JP2014106133A - Target detection device, and target detection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To maintain a target detection probability in a low-SNR environment even when using a TBD algorithm.SOLUTION: A target detection device includes: an analysis processor 15 which uses a TBD algorithm to convert a reception detection signal of a radar reflection wave to cell reception signals per resolution unit of distance and frequency of an observation area and analyzes the distance, frequency, and speed of each cell: a correlation processor 16 which uses a particle filter to determine a target estimation point of a target distance and a target speed at the current time in accordance with the cell reception signals and the analysis processing result at the preceding observation and determines whether the target estimation point is in a transmission blanking period or not; and a detection processor 17 which obtains a wake of a target on the basis of the analysis result of the analysis processor 15 and the transmission blanking period determination result about the target estimation point, of the correlation processor 16.

Description

  The present embodiment relates to a target detection apparatus and a target detection method for obtaining a target distance and direction using a radar device in a flying object.

  The target detection device using the radar device mounted on the flying object has a simple structure from the viewpoint of miniaturization, and the received signal of the radar reflected wave is Fourier-transformed so that it exceeds the preset threshold value. Judge the goal.

  As is well known, in a radar apparatus, in a low SNR (Signal to Noise Ratio) environment, it is necessary to increase the threshold value in order to avoid false detection, and the target component is the threshold value. If it does not exceed, the target cannot be detected. When the threshold value is lowered, false detections other than the target increase. If the target is a slow-moving target in the ground radar apparatus, the SNR can be improved by extending the observation time. However, the effect of the flying object cannot be obtained because a rapid distance change from the target occurs.

  As means for solving this problem, a method has been devised in which observation is repeated a plurality of times and a change in distance or speed is dealt with using a TBD (Track Before Detect) algorithm. With these methods, the target can be detected with almost the same hardware scale as that of a conventional flying object.

  In a radar apparatus mounted on a flying object, a high PRF (Pulse Repetition Frequency) having a wide speed detection range may be employed. In a high PRIF, a transmission pulse is transmitted at a short interval (PRI: Pulse Repetition Interval) with respect to a target distance. Therefore, in a certain PRI, a reflected wave from the target is returned at the transmission timing, and a period during which reception is not possible ( Transmission blanking period) occurs. Therefore, the PRI is switched according to the target relative distance so that the transmission timing and the reception timing of the reflected wave do not overlap.

  However, in the minute target detection using the TBD algorithm, since the detailed position of the target is not known at the time of observation, the PRI cannot be switched, and a period in which a reflected wave from the target cannot be obtained. Therefore, the target detection operation during that time becomes unstable, and as a result, noise is erroneously detected, or even if the reflected wave can be received again, the target cannot be detected.

JP 2010-261734 A JP 2011-117845 A

Higuchi, “Particle Filter”, IEICE Journal, Vol.88, No.12, pp.989-994, December 2005

  As described above, when the target detection is performed using the TBD algorithm, since the detailed position of the target is not known at the time of observation, the PRI cannot be switched, and there is a period during which the reflected wave from the target cannot be obtained. Consequently, the target detection operation during that time becomes unstable, and as a result, noise is erroneously detected, or even if the reflected wave can be received again, the target cannot be detected.

  The present embodiment has been made to solve the above problem, and a target detection apparatus and a target detection method capable of maintaining the target detection probability in a low SNR environment even when the TBD algorithm is used. The purpose is to provide.

  In order to solve the above problem, the target detection apparatus according to the present embodiment is a target detection apparatus that detects a target using a TBD (Track Before Detect) algorithm for a received detection signal of a radar reflected wave, The reception detection signal is converted into a cell reception signal for each resolution unit of distance and frequency in the observation region, and analysis processing means for analyzing the distance, frequency, and speed of each cell, and analysis of the cell reception signal and the previous observation time From the processing results, a target estimation point of the target distance and target speed at the current time is determined using a particle filter, and correlation processing means for determining whether or not the target estimation point is a transmission blanking period; and the analysis processing means And a detection processor that obtains the track of the target based on the analysis result and the transmission blanking period determination result of the target estimation point of the correlation processing means.

  The target detection method according to the present embodiment is a target detection method for detecting a target of a received detection signal of a radar reflected wave by using a TBD (Track Before Detect) algorithm, and the received detection signal is observed in an observation region. The distance, frequency, and speed of each cell are converted into cell reception signals, the distance, frequency, and speed of each cell are analyzed, and the current time using a particle filter is analyzed from the analysis processing results of the cell reception signals and the previous observation time. A target estimation point of the target distance and target speed is determined, it is determined whether the target estimation point is a transmission blanking period, and based on the analysis processing result and the determination result of the transmission blanking period of the target estimation point The target track is obtained.

The block diagram which shows schematic structure of the flying body in which the target detection apparatus which concerns on this embodiment is mounted. The block diagram which shows the structure of the target detection apparatus which concerns on this embodiment. FIG. 3 is a distribution diagram showing an analysis example of a received signal for each resolution unit (cell) of the observation area distance and frequency obtained by the analysis processor shown in FIG. The flowchart which shows the flow of a process of the correlation processor shown in FIG. FIG. 5 is a distribution diagram illustrating an example of a blanking determination target section of the correlation process illustrated in FIG. 4. FIG. 5 is a distribution diagram showing another example of the blanking determination target section of the correlation process shown in FIG. 4. In the correlation process shown in FIG. 4, the distribution diagram illustrating the position of the particles when the process is resumed after passing through the transmission unit ranking.

  Hereinafter, embodiments will be described with reference to the drawings.

  FIG. 1 is a block diagram showing a schematic configuration of a flying object on which the target detection device according to the present embodiment is mounted. The flying object 1 shown in FIG. 1 includes a guidance device 2 that generates a guidance signal for flying in the direction of the target T, and a steering device 3 that changes the flying posture in the direction of the target T according to the guidance signal. The guidance device 2 includes a target detection device 4 that detects the target T and a target tracking device 5 that generates a guidance signal.

  FIG. 2 is a block diagram showing a specific configuration of the target detection device 4. 2 includes an antenna 11 that receives a radar reflected wave from the target T, a receiver 12 that detects the reflected wave, an A / D converter 13 that converts the detected signal into a digital signal, It comprises a target detector 14 that detects a target from a digital detection signal using the TBD algorithm and obtains its track.

  The target detector 14 detects the target from the analysis processor 15 that performs an analysis operation of the digital detection signal, the correlation processor 16 that performs correlation processing and blanking determination processing on the analysis processing result, and the correlation processing / determination processing result. A detection processor 17 for obtaining a wake is provided.

  In the above configuration, the operation of the target detection device 4 will be described below.

  The radar reflected wave from the target T is received by the antenna 11 and detected by the receiver 12. The detected signal is converted into a digital signal by the A / D converter 13. The digital detection signal is captured by the target detector 14 and used for target detection processing.

  The digital detection signal captured by the target detector 14 is Fourier-transformed by the analysis processor 15 and converted from a time domain signal to a frequency domain signal. As shown in the distribution diagram of FIG. Equivalent) and the received signal for each frequency resolution unit (cell). The analysis processor 15 analyzes the distance and frequency for each cell and calculates the Doppler shift amount of the frequency to analyze the speed. The correlation processor 16 uses the particle signal to obtain the target point of the target distance and target speed at the current time (hereinafter referred to as target target point) from the received signal for each cell obtained by the analysis processor 15 and the analysis result of the previous observation time. ).

Here, the processing of the correlation processor 16 will be described with reference to the correlation processing flowchart shown in FIG.
First, a correlation value between the received signal for each cell and the previous time is acquired (step S1).
Subsequently, correlation processing is performed using a particle filter (see publicly known document 1) (steps S2 to S4). That is, in step S2, predicted values of the current distance and frequency are set for the particles (target estimated points) obtained at the previous time. Next, in step S3, the likelihood is calculated from the value of the input (received signal for each cell) corresponding to the predicted distance and frequency of each particle. Then, in step S4, a thing with a high likelihood is extracted and this is made into the particle | grains of this time.

  Next, blanking determination processing is performed (steps S5 to S7). First, in step S5, the number of particles in a preset target section is counted. For example, as shown in FIG. 5, the target section is for two to three ranges adjacent to the distance range corresponding to the blanking region (far side). Since the target speed is faster as the frequency is higher, as shown in FIG. 6, the target section may be changed according to the frequency, and the target section in the higher frequency region may be longer than the lower frequency region.

In step S6, if the counted number of particles is larger than a preset determination threshold value, the additional processing in step S7 is executed, and if it is less, step S8 is executed.
The additional process of step S7 is a process for coping while the target is in the blanking area. In the additional processing, for example, the processing is paused until transmission blanking passes, and the processing is resumed after passing. When restarting, as shown in FIG. 7, the particle distribution (position) is shifted to the front side of the distance range corresponding to the blanking region. The pause time is obtained from the length of transmission blanking (known) and the target speed (can be estimated in the process of observation and correlation processing).
Steps S1 to S7 are repeated up to the number of repetitions set in advance in step S8.

  The correlation processing result of the particles detected by the correlation processor 16 is sent to the detection processor 17. In this detection processor 17, particles having a likelihood exceeding a preset threshold or particles having a number exceeding the preset threshold in the same cell are detected as targets. In addition, the track of the target being observed (change in speed and distance) is obtained from the correlation processing information of the detected particles. From the distance information and the speed information, compare the average value of the speed information within the observation time and the speed calculated from the distance change during the observation time. Are considered false detections and excluded from the detection results.

  Here, in the above particle filter, the likelihood of particles is calculated from the observed values, and the particles are gradually concentrated in the cell where the target is supposed to exist. It can be recognized that there is a target if the particles are concentrated in about 1 to 2 cells before the transmission blanking period starts, but it cannot be recognized as a target in a state where the particles are scattered over several cells. However, it can be recognized that “maybe” by allowing a wider range for counting the number of particles. By utilizing this, it is possible to effectively perform processing that avoids blanking by detecting that the target is within the transmission blanking period.

  As described above, according to the present embodiment, it is possible to maintain and improve the target detection probability even in a high PRF, even in a low SNR environment when the TBD algorithm is used.

  Note that the present embodiment is not limited to the above-described embodiment as it is, and can be embodied by modifying constituent elements without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

DESCRIPTION OF SYMBOLS 1 ... Flying object, 2 ... Guidance device, 3 ... Steering device, 4 ... Target detection device, 5 ... Target tracking device, 11 ... Antenna, 12 ... Receiver, 13 ... A / D converter, 14 ... Target detection part, 15 ... analysis processor, 16 ... correlation processor, 17 ... detection processor.

Claims (8)

A target detection apparatus for detecting a target using a TBD (Track Before Detect) algorithm for a received detection signal of a radar reflected wave,
An analysis processing means for converting the reception detection signal into a cell reception signal for each resolution unit of the observation area distance and frequency, and analyzing the distance, frequency, and speed of each cell from the cell reception signal;
From the analysis result of the cell reception signal and the previous observation time, the target estimation point of the target distance and target speed of the current time is determined using a particle filter, and it is determined whether or not the target estimation point is in the transmission blanking period Correlation processing means to
And a detection processor for obtaining a track of the target based on an analysis result of the analysis processing unit and a transmission blanking period determination result of the target estimation point of the correlation processing unit. The correlation processor
Obtaining a correlation value between the cell reception signal and the previous time;
As the correlation processing by the particle filter, the predicted value of the current distance and frequency is set for the particle that is the target estimated point obtained at the previous time, and the value of the cell reception signal corresponding to the predicted distance and frequency of each particle is set. Calculate the degree, extract the one with the highest likelihood and use this as the particle at this time,
Count the number of particles in the target section outside the preset blanking period,
Determine whether the number of counted particles is greater than a preset decision threshold,
The target detection apparatus according to claim 1, wherein if the number of particles is larger than a determination threshold value, an additional process is performed to cope with a target in the transmission blanking region.   The additional process is to pause the process until passing through the transmission blanking region, and restart the process after passing, and when restarting, the particle distribution is shifted to the near side of the distance range corresponding to the transmission blanking region, 3. The target detection apparatus according to claim 2, wherein the pause time is obtained from a length of the transmission blanking region and a target speed. The detection processor is:
Comparing the correlation processing result of the particles detected by the correlation processor with a preset threshold value, particles having a likelihood exceeding the threshold value or particles having a number exceeding the threshold value at the same point Is detected as a goal,
From the correlation processing result of the detected particles, a wake indicating the change in the distance and speed of the target being observed is obtained,
The average value of the speed information within the observation time is compared with the speed calculated from the distance change amount within the observation time from the distance information and speed information of the target, and when the difference is larger than a predetermined threshold value, the target The target detection apparatus according to claim 1, wherein the target detection device is regarded as a false detection of noise rather than being excluded from the detection result. A target detection method for detecting a target using a TBD (Track Before Detect) algorithm for a received detection signal of a radar reflected wave,
The received detection signal is converted into a cell reception signal for each unit of resolution of the observation area distance and frequency, and the distance, frequency, and speed of each cell are analyzed from the cell reception signal,
From the analysis result of the cell reception signal and the previous observation time, the target estimation point of the target distance and target speed of the current time is determined using a particle filter, and it is determined whether or not the target estimation point is in the transmission blanking period And
A target detection method, wherein a track of the target is obtained based on a result of the analysis processing and a determination result of a transmission blanking period of the target estimation point. The determination process of the transmission blanking period includes
Obtaining a correlation value between the cell reception signal and the previous time;
For particles that are target estimation points obtained at the previous time, set the predicted value of the current distance and frequency, calculate the likelihood from the value of the cell reception signal corresponding to the predicted distance and frequency of each particle, and the likelihood Is extracted and used as the particle at the current time,
Count the number of particles in the target section outside the preset blanking period,
Determine whether the number of counted particles is greater than a preset decision threshold,
6. The target detection method according to claim 5, wherein if the number of particles is larger than a determination threshold value, an additional process is performed to cope with a target in the transmission blanking region.   The additional process is to pause the process until passing through the transmission blanking region, and restart the process after passing, and when restarting, the particle distribution is shifted to the near side of the distance range corresponding to the transmission blanking region, 7. The target detection method according to claim 6, wherein the pause time is obtained from a length of the transmission blanking region and a target speed. The detection process includes
Comparing the correlation processing result of the particles detected by the correlation processor with a preset threshold value, particles having a likelihood exceeding the threshold value or particles having a number exceeding the threshold value at the same point Is detected as a goal,
From the correlation processing result of the detected particles, a wake indicating the change in the distance and speed of the target being observed is obtained,
The average value of the speed information within the observation time is compared with the speed calculated from the distance change amount within the observation time from the distance information and speed information of the target, and when the difference is larger than a predetermined threshold value, the target The target detection method according to claim 5, wherein the target detection method is regarded as a false detection of noise rather than being excluded from the detection result.

Images