10B are diagrams illustrating a specific example of two-system clutter suppression processing according to the present disclosure. [Figure 10] FIG. 1 is a diagram illustrating the procedure of OS-CFAR processing according to the present disclosure. [Figure 11] FIG. 1 illustrates a specific example of OS-CFAR processing according to the present disclosure. [Figure 12] FIG. 1 is a diagram illustrating a procedure of CA-CFAR processing according to the present disclosure. [Figure 13] FIG. 1 illustrates a specific example of CA-CFAR processing according to the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0027]

[0023] The following embodiments of the present disclosure will be described with reference to the accompanying drawings. The embodiments described below are examples of implementation of the present disclosure, and the present disclosure is not limited to the following embodiments.

[0028] (Overview of clutter suppression processing of the present disclosure) The configuration of the radar system of the present disclosure is shown in Figure 2. The procedure for the clutter suppression processing of the present disclosure is shown in Figure 3. The radar system S includes a radar transceiver 1, a clutter suppression device 2, and a radar display device 3, and uses a radar mounted on a ship, aircraft, or the like to suppress clutter such as sea surface clutter or rain / snow clutter and recognize targets such as ships or aircraft.

[0029] The radar transceiver 1 emits a radar transmission signal and receives a radar reflection signal. The clutter suppression device 2 sets parameters for clutter suppression processing, suppresses clutter, and recognizes targets. The radar display device 3 displays targets after clutter has been removed.

[0030] The clutter suppression device 2 includes a parameter setting unit 21 and a clutter suppression unit 22, and can be realized by installing the clutter suppression program shown in FIG. 3 in a computer, or by equipping the radar system S with the clutter suppression ASIC (Application Specific Integrated Circuit) shown in FIG. 3.

[0031] In summary, the present disclosure focuses on the fact that the "distribution length" of clutter is long / short for sweep data "before clutter suppression" when sea surface waves are high / low or when rain / snow is strong / weak. Therefore, the parameters of the clutter suppression process are set so that the clutter suppression effect is high / low for sweep data "before clutter suppression" as the "distribution length" of clutter is long / short, respectively, thereby suppressing clutter and recognizing targets.

[0032] In other words, the parameter setting unit 21 sets the parameters for the clutter suppression process for each sweep direction for the sweep data for each direction before clutter suppression so that the clutter suppression effect increases / decreases as the clutter distribution length starting from the position of the radar transceiver 1 increases / decreases, respectively (step S1).

[0033] Then, the clutter suppression unit 22 suppresses clutter for the sweep data for each direction before clutter suppression, based on the parameters for the clutter suppression process for each sweep direction set by the parameter setting unit 21, and recognizes the target (step S2).

[0034] A specific example of the clutter suppression processing of the present disclosure is shown in Fig. 4. In Fig. 4, parameters for the clutter suppression processing for each sweep direction are set fully automatically for the radar image R. The clutter distribution length starting from the position of the radar transceiver 1 is defined as the distance between the position of the radar transceiver 1 and the position where the radar reflection intensity is reduced to a predetermined intensity.

[0035] As a result, in the upper left column of Fig. 4, when the sea surface has high waves or there is heavy rain and snow, the distribution length of the clutter starting from the position of the radar transceiver 1 becomes long for each sweep direction. Then, in the upper right column of Fig. 4, by setting the clutter suppression parameter for each sweep direction to an appropriately large value, the clutter suppression effect for each sweep direction becomes appropriately high, making it possible to reduce the amount of clutter that remains and to recognize targets.

[0036] On the other hand, in the lower left column of Fig. 4, when the sea surface waves are low or the rain and snow are light, the distribution length of the clutter starting from the position of the radar transceiver 1 becomes short for each sweep direction. Then, in the lower right column of Fig. 4, by setting the clutter suppression parameter for each sweep direction to an appropriate small value, the clutter suppression effect for each sweep direction becomes appropriately low, so that excessive target fading can be reduced and targets can be recognized.

[0037] A specific example of the clutter suppression processing of the present disclosure is also shown in Figure 5. In Figure 5, parameters for the clutter suppression processing for each sweep direction are set fully automatically for the radar image R. The distribution length of the clutter starting from the position of the radar transceiver 1 is long in the sweep direction D1 (e.g., upwind of the ship) and short in the sweep direction DN (e.g., downwind of the ship).

[0038] That is, in the upper left column of Fig. 5, the distribution length of clutter C starting from the position of the radar transceiver 1 becomes longer in the sweep direction D1 (upwind of the ship, etc.). Then, in the upper right column of Fig. 5, by setting the clutter suppression parameter in the sweep direction D1 (upwind of the ship, etc.) to an appropriate value, the clutter suppression effect in the sweep direction D1 becomes appropriately high, so that the remaining clutter C can be reduced and the target T can be recognized.

[0039] On the other hand, in the lower left column of Fig. 5, the distribution length of the clutter C starting from the position of the radar transceiver 1 in the sweep direction DN (downwind of the ship, etc.) becomes shorter. Then, in the lower right column of Fig. 5, by setting the clutter suppression parameter in the sweep direction DN (downwind of the ship, etc.) to an appropriate small value, the clutter suppression effect in the sweep direction DN becomes appropriately low, so that excessive fading of the target T can be reduced and the target T can be recognized.

[0040] In this way, the parameters for the clutter suppression process for the sweep data for each sweep direction can be set completely automatically without using manual knobs, regardless of whether the operator has a high level of skill or not.

[0041] (Specific example of parameter setting process of the present disclosure) A specific example of the parameter setting process of the present disclosure is shown in Fig. 6. In the left column of Fig. 6, the parameter setting unit 21 sets the parameters of the clutter suppression process with a proportional increase in accordance with the clutter distribution length starting from the position of the radar transceiver 1 for the sweep data before clutter suppression. In the right column of Fig. 6, the parameter setting unit 21 sets the parameters of the clutter suppression process with a monotonically increasing downward convex (or upward convex) increase in accordance with the clutter distribution length starting from the position of the radar transceiver 1 for the sweep data before clutter suppression.

[0042] A specific example of the parameter setting process of the present disclosure is also shown in Figure 7. In the left column of Figure 7, the parameter setting unit 21 sets a "reference" parameter PR for clutter suppression processing for the "reference" distribution length of clutter originating from the position of the radar transceiver 1 for the sweep data before clutter suppression, and sets the "reference" parameter PR "other" for clutter suppression processing for "other" clutter distribution lengths based on the clutter suppression processing parameter "linear" PL. In the right column of Figure 7, the parameter setting unit 21 sets "various" parameters P1,...,PN for clutter suppression processing for "various" distribution lengths of clutter originating from the position of the radar transceiver 1 for the sweep data before clutter suppression.

[0043] In Figures 6 and 7, the setting of the parameters for the clutter suppression process relative to the clutter distribution length and the setting of the reference parameters for the clutter suppression process relative to the clutter reference distribution length can be changed in various ways according to various radar ranges (various pulse widths or reception bands) or various detection modes (float detection, coastal navigation mode, etc.).

[0044] (Specific example of clutter suppression processing for systems 1 and 2 of the present disclosure) A specific example of clutter suppression processing of the "first system" of the present disclosure is shown in Fig. 8. At the "initial stage" of radar operation, the parameter setting unit 21 sets parameters for clutter suppression processing for the sweep data before clutter suppression of the "first system."

[0045] During "normal" radar operation, the clutter suppression unit 22 suppresses clutter for the sweep data of the "first system" before clutter suppression based on the parameters of the clutter suppression process that are "the same" as the parameters set during the "initial" radar operation.

[0046] In the upper part of Figure 8, radar images R11, R12, R13, R14, R15, and R16 of the "first system" are radar images with clutter suppression, generated over time from initial to normal. In the lower part of Figure 8, "actual" wave conditions W1, W2, W3, W4, W5, and W6 are plotted over time from initial to normal for comparison with radar images R11, R12, R13, R14, R15, and R16 of the "first system." Here, "actual" wave conditions are interpreted literally as actual wave conditions that are not radar images, but also as radar images without clutter suppression, i.e., wave removal.

[0047] In the "actual" wave conditions W1, W2, W3, and W4, the distribution length of the clutter originating from the radar transceiver 1 remains short. In the "actual" wave conditions W5 and W6, the distribution length of the clutter originating from the radar transceiver 1 changes over time in the direction of increasing in length.

[0048] At the "initial stage" of radar operation, the parameter setting unit 21 sets parameters for clutter suppression processing for the radar image R14 before clutter suppression of the "first system" based on the average image of the radar images R11, R12, and R13 before clutter suppression of the "first system."

[0049] During "normal" radar operation, the clutter suppression unit 22 suppresses clutter for the "first system" pre-clutter suppression radar images R14, R15, and R16 based on the "same" clutter suppression processing parameters as the parameters set during the "initial" phase of radar operation. As a result, clutter is suppressed in the "first system" post-clutter suppression radar image R14. Then, in the "first system" post-clutter suppression radar images R15 and R16, clutter remains depending on the change over time in the clutter distribution length.

[0050] In this way, after the parameters for clutter suppression processing are set "initially" during radar operation, if the environment, such as the sea surface or rain / snow, "does not change" during "regular" radar operation, the parameters for clutter suppression processing can be "maintained at the initial settings." Then, if the "initial settings" for radar operation are "repeatedly executed," the parameters for clutter suppression processing can be made to follow environmental changes, such as the sea surface or rain / snow.

[0051] A specific example of the "two-system" clutter suppression processing of the present disclosure is shown in Fig. 9. The parameter setting unit 21 sets parameters for the clutter suppression processing for the "first system" sweep data before clutter suppression during "normal" radar operation.

[0052] During "normal" radar operation, the clutter suppression unit 22 suppresses clutter based on parameters of the clutter suppression process for the "first system" sweep data before clutter suppression and the "second system" sweep data before clutter suppression, which is "separate."

[0053] In the upper part of Fig. 9, radar images R11, R12, R13, R14, R15, and R16 of the "first system" are radar images for setting parameters without clutter suppression, and are generated as time passes from the initial state to the normal state. In the lower part of Fig. 9, radar images R21, R22, R23, R24, R25, and R26 of the "second system" are radar images with clutter suppression, and are generated as time passes from the initial state to the normal state. Radar images R11, R12, R13, R14, R15, and R16 of the "first system" correspond to "actual" wave conditions W1, W2, W3, W4, W5, and W6 (not shown in Fig. 9).

[0054] In the radar images R11, R12, R13, and R14 of the "first system," the distribution length of the clutter originating from the radar transceiver 1 remains short, corresponding to the "actual" wave conditions W1, W2, W3, and W4 (not shown in FIG. 9). In the radar images R15 and R16 of the "first system," the distribution length of the clutter originating from the radar transceiver 1 changes over time in the direction of becoming longer, corresponding to the "actual" wave conditions W5 and W6 (not shown in FIG. 9).

[0055] During "normal" radar operation, the parameter setting unit 21 sets parameters for clutter suppression processing for the radar image R14 before clutter suppression of the "first system" based on the average image of the radar images R11, R12, and R13 before clutter suppression of the "first system."

[0056] During "normal" radar operation, the clutter suppression unit 22 suppresses clutter based on the parameters of the clutter suppression process for the radar image R14 before clutter suppression of the "first system" and the "separate" radar image R24 before clutter suppression of the "second system."

[0057] During "normal" radar operation, the parameter setting unit 21 sets parameters for clutter suppression processing for the radar image R15 before clutter suppression of the "first system" based on the average image of the radar images R12, R13, and R14 before clutter suppression of the "first system."

[0058] During "normal" radar operation, the clutter suppression unit 22 suppresses clutter based on the parameters of the clutter suppression process for the radar image R15 before clutter suppression of the "first system" and the "separate" radar image R25 before clutter suppression of the "second system."

[0059] During "normal" radar operation, the parameter setting unit 21 sets parameters for clutter suppression processing for the radar image R16 before clutter suppression of the "first system" based on the average image of the radar images R13, R14, and R15 before clutter suppression of the "first system."

[0060] During "normal" radar operation, the clutter suppression unit 22 suppresses clutter based on the parameters of the clutter suppression process for the radar image R16 before clutter suppression of the "first system" and the "separate" radar image R26 before clutter suppression of the "second system."

[0061] As a result, clutter is suppressed in the radar image R24 after clutter suppression of the "second system." Then, in the radar image R25 after clutter suppression of the "second system," clutter remains in the image depending on the change in the clutter distribution length over time. However, in the radar image R26 after clutter suppression of the "second system," the amount of clutter remains is reduced, regardless of the change in the clutter distribution length over time, and clutter is further suppressed.

[0062] In this way, after the parameters for clutter suppression processing are set "initially" during radar operation, even if the environment, such as the sea surface or rain / snow, "changes" during "regular" radar operation, the parameters for clutter suppression processing can "adapt to environmental changes." And, even if the "initial setting" of radar operation "is not repeatedly performed," the parameters for clutter suppression processing can be made to follow environmental changes, such as the sea surface or rain / snow.

[0063] (Specific example of OS and CA-CFAR processing of the present disclosure) The procedure for the OS-CFAR processing of the present disclosure is shown in Fig. 10. A specific example of the OS-CFAR processing of the present disclosure is shown in Fig. 11. In scan data D, guard cells are placed around the cell of interest in order to recognize large ships and the like, and reference cells are placed around the guard cells.

[0064] The parameter setting unit 21 sets the intensity of the reference cell for the sweep data D before clutter suppression so that x1≦ ≦ x k ≦ ≦ x m (m is the total number of reference cells) in ascending order (step S11). Then, the parameter setting unit 21 sets the k-th intensity x of the reference cell as a parameter for the clutter suppression process for the sweep data D before clutter suppression. k (Step S12), and extracting the intensity x k (Step S13), and the intensity x k and the coefficient α multiplied by x k *An upper limit value t for α is set (step S14).

[0065] Here, the parameter setting unit 21 sets the parameter k and the multiplication coefficient α in the same way as in normal OS-CFAR processing, but unlike normal OS-CFAR processing, it also sets an upper limit value t, the reason for which will be described later with reference to FIG. 11. The parameter setting unit 21 then sets the parameter k in accordance with the ratio of the "current" distribution length of the clutter to the "reference" distribution length of the clutter. 現状 =k 基準 *Current distribution length / reference distribution length, multiplication coefficient α 現状 =α 基準 *Current distribution length / reference distribution length and upper limit t 現状 =t 基準 *Set the current distribution length / reference distribution length.

[0066] The clutter suppressor 22 calculates the multiplication value x k *When α is larger than the upper limit value t (step S14, YES), the strength x t If is greater than the upper limit t (step S15, YES), the strength x tis maintained as is (step S16).

[0067] In the upper part of FIG. 11, a target T in the cell of interest is present against the background of clutter C in the reference cell, whose intensity decreases as the distance from the position of the radar transceiver 1 increases. The protruding clutter C (intensity x k ) also exists. Then, the intensity x of the target cell is t As a threshold for k *α, the target T in the cell of interest is suppressed as clutter. t If the upper limit value t is adopted as the threshold for the target T, the target T in the cell of interest is maintained as it is.

[0068] The clutter suppressor 22 calculates the multiplication value x k *When α is larger than the upper limit value t (step S14, YES), the strength x t If is smaller than the upper limit value t (step S15, NO), the strength x t is suppressed as clutter (step S17).

[0069] The clutter suppressor 22 calculates the multiplication value x k *When α is smaller than the upper limit value t (step S14, NO), the strength x t is the multiplication value x k *If it is larger than α (step S18, YES), the intensity x t is maintained as is (step S19).

[0070] In the lower part of FIG. 11, the target T in the cell of interest is present against the background of clutter C in the reference cell, whose intensity decreases as the distance from the position of the radar transceiver 1 increases. However, the prominent clutter C (intensity x k ) does not exist. Then, the intensity x of the target cell is t As a threshold for kEven if *α is adopted, the target T in the cell of interest remains the same. Rather, the intensity x t If the upper limit value t is adopted as the threshold for , the target T in the cell of interest is suppressed as clutter.

[0071] The clutter suppressor 22 calculates the multiplication value x k *When α is smaller than the upper limit value t (step S14, NO), the strength x t is the multiplication value x k *If it is smaller than α (step S18, NO), the intensity x t is suppressed as clutter (step S20).

[0072] In this way, by setting the upper limit value t when executing OS-CFAR, it is possible to prevent erroneous target removal, and to set the OS-CFAR parameters fully automatically without using a manual knob, regardless of the level of experience. Note that the parameters set according to the clutter distribution length may be all or some of the parameters k, multiplication coefficient α, and upper limit value t.

[0073] The procedure of the CA-CFAR processing of the present disclosure is shown in Fig. 12. A specific example of the CA-CFAR processing of the present disclosure is shown in Fig. 13. In scan data D, guard cells are placed around the cell of interest in order to recognize large ships and the like, and reference cells are placed around the guard cells.

[0074] The parameter setting unit 21 calculates the intensity of the reference cell for the sweep data D before clutter suppression as Av=(x1+ +x k +···+x m) / m (m is the total number of reference cells) (step S21). Then, for the sweep data D before clutter suppression, the parameter setting unit 21 sets an offset value D to the average value Av (step S22) and a multiplication coefficient β to the sum ATT (ATTenuation) of the average value Av and the offset value D as parameters for the clutter suppression process (steps S23 and S24).

[0075] Here, the parameter setting unit 21 sets the multiplication coefficient β in the same way as in normal CA-CFAR processing, but unlike normal CA-CFAR processing, it also sets an offset value D (however, the offset value D is set to a positive value in order to suppress clutter), the reason for which will be described later with reference to FIG. 13. The parameter setting unit 21 then sets the offset value D in accordance with the ratio of the "current" distribution length of the clutter to the "reference" distribution length of the clutter. 現状 =D 基準 *Current distribution length / reference distribution length and multiplication coefficient β 現状 =β 基準 *Set the current distribution length / reference distribution length.

[0076] The clutter suppression unit 22 calculates the intensity x of the target cell. t is larger than the multiplication value ATT*β of the addition value ATT and the multiplication coefficient β (step S24, YES), the intensity x t is maintained as is (step S25).

[0077] In the upper part of Fig. 13, a target T in a cell of interest is present against the background of clutter C in a reference cell, the intensity of which decreases as the distance from the position of the radar transceiver 1 increases. Then, the intensity x t If the multiplication value Av*β is used as the threshold for the target T in the cell of interest, there is a high possibility that the target T in the cell of interest will be maintained as it is. t Even if a multiplication value ATT*β larger than the multiplication value Av*β is used as the threshold for the target T in the cell of interest, there is a high possibility that the target T will be maintained as it is.

[0078] The clutter suppression unit 22 calculates the intensity x of the target cell. t is smaller than the product ATT*β of the addition value ATT and the multiplication coefficient β (step S24, NO), the intensity x t is suppressed as clutter (step S26).

[0079] In the lower part of Fig. 13, the target T does not exist in the cell of interest against the background of clutter C in the reference cell, whose intensity decreases as the distance from the position of the radar transceiver 1 increases. Then, the intensity x t If the multiplication value Av*β is used as the threshold for the intensity x t If a multiplication value ATT*β that is larger than the multiplication value Av*β is adopted as the threshold for the clutter C in the cell of interest, there is a high possibility that the clutter C in the cell of interest will be suppressed.

[0080] In this way, by setting the offset value D when executing CA-CFAR, clutter is prevented from being left behind, and the CA-CFAR parameters can be set fully automatically without using manual controls, regardless of whether the user has a high level of experience. Note that the parameters set in accordance with the clutter distribution length may be all or some of the parameters out of the offset value D and the multiplication coefficient β. [Industrial Applicability]

[0081] The clutter suppression device and clutter suppression program disclosed herein use a radar mounted on a ship, aircraft, etc. to suppress clutter such as sea surface clutter or rain / snow clutter, and when recognizing targets such as ships or aircraft, can set parameters for clutter suppression processing on sweep data fully automatically without using manual knobs, regardless of whether the user is experienced or not. [Explanation of symbols]

[0082] S: Radar system 1: Radar transmitter and receiver 2: Clutter suppression device 3: Radar display device 21: Parameter setting section 22: Clutter suppression unit R: Radar image R11, R12, R13, R14, R15, R16: Radar images R21, R22, R23, R24, R25, R26: Radar images W1, W2, W3, W4, W5, W6: Actual wave conditions T:Target C: Clutter PR: Reference parameter PL: Parameter line P1, PN: parameters D: Sweep data

Claims

1. A clutter suppression device that uses a radar to suppress clutter and recognize a target, a parameter setting unit that sets parameters for clutter suppression processing for sweep data before clutter suppression so that the clutter suppression effect increases / decreases as the clutter distribution length starting from the position of the radar increases / decreases, respectively; a clutter suppression unit that suppresses clutter based on the parameters of the clutter suppression process set by the parameter setting unit for the sweep data before clutter suppression; A clutter suppression device comprising:

2. the parameter setting unit sets parameters for clutter suppression processing for each sweep direction for sweep data for each direction before clutter suppression; The clutter suppression unit suppresses clutter for sweep data for each direction before clutter suppression based on parameters for clutter suppression processing for each sweep direction.

2. The clutter suppression device according to claim 1.

3. the parameter setting unit sets parameters for clutter suppression processing for sweep data before clutter suppression of a first system during normal operation of the radar; The clutter suppression unit suppresses clutter based on parameters of clutter suppression processing for second-system sweep data before clutter suppression, which is separate from the first-system sweep data before clutter suppression, during normal operation of the radar.

3. The clutter suppression device according to claim 1 or 2.

4. the parameter setting unit sets parameters for clutter suppression processing for sweep data before clutter suppression of a first system at an early stage of operation of the radar; The clutter suppression unit suppresses clutter for the sweep data of the first system before clutter suppression during normal operation of the radar, based on parameters of clutter suppression processing that are the same as parameters set at the beginning of operation of the radar.

3. The clutter suppression device according to claim 1 or 2.

5. the parameter setting unit sets, as parameters for the clutter suppression process for the sweep data before clutter suppression, which of the reference cells surrounding the cell of interest to extract an intensity from, a multiplication coefficient for the intensity, and an upper limit value for the multiplication value of the intensity and the coefficient; The clutter suppression unit (1) maintains the intensity of the cell of interest as it is or suppresses it as clutter if the intensity of the cell of interest is larger / smaller than the upper limit value when the multiplication value is larger than the upper limit value, and (2) maintains the intensity of the cell of interest as it is or suppresses it as clutter if the intensity of the cell of interest is larger / smaller than the multiplication value when the multiplication value is smaller than the upper limit value.

3. The clutter suppression device according to claim 1 or 2.

6. the parameter setting unit sets, as parameters for clutter suppression processing, an offset value to an average value of intensities of reference cells around a cell of interest and a multiplication coefficient to a value obtained by adding the average value and the offset value, for sweep data before clutter suppression; The clutter suppression unit (1) maintains the intensity of the cell of interest as it is when the intensity is greater than the product of the sum and the multiplication coefficient, and (2) suppresses the intensity of the cell of interest as clutter when the intensity is smaller than the product of the sum and the multiplication coefficient.

3. The clutter suppression device according to claim 1 or 2.

7. 3. A clutter suppression program for causing a computer to sequentially execute the processing steps executed by the processing units of the clutter suppression device according to claim 1.

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