Radar signal processing device, radar device, method for processing radar signals

Abstract

Radar signal processing device (14) comprising: a signal receiver (20) which is configured to receive received data in a polar coordinate system based on a received signal; a data storage device for previous data, designed to store previous correlated data in the polar coordinate system; a polar coordinate correlator (21) designed to generate correlating data by establishing a correlation in the polar coordinate system between the received data and the previous correlated data stored in the data memory of previous data, have been carried out; a trend curve calculation module (22) configured to calculate a trend curve of a distance-direction signal level of the received data in the polar coordinate system; and a target acquisition module (24) which is trained to identify a target based on the signal level of the received data and the trend curve, wherein the polar coordinate correlator (21) modifies the contents of the correlation of the received data based on the target acquisition result of the target acquisition module (24), characterized in that the signal receiver (20) has a log amplifier (26) and a linear amplifier (32) and wherein the signal receiver (20) outputs a log amplifier (26) to the trend curve calculation module (22) and the target acquisition module (24) and outputs a linear amplifier (32) to the polar coordinate correlator (21).

Description

Technical field

[0001] The present invention mainly relates to a radar signal processing device that suppresses interference data by performing a scan correlation on the received signal. background

[0002] Ship radars transmit radio waves from an antenna that rotates in a predetermined cycle in a horizontal plane and receive reflected signals from targets in the vicinity of the antenna. Each received signal (receive signal) is converted into receive data by an analog-to-digital converter (ADC). The received data is processed appropriately and then displayed as a radar image on a display unit. A radar operator can assess the situation regarding targets in the vicinity by reviewing the displayed radar image.

[0003] A distance r to the target can be determined based on the time required by the antenna to receive the reflected signal from the target after transmission. Furthermore, the target's direction can be determined by the antenna's orientation θ at the time it receives the reflected signal. In other words, the signal received by the ship's radar defines the target's position in a polar coordinate system (r, θ).

[0004] In some cases, the received signal contains interference (a reflection wave from the sea surface or rain) and noise. When interference and noise are displayed on the radar image, the target's distinguishability on the radar image decreases. Therefore, a scan correlation for target distinguishability from interference, based on the stability of the received signals between scans and their display on the radar image, is conventionally known for ship radars. Patents 1 to 4 disclose such a scan correlation by way of example.

[0005] Patent specification 1 discloses a configuration in which the received data displayed in the polar coordinate system are converted into an orthogonal coordinate system and scan correlation is performed by accessing an image memory via write and read addresses corresponding to the coordinates in the orthogonal coordinate system. In other words, patent specification 1 performs scan correlation by converting the received data from the polar coordinate system into an orthogonal coordinate system.

[0006] In this regard, patents 2 and 3 describe problems encountered when performing scan correlation after converting the coordinates to the orthogonal coordinate system. For example, patent 2 describes a problem with scan correlation involving conversion from the polar coordinate system to the orthogonal coordinate system: the received data (echo data) must be selected, interpolation data for the coordinate conversion must be generated, and the original echo data cannot be used for scan correlation as is. Furthermore, patent 3 describes a problem where the accuracy of the correlation decreases slightly because the corresponding ratio between the received data and the sweep is lost when the received data is written to the image memory (memory for the correlation) at an address in the orthogonal coordinate system.

[0007] Thus, patents 2 and 3 disclose configurations in which scan correlation is performed while maintaining the polar coordinate system. Patent 2 claims that resolution can be improved by performing scan correlation using the coordinate system when the signal is received. Furthermore, patent 3 claims that the accuracy of the scan correlation is not degraded by maintaining the associated ratio between a true transmission direction and a relative transmission direction of the signal when it is written to / read from the image memory. Referenced prior art documents: Patent specifications Patent specification 1: JP H08-043519A Patent Document 2: JP 2011-095029A Patent Document 3: JP 2003-075528A Patent Document 4: JP H11-094931A

[0008] Further printed prior art in the present technical field is disclosed in documents US 2011 / 0102248 A1, US 2011 / 0291877 A1 and JP 2011-242253 A. Disclosure of the invention [Problems to be solved by the invention]

[0009] Meanwhile, the scan correlation process described above causes a problem: the signal from a relatively fast-moving target is suppressed. In other words, because a relatively high-speed target is not stationary at a single point on the radar screen, it cannot be distinguished from interference and noise. Therefore, the signal from a relatively high-speed target is suppressed during scan correlation, resulting in a blurred image of the target on the radar screen (and ultimately, the target is not displayed).

[0010] In this regard, patent specification 4, for example, discloses a processing method in which the position of the target (target object) is estimated by detecting and tracking the target and correcting its position to the expected position. Patent specification 4 accordingly claims that the target being monitored is clearly displayed, even when moving at high speed. However, since correcting the relative movement of the target using the coordinates of the polar coordinate system is not straightforward, the processing is performed after the coordinates have been converted to the orthogonal coordinate system. Therefore, when the processing according to patent specification 4 is performed, a reduction in the accuracy of the scan correlation due to the conversion of the coordinates from the polar to the orthogonal coordinate system cannot be avoided.Furthermore, processing the detection and tracking requires high processor power, and the number of targets that can be detected and tracked simultaneously is limited.

[0011] The present invention arose in light of the above situation and is mainly directed to provide a radar signal processing device that preserves the accuracy of the scan correlation by performing the scan correlation in a polar coordinate system, and that prevents a high-speed moving target from being suppressed by the scan correlation. [Summary of the invention]

[0012] The problems solved by the present invention are described above; the means of solving the problems and their effects are described below.

[0013] According to a first aspect of the present invention, a radar signal processing device with the following configuration is provided. The radar signal processing device comprises a signal receiver, a data memory for previous data, a polar coordinate correlator, a trend curve calculation module, and a target acquisition module. The signal receiver receives received data in a polar coordinate system based on a received signal. The data memory stores previously correlated data in the polar coordinate system. The polar coordinate correlator generates correlated data by performing a correlation in the polar coordinate system between the received data and the previously correlated data stored in the data memory. The trend curve calculation module calculates a trend curve of a distance-direction signal level of the received data in the polar coordinate system.The target acquisition module detects a target based on the signal level of the received data and the trend curve. Furthermore, the polar coordinate correlator modifies the correlation of the received data based on the target acquisition result from the target acquisition module.

[0014] By changing the content of the scan correlation depending on whether the target has been detected by the target acquisition module, target suppression due to the scan correlation can be prevented.

[0015] The radar signal processing device is preferably designed as follows.

[0016] Since the signal level of the received data is a predetermined level higher than the trend curve, the target acquisition module detects the target. Once the target acquisition module detects the target, the polar coordinate correlator outputs a value from the received data without being correlated.

[0017] By comparing the trend curve with the signal level of the received data, the target can be easily identified. Furthermore, if the target is identified by outputting the non-scan-correlated received data, the suppression of the signal level of the received data indicating the target due to scan correlation can be prevented.

[0018] The radar signal processing device is preferably configured as follows. If the signal level of the received data is higher than the trend curve by a predetermined level, the target acquisition module acquires the target. The polar coordinate correlator changes the weighting coefficients of the received data and the previously correlated data for the case in which the target is acquired by the target acquisition module and for the case in which the target is not acquired.

[0019] The effect of scan correlation can be modified by changing the weighting coefficients. This prevents the target from being suppressed due to scan correlation.

[0020] The radar signal processing device is preferably configured as follows. The target acquisition module outputs a gate signal indicating whether the target has been acquired. The polar coordinate correlator modifies the correlation values ​​according to the gate signal.

[0021] Thus, processing can be switched using a simple configuration depending on whether the target exists.

[0022] The signal processing device is preferably configured as follows. The signal processing device comprises a data acquisition memory configured to store at least the data acquisition result from the target acquisition module in a scan immediately preceding the current scan. The polar coordinate correlator uses at least one of the data acquisition results from the immediately preceding scan, which is stored in the data acquisition memory, and the data acquisition result from the current scan output by the target acquisition module.

[0023] By taking into account the previous target setting result, the achievement of the target can be determined more accurately.

[0024] The signal processing device is preferably configured as follows. The target acquisition module detects the target when the signal level of the received data is higher than a curve corresponding to the trend curve with an added offset.

[0025] Adding the offset to the trend curve prevents the misidentification of an unnecessary signal as the target.

[0026] The radar signal processing device is designed according to the invention as follows. The signal receiver comprises a log amplifier and a linear amplifier. The signal receiver outputs a signal from the log amplifier to the trend curve calculation module and the target acquisition module. Furthermore, the signal receiver outputs a signal from the linear amplifier to the polar coordinate correlator.

[0027] This means that by processing the target acquisition and using the output of the log amplifier, which has a large dynamic range and is not easily saturated, the target can be accurately acquired. Meanwhile, the correlation between the previous signal level and the current signal level can be easily used by performing scan correlation using the output of the linear amplifier, obtained by linearly amplifying the received signal. As a result, a suitable scan correlation can be achieved.

[0028] According to a second aspect of the present invention, a radar device is provided which comprises the radar signal processing device described above, a radar antenna configured to receive the received signals, and a display unit configured to display the radar image based on the result of the scan correlation performed by the polar coordinate correlator.

[0029] The radar device can display the radar image in which the high-speed moving target is not suppressed, and thus an operator of the radar device can accurately assess the situation of the target in the vicinity of the device.

[0030] According to a third aspect of the present invention, a method for processing the radar signal is provided. The method for processing the radar signal comprises acquiring received data in a polar coordinate system based on a received signal, acquiring prior correlated data in the polar coordinate system, generating correlated data by performing a correlation in the polar coordinate system between the received data and the prior correlated data, calculating a trend curve of a distance-direction signal level of the received data in the polar coordinate system, and acquiring the target based on the signal level of the received data and the trend curve. Furthermore, the contents of the correlation of the received data are modified during the generation of the correlated data based on the target acquisition result. Brief description of the drawings Fig. Figure 1 is a block diagram of a radar device according to an embodiment of the present invention. Fig. Figure 2 shows views to describe a target moving at a relatively high speed. Fig. Figure 3 shows a view in which part (a) shows a schematic view of a radar image in which the high-speed moving target is suppressed by a conventional scan correlation, and part (b) is a schematic view showing a radar image based on a radar signal processing device of the present invention. Fig. Figure 4 shows diagrams describing how a target is captured by a target capture module. Fig. Figure 5 is a schematic view showing a radar image with an image obtained through conventional scan correlation. Fig. Figure 6 is a block diagram of a radar device according to a second embodiment. Explanations of the invention

[0031] Exemplary embodiments of the present invention are described below with reference to the drawings. As in Fig. Figure 1 shows a radar device 10 according to the first embodiment of the present invention, which is a radar device for a ship and displays the location of a target or targets (e.g., another ship or ships and the mainland) in the vicinity of the ship. This radar device 10 comprises a radar antenna 11, a transceiver 12, a transmission signal output unit 13, a radar signal processing device 14, and a display unit 15.

[0032] The radar antenna is a directional antenna that rotates 360° in a plane at a predetermined cycle. In the following description, a direction in which a principal extension of the radar antenna 11 is oriented is simply referred to as the orientation of the radar antenna 11. The transmission signal output unit 13 repeatedly outputs a multitude of pulse signals while the radar antenna 11 completes a full rotation. The pulse signal is supplied to the radar antenna 11 via the transceiver 12 and output by the radar antenna 11.

[0033] The pulse signal emitted by radar antenna 11 is reflected off the target in the vicinity and is received again by radar antenna 11. In the following description, the signal received by radar antenna 11 is referred to as the "receive signal." The receive signal is fed to the radar signal processing unit 14 via the transceiver 12. Operation in which radar antenna 11 performs a full rotation while transmitting the signals is called a "scan," and operation in which the pulse signal is transmitted and the receive signals are received before the next pulse signal is transmitted is called a "sweep." It should be noted that a detailed description of the configurations of radar antenna 11, the transmission signal output unit 13, and the transceiver 12 is omitted, as they are known.

[0034] The radar signal processing device 14 comprises a signal receiver 20, a polar coordinate correlator 21, a trend curve calculation module 22, a delay processing module 23, a target acquisition module 24 and an image processing module 25.

[0035] The signal receiver 20 receives the received signal from the transceiver 12. The signal receiver 20 comprises a log amplifier 26 for amplifying the received signal and an analog-to-digital converter (ADC) 27 for sampling the received signal amplified by the log amplifier 26 and converting it into digital data. The digital data output by the ADC 27 is referred to as received data. The value of each received data point determines a signal level of the received signal when the data is acquired. It should be noted that the signal level of the received signals received by the radar antenna 11 lies within an extremely wide range, from a high signal level (e.g., corresponding to the reflected signal from near the radar antenna 11) to a low signal level (e.g., corresponding to a reflected signal from a distance).By using the log amplifier 26 to amplify the received signal, as described above, saturation / overdriving of the output can be prevented when the signal level is high, and the acquisition can be carried out by the A / D converter 27 in a wide dynamic range.

[0036] If the reflection signal from the target is not received by the radar antenna 11, the received signal level becomes noise, and the value of the received data is low. If the reflection signal from the target is received, the received signal level becomes higher than the noise level, and the value of the received data is high. A distance r from the radar antenna 11 to the target can be determined by the time required from the transmission of the pulse signal to the radar antenna 11 until the reflection signal is received. Furthermore, the direction of the target can be obtained based on the orientation θ of the radar antenna 11 at the time of receiving the reflection signal. As described above, the received data received by the signal receiver 20 can be assigned to a point on a plane with coordinates (r, θ) in a polar coordinate system.It can therefore be said that the signal receiver 20 of the radar signal processing device 14 receives all received data in the polar coordinate system (r, θ).

[0037] The polar coordinate correlator 21 performs a scan correlation in the polar coordinate system. The polar coordinate correlator 21 comprises a computational processing module 28 and a memory of previous data 29. The memory of previous data 29 is a memory area in which correlated data for a previous scan (one full rotation of the radar antenna 11) can be stored.

[0038] The calculation processing module 28 performs scan correlation, in which the last data input by the signal receiver 20 and the correlated data of an immediately preceding scan, stored in the memory of previous data 29, are weighted and combined to generate new correlated data and output them. Specifically, the calculation performed by the calculation processing module 28 can be expressed by the following formula: S'r,⊖=(1−α)Dr,⊖+αSr,⊖

[0039] It should be noted that D r,θ The value of the last received data input from signal receiver 20 (signal level) is given, and the subscripts r and θ indicate that the received data corresponds to a location (r, θ) in the polar coordinate system. r,θ stands for data that relates to the position of the received data D r,θ(correlated data from the immediately previous scan) correspond to the correlated data for a scan stored in the memory of previous data 29. The coefficient α is a weighting coefficient (filter coefficient) used for weighting and takes a value within the range between 0 and 1.

[0040] It is evident from equation (1) that scan correlation is a type of IIR filtering and serves to suppress unstable signals between scans. On the other hand, stable signals between scans (reflections from a stationary target) remain unaffected by IIR filtering.

[0041] The memory of previous data 29 stores the correlated data for a scan in the polar coordinate system. Specifically, the write and read addresses of the correlated data S correspond to r,θin the memory of previous data 29 with the coordinates (r, θ) in the polar coordinate system, each of which individually corresponds to the correlated data S r,θ are assigned. Therefore, when calculating formula (1), the correlated data S r,θ Data from previous data 20 can be read while remaining in the polar coordinate system, thus eliminating the need for coordinate conversion. This allows for a more accurate processing result compared to a configuration that performs scan correlation after converting the coordinates to the orthogonal coordinate system, and the target is easily distinguishable from the interfering data.

[0042] The polar coordinate correlator 21 outputs the result of the scan correlation to the image processing module 25. The image processing module 25 generates a two-dimensional image (radar image) that shows the location of the target(s) in the vicinity of the radar signal processing device, based on the result of the scan correlation input from the polar coordinate correlator 21. Since interference data and noise are suppressed by the scan correlation, the image processing module 25 can generate the radar image with suppressed interference data and noise. The image processing module 25 outputs the radar image to the display unit 15. The display unit shows the radar image. Thus, an operator of the radar device 10 can determine the location of the target(s) in the vicinity.

[0043] The following is a brief description of scan correlation problems.

[0044] The scan correlation described above has the disadvantage of suppressing the signal level of the received data, which characterizes the target moving rapidly relative to the radar antenna 11. For example, a case is considered in which a target 30 is moving at high speed relative to the ship, as in Fig. 2 shown. The diagram in part (a) of Fig. Figure 2 schematically shows the received data in the distance direction during an immediately previous scan and the diagram in part (b) of the Fig. Figure 2 schematically shows the received data in the distance direction, which were received during the last sweep. Furthermore, a virtual radar image based on the received data is shown in the upper right part of each diagram.

[0045] In the example of the Fig. In the previous scan, target 30 was located at a distance r1. However, in the latest received data, target 30 has moved to a distance r2 from that location. As described, the position of target 30, which is moving at a relatively high speed, changes between scans. Therefore, the correlation between target 30 in the previous scan and target 30 in the latest scan cannot be used. When performing the scan correlation, the high-speed target 30 is suppressed, and the result, as shown in part (a), is... Fig. As shown in Figure 3, target 30, which should originally have been displayed at a position with a distance of r2, is not clearly visible (or not visible at all) on the radar image. As described, the problem with conventional scan correlation is the poor distinguishability of a high-speed moving target on the radar image.

[0046] In the meantime, the reflected signal from the target may exhibit a sufficient level difference compared to the interfering data and noise. In such a case, the target can be easily distinguished from the interfering data and noise without performing a scan correlation.

[0047] Therefore, the radar signal processing device 14 of this embodiment detects the target by comparing the signal level of the received data with a trend curve and modifying the contents of the scan correlation performed by the polar coordinate correlator 21 based on the target detection result.

[0048] A typical configuration of the radar signal processing device of this embodiment is described in detail below. Specifically, the radar signal processing device 14 of this embodiment comprises the trend curve calculation module 22 and the target acquisition module 24.

[0049] The trend curve calculation module 22 receives the received data from the signal receiver 20. The trend curve calculation module 22 calculates a trend curve of the value (signal level) of the received data in the distance direction. In this embodiment, the trend curve calculation module displays a moving average line of the received data value in the distance direction. The trend curve calculation module 22 outputs the resulting trend curve to the target acquisition module 24.

[0050] The target acquisition module 24 acquires the target based on the received data and the trend curve. Specifically, the target acquisition module 24 compares the signal level of the received data with a curve that corresponds to the trend curve with a constant added offset (offset curve) and acquires the target as soon as the signal level of the received data exceeds the offset curve. As described in Fig. As shown in Figure 4, adding the offset value to the trend curve prevents noise and interference data from easily exceeding the offset curve, thus avoiding the incorrect capture of noise and interference data as the target. It should be noted that the trend curve, being a moving average, is delayed by a fixed time interval from the last received data output by signal receiver 20. Therefore, to enable the target acquisition module 24 to perform the comparison effectively, the delay processing module 23 is provided to delay the data received by signal receiver 20 by a time interval corresponding to the time delay of the trend curve and output it to the target acquisition module 24.

[0051] Since the data output by the signal receiver 20 is amplified and recorded by the log amplifier 26, it is important to note, as described above, that the signal level, even if it is a high-level received signal (e.g., a received signal from a short distance), is not simply saturated or overdriven, and the dynamic range is wide. Therefore, the target acquisition module 24 can precisely compare the signal level of the received data with the trend curve and accurately acquire the target.

[0052] Furthermore, the target acquisition module 24 outputs a gate signal indicating whether the target has been acquired (whether the signal level of the received data exceeds the offset curve). For example, in this embodiment, the target acquisition module outputs "0" if the target is not acquired and "1" if the target is acquired. The gate signal is fed into the polar coordinate correlator 21.

[0053] The polar coordinate correlator modifies the content of the processing based on the gate signal by the polar coordinate correlator 21. Specifically, if the gate signal input is "0" (when the target is not detected), the polar coordinate correlator 21 outputs the correlated data obtained by the computational processing module 28 as a result of the scan correlation. Since the scan correlation result is output as usual when the target is not detected, as described above, the radar image can be obtained with suppressed unnecessary signals such as interference and noise.

[0054] On the other hand, when the input gate signal is “1” (the target is being acquired), the polar coordinate correlator 21 outputs the received data input by the signal receiver 20 as they are (the value without being scan-correlated) as a result of the scan correlation. Therefore, the target is not suppressed by the scan correlation, even if the target is moving at high speed. Even if the target 30 is moving at high speed, which would occur with conventional scan correlation as described in part (a) of the Fig. 3 is shown, which is suppressed, can result according to the configuration of the present embodiment as shown in part (b) of Fig. As shown in Figure 3, target 30 is clearly displayed on the radar image. This improves the distinguishability of target 30.

[0055] As described above, the radar signal processing device of this embodiment comprises the signal receiver 20, the memory of previous data 29, the polar coordinate correlator 21, the trend curve calculation module 22, and the target acquisition module 24. Furthermore, a method for processing the radar signal by the radar signal processing device according to this embodiment is carried out as described below.

[0056] Specifically, the signal receiver 20 first acquires the received data in the polar coordinate system based on the received signal. The trend curve calculation module 22 then calculates the distance-direction trend curve of the signal level of the received data in the polar coordinate system. Finally, the target acquisition module 24 acquires the target based on the signal level of the received data and the trend curve.

[0057] Before or after, the polar coordinate correlator 21 acquires the previously correlated data stored in the memory of previous data 29 in the polar coordinate system. Furthermore, the polar coordinate correlator 21 performs the correlation between the received data and the previously correlated data in the polar coordinate system to generate the correlated data. In this case, the polar coordinate correlator modifies the contents of the correlation of the received data based on the target acquisition result of the target acquisition module 24.

[0058] By modifying the content of the scan correlation based on whether the target was detected by the target acquisition module 24 as described above, target suppression due to the scan correlation can be avoided.

[0059] The following describes a modification of the above embodiment.

[0060] In the above embodiment, the polar coordinate correlator 21 switches the processing between outputting the correlated data and outputting the received data as is (the value without being scan-correlated) based on the target acquisition result of the target acquisition module 24. In this modification, the polar coordinate correlator 21 changes the filter coefficient α of the scan correlation based on the target acquisition result from the target acquisition module 24.

[0061] The filter coefficient α is a parameter for adjusting the effect of scan correlation, and the effect of scan correlation increases as the value of α increases. Therefore, it becomes easier to suppress the fast-moving target when the value of α is larger.

[0062] Therefore, in the radar signal processing device 14 of this embodiment, the polar coordinate correlator increases the filter coefficient α when the gate signal output by the target acquisition module 24 is “0” (the target was not acquired). Conversely, the polar coordinate correlator reduces the filter coefficient α when the gate signal is “1” (the target was acquired).

[0063] If the target is acquired by the target acquisition module 24, target suppression becomes more difficult because the effect of scan correlation can be reduced accordingly. Consequently, it can be prevented that even a relatively high-speed target is suppressed by scan correlation. Conversely, if the target is not acquired by the target acquisition module 24, sufficient application of the scan correlation effect can be used to obtain a radar image with suppressed interference and noise.

[0064] The following describes a further modification of the above embodiment.

[0065] As described above, the relatively high-speed moving target is captured at a position different from the immediately preceding scan. Therefore, there is a case where the remaining image appears at the target's position during the immediately preceding scan due to scan correlation. For example, a case like the one described in... Fig. Figure 2 takes into account the fact that the target was at a position with a distance r1 in the immediately previous scan and has moved to a position with a distance r2 in the last scan. In this case, the correlation between the data of the immediately previous scan and the last received data, as shown in Figure 2, can be used to determine the target position. Fig. As shown in Figure 5, the remaining image appears at a position of the target in the immediately previous scan (the position at distance r1).

[0066] Therefore, in the modification described below, the contents of the processing performed by the polar coordinate correlator 21 with respect to the gate signal are changed from the immediately previous scan in order to suppress the remaining image.

[0067] The modification is described in detail below. The polar coordinate correlator 21 of this modification includes a data acquisition memory that can store gate signals output by the target acquisition module 24 (the target acquisition result) for a scan. Furthermore, if at least the last gate signal or the gate signal of the immediately preceding gate signal stored in the data acquisition memory is "1" (the target has been acquired), the polar coordinate correlator 21 outputs the received data as is (the value without being scan-correlated) as a scan correlation result.

[0068] Specifically, a gate signal of "1" from the immediately preceding scan indicates that the target existed at least during that scan. Therefore, when performing scan correlation in such a case, there is a possibility that the remaining image at the target position will appear in the immediately preceding scan. For this reason, the polar coordinate correlator in this embodiment outputs the received data as is (the value without scan correlation) as the scan correlation result, even if the gate signal from the immediately preceding scan is "1".

[0069] Accordingly, the appearance of the remaining image at the target's position during the immediately preceding scan can be prevented. This allows for a more accurate scan correlation result.

[0070] A second embodiment of the present invention is described below. It should be noted that in the second embodiment, the configurations are identical or comparable to those of the first embodiment and are designated with the same reference numerals as in the first embodiment, although their description is omitted.

[0071] As in Fig. As shown in Figure 6, in the second embodiment, the signal receiver 20 in the radar signal processing device 101 also comprises a linear amplifier 32 in addition to the log amplifier 26. The received signal from the radar antenna 11 is amplified by the linear amplifier 32 and recorded by the A / D converter 33.

[0072] The output of the log amplifier 26 (the received data recorded by the A / D converter 27) is output to the target acquisition module 24 and the trend curve calculation module 22, similar to the first embodiment. Therefore, the target acquisition processing can be performed using the output of the log amplifier, which has a wide dynamic range and is not easily saturated, and thus the target can be acquired accurately.

[0073] On the other hand, an output from the linear amplifier 32 (the received data recorded by the A / D converter 33) is sent to the polar coordinate correlator 21. The polar coordinate correlator 21 performs the scan correlation based on the output of the linear amplifier 32. By performing the scan correlation using the output of the linear amplifier 32, which is obtained by linearly amplifying the received signal, the correlation between the previous signal level and the current signal level can be easily determined. As a result, a suitable scan correlation result can be obtained.

[0074] Although the preferred embodiments and modifications of the present invention are described above, the above configurations can be modified by the following examples.

[0075] The radar device of the present invention is not limited to radar devices for ships and can be used in radar devices for other uses.

[0076] Further processing steps can be performed after the polar coordinate correlator 21, which can be executed in the polar coordinate system. For example, processing such as ARPA (Automatic Radar Plotting Aid) can be inserted for the correlated data in the polar coordinate system output by the polar coordinate correlator 21. In simpler terms, this is processing for automatically determining the probability of a collision with the target. According to the configuration of the present invention, the target is not suppressed during scan correlation, even if it is moving at high speed; therefore, the collision risk with respect to a fast-moving target can be determined precisely.

[0077] It has been described that the target acquisition module 24 outputs the gate signal according to the target acquisition result; however, the format in which the target acquisition module 24 outputs the target acquisition result is not limited to the gate signal, as long as the contents of the processing carried out by the polar coordinate correlator 21 can be switched by the target acquisition module 24 depending on the target acquisition result.

[0078] The size of the offset added to the trend curve when acquiring the target is preferably adjustable by the operator via a suitable input. Accordingly, the offset can be set depending on a noise level or interference data level, enabling appropriate processing. A configuration in which the offset value is automatically adjusted depending on the noise level or interference data level should also be considered.

[0079] The calculation method for the trend curve is not limited to a simple average of movement, as long as a change trend in the signal level of the received data in the direction of distance can be obtained.

Claims

[1] Radar signal processing device (14) comprising: a signal receiver (20) which is configured to receive received data in a polar coordinate system based on a received signal; a data storage device for previous data, designed to store previous correlated data in the polar coordinate system; a polar coordinate correlator (21) configured to generate correlating data by establishing a correlation in the polar coordinate system between the received data and the previous correlated data stored in the data memory of previous data, have been carried out; a trend curve calculation module (22) configured to calculate a trend curve of a distance-direction signal level of the received data in the polar coordinate system; and a target acquisition module (24) which is trained to identify a target based on the signal level of the received data and the trend curve, wherein the polar coordinate correlator (21) modifies the contents of the correlation of the received data based on the target acquisition result of the target acquisition module (24), characterized by , that the signal receiver (20) has a log amplifier (26) and a linear amplifier (32) and wherein the signal receiver (20) outputs a log amplifier (26) to the trend curve calculation module (22) and the target acquisition module (24) and outputs a linear amplifier (32) to the polar coordinate correlator (21). [2] The radar signal processing device (14) according to claim 1, wherein the target acquisition module (24) acquires the target when the signal level of the received data is a predetermined level higher than the trend curve, and wherein the polar coordinate correlator (21) outputs a value of the received data without being correlated when the target acquisition module (24) acquires the target. [3] Radar signal processing device (14) according to claim 1, wherein the target acquisition module (24) acquires the target when the signal level of the receiving unit is a certain level higher than the trend curve, and wherein the polar coordinate correlator (21) changes weighting coefficients of the received data and the previously correlated data for the case in which the target is acquired by the target acquisition module (24) and the case in which the target is not acquired. [4] Radar signal processing device (14) according to at least one of claims 1 to 3, wherein the target acquisition module (24) outputs a gate signal indicating whether a target has been acquired, and wherein the polar coordinate correlator (21) modifies the contents of the correlation according to the gate signal. [5] Radar signal processing device (14) according to at least one of claims 1 to 4, comprising a data acquisition memory configured to store at least the data acquisition result from the target acquisition module (24) in a scan immediately prior to the current scan, wherein the polar coordinate correlator (21) uses at least one of the data acquisition results from the immediately preceding scan stored in the data acquisition memory and the data acquisition result of the current scan output from the target acquisition module (24). [6] Radar signal processing device (14) according to at least one of claims 1 to 5, wherein the target acquisition module (24) acquires the target when the signal level of the received data is higher than a curve corresponding to the trend curve with an added offset. [7] Radar device (10) comprising: the radar signal processing device (14) according to at least one of claims 1 to 6, a radar antenna (11) designed to receive the received signal, and a display unit (15) designed to display a radar image based on the result of the scan correlation performed by the polar coordinate correlator (21). [8] Method for processing a radar signal by a radar signal processing device (14) according to any one of the preceding claims 1 to 6 comprising: Receiving received data in a polar coordinate system based on a received signal; Receiving previously correlated data in the polar coordinate system; Generating correlated data by performing a correlation between the received data and the previously correlated data in the polar coordinate system. Calculating a trend curve of a distance-direction signal level of the received data in the polar coordinate system, and Determining a target based on the signal level of the received data and the trend curve, wherein, when generating the correlated data, the contents of the correlation of the received data are changed based on the detection of the target, wherein the signal receiver (20) has a log amplifier (26) and a linear amplifier (32) and wherein the signal receiver (20) outputs a log amplifier (26) to the trend curve calculation module (22) and the target acquisition module (24) and outputs a linear amplifier (32) to the polar coordinate correlator (21).

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