JP3519360B2 - ISAR signal 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 an ISAR signal processing method and apparatus for applying a transmitted wave to a target, receiving the reflected wave, and outputting the physical shape of the target as an image.

[0002]

2. Description of the Related Art FIG. 6 is a block diagram of a conventional ISAR signal processing system and a data image used for the processing. In the figure, 1 is a distance compensation processing unit, 2 is an isolated point calculation processing unit, 3 is a phase compensation processing unit, 4 is an FFT processing unit, and 5 is an amplitude detection processing unit.

Next, the operation will be described. When the observation data which is the reflected wave from the target is input, the distance compensation processing unit 1 compensates for the change in the relative distance between the radar and the target.
Next, when the phase compensation processing is performed in the isolated point calculation processing unit 2, a reference point (hereinafter referred to as an isolated point) is calculated, and the phase compensation processing unit 3 calculates a relative distance change between the radar and the target. Phase compensation processing is performed to compensate for the Doppler frequency change component caused by.

At this stage, since the received signal contains only the component in which the target itself is swaying, the FFT is performed.
An ISAR image can be obtained by performing FFT processing in the processing unit 4, extracting a target fluctuation component, and performing amplitude detection in the amplitude detection processing unit 5.

As shown in the data image used in the process of FIG. 6, all of these processes are performed on the data corresponding to the synthetic aperture time necessary to form one image, and finally 1 Form a sheet of ISAR image.

[0006]

In the conventional ISAR processing method, in order to form one image, all the data for the required synthetic aperture time is processed in the processing units 1 to 5 in FIG. Was. That is, 1 in 1 synthetic aperture time
In order to form one image, data processing for one synthetic aperture time is performed, and in order to form one image in two synthetic aperture time, data processing for two synthetic aperture time is performed. Therefore, there is a problem in that hardware resources are required for the required data. In addition, the isolated point can be calculated only every fixed period, and if the optimum isolated point cannot be selected, there is a problem that the ISAR image spreads in the Doppler direction.

The present invention has been made in order to solve the above-mentioned problems, and a hardware resource is formed by forming one ISAR image only by data processing for a required synthetic aperture time or less. It is an object of the present invention to provide an ISAR signal processing method and apparatus capable of making the ISAR image small in size and constant, and adaptively selecting isolated points to form an ISAR image that does not spread in the Doppler direction. .

[0008]

I according to the invention of claim 1
The SAR signal processing method is an ISAR signal processing method in which a transmitted wave is applied to a target, the reflected wave is received, and the physical shape of the target is output as an image. The first method is to compensate the relative distance between the radar device and the target. And a second step of calculating a reference point when performing the phase compensation process,
A third step of compensating for a change component of the Doppler frequency caused by a change in the relative distance between the radar device and the target; a fourth step of performing an FFT process; and a fifth step of performing amplitude detection, From the first step to the third step , the processing is performed on the data less than the synthetic aperture time required to form one image,
One screen is formed by accumulating the processed data in the fourth step.

The ISAR signal processing method according to a second aspect of the present invention is the method of the first aspect, wherein after the phase compensation of the third step, the data for a plurality of pulses is integrated according to the synthetic aperture time. Is.

An ISAR signal processing method according to a third aspect of the present invention is the method according to the first or second aspect of the invention, in which the spread in the Doppler direction of the data after the FFT processing of the fourth step is measured, and the result is measured by the second method. It gives feedback to the step.

An ISAR signal processing method according to a fourth aspect of the present invention is the simple FF according to the first or second aspect of the invention, in which the number of data is thinned out before the FFT processing of the fourth step.
T is measured, its spread is measured, and the result is fed back to the second step.

In the ISAR signal processing method according to the invention of claim 5, in the invention according to any one of claims 1 to 4, when performing the processing of the second step, some candidates are selected and all of them are selected. Phase compensation and FFT processing are performed on the candidates, the spread in the Doppler direction is measured, and an ISAR image judged to have the smallest spread in the Doppler direction is output.

According to a sixth aspect of the present invention, there is provided an ISAR signal processing device, wherein an ISAR signal processing device receives a transmitted wave as a target, receives the reflected wave, and outputs the physical shape of the target as an image, which is a radar device. The synthetic aperture time required to form one image related to the relative distance of the target is not enough.
A distance compensating means for compensating the full data, an isolated point calculating means for calculating a reference point when performing the phase compensating processing based on the output of the distance compensating means, and an output of the isolated point calculating means. On the basis of the phase compensating means for compensating the change component of the Doppler frequency caused by the change in the relative distance between the radar device and the target, the output of the phase compensating means is sequentially accumulated, and all the accumulated one synthetic aperture time is stored. It is provided with FFT means for performing FFT processing on data and amplitude detection means for performing amplitude detection on the output of the FFT means.

An ISAR signal processing device according to a seventh aspect of the present invention is the ISAR signal processing device according to the sixth aspect, further comprising presum processing means for integrating data of a plurality of pulses according to the synthetic aperture time after phase compensation. Is.

The ISAR signal processing device according to the invention of claim 8 is the invention of claim 6 or 7, wherein the spread in the Doppler direction of the FFT processed data is measured, and the result is fed back to the isolated point calculating means. It is provided with a Doppler direction spread measuring means.

An ISAR signal processing device according to a ninth aspect of the present invention is the simple FFT device according to the sixth or seventh aspect of the invention, which performs a simple FFT by thinning out the number of data before the FFT processing.
The FT means and the Doppler direction spread measuring means for measuring the spread in the Doppler direction of the data thinned out based on the output of the simple FFT means and feeding back the result to the isolated point calculating means are provided.

According to a tenth aspect of the present invention, there is provided an ISAR signal processing device, wherein a transmitted wave is applied to a target, the reflected wave is received, and the physical shape of the target is output as an image. Synthetic aperture time required to form one image related to the target relative distance
Distance compensating means for compensating the data less than ,
Based on the output of the distance compensating means, an isolated point calculating means for calculating a reference point when performing phase compensation processing, and some candidates are selected when performing the isolated point calculation, and the phase for all the candidates is selected. A plurality of phase compensation means for performing compensation,
A plurality of FFT means for performing FFT processing on each output of the phase compensating means, a plurality of Doppler direction spread measuring means for measuring spread in the Doppler direction based on each output of the FFT means, and the Doppler direction spread measurement Image determination means for outputting the ISAR image determined to have the smallest spread in the Doppler direction based on each output of the means.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below.
It will be described with reference to the drawings. Embodiment 1. 1 is a block diagram of an ISAR signal processing system according to Embodiment 1 of the present invention and a diagram showing a data image to be processed. In addition, in FIG.
Parts corresponding to those in FIG. 6 are designated by the same reference numerals, and detailed description thereof will be omitted. In the figure, 1A is a distance compensation processing unit as a distance compensating means for compensating for a relative distance change between a radar device and a target, and 2A is an isolated point calculating means as an isolated point calculating means for calculating an isolated point when performing phase compensation processing. The processing unit 3A is a phase compensation processing unit as a phase compensation unit that compensates a change component of the Doppler frequency caused by a change in the relative distance between the radar device and the target, and 4A is an FFT processing unit as an FFT unit that performs the FFT process.

Next, the operation will be described. here,
As an example, one ISAR image is formed in one synthetic aperture time, and it is assumed that the data to be processed is 1/3 of one synthetic aperture time, and the data amount corresponding to that is N pulses. To do. When the observation data is input, first, the distance compensation processing unit 1A performs distance compensation for N pulses, and the oldest N pulse data is used as the isolated point calculation processing unit 2.
Send to A. After the isolated point calculation processing unit 2A calculates the isolated point, the oldest N pulse data is transmitted to the phase compensation processing unit 3A to perform the phase compensation, and the oldest N pulse is also sent to the FFT processing unit 4A. Send.

The FFT processing section 4A sequentially accumulates the transmitted data, performs FFT in the pulse direction on all the data for one synthetic aperture time, and transmits the result to the amplitude detection processing section 5. . The amplitude detection processing unit 5 also performs amplitude detection on all data for one synthetic aperture time to form an ISAR image.

As described above, in this embodiment, the distance compensation is performed.
In the processing from the processing unit to the phase compensation processing unit, one image
Data less than the synthetic aperture time required to form
By performing the processing, the data processing amount is always N pulses, so that the data to be processed is smaller than the conventional one, and therefore the hardware resource can be made small and constant.

Embodiment 2. 2 is a block diagram of an ISAR signal processing system according to the second embodiment of the present invention and a diagram showing a data image to be processed. 2, parts corresponding to those in FIG. 1 are designated by the same reference numerals, and detailed description thereof will be omitted. In the present embodiment, the presum processing means for performing integration of a plurality of pulses of data between the phase compensation processing unit 3A and the FFT processing unit 4A according to the synthetic aperture time after phase compensation in the first embodiment. The presum processing unit 21 is added. Other configurations are similar to those in FIG.

Next, the operation will be described. The presum processing unit 21 performs presum processing according to the synthetic aperture time. For example, when one synthetic aperture time is used as a reference, when it is desired to form one ISAR image in two synthetic aperture times, integration is performed in the pulse direction so that the number of data is the same as one synthetic aperture time. Other operations are the same as those in the case of FIG. 1, and thus the description thereof will be omitted.

As described above, in the present embodiment, by performing the presum processing, even in the FFT processing section and thereafter,
Only the amount of data corresponding to the reference synthetic aperture time needs to be processed, and the hardware resources can be made small and constant.

Embodiment 3. FIG. 3 is a block diagram of an ISAR signal processing system according to the third embodiment of the present invention. 3, parts corresponding to those in FIG. 1 are designated by the same reference numerals, and detailed description thereof will be omitted. In the present embodiment, in the first embodiment, the spread in the Doppler direction of the FFT processed data is measured between the FFT processing unit 4A and the isolated point calculation processing unit 2A, and the result is measured as the isolated point calculation processing unit 2A. The Doppler-direction spread measuring unit 31 is added as a Doppler-direction spread measuring means for feeding back to. Other configurations are similar to those in FIG.

Next, the operation will be described. In the Doppler direction spread measurement unit 31, FFT processing unit 4A performs F
The data after FT is integrated in the Doppler direction. If the Doppler value after integration is greater than a certain reference value, the isolated point calculation processing unit 2A is notified and the isolated point is selected again. Other operations are the same as those in the case of FIG. 1, and thus the description thereof will be omitted.

As described above, in this embodiment, the optimum isolated point can be selected by measuring the spread of the FFT processed data in the Doppler direction and feeding back the result to the isolated point calculation processing section. , ISAR images that do not spread in the Doppler direction can be obtained. still,
A fixed value may be used as a reference of whether or not it is spread in the Doppler direction, or it may be adaptively determined according to the amplitude.

Fourth Embodiment 4 is a block diagram of an ISAR signal processing system according to Embodiment 4 of the present invention. 4, parts corresponding to those in FIG. 3 are designated by the same reference numerals, and detailed description thereof will be omitted. In the present embodiment, the Doppler direction spread measurement unit 3 in the third embodiment is used.
Instead of 1, simple FFT processing unit 4 as simple FFT means
1 and the Doppler direction spread measuring unit 42.

Next, the operation will be described. Before performing the FFT in the FFT processing unit 4A, the simple FFT processing unit 41 performs the simple FFT by thinning out the number of data, and then the Doppler direction spread measuring unit 42 measures the spread in the Doppler direction. The calculation processing unit 2A recalculates the isolated points. The other operations are the same as those in the case of FIG. 3, and the description thereof will be omitted.

As described above, according to the present embodiment, before the FFT processing, the simple FFT in which the number of data items is thinned is performed, the spread thereof is measured, and the result is fed back to the isolated point calculation processing section. In addition to the effect of the form 3, the cycle of reselecting the isolated point can be accelerated.

Embodiment 5. 5 is a block diagram of an ISAR signal processing system according to Embodiment 5 of the present invention. 5, parts corresponding to those in FIG. 1 are designated by the same reference numerals, and detailed description thereof will be omitted. In the present embodiment, in the first embodiment, the Doppler direction spread measurement unit,
An image determination unit is added, and further, the phase compensation processing unit to the Doppler direction spread measurement unit are combined into one, and some of them are arranged in parallel.

In the figure, 51, 55 and 58 are Doppler direction spread measuring units, 52 is an image determining unit as image determining means, 53 and 56 are phase compensation processing units, and 54 and 57 are FFs.
The T processing unit. Doppler direction spread measurement unit 51 is FF
The phase compensation processing units 53, F are provided in the subsequent stage of the T processing unit 4A, and the phase compensation processing units 53,
The column circuits of the FT processing unit 54 and the Doppler-direction spread measuring unit 55 and the column circuits of the phase compensation processing unit 56, the FFT processing unit 57, and the Doppler-direction spread measuring unit 58 are connected in parallel to form an M-sequence circuit configuration. The output sides of the Doppler direction spread measurement units 51, 55, 58 are all connected to the image determination unit 52.

Next, the operation will be described. Obtaining some candidate isolated points in the isolated point calculation processing unit 2A,
Phase compensation processing units 3A, 53 and 56 based on each isolated point
Phase compensation is performed respectively. After that, the FFT processing unit 4
A, 54, and 57 perform FFT processing respectively, and Doppler direction spread measurement units 51, 55, and 58 perform Doppler direction spread measurement, respectively, and the image determination unit 52 uses the data that has not spread most in the Doppler direction. Is selected, the amplitude detection processing unit 5 performs amplitude detection and IS
Form an AR image.

As described above, according to the present embodiment, when performing isolated point calculation, some candidates are selected, phase compensation and FFT processing are performed for all the candidates, and the spread in the Doppler direction is measured, By outputting an ISAR image that is determined to have a small spread in the Doppler direction, an ISAR image that does not spread in the Doppler direction can be formed without reselecting isolated points.

[0035]

As described above, according to the first aspect of the invention, in the ISAR signal processing method, the transmitted wave is applied to the target, the reflected wave is received, and the physical shape of the target is output as an image. It is caused by a first step of compensating the relative distance between the radar device and the target, a second step of calculating a reference point when performing phase compensation processing, and a change in the relative distance between the radar device and the target. a third step of compensating the change component of the Doppler frequency, and a fourth step of performing FFT processing, and a fifth step of performing amplitude detection, the third step from the first step, its
Respectively synthetic aperture time period necessary to form a single image
Since one screen is formed by processing the less than data and accumulating the processed data in the fourth step, there is an effect that the hardware resources in the ISAR signal processing can be made small and constant. .

According to the invention of claim 2, the third
After the phase compensation in the step of, the data for a plurality of pulses is integrated according to the synthetic aperture time. Therefore, even after the FFT processing, it is only necessary to process the data amount for the synthetic aperture time which is the reference. There is an effect that it can contribute to small-scale and constant wear resources.

According to the invention of claim 3, the fourth
The spread in the Doppler direction of the data after the FFT processing of the step is measured, and the result is fed back to the second step, so that the optimum isolated point serving as a reference when performing the phase compensation processing can be selected. There is an effect that an ISAR image that does not spread in the direction can be obtained.

According to the invention of claim 4, the fourth
Before the FFT process of the step, a simple FFT in which the number of data is thinned is performed, the spread thereof is measured, and the result is fed back to the second step. Therefore, an isolated point serving as a reference when performing the phase compensation process is determined. This has the effect of speeding up the cycle of reselection.

According to the invention of claim 5, the second
When performing the processing of step, some candidates are selected, phase compensation and FFT processing are performed for all of the candidates, the spread in the Doppler direction is measured, and the ISAR image determined to have the smallest spread in the Doppler direction Is output, the ISAR that does not spread in the Doppler direction without reselecting the isolated point serving as the reference when performing the phase compensation processing is output.
There is an effect that an image can be formed.

Further, according to the invention of claim 6, in the ISAR signal processing device for applying the transmitted wave to the target, receiving the reflected wave, and outputting the physical shape of the target as an image,
Distance compensation means for compensating data less than the synthetic aperture time necessary to form one image related to the relative distance between the radar device and the target, and phase compensation based on the output of the distance compensation means An isolated point calculating means for calculating a reference point for processing, and a phase for compensating for a change component of the Doppler frequency caused by a change in the relative distance between the radar device and the target based on the output of the isolated point calculating means. The compensation means and the output of the phase compensation means are sequentially accumulated, and FF is applied to all the accumulated data for one synthetic aperture time.
Since the FFT means for performing the T process and the amplitude detection means for performing the amplitude detection on the output of the FFT means are provided, the ISA
There is an effect that the hardware resources in the R signal processing can be made small and constant, the configuration can be simplified, and the cost can be reduced.

Further, according to the invention of claim 7, since the presum processing means for integrating the data for a plurality of pulses according to the synthetic aperture time after the phase compensation is provided, the hardware resources are small and constant. Therefore, there is an effect that it can contribute to the simplification of the configuration and the cost reduction.

According to the invention of claim 8, the FF is provided.
Since the spread in the Doppler direction of the T-processed data is measured and the result is fed back to the isolated point calculating unit, the spread measuring unit for Doppler direction is provided, so that an ISAR image that does not spread in the Doppler direction can be obtained. This has the effect of improving accuracy.

According to the invention of claim 9, the FF is provided.
Before the T processing, a simple FFT unit that performs a simple FFT by thinning the number of data, and a spread of the thinned data in the Doppler direction based on the output of the simple FFT unit are measured,
Since the Doppler direction spread measuring means for feeding back the result to the isolated point calculating means is provided, the cycle for reselecting the isolated point serving as the reference when performing the phase compensation processing can be accelerated and the accuracy of the image processing is improved. The effect is that you can do it.

Further, according to the invention of claim 10, in the ISAR signal processing device for applying the transmitted wave to the target, receiving the reflected wave, and outputting the physical shape of the target as an image, the radar device and the target are provided. A distance compensating means for compensating data less than the synthetic aperture time required to form one image related to the relative distance of the image, and a phase compensating processing for performing the phase compensating processing based on the output of the distance compensating means. An isolated point calculating means for calculating a reference point, a plurality of phase compensating means for performing phase compensation for all the candidates by selecting some candidates when performing the isolated point calculation, and each of the phase compensating means. A plurality of FFT means for performing FFT processing on the output, and a plurality of Doppler direction spread measuring means for measuring the spread in the Doppler direction based on each output of the FFT means;
Since the image determination means outputs the ISAR image determined to have the smallest spread in the Doppler direction based on each output of the Doppler direction spread measurement means, the isolated point serving as a reference when performing the phase compensation processing is determined. There is an effect that an ISAR image that does not spread in the Doppler direction can be formed without reselection, and the accuracy of image processing can be improved at a processing speed equivalent to that of the conventional apparatus.

[Brief description of drawings]

FIG. 1 is a diagram showing a processing block diagram and a data processing image in a first embodiment of the present invention.

FIG. 2 is a diagram showing a processing block diagram and a data processing image in the second embodiment of the present invention.

FIG. 3 is a processing block diagram according to a third embodiment of the present invention.

FIG. 4 is a processing block diagram according to a fourth embodiment of the present invention.

FIG. 5 is a processing block diagram according to a fifth embodiment of the present invention.

FIG. 6 is a diagram showing a processing block diagram and a data processing image in a conventional ISAR signal processing system.

[Explanation of symbols]

1A distance compensation processing unit, 2A isolated point calculation processing unit,
3A, 53, 56 Phase compensation processing unit, 4A, 54, 5
7 FFT processing unit, 5 amplitude detection processing unit, 21 presum processing unit, 31, 42, 51, 55, 58 Doppler direction spread measurement unit, 41 simple FFT processing unit, 5
2 Image determination unit.

─────────────────────────────────────────────────── ─── Continuation of the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) G01S ⁷ /00-7/42 G01S 13/00-13/95

Claims (10)

(57) [Claims] 1. An Inverse Synthetic Aperture Radar (hereinafter referred to as ISAR) signal processing method for applying a transmitted wave to a target, receiving the reflected wave, and outputting the physical shape of the target as an image, comprising a radar device and the target. Of the Doppler frequency caused by a change in the relative distance between the radar device and the target, a first step of compensating the relative distance between the radar device and the target, and a second step of calculating a reference point when performing the phase compensation process. The third step of compensating for the above, the fourth step of performing the FFT processing, and the fifth step of performing the amplitude detection. The first step to the third step each form one image. The ISA is characterized in that one screen is formed by processing data that is less than the synthetic aperture time required for processing and accumulating the processed data in the fourth step.
R signal processing method. 2. The ISAR signal processing method according to claim 1, wherein after the phase compensation in the third step, data integration for a plurality of pulses is performed according to the synthetic aperture time. 3. The ISAR signal processing method according to claim 1, wherein the spread in the Doppler direction of the data after the FFT processing in the fourth step is measured, and the result is fed back to the second step. . 4. Before the FFT processing of the fourth step,
3. The ISAR according to claim 1 or 2, wherein a simple FFT in which the number of data is thinned is performed, its spread is measured, and the result is fed back to the second step.
Signal processing method. 5. When performing the processing of the second step, some candidates are selected, phase compensation and FFT processing are performed for all of the candidates, the spread in the Doppler direction is measured, and the spread in the most Doppler direction is measured. 5. An ISAR image that is judged to be small is output.
The ISAR signal processing method according to any one of 1. 6. An ISAR that applies a transmitted wave to a target, receives the reflected wave, and outputs the physical shape of the target as an image.
In the signal processing device, a distance compensating means for compensating the data shorter than the synthetic aperture time necessary for forming one image related to the relative distance between the radar device and the target, and the output of the distance compensating means. Based on the isolated point calculation means for calculating a reference point when performing the phase compensation processing, and a change in the Doppler frequency caused by a change in the relative distance between the radar device and the target based on the output of the isolated point calculation means. A phase compensating means for compensating the component, an FFT means for sequentially accumulating the outputs of the phase compensating means and performing an FFT process on all the accumulated data of one synthetic aperture time, and an output of the FFT means. And an amplitude detection means for performing amplitude detection. 7. After phase compensation, depending on the synthetic aperture time,
7. The ISAR signal processing device according to claim 6, further comprising a presum processing means for integrating data of a plurality of pulses. 8. The Doppler direction spread measuring means for measuring the spread of the FFT processed data in the Doppler direction and feeding back the result to the isolated point calculating means. ISA
R signal processing device. 9. A simple FFT means for performing a simple FFT by thinning out the number of data before the FFT processing, and the simple FFT.
8. The ISAR according to claim 6 or 7, further comprising: Doppler direction spread measuring means for measuring the spread in the Doppler direction of the data thinned out based on the output of the means and feeding back the result to the isolated point calculating means.
Signal processing device. 10. An ISA that applies a transmitted wave to a target, receives the reflected wave, and outputs the physical shape of the target as an image.
In the R signal processing device, a distance compensating means for compensating data less than the synthetic aperture time necessary for forming one image related to the relative distance between the radar device and the target, and the distance compensating means. An isolated point calculating means for calculating a reference point when performing phase compensation processing based on the output, and a plurality of candidates selected when performing the isolated point calculation, and a plurality of candidates for performing phase compensation for all the candidates. Phase compensation means, a plurality of FFT means for performing FFT processing on each output of the phase compensation means, and a plurality of Doppler direction spread measurement means for measuring the spread in the Doppler direction based on each output of the FFT means, An image determination unit that outputs an ISAR image in which the spread in the Doppler direction is determined to be the smallest based on each output of the Doppler direction spread measurement unit is provided. ISAR signal processing apparatus according to.