Suppression amount determination device, radar receiver, suppression amount determination method, radar reception method, suppression amount determination program, radar reception program

Abstract

To obtain the amount of suppression for appropriately suppressing sea surface reflection using only radar while maintaining real-time performance.SOLUTION: A suppression amount determination device of the present invention includes a mask generation unit, an in-mask representative feature calculation unit, an in-mask representative feature recording unit, an azimuth angle in-range feature tendency calculation unit, a sea surface reflection identification unit, and a specific sea surface reflection suppression amount determination unit. The mask generation unit generates a mask by using a range where the strength of a received signal is high as one mask. The in-mask representative feature calculation unit calculates a representative feature amount including a representative tendency value indicating that the received signal in the mask is likely to be a reflected signal on a sea surface. The azimuth angle in-range feature tendency calculation unit calculates a tendency value condition, which is a condition for identifying reflection on the sea surface. The sea surface reflection identification unit determines whether the received signal in the mask is reflection on the sea surface. The specific sea surface reflection suppression amount determination unit determines a suppression amount so as to reduce the received signal of the mask determined to be reflection on the sea surface equal to or less than a noise level.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a suppression amount determination device, a suppression amount determination method, and a suppression amount determination program that determine a suppression amount for suppressing signals reflected from the sea surface from radar reception signals received at sea, as well as a radar receiver, a radar reception method, and a radar reception program that suppress signals reflected from the sea surface using the determined suppression amount. [Background technology]

[0002] Marine radars installed on ships monitor obstacles such as nearby ships, land, and navigational markers for safe navigation. The antennas typically use a fan beam pattern with narrow horizontal and relatively wide vertical directivity, which transmits radio waves while rotating horizontally and receives reflected waves from surrounding objects to determine the distance and direction of the objects. However, the received signals contain not only reflected waves from objects (targets) necessary for safe navigation, but also reflected waves (ocean surface clutter) from waves appearing mainly near the ship, which can hinder the identification of targets.

[0003] Sea clutter varies depending on sea conditions such as wind direction and speed, and is generally said to attenuate in proportion to the cube of the distance at short distances and the seventh power at long distances (Non-Patent Document 1). Sensitivity Time Control (STC) has been widely used as a method for suppressing sea clutter. This is a process that suppresses sea clutter by attenuating the received signal inversely proportional to the power of the distance, in accordance with the characteristics of sea clutter that attenuates with distance.

[0004] However, as mentioned above, sea clutter is affected by wind direction and speed, and its behavior varies depending on the direction relative to the radar. Therefore, if uniform attenuation is applied in all directions, events such as the disappearance of the target or the remaining sea clutter can occur. Non-Patent Document 1 provides a solution to this problem. In Non-Patent Document 1, the sea clutter strength for each azimuth angle range is estimated from the received signal acquired within a specified azimuth angle range, and the received signal is suppressed accordingly. In addition to extracting features for each azimuth angle range, Patent Document 1 suppresses sea clutter that cannot be completely suppressed by CFAR (Constant False Alarm Rate) processing by determining the amount of attenuation at each sampling point according to the distance.

[0005] Furthermore, the above processing basically utilizes the nature of sea surface clutter levels changing with distance, and applies an attenuation curve (STC curve) according to distance to all received signals. However, in this case, attenuation is applied to the target object as well as the sea surface clutter, which can result in a decrease in identification ability or even loss depending on the size of the target object.

[0006] On the other hand, a process called scan-to-scan correlation is also widely used to suppress sea clutter. This is a method of storing multiple sets of previously acquired scan data (= data from one antenna revolution) and suppressing sea clutter in the current data through statistical processing. Generally, sea clutter is scattered around the ship, and its location and number tend to change irregularly, so averaging multiple scans can achieve a significant effect in suppressing sea clutter. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-25916 [Non-patent literature]

[0008] [Non-Patent Document 1] Tomiji Nirasawa and Hiroshi Okada, "Automated STC for Radar (Lecture at the 51st Conference of the Japan Institute of Navigation)," Transactions of the Japan Institute of Navigation, No. 52, pp. 101-108, December 1974. Summary of the Invention [Problem to be solved by the invention]

[0009] However, in Non-Patent Document 1, the received signal also contains reflected waves from the target, so there is still a problem in determining the appropriate amount of suppression. Patent Document 1 also has a problem in determining whether reflected waves contained in the received signal are necessary. Furthermore, in the case of inter-scan correlation processing, a large number of scans are required to achieve sufficient suppression, which leads to problems such as poor real-time performance and the tendency to lose fast-moving targets. Furthermore, a direction sensor separate from the radar is required to determine the absolute direction for each scan. The present invention aims to obtain a suppression amount for appropriately suppressing sea clutter using only radar while maintaining real-time performance. [Means for solving the problem]

[0010] The suppression amount determination device of the present invention determines the amount of suppression for suppressing signals reflected from the sea surface from radar reception signals received at sea. The received signals are signals received at predetermined azimuths and indicate intensities at a predetermined distance resolution. The suppression amount determination device includes a mask generation unit, an in-mask representative feature calculation unit, an in-mask representative feature recording unit, an in-azimuth angle range feature tendency calculation unit, a sea surface clutter identification unit, and a specific sea surface clutter suppression amount determination unit. The mask generation unit determines the amount of suppression for suppressing signals reflected from the sea surface from radar reception signals received at sea. The received signals are received at predetermined azimuths and indicate intensities at a predetermined distance resolution. The mask generation unit calculates a mask representative feature tendency within the mask, a mask representative feature recording unit, an in-azimuth angle range feature tendency calculation unit, a sea surface clutter identification unit, and a specific sea surface clutter suppression amount determination unit. DistanceA mask is generated by treating the range as one mask. The intra-mask representative feature calculation unit calculates, for each mask, a representative feature amount including a representative tendency value indicating that the received signal within a predetermined mask is likely to be a signal reflected from the sea surface. The intra-mask representative feature recording unit records the representative feature amount for each azimuth. The intra-azimuth angle range feature tendency calculation unit calculates a tendency value condition, which is a condition for identifying sea surface reflection, based on the representative tendency value of the predetermined azimuth range. The sea surface clutter identification unit determines, for each mask of the received signal to be processed, whether the received signal within the mask is a sea surface reflection according to the representative tendency value and tendency value condition of the mask. The specific sea surface clutter suppression amount determination unit determines, for each mask of the received signal to be processed, a suppression amount so as to reduce the received signal of the mask determined by the sea surface clutter identification unit to be a sea surface reflection below the noise level. [Effects of the Invention]

[0011] In this invention, sea clutter is identified from the characteristics of sea surface reflection and only the identified sea clutter is suppressed. Therefore, the suppression amount determination device of the present invention can obtain the suppression amount for appropriately suppressing sea clutter using only the radar while ensuring target identification and maintaining real-time performance. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a diagram showing an example of the functional configuration of a radar receiver 200 having a suppression amount determination device 100 according to the present invention. [Figure 2] FIG. 10 is a diagram showing the processing flow of a radar reception method including a suppression amount determination method. [Figure 3] 1 is a diagram showing an example of a received signal obtained from a radar. [Figure 4] This figure shows an example in which a mask is generated for all indexes, with 100 dB or more being "higher than a predetermined value," and the generated mask is added to Figure 3. [Figure 5] FIG. 5 is a diagram showing an example in which an example in which the width of the mask is used as a representative tendency value is added to FIG. 4 . [Figure 6]FIG. 10 is a diagram showing an example of cumulative probability distribution when the width of the mask (the number of indexes) is used as a representative tendency value. [Figure 7] FIG. 5 is a diagram showing an example in which an example in which the distance between adjacent masks is used as a representative tendency value is added to FIG. 4 . [Figure 8] FIG. 10 is a diagram showing an example of cumulative probability distribution when the distance to the next farthest mask (number of indexes) is used as a representative tendency value. [Figure 9] FIG. 5 is a diagram showing an example in which a value indicating the strength of the received signal within the mask is used as a representative tendency value, and a pair of a representative distance indicating the distance to the mask and the representative tendency value is used as a representative feature amount, added to FIG. 4 . [Figure 10] FIG. 10 is a diagram showing an example of a cumulative probability distribution when a value indicating the strength of a received signal within a mask is used as a representative tendency value, and a pair of a representative distance indicating the distance to the mask and the representative tendency value is used as a representative feature amount. [Figure 11] FIG. 2 is a diagram showing an example of the functional configuration of a computer. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, embodiments of the present invention will be described in detail. Components having the same functions are given the same numbers, and duplicated explanations will be omitted. [Example]

[0014] FIG. 1 shows an example of the functional configuration of a radar receiver 200 having a suppression amount determination device 100 of the present invention. FIG. 2 shows the processing flow of a radar reception method including a suppression amount determination method. FIG. 3 shows an example of a received signal acquired from a radar. The horizontal axis of FIG. 3 shows the index of the radar's reflected signal. The distance indicated by the number is determined by the distance resolution setting. For example, if the distance resolution is 20 m, the number 1000 corresponds to a distance of 20 km from the radar. Furthermore, if the distance resolution is 0.5 m, the number 1000 corresponds to a distance of 500 m from the radar. The vertical axis of FIG. 3 shows the strength (Level) of the received signal. The unit of the vertical axis is dB.

[0015] In the example of the received signal in Figure 3, there is land at a distance farther than the number 550, and there is sea surface reflection (sea clutter) at a distance closer to the number 550. As can be seen from Figure 3, sea surface reflection is weaker than reflection from land. Furthermore, as shown in Non-Patent Document 1 and other documents, the strength decreases as the distance increases. In the range where sea surface clutter exists, the strength of the received signal changes at short distance intervals. In this invention, by utilizing the property that sea surface clutter changes at short distance intervals and the fact that the strength decreases as the distance increases, the sea surface reflection contained in the received signal in the direction being measured is identified, and the amount of suppression for the identified reflection is determined.

[0016] The suppression amount determination device 100 determines the amount of suppression required to suppress signals reflected from the sea surface from radar signals received over the sea. The suppression amount determination device 100 includes a mask generation unit 110, an in-mask representative feature calculation unit 120, an in-mask representative feature recording unit 130, an azimuth angle range feature tendency calculation unit 140, a sea surface clutter identification unit 150, and a specific sea surface clutter suppression amount determination unit 160. The radar receiver 200 includes the suppression amount determination device 100 and also includes a sea surface clutter suppression unit 270. The "received signal" is a signal that indicates the intensity at a predetermined distance resolution received for each predetermined direction. The predetermined direction may be, for example, every 1 degree or every 0.25 degrees. The predetermined distance resolution may be selected from approximately 0.5 m to 30 m, taking into account the distance to be measured. For example, when numbers up to 1000 can be measured, setting the distance resolution to 0.5 m will result in a measurable distance of 500 m. If the distance resolution is set to 30m, the measurable distance is 30km.

[0017] The mask generation unit 110 generates a mask when the strength of the received signal is continuously higher than a predetermined value. DistanceA mask is generated with the range as one mask (S110). "Higher than a predetermined value" may be equal to or greater than a threshold value set for all indexes, or may be higher than a threshold value set for a value determined taking distance into consideration (the farther the index, the smaller the value). Figure 4 shows an example in which a mask is generated with 100 dB or more set as "higher than a predetermined value" for all indexes, and the generated mask is added to Figure 3. It can be seen that the mask in the vicinity of "reflection from land, etc." in Figure 3 is wide (the width of continuously high intensity), while the mask in the vicinity of "sea surface reflection" is narrow. In other words, many masks are generated in the vicinity of "sea surface reflection."

[0018] The intra-mask representative feature calculation unit 120 calculates, for each mask, a representative feature amount including a representative tendency value that indicates that the received signal within a predetermined mask is likely to be a signal reflected from the sea surface (S120). The intra-mask representative feature calculation unit 120 may use the width of the mask, the distance between adjacent masks, a value indicating the strength of the received signal within the mask, or the like as the representative tendency value. Note that, when the representative tendency value is the strength of the received signal within the mask, the representative feature amount is a combination of a representative distance indicating the distance to the mask and the representative tendency value.

[0019] The in-mask representative feature recording unit 130 records the representative feature amount for each azimuth direction (S130). The in-mask representative feature recording unit 130 records predetermined past representative feature amounts for each azimuth direction for use in processing by the in-azimuth angle range feature tendency calculation unit 140, which will be described later.

[0020] The azimuth angle range feature tendency calculation unit 140 calculates the tendency value condition, which is a condition for identifying sea surface clutter, based on the representative tendency value for a predetermined azimuth range (S140). The "predetermined azimuth range" refers to a range that includes received signals older than the received signal being processed. For example, if received signals are received every 1 degree of azimuth angle, and the "predetermined azimuth range" is set to 10 degrees, then nine previous received signals can be added to the received signal being processed. This is because sea surface clutter has similar properties within a certain azimuth range. The "predetermined azimuth range" may be 45 degrees or 90 degrees.

[0021] If the width of a mask or the distance between adjacent masks is used as the representative tendency value, the "tendency value condition" may be, for example, a condition for determining whether a range in which the representative tendency value exists is highly likely to be a reflection signal from the sea surface. If a value indicating the intensity of a received signal within a mask is used as the representative tendency value, the "tendency value condition" may be, for example, a condition for determining whether a range in which a value obtained by multiplying the representative tendency value intensity by a predetermined function of the representative distance exists is highly likely to be a reflection signal from the sea surface. The "function of the representative distance" may be a function of the cube of the representative distance, in accordance with Equation (4) in Non-Patent Document 1. However, since other documents use different functions, the function may be determined as appropriate. The "representative distance" may be determined as appropriate using a predetermined method as long as it is within the range of distances included in the mask. For example, it may be the center distance within the mask or the distance with the highest intensity within the mask. The "representative intensity" may be determined based on the intensity within the mask using a predetermined method. For example, it may be the average intensity within the mask or the highest intensity within the mask.

[0022] FIG. 5 is an example in which an example of a representative feature example 1, in which the width of a mask is used as a representative tendency value, is added to FIG. 4. However, it cannot be added to masks with narrow widths. It is added only to masks with widths that are easily visible. In reality, the intra-mask representative feature calculation unit 120 calculates a representative feature for each mask. FIG. 6 shows an example of a cumulative probability distribution when the width of a mask (the number of indexes) is used as the representative tendency value. The horizontal axis represents the mask width (the number of indexes). The vertical axis represents the proportion (probability) of the number of masks within the mask width when the total number of masks in a predetermined orientation range is used as the parameter. Note that FIG. 6 is an example to illustrate the cumulative probability distribution and is not based on the data of the example of FIG. 5. Furthermore, a distribution other than a cumulative probability distribution may be used. For example, a probability density function, an average, a variance, etc. may be used.

[0023] If sea surface reflections are characterized by a narrow mask width and a high proportion of sea surface reflection signals included in the reflected signals, then a range where the cumulative probability distribution is 90% or less can be determined to be a sea surface reflection. In this case, the threshold mask width and the range of tendency value conditions, which are the conditions for determining that a reflection is from the sea surface, are shown in Figure 6. However, "90% or less" is an example and can be set as appropriate. Also, although only an upper limit threshold has been set, a lower limit threshold can also be set.

[0024] FIG. 7 shows an example of representative feature example 2, in which the distance between adjacent masks is used as a representative tendency value, added to FIG. 4. However, this is not added to masks with narrow spacing. It is added only to masks with a width that is easily visible. The intra-mask representative feature calculation unit 120 actually calculates representative features for each of all masks. FIG. 8 shows an example of a cumulative probability distribution when the distance to the next-furthest mask (the number of indexes) is used as the representative tendency value. The horizontal axis represents the distance to the mask (the number of indexes). The vertical axis represents the proportion (probability) of the number of masks within a distance to the mask when the total number of masks in a predetermined orientation range is used as the parameter. Note that FIG. 8 is an example to illustrate the cumulative probability distribution and is not based on the data of the example of FIG. 7. Furthermore, a method other than the cumulative probability distribution may be used. For example, a probability density function, an average, a variance, or the like may be used.

[0025] If sea surface reflections are characterized by a narrow gap between adjacent masks and a high proportion of signals reflected from the sea surface in the reflected signal, then a range in which the cumulative probability distribution is 90% or less can be determined to be a sea surface reflection. In this case, the threshold value for the distance to the next-furthest mask and the range of tendency value conditions, which are the conditions for determining that a reflection is from the sea surface, are shown in Figure 8. Note that "90% or less" is an example and can be set as appropriate. Also, while only an upper threshold is set, a lower threshold may also be set. Note that in Figure 7, the distance to the next-furthest mask is used as the gap between adjacent masks, but the distance to the closest mask may also be used, or the sum or average of the distances to both adjacent masks may also be used.

[0026] FIG. 9 shows an example of a representative feature third example, in which a value indicating the strength of the received signal within the mask is used as a representative tendency value, and a pair of a representative distance indicating the distance to the mask and a representative tendency value is used as the representative feature. In FIG. 9, a representative feature is added to FIG. 4, in which the distance to the center of the mask is used as the representative distance and the average intensity within the mask is used as the representative intensity. However, this feature is not added for narrow masks. It is added only for masks with a width that is easily visible. The intra-mask representative feature calculation unit 120 actually calculates a representative feature for each mask. FIG. 10 shows an example of a cumulative probability distribution in which a value indicating the strength of the received signal within the mask is used as a representative tendency value, and a pair of a representative distance indicating the distance to the mask and a representative tendency value are used as the representative feature. The horizontal axis represents the average signal level multiplied by the cube of the distance. The vertical axis represents the proportion (probability) of the number of masks when the total number of masks in a predetermined azimuth range is used as the parameter. Note that FIG. 10 is an example to illustrate the cumulative probability distribution, and is not based on the data of the example of FIG. 9. Furthermore, it is also possible to use a function other than the cumulative probability distribution, such as a probability density function, an average, or a variance.

[0027] If the proportion of signals reflected from the sea surface in the reflected signal is high, then it can be determined that the signal is a reflection from the sea surface when the cumulative probability distribution is in the range of 5% to 95%, for example. In this case, the lower and upper thresholds for the value obtained by multiplying the average signal level by the cube of the distance, as well as the range of tendency value conditions for determining that the signal is a reflection from the sea surface, are shown in Figure 10. However, "5%" and "95% or less" are merely examples and can be set as appropriate.

[0028] For each mask of the received signal to be processed, the sea surface reflection identification unit 150 determines whether the received signal within the mask is a reflection from the sea surface according to the representative tendency value and tendency value condition of the mask (S150). For example, in the examples of Figures 6, 8, and 10, the received signal within the mask within the range indicated as "tendency value condition" is determined to be a reflection from the sea surface.

[0029] The specific sea surface clutter suppression amount determiner 160 determines the amount of suppression for each mask of the received signal to be processed so as to reduce the received signal of the mask determined to be a sea surface reflection by the sea surface clutter identifying unit 150 to below the noise level (S160). In the case of the received signal shown in Fig. 3, the amount of suppression can be determined so as to be 80 to 90 dB or less.

[0030] In this invention, sea clutter is identified from the characteristics of sea surface reflection and only the identified sea clutter is suppressed. Therefore, the suppression amount determination device of the present invention can obtain the suppression amount for appropriately suppressing sea clutter using only the radar while ensuring target identification and maintaining real-time performance.

[0031] The sea clutter suppression unit 270 suppresses the received signal according to the amount of suppression determined for each mask (S270). The radar receiver 200 of the present invention suppresses only sea clutter, so it can suppress sea clutter while maintaining target identification.

[0032] [Programs, recording media] The various processes described above can be implemented by loading a program that executes each step of the above method into the recording unit 2020 of the computer 2000 shown in Figure 11 and operating the control unit 2010, input unit 2030, output unit 2040, display unit 2050, etc.

[0033] The program describing the processing contents can be recorded on a computer-readable recording medium, which may be, for example, a magnetic recording device, an optical disk, a magneto-optical recording medium, a semiconductor memory, or any other suitable recording medium.

[0034] The program may be distributed, for example, by selling, transferring, lending, etc. a portable recording medium such as a DVD or CD-ROM on which the program is recorded. Furthermore, the program may be stored in a storage device of a server computer, and then transferred from the server computer to another computer via a network, thereby distributing the program.

[0035] A computer that executes such a program may first temporarily store the program recorded on a portable recording medium or transferred from a server computer in its own storage device. Then, when executing a process, the computer reads the program stored on its own recording medium and executes the process in accordance with the read program. Alternatively, the computer may read the program directly from a portable recording medium and execute the process in accordance with the program. Furthermore, the computer may execute the process in accordance with the received program each time a program is transferred from a server computer to the computer. Alternatively, the server computer may not transfer the program to the computer, but may execute the process through a so-called ASP (Application Service Provider) service, which realizes the processing function by issuing an execution instruction and obtaining the results. In this embodiment, the program includes information used for processing by a computer that is equivalent to a program (such as data that is not a direct instruction to the computer but has properties that define computer processing).

[0036] Furthermore, in this embodiment, the device is configured by executing a predetermined program on a computer, but at least a part of the processing contents may be realized by hardware. [Explanation of symbols]

[0037] 100 Suppression amount determination device 110 Mask generation unit 120 Mask representative feature calculation unit 130 Mask representative feature recording unit 140 Azimuth angle range feature tendency calculation unit 150 Sea surface reflection specific part 160 Specific sea clutter suppression amount determination unit 200 radar receiver 270 Sea clutter suppression unit 2000 Computer 2010 Control Unit 2020 Records Department 2030 Input section 2040 Output Unit 2050 Display section

Claims

1. A suppression amount determination device for determining a suppression amount for suppressing a signal reflected from the sea surface from a radar signal received at sea, The received signal is a signal received in each predetermined direction and indicates its intensity at a predetermined distance resolution, a mask generation unit that generates a mask, with one mask being a range of distances where the strength of the received signal is continuously higher than a predetermined value; a mask representative feature calculation unit that calculates, for each mask, a representative feature amount including a representative tendency value that indicates that the received signal within a predetermined mask is likely to be a signal reflected from the sea surface; a representative feature recording unit in a mask that records the representative feature amount for each orientation; an azimuth angle range characteristic tendency calculation unit that calculates a tendency value condition, which is a condition for identifying reflection on the sea surface, based on a representative tendency value in a predetermined azimuth range; a sea surface clutter identifying unit that determines whether or not a received signal within a mask is a clutter of the sea surface, for each mask of the received signal to be processed, according to the representative tendency value of the mask and the tendency value condition; a specific sea clutter suppression amount determining unit that determines a suppression amount for each mask of the received signal to be processed so as to reduce the received signal of the mask determined by the sea clutter identifying unit to be a sea clutter to below the noise level; A suppression amount determining device comprising:

2. 2. The suppression amount determining device according to claim 1, The mask representative feature calculation unit uses the width of the mask as a representative tendency value. A suppression amount determining device characterized by:

3. 2. The suppression amount determining device according to claim 1, The intra-mask representative feature calculation unit uses the distance between adjacent masks as a representative tendency value. A suppression amount determining device characterized by:

4. 4. The suppression amount determining device according to claim 2, The tendency value condition is a condition for determining that a range in which a representative tendency value is likely to exist is a reflected signal from the sea surface. A suppression amount determining device characterized by:

5. 2. The suppression amount determining device according to claim 1, The in-mask representative feature calculation unit sets a value indicating the intensity of the received signal within the mask as a representative tendency value, and sets a pair of a representative distance indicating the distance to the mask and the representative tendency value as a representative feature. A suppression amount determining device characterized by:

6. 6. The suppression amount determining device according to claim 5, The tendency value condition is a condition for determining that a range in which there is a high probability that a value obtained by multiplying the representative tendency value intensity by a predetermined function of the representative distance exists is a reflected signal from the sea surface. A suppression amount determining device characterized by:

7. The suppression amount determining device according to any one of claims 1 to 6, moreover, a sea clutter suppression unit that suppresses the received signal in accordance with the amount of suppression; A radar receiver comprising:

8. A method for determining a suppression amount for suppressing a signal reflected from the sea surface from a radar signal received at sea, comprising: The received signal is a signal received in each predetermined direction and indicates its intensity at a predetermined distance resolution, a mask generation step of generating a mask that is a range of distances where the strength of the received signal is continuously higher than a predetermined value; a mask representative feature calculation step of calculating, for each mask, a representative feature amount including a representative tendency value indicating that the received signal within a predetermined mask is likely to be a signal reflected from the sea surface; a mask representative feature recording step of recording the representative feature amount for each orientation; an azimuth angle range characteristic tendency calculation step for calculating a tendency value condition, which is a condition for identifying reflection on the sea surface, based on a representative tendency value in a predetermined azimuth angle range; a sea surface clutter identifying step of determining whether or not the received signal within each mask is a clutter from the sea surface, based on the representative tendency value of the mask and the tendency value condition, for each mask of the received signal to be processed; a specific sea clutter suppression amount determination step for determining a suppression amount for each mask of the received signal to be processed so as to reduce the received signal of the mask determined to be a sea clutter in the sea clutter identification step to below the noise level; A method for determining the amount of suppression to be performed.

9. The method for determining the amount of suppression according to claim 8, moreover, a sea clutter suppression step of suppressing the received signal in accordance with the suppression amount; Radar reception method to perform.

10. 7. A suppression amount determination program for causing a computer to function as the suppression amount determination device according to claim 1.

11. A radar receiving program for causing a computer to function as the radar receiver according to claim 7.

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