JP3395639B2 - ISAR signal processor - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ISAR signal processing device for processing a pulse (radar video) obtained by an inverse synthetic aperture radar (ISAR).

[0002]

2. Description of the Related Art Inverse synthetic aperture radar (hereinafter referred to as "ISA"
R ") is a change in the Doppler of a stationary or moving platform that transmits a pulse toward a target and receives the pulse reflected from the target (hereinafter," radar video "). The objective is to obtain the target image by compensating for the target fluctuation.
The ISAR is an ISAR signal transmitter that creates a pulse to be transmitted and an ISAR that receives and analyzes radar video reflected by a target and converts it into ISAR image information.
It is mainly composed of a signal processing device and an antenna for transmitting and receiving pulses.

FIG. 10 shows an ISA in the conventional ISAR.
It is a block diagram which shows an R signal processing apparatus. 101 in the figure
Is a receiving unit which is a receiving means. A pulse compression unit 102 is a pulse compression unit. Reference numeral 103 is a radar platform target movement compensation unit, 104 is a cross-range compression unit, 105 is a manual selection unit, and 106 is an amplitude detection unit. The radar platform target movement compensation unit 10
3, a cross-range compression unit 104, and a manual selection unit 105
And the amplitude detection section 106 constitute a pulse analysis means 107. Reference numeral 108 is a LOG which is an image information converting means.
It is a conversion unit. An image buffer unit 109 is provided.

Next, the processing operation of radar video in the conventional ISAR signal processing apparatus will be described. First,
The pulse transmitted from the ISAR signal transmitter collides with the target and is reflected, and is sent to the receiver 101 as a radar video through the antenna. Note that the ISAR signal transmitting device transmits an electric signal to the antenna at a predetermined constant cycle, and the antenna converts the electric signal into a pulse and transmits the pulse in a constant direction. The received radar video is sent to the pulse compression unit 102 and is compressed in the range direction because it is necessary to improve the resolution. The compression in the range direction is performed by software by correlating the transmitted pulse with the received radar video.

The range-compressed radar video is then sent to the radar platform target movement compensation unit 103, and the phase is compensated by the platform movement compensation amount and the target movement compensation amount. The platform movement compensation amount is determined by the position / speed of the platform measured by the navigation device mounted on the platform, and the target movement amount compensation amount is based on the radar video obtained by reflecting on the target. It is determined by the target distance / speed obtained from the time from the transmission of the pulse to the reception by extracting the one with strong amplitude.

The phase-compensated radar video is then sent to the cross-range compression section 104, and the observation time is cross-range compressed according to the observation time designation input from the manual selection device 105 to obtain the range. -It is converted into a radar video that is expressed in three dimensions: amplitude and Doppler. In addition,
The longer the observation time, that is, the longer the unit period for processing the received radar video is, the better the resolution will be.However, if it is too long, it will be difficult to obtain a clear image due to the effect of shaking. Need to set the time. In other words, if the fluctuation of the target is small, the observation time may be shortened,
On the contrary, if it is long, it is necessary to extend the observation time. Therefore,
In the manual selection unit 105, the observer manually sets the observation time while viewing the image.

The radar video, which has been subjected to the cross range compression, is sent to the amplitude detection section 106 to detect the amplitude. After that, the amplitude-detected radar video is transferred to the LOG converter 1
In 08, after the dynamic range is expanded by logarithmic conversion and converted into ISAR image information, the image buffer unit 10
9 and stored.

[0008]

In the conventional ISAR signal processing apparatus as described above, the radar video represented by the three-dimensional range, amplitude and Doppler after cross range compression and amplitude detection is Since it is converted into image information only by logarithmically converting it in the LOG converter 108 and expanding the dynamic range, clutter, noise, etc. are reflected as they are, and it is difficult to obtain a clear image for target recognition. There was a problem.

Further, when the cross-range compression is performed, the observer must determine the observing time by trial and error while observing the image, and there is a problem that the working time until the ISAR image information becomes long.

Furthermore, since there is no means for accurately measuring the moving direction and moving speed of the target, the ISAR signal transmitting device and the antenna have to keep the pulse transmitting cycle and the pulse transmitting direction in a predetermined state. , It was not possible to adjust to the optimum one according to the condition.

The present invention has been made to solve the above-mentioned problems, and a first object thereof is to receive a radar
The goal is to remove clutter and noise from the video and get a clearer image. The second purpose is to increase the processing speed until the ISAR image information is obtained by automatically selecting the optimum observation time. Also,
The third purpose is to detect the moving direction and moving speed of the target based on the information obtained in the ISAR signal processing process, and to adjust the pulse transmission cycle and the pulse transmission direction to the optimum ones. Is to

[0012]

ISA according to the present invention
In the R signal processing device, a receiving means for receiving the pulse reflected from the target, a pulse compressing means for compressing the pulse received by the receiving means, and a cross range by adjusting the phase of the pulse compressed by the pulse compressing means. Pulse analysis means for detecting the amplitude after compression in the direction and CFAR processing of the pulse compressed by the pulse compression means
The threshold is set by the pulse processed by the AR and the pulse whose amplitude is detected by the pulse analysis means, and the pulse extraction means for extracting only the pulse exceeding the threshold and the dynamic range of the pulse extracted by the pulse extraction means are expanded. And image information conversion means for converting into ISAR image information.

The receiving means for receiving the pulse reflected from the target, the pulse compressing means for compressing the pulse received by the receiving means, and the phase of the pulse compressed by the pulse compressing means are adjusted in the cross range direction. The pulse analysis means for detecting the amplitude after compression and the CFAR processing of the pulse compressed by the pulse compression means, and the first threshold is set by the CFAR processed pulse and the pulse whose amplitude is detected by the pulse analysis means. A first threshold setting means, a pulse histogram creating means for creating a composite histogram by creating a target area histogram and a non-target area histogram from pulses whose amplitudes have been detected by the pulse analyzing means, and a pulse histogram creating means A composite histogram created by
A second threshold is calculated from the first threshold set by the first threshold setting means, and a pulse extraction means for extracting only pulses exceeding the second threshold, and a dynamic range of the pulses extracted by the pulse extraction means Image information conversion means for enlarging and converting to ISAR image information.

Further, the image information converting means is adapted to expand the dynamic range of the pulse by using the histogram smoothing method and convert it into ISAR image information.

The receiving means for receiving the pulse reflected from the target, the pulse compressing means for compressing the pulse received by the receiving means, and the phase of the pulse compressed by the pulse compressing means are adjusted in the cross range direction. The pulse analysis means for detecting the amplitude after compression and the CFAR processing of the pulse compressed by the pulse compression means, and the first threshold is set by the CFAR processed pulse and the pulse whose amplitude is detected by the pulse analysis means. A first threshold setting means, a pulse histogram creating means for creating a target histogram and a non-target area histogram from the pulse whose amplitude is detected by the pulse analyzing means, and then synthesizing to create a synthetic histogram, and a pulse histogram creating The composite histogram and the first threshold created by Created by the second threshold setting means for setting the second threshold from the first threshold set by the threshold setting means, the second threshold set by the second threshold setting means and the pulse histogram creating means An image information conversion means for expanding the dynamic range from the composite histogram using the histogram smoothing method and converting it into ISAR image information is provided.

Further, a sea state estimating means for estimating the sea state by detecting the clutter intensity from the pulse compressed by the pulse compressing means, and a target moving direction and a moving direction of the target from the pulse obtained by the CFAR processing of the pulse compressed by the pulse compressing means The target movement detection means for detecting the movement speed, and the observation time control means for setting the observation time based on the movement direction and the movement speed of the target detected by the state and the target movement detection means estimated by the sea state estimation means are provided. I decided.

Further, the target movement detecting means detects the moving direction and moving speed of the target from the CFAR processed pulse and the target movement compensation amount of the target.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiment 1. 1 is a block diagram showing an ISAR signal processing apparatus according to Embodiment 1 of the present invention. In the figure, reference numeral 1 is a receiving unit which is a receiving means. Reference numeral 2 is a pulse compression unit which is a pulse compression means. 3 is a radar platform target movement compensation unit, 4 is a cross range compression unit, 5 is a manual selection unit,
Reference numeral 6 is an amplitude detector. The radar platform target movement compensation unit 3, the cross-range compression unit 4, the manual selection unit 5, and the amplitude detection unit 6 form a pulse analysis unit 7. Reference numeral 8 is a CFAR processing unit, 9 is a range spread estimation unit, 10 is a range spread comparison unit, 11 is a range spread detection unit, and 12 is a threshold excess amplitude extraction unit. It should be noted that the CFAR processing unit 8, the range spread estimating unit 9, the range spread comparing unit 10, the range spread detecting unit 11,
A pulse extraction unit 13 is configured with the threshold excess amplitude extraction unit 12. Reference numeral 14 is a LOG conversion unit which is an image information conversion unit. Reference numeral 15 is an image buffer unit.

Next, a radar video processing operation using this ISAR signal processing apparatus will be described. First,
The pulse transmitted from the ISAR signal transmitting device collides with the target and is reflected, and is transmitted to the receiving unit 1 through the antenna as radar video. It should be noted that the ISAR signal transmitting apparatus transmits a pulse toward the target at a constant cycle.
This radar video is sent to the pulse compressor 2 and is compressed in the range direction because it is necessary to improve the resolution. This compression in the range direction is performed by software by correlating the transmitted pulse with the received radar video.

The range-compressed radar video is then sent to the radar platform target movement compensator 3 where the phase is compensated by the platform movement compensation amount and the target movement compensation amount. The platform movement compensation amount is
Measured by the navigation device mounted on the platform, determined by the position and speed of the platform, and
The target movement compensation amount is determined by the target distance / speed obtained from the time from the transmission of the pulse to the reception of a pulsed video having a strong amplitude extracted from the radar video obtained by reflection on the target.

The phase-compensated radar video is then sent to the cross-range compressor 4 for manual selection 5
According to the observation time instruction input from, the observation time is cross-range compressed and converted into a radar video represented by three dimensions of range, amplitude, and Doppler. It should be noted that the longer the observation time, that is, the longer the unit period for processing the received radar video, the better the resolution, but if it is too long, it will be difficult to obtain a clear image due to the effect of shaking. It is necessary to set a different observation time. That is, if the fluctuation of the target is small, the observation time may be short, and conversely, if it is long, the observation time needs to be long. Therefore, in the manual selection unit 5, the observer manually determines the observation time while viewing the image.

The radar video, which has been subjected to the cross range compression, is sent to the amplitude detection section 6 and its amplitude is detected. The radar video whose amplitude has been detected is sent to the threshold excess amplitude extraction unit 12. Threshold excess amplitude extraction unit 1
In No. 2, first, the threshold is set at a low amplitude level, and only the radar video that exceeds the threshold is extracted and sent to the range spread detector 11. Range spread detector 1
In 1, the spread in the range direction of the radar video exceeding the threshold is detected, and the spread information in the range direction is sent to the range spread comparison unit 10.

In parallel with this, the CFAR processing unit 8
Then, the radar video that has been range-compressed by the pulse compression unit 2 is subjected to CFAR processing in the range direction. Note that the CFAR processing is performed by dividing an input radar video into a plurality of cells in the range direction, and a cell including a target (referred to as “target cell”) and a plurality of cells before and after the target cell (“reference cell”).
Is called) and a threshold value is obtained from the reference cell, and only radar video exceeding this threshold value is extracted.

The spread in the range direction of the radar video extracted by the CFAR processing unit 8 is estimated by the range spread estimating unit 9, and the spread information in the range direction is sent to the range spread comparing unit 10.

The range spread comparison unit 10 compares the range spread sent from the range spread estimation unit 9 with the range spread sent from the range spread detection unit 11, and the result is the threshold excess amplitude extraction unit. Sent to 12.

In the threshold excess amplitude extraction section 12,
If the result is that the spreads in both range directions do not match, the amplitude with a higher level than that of the previous time is set as the threshold again, and only radar video that exceeds that is extracted and sent to the range spread detection unit 11. ,Later,
A similar operation is performed to determine if the range spreads match. On the contrary, when the result that the spreads in both range directions match is obtained, the threshold is fixed,
Only pulses that exceed the threshold are sent to the LOG converter 14.

In the LOG converter 14, the radar
The video is converted into ISAR image information by expanding the dynamic range by logarithmic conversion.
It is sent to and stored in the image buffer unit 15.

Thus, the radar video compressed in the range direction is subjected to CFAR processing, and only if the spread in the range direction of the radar video after amplitude detection in which the threshold is exceeded matches the spread in the range direction. LOG conversion of radar video exceeding
Since the SAR image information is obtained, clutter and noise can be eliminated, and a clearer image can be obtained.

Embodiment 2. 2 is a block diagram showing an ISAR signal processing apparatus according to Embodiment 2 of the present invention, and Embodiment 1 of FIG.
In the ISAR signal processing device in the above, the radar video compressed in the range direction by the pulse compression unit 2 is CFAR.
After processing, radar platform target movement compensation unit 3
It was designed to be sent to. In the figure, 16 is a CFAR processing unit which is a CFAR processing means.

In such a configuration, the radar video compressed in the range direction by the pulse compression unit 2 is CFA.
The CF processing is performed by the R processing unit 16 to remove clutter and noise, and thereafter the clutter and noise are sent to the radar platform target movement compensation unit 3. Therefore, a clear image without clutter and noise is obtained, and the radar platform target movement is obtained. Radar that is processed by the movement compensation unit 3 and later
The amount of video information can be reduced, and the processing speed up to ISAR image information can be increased.

Embodiment 3. FIG. 3 is a block diagram showing an ISAR signal processing device according to a third embodiment of the present invention. In the ISAR signal processing device according to the first embodiment shown in FIG. 1, a threshold is further set for fine adjustment. Is.

In the figure, numeral 17 is a video cutout section, 18 is a target area histogram preparation section, 19 is a non-target area histogram preparation section, and 20 is a histogram composition section. In addition,
The video cutout unit 17, the target area histogram creating unit 18, the non-target area histogram creating unit 19, and the histogram synthesizing unit 20 make up the pulse histogram creating unit 2
Make up one. 22 is a threshold 2 creating section, 2
Reference numeral 3 is a threshold 2 excess amplitude extraction unit. It should be noted that the threshold 2 creating unit 22 and the threshold 2 excess amplitude extracting unit 23 constitute a pulse extracting means 24. Reference numeral 25 is a threshold 1 setting unit. Note that C
The FAR processing unit 8, the range spread estimating unit 9, the range spread comparing unit 10, the range spread detecting unit 11, and the threshold 1 setting unit 25 constitute a first threshold setting unit 26. It should be noted that unlike the threshold excess amplitude extraction unit 12 in the first embodiment shown in FIG. 1, the threshold 1 setting unit 25 does not perform operation of extracting radar video having an amplitude exceeding the threshold even if the threshold is determined. , Just threshold 2
Only the information on the threshold 1 is sent to the creation unit 22.

Next, a radar video processing operation using this ISAR signal processing apparatus will be described. The radar video amplitude-detected by the amplitude detector 6 is sent to the video clipper 17. The video clipping unit 17 determines whether the radar video is a target area or a non-target area based on the tracking information, and the video of the target area and the video of the non-target area are equal in area from both areas. The video of the target area is sent to the target area histogram creation unit 18, and the video of the non-target area is sent to the non-target area histogram creation unit 19. In the non-target area, only radar video due to clutter and noise exists, and in the target area, radar video due to target, clutter and noise exists.

The target area histogram creating section 18 and the non-target area histogram creating section 19 create a histogram by designating the amplitude on the horizontal axis and the frequency on the vertical axis. Figure 4
4A is a histogram of the target area created by the target area histogram creating unit 18, and FIG. 4B is a histogram of the non-target area created by the non-target area histogram creating unit 19. Note that the radar video histogram consisting of clutter and noise is generally supposed to follow the Weibull distribution, so the histogram in the non-target area has one mountain as shown in FIG. The histogram of the target area is shown in FIG.
As shown in the figure, mountains due to clutter and noise and mountains due to the target appear.

Next, the histogram of the target area created by the target area histogram creating section 18 and the histogram of the non-target area created by the non-target area histogram creating section 19 are sent to the histogram combining section 20 and combined. ,
A composite histogram is created. FIG. 4C is a composite histogram. As can be seen from FIG. 4 (c), the peaks due to clutter and noise are emphasized by combining. This composite histogram is sent to the threshold 2 creation unit 22 and the threshold 1 setting unit 2
In the vicinity of the threshold 1 determined in step 5, the amplitude having the minimum frequency in the valley portion of the combined histogram is determined as the threshold 2, and this value is sent to the threshold 2 excess amplitude extraction unit 23.

The threshold 2 excess amplitude extraction unit 23 extracts only the pulses exceeding the threshold 2 from the radar video sent from the amplitude detection unit 6 and whose amplitude is detected, and sends them to the LOG conversion unit 14. LOG converter 14
Then, the dynamic range is expanded by logarithmic conversion and converted into ISAR image information. After that, the ISAR image information is sent to and stored in the image buffer unit 15.

Thus, in the vicinity of the threshold 1,
Clutter and noise are removed at a finer level by setting a threshold value to a value that has the lowest frequency in the valley portion of the combined histogram and extracting and processing a radar video having an amplitude exceeding the threshold value 2. As a result, a clearer image can be obtained, and of the radar video obtained by reflecting on the target, those with low amplitude are deleted as clutter and noise, which makes it impossible to obtain a complete image. You can avoid the danger.

Fourth Embodiment FIG. 5 is a block diagram showing an ISAR signal processing apparatus according to Embodiment 4 of the present invention, and Embodiment 3 of FIG.
In the ISAR signal processing device in 1), the histogram smoothing method is used instead of the LOG conversion to convert to ISAR image information.

In the figure, reference numeral 27 is a threshold 2 creating section which is a second threshold setting means. 28
Is a histogram smoothing unit which is an image information converting unit. Next, the operation will be described. The threshold 2 creating unit 27 determines the threshold 2 from the combined histogram sent from the histogram combining unit 20 and the threshold 1 sent from the threshold 1 setting unit 25, and the information on the combined histogram and the threshold 2 is obtained from the histogram smoothing unit 28. Send to.

FIG. 6 is a conceptual diagram showing the processing in the histogram smoothing unit 28 using the histogram smoothing method.
In the histogram smoothing unit 28, first, the portion exceeding the threshold 2 is separated from the combined histogram, and the histogram shown in FIG.
Create a histogram as shown in. Next, in the histogram after separation, as shown in FIG. 6B, a plurality of adjacent amplitudes are collected so that the average of their frequencies becomes flat, and the amplitudes are changed to brightness, thereby changing the dynamic range. Enlarge and convert to ISAR image information. After that, the ISAR image information is stored in the image buffer unit 15.

As a result, the histogram synthesized by the histogram synthesizer 20 is used to expand the dynamic range by the histogram smoothing method in the histogram smoother 28 to obtain ISAR image information. The processing speed can be increased as compared with the case where the sent radar video is LOG-converted to generate ISAR image information.

The histogram smoothing method is used for expanding the dynamic range, and even if it is not particularly this embodiment, in the first embodiment or the conventional example, instead of the LOG conversion, amplitude detection is performed. It is also possible to create a histogram from the generated lator video and use the histogram smoothing method to expand the dynamic range.

Fifth Embodiment FIG. 7 is a block diagram showing an ISAR signal processing device according to the fifth embodiment of the present invention.
In the ISAR signal processing device, the observation time is automatically set instead of manually selecting the observation time. In the figure, 29 is a target detection unit, and 30 is a tracking processing unit. The target detection unit 29 and the tracking processing unit 30 constitute a target movement detection unit 31. 32
Is a clutter intensity recognition unit, and 33 is a sea state estimation unit. The clutter strength recognition unit 32 and the sea state estimation unit 33 constitute sea state estimation means 34. An observation time control unit 35 is an observation time control means.

Next, in this configuration, the operation for obtaining an image with a ship moving on the sea as a target will be described. First, the radar video compressed in the range direction by the pulse compression unit 2 is the platform target movement compensation unit 3,
At the same time as being sent to the CFAR processing unit 8, it is also sent to the clutter strength recognition unit 32. In the clutter strength recognition unit 32,
Recognize the clutter intensity by averaging the amplitude around the target.
The intensity of this clutter is sent to the sea state estimation unit 33, and the sea state is calculated using the radar equation.
This sea state information is sent to the observation time control unit 35.

In parallel, the CFAR processing unit 8
The FAR-processed radar video is sent to the range spread estimation unit 9 and also to the target detection unit 29. The target detection unit 29 identifies the position of the target based on the CFAR-processed radar video, and the tracking processing unit 30.
Send to. The tracking processing unit 30 obtains the moving direction and moving speed of the target based on the positional information of the target sent from the target detecting unit 29, and sends the moving direction and moving speed of the target to the observation time control unit 35.

The observation time control unit 35 determines the observation time from the sea state and the moving direction and moving speed of the target. Generally, the sway of a ship is determined by the sea state, the moving direction and moving speed of the target, and for example, the sway of the ship increases as the sea state increases.
The sway of a ship also changes depending on whether the ship is stationary or moving, and whether it travels parallel or vertically to the direction of wave travel. In the observation time control unit 35, the past sea state,
It has a relationship diagram showing the correlation between the moving direction and moving speed of the target and the optimum observation time set manually at that time, and based on this, the observation time is calculated from the sea state and the moving direction and moving speed of the target. To decide.

The observation time determined by the observation time control section 35 is sent to the cross range compression section 4, and thereafter, the same processing as in the first embodiment is performed to obtain ISAR image information.

As described above, the ISAR receiving and processing apparatus obtains the ISAR image information because it obtains the motion of the ship from the received radar video and automatically sets the optimum observation time without human intervention. Therefore, the processing speed can be increased.

Sixth Embodiment FIG. 8 is a block diagram showing an ISAR signal processing apparatus according to Embodiment 5 of the present invention, and FIG.
In the ISAR signal processing device, the tracking processing unit is linked to the radar platform target movement compensation unit. In the figure, 36 is a tracking processing unit. The target detection unit 29 and the tracking processing unit 36 form a target movement detection unit 31.

In the tracking processing section 36, not only the position information of the target detected by the target detecting section 29 but also the target movement compensation amount is sent from the radar platform target movement compensating section 3 and the information is complemented with each other. Measure the target speed.

As described above, since the tracking processing unit 36 obtains the target moving direction and moving speed while complementing the target moving compensation amount, it is necessary to detect more accurate values of the target moving direction and moving speed. It is possible to set a more optimal observation time.

Embodiment 7. FIG. 9 is a block diagram showing an ISAR signal processing apparatus according to Embodiment 7 of the present invention. Embodiment 1 of FIG.
In this ISAR signal processing device, the target can be tracked and the moving direction and moving speed of the target can be detected from the CFAR-processed radar video.

In the figure, 37 is a CFAR processing unit, 38 is a target detecting unit, and 39 is a tracking processing unit. The CFAR processing unit 37, the target detection unit 38, and the tracking processing unit 39 constitute the target tracking information detection means 40.

Next, the operation will be described. The radar video received by the receiver 1 is sent to the pulse compressor 2 and is compressed in the range direction because it is necessary to improve the resolution. This compression in the range direction is performed by software by correlating the transmitted pulse with the received radar video.

The range-compressed radar video is then processed by the radar platform target movement compensator 3 and CFA.
It is sent to the R processing unit 37. The CFAR processing unit 37 performs CFAR processing on the radar video that has been range-compressed by the pulse compression unit 2 in the range direction, and sends the radar video after CFAR processing to the target detection unit 38. In the target detection unit 38, C
The target position is specified based on the FAR-processed radar video and sent to the tracking processing unit 39. In parallel with this, in the radar platform target movement compensation unit 3, the target movement compensation amount of the target is detected and sent to the tracking processing unit 39.

The tracking processing section 39 calculates the moving direction and moving speed of the target from the position information of the target and the target movement compensation amount of the target.

The moving direction and moving speed of this target are I
It is sent to the SAR signal transmitter and the antenna. In the ISAR signal transmitter and the antenna, the pulse emission interval and the pulse emission direction can be controlled by the moving direction and moving speed of the target. The control is performed by the observer by manually changing the setting each time.

Thus, from the ISAR signal processing device,
By obtaining a more accurate target movement direction and movement speed, the ISAR signal transmitter and antenna can adjust the pulse transmission cycle and pulse transmission direction so that the target can always be captured, and clear image information can be obtained. It is possible to perform the optimum control to obtain it.

[0059]

In the ISAR signal processing device according to the present invention, the receiving means for receiving the pulse reflected from the target, the pulse compressing means for compressing the pulse received by the receiving means, and the pulse compressing means for compressing the pulse. Pulse analysis means for adjusting the phase of the pulse and compressing it in the cross-range direction and then detecting the amplitude, and CFAR processing the pulse compressed by the pulse compression means, and the amplitude is detected by the CFAR processed pulse and the pulse analysis means. And a pulse extraction means for setting only a threshold value of the pulse that exceeds the threshold value, and an image information conversion means for expanding the dynamic range of the pulse extracted by the pulse extraction means and converting it into ISAR image information. I made it.

Accordingly, the radar video compressed in the range direction is subjected to CFAR processing, and the threshold value is detected only when the spread in the range direction of the radar video after amplitude detection in which the threshold value exceeds the threshold value matches the spread in the range direction. Converts radar video exceeding LOG to LOG
Since the AR image information is obtained, clutter and noise can be eliminated and a clearer image can be obtained.

Further, receiving means for receiving the pulse reflected from the target, pulse compressing means for compressing the pulse received by the receiving means, and CFAR processing means for CFAR processing the pulse compressed by the pulse compressing means, CF
ISAR image information by expanding the dynamic range of the pulse whose amplitude has been detected by the pulse analyzing means and the pulse analyzing means which adjusts the phase of the CFAR processed pulse by the AR processing means and compresses it in the cross range direction. And image information conversion means for converting into

Thus, the radar video compressed in the range direction by the pulse compression unit is processed by the CFA processing unit by the CFA processing unit.
The R processing removes the clutter and noise and then sends it to the radar platform target movement compensator, so that a clear image without clutter and noise can be obtained and the amount of information of the radar video to be image processed. Can be reduced, and the processing speed up to ISAR image information can be increased.

The receiving means for receiving the pulse reflected from the target, the pulse compressing means for compressing the pulse received by the receiving means, and the phase of the pulse compressed by the pulse compressing means are adjusted in the cross range direction. The pulse analysis means for detecting the amplitude after compression and the CFAR processing of the pulse compressed by the pulse compression means, and the first threshold is set by the CFAR processed pulse and the pulse whose amplitude is detected by the pulse analysis means. A first threshold setting means, a pulse histogram creating means for creating a composite histogram by creating a target area histogram and a non-target area histogram from pulses whose amplitudes have been detected by the pulse analyzing means, and a pulse histogram creating means A composite histogram created by
A second threshold is calculated from the first threshold set by the first threshold setting means, and a pulse extraction means for extracting only pulses exceeding the second threshold, and a dynamic range of the pulses extracted by the pulse extraction means Image information conversion means for enlarging and converting to ISAR image information.

As a result, in the vicinity of the threshold 1,
The threshold value is the lowest frequency in the post-synthesis histogram, and radar video with an amplitude exceeding it can be extracted and processed, and the clutter and noise can be removed at a finer level. As a result, a clearer image can be obtained, and of the radar video obtained by reflecting on the target, those with low amplitude are deleted as clutter and noise, which makes it impossible to obtain a complete image. You can avoid the danger.

Further, the image information converting means is adapted to expand the dynamic range of the pulse by using the histogram smoothing method and convert it into ISAR image information.

The receiving means for receiving the pulse reflected from the target, the pulse compressing means for compressing the pulse received by the receiving means, and the phase of the pulse compressed by the pulse compressing means are adjusted in the cross range direction. The pulse analysis means for detecting the amplitude after compression and the CFAR processing for the pulse compressed by the pulse compression means, and the first threshold is set by the CFAR processed pulse and the pulse whose amplitude is detected by the pulse analysis means. First threshold setting means, pulse histogram creation means for creating a target area histogram and non-target area histogram from the pulses whose amplitudes have been detected by the pulse analysis means, and then creating a composite histogram, and pulse histogram creation means The composite histogram and the first threshold created by Created by the second threshold setting means for setting the second threshold from the first threshold set by the threshold setting means, the second threshold set by the second threshold setting means and the pulse histogram creating means An image information conversion means for expanding the dynamic range from the composite histogram using the histogram smoothing method and converting it into ISAR image information is provided.

As a result, the processing speed can be increased as compared with the case where the radar video sent from the amplitude detector is LOG-converted to create ISAR image information.

Further, the sea state estimating means for detecting the clutter strength from the pulse compressed by the pulse compressing means and estimating the sea state, and the target moving direction from the pulse obtained by the CFAR processing of the pulse compressed by the pulse compressing means, The target movement detection means for detecting the movement speed, and the observation time control means for setting the observation time based on the movement direction and the movement speed of the target detected by the state and the target movement detection means estimated by the sea state estimation means are provided. I decided.

As a result, the motion of the ship is obtained from the received radar video, and the optimum observation time is automatically set without human intervention, so the processing speed for obtaining ISAR image information is increased. be able to.

Further, the target movement detecting means detects the moving direction and moving speed of the target from the pulse subjected to the CFAR processing and the target movement compensation amount of the target.

As a result, the target moving direction and moving speed can be calculated while being supplemented by the target moving compensation amount, so that a more accurate moving direction and moving speed value can be detected, and a more optimal observation time can be obtained. Can be set.

The receiving means for receiving the pulse reflected from the target, the pulse compressing means for compressing the pulse received by the receiving means, and the phase of the pulse compressed by the pulse compressing means are adjusted in the cross range direction. After the compression, the amplitude is detected, and the pulse analysis means for calculating the target movement compensation amount of the target and the dynamic range of the pulse whose amplitude has been detected by the pulse analysis means are expanded.
Image information converting means for converting to AR image information, and CFAR processing of the pulse compressed by the pulse compressing means, and CF
A target tracking means for detecting the target moving direction and moving speed from the AR-processed pulse and the target moving compensation amount is provided.

As a result, a more accurate moving direction and moving speed of the target can be obtained, and the ISAR signal processing device and the antenna adjust the pulse transmitting cycle and the pulse transmitting direction so that the target can always be captured. It is possible to perform optimal control for obtaining clear image information.

[Brief description of drawings]

FIG. 1 is a block diagram of an ISAR signal processing device according to a first embodiment.

FIG. 2 is a block diagram of an ISAR signal processing device according to a second embodiment.

FIG. 3 is a block diagram of an ISAR signal processing device according to a third embodiment.

FIG. 4 is a histogram created by a target area histogram creation unit, a non-target area histogram creation unit, and a histogram composition unit according to the third embodiment.

FIG. 5 is a block diagram of an ISAR signal processing device according to a fourth embodiment.

FIG. 6 is a conceptual diagram showing a histogram smoothing method.

FIG. 7 is a block diagram of an ISAR signal processing device according to a fifth embodiment.

FIG. 8 is a block diagram of an ISAR signal processing device according to a sixth embodiment.

FIG. 9 is a block diagram of an ISAR signal processing device according to a seventh embodiment.

FIG. 10 is a block diagram of a conventional ISAR signal processing device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 receiving part (reception means), 2 pulse compression part (pulse compression means), 7 pulse analysis means, 13 pulse extraction means, 14 LOG conversion means (image information conversion means), 16 CFAR processing means, 21 pulse histogram creation means, 24 pulse extracting means, 26 first threshold setting means, 28 histogram smoothing section (image information converting means), 31 target movement detecting means, 34 sea state estimating means, 35 observation time controlling means, 40 target tracking means

Claims (6)

(57) [Claims] 1. A receiving means for receiving a pulse reflected from a target, a pulse compressing means for compressing the pulse received by the receiving means, and a cross range by adjusting the phase of the pulse compressed by the pulse compressing means. The pulse analysis means for detecting the amplitude after compression in the direction and the pulse compressed by the pulse compression means are subjected to CFAR processing, and the threshold is detected between the pulse subjected to the CFAR processing and the pulse whose amplitude is detected by the pulse analysis means. Set,
I, which comprises pulse extraction means for extracting only pulses exceeding the threshold, and image information conversion means for expanding the dynamic range of the pulses extracted by the pulse extraction means and converting them into ISAR image information.
SAR signal processing device. 2. A receiving means for receiving a pulse reflected from a target, a pulse compressing means for compressing the pulse received by the receiving means, and a cross range by adjusting the phase of the pulse compressed by the pulse compressing means. A pulse analyzing means for detecting the amplitude after compressing in the direction, and a CFAR processing for the pulse compressed by the pulse compressing means, and the pulse subjected to the CFAR processing and the pulse whose amplitude is detected by the pulse analyzing means. First threshold setting means for setting the threshold of, and a pulse histogram creating means for creating a composite histogram after creating a target area histogram and a non-target area histogram from the pulse whose amplitude is detected by the pulse analysis means And a composite histogram created by the pulse histogram creating means. And a pulse extraction means for calculating a second threshold from the first threshold set by the first threshold setting means, and extracting only pulses exceeding the second threshold, and the pulse extraction means. Image information conversion means for expanding the dynamic range of the generated pulse and converting it to ISAR image information. 3. The image information conversion means expands the dynamic range of the pulse by using a histogram smoothing method to obtain I
Claim and converting the SAR image information 1 or
Or the ISAR signal processing device according to item 2 . 4. A receiving means for receiving a pulse reflected from a target, a pulse compressing means for compressing the pulse received by the receiving means, and a cross range by adjusting the phase of the pulse compressed by the pulse compressing means. A pulse analyzing means for detecting the amplitude after compressing in the direction, and a CFAR processing for the pulse compressed by the pulse compressing means, and a pulse for which the CFAR processing is performed and a pulse whose amplitude is detected by the pulse analyzing means. First threshold setting means for setting the threshold of, and a pulse histogram creation to create a composite histogram after creating a target area histogram and a non-target area histogram from the pulse whose amplitude is detected by the pulse analysis means And a composite hist created by the pulse histogram creating means. Gram and a second threshold setting means for setting a second threshold from the first threshold set by the first threshold setting means, a second threshold set by the second threshold setting means and the An ISAR signal processing device, comprising: an image information conversion unit that expands a dynamic range from a composite histogram created by the pulse histogram creation unit by using a histogram smoothing method and converts it into ISAR image information. 5. A target moving direction from a sea state estimating means for detecting a clutter strength from a pulse compressed by the pulse compressing means and estimating a sea state, and a pulse obtained by CFAR processing the pulse compressed by the pulse compressing means. And a target movement detection means for detecting a movement speed, an observation time control means for setting an observation time based on the state of movement estimated by the sea state estimation means and the movement direction and movement speed of the target detected by the target movement detection means. The ISAR signal processing device according to any one of claims 1 to 4, further comprising: 6. The ISAR signal processing apparatus according to claim 5 , wherein the target movement detecting means detects the movement direction and movement speed of the target from the CFAR processed pulse and the target movement compensation amount of the target.