JP2010175383A - Target detection apparatus and target detection method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a target detection apparatus improving target detection precision. <P>SOLUTION: The target detection apparatus includes: an image processor 10 acquiring the angle and distance for every temperature regions from the distance of a lasr macrometer 9 by dividing the image data of an infrared camera 8 for each of the temperature regions; a polarization-switching device 3 collecting the radar signal of an observation target by driving any one of two antennas 1, 2 having a mutually orthogonal polarization property for a transmission and by driving both of the antennas for a reception; an observed scattering vector accumulator 7 for storing the laser signal as the scattering vector for each of resolution cells; a laser signal divider 11 for dividing the scattering vectors for each of the temperature regions by extracting the resolution cell of the corresponding scattering vectors using the acquired angle and distance for each of the temperature regions; a notch filter circuit 12 for generating a filter from the scattering vectors divided for each of the temperature regions, performing application processing of the filter to each of the resolution cells in the temperature region and outputting an electric power for each of the temperature region; and a threshold value circuit 13 for discriminating the target and a clutter by comparing the electric power to the threshold value. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to the field of radar devices, and more particularly to a target detection device and a target detection method for detecting a target using polarization information.

  A radar device mounted on an aircraft observes the ground surface and the vicinity of the sea surface by transmitting and receiving radio waves from the sky, and detects small targets existing near the ground surface and the sea surface. Here, the small target means a target having a low radio wave reflection intensity, and is not necessarily a target having a small physical size. When this type of radar apparatus observes the ground surface or the vicinity of the sea surface, generally strong echoes from the ground surface or the sea surface are received. They are called “ground clutter” and “sea clutter”, respectively. In this specification, echoes from the background such as ground clutter and sea clutter are collectively referred to simply as “clutter”. Therefore, it is necessary to suppress clutter in advance in order to detect an echo from a target existing near the ground surface or the sea surface from the received radar signal. The echo from the target is called a “target signal”.

  As a conventional clutter suppression technique in a radar apparatus, there is a technique called MTI (Moving Target Indicator) that suppresses clutter using a Doppler frequency difference between a target signal and a clutter (see, for example, Non-Patent Document 1). This is a method of suppressing clutter by determining a clutter and a target signal based on the speed difference between the background and the target assuming a small target that moves like a vehicle or a ship.

  Further, as a clutter suppression method for detecting a stationary target, there is a method of detecting a target by suppressing the clutter while paying attention to the difference between the polarization characteristics of the target and the background (see, for example, Non-Patent Document 2). . This method transmits and receives radio waves with a combination of two polarizations orthogonal to each other (for example, horizontal polarization (H polarization) and vertical polarization (V polarization)) to obtain the background and target polarization characteristics. It measures and suppresses the portion corresponding to the polarization characteristic of the clutter in the received signal.

  An example of the latter method is an adaptive notch filter (see, for example, Patent Document 1). The target detection apparatus using an adaptive notch filter includes a first polarization transmission / reception antenna, a second polarization transmission / reception antenna, a polarization switch, a transmission / reception switch, a receiver, a transmitter, an observed scatter vector accumulator, an adaptive polar It consists of a remetric notch filter circuit, a threshold circuit, and a display.

  Next, the operation of the conventional adaptive notch filter will be described. Either one of the first polarized wave transmitting / receiving antenna and the second polarized wave transmitting / receiving antenna is driven for transmission and both are driven for reception, and four types of radar signals are collected for the observation target. The radar signal is stored in the observed scatter vector accumulator as a scatter vector Xk for each resolution cell k (k = 1, 2,..., K: K is the number of resolution cells). The scattering vector is obtained by using four types of radar signals as one component of a column matrix, and is called a “scattering vector” in the sense of a vector representing scattering characteristics. In this adaptive notch filter, a filter coefficient is generated by using a scattering vector of a resolution cell considered to be a clutter.

  In the filter coefficient creation method, first, a resolution cell that is considered to be a clutter is used as a reference cell, and a covariance matrix is calculated from a scattering vector. An eigenvalue analysis of this covariance matrix is performed, and the adaptive polarimetric notch filter that outputs power normalized by the average power is suppressed for the principal component having the largest power and the other components are output. Generate filter coefficients. The created filter is applied to each resolution cell to suppress clutter. The stationary signal is detected by comparing the output signal of the filter with a set threshold value.

JP 2003-185733 A (2nd page, FIG. 1)

M. I. Skolnik, “Introduction to Radar Systems,” Second Edition, McGraw-Hill, 1980 L. M. Novak, M.C. Burl, W.W. Irving, “Optimal polarimetric processing for enhanced target detection,” IEEE Transactions on Aerospace and Electronic Systems, Vol. 29, No. 1, pp.234-244, Jan. 1993

  However, the prior art has the following problems. First, the clutter component suppression effect differs depending on how the reference cell is selected. In addition, when there are multiple types of clutter (for example, when there is water and soil clutter or when there is asphalt and soil), a filter is formed from one type of clutter component or a mixture of multiple types of clutter. . For this reason, the clutter component suppression effect is reduced.

  The present invention has been made to solve the above-described problems, and suppresses clutter components for each type of clutter using an optical sensor, and suppresses clutter components for each type of clutter. An object of the present invention is to provide a target detection device and a target detection method that can enhance the suppression effect of clutter components and improve target detection accuracy.

  A target detection apparatus according to the present invention includes an infrared camera that irradiates infrared rays to acquire image data of an observation target, a laser range finder that measures the distance of the observation target, and image data acquired by the infrared camera as temperature. Dividing into regions and obtaining the distance of multiple points for each temperature region from the distance measured by the laser range finder, and the image processor for obtaining the angle and distance of each temperature region, and the polarization characteristics orthogonal to each other A polarization switch that collects radar signals to be observed by driving either one of the first and second antennas for transmission and both for reception The observation scatter vector accumulator that stores the radar signal as a scatter vector for each resolution cell related to the observation target, and the angle and distance for each temperature region obtained by the image processor, are used for the observation. A resolution vector of the corresponding scattering vector is extracted from the scattering vector accumulator, and a radar signal divider that divides the scattering vector, which is a radar signal, for each temperature region, and a scattering vector divided for each temperature region by the radar signal divider An adaptive polarimetric notch filter circuit that generates a filter for each temperature region, applies a filter generated for each temperature region to each resolution cell in the temperature region, and outputs power for each temperature region; And a threshold circuit for comparing the power with a preset threshold value and discriminating between a target and clutter.

  According to the target detection device of the present invention, the clutter component is suppressed for each type of clutter using an optical sensor, the clutter component is suppressed for each type of clutter, and the suppression effect of the clutter component is enhanced. The target detection accuracy can be improved.

It is a block diagram which shows the structure of the target detection apparatus which concerns on Embodiment 1 of this invention. It is a figure which shows the observation scattering vector accumulate | stored in the observation scattering vector accumulator of the target detection apparatus which concerns on Embodiment 1 of this invention. It is a block diagram which shows the structure of the target detection apparatus which concerns on Embodiment 2 of this invention. It is a block diagram which shows the structure of the target detection apparatus which concerns on Embodiment 3 of this invention.

  Hereinafter, preferred embodiments of a target detection apparatus and a target detection method of the present invention will be described with reference to the drawings.

Embodiment 1 FIG.
A target detection apparatus according to Embodiment 1 of the present invention will be described with reference to FIGS. FIG. 1 is a block diagram showing a configuration of a target detection apparatus according to Embodiment 1 of the present invention. In the following, in each figure, the same reference numerals indicate the same or corresponding parts.

  In FIG. 1, a target detection apparatus according to Embodiment 1 of the present invention is mounted on an aircraft or the like, and has first polarization transmission / reception antenna 1 and second polarization transmission / reception antenna 2 having polarization characteristics orthogonal to each other. One of the two antennas 1 and 2 (the first and second antennas) has a bias that drives one of them for transmission and both of them for reception and collects radar signals to be observed such as near the ground surface and the sea surface. A wave switch 3, a transmission / reception switch 4 for switching between transmission and reception, a receiver 5 for demodulating a radar signal sent from the polarization switch 3 through the transmission / reception switch 4, and a broadband pulse to generate and switch transmission / reception A transmitter 6 that is sent to the polarization switching device 3 via the device 4, an observation scatter vector accumulator 7 that stores the radar signal as a scatter vector for each resolution cell related to the observation object, and an infrared ray for observing the type of clutter. An infrared camera 8 that irradiates and acquires image data to be observed, a laser range finder 9 that measures the distance of the observation target, and image data acquired by the infrared camera 8 are divided into temperature regions, and the laser range finder An image processor 10 is provided that obtains the distance of a plurality of points for each temperature region from the distance measured by 9 and obtains the angle and distance of each temperature region.

  Further, by using the angle and distance for each temperature region obtained by the image processor 10, the corresponding scattering vector resolution cell is extracted from the observed scattering vector accumulator 7, and the scattering vector, which is a radar signal, is divided for each temperature region. The filter is generated for each temperature region from the radar signal divider 11 to be performed and the scattering vector divided for each temperature region by the radar signal divider 11, and the filter generated for each temperature region is converted into each resolution cell in the temperature region. And an adaptive polarimetric notch filter circuit 12 that outputs power for each temperature region, and a threshold value for discriminating a target and a clutter by comparing the output power of the filter circuit 12 with a preset threshold value. A circuit 13 and a display 14 for outputting the position of the resolution cell determined as the target by the threshold circuit 13 are provided.

  Next, the operation of the target detection apparatus according to the first embodiment will be described with reference to the drawings. FIG. 2 is a diagram showing observed scatter vectors accumulated in the observed scatter vector accumulator of the target detection apparatus according to Embodiment 1 of the present invention.

  First, observation is performed with the infrared camera 8. The image processor 10 divides the image data acquired by the infrared camera 8 for each temperature region. Further, the image processor 10 obtains a plurality of distances for each temperature region by using the distance measured by the laser distance measuring device 9, and obtains the angle and distance of each temperature region.

  At the same time, observation using a radar is performed. The transmitter 6 sends the generated broadband pulse to the polarization switch 3 via the transmission / reception switch 4. The polarization switch 3 sends a transmission signal to the first polarization transmission / reception antenna 1 out of the first polarization transmission / reception antenna 1 and the second polarization transmission / reception antenna 2.

  Here, the first polarization transmitting / receiving antenna 1 and the second polarization transmitting / receiving antenna 2 are a set of antennas whose polarization characteristics are orthogonal to each other. For example, a pair of vertical polarization and horizontal polarization, a pair of right-handed circular polarization and left-handed circular polarization, etc. are well known as the two orthogonal polarization characteristics.

  The signal transmitted from the first polarization transmitting / receiving antenna 1 is scattered by the observation target. This is received by the first polarization transmitting / receiving antenna 1 and the second polarization transmitting / receiving antenna 2 and sent to the polarization switch 3. These signals are sent to the receiver 5 via the transmission / reception switch 4.

  The signal demodulated by the receiver 5 is stored in the observed scattering vector accumulator 7 in the form of reflection coefficients S11 and S21 to be observed. Here, Sij represents a reflection coefficient to be observed, which is transmitted by the j-th polarization transmitting / receiving antenna and received by the i-th polarization transmitting / receiving antenna.

  Similarly, the transmitter 6 sends the generated broadband pulse to the polarization switch 3 via the transmission / reception switch 4 and irradiates the target from the second polarization transmitting / receiving antenna 2 to repeat the same processing. Thus, the reflection coefficients S12 and S22 to be observed are obtained. This is similarly stored in the observed scatter vector accumulator 7.

  A matrix display of the observed S11, S12, S21, and S22 is referred to as a scattering matrix [S]. Also, what is expressed by the column vector X is called a “scattering vector” in the sense of a vector representing scattering characteristics.

  In S11, S12, S21, and S22, as shown in FIG. 2, resolution cell k (k = 1, 2,..., K: K is the number of resolution cells) relating to the observation object in the observed scatter vector accumulator 7. Each is stored as a scattering vector Xk.

  The radar signal divider 11 extracts the resolution cell of the corresponding radar signal (scattering vector) using the angle and distance information for each temperature region obtained by the image processor 10, and divides the radar signal into each temperature region. . The adaptive polarimetric notch filter circuit 12 generates a filter for each temperature region from a radar signal divided for each temperature region. The adaptive polarimetric notch filter circuit 12 applies a filter generated for each temperature region to each resolution cell in the temperature region, and outputs power P for each temperature region.

  When the observation point of the radar and the observation point of the infrared camera 8 are accurately known, it is not necessary to perform the observation using the radar and the observation using the infrared camera 8 at the same time, either one may be performed first. This is because if the exact position of the observation point is not known, the corresponding radar signal cannot be extracted from the angle information and distance information for each temperature region obtained by the image processor 10 as described above.

  Next, the power P for each temperature region output from the adaptive polarimetric notch filter circuit 12 is sent to the threshold circuit 13. The threshold circuit 13 compares the input power P with the threshold T, and determines that the target is when the power P is greater than the threshold T or the power P is equal to the threshold T, and the case where the power P is lower than the threshold T is determined as clutter. To do. The display 14 outputs the position of the resolution cell determined as the target as the target detection result.

  As described above, according to the first embodiment, even in the terrain composed of a plurality of types of clutter, the clutter component is suppressed for each type of clutter, so that a high target detection probability can be maintained. It becomes. Further, the first embodiment can be easily expanded when the radar configuration is bistatic.

Embodiment 2. FIG.
A target detection apparatus according to Embodiment 2 of the present invention will be described with reference to FIG. FIG. 3 is a block diagram showing a configuration of the target detection apparatus according to Embodiment 2 of the present invention.

  In FIG. 3, in addition to the configuration of the target detection apparatus according to the first embodiment, the target detection apparatus according to the second embodiment of the present invention is provided with a split condition input unit 15 for inputting a condition for splitting. .

  Next, the operation of the target detection apparatus according to the second embodiment will be described with reference to the drawings.

  In the second embodiment, when the image data acquired by the infrared camera 8 is divided for each region, the image processor 10 inputs a condition for division by the division condition input unit 15. The condition for the division is that the operator confirms the image of the infrared camera 8 and determines the area.

  Next, the image processor 10 obtains the distances of a plurality of points for each divided area using the distance information measured by the laser distance measuring device 9. In the following, target detection is performed by the same processing as in the first embodiment. Each region corresponds to each temperature region.

  Therefore, according to the second embodiment, since the operator can directly select a region to be divided, a high target detection probability can be maintained even when the temperature difference between different types of clutter is small. It becomes.

Embodiment 3 FIG.
A target detection apparatus according to Embodiment 3 of the present invention will be described with reference to FIG. FIG. 4 is a block diagram showing a configuration of a target detection apparatus according to Embodiment 3 of the present invention.

  In FIG. 4, in addition to the configuration of the target detection apparatus according to the first embodiment, the target detection apparatus according to the third embodiment of the present invention has three-dimensional terrain data (height as shown in an overhead view). Map data 16 including three-dimensional data including information) and a self-position measuring device 17 that measures a three-dimensional self-position (for example, latitude, longitude, and height) are provided.

  Next, the operation of the target detection apparatus according to the third embodiment will be described with reference to the drawings.

  In the third embodiment, the image processor 10 acquires the terrain data to be observed (for example, the position of the road or the position of the building) from the map data 16 from the self-position measured by the self-position measuring device 17.

  The image processor 10 compares the acquired terrain data with the image data acquired by the infrared camera 8 and corrects the terrain data. This process is for correcting an error (for example, when the observation target has a height). The image processor 10 divides the corrected terrain data to be observed into terrain areas.

  Next, the image processor 10 obtains the distances of a plurality of points for each terrain area divided using the distance information measured by the laser rangefinder 9. In the following, target detection is performed by the same processing as in the first embodiment. Each terrain area corresponds to each temperature area.

  Therefore, according to the third embodiment, since the map data 16 is used to select a region to be divided, a clutter component whose position is known in advance such as a road can be efficiently suppressed. It becomes possible to maintain the detection probability.

  DESCRIPTION OF SYMBOLS 1 1st polarized wave transmission / reception antenna, 2nd 2nd polarization transmission / reception antenna, 3 Polarization switch, 4 Transmission / reception switch, 5 Receiver, 6 Transmitter, 7 Observation scattering vector accumulator, 8 Infrared camera, 9 Laser ranging , 10 image processor, 11 radar signal divider, 12 adaptive polarimetric notch filter circuit, 13 threshold circuit, 14 indicator, 15 division condition input device, 16 map data, 17 self-position measuring device.

Claims (7)

An infrared camera that irradiates infrared rays to acquire image data of the observation target;
A laser range finder for measuring the distance of the observation object;
Image processing obtained by dividing the image data acquired by the infrared camera for each temperature region, obtaining a plurality of distances for each temperature region from the distance measured by the laser distance measuring device, and obtaining an angle and a distance of each temperature region And
First and second antennas having polarization characteristics orthogonal to each other;
Of the first and second antennas, a polarization switching device that drives either one in transmission and both in reception and collects radar signals to be observed;
An observation scatter vector accumulator for storing the radar signal as a scatter vector for each resolution cell relating to the observation object;
A radar that extracts the resolution vector of the corresponding scatter vector from the observed scatter vector accumulator using the angle and distance for each temperature region obtained by the image processor, and divides the scatter vector as a radar signal for each temperature region A signal splitter;
From the scattering vector divided for each temperature region by the radar signal divider, a filter is generated for each temperature region, and the filter generated for each temperature region is applied to each resolution cell in the temperature region. An adaptive polarimetric notch filter circuit that outputs power every time;
A target detection apparatus comprising: a threshold circuit that compares the power with a preset threshold value to determine a target and a clutter. A duplexer that switches between transmission and reception;
A transmitter that generates a broadband pulse and sends it to the polarization switch via the duplexer;
A receiver that demodulates a radar signal transmitted from the polarization switch via the transmission / reception switch;
The target detection apparatus according to claim 1, further comprising a display that outputs a position of a resolution cell determined as a target by the threshold circuit. A split condition input device for inputting a split condition;
3. The target detection apparatus according to claim 1, wherein the image processor divides image data acquired by the infrared camera for each region based on a dividing condition input by the dividing condition input unit. . A self-position measuring device for measuring three-dimensional self-position;
Map data including 3D terrain data to be observed
The image processor acquires terrain data to be observed from the map data based on the self-position measured by the self-position measuring device, and compares the terrain data with the image data obtained by the infrared camera. The target detection apparatus according to claim 1 or 2, wherein the corrected topographic data of the observation target is divided for each region. Irradiating infrared rays with an infrared camera to obtain image data to be observed; and
Dividing the image data acquired by the infrared camera for each temperature region, obtaining the distance of a plurality of points for each temperature region from the distance measured by the laser range finder, obtaining the angle and distance of each temperature region;
Simultaneously with the observation by the infrared camera, either one of the first and second antennas having polarization characteristics orthogonal to each other is driven for transmission and both are received for reception to collect radar signals to be observed. Steps,
Storing the radar signal as a scatter vector for each resolution cell for the observation object;
Extracting the corresponding scattering vector resolution cell from the stored scattering vector using the obtained angle and distance for each temperature region, and dividing the scattering vector as a radar signal for each temperature region;
A filter is generated for each temperature region from the scattering vector divided for each temperature region, the filter generated for each temperature region is applied to each resolution cell in the temperature region, and power is output for each temperature region. Steps,
Comparing the power with a preset threshold value and discriminating between a target and a clutter. Instead of the step of dividing the image data acquired by the infrared camera for each temperature region, obtaining the distance of a plurality of points for each temperature region from the distance measured by the laser rangefinder, and obtaining the angle and distance of each temperature region In addition,
Based on the division condition input by the division condition input unit, the image data acquired by the infrared camera is divided for each region, and the distance of a plurality of points is obtained for each region from the distance measured by the laser rangefinder, The target detection method according to claim 5, further comprising a step of obtaining an angle and a distance of each region. Instead of the step of dividing the image data acquired by the infrared camera for each temperature region, obtaining the distance of a plurality of points for each temperature region from the distance measured by the laser rangefinder, and obtaining the angle and distance of each temperature region In addition,
Acquire the topographic data of the observation object from the map data based on the self-position measured by the self-position measuring device, match the topographic data with the image data acquired by the infrared camera, correct the topographic data, and the corrected observation target 6. The method according to claim 5, further comprising the steps of: dividing the topographical data of each area into areas, obtaining a plurality of distances for each area from distances measured by the laser range finder, and obtaining an angle and a distance of each area. The target detection method described.

Images