Radar device, clutter suppression method, and clutter suppression program

Abstract

To suppress clutter more reliably.SOLUTION: A radar device comprises: a transmission section that transmits radio waves; an acquisition section that acquires amplitude information indicating an amplitude of a reflected signal reflected from a target by the radio waves and phase information indicating a phase of the reflected signal; a compatibility degree calculation section that calculates a compatibility degree of clutter included in echo data based on the reflected signal using a membership function for each of the amplitude information and the phase information, the compatibility degree calculation section calculating the a first compatibility degree which is the compatibility degree corresponding to the amplitude information and a second compatibility degree which is the compatibility degree corresponding to the phase information; and a clutter suppression section that performs suppression processing of suppressing the clutter on the basis of the first compatibility degree and the second compatibility degree.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a radar device, a clutter suppression method, and a clutter suppression program. [Background technology]

[0002] A technology has been developed to suppress the influence of clutter in echo images for target detection displayed in a radar device. For example, Patent Document 1 (JP Patent Publication 2012-108057 A) discloses the following target detection method. That is, the target detection method receives reflected echoes of detection signals transmitted sequentially from a rotating antenna, and performs target detection from detection data obtained by sampling the received signals at a predetermined timing interval, and includes a temporary storage step of temporarily storing detection data within a predetermined range, and an echo identification step of identifying the type of the reflected echo based on the fluctuation of adjacent detection data values ​​within the predetermined range. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2012-108057 A [Patent Document 2] JP 2021-113696 A Summary of the Invention [Problem to be solved by the invention]

[0004] There is a demand for a technique that goes beyond the technique described in Patent Document 1 and is capable of suppressing clutter more reliably.

[0005] The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a radar device, a clutter suppression method, and a clutter suppression program that are capable of suppressing clutter more reliably. [Means for solving the problem]

[0006] (1) In order to solve the above problem, a radar device according to one aspect of the present invention includes a transmitter that transmits radio waves; an acquirer that acquires amplitude information indicating an amplitude of a reflected signal of the radio waves reflected by a target and phase information indicating a phase of the reflected signal; a conformance calculator that calculates a conformance of clutter included in echo data based on the reflected signal by using a membership function for each of the amplitude information and the phase information, the conformance calculator calculating a first conformance that is the conformance corresponding to the amplitude information and a second conformance that is the conformance corresponding to the phase information; and a clutter suppressor that performs a suppression process to suppress the clutter based on the first conformance and the second conformance.

[0007] In this way, when estimating whether or not clutter is included in echo data based on a reflected signal, the accuracy of estimation can be improved by using the phase of the reflected signal in addition to the amplitude of the reflected signal. Also, by calculating the compatibility of clutter using a membership function for each of the amplitude and phase of the reflected signal, it is possible to estimate whether or not clutter is included in the echo data by fuzzy inference, so that clutter to be suppressed can be accurately detected. Therefore, clutter can be suppressed more reliably.

[0008] (2) In the above (1), the radar device may further include a determination unit that makes a determination regarding the clutter based on the first conformance and the second conformance, and a display processing unit that performs processing to display a result of the determination made by the determination unit.

[0009] With this configuration, it is possible to display locations where clutter is occurring in an echo image that shows the presence or absence of targets in the detection area, thereby enabling the user to recognize those locations as areas where it is raining or the like, which can cause clutter.

[0010] (3) In the above (1) or (2), the phase information may include a Doppler velocity width of the reflected signal.

[0011] For example, the Doppler velocity width of clutter generated when radio waves transmitted from a radar device are reflected by rain is larger than the Doppler velocity width of clutter generated when the radio waves are reflected by land. With the above-mentioned configuration, it is possible to distinguish between clutter generated when radio waves are reflected by rain and clutter generated when radio waves are reflected by land.

[0012] (4) In any one of (1) to (3) above, the phase information may include a vector coincidence of the reflected signal, as expressed by the following equation (1):

number

[0013] For example, the vector coincidence degree of clutter generated by radio waves transmitted from a radar device reflecting off land is greater than the vector coincidence degree of clutter generated by the same radio waves reflecting off rain. With the above-described configuration, it is possible to distinguish between clutter generated by radio waves reflecting off rain and clutter generated by radio waves reflecting off land.

[0014] (5) In the above (3) or (4), the acquisition unit may perform a filtering process to smooth a waveform indicated by the reflected signal, and the amplitude information may include a correction value of the amplitude of the reflected signal after the filtering process.

[0015] In this manner, by using the correction value of the amplitude of the filtered reflected signal to estimate whether or not clutter is included in the echo data based on the reflected signal, clutter to be suppressed can be detected more accurately.

[0016] (6) In any of (1) to (5) above, the compatibility calculation unit may further weight the first compatibility and the second compatibility, and add the weighted first compatibility and the weighted second compatibility, and the clutter suppression unit may perform the suppression process using normalized data, which is data obtained by normalizing a result of the addition by the compatibility calculation unit.

[0017] For example, the difference between the phase of the reflected signal from the target and the phase of the clutter is larger than the difference between the amplitude of the reflected signal from the target and the amplitude of the clutter. With the above-mentioned configuration, for example, by making the weighting of the second goodness of fit corresponding to the phase larger than the weighting of the first goodness of fit corresponding to the amplitude, it is possible to more accurately estimate whether or not the echo data based on the received reflected signal contains clutter, and therefore it is possible to more reliably suppress clutter.

[0018] (7) In the above (6), the clutter suppression unit may perform a threshold calculation process to calculate a threshold for suppressing the clutter based on the normalized data, and the clutter suppression unit may subtract the threshold from the echo data in the suppression process.

[0019] With this configuration, clutter contained in echo data can be easily suppressed by using a threshold based on the compatibility of the clutter calculated by fuzzy inference.

[0020] (8) In the above (7), the transmitter may transmit the radio waves via a rotating antenna, and the clutter suppression unit may, in the threshold calculation process, calculate a first threshold, which is the threshold in the rotation direction of the antenna, using the following equation (2), and calculate a second threshold, which is the threshold in the direction from the radar device toward the target, using the following equation (3), and the clutter suppression unit may subtract the second threshold from the echo data in the suppression process. Tha[i] = Tha[i] × W1 × (1-Q) +(S[i]×(1-W1×(1-Q))) ···(2) Thb[i] = Thb[i-1] × W2 × (1-Q) +(Tha[i]×(1-W2×(1-Q))) ···(3) where Tha[i] is the first threshold, Thb[i] is the second threshold, S[i] is the echo data, W1 and W2 are predetermined coefficients, Q is the normalized data, and i is an integer greater than or equal to zero and less than the number of samples.

[0021] With this configuration, the threshold value used for suppressing clutter can be easily calculated by substituting the goodness of fit of the clutter corresponding to the amplitude of the reflected signal and the normalized data based on the goodness of fit of the clutter corresponding to the phase of the reflected signal into a predetermined calculation formula.

[0022] (9) In any of (1) to (6) above, the clutter suppression unit may replace, in the suppression process, the echo data for which the first conformance is equal to or greater than a predetermined first threshold or the second conformance is equal to or greater than a predetermined second threshold, with zero.

[0023] With this configuration, it is possible to estimate whether or not clutter is included in the echo data according to the value of the goodness of fit calculated by fuzzy inference, and if clutter is included in the echo data, the echo data can be replaced with zero, thereby making it possible to suppress the clutter more reliably.

[0024] (10) In order to solve the above-mentioned problems, a clutter suppression method according to one aspect of the present invention is a clutter suppression method in a radar device, which transmits radio waves, obtains amplitude information indicating the amplitude of a reflected signal of the radio waves reflected by a target, and phase information indicating the phase of the reflected signal, calculates a first goodness of fit corresponding to the amplitude information and a second goodness of fit corresponding to the phase information as goodness of fit of clutter included in echo data based on the reflected signal by using membership functions for each of the amplitude information and the phase information, and performs a suppression process to suppress the clutter based on the first goodness of fit and the second goodness of fit.

[0025] In this way, when estimating whether or not clutter is included in echo data based on a reflected signal, the accuracy of estimation can be improved by using the phase of the reflected signal in addition to the amplitude of the reflected signal. Also, by calculating the compatibility of clutter using a membership function for each of the amplitude and phase of the reflected signal, it is possible to estimate whether or not clutter is included in the echo data by fuzzy inference, so that clutter to be suppressed can be accurately detected. Therefore, clutter can be suppressed more reliably.

[0026] (11) In order to solve the above-mentioned problems, a clutter suppression program according to an aspect of the present invention is a clutter suppression program used in a radar device, the program causing a computer to execute the following processes: transmitting radio waves; acquiring amplitude information indicating the amplitude of a reflected signal of the radio waves reflected by a target and phase information indicating the phase of the reflected signal; calculating a first goodness of fit corresponding to the amplitude information and a second goodness of fit corresponding to the phase information by using membership functions for each of the amplitude information and the phase information as goodness of fit of clutter included in echo data based on the reflected signal; and suppressing the clutter based on the first goodness of fit and the second goodness of fit.

[0027] In this way, when estimating whether or not clutter is included in echo data based on a reflected signal, the accuracy of estimation can be improved by using the phase of the reflected signal in addition to the amplitude of the reflected signal. Also, by calculating the compatibility of clutter using a membership function for each of the amplitude and phase of the reflected signal, it is possible to estimate whether or not clutter is included in the echo data by fuzzy inference, so that clutter to be suppressed can be accurately detected. Therefore, clutter can be suppressed more reliably. Effect of the Invention

[0028] According to the present invention, clutter can be suppressed more reliably. [Brief description of the drawings]

[0029] [Figure 1] FIG. 1 is a diagram showing a configuration of a radar device according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a diagram showing an example of an echo image displayed by the radar device according to the embodiment of the present invention. [Diagram 3] FIG. 3 is a diagram illustrating an example of the configuration of an acquisition unit in the radar device according to the embodiment of the present invention. [Figure 4] FIG. 4 is a diagram showing an example of an echo image displayed by the radar device according to the embodiment of the present invention using the calculation result of the Doppler velocity width of the reflected signal. [Diagram 5] FIG. 5 is a diagram showing an example of an echo image displayed by the radar device according to the embodiment of the present invention using the calculation result of the vector coincidence degree of the reflected signal. [Figure 6] FIG. 6 is a diagram showing an example of a reflected signal smoothed by the radar device according to the embodiment of the present invention. [Figure 7] FIG. 7 is a diagram for explaining the correction process performed by the radar device according to the embodiment of the present invention. [Figure 8] FIG. 8 is a diagram showing an example of an echo image displayed by the radar device according to the embodiment of the present invention using the calculation result of the correction value of the amplitude of the reflected signal. [Figure 9] FIG. 9 is a diagram showing an example of a membership function used in the compatibility calculation process performed by the radar device according to the embodiment of the present invention. [Figure 10] FIG. 10 is a diagram showing another example of the membership function used in the compatibility calculation process by the radar device according to the embodiment of the present invention. [Figure 11] FIG. 11 is a diagram showing another example of the membership function used in the compatibility calculation process by the radar device according to the embodiment of the present invention. [Figure 12]FIG. 12 is a diagram showing another example of an echo image displayed by the radar device according to the embodiment of the present invention. [Figure 13] FIG. 13 is a diagram showing another example of an echo image displayed by the radar device according to the embodiment of the present invention. [Figure 14] FIG. 14 is a flowchart defining an operation procedure when the radar device according to the embodiment of the present invention performs the suppression process. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0030] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference characters and their description will not be repeated. In addition, at least some of the embodiments described below may be arbitrarily combined.

[0031] <Radar device configuration> Fig. 1 is a diagram showing a configuration of a radar device according to an embodiment of the present invention. Referring to Fig. 1, a radar device 301 includes a radar unit 201 and a display processing unit 202. The radar unit 201 includes a transmission control unit 21, a transmission unit 22, a transmission antenna 23, a reception antenna 24, a reception unit 25, an A / D conversion unit 26, an acquisition unit 27, a compatibility calculation unit 28, a clutter suppression unit 29, and a determination unit 30. A part or all of the transmission control unit 21, the acquisition unit 27, the compatibility calculation unit 28, the clutter suppression unit 29, the determination unit 30, and the display processing unit 202 are realized, for example, by a processing circuit including one or more processors.

[0032] The radar device 301 is, for example, a pulse radar device. The radar device 301 is mounted on, for example, a ship. The radar device 301 performs processing to display, on a display device (not shown), an echo image indicating the presence or absence of a target in a detection target area that is an area monitored by the ship, and the distance between the radar device 301 and the target. The ship is an example of a surface vehicle.

[0033] The radar device 301 is not limited to a pulse-type radar device, but may be a radar device of another type different from the pulse type, for example, a frequency modulated continuous wave (FM-CW) type.

[0034] The radar unit 201 outputs echo data indicating the detection result of the target object in the detection target area to the display processing unit 202. The transmitting antenna 23 and the receiving antenna 24 rotate so that the azimuth angle of the radiation direction of the radio wave by the transmitting antenna 23 changes by a predetermined angle for each predetermined sweep period St. This allows the radar unit 201 to detect targets existing in all directions around the ship on which its radar device 301 is mounted. Hereinafter, the rotation direction of the transmitting antenna 23 and the receiving antenna 24 is also referred to as the "azimuth direction". In addition, the operation of rotating the receiving antenna 24 360 degrees to receive the reflected signal is also referred to as the "scan".

[0035] The radar unit 201 outputs to the display processing unit 202 echo data indicating the detection result of the target in the detection area for each sweep period St.

[0036] The display processing unit 202 performs processing for displaying an echo image in the detection target area on a display device based on the multiple echo data received from the radar unit 201 .

[0037] FIG. 2 is a diagram showing an example of an echo image displayed by the radar device according to the embodiment of the present invention.

[0038] 2, the echo image G1 shows the intensity of a reflected signal from a target (hereinafter also referred to as a "target echo C1") and the intensity of clutter C2. The clutter C2 is a reflected signal that is a radio wave transmitted from the radar device 301 and reflected by rain, snow, land, the sea surface, etc.

[0039] 2, the echo image G1 shows the intensity of rain clutter C21, which is clutter C2, and the intensity of land clutter C22, which is clutter C2. The rain clutter C21 is clutter that occurs when the radio waves transmitted from the radar device 301 are reflected by rain. The land clutter C22 is clutter that occurs when the radio waves are reflected by land.

[0040] Furthermore, the echo image G1 shows the intensity of the reflected signal from a stationary target (hereinafter also referred to as the "stationary target echo C11") and the intensity of the reflected signal from a moving target (hereinafter also referred to as the "moving target echo C12").

[0041] [Radar section] The transmitter 22 transmits radio waves via a rotating transmission antenna 23. More specifically, for example, the transmitter 22 transmits pulsed radio waves (hereinafter also referred to as "transmission waves") during a sweep period St.

[0042] Specifically, for example, the transmission control unit 21 outputs a pulse-shaped transmission trigger to the transmission unit 22.

[0043] The transmitter 22 generates a transmission wave in accordance with a transmission trigger received from the transmission control unit 21. Then, the transmitter 22 transmits the generated transmission wave to the detection target area via the rotating transmission antenna 23. The transmitter 22 includes, for example, a magnetron used to generate the transmission wave. The transmitter 22 generates a transmission wave with a frequency specific to the magnetron.

[0044] The receiving unit 25 receives a reflected signal of the transmitted wave reflected by a target object or the like. More specifically, the receiving unit 25 receives a reflected signal in the RF band, which is a signal of the transmitted wave reflected by a target object or the like in the detection target area, via the rotating receiving antenna 24. The receiving unit 25 outputs the received reflected signal to the A / D conversion unit 26.

[0045] Specifically, for example, the receiving unit 25 includes a low-noise amplifier. The low-noise amplifier amplifies a reflected signal in the RF band received via the receiving antenna 24, and outputs the amplified signal to the A / D conversion unit .

[0046] The A / D conversion unit 26 converts the reflected signal SA, which is an analog signal received from the receiving unit 25, into a reflected signal SD, which is a digital signal, by sampling it at a predetermined sampling frequency fs, and outputs it to the acquisition unit 27, the clutter suppression unit 29, and the judgment unit 30.

[0047] Specifically, for example, the A / D conversion unit 26 generates N reflected signals SD by performing sampling at a sampling frequency fs for each sweep period St, and outputs the signals to the acquisition unit 27. N is an integer of 1 or more.

[0048] The acquiring unit 27 acquires phase information indicating the phase of the reflected signal SD and amplitude information indicating the amplitude of the reflected signal SD.

[0049] Fig. 3 is a diagram showing an example of a configuration of an acquisition unit in a radar device according to an embodiment of the present invention. With reference to Fig. 3, the acquisition unit 27 includes a speed width calculation unit 31, a vector coincidence calculation unit 32, and a correction value calculation unit 33. The correction value calculation unit 33 includes an LPF (Low Pass Filter) 41, a correction unit 42, and an offset generation unit 43.

[0050] (Doppler velocity range) More specifically, for example, the phase information includes a Doppler velocity width of the reflected signal SD. Specifically, for example, the velocity width calculation unit 31 calculates the Doppler velocity width σ using an autocorrelation function R(j) for the reflected signal SD received from the A / D conversion unit 26. The autocorrelation function R(j) is expressed, for example, by the following equation (4). In equation (4), S(i) is the i-th reflected signal SD among the N reflected signals SD, and S(i+j) is the i+j-th reflected signal SD among the N reflected signals SD. j is a value within a range from zero to N.

[0051]

number

[0052] The acquisition unit 27 calculates the autocorrelation function R(T) in equation (4) when j is a number corresponding to the pulse repetition period T of the transmission wave. The acquisition unit 27 also calculates the autocorrelation function R(0) in equation (4) when j is zero.

[0053] Then, the acquisition unit 27 calculates the Doppler velocity width of the reflected signal SD by substituting the autocorrelation functions R(T) and R(0) into the following equation (5): In equation (5), σ is the Doppler velocity width, and λ is the wavelength of the transmission wave.

[0054]

number

[0055] The Doppler velocity width σ of the rain clutter is a value different from the Doppler velocity width σ of the land clutter. For example, the Doppler velocity width σ of the rain clutter is a value larger than the Doppler velocity width σ of the land clutter. After calculating the Doppler velocity width of the reflected signal SD, the acquisition unit 27 outputs the calculated Doppler velocity width to the compatibility calculation unit 28.

[0056] The radar device 301 may be configured to determine the type of the received reflected signal using the calculated Doppler velocity width and display the determination result on the display device. In this case, for example, when the calculated Doppler velocity width is equal to or greater than a predetermined threshold Th1, the acquisition unit 27 determines that the reflected signal corresponding to the calculated Doppler velocity width is rain clutter. On the other hand, when the calculated Doppler velocity width is less than the threshold Th1, the acquisition unit 27 determines that the reflected signal corresponding to the calculated Doppler velocity width is not rain clutter. Then, the acquisition unit 27 outputs determination result information P1 indicating the determination result of the reflected signal using the Doppler velocity width to the display processing unit 202.

[0057] FIG. 4 is a diagram showing an example of an echo image displayed by the radar device according to the embodiment of the present invention using the calculation result of the Doppler velocity width of the reflected signal.

[0058] 4, for example, the display processing unit 202 displays on the display device an echo image G2 indicating the result of the determination of the reflected signal using the Doppler velocity width, based on the determination result information P1 received from the acquisition unit 27. In the echo image G2, the rain clutter C21, whose Doppler velocity width is equal to or greater than the threshold Th1, is hatched, and the land clutter C22 and the target echo C1, whose Doppler velocity width is less than the threshold Th1, are not hatched.

[0059] (Vector similarity) Furthermore, for example, the phase information includes the vector coincidence of the reflected signal SD, expressed by the following formula (6), in addition to the Doppler velocity range: CPA is the vector coincidence, N is the number of samples, and xi is a complex component of the reflected signal.

[0060] 3 again, specifically, for example, the acquisition unit 27 calculates the vector coincidence degree by substituting the N reflected signals SD received from the A / D conversion unit 26 into the following formula (6). The vector coincidence degree is, for example, a value within a range from zero to one.

[0061]

number

[0062] The vector agreement CPA of the rain clutter is a value different from the vector agreement CPA of the land clutter. For example, the vector agreement CPA of the rain clutter is a value smaller than the vector agreement CPA of the land clutter. After calculating the vector agreement CPA of the reflected signal SD, the acquisition unit 27 outputs the calculated vector agreement CPA to the compatibility calculation unit 28.

[0063] The radar device 301 may be configured to determine the type of the received reflected signal using the calculated vector coincidence and display the determination result on the display device. In this case, for example, when the calculated vector coincidence is equal to or greater than a predetermined threshold Th2, the acquisition unit 27 determines that the reflected signal corresponding to the vector coincidence is a land clutter or a stationary target echo. On the other hand, when the calculated vector coincidence is less than the threshold Th2, the acquisition unit 27 determines that the reflected signal corresponding to the vector coincidence is neither a land clutter nor a stationary target echo C11. Then, the acquisition unit 27 outputs determination result information P2 indicating the determination result of the reflected signal using the vector coincidence to the display processing unit 202.

[0064] FIG. 5 is a diagram showing an example of an echo image displayed by the radar device according to the embodiment of the present invention using the calculation result of the vector coincidence degree of the reflected signal.

[0065] 5, for example, the display processing unit 202 displays on the display device an echo image G3 indicating the result of the determination of the reflected signal using the vector coincidence degree, based on the determination result information P2 received from the acquisition unit 27. In the echo image G3, the land clutter C22 and the stationary target echo C11, whose vector coincidence degree is equal to or greater than the threshold value Th2, are hatched, and the rain clutter C21 and the moving target echo C12, whose vector coincidence degree is less than the threshold value Th2, are not hatched.

[0066] The acquiring unit 27 may acquire one of the Doppler velocity range and the vector coincidence as the phase information. The radar device 301 may acquire, as the phase information, another index value indicating the phase of the reflected signal, in addition to the Doppler velocity range and the vector coincidence.

[0067] (correction value for the amplitude of the reflected signal) For example, in the correction value calculation unit 33, the LPF 41 performs a filtering process to smooth the waveform indicated by the reflected signal SD received from the A / D conversion unit 26. The LPF 41 is, for example, an IIR (Infinite Impulse Response) filter.

[0068] In this embodiment, for example, the correction value calculation unit 33 acquires, as amplitude information, a correction value M of the amplitude of the waveform indicated by the filtered reflected signal SD. For simplicity of description, the amplitude of the waveform indicated by the reflected signal SD, which is a digital signal, will be simply referred to as the "amplitude of the reflected signal SD."

[0069] 6 is a diagram showing an example of a reflected signal smoothed by the radar device according to the embodiment of the present invention, in which the horizontal axis indicates the distance L from the radar device 301, and the vertical axis indicates the amplitude.

[0070] 6, graph E1, indicated by a solid line, shows the relationship between the amplitude of the reflected signal SD before filtering and the distance. Graph E2, indicated by a dashed line, shows the relationship between the amplitude of the reflected signal SD after filtering and the distance. As shown in graphs E1 and E2, the amplitude of the reflected signal SD after filtering is shifted in the direction from the radar device 301 toward the target (hereinafter also referred to as the "distance direction") relative to the amplitude of the reflected signal SD before filtering. In other words, the reflected signal SD after filtering is delayed in the distance direction relative to the reflected signal SD before filtering.

[0071] Referring back to FIG. 3, the LPF 41 outputs the filtered reflected signal SD to the correction unit 42 and the offset generation unit 43.

[0072] The correction unit 42 performs a correction process to correct the reflected signal SD that has passed through the LPF 41. Specifically, for example, the correction unit 42 calculates a difference value B1 between the amplitude of the reflected signal SD after filtering shown in graph E2 and the amplitude of the reflected signal SD before filtering shown in graph E1 for each distance L from the radar device 301. Then, the correction unit 42 checks whether the calculated difference value B1 is equal to or greater than a predetermined threshold value Tb for each distance L.

[0073] 7 is a diagram for explaining the correction process by the radar device according to the embodiment of the present invention. In FIG. 7, the graph E3 shown by the solid line shows the relationship between the amplitude and distance of the reflected signal SD after the correction process. The graph E2 shown by the dashed line shows the relationship between the amplitude and distance of the reflected signal SD before the correction process, that is, the relationship between the amplitude and distance of the reflected signal SD after the filtering process shown in FIG. 6.

[0074] 3 and 7, the correction unit 42 estimates a delay amount D of the amplitude of the filtered reflected signal SD shown in graph E2 for each distance L based on a filter coefficient used in the filtering process by the LPF 41. The correction unit 42 then shifts the amplitude of the filtered reflected signal SD at a distance where the difference value B1 is less than the threshold value Tb by the estimated delay amount D in a direction toward the radar device 301. The correction unit 42 outputs the corrected reflected signal SD to the offset generation unit 43.

[0075] 6 and 7, offset generation unit 43 calculates a difference value B2 between the amplitude of reflected signal SD before filtering shown in graph E1 and the amplitude of reflected signal SD after correction shown in graph E3 for each distance L. Offset generation unit 43 repeats the process of calculating difference value B2 for each distance L a predetermined number of scans.

[0076] Then, the offset generating unit 43 calculates a statistical value of the difference value B2 for each distance L. For example, the offset generating unit 43 calculates a standard deviation H of the difference value B2 for each distance L as the statistical value.

[0077] After calculating the standard deviation H for each distance L, the offset generating unit 43 multiplies the standard deviation H by a predetermined coefficient α to calculate an offset value.

[0078] Then, the offset generating unit 43 calculates a correction value M by adding the amplitude of the corrected reflected signal SD shown in the graph E3 to the calculated offset value for each distance L. The acquiring unit 27 outputs the calculated correction value M to the compatibility calculating unit 28.

[0079] The radar device 301 may be configured to determine the type of the received reflected signal using the calculated correction value M and display the determination result on the display device. In this case, for example, when the calculated correction value M is equal to or greater than a predetermined threshold Th3, the acquisition unit 27 determines that the reflected signal corresponding to the correction value M is clutter C2. On the other hand, when the calculated correction value M is less than the threshold Th3, the acquisition unit 27 determines that the reflected signal corresponding to the correction value M is not clutter C2. Then, the acquisition unit 27 outputs determination result information P3 indicating the determination result of the reflected signal using the correction value M to the display processing unit 202.

[0080] Moreover, the acquiring unit 27 may acquire, as the amplitude information, not only the correction value M but also other index values ​​indicating the amplitude of the reflected signal.

[0081] FIG. 8 is a diagram showing an example of an echo image displayed by the radar device according to the embodiment of the present invention using the calculation result of the correction value of the amplitude of the reflected signal.

[0082] 8, the display processing unit 202 displays on the display device an echo image G4 indicating the result of the determination of the reflected signal using the correction value M, based on the determination result information P3 received from the acquisition unit 27. In the echo image G4, the clutter C2 whose correction value M is equal to or greater than the threshold value Th3, i.e., the rain clutter C21 and the land clutter C22, are hatched, and the target echo C1 whose correction value M is less than the threshold value Th3, i.e., the stationary target echo C11 and the moving target echo C12, are not hatched.

[0083] (Calculation of compatibility) The compatibility calculation unit 28 performs a compatibility calculation process to calculate the compatibility of clutter included in echo data based on a reflected signal for each distance L by using a membership function for each of the amplitude information and the phase information. The compatibility is an index value indicating the possibility that the echo data includes clutter.

[0084] More specifically, the compatibility calculation unit 28 calculates compatibility A11, A12 corresponding to the amplitude information and compatibility A2 corresponding to the phase information. The compatibility A11, A12 are an example of a first compatibility, and the compatibility A2 is an example of a second compatibility.

[0085] Specifically, for example, in the compatibility calculation process, the compatibility calculation unit 28 calculates a compatibility A11 corresponding to the Doppler velocity width, which is an example of amplitude information, a compatibility A12 corresponding to the vector coincidence, which is an example of amplitude information, and a compatibility A2 corresponding to the correction value M, which is an example of amplitude information.

[0086] Fig. 9 is a diagram showing an example of a membership function used in the suitability calculation process by the radar device according to the embodiment of the present invention. Fig. 9 is a diagram showing a membership function F1, which is a membership function F used to calculate the suitability A11. In Fig. 9, the horizontal axis represents the Doppler velocity width σ, and the vertical axis represents the suitability A11.

[0087] 9, in the membership function F1, the goodness of fit A11 increases in proportion to the Doppler velocity range σ within the range of 2.3 to 11.8. Moreover, the goodness of fit A11 is a constant value within the range of 11.8 to 15. In the example shown in FIG. 9, the value of the goodness of fit A11 increases from zero to 255 within the range of 2.3 to 11.8 of the Doppler velocity range σ. Moreover, the value of the goodness of fit A11 is 255 within the range of 11.8 to 15 of the Doppler velocity range σ. That is, for example, the goodness of fit A11 is a value within the range of zero to 255.

[0088] Fig. 10 is a diagram showing another example of the membership function used in the compatibility calculation process by the radar device according to the embodiment of the present invention. Fig. 10 is a diagram showing a membership function F2 which is the membership function F used to calculate the compatibility A12. In Fig. 10, the horizontal axis indicates the vector matching degree CPA, and the vertical axis indicates the compatibility A12.

[0089] 10, in the membership function F2, the goodness of fit A12 is a constant value when the vector matching degree CPA is in the range of zero to 0.5. Also, the goodness of fit A12 decreases when the vector matching degree CPA is in the range of 0.5 to 0.94. In the example shown in FIG. 10, the value of the goodness of fit A12 is 255 when the vector matching degree CPA is in the range of zero to 0.5. Also, the value of the goodness of fit A12 decreases from 255 to zero when the vector matching degree CPA is in the range of 0.5 to 0.94. That is, for example, the goodness of fit A12 is a value in the range of zero to 255.

[0090] Fig. 11 is a diagram showing another example of the membership function used in the fitness calculation process by the radar device according to the embodiment of the present invention. Fig. 11 is a diagram showing a membership function F3 which is the membership function F used to calculate the fitness A2. In Fig. 11, the horizontal axis represents the correction value M, and the vertical axis represents the fitness A2.

[0091] 11, in membership function F3, the goodness of fit A2 increases in proportion to the correction value M when the correction value M is in the range of 63 to 140. Moreover, the goodness of fit A2 is a constant value when the correction value M is in the range of 140 to 250. In the example shown in FIG. 11, the value of the goodness of fit A2 increases from zero to 255 when the correction value M is in the range of 63 to 140. Moreover, the value of the goodness of fit A2 is 255 when the correction value M is in the range of 140 to 250. That is, for example, the goodness of fit A2 is a value in the range of zero to 255.

[0092] When the compatibility calculation unit 28 calculates the compatibility A11, A12, it determines, for each distance L, the compatibility A11, A12 having the smaller value as the compatibility A10 at that distance L. As described above, the compatibility A11, A12 are values ​​within the range from zero to 255, for example. Therefore, the compatibility A10 is a value within the range from zero to 255, for example.

[0093] Then, for example, the compatibility calculation unit 28 weights the compatibility A10 and the compatibility A2 for each distance L, and adds the weighted compatibility A10 and the weighted compatibility A2. Then, the compatibility calculation unit 28 standardizes the addition result. Hereinafter, the addition result standardized by the compatibility calculation unit 28 is also referred to as "weighted compatibility Q." The weighted compatibility Q is an example of standardized data.

[0094] More specifically, for example, the compatibility calculation unit 28 calculates the weighted compatibility Q by standardizing the sum of the compatibility A10 multiplied by a predetermined weighting coefficient K1 and the compatibility A10 multiplied by a predetermined weighting coefficient K2 using the sum of the weighting coefficient K1 and the weighting coefficient K2.

[0095] Specifically, for example, the compatibility calculation unit 28 substitutes the compatibility A10 and the compatibility A2 into the following formula (7): In formula (7), G is the weighted compatibility Q, and U is a predetermined coefficient. Q=U×(K1×A10+K2×A2) / (K1+K2) ···(7)

[0096] For example, the weighted fitness Q is a value in the range from zero to 1. Here, as described above, the fitnesses A10 and A2 are values ​​in the range from zero to 255. The coefficient U in equation (7) is a coefficient for converting the value of the weighted fitness Q from a value in the range from zero to 255 to a value in the range from zero to 1. Specifically, for example, the coefficient U is the reciprocal of the value obtained by adding the maximum value of the fitness A10 and the maximum value of the fitness A2.

[0097] In this embodiment, for example, the value of the weighting coefficient K1 is 2, and the value of the weighting coefficient K2 is 1. The compatibility calculation unit 28 may be configured to weight the compatibility A11 corresponding to the Doppler velocity width, the compatibility A12 corresponding to the vector coincidence, and the compatibility A2 corresponding to the correction value M, without determining the compatibility A10, and calculate the weighted compatibility Q by adding the weighted compatibility A11, the weighted compatibility A12, and the weighted compatibility A2.

[0098] As described above, the Doppler velocity width σ of rain clutter is a different value from the Doppler velocity width σ of land clutter. Also, the vector coincidence CPA of rain clutter is a different value from the vector coincidence CPA of land clutter. Therefore, the weighted conformance Q of rain clutter is a different value from the weighted conformance Q of land clutter. For example, the weighted conformance Q of rain clutter is a value close to zero, and the weighted conformance Q of land clutter is a value close to 1.

[0099] Referring back to FIG. 1, the compatibility calculation unit 28 outputs the calculated weighted compatibility Q at each distance L to the clutter suppression unit 29 and the determination unit 30.

[0100] (Clutter suppression) The clutter suppressor 29 performs suppression processing to suppress clutter based on the compatibility A10 and the compatibility A2.

[0101] More specifically, for example, the clutter suppression unit 29 performs the suppression process using data obtained by standardizing the sum of the weighted fitness A10 and the weighted fitness A2 calculated by the fitness calculation unit 28, i.e., the weighted fitness Q.

[0102] Specifically, for example, the clutter suppression unit 29 performs a threshold calculation process to calculate a threshold for suppressing clutter (hereinafter also referred to as a "suppression threshold") based on the weighted compatibility Q received from the compatibility calculation unit 28. Then, in the suppression process, the clutter suppression unit 29 subtracts the suppression threshold from the echo data.

[0103] For example, in the threshold calculation process, the clutter suppression unit 29 calculates a suppression threshold Tha which is a suppression threshold in the azimuth direction, and a suppression threshold Thb which is a suppression threshold in the distance direction.

[0104] For example, the clutter suppression unit 29 calculates the suppression threshold value Tha and the suppression threshold value Thb for each reflected signal SD received from the A / D conversion unit 26 by substituting the weighted compatibility Q received from the compatibility calculation unit 28 into the following equations (8) and (9). In equations (8) and (9), i is an integer equal to or greater than zero and equal to or less than the number of samples N, W1 is a filter coefficient in the azimuth direction, W2 is a filter coefficient in the range direction, and S[i] is echo data based on the reflected signal SD. Tha[i] = Tha[i] × W1 × (1-Q) +(S[i]×(1-W1×(1-Q))) ···(8) Thb[i] = Thb[i-1] × W2 × (1-Q) +(Tha[i]×(1-W2×(1-Q))) ···(9)

[0105] After calculating the suppression thresholds Tha and Thb, the clutter suppression unit 29 subtracts the suppression threshold Thb from the echo data, and outputs the echo data after subtraction to the display processing unit 202.

[0106] As described above, the weighted fitness Q of rain clutter is a different value from the weighted fitness Q of land clutter. Therefore, the suppression threshold Tha corresponding to rain clutter is a different value from the suppression threshold Tha corresponding to rain clutter, and the suppression threshold Thb corresponding to rain clutter is a different value from the suppression threshold Thb corresponding to rain clutter. Therefore, for example, the clutter suppression unit 29 can perform processing to suppress one of rain clutter and land clutter and not suppress the other, depending on the values ​​of the suppression thresholds Tha and Thb.

[0107] For example, when the value of the weighted fitness Q in formulas (8) and (9) is close to zero, the clutter suppression unit 29 suppresses rain clutter but does not suppress land clutter, thereby making it possible to prevent a decrease in visibility of land clutter.

[0108] The display processing unit 202 performs processing for displaying an echo image in the detection target area on a display device based on the echo data received from the clutter suppression unit 29 .

[0109] Fig. 12 is a diagram showing another example of an echo image displayed by the radar device according to the embodiment of the present invention, which shows an echo image G5 when the clutter suppression unit 29 suppresses rain clutter but does not suppress land clutter in the suppression process.

[0110] 1 and 12, when the clutter suppression unit 29 suppresses rain clutter, the intensity of the rain clutter, i.e., the echo level of the rain clutter, becomes smaller than the echo level of the rain clutter before the suppression process. For example, in echo image G5, the echo level of the rain clutter C21 is smaller than the echo level of echo image G2 shown in Fig. 4. Therefore, in the example shown in Fig. 12, the rain clutter C21 is hatched differently from the rain clutter C21 shown in Fig. 4. Moreover, the stationary target echo C11, the moving target echo C12, and the unsuppressed land clutter C22 are not hatched.

[0111] (Judgment Department) For example, the determination unit 30 performs a determination regarding clutter (hereinafter also referred to as a "clutter determination process") based on the degree of conformance A10 and the degree of conformance A2. In this embodiment, in the clutter determination process, the determination unit 30 performs a determination regarding rain clutter based on the degree of conformance A10 and the degree of conformance A2.

[0112] More specifically, for example, in the clutter determination process, the determination unit 30 determines whether or not the weighted conformance Q received from the conformance calculation unit 28 is equal to or greater than a predetermined threshold value Tc for each reflected signal SD received from the A / D conversion unit 26.

[0113] When the weighted fitness Q from the fitness calculation unit 28 is equal to or greater than the threshold Tc, the determination unit 30 determines that the reflected signal SD corresponding to the weighted fitness Q is a reflected signal based on rain clutter. When determining whether or not a reflected signal received at time t is a rain clutter based on the difference between the intensity of the reflected signal received at time t and the intensity of the reflected signal received at a time before time t, if the difference is small, the reflected signal may be erroneously determined to be noise. In contrast, in the present embodiment, the weighted fitness Q calculated by fuzzy inference is used to perform clutter determination processing, thereby making it possible to suppress erroneous determination of the received reflected signal as noise.

[0114] Then, the determination unit 30 outputs determination result information P4 indicating the determination result to the display processing unit 202. For example, the determination unit 30 outputs information indicating the distance L corresponding to the reflected signal SD for which the weighted conformance Q is equal to or greater than the threshold value Tc to the display processing unit 202 as the determination result information P4.

[0115] On the other hand, when the weighted goodness of fit Q from the goodness of fit calculation section 28 is less than the threshold value Tc, the determination section 30 determines that the reflected signal SD corresponding to the weighted goodness of fit Q is not a reflected signal based on rain clutter.

[0116] (Display processing unit) For example, the display processing unit 202 performs a process of displaying the determination result by the determining unit 30. More specifically, for example, when the display processing unit 202 receives the determination result information P4 from the determining unit 30, the display processing unit 202 displays a portion of the echo image corresponding to the distance L indicated by the determination result information P4 in a color different from other portions. That is, the display processing unit 202 displays the rain clutter in a color different from the target echo C1 and the like in the echo image.

[0117] FIG. 13 is a diagram showing another example of an echo image displayed by the radar device according to the embodiment of the present invention.

[0118] 13, in the echo image G6, the rain clutter C21, which is displayed in a color different from the land clutter C22 and the target echo C1, is hatched.

[0119] In the radar device 301, the radar section 201 may be configured not to include the determination section 30. In other words, the radar device 301 may be configured not to perform clutter determination processing.

[0120] <Operation flow> The radar device 301 according to the embodiment of the present invention includes a computer including a memory, and a processor such as a CPU in the computer reads out a program including some or all of the steps of the following flowcharts from the memory and executes it. The program of this device can be installed from outside. The program of this device is distributed in a state stored on a recording medium or via a communication line.

[0121] FIG. 14 is a flowchart defining an operation procedure when the radar device according to the embodiment of the present invention performs the suppression process.

[0122] 14, first, the radar device 301 transmits a transmission wave to a detection target area (step S101).

[0123] Next, the radar device 301 receives a reflected signal based on the transmitted wave (step S102).

[0124] Next, the radar device 301 calculates the Doppler velocity width σ of the received reflected signal (step S103).

[0125] Next, the radar device 301 calculates the vector coincidence CPA of the received reflected signal (step S104).

[0126] Next, the radar device 301 calculates a correction value M for the amplitude of the received reflected signal (step S105). Note that steps S103 to S105 may be executed in a reverse order or in parallel.

[0127] Next, the radar device 301 performs a compatibility calculation process for each of the calculated Doppler velocity range σ, vector agreement CPA, and correction value M. For example, as described above, the radar device 301 calculates the compatibility A11, the compatibility A12, and the compatibility A2 corresponding to the Doppler velocity range σ, the vector agreement CPA, and the correction value M, respectively, by using the membership function F for each of the Doppler velocity range σ, the vector agreement CPA, and the correction value M (step S106).

[0128] Next, the radar device 301 calculates a weighted goodness of fit Q using the goodness of fit A11, the goodness of fit A12, and the goodness of fit A2 (step S107).

[0129] Next, the radar device 301 performs a suppression process to suppress clutter using data obtained by normalizing the calculated weighted fitness Q, i.e., the weighted fitness Q. For example, as described above, the radar device 301 calculates a suppression threshold for suppressing clutter using the weighted fitness Q, and subtracts the suppression threshold from the echo data (step S108).

[0130] Next, the radar device 301 displays an echo image in the detection target area on a display device based on the echo data after the suppression process (step S109).

[0131] Next, the radar device 301 performs clutter determination processing based on the calculated weighted conformance Q (step S110).

[0132] Next, the radar device 301 displays the determination result of the clutter determination process on the display device (step S111). Note that the processes of steps S108 and S109 may be executed in a reverse order to the processes of steps S110 and S111, or may be executed in parallel.

[0133] <Modification> In the suppression process, the radar device 301 may replace echo data whose conformance is equal to or greater than a predetermined threshold with zero.

[0134] 1 again, in the modified example, the compatibility calculation unit 28 outputs the compatibility A10 and the compatibility A2 to the clutter suppression unit 29, for example.

[0135] The clutter suppression unit 29 checks whether the compatibility A10 received from the compatibility calculation unit 28 is equal to or greater than a threshold value Th21. The clutter suppression unit 29 also checks whether the compatibility A10 received from the compatibility calculation unit 28 is equal to or greater than a threshold value Th22. The threshold value Th21 is an example of a first threshold value, and the threshold value Th22 is an example of a second threshold value.

[0136] For example, in the suppression process, the clutter suppressor 29 replaces echo data whose conformance A10 is equal to or greater than a threshold value Th21 or whose conformance A2 is equal to or greater than a threshold value Th22 with zero.

[0137] On the other hand, the clutter suppression unit 29 does not replace echo data in which the fitness A10 is less than the threshold Th21 and the fitness A2 is less than the threshold Th22 with zero. Note that the radar device 301 may determine echo data in which the fitness A10 is equal to or greater than the threshold Th21 or the fitness A2 is equal to or greater than the threshold Th22 as echo data containing noise, and replace the echo data with zero, by a process similar to the suppression process in the modified example.

[0138] The above-described embodiments should be considered as illustrative and not restrictive in all respects. The scope of the present invention is defined by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0139] 21 Transmission control section 22 Transmitter 23 Transmitting Antenna 24 Receiving antenna 25 Receiving section 26 A / D conversion section 27 Acquisition Department 28 Compatibility calculation section 29 Clutter suppression section 30 Judgment section 31 Speed ​​width calculation section 32 Vector coincidence calculation unit 33 Threshold calculation unit 41 LPF 42 Correction section 43 Offset Generation Unit 201 Radar Section 202 Display processing unit 301 Radar Equipment F,F1,F2,F3 membership functions G1, G2, G3, G4, G5 echo images

Claims

1. A transmitter that transmits radio waves; an acquisition unit that acquires amplitude information indicating an amplitude of a reflected signal of the radio wave reflected by a target and phase information indicating a phase of the reflected signal; a goodness-of-fit calculation unit that calculates a goodness of fit of clutter included in echo data based on the reflected signal by using a membership function for each of the amplitude information and the phase information, the goodness-of-fit calculation unit calculating a first goodness of fit corresponding to the amplitude information and a second goodness of fit corresponding to the phase information; a clutter suppression unit that performs a suppression process to suppress the clutter based on the first degree of conformance and the second degree of conformance.

2. The radar device further comprises: a determination unit that performs a determination regarding the clutter based on the first degree of conformance and the second degree of conformance; The radar device according to claim 1 , further comprising: a display processing unit that performs processing to display a result of the determination made by the determination unit.

3. The radar device according to claim 1 , wherein the phase information includes a Doppler velocity width of the reflected signal.

4. The radar device according to claim 1 , wherein the phase information includes a vector coincidence of the reflected signal, the vector coincidence being expressed by the following equation (1): [0010] where CPA is the vector coincidence, N is the number of samples, and x i are the complex components of the reflected signal.

5. The acquisition unit performs a filter process to smooth a waveform indicated by the reflected signal, 5. The radar device according to claim 3, wherein the amplitude information includes a correction value for the amplitude of the reflected signal after the filtering process.

6. the compatibility calculation unit further weights the first compatibility and the second compatibility, and adds the weighted first compatibility and the weighted second compatibility; 3. The radar device according to claim 1, wherein the clutter suppression unit performs the suppression process using normalized data obtained by normalizing the addition result obtained by the compatibility calculation unit.

7. the clutter suppression unit performs a threshold calculation process to calculate a threshold for suppressing the clutter based on the normalized data; The radar device according to claim 6 , wherein the clutter suppressor subtracts the threshold value from the echo data in the suppression process.

8. The transmitter transmits the radio waves via a rotating antenna, the clutter suppression unit, in the threshold calculation process, calculates a first threshold, which is the threshold in a rotation direction of the antenna, by using the following formula (2), and calculates a second threshold, which is the threshold in a direction from the radar device toward the target, by using the following formula (3): The radar device according to claim 7 , wherein the clutter suppressor subtracts the second threshold value from the echo data in the suppression process. Tha[i]=Tha[i]×W1×(1-Q) +(S[i]×(1-W1×(1-Q))) ...(2) Thb[i]=Thb[i-1]×W2×(1-Q) +(Tha[i]×(1-W2×(1-Q)))...(3) where Tha[i] is the first threshold, Thb[i] is the second threshold, S[i] is the echo data, W1 and W2 are coefficients, Q is the normalized data, and i is an integer greater than or equal to zero and less than the number of samples.

9. 3. The radar device according to claim 1, wherein the clutter suppression unit replaces the echo data for which the first conformance is equal to or greater than a predetermined first threshold or the second conformance is equal to or greater than a predetermined second threshold with zero in the suppression process.

10. A clutter suppression method for a radar device, comprising: Transmits radio waves, acquiring amplitude information indicating an amplitude of a reflected signal of the radio wave reflected by a target and phase information indicating a phase of the reflected signal; calculating a first goodness of fit corresponding to the amplitude information and a second goodness of fit corresponding to the phase information as goodness of fit of the clutter included in the echo data based on the reflected signal by using a membership function for each of the amplitude information and the phase information; a clutter suppression method for performing a suppression process for suppressing the clutter based on the first degree of fit and the second degree of fit.

11. A clutter suppression program for use in a radar device, comprising: A process of transmitting radio waves; A process of acquiring amplitude information indicating an amplitude of a reflected signal of the radio wave reflected by a target and phase information indicating a phase of the reflected signal; a process of calculating a first goodness of fit corresponding to the amplitude information and a second goodness of fit corresponding to the phase information as goodness of fit of clutter included in echo data based on the reflected signal by using a membership function for each of the amplitude information and the phase information; and suppressing the clutter based on the first degree of conformance and the second degree of conformance.

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