JP4913012B2 - Automatic gain controller - Google Patents

Description

The present invention relates to an automatic gain control device that automatically controls the display level of a received signal in a radar device that transmits and receives pulsed radio waves.

In order to obtain an optimal radar image in a radar device installed on a ship for the purpose of supporting safe and efficient navigation, white noise generated inside the radar device or the sea surface is adjusted appropriately. It is necessary to remove clutter such as reflection and rain / snow reflection at an optimum level.
The reception sensitivity is adjusted by a gain control device in the radar device. In the following description, unnecessary signals such as white noise and clutter are referred to as noise, and a reflected signal from an object to be detected such as a ship, a buoy, and land is referred to as a target echo to be distinguished.

As a reception sensitivity adjustment method in a conventional radar apparatus, for example, there is one described in Patent Document 1.
In this Patent Document 1, a signal having a certain amplitude value or more is extracted from a received signal to perform sensitivity adjustment, and the extracted signals are counted. Then, the count value is compared with a preset reference value, and the level of the gain control signal is adjusted according to the result.
Japanese Patent No. 3288489

To support safe navigation in the vicinity of harbors where there are many man-made structures such as wharves, breakwaters, piers, ships, etc., inside harbors, and sea areas such as canals (hereinafter referred to as “port areas”) For this reason, it is desirable that the radar device clearly displays artificial structures such as a quay, a breakwater, a pier, and a ship that exist near the ship.
However, the threshold value suitable for this display does not necessarily match the threshold value suitable for removing noise on the ocean away from the land. For this reason, the conventional automatic gain control device described in Patent Document 1 has a problem that it is difficult to clearly display an artificial structure in a harbor area while noise can be appropriately removed at sea. It was.

The present invention has been made in view of such problems, and an object of the present invention is to provide an automatic gain control apparatus capable of automatically performing gain control according to the sea area where the ship is located.

The present invention automatically changes the threshold to be applied depending on whether the ship position is inside or outside the harbor area, and realizes optimum reception sensitivity adjustment according to the sea area where the ship is located.

Specifically, the present invention is an automatic gain control device that compares the amplitude of a received signal obtained from a radar search area with a predetermined threshold and outputs a received signal having an amplitude equal to or greater than the predetermined threshold. A determination unit for determining whether the ship position is in the harbor area or outside the harbor area, and based on a determination result of the determination unit, the first threshold used outside the harbor area or in the harbor area A threshold value calculation unit that calculates a second threshold value to be used; and an output control unit that performs gain control of the received signal using the threshold value calculated by the threshold value calculation unit.

The determination unit determines whether the own ship position is in the port area or outside the port area based on the amplitude value of the received signal in the determination area defined as an area within a certain distance range from the own ship. For example, the determination unit counts the number (N) of data having an amplitude greater than or equal to a predetermined amplitude (Aref) from the received signal in the determination area, and the count value (N) is greater than or equal to a predetermined value (Nref). When the ship position is determined to be within the harbor area, the ship position is determined to be outside the harbor area when less than a predetermined value (Nref).

In addition, the determination unit determines whether the ship position is in the port area or outside the port area based on the amplitude value of the received signal extracted for each division determination region defined as a region obtained by dividing the determination region in the azimuth direction. You may make it determine.

The determination unit may determine whether the ship position is in the port area or outside the port area based on the ship position information and the map information.

The inside / outside determination of the harbor area by the determination unit is performed for each search area of the own ship, and the area for each inside / outside determination area defined as an area obtained by dividing the search area of the own ship into a plurality of azimuth directions. It may be determined whether the area is inside or outside the harbor area. Specifically, the determination unit determines whether the area is inside or outside the harbor area for each inside / outside determination region, and the threshold value calculation unit sets the first threshold value or the second threshold value to the inside / outside determination region. Calculate every time. Thereby, for example, when entering the port, the first threshold value used outside the port area is calculated for the area behind the ship, and the second threshold value used within the port area is calculated for the area ahead of the ship. Is also possible. In addition, in order to avoid the discontinuity of sensitivity that occurs when processing is switched for each azimuth in this way, the calculated threshold value is smoothed so that the sensitivity continuously changes in the azimuth direction at the boundary of the inside / outside determination region. Processing such as conversion may be performed.

In addition, the threshold value may change discontinuously immediately after the determination result by the determination unit changes from inside the port area to outside the port area, or immediately after changing from outside the port area to inside the port area. In order to prevent the radar image from changing discontinuously with this change, the threshold value calculation unit calculates the first threshold value and the second threshold value, and outputs the weighted average value of both as the threshold value. It may be.

As another method, the threshold value calculation unit may calculate a weighted average value of the previously output threshold value and the currently calculated threshold value, and output the calculated average value as a current output threshold value.
For the latter method, regardless of whether or not the determination result by the determination unit changes, the weighted average value of the previously output threshold value and the currently calculated threshold value is always calculated, and the calculated average value is calculated. You may output as the threshold value output this time. As a result, the threshold value calculation unit can output an optimum threshold value with almost no influence even when an abnormal value is temporarily calculated for some reason.

The present invention also relates to an automatic gain control device that compares the amplitude of a received signal obtained from a radar search area with a predetermined threshold and outputs a received signal having an amplitude equal to or greater than the predetermined threshold. A determination unit that determines whether the position is in the harbor area or outside the harbor area, a notification unit that notifies the determination result of the determination unit to the user, a user input reception unit that receives an input from the user who has received the notification, A threshold calculating unit that calculates a first threshold used outside the harbor area or a second threshold used inside the harbor area based on an output from a user input receiving unit and a determination result from the determining unit; And an output control unit that performs gain control of the received signal using the threshold value calculated by the calculation unit. With such a configuration, the user can also select and apply the first threshold value or the second threshold value according to the determination result by the determination unit, so that convenience for the user can be improved.

According to the present invention, it is possible to obtain a radar image having an optimum sensitivity on the ocean and in a harbor without performing operations such as setting change and sensitivity adjustment.

(Embodiment 1)
FIG. 1 is a block diagram showing the configuration of an automatic gain control apparatus according to Embodiment 1 of the present invention.
In FIG. 1, the automatic gain control apparatus according to the first embodiment of the present invention includes a determination unit 11, a threshold calculation unit 12, and an output control unit 13.

The determination unit 11 determines whether the sea area where the ship is located is inside the port area or outside the port area. The harbor area refers to the area around the harbor where there are many man-made structures such as quay, breakwater, pier, and ship, the inside of the harbor, and sea areas such as canals.
Based on the determination result of the determination unit 11, the threshold calculation unit 12 calculates a first threshold used outside the port area or a second threshold used inside the port area. In the following description, an algorithm for calculating the first threshold is referred to as a first threshold calculation algorithm, and an algorithm for calculating the second threshold is referred to as a second threshold calculation algorithm.
The output control unit 13 performs gain control of the received signal using the threshold value calculated by the threshold value calculation unit 12.

Below, the example of the determination process by the determination part 11 is demonstrated.
1. A determination-type radar apparatus that uses the amplitude value of a received signal transmits a pulsed radio wave at a predetermined period and receives a radio wave reflected by a target from an antenna that rotates on a horizontal plane at a predetermined period. The receiving unit of the radar apparatus converts the received radio wave into an electric signal, samples it at a predetermined sampling rate, and converts it into a digital signal. The determination unit 11 performs the determination processes (1) and (2) described below using the reception signal converted into a digital signal by the reception unit.

(1) First Determination Method FIG. 2 is an explanatory diagram for explaining determination processing by the determination unit 11.
As shown in FIG. 2, the determination unit 11 determines the own ship based on the amplitude value of the received signal in the determination area defined as an area within a certain distance range (for example, 0.1 to 0.2 NM) from the own ship. Determine if the location is within the harbor area or outside the harbor area.

For example, the determination unit 11 extracts a reception signal in the determination region from reception signals in the entire search region, and counts the number (N) of data having an amplitude greater than or equal to a predetermined amplitude (Aref) among the extracted reception signals. . The determination unit 11 determines that the ship position is in the harbor area when the count value (N) is equal to or greater than a predetermined value (Nref), and determines that the ship position is less than the predetermined value (Nref). It is determined that it is outside the port area. Since the amplitude of the received signal depends on the transmission pulse width, the values of Aref and Nref may be changed according to the transmission pulse width. If the sampling rate of the received signal varies depending on the detection range, the values of Aref and Nref may be changed according to the sampling rate of the received signal.

(2) Second determination method The received signal in the harbor area has a particularly large amplitude in the direction in which a large building exists or the direction in which the transmission pulse is perpendicularly incident on the side of the quay. Compared with the received signal at, the amplitude of the received signal tends to differ greatly for each direction. On the other hand, although the received signal at sea is small compared to the inside of the port, for example, when there are a large number of ships all around the ship, the count value (N) in the first determination method described above. Takes a large value. Accordingly, the determination unit 11 may erroneously determine that the ship position is within the port area even though the ship position is actually outside the port area.

Therefore, in the second determination method, it is determined whether the ship position is in the port area or outside the port area in consideration of the difference in amplitude value for each direction.
FIG. 3 is an explanatory diagram for explaining a determination process in consideration of the direction by the determination unit 11.

As shown in FIG. 3, the determination unit 11 determines the own ship based on the amplitude value of the received signal extracted for each division determination area defined as an area obtained by dividing the determination area into M (for example, 12) areas in the azimuth direction. Determine if the location is within the harbor area or outside the harbor area.

As an example, the determination unit 11 extracts a reception signal for each division determination region from reception signals in the entire search region, and among the reception signals extracted for each division determination region, data having an amplitude equal to or greater than a predetermined amplitude (Aref). Count the number of And the determination part 11 extracts M0 (for example, 3) in an order from the largest thing among the count values (Nsub) obtained for every division | segmentation determination area | region, and makes the sum total (S) of the extracted M0 count value. calculate. The determination unit 11 determines that the ship position is within the harbor area when the sum (S) is equal to or greater than a predetermined value (Sref), and the ship position is outside the harbor area when the sum is less than the predetermined value (Sref). It is determined that Since the amplitude of the received signal depends on the transmission pulse width, the values of Aref and Sref may be changed according to the transmission pulse width. If the sampling rate of the received signal varies depending on the detection range, the values of Aref and Nref may be changed according to the sampling rate of the received signal.

As another example, it is also possible to determine whether the ship position is within the port area or outside the port area based on the similarity of the frequency distribution with the amplitude value of the adjacent division determination region as a variable. For example, the determination unit 11 generates a frequency distribution with the amplitude value as a variable with respect to the reception signal in the division determination region having the largest count value (Nsub) and the division determination region adjacent thereto. Here, these frequency distributions are expressed as h1 [j] and h2 [j] (0 ≦ j ≦ J−1), respectively. j represents the class of the frequency distribution, and J represents the class number. The determination unit 11 calculates a similarity index ρ defined by Equation 1 based on these arrays.
The determination unit 11 determines that the ship position is outside the harbor area when the index ρ is equal to or greater than a predetermined value (ρref), and the ship position is within the harbor area when the index ρ is less than the predetermined value (ρref). Is determined.

In this way, the determination unit 11 can perform determination processing that reflects the situation for each direction by determining whether the ship position is within the port area or outside the port area from the amplitude information obtained for each direction. become.

2. Determination method using map information Whether the ship position is in the port area or outside the port area can be determined using map information in addition to using the amplitude value of the received signal. That is, the determination unit 11 stores in advance the latitude and longitude of the harbor area, and based on the latitude and longitude of the ship position obtained from a positioning device such as GPS, Determine if out of area.

Next, threshold value calculation processing by the threshold value calculation unit 12 will be described with reference to FIG.
FIG. 4 is a flowchart for explaining the processing of the threshold value calculation unit 12 of the present invention.
(S11) First, the threshold value calculation unit 12 acquires a determination result from the determination unit 11 whether the ship position is outside the port area or the port area.
(S12) If the determination result by the determination unit 11 is outside the port area, the threshold value calculation unit 12 calculates a first threshold value used outside the port area using the first threshold value calculation algorithm.
(S13) On the other hand, when the determination result by the determination part 11 is in a harbor area, the threshold value calculation part 12 calculates the 2nd threshold value used in a harbor area using a 2nd threshold value calculation algorithm.

Next, the first threshold value calculation algorithm will be described with reference to FIG.
The first threshold value calculation algorithm generates a frequency distribution having an amplitude value as a variable for a received signal in a predetermined region, and calculates a threshold value for removing noise such as white noise and clutter at an optimum level based on the frequency distribution. .
The first threshold value calculation algorithm generates a frequency distribution whose amplitude value is a variable for a received signal from a predetermined area, and calculates a threshold value for removing noise such as white noise and clutter at an optimum level based on the frequency distribution. To do.

Specific examples thereof will be described below.
FIG. 5 is an explanatory diagram for explaining an example of a threshold calculation method using the first threshold calculation algorithm.
First, as shown in FIG. 5, the first threshold value calculation algorithm uses a target echo for each threshold value calculation region defined as a region obtained by dividing the radar search region into a plurality of regions, based on the frequency distribution of that region. It is determined whether the target echo dominant region is dominant or the noise dominant region is a noise dominant region.

Next, the threshold value of the noise dominant region is calculated based on the frequency distribution of the region determined as the noise dominant region. In the target echo dominant region, it is difficult to calculate an appropriate threshold for removing noise due to the influence of the target echo. Therefore, the threshold value of the target echo dominant region is calculated by performing interpolation processing or extrapolation processing on the threshold value calculated in the noise dominant region. As a result, it is possible to calculate a threshold for removing noise such as white noise and clutter at an optimum level without being affected by the target echo.

Note that the first threshold calculation algorithm described here is merely an example, and is not limited to this as long as it is a threshold calculation algorithm that can remove white noise, clutter, and other noises at an optimum level on the sea away from the land. It is not a thing.

On the other hand, in order to support safe navigation in the harbor area, it is desirable that the radar device clearly displays artificial structures such as quays, breakwaters, piers, ships, etc. that exist near the ship. However, the threshold value suitable for this display does not necessarily match the threshold value suitable for removing noise on the ocean away from the land.

This is not an exception to the first threshold calculation algorithm described above, and it is difficult for the threshold calculation unit 12 to perform optimum threshold adjustment using the first threshold calculation algorithm in the harbor area.

Therefore, the automatic gain control device of the present invention switches the threshold calculation algorithm based on the determination result of the determination unit 11, and uses the first threshold calculation algorithm when the ship position is outside the harbor area. When the own ship position is within the harbor area, the second threshold is calculated using the second threshold calculation algorithm.

Hereinafter, the second threshold value calculation algorithm will be described with reference to FIG.
As shown in FIG. 6, the second threshold value calculation algorithm calculates a threshold value by using the first threshold value calculation algorithm as it is for an area separated from the ship by a certain distance (for example, 0.5 NM). For an area closer to the ship than the distance, a predetermined threshold is used according to the distance from the ship.

That is, the threshold value calculation unit 12 outputs an appropriate threshold value for clearly displaying an artificial structure such as a quay, a breakwater, a pier, and a ship for an area near the own ship. For regions that are more than a distance apart, a threshold value calculated using the first threshold value calculation algorithm described above is output. In order to prevent the threshold value from changing discontinuously in the distance direction, it is more preferable to perform processing in which the threshold value changes continuously at the boundary between these two regions.

Note that the second threshold calculation algorithm described here is merely an example, and it is a threshold calculation algorithm that can clearly display artificial structures such as quays, breakwaters, piers, ships, etc. existing near the ship. If there is, it is not limited to this.

As described above, the present invention determines whether the position of the ship is in the harbor area or outside the harbor area, and changes the threshold to be used based on the determination result, thereby changing the setting or adjusting the sensitivity both at sea and in the harbor. The radar image with the optimum sensitivity can always be obtained without executing the operation.

In the first embodiment of the present invention, a description has been given of changing the threshold calculation algorithm for the entire search area depending on whether the ship position is in the harbor area or outside the harbor area, but the surrounding sea area where the ship is located is described. Based on the situation, it may be determined for each azimuth whether in the harbor area or outside the harbor area, and the threshold calculation algorithm may be switched for each azimuth.

Specifically, the determination unit 11 determines whether the radar search area is inside or outside the harbor area for each inside / outside judgment area defined as an area obtained by dividing the radar search area into a plurality of directions. Then, the threshold calculation unit 12 selects and executes the first threshold calculation algorithm and the second threshold calculation algorithm for each inside / outside determination region based on the determination result for each inside / outside determination region by the determination unit 11. Thereby, for example, when entering the port, it is possible to calculate a second threshold value suitable for the inside of the port area in front of the ship and to calculate a first threshold value suitable for the outside of the port area behind the ship. In order to avoid the discontinuity of sensitivity that occurs when processing is switched for each azimuth, smoothing is performed on the calculated threshold value so that the sensitivity continuously changes in the azimuth direction at the boundary of the inside / outside determination region. Processing may be performed.

(Embodiment 2)
Next, an automatic gain control apparatus according to Embodiment 2 of the present invention will be described. In the automatic gain control device according to the second embodiment of the present invention, the threshold value calculation unit 12 changes immediately after the determination result by the determination unit 11 changes from within the port area to outside the port area, or from outside the port area to within the port area. Immediately after that, the first threshold value and the second threshold value are calculated, and the weighted average value of both is output as the threshold value, which is different from the automatic gain control apparatus according to the first embodiment of the present invention described above. The constituent elements other than the threshold calculation unit 12 are the same as those of the automatic gain control apparatus according to the first embodiment described above, and thus the description thereof is omitted here.

FIG. 7 is a flowchart for explaining the processing of the threshold value calculation unit 12 according to the second embodiment of the present invention. The flowchart shown in FIG. 7 is a process executed by the threshold value calculation unit 12 when the determination result by the determination unit 11 changes from inside the port area to outside the port area, or when changing from outside the port area to inside the port area.

(S21) When the determination result by the determination unit 11 changes from inside the port area to outside the port area, or when changing from outside the port area to inside the port area, the threshold value calculation unit 12 includes the first threshold value calculation algorithm, the second The first threshold value and the second threshold value are calculated using both of the threshold calculation algorithms.

(S22) Next, the threshold calculation unit 12 sets the weighting amounts α and β of the first threshold and the second threshold. Here, α is a coefficient to be multiplied by the threshold value calculated using the threshold value calculation algorithm corresponding to the determination result before the change, and β is a coefficient to be multiplied by the threshold value calculated using the threshold value calculation algorithm corresponding to the determination result after the change. . For example, when the weighting amount is changed by 0.1 as shown in Table 1, when α used last time is α [N−1] and α used this time is α [N], the weighting amount α is α [N]. N] = α [N−1] −0.1. Further, when β used last time is β [N−1] and β used this time is β [N], the weighting amount β is β [N] = β [N−1] +0.1. The initial values of α and β are α = 1 and β = 0.

(S23) After α and β are set, the threshold calculation unit 12 calculates αA + βB and calculates a threshold to be output to the output control unit 13. A is a threshold value calculated using a threshold value calculation algorithm corresponding to the determination result before the change, and B is a threshold value calculated using a threshold value calculation algorithm corresponding to the determination result after the change. For example, when the determination result by the determination unit 11 changes from inside the harbor area to outside the harbor area, the second threshold calculated using the second threshold calculation algorithm used inside the harbor area is A, which is used outside the harbor area. The first threshold value calculated using the first threshold value calculation algorithm is B.

(S24) The threshold calculation unit 12 outputs the threshold calculated by the calculation of αA + βB to the output control unit 13.
(S25) Thereafter, the threshold calculation unit 12 has completely shifted from the state before the change to the state after the change, that is, whether or not the set value of α is “0” and the set value of β is “1”. If α = 0 and β = 1, the process ends. On the other hand, unless α = 0 and β = 1, the processing from step S21 to step S23 is repeatedly executed until α = 0 and β = 1. Thereby, it is possible to gradually shift from the threshold before the change to the threshold after the change through the threshold calculation processing for 10 times.

When the determination result by the determination unit 11 changes again during the process from step S21 to step S24, the values of α and β are set to 0.1 as in the process from step S21 to step 25 described above. It is sufficient to change the values one by one to return to the state of α = 1 and β = 0. Thereby, even if it is a case where the determination result by the determination part 11 is changed again, it can prevent that the threshold value applied changes rapidly.

Further, as a method for realizing the weighting process according to the second embodiment of the present invention more simply, there is the following method.
While the radar apparatus is operating, the threshold value calculation unit 12 repeats the operation of calculating the first threshold value or the second threshold value based on the determination result by the determination unit 11 and outputting it to the output control unit 13. At this time, instead of outputting the calculated threshold value as it is, the threshold value calculation unit 12 calculates a weighted average value of the previous threshold value calculated with the same azimuth and distance and the currently calculated threshold value, and outputs the average value. To do. If the previously output threshold value is THout [N−1] and the currently calculated threshold value is TH [N], the currently output threshold value THout [N] is, for example, THout [N] = 0.1 × TH [N] +0. .9 × THout [N−1]. Note that the calculated threshold value may be output as it is immediately after the radar apparatus is activated.

Thereby, even when the determination result by the determination unit 11 changes from the port area to the outside of the port area or from the outside of the port area to the inside of the port area, the threshold value can be gradually changed. It becomes possible to avoid. In addition, even when the determination unit 11 temporarily makes a determination error, since a rapid change in the threshold value is alleviated, it is possible to prevent the influence of the erroneous determination without giving the user a sense of incongruity on the radar image. Become.

In Embodiment 2 of the present invention, immediately after the determination result by the determination unit 11 changes from within the port area to the outside of the port area, or immediately after the change from the outside of the port area to the inside of the port area, the previously output threshold value and this time Although calculating the weighted average value with the calculated threshold value and performing the process of outputting the calculated average value as the threshold value to be output this time, regardless of whether or not the determination result by the determination unit changes, A weighted average value of the previously output threshold value and the currently calculated threshold value may always be output as the currently output threshold value. Thereby, even if the threshold value calculation unit temporarily calculates an abnormal value for some reason, it is possible to output an optimum threshold value with little influence.

(Embodiment 3)
Next, an automatic gain control apparatus according to Embodiment 3 of the present invention will be described. The automatic gain control apparatus according to the third embodiment of the present invention is different from the automatic gain control apparatus according to the first embodiment of the present invention described above in that the determination result by the determination unit 11 is notified to the user. The same components as those in the automatic gain control apparatus according to Embodiment 1 described above are denoted by the same reference numerals, and description thereof is omitted.

FIG. 8 is a block diagram showing a configuration of an automatic gain control apparatus according to Embodiment 3 of the present invention.
In FIG. 8, the automatic gain control device according to the third embodiment of the present invention includes a determination unit 11, a threshold calculation unit 12, an output control unit 13, a notification unit 21, and a user input reception unit 22.

The notification unit 21 notifies the user of the determination result of the determination unit 11. Note that the notification method to the user may be a method of notifying by sound or vibration in addition to a method of displaying the determination result on the display screen.

The user input accepting unit 22 is an input device such as a mouse that accepts user input. The user input accepting unit 22 accepts an instruction to execute any of the following processes [1] to [3], and the received instruction is a threshold value calculating unit. 12 is output.
[1] The first threshold value or the second threshold value is calculated according to the determination result of the determination unit 11.
[2] The first threshold value is calculated regardless of the determination result of the determination unit 11.
[3] The second threshold value is calculated regardless of the determination result of the determination unit 11.

The threshold calculation unit 12 executes one of the processes [1] to [3] shown above according to the instruction received by the user input reception unit 22. As a result, the user can change the threshold while viewing the radar image. For example, when the user wants to remove the sea surface reflection clutter in the harbor area, the user may select [2] shown above. If the determination unit 11 makes an erroneous determination, it is possible to select [2] or [3] shown above and apply an appropriate threshold value.

The present invention can be freely modified within the scope of the present invention described in each embodiment of the present invention, and is not limited to the contents described in each embodiment of the present invention. .

1 is a block diagram showing a configuration of an automatic gain control device according to Embodiment 1 of the present invention. Explanatory drawing for demonstrating the determination process by a determination part Explanatory drawing for demonstrating the determination process by the determination part which considered the azimuth | direction The flowchart for demonstrating the process by the threshold value calculation part of this invention Explanatory drawing for demonstrating an example of the threshold value calculation method using the 1st threshold value calculation algorithm The figure which shows an example of the 2nd threshold value calculated using the 2nd threshold value calculation algorithm The flowchart for demonstrating the process by the threshold value calculation part when the determination result by the determination part of the automatic gain control apparatus by Embodiment 2 of this invention changes. Block diagram showing a configuration of an automatic gain control apparatus according to Embodiment 3 of the present invention.

Explanation of symbols

11 determination unit 12 threshold calculation unit 13 output control unit 21 notification unit 22 user input reception unit

Claims (10)

In the automatic gain control device that compares the amplitude of the received signal obtained from the radar search area with a predetermined threshold and outputs a received signal having an amplitude greater than or equal to the predetermined threshold,
A determination unit for determining whether the position of the ship is in the harbor area or outside the harbor area;
Based on the determination result of the determination unit, a threshold calculation unit that calculates a first threshold used outside the harbor area or a second threshold used within the harbor area;
An output control unit that performs gain control of a received signal using the threshold value calculated by the threshold value calculation unit;
An automatic gain control device comprising: The automatic gain control device according to claim 1,
The determination unit determines whether the own ship position is in the port area or outside the port area based on the amplitude value of the received signal in the determination area defined as an area within a certain distance range from the own ship. Automatic gain control device. The automatic gain control device according to claim 2,
The determination unit counts the number (N) of data having an amplitude greater than or equal to a predetermined amplitude (Aref) from the received signal in the determination area, and the count value (N) is equal to or greater than a predetermined value (Nref) An automatic gain control device, characterized in that it determines that its own ship position is in the harbor area, and determines that its own ship position is outside the harbor area when it is less than a predetermined value (Nref). The automatic gain control device according to claim 2,
The determination unit determines whether the own ship position is in the port area or outside the port area based on the amplitude value of the received signal extracted for each division determination region defined as a region obtained by dividing the determination region into a plurality of directions. An automatic gain control device characterized by determining. The automatic gain control device according to claim 1,
The determination unit determines whether the ship position is in the port area or outside the port area based on the ship position information and the map information. The automatic gain control device according to claim 1,
The determination unit determines whether the radar search area is defined as an area obtained by dividing the radar search area into a plurality of directions in the harbor area or outside the harbor area.
The threshold calculation unit calculates the first threshold or the second threshold for each of the inside / outside determination regions. The automatic gain control device according to claim 1,
The threshold value calculation unit calculates the first threshold value and the second threshold value immediately after the determination result by the determination unit changes from inside the port area to outside the port area, or immediately after changing from outside the port area to inside the port area. Then, the automatic gain control device outputs the weighted average value of both to the output control unit as a threshold value to be output this time. The automatic gain control device according to claim 1,
The threshold calculation unit calculates a weighted average value of a previously output threshold value and a currently calculated threshold value, and outputs the calculated average value to the output control unit as a current output threshold value. apparatus. The automatic gain control device according to claim 1,
An automatic gain control apparatus comprising: a notification unit that notifies a user whether the ship position is in a port area or outside a port area based on a determination result of the determination unit. In the automatic gain control device that compares the amplitude of the received signal obtained from the radar search area with a predetermined threshold and outputs a received signal having an amplitude greater than or equal to the predetermined threshold,
A determination unit for determining whether the position of the ship is within the harbor area or outside the harbor area;
Based on the determination result of the determination unit, a notification unit that notifies the user whether the ship position is in the harbor area or outside the harbor area;
A user input receiving unit that receives input from the user who has received the notification;
Based on the output from the user input reception unit and the determination result from the determination unit, a threshold value calculation unit that calculates a first threshold value used outside the port area or a second threshold value used in the port area;
An output control unit that performs gain control of a received signal using the threshold value calculated by the threshold value calculation unit;
An automatic gain control device comprising: