JP3279832B2 - Multi-target radar image processing method and apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-target radar image processing method and apparatus suitable for processing images of a plurality of targets obtained through an inverse synthetic aperture radar mounted on an air vehicle such as an aircraft.

[0002]

2. Description of the Related Art As is well known, an inverse synthetic aperture radar is
This is a technique for obtaining a radar image of a target object by rotating the object.

[0003] Further, as an apparatus for collecting an image of a target ship or the like from an airplane such as an aircraft using such an inverse synthetic aperture radar technique and identifying the same, the apparatus shown in FIG. 3 is generally known. Have been.

That is, as shown in FIG. 3, this device is mainly composed of an antenna device 10, a transmission / reception device 20, a signal processing device 30, and a display device 40. A reflected wave by a target of a radar beam radiated at a predetermined beam width on the azimuth plane and the elevation plane through the transmission / reception apparatus 20 and the antenna apparatus 10 is received through the antenna apparatus 10 and the transmission / reception apparatus 20, and a video signal obtained by the reception is received. Is operated to form a predetermined image through the signal processing device 30 and display the image on the display device 40.

[0005] Here, the signal processing device 30 detects a target existing in the radar search area based on the obtained video signal, outputs the position information to the display device 40, and outputs the position information to the antenna. The antenna device 10 is configured to include a target detection circuit 31 that feeds back the radar beam emitted from the antenna 12 through the control circuit 11 based on the feedback position information. Capture that target.

However, since there are usually a plurality of target ships in the radar search area, when capturing such targets, the radar operator or the like determines the priority of the targets to be imaged. Typically, one goal is selected based on a defined priority. When one target is selected in this way, the position information about the selected target is fed back from the target detection circuit 31 to the control circuit 11 in the antenna device 10, and is emitted from the antenna 12 through the control circuit 11. The radar beam is controlled to track the selected target. After the target has been detected and selected in this manner, the selected target is continuously irradiated with a radar beam.

On the other hand, an image processing circuit 32 also provided in the signal processing device 30 outputs an I / Q video signal obtained by orthogonally detecting the radar reflected wave (corresponding to the area of the target) from the target thus captured (selected). , That is, to the amplitude / phase information,
The image processing in the mode shown in FIG. 4 is performed, the obtained target image is displayed on the display device 40, and the image information is transmitted to the identification processing circuit 33.

That is, in the image processing circuit 32, as shown in FIG. 4, (1) target information (amplitude / phase information) spreading in two dimensions (distance direction and azimuth direction) is, for example, The distance component is corrected by compression (the distance correction unit 32
1).

(2) In addition to the distance-corrected target information,
The Doppler correction based on the Doppler frequency generated by the shaking (rotational movement) of the target is performed to remove the speed component of the moving target (Doppler correction unit 322).

(3) The Doppler-corrected target information is subjected to corner turn processing at an appropriate resolution in the azimuth direction (sweep direction) and the distance direction (range direction) (corner turn memory 323).

(4) Finally, the information subjected to the corner turn processing is subjected to FFT (fast Fourier transform) processing to form an image, which is output to the display device 40 and the identification processing circuit 33 (F
FT section 324).

The information processed through the image processing circuit 32 is displayed as an image on the display device 40, for example, in a manner shown in FIG.

In FIG. 5, the vertical axis represents the Doppler frequency fd, and the horizontal axis represents the distance (range) R. For example, information about the vertical size S1, the horizontal size S2, and the like in the target image. Is compared with the identification information (feature information) in the pre-registered database in the identification processing circuit 33 to determine the target ship type, ship name, and the like. In the case of the above-described device, information on the determined ship type, ship name, and the like is also displayed on the display device 4.
It will be displayed together with 0. The identification processing circuit 3
The target feature information to be compared with the database in 3 may be artificially input to the identification processing circuit 33 by a radar operator or the like.

[0014]

By the way, in the image processing by the inverse synthetic aperture radar, as described above, the imaging is performed by detecting the Doppler frequency generated by the rotation of the target itself. From
The quality of the resulting image quality is also determined depending on the magnitude of the target rotational movement.

In the case of the above-mentioned ship, the rotational movement as the target is generated by the fluctuation caused by floating on the water surface. Therefore, the quality of the obtained image depends on the magnitude of the fluctuation. Change. When identifying the ship type and ship name of a target ship from such radar images, the quality of the obtained image quality is particularly problematic. In this case, the above-described image processing and identification processing must be performed at least for a period longer than the oscillation period.
In general, a ship's motion on the surface of the water has a cycle of up to 2
Considering that the time is 0 to 30 seconds, it takes about 20 to 30 seconds to image one ship and identify its type and ship name. Moreover, in the multi-target radar exemplified here, the above-described image processing and identification processing are usually repeated sequentially for a plurality of ships existing in the search area. If (N is an integer), processing time N times as long is required.

FIG. 6 schematically shows the concept of an image processing method performed through such an image processing apparatus for a multi-target radar.

As shown in FIG. 6, conventionally, after one target to be imaged is selected, a continuous period (20 to 30 seconds) until the sway (rotational motion) of the target is maximized. While tracking this, the above-mentioned imaging and identification are continuously performed, and thereafter, the radar beam is moved to the next selected target and the same processing is repeated. An enormous amount of time, expressed as one oscillation period (20 to 30 seconds) × N (the number of targets) [seconds], is required before the imaging and identification of the target If the number is small, still want to capture more targets from a longer distance and try to image and identify them, or want to minimize the power radiation for concealing the position of the aircraft as much as possible This is a problem in some cases.

The present invention has been made in view of the above circumstances, and is intended to allow a plurality of targets, such as a ship floating on the water surface, which oscillate at a relatively long cycle, to be sufficiently longer than the sway cycle of the targets. It is an object of the present invention to provide an image processing method and apparatus for a multi-target radar capable of imaging in a short time and with a quality sufficient for practical use, and thereby enabling quick and reliable identification of these targets.

[0019]

According to the present invention, although the quality of the obtained image quality certainly depends on the magnitude of the fluctuation of the target, the time required for imaging the target with respect to one target itself is not the same as that of the video signal. This is a very short time that depends only on the processing system, and even if one target is continuously imaged over the entire time corresponding to the target oscillation period, the magnitude of the rotational movement of the target is large. Since the change is very slow compared to the time required for this imaging, it is noted that there is no significant change in the quality of the obtained image itself, and based on the video signal obtained at the time of detecting the target, And collectively acquire in advance the position information for all of the plurality of targets, and irradiate a radar beam based on (a) the position information for each of the targets for which the position information has been acquired, and obtain the amplitude / Collecting the phase information; (b) imaging the target based on the collected amplitude / phase information; and (c) identifying the target from the obtained target image based on the identification information. Is repeated in a time-sharing manner at a period sufficiently shorter than the oscillation period of

[0020]

The above-mentioned steps (a) to (c) are conventionally known steps, but the time required to image one target is limited to the video signal processing system as described above. Since it is an extremely short time depending on the video signal, as long as the position information on all of the plurality of targets is collectively acquired in advance and this is appropriately stored, the processing in the processing system of the video signal is effectively performed. In accordance with the speed (time), it is possible to capture each of the plurality of targets (distribution of the radar beam) based on the acquired position information and to image the captured targets. In this case, since the steps (a) to (c) are repeated in a time-division manner, and sequentially and recursively for the same target,
Assuming that such processing is maintained for a time corresponding to the target oscillation period (for example, 20 to 30 seconds), the above-described conditions for obtaining a high-quality image, that is, all of the conditions corresponding to the target oscillation period, Track your goals over time,
The monitoring condition is satisfied in a pseudo manner, and it is possible to sequentially and recursively image these targets with a quality that is not much different from the quality of the image obtained by the conventional processing method.

According to such an image processing method,
Process for collecting information in (a) above and thereafter (b) to (c)
The steps (a) to (c) for the targets evaluated from the second onward among a plurality of targets can be performed independently of the steps related to imaging / identification of
Can be performed in parallel with the above-mentioned steps (b) to (c) for the target evaluated one immediately before, so that the above-mentioned imaging can be made more efficient. That is, for this purpose, an appropriate image memory for storing and holding information (target image information) to be subjected to the identification processing while the identification processing for one target is being performed may be prepared.

[0022]

FIG. 1 shows an embodiment of an image processing apparatus for a multi-target radar according to the present invention.

FIG. 1 also shows an apparatus for collecting an image of a target ship or the like from a flying object such as an aircraft using the above-described inverse synthetic aperture radar technology and identifying the image. Also, in FIG. 1, the same elements as those in the apparatus shown in FIG. 3 are denoted by the same reference numerals, and redundant description of these elements will be omitted.

In the apparatus according to this embodiment, FIG.
As shown in FIG. 2, an electronic scanning antenna device 50 is employed as the antenna device to improve the efficiency and responsiveness of scanning control of the emitted radar beam.

That is, the electronic scanning antenna device 50
The antenna is configured to have an antenna 52 in an array configuration, and the phase of each array is controlled through a control circuit 51 to electronically control the direction of the antenna beam. Each of the arrays includes a transmission / reception amplifier (not shown). In each of these arrays, amplification / radiation of transmission power applied from the transmission / reception device 20 and high frequency amplification of power reflected from a target are performed. And so on. The received power (reflected power) from the target, which has been high-frequency amplified in this way, is then applied to the transmission / reception device 20, and is further amplified, frequency-converted, and detected through the transmission / reception device 20, and becomes the video signal described above. It is input to the device 60.

The signal processing device 60 basically detects the target existing in the radar search area based on the input video signal, as in the signal processing device 30 (FIG. 3) described above, and detects the position information. A target detection circuit 61 that outputs the position information to the display device 40 and feeds back the position information to the antenna device 50 is provided. The signal processing device 60 according to this embodiment further includes a target detection circuit 61 that is provided in the radar search area. And a tracking memory circuit 64 in which position information detected by the target detection circuit 61 is collectively stored and stored for the target.
Then, the position information of all the targets collectively stored in the tracking memory circuit 64 is stored in the above-described target oscillation cycle (20 to 3).
0 second), and feeds it back to the control circuit 51 of the antenna device 50, while sequentially reading it at a period sufficiently shorter than 0 seconds). The reading of such position information by the target detection circuit 61 and the feedback of the read position information to the antenna device 50 are repeatedly executed within one target oscillation cycle.

Thus, in the antenna device 50, the phase of each array constituting the antenna 52 is controlled one after another at the above-described cycle based on the above-mentioned feedbacked position information, and emitted from the antenna 52 through the control circuit 51. The radar beam is continuously irradiated on the target in each case only for the selected period. Also in this case, the selection order of the plurality of targets, that is, the target detection circuit 6 of the position information stored in the tracking memory circuit 64.
The order of reading through 1 is appropriately determined by a radar operator or the like when the target is detected through the target detection circuit 61 and the display device 40.

On the other hand, the image processing circuit 62 in the signal processing device 60 is also basically
2 (FIG. 3), the I / Q video signal obtained by orthogonal detection of the radar reflected wave (corresponding to the target area) from the target thus captured (selected), that is, the amplitude / phase information, This is a circuit for performing an imaging process in the same manner as that shown in FIG. However, according to this embodiment, the signal processing device 60 is also provided with an image memory circuit 65 for temporarily storing and holding the information to be imaged. The stored information is temporarily stored in the image memory circuit 65, and the stored and stored image information is displayed on the display device 40.
And input to the identification processing circuit 63. The display device 40 displays the image information (target information) stored and held in the manner illustrated in FIG.

The identification processing circuit 63 has a built-in database having characteristic information on various types of ships as identification information, similarly to the identification processing circuit 33 (FIG. 3).
This is a circuit for comparing the image information stored and held in the image memory circuit 65 with the identification information in this database to determine the target ship type, ship name, and the like. The determination result is also displayed on the display device 40 together with the target image.

The signal processing device 60 according to this embodiment
In the above, the switching of the image information to be stored and held in the image memory circuit 65 is performed by clearing the output from the target detection circuit 64 in accordance with the timing of reading the target position information from the tracking memory 64 by the target detection circuit 61. It is assumed that this is performed by the signal CR. That is, the image memory circuit 65 stores and holds the image information on the target while the information imaged by the image processing circuit 62 is being identified by the identification circuit 63.

FIG. 2 shows the image processing operation executed through such an apparatus in chronological order. The image processing method according to the present invention will be described in further detail with reference to FIG. Will be described.

First, in FIG. 2, "# 1", "#
2 ","# 3 ",..."#N"is a number conveniently assigned according to the selection order for each of the targets (ships) for which the number N has been detected. It is assumed that the width T1 represents the time required to image each of these targets.

In FIG. 2, T2 represents the cycle time (20 to 30 seconds) of the above-mentioned rocking (rotational motion) of the target ship on the water surface, and T3 represents the apparatus of this embodiment. Represents the period of time required to collect image information for the above number N targets.

That is, in the apparatus of this embodiment, N ships existing in the radar search area are detected, and their position information is stored in the tracking memory circuit 64.
In response to the reading of the position information by a predetermined cycle (the cycle time is empirically determined according to the time T1 required for imaging the one target in the apparatus), the position information is read in the following manner. And processing for identification.

(1) Based on the position information of the first ship (# 1), the first ship (# 1) is continuously irradiated with a radar beam, and the amplitude of the reflected area / The phase information is collected through the antenna device 50 and the transmitting / receiving device 20 (period t11 in FIG. 2).

(2) First ship obtained (# 1)
Based on the amplitude / phase information of the second ship (# 2), a radar beam is applied to the second ship (# 2) based on the position information of the second ship (# 2) while imaging the image through the image processing device 62. Continuous irradiation is performed, and amplitude / phase information corresponding to the reflected area is collected through the antenna device 50 and the transmission / reception device 20 (period t12 in FIG. 2).

(3) The first ship (#)
The image information of 1) is stored and held in the image memory circuit 65, the identification processing by the identification processing circuit 63, and the image display through the display device 40 are performed. ) Based on the amplitude / phase information
This is imaged through the image processing device 62, and based on the position information of the third ship (# 3), the third ship (# 3) is continuously irradiated with a radar beam, and the reflected light is reflected. The amplitude / phase information of a certain area is collected through the antenna device 50 and the transmission / reception device 20 (the time in FIG. 2).
t13 period).

(4) Based on the clear signal CR, the first
The image information on the second ship (# 1) is cleared from the image memory circuit 65, and the second
The image information of the third ship (# 2) is stored and held in the same image memory circuit 65, the identification processing by the identification processing circuit 63 and the image display through the display device 40 are performed, and the third information obtained above is obtained. Based on the amplitude / phase information of the fourth ship (# 3), it is imaged through the image processing device 62, and based on the position information of the fourth ship, the fourth
The radar ship is continuously irradiated with the radar ship and the amplitude / phase information of the reflected area is collected through the antenna device 50 and the transmission / reception device 20 (the time in FIG. 2).
t14 period).

(5) The process according to the above (4) is repeated until the amplitude / phase information on the N-th ship (#N) is collected, and the process on the N-th ship (#N) is repeated. When the amplitude / phase information is collected, the collected Nth
This is imaged through the image processing device 62 based on the amplitude / phase information of the #th ship (#N). In parallel with this, the sampling of the amplitude / phase information for the first ship (# 1) is started again (time t21 in FIG. 2).
Period).

As described above, the processes (1) to (5) are executed within the above-mentioned time T3 as one cycle of imaging and identification processing for the above-mentioned N ships by the apparatus of this embodiment. Yes, at this point in time T3, one type of imaging and identification of the N ships has been achieved.

In this embodiment, (1)
The processing of (5) to (5) is performed in one oscillation period T2 (2
By repeating within (0 to 30 seconds), the quality of the displayed image information (stored and held in the image memory circuit 65) is maintained, and the identification accuracy in the identification processing is maintained.

That is, as described above: ◆ Even if one ship is continuously imaged over the entire period corresponding to the wobble period of the ship, the change in the magnitude of the rotational motion of the same ship is Since the time required for imaging is very slow, there is no significant change in the quality of the obtained image.

For this reason, if the processing of the above (1) to (5) is maintained for a time T3 corresponding to one oscillation period of the ship, the inverse synthetic aperture used in such an environment is maintained. The condition for obtaining a high-quality image in the radar, that is, the condition for tracking and monitoring the target over the entire time corresponding to one oscillation period of the ship is satisfied in a pseudo manner.

Therefore, even with the image processing method according to this embodiment, images of these N ships can be obtained with a quality that is not much different from the image quality obtained by the conventional image processing method. .

As described above, according to the image processing method according to the present embodiment, as apparent from FIG.
(T1 and T2 respectively correspond to the above-mentioned times T1 and T2 in FIG. 2), a plurality of ships oscillating with a long period in time can be reduced in a very short time (1 / N compared to the conventional method). Image), and the ship type, ship name, etc. can be identified. Therefore,
If you want to capture and target more targets from a longer distance as described above and try to image and identify them, or if you want to minimize the power emission as much as possible to keep your position secret, Especially effective.

According to the above-described embodiment, the step of collecting amplitude / phase information, the step of imaging, and the step of identification (for the second and subsequent targets among the plurality of targets (ships)) Display) step, the imaging step for the target evaluated one immediately before, and the identification processing (display) step are each performed in parallel, so that the most efficient form in practical use is obtained. Although the imaging processing and the identification processing are performed for each of the above targets, the image processing method according to the present invention is not necessarily limited to such a method. In short, the process until all these targets are imaged, that is, the image acquisition cycle (time T3) of each target in FIG.
Is realized in a time-divisional manner at least in a cycle sufficiently shorter than the target oscillation cycle (time T2), thereby realizing efficient imaging and identification processing in a manner similar to the above. Can.

In the above embodiment, the signal processing circuit 6
0, the clear signal C from the target detection circuit 61
If the image memory circuit 65 is periodically cleared by R, but the image information stored and held in the image memory circuit 65 is overwritten by newly written image information every time, such target detection is performed. Circuit 6
The clear signal from 1 becomes unnecessary.

In the above-described embodiment, the electronic scanning antenna device 50 has a built-in high-frequency amplifier for transmission and reception. It is sufficient for the antenna device 50 to have only the phase shifter for phase control described above.

As the antenna device 50, any type of device may be employed as long as it can respond to the above-described beam distribution control by time division with high sensitivity. Not necessarily.

In the above embodiment, basically, a plurality of targets existing in the radar area are detected through the target detection circuit 61, and the position information is stored in the tracking memory circuit 64. Although the above-described image acquisition processing (processing that takes time T3) of each target is repeated within one shaking cycle of these targets based on the position information, the detection of the above targets and the detection of the detected targets It is also possible to store the position information in the tracking memory circuit 64 for each processing of the above-described image acquisition processing (processing that takes time T3) so as to see the movement amount of each of these target targets.

That is, each time the target position information is detected and stored in the tracking memory circuit 64,
The moving speed of each target can be estimated from the cycle time of the processing and the moving amount of each target within the same time, and the moving speed information of each target estimated in this way is stored in the image processing circuit 62. If you try to reflect on
For example, the configuration of the image processing circuit 62 having the configuration shown in FIG. 4 can be simplified.

The multi-target radar itself described here can be mounted on an unmanned flying vehicle.
That is, in such a case, the display device 40 is not necessarily required, and it is not necessary to determine the order of selection for display. In such a case, usually, the steering control of the flying object itself is performed based on the identified contents of the plurality of targets to be imaged.

[0053]

As described above, according to the present invention, position information for all of a plurality of targets is acquired collectively in advance, and amplitude / phase information for each target for which the position information has been acquired is collected. Performing the step of imaging the target based on the collected amplitude / phase information, and the step of identifying the target from the obtained target image based on the identification information. Since the repetition is performed in a short period in a time-division manner, it becomes possible to realize imaging of all of the plurality of target targets in a very short time. Moreover, if the tracking and monitoring of each of these targets is performed over the entire time corresponding to the fluctuation period of the target, an image having a quality that is not much different from the quality of a conventionally obtained image can be obtained. The target identification accuracy is also well maintained in each of the obtained images.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of an image processing apparatus for a multi-target radar according to the present invention.

FIG. 2 is a time chart schematically showing an image processing method of the multi-target radar according to the embodiment of the present invention, which is executed through the apparatus of the embodiment shown in FIG. 1;

FIG. 3 is a block diagram showing a configuration example of a conventional multi-target radar image processing apparatus.

FIG. 4 is a functional block diagram showing a general configuration of a circuit for imaging a video signal obtained through an inverse synthetic aperture radar.

FIG. 5 is a schematic diagram showing an example of displaying an imaged target on a display device.

FIG. 6 is a time chart schematically showing a conventional image processing method in a multi-target radar.

[Explanation of symbols]

 10, 50 antenna device 11, 51 control circuit 12, 52 antenna 20 transmission / reception device 30, 60 signal processing device 31, 61 target detection circuit 32, 62 image processing circuit 33, 63 identification processing circuit 40 display device 64 tracking memory circuit 65 image Memory circuit

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-4-262286 (JP, A) JP-A-6-167566 (JP, A) JP-A-4-190186 (JP, A) JP-A-6-167 160515 (JP, A) JP-A-1-227981 (JP, A) JP-A-6-167567 (JP, A) JP-A-8-29528 (JP, A) JP-A-59-27281 (JP, A) (58) Field surveyed (Int.Cl. ⁷ , DB name) G01S ⁷ /00-7/42 G01S 13/00-13/95

Claims (3)

(57) [Claims] 1. A video signal corresponding to a plurality of upsetting targets is acquired through an inverse synthetic aperture radar mounted on an air vehicle such as an aircraft, and each of the targets is imaged based on the acquired video signals. In the image processing method of a multi-target radar for identifying a target type or the like based on the identification information, position information on all of the plurality of targets is collectively acquired in advance based on the video signal, and the position information is acquired. (A) a first step of irradiating a radar beam based on position information and collecting its amplitude / phase information for each target, and (b) a step of imaging the same target based on the collected amplitude / phase information. The second step, (c) The third step of identifying a target from the obtained target image based on the identification information is repeated in a time-sharing manner at a period sufficiently shorter than the fluctuation period of the target. The image processing method of the multi-target radar, characterized in that the. 2. The method according to claim 1, wherein the first to third steps are performed for a target evaluated from a second one of the plurality of targets.
2. The image processing method for a multi-target radar according to claim 1, wherein the method is executed in parallel with the second and third steps for the target evaluated one before each. 3. A video signal corresponding to a plurality of upsetting targets is sampled through an inverse synthetic aperture radar mounted on an air vehicle such as an aircraft, and each of the targets is imaged based on the sampled video signals. And a multi-target radar image processing apparatus for identifying a target type or the like based on the identification information, a target position detecting means for detecting a position of each of the plurality of targets based on the video signal, A first memory unit in which the position information of the targets is collectively stored by the number of these targets, and based on the position information of each target stored in the first memory unit, the oscillation period of the targets is sufficiently shorter. Radar beam control means for controlling the distribution of the radar beam to each target in a period, and amplitude / phase information of a signal sequentially received in accordance with the radar beam control. Image processing means for imaging each corresponding target based on the identification information, identification processing means for identifying the target from the imaged target image based on the identification information, and identification processing for at least one target. And a second memory means for storing and holding the target image subjected to the identification processing. An image processing apparatus for a multi-target radar, comprising: