JP2011191267A - Apparatus, program and method of specifying target speed - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately specify the speed of a target from a SAR image, after azimuthal compression. <P>SOLUTION: A plurality of estimated speeds of a target are input. A reference function for the azimuth compression calculated, based on a relative distance between the SAR and the target, and synthetic aperture time is generated per input estimated speed. In particular, start time and finish time of the synthetic aperture time are changed, according to the estimated speed to generate the reference function in a predetermined case. The input SAR image after the azimuth compression is once azimuth-decompressed and restored to data before the azimuth compression, and azimuth-compressed again, based on each generated reference function to reproduce the image. The reference function used in reproducing the sharpest image is identified, and the estimated speed used in generating the identified reference function is specified as the speed of the target. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a technique for identifying the speed of a target from, for example, a SAR (Synthetic Aperture Radar) image.

  Patent Document 1 describes specifying the speed of a target from a SAR image after azimuth compression (data after azimuth compression). In Patent Document 1, the data after azimuth compression is decompressed using the azimuth compression reference function used for azimuth compression, and returned to the data before azimuth compression. Then, by changing the predicted speed of the target, a plurality of azimuth compression reference functions are generated, the data before azimuth compression is again azimuth compressed using the generated azimuth compression reference functions, and a plurality of post-azimuth compression data Is generated. Among the generated images after azimuth compression, identify the azimuth compression reference function used to obtain the clearest image data, and specify the target prediction speed used to generate the azimuth compression reference function. Identify the speed of the target.

JP 2007-292532 A

Even with the method described in Patent Document 1, it is possible to specify the speed of the target. However, in the method described in Patent Document 1, there is a possibility that an error of a predetermined value or more is included in the speed of the specified target.
An object of the present invention is to specify the speed of a target with high accuracy from a SAR image after azimuth compression.

The target speed specifying device according to the present invention is:
A target speed specifying device that specifies a speed of a target observed by a SAR (Synthetic Aperture Radar),
A data input unit for inputting the range-compressed data obtained by performing range compression on the target data observed by the SAR and storing the data in the storage device;
A SAR speed input unit that inputs a speed of a SAR-equipped machine having the SAR and stores the speed in a storage device;
A synthetic aperture time information input unit for inputting synthetic aperture time information indicating a start time and an end time of the synthetic aperture time and storing the information in a storage device;
A predicted speed input unit that inputs a plurality of predicted speeds of the target and stores them in a storage device;
The speed of the SAR-equipped machine input by the SAR speed input unit, the synthetic aperture time indicated by the synthetic aperture time information input by the synthetic aperture time information input unit, and a plurality of predicted speeds input by the predicted speed input unit Based on the relative speed between the SAR and the target represented based on the speed of the SAR-equipped machine and the speed of the target, and the synthetic opening time, for each predicted speed input by the predicted speed input unit. A reference function generation unit that generates a plurality of reference functions by generating a reference function to be generated, and, in a predetermined case, a start time and an end time of the synthetic aperture time according to the predicted speed A reference function generation unit that generates a reference function by changing,
An azimuth compression processing unit that generates azimuth-compressed data after the range compression and generates a plurality of azimuth-compressed data by a processing device based on each reference function of a plurality of reference functions generated by the reference function generation unit;
A definition calculation unit that calculates the definition of an image of a target indicated by each azimuth-compressed data of the plurality of azimuth-compressed data generated by the azimuth compression processing unit; and
When the reference function used to generate the azimuth-compressed data having a high definition of the target image calculated by the definition calculation unit is generated, the predicted speed used by the reference function generation unit is determined as the target. And a speed specifying unit that is specified by the processing device as the speed.

The predicted speed input unit includes a polynomial that represents a predicted speed of the target in the range direction and a polynomial that represents the predicted speed of the target in the azimuth direction, in order from the predetermined order of the predetermined polynomial, Enter multiple predicted speeds of the target generated by changing the coefficient,
The speed specifying unit specifies the coefficient of the order of the polynomial by specifying the speed of the target when represented by the polynomial of the order,
The predicted speed input unit sets a coefficient other than the coefficient of the degree of the polynomial to a specified value if the coefficient is already specified by the speed specifying unit, and sets a predetermined value if the coefficient is not specified. It is characterized by that.

When the predicted speed generated by changing the 0th order coefficient of the polynomial representing the predicted speed in the range direction of the target is input, the reference function generation unit sets the synthetic aperture time according to the predicted speed. It is characterized by generating a reference function by changing.

ここで、ｒ_ＰＴはＳＡＲと目標物との相対距離、ｔは時刻、Ｒ_０は合成開口中心でのＳＡＲと目標物との距離、ｖ_ｒＥは地球の自転による目標物のレンジ方向速度、ｖ_ａＥは地球の自転による目標物のアジマス方向速度、Ｖ_ｒＴは目標物自身の移動による目標物のレンジ方向速度、Ｖ_ａＴは目標物自身の移動による目標物のアジマス方向速度、ａ_Ｐ＿０はＳＡＲ搭載機の速度の０次成分、ｆ_ｒｅｆ（ｔ）は参照関数、ｒｅｃｔ（ｔ／Ｔ）はｔがＴに含まれる場合は１、ｔがＴに含まれない場合は０となる関数、λは、ＳＡＲから放射される電波の波長、α^ｓ _{ｓｔａｒｔ}は前記合成開口時間情報入力部が入力した合成開口時間の開始時刻、α^ｓ _ｅｎｄは前記合成開口時間情報入力部が入力した合成開口時間の終了時刻、ａ_１は数５、ａ_２は数６である。

The reference function generator is
Generated by changing the 0th order coefficient of the polynomial that represents the predicted speed of the target in the azimuth direction and the first order coefficient of the polynomial that represents the predicted speed of the target in the range direction. When either of the predicted speeds is input, based on the formula that expands Formula 1 representing the relative distance between the SAR and the target based on Formula 2 and limits it to the second order term, Formula 3 To generate a reference function,
When the predicted speed generated by changing the 0th-order coefficient of the polynomial representing the predicted speed in the range direction of the target is input, the formula 1 is expanded and based on the formula limited to the second-order terms. At the same time, the reference function is generated by calculating Equation 3 by changing the start time and end time of the synthetic aperture time based on Equation 4.

Here, r _PT is the relative distance between the SAR and the target, t is the time, R ₀ is the distance between the SAR and the target at the center of the synthetic aperture, v _rE is the range speed of the target due to the rotation of the earth, v _aE is the target azimuth speed due to the rotation of the earth, V _rT is the target range speed due to the movement of the target itself, V _aT is the target azimuth speed due to the movement of the target itself, and a _{P_0} is the SAR mounted 0th-order component of the machine speed, f _ref (t) is a reference function, rect (t / T) is a function that is 1 when t is included in T, and 0 when t is not included in T, λ is , The wavelength of the radio wave radiated from the SAR, α ^s _start is the start time of the synthetic aperture time input by the synthetic aperture time information input unit, and α ^s _end is the _end of the synthetic aperture time input by the synthetic aperture time information input unit time, _{a 1} is the number 5, a It is the number 6.

The reference function generator is
When a predicted speed generated by changing other coefficients is input, Formula 2 is calculated based on an expression obtained by expanding Formula 1 representing a relative distance between the SAR and the target to a predetermined order. And generating a reference function.

The predicted speed input unit includes a predicted speed generated by changing a 0th-order coefficient of a polynomial that represents a predicted speed of the target in the azimuth direction, and a first-order coefficient of a polynomial that represents the predicted speed of the target in the range direction. Are input in a predetermined order, and then input the predicted speed generated by changing the 0th-order coefficient of the polynomial representing the predicted speed in the range direction of the target, The prediction speed generated by changing the coefficient is input in a predetermined order.

When the predicted speed generated by changing the 0th-order coefficient of a polynomial representing the predicted speed of the target in the range direction is input, the speed specifying unit has high azimuth compression of the target image. When there are a plurality of post-data, the prediction function used by the reference function generation unit when generating a reference function used to generate a plurality of post-azimuth-compressed data with high definition of the target image. The highest predicted speed among the speeds is specified as the speed of the target.

The target speed specifying program according to the present invention includes:
A target speed specifying program for specifying a speed of a target observed by SAR (Synthetic Aperture Radar),
A data input process for inputting range-compressed data obtained by subjecting the target data observed by the SAR to range compression;
SAR speed input processing for inputting the speed of a SAR-equipped machine equipped with SAR;
Synthetic opening time information input processing for inputting synthetic opening time information indicating the start time and end time of the synthetic opening time;
A predicted speed input process for inputting a plurality of predicted speeds of the target;
The speed of the SAR-equipped machine input in the SAR speed input process, the synthetic aperture time indicated by the synthetic aperture time information input in the synthetic aperture time information input process, and a plurality of predicted speeds input in the predicted speed input process On the basis of the predicted speed input in the predicted speed input process, the relative distance between the SAR and the target represented based on the speed of the SAR-equipped machine and the speed of the target and the synthetic opening time are obtained. A reference function generation process for generating a plurality of reference functions by changing a start time and an end time of the synthetic opening time according to the predicted speed in a predetermined case. A reference function generation process for generating a reference function;
Based on each reference function of a plurality of reference functions generated in the reference function generation processing, azimuth compression processing to generate a plurality of azimuth compressed data by azimuth compressing the range-compressed data;
A definition calculation process for calculating the definition of the image of the target indicated by each azimuth-compressed data of the plurality of azimuth-compressed data generated by the azimuth compression process;
When generating the reference function used to generate the azimuth-compressed data having a high definition of the target image calculated in the definition calculation process, the predicted speed used in the reference function generation process is set as the target. It is characterized by causing a computer to execute a speed specifying process that specifies the speed of the above.

In the predicted speed input process, with respect to a polynomial that represents the predicted speed of the target in the range direction and a polynomial that represents the predicted speed of the target in the azimuth direction, the order of the polynomial in the order from the predetermined order of the predetermined polynomial Enter multiple predicted speeds of the target generated by changing the coefficient,
In the speed specifying process, the coefficient of the order of the polynomial is specified by specifying the speed of the target when represented by the polynomial of the order,
In the predicted speed input process, coefficients other than the coefficient of the order of the polynomial are set to specified values when already specified in the speed specifying process, and are set to predetermined values when not specified. It is characterized by that.

In the reference function generation process, when a predicted speed generated by changing a 0th order coefficient of a polynomial that represents a predicted speed in the range direction of the target is input, the synthetic aperture time is set according to the predicted speed. It is characterized by generating a reference function by changing.

ここで、ｒ_ＰＴはＳＡＲと目標物との相対距離、ｔは時刻、Ｒ_０は合成開口中心でのＳＡＲと目標物との距離、ｖ_ｒＥは地球の自転による目標物のレンジ方向速度、ｖ_ａＥは地球の自転による目標物のアジマス方向速度、Ｖ_ｒＴは目標物自身の移動による目標物のレンジ方向速度、Ｖ_ａＴは目標物自身の移動による目標物のアジマス方向速度、ａ_Ｐ＿０はＳＡＲ搭載機の速度の０次成分、ｆ_ｒｅｆ（ｔ）は参照関数、ｒｅｃｔ（ｔ／Ｔ）はｔがＴに含まれる場合は１、ｔがＴに含まれない場合は０となる関数、λは、ＳＡＲから放射される電波の波長、α^ｓ _{ｓｔａｒｔ}は前記合成開口時間情報入力処理で入力した合成開口時間の開始時刻、α^ｓ _ｅｎｄは前記合成開口時間情報入力処理で入力した合成開口時間の終了時刻、ａ_１は数１１、ａ_２は数１２である。

In the reference function generation process,
Generated by changing the 0th order coefficient of the polynomial that represents the predicted speed of the target in the azimuth direction and the first order coefficient of the polynomial that represents the predicted speed of the target in the range direction. When any one of the predicted speeds is input, Equation 7 representing the relative distance between the SAR and the target is expanded based on Equation 8 and based on an equation limited to the second order term, Equation 9 To generate a reference function,
When the predicted speed generated by changing the 0th-order coefficient of the polynomial representing the predicted speed in the range direction of the target is input, the formula 7 is expanded and based on the formula limited to the second-order terms In addition, the reference function is generated by calculating Equation 9 by changing the start time and end time of the synthetic aperture time based on Equation 10.

Here, r _PT is the relative distance between the SAR and the target, t is the time, R ₀ is the distance between the SAR and the target at the center of the synthetic aperture, v _rE is the range speed of the target due to the rotation of the earth, v _aE is the target azimuth speed due to the rotation of the earth, V _rT is the target range speed due to the movement of the target itself, V _aT is the target azimuth speed due to the movement of the target itself, and a _{P_0} is the SAR mounted 0th-order component of the machine speed, f _ref (t) is a reference function, rect (t / T) is a function that is 1 when t is included in T, and 0 when t is not included in T, λ is , The wavelength of the radio wave radiated from the SAR, α ^s _start is the _start time of the synthetic aperture time input in the synthetic aperture time information input process, and α ^s _end is the _end of the synthetic aperture time input in the synthetic aperture time information input process time, _{a 1} is the number 1 , _{A 2} is the number 12.

In the reference function generation process,
When a predicted speed generated by changing other coefficients is input, Formula 8 is calculated based on an expression obtained by expanding Formula 7 representing a relative distance between the SAR and the target to a predetermined order. And generating a reference function.

In the predicted speed input process, the predicted speed generated by changing the 0th order coefficient of the polynomial representing the predicted speed of the target in the azimuth direction and the first order coefficient of the polynomial representing the predicted speed in the range direction of the target Are input in a predetermined order, and then input the predicted speed generated by changing the 0th-order coefficient of the polynomial representing the predicted speed in the range direction of the target, The prediction speed generated by changing the coefficient is input in a predetermined order.

In the speed specifying process, when a predicted speed generated by changing a 0th-order coefficient of a polynomial representing a predicted speed of the target in the range direction is input, azimuth compression with high definition of the target image When there are a plurality of post-data, the prediction function used in the reference function generation process when generating a reference function used to generate a plurality of post-azimuth-compressed data with high definition of the target image. The highest predicted speed among the speeds is specified as the speed of the target.

The target speed specifying method according to the present invention includes:
A target speed specifying method for specifying a speed of a target observed by a SAR (Synthetic Aperture Radar),
A data input step of inputting range-compressed data obtained by subjecting the target data observed by the SAR to range compression;
A SAR speed input process for inputting the speed of the SAR-equipped machine equipped with the SAR;
A synthetic opening time information input step for inputting synthetic opening time information indicating a start time and an end time of the synthetic opening time;
A predicted speed input step for inputting a plurality of predicted speeds of the target;
The speed of the SAR-equipped machine input in the SAR speed input step, the synthetic aperture time indicated by the synthetic aperture time information input in the synthetic aperture time information input step, and a plurality of predicted speeds input in the predicted speed input step On the basis of the predicted speed input in the predicted speed input step, the relative distance between the SAR and the target represented based on the speed of the SAR-equipped machine and the speed of the target, and the synthetic opening time are obtained. A reference function generating step for generating a plurality of reference functions by changing a start time and an end time of the synthetic opening time according to the predicted speed in a predetermined case. A reference function generation step for generating a reference function;
An azimuth compression processing step for generating a plurality of azimuth-compressed data by azimuth-compressing the range-compressed data based on each reference function of a plurality of reference functions generated in the reference function generation step;
A definition calculation step for calculating a definition of an image of a target indicated by each azimuth-compressed data of the plurality of azimuth-compressed data generated in the azimuth compression processing step;
When generating the reference function used to generate the azimuth-compressed data having a high definition of the target image calculated in the definition calculation step, the predicted speed used in the reference function generation step is determined as the target. And a speed specifying step for specifying the speed as a speed.

  The target velocity specifying device according to the present invention generates a reference function by changing the start time and the end time of the synthetic opening time according to the predicted speed in a predetermined case, thereby generating the target speed with high accuracy. Can be specified.

Explanatory drawing of the relative distance of SAR and the moving target. Explanatory drawing of the influence of the target moving. FIG. 3 is a functional block diagram illustrating functions of the target velocity identification device 100 according to the first embodiment. The flowchart which shows the process of the target object speed specific | specification apparatus 100. FIG. The flowchart which shows the process of a 1st speed component specific step. Explanatory drawing of several reference function _fref (t) produced | generated by (S22). The flowchart which shows the process of a 2nd speed component specific step. Explanatory drawing of several reference function _fref (t) produced | generated by (S32). The flowchart which shows the process of a 3rd speed component specific step. The flowchart which shows the process of an image reproduction step. The figure which shows an example when a Doppler frequency band is restrict | limited. The figure which shows the correspondence of a Doppler frequency domain and a time domain. The figure which shows the change of the sharpness calculated by (S34) when the Doppler frequency area | region is restrict | limited. Explanatory drawing of the peak having the highest definition having a predetermined range. The figure which shows an example of the hardware constitutions of the target object speed specific | specification apparatus 100. FIG.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
In the following description, the processing device is a CPU 911 or the like which will be described later. The storage device is a ROM 913, a RAM 914, a magnetic disk 920, a cache memory, a register, or the like included in the CPU 911, which will be described later. The input device is a keyboard 902, a communication board 915, and the like which will be described later. That is, the processing device, the storage device, and the input device are hardware.

ここで、ｔは、時刻である。Ｔは、合成開口時間である。ｒｅｃｔ（ｔ／Ｔ）は、ｔがＴに含まれる場合は１、ｔがＴに含まれない場合は０となる関数である。λは、ＳＡＲから放射される電波の波長である。ｒ_ＰＴは、ＳＡＲと目標物との相対距離である。 Embodiment 1 FIG.
In the SAR image reproduction process, generally, a signal obtained by the SAR is subjected to range compression, range migration correction, and azimuth compression to generate image data.
Azimuth compression is correlation processing between the data after range compression and the reference function f _ref (t) (azimuth compression reference function). The reference function f _ref (t) is a function obtained from the relative distance (relative motion) between the SAR and the target, and is expressed as Equation 13. In azimuth compression, the Doppler frequency is calculated based on the reference function f _ref (t), and image data is obtained by forming an image on a normal Doppler.

Here, t is time. T is the synthetic opening time. rect (t / T) is a function that is 1 when t is included in T, and 0 when t is not included in T. λ is the wavelength of the radio wave emitted from the SAR. r _PT is the relative distance between the SAR and the target.

ここで、Ｒ_０は、合成開口中心（ｔ＝０）でのＳＡＲと目標物との距離である。ｖ_ｒＥは、地球の自転による目標物のレンジ方向速度である。ｖ_ｒＴは、目標物自身の移動による目標物のレンジ方向速度である。ｖ_ａＴは、目標物自身の移動による目標物のアジマス方向速度である。Ｖ_Ｐは、ＳＡＲを搭載したＳＡＲ搭載機の速度（アジマス方向速度）である。
なお、数１４では、地球の自転がレンジ方向にだけ影響する場合を示している。しかし、地球の自転がレンジ方向だけでなく、アジマス方向にも影響する場合も考えられ、この場合には、数１４は数１５のように書き換えられる。

ここで、ｖ_ａＥは、地球の自転による目標物のアジマス方向速度である。 FIG. 1 is an explanatory diagram of the relative distance between a SAR and a moving target. Note that there are two types of movement of the target object: movement of the target object and movement due to the rotation of the earth.
As shown in FIG. 1, the relative distance between the SAR and the moving target can be expressed as in Expression 14.

Here, R ₀ is the distance between the SAR and the target at the center of the synthetic aperture (t = 0). _vrE is the range direction velocity of the target due to the rotation of the earth. v _rT is the speed in the range direction of the target due to the movement of the target itself. v _aT is the speed in the azimuth direction of the target due to the movement of the target itself. V _P is the speed of the SAR mounting machine equipped with a SAR (azimuth direction velocity).
In Equation 14, the case where the rotation of the earth affects only the range direction is shown. However, it is conceivable that the rotation of the earth affects not only the range direction but also the azimuth direction. In this case, Equation 14 is rewritten as Equation 15.

Here, _vaE is the azimuth direction speed of the target due to the rotation of the earth.

ここで、αは、ＳＡＲ搭載機の進行方向真横に対して、スクイントさせた電波の放射角度である。 Equations (14) and (15) represent the relative distance between the SAR-equipped machine and the target when the radio wave is radiated from the SAR in a direction (straight side) perpendicular to the traveling direction of the SAR-equipped machine. When radio waves are squinted and emitted from the SAR, Equation 15 can be expressed as Equation 16. Note that “radiating a radio wave by squinting” means that the radio wave is not emitted from the SAR in a direction perpendicular to the traveling direction of the SAR, but is tilted forward and backward in the traveling direction of the SAR.

Here, α is the radiation angle of the radio wave squinted with respect to the side of the traveling direction of the SAR-equipped machine.

  In the following description, Equation 14 is used to simplify the description. That is, the case where the rotation of the earth affects only the range direction will be described as an example in which radio waves are radiated from the SAR in a direction (straight side) perpendicular to the traveling direction of the SAR-equipped machine. However, based on the following description, it is easy to apply to the case where Expressions 15 and 16 are used.

V _P (t), v _rT (t), and v _aT (t) are respectively defined as follows.
_{V P (t) = a P_0} + a P_1 t + a P_2 t 2 + ··· + a P_n t n
_{v rT (t) = a rT_0} + a rT_1 t + a rT_2 t 2 + ··· + a rT_k t k
v _aT (t) = a _aT — ₀ + a _{aT — 1} t + a _{aT —} ² t ² +... + a _{aT —} ^l t ^l
Then, _rPT can be expanded and expressed as in Expression 17.

When Expression 17 is an expression up to the second order term relating to time t, it is expressed as Expression 18.

すると、数１８を数２０のように変形できる。

数２０から、時刻ｔの２次関数の頂点（ｘ，ｙ）は、数２１のように表せる。

It is defined as Equation 19.

Then, Equation 18 can be transformed into Equation 20.

From Equation 20, the vertex (x, y) of the quadratic function at time t can be expressed as Equation 21.

ここで、数２２においてａ_２は、数２３である。

FIG. 2 is an explanatory diagram of the influence of the moving target. In FIG. 2, a curve when the target shown in Equation 20 is moving is indicated by a solid line. Further, in FIG. 2, a curve obtained when the target is stationary at the position of the synthetic aperture center of the target indicated by a solid line is indicated by a broken line. In FIG. 2, the vertical axis represents the relative distance between the SAR and the target, and the horizontal axis represents the time.
Note that the target object is stationary not only when the target object does not move, but also when the target object does not move due to the rotation of the earth. Therefore, if the target is stationary, the number 18 of the _{v rE, a rT_0, a rT_1} , v aE, by substituting 0 into _{a AT_0,} the _{r PT} when the target is stationary This can be expressed as Equation 22.

Here, in Equation 22, a ₂ is Equation 23.

  As can be seen from FIG. 2, when the target is moving, the position of the vertex (x, y) of the quadratic function shown in Equation 20 and the quadratic function are compared with the case where the target is stationary. The shape (curvature) of the curve represented by is different.

First, the influence of different positions of the vertex (x, y) of the quadratic function will be described.
As described above, in the SAR image reproduction process, image data is usually obtained by forming an image on zero Doppler. Zero Doppler is the vertex position of the quadratic function on the time axis. That is, if the target is stationary, an image is formed at (0, a ₀ ) in FIG. 2 that is the position of the center of the synthetic aperture. Therefore, when the target is stationary, the target is displayed at the original position of the target.
However, when the target is moving, an image is formed at the position (−a ₁ / 2a ₂ , a ₀ −a ₁ ² / 4a ₂ ) in FIG. In other words, when the target is moving, in the azimuth-compressed data, the position (−a ₁ / 2a ₂ , a) different from the position (0, a ₀ ) at the center of the synthetic aperture where the target should be originally displayed. _0- a ₁ ² / 4a ₂ ), an image of the target is formed and the target is displayed.
It should be noted that the position (0, a ₀ ) where the target should be originally displayed is not known even if the data after azimuth compression is viewed.

Similarly, both the moving target and the stationary target shown in FIG. 2 are originally generated based on the synthetic opening time T from the start time −T / 2 to the end time T / 2. It should be azimuth compressed using f _ref (t).
However, normally, assuming that the vertex position of the quadratic function on the time axis is the synthetic aperture center, azimuth compression is performed using a reference function f _ref (t) generated with a predetermined time before and after the synthetic aperture center as a synthetic aperture time. The That is, in FIG. 2, the reference function f _ref (t) generated based on the synthetic opening time T ′ from the start time −T / 2−a ₁ / 2a ₂ to the end time T / 2−a ₁ / 2a ₂ is represented by Used for azimuth compression.
The signal value for the moving target exists only from the time −T / 2 to the time T / 2, and does not exist from the time T / 2 to the time T / 2−a ₁ / 2a ₂ . Therefore, compared to the case where the azimuth compression is performed using the reference function f _ref (t) generated based on the synthetic opening time T from the start time −T / 2 to the end time T / 2, the start time −T / 2−. When azimuth compression is performed using the reference function f _ref (t) generated based on the synthetic opening time T ′ from a ₁ / 2a ₂ to the end time T / 2−a ₁ / 2a ₂ , The correlation between the signal value and the reference function f _ref (t) becomes low. That is, the luminance of the target pixel in the azimuth-compressed data is low and the image is blurred.

Next, the influence of the difference in the shape (curvature) of the curve represented by the quadratic function will be described.
Usually, azimuth compression is performed using a reference function f _ref (t) on the assumption that the target is stationary. The shape (curvature) of the curve of the reference function f _ref (t) assuming that the target is stationary is different from the shape (curvature) of the signal value curve for the moving target. Therefore, when the correlation between the signal value for the moving target and the reference function f _ref (t) is taken, the correlation is low. That is, the luminance of the target pixel in the azimuth-compressed data is low and the image is blurred.

Here, as shown in equation 19, the constant component _{a RT_0} in the range direction velocity of the target is not included in the _{a 0} and _{a 2,} contained only in _{a 1.} Further, as shown in Expression 20, a ₁ is because it is not a factor of t ^2, a ₁ will not affect the shape of the curve represented by a quadratic function of time t (curvature). That is, the constant component _{arT_0 of the} speed in the range direction of the target does not affect the shape of the curve represented by the quadratic function at time t.
On the other hand, as can be seen from Equation 21, a ₁ affects the position of the vertex (x, y) of the quadratic function at time t. That is, the constant component _{arT_0} of the range direction velocity of the target affects the position of the vertex (x, y) of the quadratic function at time t.

In Patent Document 1, the speed is specified using blurring of an image based on a difference in the shape (curvature) of a curve. However, as described above, in _Equation 18 excluding higher-order components of the third or higher order, the constant component _{arT_0} of the target range speed does not affect the shape (curvature) of the curve of the quadratic function. . Therefore, in the method of Patent Document 1, the constant component _{arT_0} of the range direction speed of the target cannot be specified using _Equation 18 excluding the higher-order components of the third order or higher.
As shown in _Equation 17, the higher-order component also includes the constant component _{arT_0} of the target range speed. Therefore, it is theoretically possible to specify the constant component _{arT_0} of the target range speed in Patent Document 1.
However, the speed of a moving target such as a vehicle is strongly influenced by low-order components and weakly influenced by high-order components. Therefore, when the speed of a moving target such as a vehicle is specified by the method of Patent Document 1, an error may be included in the constant component _{arT_0} of the range direction speed.
Therefore, the target velocity specifying apparatus 100 according to this embodiment uses the deviation of the vertex position of the quadratic function to specify the constant component _{arT_0} of the target range speed. Thereby, the range direction speed | velocity | rate of a target can be pinpointed with high precision rather than the method of patent document 1. FIG.

A target speed identification device 100 according to this embodiment will be described.
FIG. 3 is a functional block diagram showing the functions of the target speed identification device 100 in this embodiment.
The target speed identification device 100 includes an input unit 110 and a processing unit 120.
The input unit 110 includes a data input unit 111, a predicted speed input unit 112, a synthetic opening time information input unit 113, and a SAR speed input unit 114.
The processing unit 120 includes a reference function generation unit 121, an image reproduction unit 122, a sharpness calculation unit 123, and a speed specification unit 124. The image reproduction unit 122 includes a range migration correction unit 125, a zero padding processing unit 126, an FFT processing unit 127, an azimuth compression processing unit 128, and an IFFT processing unit 129.

FIG. 4 is a flowchart showing the processing of the target speed identification device 100.
(S1: Input step)
The data input unit 111 selects one target from the azimuth-compressed data (SLC (single look complex) image), cuts out a range including the target by the processing device, and decompresses the azimuth compression of the cut-out range image. The generated range-compressed data is generated by the processing device. And the data input part 111 inputs the data after range compression, and memorize | stores it in a memory | storage device. Note that decompressing azimuth compression means performing reverse processing of azimuth compression using the reference function f _ref (t) used at the time of azimuth compression.
The synthetic aperture time information input unit 113 also inputs synthetic aperture time information indicating the start time α ^s _start and the end time α ^s _end of the synthetic aperture time t ^s and stores them in the storage device. The synthetic aperture time for the target is specified from the position where the target is imaged.
Furthermore, SAR speed input section 114 stores in the storage device by entering the velocity _{V P} of the SAR mounting machine. Incidentally, as a premise, the speed _{V P} of the SAR mounting machine are known.

(S2: First speed component specifying step)
A constant component a _{aT — 0} of the target azimuth direction velocity and a primary component _{arT —} 1 of the range direction velocity are specified in a predetermined order. Here, _description will be made _assuming that the constant component a _{aT — 0} of the target azimuth direction velocity is first specified, and then the primary component a _{rT —} 1 of the range direction velocity is specified.
Here, the constant component a _{aT — 0 of the} target azimuth direction velocity and the primary component a _{rT —} 1 of the range direction velocity are specified using the blurring of the image based on the difference in the shape (curvature) of the curve.

参照関数生成部１２１は、（Ｓ１）で入力されたＳＡＲ搭載機の速度Ｖ_Ｐ（ここでは、Ｖ_Ｐの定数成分ａ_Ｐ＿０）と、（Ｓ２１）で入力された目標物のレンジ方向速度の１次成分ａ_ｒＴ＿１を、数２４に示す式に代入する。さらに、参照関数生成部１２１は、（Ｓ２１）で入力された目標物のアジマス方向速度の定数成分ａ_ａＴ＿０を、数２４に示す式に代入して、目標物のアジマス方向速度の定数成分ａ_ａＴ＿０毎にｒ_ＰＴ（ｔ）を計算する。そして、参照関数生成部１２１は、計算されたｒ_ＰＴ（ｔ）を用いて、数１３を計算することにより、（Ｓ２１）で入力された目標物のアジマス方向速度の定数成分ａ_ａＴ＿０毎に参照関数ｆ_ｒｅｆ（ｔ）を処理装置により生成する。
図６は、（Ｓ２２）で生成される複数の参照関数ｆ_ｒｅｆ（ｔ）の説明図である。図６では、目標物の信号値を実線で示し、生成される参照関数ｆ_ｒｅｆ（ｔ）のいくつかの例を破線で示す。図６に示すように、参照関数生成部１２１は、目標物のアジマス方向速度の定数成分ａ_ａＴ＿０に応じて、ｔの２次関数の曲線の形状（曲率）を様々に変化させた複数の参照関数ｆ_ｒｅｆ（ｔ）を生成する。
なお、（Ｓ１）で入力された合成開口時間は図６に示す合成開口時間Ｔ’である。
（Ｓ２３：画像再生ステップ）
画像再生部１２２は、（Ｓ２２）で生成した各参照関数ｆ_ｒｅｆ（ｔ）に基づき（Ｓ１）で入力されたレンジ圧縮後データをアジマス圧縮して、アジマス圧縮後データを処理装置により生成する。なお、画像再生ステップについて、詳しくは後述する。
（Ｓ２４：鮮明度算出ステップ）
鮮明度算出部１２３は、（Ｓ２３）で生成したアジマス圧縮後データが示す目標物の画像の鮮明度を処理装置により算出する。ここで、鮮明度とは、画像の画素の輝度であり、言い替えれば、画像再生処理で実行されたアジマス圧縮において、参照関数ｆ_ｒｅｆ（ｔ）と信号値との相関の高さを表す。
つまり、鮮明度算出部１２３は、図６において、合成開口時間Ｔ’が示す範囲における目標物の信号値を示す実線と、各参照関数ｆ_ｒｅｆ（ｔ）を示す破線との相関（一致の程度）を計算する。図６から分かるように、目標物の信号値を示す実線の曲率と、参照関数ｆ_ｒｅｆ（ｔ）を示す破線の曲率とが近いほど、相関は高くなる。
（Ｓ２５：速度特定ステップ）
速度特定部１２４は、（Ｓ２４）で算出した目標物の画像の鮮明度が最も高いアジマス圧縮後データを処理装置により特定する。速度特定部１２４は、特定したアジマス圧縮後データを生成するために使用した参照関数ｆ_ｒｅｆ（ｔ）を処理装置により特定する。つまり、図６において、目標物の信号値を示す実線と、参照関数ｆ_ｒｅｆ（ｔ）を示す破線との一致の程度が最も大きい参照関数ｆ_ｒｅｆ（ｔ）を特定する。
そして、速度特定部１２４は、特定した参照関数ｆ_ｒｅｆ（ｔ）を（Ｓ２２）で生成する場合に使用した目標物のアジマス方向速度の定数成分ａ_ａＴ＿０を処理装置により特定する。これにより、目標物のアジマス方向速度の定数成分ａ_ａＴ＿０を特定することができる。 FIG. 5 is a flowchart showing the process of the first speed component specifying step.
First, a constant component a _{aT — 0} of the target azimuth direction velocity is specified.
(S21: Speed input step)
The predicted speed input unit 112 inputs the constant component a _{aT — 0 of the} speed in the azimuth direction of various targets as the predicted speed and stores it in the storage device. Further, the predicted speed input unit 112 inputs 0 or a predetermined value as the primary component _{arT_1} of the range direction speed and stores it in the storage device.
(S22: Reference function generation step)
The reference function generation unit 121 calculates Equation 13 using _Equation 24 in which the constant component _{arT_0} of the range speed of the target in Equation 18 is 0 as an expression indicating the relative motion between the SAR and the target. A reference function f _ref (t) is generated by the processing device.

The reference function generation unit 121 uses the SAR-equipped machine speed V _P (here, the constant component a _{P — 0 of} V _P ) input in (S1) and 1 in the range direction speed of the target input in (S21). The next component _{arT_1} is substituted into the equation shown in Equation 24. Furthermore, the reference function generating unit 121, a constant component _{a AT_0} azimuthal velocity of the input target in (S21), by substituting the equations shown in Equation 24, constant component azimuthal velocity of the target _{a AT_0} Calculate r _PT (t) every time. Then, the reference function generation unit 121 calculates _Equation 13 using the calculated r _PT (t), thereby referring to each constant component a _{aT — 0 of} the target azimuth direction velocity input in (S21). The function f _ref (t) is generated by the processing device.
FIG. 6 is an explanatory diagram of a plurality of reference functions f _ref (t) generated in (S22). In FIG. 6, the signal value of the target is indicated by a solid line, and some examples of the generated reference function f _ref (t) are indicated by a broken line. As shown in FIG. 6, the reference function generation unit 121 has a plurality of references in which the shape (curvature) of the quadratic function curve of t is variously changed according to the constant component a _{aT — 0} of the target azimuth direction velocity. A function f _ref (t) is generated.
The synthetic aperture time input in (S1) is a synthetic aperture time T ′ shown in FIG.
(S23: Image reproduction step)
The image reproduction unit 122 azimuth-compresses the range-compressed data input in (S1) based on each reference function f _ref (t) generated in (S22), and generates the azimuth-compressed data by the processing device. Details of the image reproduction step will be described later.
(S24: Sharpness calculation step)
The definition calculation unit 123 calculates the definition of the target image indicated by the azimuth-compressed data generated in (S23) using the processing device. Here, the sharpness is the luminance of the pixel of the image, in other words, the height of the correlation between the reference function f _ref (t) and the signal value in the azimuth compression performed in the image reproduction process.
That is, in FIG. 6, the sharpness calculation unit 123 correlates the solid line indicating the signal value of the target in the range indicated by the synthetic aperture time T ′ and the broken line indicating each reference function f _ref (t) (degree of coincidence). ). As can be seen from FIG. 6, the closer the curvature of the solid line indicating the signal value of the target and the curvature of the broken line indicating the reference function f _ref (t), the higher the correlation.
(S25: Speed specifying step)
The speed specifying unit 124 uses the processing device to specify the azimuth-compressed data having the highest sharpness of the target image calculated in (S24). The speed specifying unit 124 specifies the reference function f _ref (t) used for generating the specified azimuth-compressed data by the processing device. That is, in FIG. 6, the reference function f _ref (t) having the greatest degree of coincidence between the solid line indicating the signal value of the target and the broken line indicating the reference function f _ref (t) is specified.
And the speed specific | specification part 124 specifies the constant component _{aaT_0} of the azimuth direction speed of the target used when producing | generating the specified reference function _fref (t) by (S22). Thereby, the constant component a _{aT — 0} of the target azimuth direction velocity can be specified.

Next, returning to (S21), the primary component _{arT_1} of the target range speed is specified.
(S21: Speed input step)
The predicted speed input unit 112 inputs the primary component _{arT_1} of the range direction speeds of various targets and stores them in the storage device. Further, the predicted speed input unit 112 inputs the constant component a _{aT — 0} of the target azimuth direction speed specified by the above-described processing and stores it in the storage device.
(S22: Reference function generation step)
The reference function generation unit 121 uses the SAR-equipped machine speed V _P (here, the constant component a _{P — 0 of VP} ) input in (S1) and the azimuth direction speed constant of the target input in (S21). The component a _{aT — 0} is substituted into the equation shown in Equation 24. Further, the reference function generation unit 121 substitutes the primary component _{arT_1} of the range speed of the target input in (S21) into the equation shown in Formula 24, _so that the primary component of the range speed of the target is obtained. a _Calculate r _PT (t) for each _{rT_1} . Then, the reference function generation unit 121 calculates _Equation 13 using the calculated r _PT (t), thereby calculating the primary component a _{rT —} 1 of the range direction velocity of the target input in (S21). The reference function f _ref (t) is generated by the processing device.
In other words, the reference function generation unit 121 has a plurality of reference functions f _ref () in which the shape (curvature) of the curve of the quadratic function of t is variously changed according to the primary component a _{rT —} 1 of the target range speed. t).
(S23: Image reproduction step)
The image reproduction unit 122 azimuth-compresses the range-compressed data input in (S1) based on each reference function f _ref (t) generated in (S22), and generates the azimuth-compressed data by the processing device.
(S24: Sharpness calculation step)
The definition calculation unit 123 calculates the definition of the target image indicated by the azimuth-compressed data generated in (S23) using the processing device.
(S25: Speed specifying step)
The speed specifying unit 124 uses the processing device to specify the azimuth-compressed data having the highest sharpness of the target image calculated in (S24). When generating the reference function f _ref (t) used to generate the specified azimuth-compressed data, the speed specifying unit 124 uses the first-order component a _{rT —} 1 of the target range speed used in (S22). Is specified by the processing device. Thereby, the primary component _{arT_1} of the range direction speed of the target can be specified.
As described above, since the constant component a _{aT — 0} of the target azimuth direction velocity and the primary component _{arT —} 1 of the range direction velocity can be identified, the processing of (S2) is terminated and the processing proceeds to (S3).

(S3: Second speed component specifying step)
A constant component _{arT_0 of the} speed in the range direction of the target is specified.
As described above, the constant component _{arT_0} of the target range speed does not affect the shape of the curve represented by the quadratic function at time t. Therefore, here, the constant component _{arT_0 of the} speed in the range direction of the target is specified using the deviation of the vertex position of the quadratic function.

FIG. 7 is a flowchart showing the processing of the second speed component specifying step.
(S31: Speed input step)
The predicted speed input unit 112 inputs the constant component _{arT_0} of the range direction speed of various targets as the predicted speed and stores it in the storage device. Further, the azimuth direction velocity constant component a _{aT — 0} and the range direction velocity primary component a _{rT —} 1 specified in (S2) are input and stored in the storage device.
(S32: Reference function generation step)
The reference function generation unit 121 generates the reference function f _ref (t) by the processing device by calculating Expression 13 using Expression 24.
First, the reference function generation unit 121 sets the SAR-equipped machine speed V _P (here, the constant component a _{P — 0 of} V _P ) input in (S1) and the azimuth direction speed of the target input in (S31). The constant component a _{aT — 0} and the primary component a _{rT —} 1 of the range direction velocity are substituted into the equation shown in Equation 24. Thereby, one r _PT (t) is calculated.
The reference function generator 121, start time alpha ^s _start and end times alpha ^s _{end The} and the respective start times ^{_{α s start + a 1 / 2a}} 2 and end time of the input synthetic aperture time ^{t s} in (S1) α ^s _end + a ₁ / 2a ₂ That is, the reference function generating unit 121, the synthetic aperture time in reproduction of the target stationary ^{t s} is the synthetic aperture start time alpha ^s _start from and end times alpha ^s _{end The ^{"α s start ≦ t s <α}} s _{In the} case of “ _end ”, the synthetic opening time t ^T here is “α ^s _start + a ₁ / 2a ₂ ≦ t ^T <α ^s _end + a ₁ / 2a ₂ ”.
Based on this, the reference function generation unit 121 calculates the equation 13 to generate the reference function f _ref (t). A ₁ and a ₂ are as shown in _Equation 19, and a ₁ includes a primary component a _{rT — 0} of the range direction velocity. Therefore, the reference function f _ref (t) is generated for each primary component a _{rT — 0} of the range direction velocity input in (S31).
FIG. 8 is an explanatory diagram of a plurality of reference functions f _ref (t) generated in (S32). In FIG. 8, the signal value of the target is indicated by a solid line, and the generated reference function f _ref (t) is indicated by a broken line. As shown in FIG. 8, since the constant component a _{aT — 0 in} the azimuth direction and the primary component a _{rT —} 1 in the range direction velocity are specified in (S2), the shape (curvature) of the quadratic function curve is One is specified. Here, the reference function generation unit 121 has a plurality of ranges in which the quadratic function cut out of the specified curve shape (curvature) is shifted in the time axis direction as in the synthetic opening times (1), (2), and (3). The reference function f _ref (t) is generated. Note that the width of the cut-out range in the time axis direction is fixed, and any synthetic opening time is equal to α ^s _end −α ^s _start shown in the synthetic opening time (1).
(S33: Image reproduction step)
The image reproduction unit 122 azimuth-compresses the range-compressed data input in (S1) based on each reference function f _ref (t) generated in (S32), and generates the azimuth-compressed data by the processing device.
(S34: Sharpness calculation step)
The definition calculation unit 123 calculates the definition of the target image indicated by the azimuth-compressed data generated in (S33) using the processing device.
That is, in FIG. 8, the definition calculation unit 123 calculates the correlation (degree of coincidence) between the solid line indicating the signal value of the target and the broken line at each synthetic aperture time. The closer the range in the time axis direction of the solid line indicating the signal value of the target and the range of the synthetic aperture time, the higher the correlation.
(S35: Speed specifying step)
The speed specifying unit 124 uses the processing device to specify the azimuth-compressed data having the highest definition of the target image calculated in (S34). When generating the reference function f _ref (t) used for generating the specified post-azimuth-compressed data, the speed specifying unit 124 uses the primary component a _{rT —} 1 of the target range speed used in (S32). Is specified by the processing device. Thereby, the primary component _{arT_1} of the range direction speed of the target can be specified.

(S4: Third speed component specifying step)
Identify the remaining velocity component of the target. That is, the components of the target in the azimuth direction that are higher than the primary component and the components in the range direction that are higher than the secondary component are specified in a predetermined order. For example, the primary component in the azimuth direction of the target, the secondary component in the range direction of the target, the secondary component in the azimuth direction of the target, the tertiary component in the range direction of the target, and so on. Identify from.
Here, the remaining velocity component of the target is specified using blurring of the image based on the difference in the shape of the curve.

FIG. 9 is a flowchart showing the process of the third speed component specifying step.
(S41: Speed input step)
The predicted speed input unit 112 changes the speed component to be specified in various ways, inputs it as a predicted speed, and stores it in the storage device. The predicted speed input unit 112 also receives the constant component a _{aT — 0 of} the target azimuth direction velocity identified in (S2) and (S3), the constant component a _{rT — 0} and the primary component a _{rT —} 1 of the range direction speed. And store it in the storage device. The predicted speed input unit 112 inputs 0 or a predetermined value for the other speed components and stores it in the storage device.
For example, when the primary component of the target in the azimuth direction is specified, the predicted speed input unit 112 changes the primary component a _{aT —} 1 of the target in the azimuth direction and inputs it as the predicted speed. Further, the predicted speed input unit 112 inputs the constant component a _{aT — 0} of the azimuth direction speed specified in (S2) and (S3), the constant component a _{rT — 0} and the primary component a _{rT —} 1 of the range direction speed. Further, the predicted speed input unit 112 sets 0 or a predetermined value as another speed component (a component higher than the secondary component in the azimuth direction of the target and a component higher than the secondary component in the range direction of the target). input.
(S42: Reference function generation step)
Referring function generation unit 121 into the equation shown in SAR and velocity _{V P} of the mounting machine, the number 17 to the velocity component input in (S41) input in (S1). Thus, r _PT (t) is calculated for each velocity component to be specified (here, the primary component a _{aT —} 1 of the target azimuth direction velocity) input in (S41). Then, the reference function generation unit 121 calculates _Equation 13 by using the calculated r _PT (t), so that the reference function f _ref (t ) Is generated by the processing device. That is, the reference function generation unit 121 generates a plurality of reference functions f _ref (t) in which the shape of the curve of the quadratic function of t is changed in accordance with the velocity component to be specified.
(S43: Image reproduction step)
The image reproduction unit 122 azimuth-compresses the range-compressed data input in (S1) based on each reference function f _ref (t) generated in (S42), and generates the azimuth-compressed data by the processing device.
(S44: Sharpness calculation step)
The definition calculation unit 123 calculates the definition of the target image indicated by the azimuth-compressed data generated in (S43) by the processing device.
(S45: Speed specifying step)
The speed specifying unit 124 uses the processing device to specify the azimuth-compressed data having the highest definition of the target image calculated in (S44). The speed specifying unit 124, when generating the reference function f _ref (t) used for generating the specified azimuth-compressed data, the speed component (here, the azimuth speed of the target object) used in (S42). Of the primary component a _{aT —} 1) is specified by the processing device. Thereby, the velocity component (here, the primary component a _{aT —} 1 of the velocity in the azimuth direction of the target) can be specified.
If all speed components are not specified, the process returns to (S41) again to specify other speed components. By repeating this, all speed components can be specified.

As described above, the target velocity specifying apparatus 100 according to this embodiment _pays attention to the shift of the vertex position of the quadratic function when specifying the primary component _{arT_1} of the target range speed, and the synthetic aperture A plurality of reference functions f _ref (t) were generated by changing the time. Thereby, the primary component _{arT_1} of the range direction speed of the target can be specified with high accuracy.

The target speed specifying device 100 can specify the speed of the target with high accuracy from, for example, the SAR image after azimuth compression. Therefore, in the ocean, analysis of suspicious boats, drift ice, etc., monitoring of operations, trend prediction, etc. It can be applied to. It is also effective for monitoring land and sea traffic.
In addition, the moving body included in the SAR image after azimuth compression can be detected by obtaining the speed for each pixel in the SAR image after azimuth compression and extracting the pixel at a speed equal to or higher than a predetermined speed. That is, it can be applied to a moving target indicator (MTI) technology.

_Further , when the equation 21 is calculated based on the constant component a _{aT — 0} of the azimuth direction velocity of the target specified in (S2) and (S3), the constant component a _{rT — 0} and the primary component a _{rT —} 1 of the range direction velocity, A deviation amount between the position where the object should be imaged and the vertex position of the quadratic function shown in Equation 18 is obtained. Therefore, it is possible to specify the position where the target should originally be imaged, that is, the position of the target at the center of the synthetic aperture.

  In the above description, it is assumed that the SLC data of the SAR image is input in (S1). However, as long as it is complex data, it may be MLC (multi-look complex) data which is a so-called multi-look processed image in which several pixels of SLC are weighted to be one pixel.

As a supplement, the image reproduction steps (S23), (S33), and (S43) will be described. The image reproduction step process is a general process and will be described briefly.
FIG. 10 is a flowchart showing the processing of the image reproduction step.

(S51: Range migration correction step)
The range migration correction unit 125 calculates a correction amount Cr according to the relative distance r _PT (t). The calculation method of the correction amount Cr is, for example, the method described in Patent Document 1. Based on the calculated correction amount Cr, the range migration correction unit 125 performs range migration correction on the data after range compression input by the data input unit 111 in (S1) and generates corrected data.

(S52: Zero padding process step)
The zero padding processing unit 126 generates zero padded data in which the number of pixels of the post-correction data is a power of two by padding the post-correction data generated in (S51) with 0.

(S53: Fast Fourier transform processing step)
The FFT processing unit 127 performs FFT (Fast Fourier Transform) on the zero padded data generated in (S52) and generates post-FFT data by the processing device.
The FFT processing unit 127 performs FFT on the reference function f _ref (t) generated by the reference function generation unit 121 and generates a post-FFT reference function by the processing device.

(S54: Azimuth compression processing step)
The azimuth compression processing unit 128 performs azimuth compression on the post-FFT data based on the post-FFT reference function generated by the FFT processing unit 127 in (S53), and generates azimuth post-compression data by the processing device.

(S55: Inverse Fast Fourier Transform processing step)
The IFFT processing unit 129 performs IFFT (Inverse Fast Fourier Transform) on the azimuth-compressed data that has been azimuth-compressed in (S54), and generates post-IFFT data by the processing device. Thereby, SAR image data compressed by azimuth is generated.

Embodiment 2. FIG.
In the second embodiment, a case where the Doppler frequency band is limited will be described.

In a system targeting a stationary target, the Doppler frequency band may be limited in order to image a stationary Doppler frequency with high quality. Limiting the Doppler frequency band means cutting (deleting) signal values for some frequency bands. Usually, the signal value in the high frequency band is cut. FIG. 11 is a diagram illustrating an example when the Doppler frequency band is limited. In FIG. 11, the signal value in the range of the frequency band S is cut.
Note that the trajectory of the target distance in the Doppler frequency domain and the trajectory of the target distance in the time domain can be handled equally. FIG. 12 is a diagram illustrating a correspondence relationship between the Doppler frequency domain and the time domain. FIG. 12 shows an example where the target is stationary. Since the change in relative distance in the Doppler frequency domain and the corresponding time are known, the time axis and the frequency axis can be uniquely associated. In FIG. 12, a region S1 in the frequency domain corresponds to a region S1 ′ in the time domain, and a region S2 in the frequency domain corresponds to a region S2 ′ in the time domain. Here, cutting a high frequency component in the Doppler frequency region corresponds to cutting a portion far from the vertex position of the quadratic function on the time axis.

FIG. 13 is a diagram illustrating the change in the sharpness calculated in (S34) when the Doppler frequency region is limited. In FIG. 13, the vertical axis is the evaluation value of the sharpness, and the horizontal axis is the constant component of the range direction speed.
As shown in FIG. 13, when the Doppler frequency region is limited, the peak with the highest sharpness calculated in (S34) has a predetermined range instead of one point. That is, the sharpness becomes the highest in the range where the constant component of the range direction speed is from _{arT — 0} 1 to a _{rT — 0} 2.

FIG. 14 is an explanatory diagram showing that the peak having the highest definition has a predetermined range.
In FIG. 14, the original synthetic aperture time is the synthetic aperture time T, which has a signal value in this range, but the signal in the region S (the two-dot broken line portion) is cut. In this case, the speed a _{rT — 0} when the synthetic aperture time T ′ used when generating the reference function f _ref (t) coincides with the synthetic aperture time ^T (when it becomes the synthetic aperture time t ^T (1) in FIG. 14). Is the speed that should be sought.
However, with (S1) Niu Omonbakaoku synthetic aperture time t ^s is gradually shifted to the left side in FIG. 14, the start time alpha ^s _start signal overlaps with a region S that is cut synthetic aperture time t ^T ( At 2), when the synthetic opening time t ^T (1) is reached, the correlation (degree of coincidence) between the solid line indicating the signal value of the target and the broken line at each synthetic opening time is the same. As it is, the synthetic aperture time t ^s is gradually shifted to the left side in FIG. 14, while the start time alpha ^s _start signal overlaps with the area S which has been cut, much synthetic aperture time t ^{T (1)} In this case, the correlation (degree of coincidence) between the solid line indicating the signal value of the target and the broken line at each synthetic aperture time is the same. When the start time α ^s _start exceeds the area S where the signal is cut, the correlation (degree of coincidence) between the solid line indicating the signal value of the target and the broken line at each synthetic opening time becomes low.
That is, the range of the constant component a _{rT — 0 in} the range direction speed in which the start time α ^s _start overlaps the signal cut region S in FIG. 14 is the range from a _{rT — 0} 1 to a _{rT — 0} 2 shown in FIG. Yes, the highest definition. Then, to the extent that sharpness is the highest, the rate to be determined originally, a speed in the case of the synthetic aperture time shifted largest from the input synthetic aperture time t ^s in (S1).
Here, the deviation between the more constant component _{a RT_0} in the range direction speed is high, the reference and functions _{f ref} (t) synthetic aperture time ^{t T} in to be generated, the synthetic aperture time ^{t s} input in (S1) Is big. Therefore, by specifying the fastest speed in the speed range where the definition is the highest, the speed that should be originally obtained can be specified. Accordingly, in FIG. 14, _{arT — 02} may be specified as a constant component of the range direction speed.

That is, when the band limitation of the Doppler frequency is performed, in (S35), the speed specifying unit 124 specifies a plurality of data after azimuth compression. Therefore, when generating the plurality of reference functions f _ref (t) used to generate the specified plurality of azimuth-compressed data, the speed specifying unit 124 uses the ranges of the plurality of targets used in (S32). The constant component _{arT_0} of the direction speed is specified, and the fastest speed is specified. Thereby, the constant component of the range direction speed of the target to be originally obtained can be specified.

Next, the hardware configuration of the target speed identification device 100 will be described.
FIG. 15 is a diagram illustrating an example of a hardware configuration of the target speed identification device 100.
As shown in FIG. 15, the target velocity specifying apparatus 100 includes a CPU 911 (also referred to as a central processing unit, a central processing unit, a processing unit, an arithmetic unit, a microprocessor, a microcomputer, and a processor) that executes a program. Yes. The CPU 911 is connected to the ROM 913, the RAM 914, the LCD 901 (Liquid Crystal Display), the keyboard 902 (K / B), the communication board 915, and the magnetic disk device 920 via the bus 912, and controls these hardware devices. Instead of the magnetic disk device 920 (fixed disk device), a storage device such as an optical disk device or a memory card read / write device may be used. The magnetic disk device 920 is connected via a predetermined fixed disk interface.

  The ROM 913 and the magnetic disk device 920 are examples of a nonvolatile memory. The RAM 914 is an example of a volatile memory. The ROM 913, the RAM 914, and the magnetic disk device 920 are examples of a storage device (memory). The keyboard 902 and the communication board 915 are examples of input devices. The communication board 915 is an example of a communication device (network interface). Furthermore, the LCD 901 is an example of a display device.

  An operating system 921 (OS), a window system 922, a program group 923, and a file group 924 are stored in the magnetic disk device 920 or the ROM 913. The programs in the program group 923 are executed by the CPU 911, the operating system 921, and the window system 922.

The program group 923 stores software, programs, and other programs that execute the functions described as “input unit 110”, “processing unit 120”, and the like in the above description. The program is read and executed by the CPU 911.
The file group 924 stores information, data, signal values, variable values, and parameters stored in the covering information storage device 34 in the above description as items of “file” and “database”. The “file” and “database” are stored in a recording medium such as a disk or a memory. Information, data, signal values, variable values, and parameters stored in a storage medium such as a disk or memory are read out to the main memory or cache memory by the CPU 911 via a read / write circuit, and extracted, searched, referenced, compared, and calculated. Used for the operation of the CPU 911 such as calculation / processing / output / printing / display. Information, data, signal values, variable values, and parameters are temporarily stored in the main memory, cache memory, and buffer memory during the operation of the CPU 911 for extraction, search, reference, comparison, calculation, calculation, processing, output, printing, and display. Is remembered.

In the above description, the arrows in the flowchart mainly indicate input / output of data and signals, and the data and signal values are recorded in a memory of the RAM 914, other recording media such as an optical disk, and an IC chip. Data and signals are transmitted online by a bus 912, signal lines, cables, other transmission media, and radio waves.
In addition, what is described as “to part” in the above description may be “to circuit”, “to device”, “to device”, “to means”, and “to function”. It may be “step”, “˜procedure”, “˜processing”. In addition, what is described as “˜device” may be “˜circuit”, “˜device”, “˜means”, “˜function”, and “˜step”, “˜procedure”, “ ~ Process ". Furthermore, what is described as “to process” may be “to step”. That is, what is described as “˜unit” may be realized by firmware stored in the ROM 913. Alternatively, it may be implemented only by software, or only by hardware such as elements, devices, substrates, and wirings, by a combination of software and hardware, or by a combination of firmware. Firmware and software are stored in a recording medium such as ROM 913 as a program. The program is read by the CPU 911 and executed by the CPU 911. That is, the program causes a computer or the like to function as the “˜unit” described above. Alternatively, the computer or the like is caused to execute the procedures and methods of “to part” described above.

  DESCRIPTION OF SYMBOLS 100 Target speed identification apparatus, 110 input part, 120 processing part, 111 data input part, 112 prediction speed input part, 113 synthetic aperture time information input part, 114 SAR speed input part, 121 reference function generation part, 122 image reproduction part , 123 sharpness calculation unit, 124 speed specifying unit, 125 range migration correction unit, 126 zero padding processing unit, 127 FFT processing unit, 128 azimuth compression processing unit, 129 IFFT processing unit.

Claims (15)

A target speed specifying device that specifies a speed of a target observed by a SAR (Synthetic Aperture Radar),
A data input unit for inputting the range-compressed data obtained by performing range compression on the target data observed by the SAR and storing the data in the storage device;
A SAR speed input unit that inputs a speed of a SAR-equipped machine having the SAR and stores the speed in a storage device;
A synthetic aperture time information input unit for inputting synthetic aperture time information indicating a start time and an end time of the synthetic aperture time and storing the information in a storage device;
A predicted speed input unit that inputs a plurality of predicted speeds of the target and stores them in a storage device;
The speed of the SAR-equipped machine input by the SAR speed input unit, the synthetic aperture time indicated by the synthetic aperture time information input by the synthetic aperture time information input unit, and a plurality of predicted speeds input by the predicted speed input unit Based on the relative speed between the SAR and the target represented based on the speed of the SAR-equipped machine and the speed of the target, and the synthetic opening time, for each predicted speed input by the predicted speed input unit. A reference function generation unit that generates a plurality of reference functions by generating a reference function to be generated, and, in a predetermined case, a start time and an end time of the synthetic aperture time according to the predicted speed A reference function generation unit that generates a reference function by changing,
An azimuth compression processing unit that generates azimuth-compressed data after the range compression and generates a plurality of azimuth-compressed data by a processing device based on each reference function of a plurality of reference functions generated by the reference function generation unit;
A definition calculation unit that calculates the definition of an image of a target indicated by each azimuth-compressed data of the plurality of azimuth-compressed data generated by the azimuth compression processing unit; and
When the reference function used to generate the azimuth-compressed data having a high definition of the target image calculated by the definition calculation unit is generated, the predicted speed used by the reference function generation unit is determined as the target. A target speed specifying device comprising: a speed specifying unit specified by a processing device as the speed of the target. The predicted speed input unit includes a polynomial that represents a predicted speed of the target in the range direction and a polynomial that represents the predicted speed of the target in the azimuth direction, in order from the predetermined order of the predetermined polynomial, Enter multiple predicted speeds of the target generated by changing the coefficient,
The speed specifying unit specifies the coefficient of the order of the polynomial by specifying the speed of the target when represented by the polynomial of the order,
The predicted speed input unit sets a coefficient other than the order coefficient of the polynomial to a specified value if it has already been specified by the speed specifying unit, and to a predetermined value if it has not been specified. The target speed specifying device according to claim 1, wherein When the predicted speed generated by changing the 0th order coefficient of the polynomial representing the predicted speed in the range direction of the target is input, the reference function generation unit sets the synthetic aperture time according to the predicted speed. 3. The target speed specifying device according to claim 2, wherein the reference function is generated by changing the reference function. The reference function generator is
Generated by changing the 0th order coefficient of the polynomial that represents the predicted speed of the target in the azimuth direction and the first order coefficient of the polynomial that represents the predicted speed of the target in the range direction. When either of the predicted speeds is input, based on the formula that expands Formula 1 representing the relative distance between the SAR and the target based on Formula 2 and limits it to the second order term, Formula 3 To generate a reference function,
When the predicted speed generated by changing the 0th-order coefficient of the polynomial representing the predicted speed in the range direction of the target is input, the formula 1 is expanded and based on the formula limited to the second-order terms. The target speed specifying apparatus according to claim 3, wherein the reference function is generated by calculating Formula 3 while changing the start time and end time of the synthetic aperture time based on Formula 4.

Here, r _PT is the relative distance between the SAR and the target, t is the time, R ₀ is the distance between the SAR and the target at the center of the synthetic aperture, v _rE is the range speed of the target due to the rotation of the earth, v _aE is the target azimuth speed due to the rotation of the earth, V _rT is the target range speed due to the movement of the target itself, V _aT is the target azimuth speed due to the movement of the target itself, and a _{P_0} is the SAR mounted 0th-order component of the machine speed, f _ref (t) is a reference function, rect (t / T) is a function that is 1 when t is included in T, and 0 when t is not included in T, λ is , The wavelength of the radio wave radiated from the SAR, α ^s _start is the start time of the synthetic aperture time input by the synthetic aperture time information input unit, and α ^s _end is the _end of the synthetic aperture time input by the synthetic aperture time information input unit time, _{a 1} is the number 5, a It is the number 6.

The reference function generator is
When a predicted speed generated by changing other coefficients is input, Formula 2 is calculated based on an expression obtained by expanding Formula 1 representing a relative distance between the SAR and the target to a predetermined order. The target speed specifying device according to claim 4, wherein the reference function is generated. The predicted speed input unit includes a predicted speed generated by changing a 0th-order coefficient of a polynomial that represents a predicted speed of the target in the azimuth direction, and a first-order coefficient of a polynomial that represents the predicted speed of the target in the range direction. Are input in a predetermined order, and then input the predicted speed generated by changing the 0th-order coefficient of the polynomial representing the predicted speed in the range direction of the target, The target speed specifying apparatus according to claim 5, wherein predicted speeds generated by changing the coefficient are input in a predetermined order. When the predicted speed generated by changing the 0th-order coefficient of a polynomial representing the predicted speed of the target in the range direction is input, the speed specifying unit has high azimuth compression of the target image. When there are a plurality of post-data, the prediction function used by the reference function generation unit when generating a reference function used to generate a plurality of post-azimuth-compressed data with high definition of the target image. The target speed specifying device according to any one of claims 3 to 6, wherein the highest predicted speed among the speeds is specified as the speed of the target. A target speed specifying program for specifying a speed of a target observed by SAR (Synthetic Aperture Radar),
A data input process for inputting range-compressed data obtained by subjecting the target data observed by the SAR to range compression;
SAR speed input processing for inputting the speed of a SAR-equipped machine equipped with SAR;
Synthetic opening time information input processing for inputting synthetic opening time information indicating the start time and end time of the synthetic opening time;
A predicted speed input process for inputting a plurality of predicted speeds of the target;
The speed of the SAR-equipped machine input in the SAR speed input process, the synthetic aperture time indicated by the synthetic aperture time information input in the synthetic aperture time information input process, and a plurality of predicted speeds input in the predicted speed input process On the basis of the predicted speed input in the predicted speed input process, the relative distance between the SAR and the target represented based on the speed of the SAR-equipped machine and the speed of the target and the synthetic opening time are obtained. A reference function generation process for generating a plurality of reference functions by changing a start time and an end time of the synthetic opening time according to the predicted speed in a predetermined case. A reference function generation process for generating a reference function;
Based on each reference function of a plurality of reference functions generated in the reference function generation processing, azimuth compression processing to generate a plurality of azimuth compressed data by azimuth compressing the range-compressed data;
A definition calculation process for calculating the definition of the image of the target indicated by each azimuth-compressed data of the plurality of azimuth-compressed data generated by the azimuth compression process;
When generating the reference function used to generate the azimuth-compressed data having a high definition of the target image calculated in the definition calculation process, the predicted speed used in the reference function generation process is set as the target. A target speed specifying program that causes a computer to execute speed specifying processing that specifies the speed of the target. In the predicted speed input process, with respect to a polynomial that represents the predicted speed of the target in the range direction and a polynomial that represents the predicted speed of the target in the azimuth direction, the order of the polynomial in the order from the predetermined order of the predetermined polynomial Enter multiple predicted speeds of the target generated by changing the coefficient,
In the speed specifying process, the coefficient of the order of the polynomial is specified by specifying the speed of the target when represented by the polynomial of the order,
In the predicted speed input process, coefficients other than the coefficient of the order of the polynomial are set to specified values when already specified in the speed specifying process, and are set to predetermined values when not specified. 9. The target speed specifying program according to claim 8. In the reference function generation process, when a predicted speed generated by changing a 0th order coefficient of a polynomial that represents a predicted speed in the range direction of the target is input, the synthetic aperture time is set according to the predicted speed. The target speed specifying program according to claim 9, wherein the reference function is generated by changing the reference function. In the reference function generation process,
Generated by changing the 0th order coefficient of the polynomial that represents the predicted speed of the target in the azimuth direction and the first order coefficient of the polynomial that represents the predicted speed of the target in the range direction. When any one of the predicted speeds is input, Equation 7 representing the relative distance between the SAR and the target is expanded based on Equation 8 and based on an equation limited to the second order term, Equation 9 To generate a reference function,
When the predicted speed generated by changing the 0th-order coefficient of the polynomial representing the predicted speed in the range direction of the target is input, the formula 7 is expanded and based on the formula limited to the second-order terms The target speed specifying program according to claim 10, wherein the reference function is generated by calculating Formula 9 by changing a start time and an end time of the synthetic opening time based on Formula 10.

Here, r _PT is the relative distance between the SAR and the target, t is the time, R ₀ is the distance between the SAR and the target at the center of the synthetic aperture, v _rE is the range speed of the target due to the rotation of the earth, v _aE is the target azimuth speed due to the rotation of the earth, V _rT is the target range speed due to the movement of the target itself, V _aT is the target azimuth speed due to the movement of the target itself, and a _{P_0} is the SAR mounted 0th-order component of the machine speed, f _ref (t) is a reference function, rect (t / T) is a function that is 1 when t is included in T, and 0 when t is not included in T, λ is , The wavelength of the radio wave radiated from the SAR, α ^s _start is the _start time of the synthetic aperture time input in the synthetic aperture time information input process, and α ^s _end is the _end of the synthetic aperture time input in the synthetic aperture time information input process time, _{a 1} is the number 1 , _{A 2} is the number 12.

In the reference function generation process,
When a predicted speed generated by changing other coefficients is input, Formula 8 is calculated based on an expression obtained by expanding Formula 7 representing a relative distance between the SAR and the target to a predetermined order. 12. The target speed specifying program according to claim 11, wherein the reference function is generated. In the predicted speed input process, the predicted speed generated by changing the 0th order coefficient of the polynomial representing the predicted speed of the target in the azimuth direction and the first order coefficient of the polynomial representing the predicted speed in the range direction of the target Are input in a predetermined order, and then input the predicted speed generated by changing the 0th-order coefficient of the polynomial representing the predicted speed in the range direction of the target, The target speed specifying program according to claim 12, wherein predicted speeds generated by changing the coefficient are input in a predetermined order. In the speed specifying process, when a predicted speed generated by changing a 0th-order coefficient of a polynomial representing a predicted speed of the target in the range direction is input, azimuth compression with high definition of the target image When there are a plurality of post-data, the prediction function used in the reference function generation process when generating a reference function used to generate a plurality of post-azimuth-compressed data with high definition of the target image. The target speed specifying program according to any one of claims 10 to 13, wherein the fastest predicted speed among the speeds is specified as the speed of the target. A target speed specifying method for specifying a speed of a target observed by a SAR (Synthetic Aperture Radar),
A data input step of inputting range-compressed data obtained by subjecting the target data observed by the SAR to range compression;
A SAR speed input process for inputting the speed of the SAR-equipped machine equipped with the SAR;
A synthetic opening time information input step for inputting synthetic opening time information indicating a start time and an end time of the synthetic opening time;
A predicted speed input step for inputting a plurality of predicted speeds of the target;
The speed of the SAR-equipped machine input in the SAR speed input step, the synthetic aperture time indicated by the synthetic aperture time information input in the synthetic aperture time information input step, and a plurality of predicted speeds input in the predicted speed input step On the basis of the predicted speed input in the predicted speed input step, the relative distance between the SAR and the target represented based on the speed of the SAR-equipped machine and the speed of the target, and the synthetic opening time are obtained. A reference function generating step for generating a plurality of reference functions by changing a start time and an end time of the synthetic opening time according to the predicted speed in a predetermined case. A reference function generation step for generating a reference function;
An azimuth compression processing step for generating a plurality of azimuth-compressed data by azimuth-compressing the range-compressed data based on each reference function of a plurality of reference functions generated in the reference function generation step;
A definition calculation step for calculating a definition of an image of a target indicated by each azimuth-compressed data of the plurality of azimuth-compressed data generated in the azimuth compression processing step;
When generating the reference function used to generate the azimuth-compressed data having a high definition of the target image calculated in the definition calculation step, the predicted speed used in the reference function generation step is determined as the target. A target speed specifying method comprising: a speed specifying step that specifies the speed of the target.

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