Signal processor and radar device

Abstract

To provide a signal processor that can improve the detection performance of a target existing within a clutter region while reducing an erroneous alarm by clutter components.SOLUTION: A signal processor 30 is provided in a radar device 100 which acquires a reception signal including reflected waves from a target being a detection object and detects the target by executing signal processing on the reception signal. The signal processor 30 includes: a range-velocity signal generation unit 31 which generates a range-velocity signal containing information on a distance and velocity from the reception signal; and a target detection unit 32 which sets an evaluation region for the detection object on the basis of the signal intensity of the range-velocity signal and performs target detection on the basis of a detection threshold obtained by setting the evaluation region.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a signal processor that detects targets and a radar device that includes the signal processor. [Background technology]

[0002] A radar device receives reflected waves from a target to be detected, and detects the target by performing signal processing on the received signal of the reflected waves. A target detection threshold is used to detect the target. Conventional radar devices calculate a target detection threshold based on the signal strength of the detection target cell in the received signal of the reflected waves and the signal strength around the detection target cell. If the only signal components present in the detection target cell of the target and its surroundings are the target and noise, a target detection threshold that results in a preset false alarm probability can be calculated, and target detection at that false alarm probability becomes possible. On the other hand, if clutter components are present in the detection target cell of the target and its surroundings, the clutter is detected as a target, resulting in a problem of increased false alarms.

[0003] Against this technical background, the following Patent Document 1 discloses a detection device that suppresses false alarms caused by clutter. The detection device disclosed in Patent Document 1 includes a mask calculation unit that calculates a clutter area, and aims to suppress false alarms by excluding the clutter area calculated by the mask calculation unit during detection from the detection target. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] U.S. Pat. No. 1,083,0883 Summary of the Invention [Problem to be solved by the invention]

[0005] The detection device disclosed in Patent Document 1 had difficulty detecting a target when the target was present within a clutter area, i.e., when the target was present in an area where the clutter and the target could not be separated in terms of distance or speed.

[0006] The present disclosure has been made in consideration of the above, and aims to provide a signal processor that can improve detection performance for targets present in a clutter area while reducing false alarms due to clutter components. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems and achieve the object, a signal processor according to the present disclosure is provided in a radar device that acquires a received signal including a reflected wave from a target to be detected and detects the target by performing signal processing on the received signal. The signal processor includes a signal generating unit that generates a distance / speed signal including distance and speed information from the received signal, and a target detecting unit that sets an evaluation region of the detection target based on the signal strength of the distance / speed signal and detects the target based on a detection threshold obtained by setting the evaluation region. Effect of the Invention

[0008] The signal processor according to the present disclosure advantageously reduces false alarms due to clutter components while improving the detection performance of targets present within a clutter area. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a block diagram showing a configuration example of a radar device including a signal processor according to a first embodiment; [Diagram 2] FIG. 1 is a block diagram showing an example of a hardware configuration for implementing the functions of a signal processor according to a first embodiment; [Diagram 3] FIG. 11 is a block diagram showing another example of a hardware configuration for implementing the functions of the signal processor according to the first embodiment. [Figure 4] 1 is a flowchart showing an overall operation of a radar device according to a first embodiment. [Diagram 5] 5 is a flowchart showing a detailed process of the first step in FIG. 4. [Figure 6] 5 is a flowchart showing a detailed process of the second step in FIG. 4. [Figure 7] A flowchart showing a detailed process of the third step in FIG. [Figure 8] FIG. 1 is a diagram for explaining a distance / speed signal in the first embodiment; [Figure 9] FIG. 2 is a diagram for explaining the positional relationship between the radar device according to the first embodiment and a reflecting surface of a radar signal; [Figure 10] FIG. 1 is a conceptual diagram for explaining a detection processing method according to a first embodiment; [Figure 11] FIG. 1 is a conceptual diagram for explaining a conventional detection processing method shown as a comparative example. [Figure 12] FIG. 1 is a diagram for explaining the effect of reducing false alarms by the detection processing method according to the first embodiment; [Figure 13] FIG. 11 is a block diagram showing a configuration example of a radar device including a signal processor according to a second embodiment. [Figure 14] FIG. 13 is a diagram for explaining a process performed by a clutter region classification unit according to the second embodiment; [Figure 15] FIG. 13 is a diagram for explaining processing by a linearization processing unit according to the second embodiment; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] A signal processor and a radar device according to embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings.

[0011] Embodiment 1 Fig. 1 is a block diagram showing an example of a configuration of a radar device 100 including a signal processor 30 according to the first embodiment. Fig. 2 is a block diagram showing an example of a hardware configuration for realizing the functions of the signal processor 30 according to the first embodiment.

[0012] The radar device 100 detects a target by acquiring a received signal including a reflected wave from the target to be detected and performing signal processing on the received signal. To realize this function, the radar device 100 according to the first embodiment includes an antenna unit 1, a transmitter unit 10, a receiver unit 20, and a signal processor 30, as shown in FIG. 1. The radar device 100 is connected to a display unit 50. The display unit 50 displays the target detection result output from the radar device 100 on a display unit (not shown). The target detection result includes information such as the distance to the target, the relative speed of the target, and the direction of the target. In this paper, these three pieces of information may be referred to as the "target distance," the "target speed," and the "target direction."

[0013] Furthermore, when the radar device 100 is mounted on a moving object, to obtain the target distance, target speed, and target direction, information on the position and speed of the platform on which the radar device 100 is mounted, and information on the direction of the main lobe of the transmission wave radiated from the radar device 100 are required. In this document, among these pieces of information, the position information and speed information of the platform are sometimes referred to as the "radar position" and "radar speed", respectively.

[0014] The antenna unit 1 includes a transmit / receive antenna 2 and a transmit / receive switch unit 3. The transmitter unit 10 includes a signal generator 11 and a transmitter 12. The signal generator 11 generates a transmission signal and outputs the generated transmission signal to the transmitter 12 and a receiver 22 (described later). When the transmitter 12 receives the transmission signal from the signal generator 11, it generates a radar signal in the RF (Radio Frequency) band based on the transmission signal. The generated radar signal is sent to the transmit / receive antenna 2 via the transmit / receive switch unit 3. The transmit / receive antenna 2 radiates the radar signal output from the transmitter 12 into space. A part of the radar signal radiated into space is reflected by the target to be detected.

[0015] The receiving unit 20 includes a receiver 22 and an AD (Analog-to-Digital) converter 23. The receiver 22 receives a time series signal of a reflected wave from a target via the transmission / reception switching unit 3. The receiver 22 generates a time series received signal by down-converting the frequency of the time series signal of the received reflected wave. The transmission signal output from the signal generating unit 11 is used to generate the down-converted received signal. The receiver 22 outputs the time series received signal to the AD converter 23.

[0016] The time-series received signal output from the receiver 22 is an analog signal, and the AD converter 23 converts the time-series received signal into a received video signal, which is a digital signal, and outputs it to the signal processor 30 .

[0017] FIG. 1 shows a configuration in which the transmitting unit 10 is provided in the radar device 100, but the present invention is not limited thereto. The transmitting unit 10 may be provided in a device different from the radar device 100 shown in FIG. 1. In addition, in FIG. 1, the antenna unit 1 includes a transmitting and receiving antenna 2 for both transmitting and receiving, but the transmitting antenna and the receiving antenna may be provided separately. In addition, each of the transmitting antenna and the receiving antenna may be an array antenna formed of a plurality of antenna elements or antenna devices. In addition, the radar signal radiated into space from the transmitting and receiving antenna 2 may be a continuous wave, a pulse wave, or a modulated wave. In addition, the transmitting unit 10 and the receiving unit 20 may each use any transmission method. For example, the MIMO (Multiple Input Multiple Output) method may be used as each transmission method.

[0018] The signal processor 30 includes a distance and speed signal generator 31 and a target detector 32. The distance and speed signal generator 31 acquires a received video signal output from the receiver 20, and generates a distance and speed signal based on the received video signal. The distance and speed signal means a signal based on distance and speed, and is generated as a signal for calculating a target distance and target speed. The target detector 32 detects target information such as a target distance, a target speed, and a target direction by performing signal processing on the distance and speed signal. The detailed processing contents of the distance and speed signal generator 31 and the target detector 32 will be described later.

[0019] In this paper, it is assumed that each of the components of the signal processor 30, that is, the distance / speed signal generator 31 and the target detector 32 shown in Fig. 1, is realized by dedicated hardware as shown in Fig. 2. That is, it is assumed that the signal processor 30 is realized by a distance / speed signal generator circuit 41 and a target detector circuit 42.

[0020] Each of the distance / speed signal generating circuit 41 and the target detection circuit 42 may be, for example, a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC (Application Specific Integrated Circuit), an FPGA (Field-Programmable Gate Array), or a combination of these.

[0021] FIG. 3 is a block diagram showing another example of a hardware configuration for realizing the function of the signal processor 30 according to the first embodiment. The components of the signal processor 30 are not limited to those realized by dedicated hardware, and the signal processor 30 may be realized by software, firmware, or a combination of software and firmware. FIG. 3 shows a configuration of a computer including a memory 51 and a processor 52. The software or firmware is stored in the computer's memory 51 as a program. The computer's processor 52 executes processing steps according to the program stored in the memory 51 to execute processing related to target detection, which will be described later. The processor 52 corresponds to a processing means called a CPU (Central Processing Unit), a central processing unit, a processing unit, an arithmetic unit, a microprocessor, a microcomputer, or a DSP (Digital Signal Processor), etc.

[0022] 2 shows an example in which each of the components of the signal processor 30 is realized by dedicated hardware, and FIG. 3 shows an example in which the signal processor 30 is realized by software, firmware, or the like, but is not limited to these examples. Some of the components in the signal processor 30 may be realized by dedicated hardware, and the remaining components may be realized by software, firmware, or the like.

[0023] 4 is a flowchart showing the overall operation of the radar device 100 according to the first embodiment. The transmitter 10 and the antenna unit 1 radiate a radar signal into space (step ST1: first step). The receiver 20 outputs a received video signal to the signal processor 30 (step ST2: second step). The signal processor 30 detects target candidates and calculates target information (step ST3: third step).

[0024] Fig. 5 is a flowchart showing a detailed processing procedure of the first step (step ST1) in Fig. 4. The signal generating unit 11 generates a transmission signal (step ST11). As described above, the generated transmission signal is output to the transmitter 12 and the receiver 22. The transmitter 12 generates a radar signal (step ST12). The generated radar signal is output to the transmitting and receiving antenna 2. The transmitting and receiving antenna 2 radiates the radar signal into space (step ST13). As described above, the radar signal radiated in step ST13 does not have to be a radar signal radiated from the radar device 100 itself, and may be a radar signal radiated from another radar device.

[0025] 6 is a flowchart showing a detailed processing procedure of the second step (step ST2) in FIG. 4. The radar signal emitted into space is reflected by a target and becomes a reflected signal. The reflected signal is incident on the transmitting / receiving antenna 2 in the antenna unit 1. The transmitting / receiving antenna 2 receives the incident reflected signal and outputs it to the receiver 22 (step ST21). The receiver 22 down-converts the input reflected signal to generate a time-series received signal (step ST22). The generated time-series received signal is output to the AD converter 23. The AD converter 23 converts the time-series received signal, which is an analog signal, into a digital signal to generate a received video signal (step ST23). The generated received video signal is output to the signal processor 30.

[0026] Fig. 7 is a flowchart showing a detailed processing procedure of the third step (step ST3) in Fig. 4. In the following explanation, the radar signal is a pulse signal, and modulation is performed within the pulse.

[0027] The distance and velocity signal generator 31 performs pulse compression on the received video signal while performing coherent integration in the hit direction to generate a distance and velocity signal (step ST31). The pulse compression is a correlation calculation performed based on the modulation component. The target detector 32 uses the distance and velocity signal to detect target candidates based on information on clutter, and calculates the distance and velocity of the target candidates (step ST32).

[0028] The processing of steps ST31 and ST32 will be further described with reference to Fig. 8 and Fig. 9 and some formulas. Fig. 8 is a diagram for explaining the distance / velocity signal in the first embodiment. Fig. 9 is a diagram for explaining the positional relationship between the radar device 100 according to the first embodiment and a reflecting surface of the radar signal.

[0029] First, the received video signal is represented as V(m,n), where m is the sample number and n is the hit number. As described above, the distance / velocity signal generator 31 performs pulse compression on the received video signal V(m,n). For convenience, the signal generated at this time is called the "distance / hit signal" and V R It is expressed as (m,n).

[0030] The distance / speed signal generator 31 generates a distance hit signal V R For (m, n), coherent integration in the hit direction is performed according to the following equation (1) to obtain the range velocity signal f d (m,n fft ) is generated. fft is the distance velocity signal f d (m,n fft ) is the sample number in the velocity direction. Here, the coherent integration in the hit direction may be performed by discrete Fourier transform, fast Fourier transform, or chirp z transform. Hereinafter, the number of samples in the velocity direction is called N fft This is explained as follows.

[0031]

number

[0032] In Fig. 8, the distance-speed signal f d (m,n fft) is shown in three dimensions, with the x-axis representing speed, the y-axis representing distance, and the z-axis representing power. Specifically, FIG. 8 shows an example in which there are clutters with high power, a target observed at the same distance and speed as the clutter, and a target observed separated from the clutter by distance or speed. The clutters with high power shown in FIG. 8 are reflected signals that affect the detection performance of the target and that lead to false alarms of the target. In the radar device 100, clutters with high power are often observed in the direction of the main beam, and are particularly observed when the sea surface, ground, structures, objects with an area larger than that of the target, etc. are present in the direction of the main beam.

[0033] The distance hit signal V generated by the distance speed signal generator 31 R (m, n) is output to the target detection unit 32.

[0034] The target detection unit 32 calculates the velocity v'(m,v,H) in the clutter direction corresponding to the sample number m according to the following equation (2).

[0035]

number

[0036] In equation (2), v is the radar speed, H is the altitude of the radar device 100 relative to the assumed reflecting surface, and θ m is the angle between the radar device 100 and the assumed clutter, R m is the distance between the radar device 100 and the assumed clutter, Δt is the sampling interval, and M is the number of test cells. The test cells are cells to be judged for the presence or absence of a target. The cells are divided into preset distance widths and speed widths, and are divided into preset distance widths and speed widths, and are divided into preset distance widths and speed widths, and are divided into preset distance widths and speed widths. d (m,n fft ) is a section on the map that represents

[0037] The radar speed v, altitude H, and angle θ shown in equation (2) m , distance R mThe meaning of the velocity v'(m,v,H) is as shown in FIG.

[0038] The target detection unit 32 detects the number of guard cells M G , number of sample cells M S Using the above, the target candidate D(m,n fft ) is calculated. The sample cell is set as an evaluation region for determining whether or not a target exists in the test cell m to be detected. The guard cell is set adjacent to the test cell m to prevent a cell containing the target power from being set as the evaluation region.

[0039]

number

[0040] In equation (3), P(m,n fft ) is the distance and speed signal f d (m,n fft ) and P TH (m,n fft ) represents the detection threshold. The distance and velocity signal f d (m,n fft ) power P(m,n fft ) is a physical quantity representing the signal strength in test cell m.

[0041] distance speed signal f d (m,n fft ) power P(m,n fft ) is the detection threshold P TH (m,n fft ), it is determined to be a target candidate and D(m,n fft ) = 1. Meanwhile, the distance and speed signal f d (m,n fft ) power P(m,n fft ) is the detection threshold P TH (m,n fft ), it is determined that it is not a target candidate and D(m,n fft )=0.

[0042] In addition, the detection threshold P TH (m,n fft ) is calculated according to the following formula (4):

[0043]

number

[0044] In equation (4), K TH represents the threshold coefficient, and mean(x) represents the mean of array x. S ''(m,m S ) is the test cell m, the sample cell m S In addition, n S ''(m,m S ) is the test cell m, the sample cell m S is the number of speed cells extracted when

[0045] In addition, the threshold coefficient K TH is calculated according to the following formula (5):

[0046]

number

[0047] Threshold coefficient K TH is a threshold coefficient that keeps the false alarm probability constant and is set according to the characteristics and distribution in the sample cell and the number of sample cells. In equation (5), K calc (N clt ) represents the function for calculating the coefficients assuming a clutter distribution, and N clt is a number that assumes clutter distribution. Note that the threshold coefficient K TH A predetermined value may be used.

[0048] The target detection unit 32 detects the position of the test cell m and the position of the sample cell m according to the following formula (6). S Sample number m in the case S ''(m,m S) is calculated.

[0049]

number

[0050] In equation (6), Round(x) represents the value of variable X rounded off to the nearest whole number, and ΔR represents the sampling interval in the distance direction.

[0051] In addition, the target detection unit 32 detects the test cell m and the sample cell m according to the following formula (7). S Number of speed cells extracted in the case of n S ''(m,m S ) is calculated.

[0052]

number

[0053] In equation (7), Δv represents the sampling interval in the velocity direction.

[0054] The target detection unit 32 also calculates the speed sample number n corresponding to the test cell m according to the following equation (8): fft,max Calculate (m).

[0055]

number

[0056] In equation (8), argmax nfft P(m,n fft )(*Note: “argmax nfft "of" nfft " is attached under "argmax") is the power P(m,n fft ) is the maximum value of n fft The target detection unit 32 calculates the distance and velocity signal f at the sample number m of each distance according to the formula (8). d (m,n fft ) power P(m,n fft) indicates the speed sample number n fft,max Calculate (m).

[0057] In addition, the target detection unit 32 calculates the velocity sample number n' according to the following equation (9). fft,max (m) may be calculated.

[0058]

number

[0059] In equation (9), N LSM is the order of the least squares method, and n LSM is the order number of the least squares method, and χn LSM (*Note:“n LSM " is the subscript to the right of "χ") is the least squares coefficient.

[0060] The distance and velocity signal f at each distance sample number m d (m,n fft ) power P(m,n fft ) indicates the speed sample number n fft,max By approximating (m) using the least squares method, it is possible to obtain the effect of suppressing false alarms. A more detailed calculation procedure will be explained below.

[0061] The target detection unit 32 calculates the distance and velocity signal f at the sample number m of each distance according to the following equation (10). d (m,n fft ) power P(m,n fft ) indicates the speed sample number n' fft,max The coefficients of the least squares method for calculating (m) are calculated. Moreover, the following formula (11) is an example in which the degree of the least squares method is 2, that is, the function used in the least squares method is a quadratic function.

[0062]

number

number

[0063] In equations (10) and (11), X represents the array of coefficients of the least squares method, W represents the array of the sample number m of each distance raised to a power, and Y represents the distance velocity signal f d (m,n fft ) power P(m,n fft ) indicates the speed sample number n fft,max (m)

[0064] In addition, the target detection unit 32 detects the test cell m and the sample cell m according to the following formula (12). S Number of speed cells extracted in the case of n S ''(m,m S ) is calculated.

[0065]

number

[0066] As described above, in the radar device 100 according to the first embodiment, the test cell m and the sample cell m S Number of speed cells extracted in the case of n S ''(m,m S ) is calculated using the distance and velocity signal f d (m,n fft ) power P(m,n fft This enables the target detection unit 32 to detect target candidates even when information such as the radar position and radar speed cannot be obtained in advance.

[0067] Next, the effect of reducing false alarms by the detection processing method of the present application will be described in comparison with conventional detection processing methods. Fig. 10 is a conceptual diagram for explaining the detection processing method of the first embodiment. Fig. 11 is a conceptual diagram for explaining the conventional detection processing method shown as a comparative example. Fig. 12 is a diagram for explaining the effect of reducing false alarms by the detection processing method of the first embodiment.

[0068] On the left side of Fig. 10 and Fig. 11, the distance velocity signal f d (m,nfft ) is shown as a distance-velocity-signal map, which is a signal strength distribution of the target. Figures 10 and 11 show the same signal strength distribution, with the magnitude of the power being represented by the shade of the hatching pattern. Also, the right side of Figures 10 and 11 shows the results of the target detection process.

[0069] In conventional detection processing, guard cells (marked with x) and sample cells (marked with △) are set one-dimensionally along the distance direction, as shown in Fig. 11. On the other hand, in the detection processing of the present application, guard cells and sample cells are set two-dimensionally along clutter with high signal strength, as shown in Fig. 10. The clutter with high signal strength is assumed to be main lobe clutter generated by the main lobe of the radar device 100. The numbers of guard cells and sample cells are the same in Fig. 10 and Fig. 11. Specifically, in the examples of Fig. 10 and Fig. 11, the number of guard cells is set to 4 and the number of sample cells is set to 6.

[0070] In the example of Fig. 11, the sample cell that is compared with the power of the test cell (circle) contains only noise, so the threshold coefficient is calculated to detect clutter with high power as a target candidate, and the number of false alarms increases, as shown in the right diagram of Fig. 11.

[0071] The reason for the increase in false alarms is shown in Fig. 12(a) and (b). When only noise is present in the sample cell, a threshold value according to the noise distribution is set as shown in Fig. 12(a). When such a threshold value is set, if noise and clutter with high power are present in the sample cell, the sample cell is more likely to be determined as a target candidate by the threshold value, and false alarms due to the clutter occur frequently. Fig. 11 shows the case where guard cells and sample cells are set one-dimensionally along the distance direction, but the same problem occurs when guard cells and sample cells are set one-dimensionally along the velocity direction.

[0072] In contrast, in the detection process of the present invention, the target detection unit 32 calculates the detection threshold value P TH (m,n fft) is set. This makes it possible to detect a target while reducing false alarms caused by clutter, even when the target is present in clutter with high power. In the detection process of the present application, the target detection unit 32 calculates the sample cell according to equations (6) and (7), and sets the detection threshold P TH (m,n fft ) is set. This makes it possible to avoid detecting clutter with high power as a target candidate, and reduces false alarms caused by clutter with high power.

[0073] In the first embodiment, the target candidate determination process has been described using CA-CFAR (Cell Average Constant False Alarm Rate) processing. The gist of the process in the first embodiment is that reflected waves due to clutter with high power are present in all or many of the sample cells. In other words, cells in which reflected waves due to clutter with high power are present may be set as sample cells. Therefore, for the target candidate determination process, other CFAR processes such as GO-CFAR (Greatest Of CFAR) and SO-CFAR (Smallest Of CFAR) may be used instead of CA-CFAR processing.

[0074] As described above, the signal processor according to the first embodiment includes a signal generator that generates a distance / speed signal including distance and speed information from a received signal, and a target detector that sets an evaluation region of a detection target based on the signal strength of the distance / speed signal and detects a target based on a detection threshold obtained by setting the evaluation region. At this time, since clutter with high power is present in the evaluation region of the detection target, a detection threshold corresponding to the clutter distribution with high power is set. This makes it possible to improve the detection performance of a target present in a clutter region while reducing false alarms due to clutter components.

[0075] In the signal processor according to the first embodiment, the detection threshold may be set based on the position information, speed information, and main lobe direction information of the radar device, or based on the average or maximum value of the signal strength of the distance / velocity signal in the evaluation region. The evaluation region of the detection target may be set along the direction in which the main lobe clutter exists, or based on parameters obtained by processing the signal strength of the distance / velocity signal by the least squares method. Whichever method is used, it is possible to enjoy the effects described in the first embodiment.

[0076] Embodiment 2 FIG. 13 is a block diagram showing a configuration example of a radar device 100b including a signal processor 30b according to the second embodiment. In the radar device 100b according to the second embodiment, the transmitter 10 shown in FIG. 1 is replaced with a transmitter 10b, and the signal processor 30 shown in FIG. 1 is replaced with a signal processor 30b. In the transmitter 10b shown in FIG. 13, the signal generator 11 shown in FIG. 1 is replaced with a signal generator 11b, and in the signal processor 30b shown in FIG. 13, the distance / velocity signal generator 31 shown in FIG. 1 is replaced with a distance / velocity signal generator 31b, and the target detector 32 shown in FIG. 1 is replaced with a target detector 32b. In addition, in the signal processor 30b shown in FIG. 13, a clutter region classification unit 33 and a linearization processor 34 are added between the distance / velocity signal generator 31b and the target detector 32b. The other components are the same or equivalent to those of the radar device 100 shown in FIG. 1, and the same or equivalent components are denoted by the same reference numerals, and duplicated explanations will be omitted.

[0077] The signal generating unit 11b generates a transmission signal and outputs the generated transmission signal to each of the transmitter 12 and the receiver 22. The difference from the signal generating unit 11 in the first embodiment is that the transmission signal generated by the signal generating unit 11b in the second embodiment, i.e., the transmission signal that is the source of the radar signal, is code modulated. By code modulation, a code for identifying the timing of transmission is added to the transmission signal. This allows the distance / speed signal generating unit 31b of the signal processor 30b to code demodulate with the code corresponding to the distance, and to suppress reflected signals other than the code corresponding to the distance.

[0078] The clutter region classification unit 33 calculates the clutter region value P clt (m,n fft ) is calculated.

[0079]

number

[0080] In formula (13), L TH is the distance and speed signal f d (m,n fft ) power P(m,n fft ) is the threshold for calculating the clutter area of ​​the range and velocity signal f d (m,n fft ) power P(m,n fft ) is the threshold L TH If it is greater than or equal to this, it is determined to be a clutter area and P clt (m,n fft ) = 1. Meanwhile, the distance and speed signal f d (m,n fft ) power P(m,n fft ) is the threshold L TH If it is less than P, it is determined to be outside the clutter area (noise area) and clt (m,n fft )=0. That is, the threshold L TH It is determined whether the area that returned the reflected signal is a clutter area or outside the clutter area (noise area) by the above.

[0081] 14 is a diagram illustrating the process performed by the clutter region classification unit 33 according to the second embodiment. In FIG. 14, the hatched region indicates the clutter region value P clt (m,n fft )=1, and the non-hatched areas are areas where the clutter area value P clt (m,n fft)=0. The clutter region classification unit 33 according to the second embodiment classifies the region from which the reflected signal is obtained into a clutter region and a non-clutter region (noise region), so that the linearization processing unit 34 and the target detection unit 32b at the subsequent stage can perform processing according to each region.

[0082] The clutter region classification unit 33 determines a threshold value L according to the following equation (14). TH Calculate.

[0083]

number

[0084] In equation (14), σ 2 var (k) represents the variance for distinguishing between clutter areas with high signal strength and other areas. k is a number that represents the degree of signal strength, and will be referred to as "strength k" hereafter. TH has variance σ 2 var The value of intensity k indicating the maximum value of (k) is set. Note that in formula (14), intensity k is divided into L divisions from 1 to L, but the number of divisions is arbitrary.

[0085] Variance σ at intensity k 2 var (k) is calculated according to the following equation (15):

[0086]

number

[0087] In equation (15), ω p (k) represents the number of samples at region number p and intensity k, and μ p (k) represents the weighted average at region number p and intensity k, and μ T represents the weighted sum.

[0088] Number of samples ω at region number p and intensity k p(k) is calculated according to the following equation (16):

[0089]

number

[0090] In equation (16), P hist (l) is the distance and speed signal f d (m,n fft ) power P(m,n fft ) where p=0 means outside the clutter region (noise region) and p=1 means inside the clutter region.

[0091] The clutter region classification unit 33 also calculates the distance and velocity signal f according to the following equation (17): d (m,n fft ) power P(m,n fft ) Histogram P' before normalization hist Calculate (l).

[0092]

number

[0093] The histogram P shown in equation (16) hist (l) is the histogram P' before normalization calculated by equation (17). hist (l) is used to calculate according to the following equation (18).

[0094]

number

[0095] In addition, the weighted average μ p (k) is calculated according to the following equation (19):

[0096]

number

[0097] In addition, the weighting factor μ T is calculated according to the following equation (20).

[0098]

number

[0099] In addition, the threshold L TH However, the clutter region classification unit 33 according to the second embodiment uses the threshold value L TH The distance speed signal f d (m,n fft ) power P(m,n fft ), it has the advantage that it does not need to be determined in advance, and the threshold value L is calculated based on the observed received signal. TH This has the advantage that it can be calculated with high accuracy.

[0100] The clutter area classification unit 33 classifies the calculated clutter area value P clt (m,n fft ) to the linearization processor 34.

[0101] The linearization processor 34 calculates the distance velocity signal f according to the following equation (21): d (m,n fft ) power P(m,n fft ) is linearized, and the linearized power P'(m,n fft )

[0102]

number

[0103] Fig. 15 is a diagram for explaining the processing by the linearization processing unit 34 according to the embodiment 2. Fig. 15(a) shows the distance-speed signal map before the linearization processing, and Fig. 15(b) shows the distance-speed signal map after the linearization processing.

[0104] In the distance-speed signal map before linearization, the relationship of continuity between the test cells and the sample cells is small. The target detection unit 32 processes a large amount of test cell data and sample cell data for target candidate determination processing and target detection processing. In the relationship between the test cells and the sample cells before linearization, the continuity of the memory arrangement is poor, which may result in an increase in memory capacity and an increase in processing time.

[0105] In contrast, in the distance-speed signal map after linearization, the relationship of continuity between the test cell and the sample cell is high. Therefore, by using the distance-speed signal map after linearization, the continuity of the memory arrangement can be increased, so that the storage capacity can be reduced and the processing time can be shortened.

[0106] The linearization processing unit 34 calculates the power P'(m,n fft ) to the target detection unit 32b.

[0107] The target detection unit 32b calculates the detection threshold P TH (m,n fft ) is calculated.

[0108]

number

[0109] In equation (22), K TH,Noise represents a threshold coefficient when noise distribution is assumed.

[0110] As shown in equation (22), the target detection unit 32b detects the clutter region using a detection threshold P TH (m,n fft ) is used to detect targets, and for areas outside the clutter area (noise area), a threshold coefficient K TH,Noise The detection threshold P TH (m,n fft ) is used.

[0111] As shown in Fig. 15(b), even after linearization, there are cases where all sample cells are not arranged continuously. Even in such cases, sample cells may be set along the distance direction or the velocity direction in target detection processing outside the clutter region (noise region).

[0112] Threshold coefficient K when noise distribution is assumed TH,Noise is calculated according to the following equation (23).

[0113]

number

[0114] Threshold coefficient K TH,Noise is a threshold coefficient for making the false alarm probability constant, which is set according to the characteristics and distribution of noise in the sample cell and the number of sample cells. In equation (23), N Noise is the number that assumes the noise distribution, and K calc (N Noise ) represents a function for calculating coefficients assuming a noise distribution.

[0115] As described above, the signal processor according to the second embodiment further includes a clutter area classification unit as an area classification unit that classifies the area of ​​the detection target based on the signal strength of the range-velocity signal in addition to the configuration of the first embodiment. According to the signal processor configured in this manner, the target detection unit can perform the target detection process using a threshold value according to the area classified by the clutter area classification unit. When the area classification unit classifies the area of ​​the detection target into a clutter area and an outside clutter area, the target detection unit can use a threshold value calculated from the respective distributions of the clutter area and the outside clutter area (noise area). This makes it possible to make the false alarms constant in accordance with the respective distributions, and further makes it possible to improve the detection performance of targets present in the clutter area while reducing false alarms due to clutter components.

[0116] Moreover, the signal processor according to the second embodiment includes, in addition to the configuration of the first embodiment, a linearization processing unit that performs linearization processing on the distance / speed signal to generate a linearized distance / speed signal map. By using the linearized distance / speed signal map, the continuity of the memory arrangement can be increased, so that the storage capacity of the radar device can be reduced and the processing time in the radar device can be shortened.

[0117] In the signal processor according to the second embodiment, the evaluation region of the detection target may be set in the distance direction and the speed direction with the cell of the detection target at the center. Even if set in this way, it is possible to obtain the effects described in the second embodiment.

[0118] In addition, in the signal processor according to the second embodiment, the transmission signal that is the source of the radar signal may be code-modulated, and the distance / velocity signal may be code-demodulated with a code corresponding to the distance. In this way, a distance / velocity signal is generated in which components of the reflected signal other than the code corresponding to the distance are suppressed, making it possible to further reduce false alarms due to clutter.

[0119] The configurations shown in the above embodiments are merely examples, and may be combined with other known technologies, or the embodiments may be combined with each other. Also, parts of the configurations may be omitted or modified without departing from the spirit of the invention. [Explanation of symbols]

[0120] REFERENCE SIGNS LIST 1 antenna section, 2 transmit / receive antenna, 3 transmit / receive switching section, 10, 10b transmit section, 11, 11b signal generating section, 12 transmitter, 20 receive section, 22 receiver, 23 AD converter, 30, 30b signal processor, 31, 31b distance / velocity signal generating section, 32, 32b target detection section, 33 clutter area classification section, 34 linearization processing section, 41 distance / velocity signal generating circuit, 42 target detection circuit, 50 display, 51 memory, 52 processor, 100, 100b radar device.

Claims

1. A signal processor provided in a radar device that acquires a received signal including a reflected wave from a target to be detected and detects the target by performing signal processing on the received signal, a signal generating unit that generates a distance and speed signal including distance and speed information from the received signal; a target detection unit that sets an evaluation region of a detection target based on a signal strength of the distance / velocity signal, and detects a target based on a detection threshold obtained by setting the evaluation region; A signal processor comprising:

2. The detection threshold is set based on the position information, the speed information, and the main lobe direction information of the radar device.

2. The signal processor according to claim 1 .

3. The evaluation region is set along the direction in which the main lobe clutter exists.

3. The signal processor according to claim 2.

4. The detection threshold is set based on an average value of the signal strength of the distance velocity signal in the evaluation region.

2. The signal processor according to claim 1 .

5. The detection threshold is set based on a maximum value of the signal strength of the distance velocity signal in the evaluation region.

2. The signal processor according to claim 1 .

6. The evaluation region is set based on parameters obtained by processing the signal strength of the distance velocity signal by the least squares method.

2. The signal processor according to claim 1 .

7. a region classification unit that classifies a detection target region based on a signal strength of the distance / velocity signal; The target detection unit performs a target detection process using a threshold value according to the area classified by the area classification unit.

2. The signal processor according to claim 1 .

8. The area classification unit classifies an area of ​​a detection target into a clutter area and a non-clutter area, The target detection unit performs a target detection process using different thresholds for the clutter region and outside the clutter region.

8. The signal processor according to claim 7.

9. A linearization processing unit performs a linearization process on the range velocity signal to generate a linearized range velocity signal map, The target detection unit performs a target detection process using the distance / speed signal map.

8. The signal processor according to claim 7.

10. The target detection unit performs a target detection process by setting the evaluation region in the distance direction and the speed direction with the cell to be detected as the center.

8. The signal processor according to claim 7.

11. The transmission signal that is the source of the radar signal is code-modulated, and the distance / velocity signal is code-demodulated with a code corresponding to the distance.

2. The signal processor according to claim 1 .

12. A radar device comprising the signal processor according to any one of claims 1 to 11.

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