JP6381825B2 - Moving target detection device - Google Patents

Description

  The present invention relates to a moving target detection apparatus that detects a signal of a moving target from signals received at a plurality of antenna openings.

  Two or more antenna apertures are arranged in the traveling direction of the platform (hereinafter, this direction is referred to as the along track direction), and a synthetic aperture radar (SAR) is used by using signals received at the respective antenna apertures. A method is known in which a moving target is detected by suppressing a stationary target signal using a combination of these images after generating an image (see, for example, Non-Patent Document 1).

  As a method using two antenna openings, for example, a moving target detection method described in Non-Patent Document 2 is known. In this technique, SAR images are generated by using signals received at two antenna apertures, and the imbalance between channels of the two generated SAR images is corrected, and then the two SAR images are aligned. The difference or phase difference of the complex amplitude is calculated, and a difference image or a phase difference image is generated.

  It can be understood that these two SAR images are two images observed at the same place with a time difference. Then, since the stationary target signal matches in the two SAR images, the amplitude of the stationary target signal is suppressed in the difference image. In the phase difference image, the phase difference from the stationary target is almost zero. On the other hand, since the position of the moving target is shifted due to the movement of the target while observing each SAR image, the amplitude is not suppressed in the difference image. Further, in the phase difference image, a phase difference corresponding to the position shift occurs.

  Therefore, in the method described in Non-Patent Document 2, in order to detect the movement target signal, the difference between the stationary target or the pixel having the large absolute value in the difference image and the pixel having the large phase difference in the phase difference image are detected. Threshold processing is performed with a threshold value calculated from the probability density function of the phase difference, and a pixel having a pixel value equal to or greater than the threshold value is detected as a movement target.

Kazuo Ouchi, "Basics of Synthetic Aperture Radar for Remote Sensing", Tokyo Denki University Press C. Gierull, “Moving Target Detection with Along-Track SAR Interferometry”, Technical Report DRDC-OTTAWA-TR-2002-084, Defense Research & Development Canada, 2002

  However, in the conventional technique as described in Non-Patent Document 2, when an error occurs in two SAR images, a difference also occurs in a signal from a stationary target that should originally match. In the difference image, the signal of the stationary target is not suppressed and the signal from the stationary target remains. Also in the phase difference image, a phase difference occurs in the stationary target signals of the two SAR images. Due to such problems, the conventional moving target detection technique has a problem that a stationary target is erroneously detected as a moving target.

  The present invention has been made to solve such a problem, and an object of the present invention is to provide a moving target detection apparatus capable of detecting a moving target with high accuracy.

A moving target detection device according to the present invention includes a radar device that obtains each reception signal obtained by receiving pulse signals irradiated to an observation range with three or more antennas, a SAR image generation unit that generates each SAR image of each reception signal, and A motion measurement unit that measures the speed of the platform on which the antenna is mounted, and a registration unit that aligns each SAR image generated by the SAR image generation unit using the platform speed information measured by the motion measurement unit; The SAR images aligned by the registration unit are compared to correct the amplitude and phase imbalance of each SAR image, and the phase difference between each SAR image corrected by the signal calibrating unit. calculated, and calculates the standard deviation of the calculated phase difference, and a moving target detection unit that detects a moving target by the standard deviation thresholded It is intended.

The moving target detecting apparatus according to the present invention detects a moving target by causing a signal of each aligned SAR image to interfere to calculate a phase difference to calculate a standard deviation of the phase difference and thresholding the standard deviation. It is what you do. As a result, a stationary target that has been erroneously detected as a moving target due to phase noise as in the prior art is not detected as a moving target, and the moving target detection performance can be improved.

It is a block block diagram of the movement target detection apparatus of Embodiment 1 of this invention. It is a hardware block diagram of the movement target detection apparatus of Embodiment 1 of this invention. It is explanatory drawing which shows the geometry of observation by the moving target detection apparatus of Embodiment 1 of this invention. It is a hardware block diagram of the movement target detection apparatus of Embodiment 2 of this invention. It is a functional block diagram which shows the structure which implement | achieves the movement target detection process in the signal processing part of the movement target detection apparatus of Embodiment 2 of this invention. It is a block diagram of the sub-aperture division type movement target detection part of the movement target detection apparatus of Embodiment 2 of this invention. It is explanatory drawing which shows the sub-aperture division | segmentation by the relationship between the azimuth time and sub-aperture number of the moving target detection apparatus of Embodiment 2 of this invention. It is explanatory drawing which shows the history of the phase difference for every sub-aperture of the moving target of the moving target detection apparatus of Embodiment 2 of this invention and a low S / N stationary target. It is a functional block diagram which shows the structure which implement | achieves the movement target detection process in the signal processing part of the movement target detection apparatus of Embodiment 3 of this invention. It is a block diagram of the difference image sub-aperture division type movement target detection part of the movement target detection apparatus of Embodiment 3 of this invention. It is a functional block diagram which shows the structure which implement | achieves the movement target detection process in the signal processing part of the movement target detection apparatus of Embodiment 4 of this invention.

Hereinafter, in order to explain the present invention in more detail, modes for carrying out the present invention will be described with reference to the accompanying drawings.
Embodiment 1 FIG.
FIG. 1 is a block diagram of a moving target detection apparatus according to this embodiment.
The moving target detection apparatus according to the present embodiment includes a radar apparatus 10, a signal processing unit 20, and a motion measurement unit 30, as shown in the figure. The radar apparatus 10 is an apparatus for obtaining each received signal obtained by receiving a pulse signal irradiated to an observation range with three or more antennas. The signal processing unit 20 is a processing unit for detecting a movement target using the received signal acquired by the radar apparatus 10 and the platform motion information measured by the motion measurement unit 30, and in FIG. The functional block configuration is shown. The illustrated signal processing unit 20 includes a SAR image generation unit 21, a registration unit 22, a signal calibration unit 23, and a movement target detection unit 24. The SAR image generation unit 21 is a processing unit that generates each SAR image of each reception signal received by the radar apparatus 10. The registration unit 22 is a processing unit that aligns each SAR image generated by the SAR image generation unit 21 using speed information in the platform motion information measured by the motion measurement unit 30. The signal calibrating unit 23 is a processing unit that compares the SAR images aligned by the registration unit 22 and corrects the amplitude and phase imbalance of the SAR images. The movement target detection unit 24 is a processing unit that detects a movement target by calculating a phase difference from each SAR image calibrated by the signal calibration unit 23 and comparing the calculated phase difference. The motion measurement unit 30 is a processing unit that measures at least the speed of a platform on which three or more antennas are mounted in the radar apparatus 10.

FIG. 2 is a hardware configuration diagram of the moving target detection apparatus shown in FIG.
The radar apparatus 10 includes an excitation unit 101, an amplification unit 102, a reception unit 103, a data recording unit 104, a transmission / reception switch 105, a transmission / reception antenna 106, reception antennas 107a and 107b, and a motion measurement unit 30.
The excitation unit 101 is a processing unit that generates a pulse signal used for observation, and the generated pulse signal is output to the amplification unit 102. The amplification unit 102 is a processing unit that amplifies the pulse signal generated by the excitation unit 101 to a desired signal level, and the amplified signal is output to the transmission / reception antenna 106 via the transmission / reception switch 105. The transmission / reception switch 105 switches the transmission / reception antenna 106 between a transmission state and a reception state. The transmission / reception antenna 106 is an antenna for irradiating the pulse signal acquired from the amplification unit 102 to the atmosphere, and irradiates the pulse signal to the atmosphere. The pulse signal irradiated into the atmosphere is irradiated and scattered on a scatterer such as the ground surface. The transmitting / receiving antenna 106 and the receiving antennas 107a and 107b receive signals scattered by the scatterers. Here, the signal received by the transmission / reception antenna 106 is output to the reception unit 103 via the transmission / reception switch 105. In addition, signals received by the receiving antennas 107 a and 107 b are output to the receiving unit 103. The receiving unit 103 is a processing unit that extracts a baseband signal from an RF (Radio Frequency) signal, and the extracted baseband signal is output to the data recording unit 104. The data recording unit 104 is a recording unit for a signal acquired from the receiving unit 103. The input signal is A / D (Analog-to-Digital) converted by the A / D conversion unit 104a to perform predetermined sampling. It converts into the signal for every rate, and the converted signal is output to the memory | storage device 207 in the signal processing part 20. FIG.

  The motion measurement unit 30 is mounted on the same platform as the radar apparatus 10, and the position of the IMU (Internal Measurement Unit) that measures the three-axis angle (or angular velocity) and acceleration that controls motion as platform motion information and the position of the platform. It is comprised by the apparatus which measures the position of a platform, an attitude | position angle, etc., such as GPS (Global Positioning System) which outputs A, and a magnetic compass which outputs azimuth information, and acquires speed information of a platform at least. In addition, for more accurate observation, it is desirable that the motion measurement unit 30 can measure the position, speed, and posture of the platform. The exercise information acquired by the exercise measuring unit 30 is output to the storage device 207 in the signal processing unit 20.

The signal processing unit 20 includes a processor 201, a controller 202, a controller interface 203, a memory 204, a display interface 205, a display 206, and a storage device 207. The processor 201 is a processor for realizing the functions of the SAR image generation unit 21 to the movement target detection unit 24 illustrated in FIG. 1, and is connected to the controller 202 via the controller interface 203.
The control signal from the storage device 207 is received, and the received signal from the storage device 207, the exercise information, the processing program, and the like are read into the memory 204 to perform the operation. The result of the movement target detection process by the processor 201 is output to the display 206 via the display interface 205. The controller 202 outputs a control signal to each part of the radar apparatus 10 and the processor 201, and controls the movement target detection apparatus.

  Further, the SAR image generation unit 21 to the movement target detection unit 24 in the signal processing unit 20 illustrated in FIG. 1 store programs corresponding to the respective processing units in the storage device 207, and the processor 201 stores these programs in the memory 204. It is realized by reading in and executing.

  In the illustrated example, the antenna having a reception function is described as three antennas, that is, the transmission / reception antenna 106 and the reception antennas 107a and 107b. The receiving unit 103 and the data recording unit 104 have a function of simultaneously receiving and recording data for the number of reception channels.

  Next, the operation of the moving target detection apparatus according to the first embodiment will be described. FIG. 3 is an explanatory diagram showing the geometry of observation by the moving target detection apparatus according to Embodiment 1 of the present invention. Hereinafter, the observation signal of the moving target detection apparatus according to the first embodiment will be described with reference to FIG.

In FIG. 3, reference numeral 106 denotes a transmission / reception antenna, and 107a and 107b denote reception antennas. Reference numeral 300 denotes a movement target.
The transmission / reception antenna 106, the reception antenna 107a, and the reception antenna 107b are mounted on the same platform, for example. At this time, the transmitting / receiving antenna 106, the receiving antenna 107a, and the receiving antenna 107b are arranged in a line along the traveling direction of the platform. Note that the transmission / reception antenna 106, the reception antenna 107a, and the reception antenna 107b do not have to be mounted on the same platform, and may be mounted on different platforms. It shall move in a line. As a platform on which the antenna is mounted, it is preferable to use a moving body such as an aircraft, an artificial satellite, and a vehicle. In the following, an aircraft is assumed as a platform, and the description will proceed with the geometry of the aircraft in mind. However, the technology disclosed in this specification can be applied to observations using platforms such as artificial satellites and vehicles as well as aircraft. Yes, it does not limit the platform type.

As shown in FIG. 3, the distance between the transmission / reception antenna 106 and the reception antenna 107a is L ₁ , and the distance between the transmission / reception antenna 106 and the reception antenna 107b is L ₂ . θ _n is the off-nadir angle, and V _r [m / s] is the speed of the platform. It is assumed that the moving target detection device described in this specification has a squint angle of 0 degrees. That is, in the case of strip map mode observation, the irradiation direction of the antenna beam is always perpendicular to the traveling direction of the platform. In the case of spotlight mode observation and sliding spotlight mode observation, at the center of the synthetic aperture. It is assumed that the direction of the antenna beam is a direction orthogonal to the traveling direction.

  In the following, the time is represented by η [seconds]. As shown in FIG. 3, the position of the transmitting / receiving antenna 106 at time η = 0 is the origin o, the platform traveling direction is the x axis, the horizontal plane is orthogonal to the x axis, and the left direction with respect to the traveling direction is positive. A coordinate system is defined in which the axis is the y-axis and the vertical upward direction is the z-axis. Further, it is assumed that the altitude of the platform is h and the ground surface is at a height of z = −h [m] parallel to the xy plane.

ただし、Ｔ［秒］は観測時間である。At this time, the position of the transmission / reception antenna 106 at the time η is expressed by the following equation (1).

However, T [second] is an observation time.

なお、Ｒ_０は、次式で表される。

また、ｖ_ｇ０［ｍ／ｓ］は次式で定義される。

The moving target 300 moves on the ground surface, and the position and speed of the moving target 300 at time η = 0 are (0, y ₀ , −h) [m] and (0, v _y0 , 0) [ m / s]. That is, it is assumed that the movement target 300 has moved only in the y-axis direction. When the distance between the transmitting / receiving antenna 106 and the moving target 300 at time η = 0 is R ₀ [m], the distance R ₁ (η) between the transmitting / receiving antenna 106 and the moving target 300 at time η is expressed by the following equation. Is done.

R ₀ is represented by the following formula.

Further, v _g0 [m / s] is defined by the following equation.

In this specification, the direction from the position of the transmitting / receiving antenna 106 at the time η = 0 to the position of the moving target 300 is referred to as a cross-track direction (coordinates orthogonal to the platform trajectory). As a term corresponding to this, the x-axis direction parallel to the platform trajectory may be referred to as the along track direction. In this way, v _y0 is a cross track component of the movement target speed at time η = 0. In the moving target detection device described in this specification, since the squint angle is assumed to be 0 degree, the cross-track direction component of the moving target speed component is the same as that of the moving target speed in the line-of-sight direction of the radar. Match the ingredients.

Next, consider a case where radio waves are transmitted from the transmitting / receiving antenna 106 and received by the receiving antenna 107a and the receiving antenna 107b. The distance from the phase center to the moving target 300 when the position of the phase center of the radio wave received by the receiving antenna 107a coincides with (V _rη , 0, 0) is R ₂ (η), and the radio wave received by the receiving antenna 107b When the distance from the phase center to the moving target 300 when the position of the phase center coincides with (V _rη , 0, 0) is R ₃ (η), it is defined by the following equation.

Here, Δη ₁ is the position of the phase center when the transmission / reception antenna 106 transmits radio waves and the reception antenna 107a receives radio waves from the time when the transmission / reception antenna 106 is at the position of (V _rη , 0, 0). The time difference until the position (V _rη , 0, 0) is _reached is shown. Δη ₂ is the position of the phase center when the transmission / reception antenna 106 transmits radio waves and the reception antenna 107b receives radio waves from the time when the transmission / reception antenna 106 is at the position of (V _rη , 0, 0). The time difference until the position of V _rη , 0,0) is _reached . Δη ₁ and Δη ₂ are given by the following equations, respectively.

The approximation of the above equation (6) is that the baseline length L _{1 from} the transmission / reception antenna 106 to the reception antenna 107 a and the baseline length L ₂ from the transmission / reception antenna 106 to the reception antenna 107 b are the distance R ₀ between the transmission / reception antenna 106 and the moving target 300. This is true under sufficiently short conditions. Further, in the approximation of the above equation (6), L ₁ and L ₂ represent physical distances from the transmission / reception antenna 106 to the reception antenna 107a and from the transmission / reception antenna 106 to the reception antenna 107b, whereas d ₁ And d ₂ are the phase center and the transmission / reception antenna when the transmission / reception antenna 106 transmits radio waves from the position of the electrical phase center when transmission / reception is performed by the transmission / reception antenna 106 and then the reception antenna 107a receives the radio waves. The distance from the transmission of the radio wave at 106 to the center of the phase when the radio wave is received by the receiving antenna 107a is shown.

At time η + Δη ₁ , the position of the movement target 300 in the cross track direction is R ₀ + v _g0 (η + Δη ₁ ), respectively. Similarly, at time η + Δη ₂ , the position of the movement target 300 in the cross track direction is R ₀ + v _g0 (η + Δη ₂ ), respectively.

  Next, the received signal model of the moving target detection device in the first embodiment and the principle of moving target detection in the first embodiment will be described based on the above observation geometry.

ここで、ａ_１（η）とａ_２（η）、ａ_３（η）はそれぞれ送受信アンテナ１０６、受信アンテナ１０７ａ、受信アンテナ１０７ｂにおける受信信号の振幅である。また、信号Ｓ_ｉ（η）（ｉ＝１，２，３）は、位相中心Ｐ_ｉが（Ｖ_ｒη，０）の位置にある時刻における観測信号である。このため、受信信号ｓ_２（η）は、時刻ηにおける観測信号ではなく、η＋Δη_１における信号である。同様に、受信信号ｓ_３（η）は、η＋Δη_２における信号である。ｎ_１（η），ｎ_２（η），ｎ_３（η）は時刻ηにおける雑音である。A signal obtained by transmitting a signal from the transmission / reception antenna 106, reflected by the movement target 300, and range-compressed by the transmission / reception antenna 106, the reception antenna 107a, and the reception antenna 107b is expressed by the following equation.

Here, a ₁ (η), a ₂ (η), and a ₃ (η) are amplitudes of received signals at the transmitting / receiving antenna 106, the receiving antenna 107a, and the receiving antenna 107b, respectively. The signal S _i (η) (i = 1, 2, 3) is an observation signal at a time when the phase center P _i is at the position of (V _r η, 0). Therefore, the reception signal s ₂ (η) is not an observation signal at time η but a signal at η + Δη ₁ . Similarly, the received signal s ₃ (η) is a signal at η + Δη ₂ . n ₁ (η), n ₂ (η), and n ₃ (η) are noises at time η.

In the observation of the moving target detection apparatus according to the first embodiment, pulses are transmitted at a certain cycle (this is called a pulse repetition cycle). Since the transmitted pulse reflected in the observation range including the moving target 300 is received by the transmission / reception antenna 106, the reception antenna 107a, and the reception antenna 107b, the signals actually observed are s ₁ (η) and s ₂ ( η) and s ₃ (η) are discretized with a pulse repetition period. In this specification, s ₁ (η), s ₂ (η), and s ₃ (η) are used unless particularly confusing. As a continuous signal. However, when s ₂ (η) and s ₃ (η) are obtained, it should be noted that signal interpolation processing is required.

The phase difference between the signal s ₁ (η), the signal s ₂ (η), and the signal s ₃ (η) is calculated as shown in the following equation by causing the signals to interfere as in the conventional ATI method.

R ₂ (η) −R ₁ (η) in the above equation (8) is a _{value obtained} by transmitting a radio wave from the transmission / reception antenna 106 from the time when the transmission / reception antenna 106 is located at (V _rη , 0, 0), and receiving antenna 107a. 3 represents a change in distance that occurs due to the movement of the moving target 300 to the time difference Δη ₁ until the position of the phase center when the radio wave is received _reaches the position of (V _rη , 0, 0). Further, R ₃ (η) −R ₂ (η) is a case where a radio wave is transmitted from the transmission / reception antenna 106 at a time at a position of (V _rη , 0, 0) and then received by the reception antenna 107a. _Until the position of the phase center in the case of receiving the radio wave by the receiving antenna 107b _reaches the position of (V _rη , 0, 0) after the position of the phase center of (V _rη , 0, 0) is _reached . Represents a change in distance generated by the movement of the moving target 300 during the time Δη ₂ −Δη ₁ . Further, R ₃ (η) −R ₁ (η) is a _{value obtained} by transmitting a radio wave from the transmission / reception antenna 106 at a time when the transmission / reception antenna 106 is located at (V _rη , 0, 0) and This is a distance change caused by the movement of the moving target 300 to the time difference Δη ₂ until the position of the phase center at the time of reception _reaches the position (V _rη , 0, 0).

In other words, the phase differences Φ ₁₂ (η), Φ ₂₃ (η), and Φ ₁₃ (η) shown in the above equation (8) indicate that the movement target 300 is Δη ₁ , Δη ₂ −Δη ₁ , Δη ₂ . It is a value according to the distance traveled in time, and depends on the speed v _g0 . Here, when phase noise is negligible, that is, when the signal to noise ratio (S / N) is sufficiently high, if 2d ₁ = d ₂ , then Δη ₂ = 2Δη ₁ If the moving target 300 is moving at a constant speed v _g0 , the phase differences Φ ₁₂ (η) and Φ ₂₃ (η) have the same value. Further, Φ ₁₃ (η) / 2 = Φ ₂₃ (η) = Φ ₁₂ (η) is established.

Similarly, the phase differences Φ ₁₂ (η) and Φ ₂₃ (η) of a stationary target (in short, a target of speed v _g0 = 0 [m / s]) for which a sufficient signal-to-noise ratio is ensured are always zero. However, since the influence of phase noise cannot be ignored for a stationary target with a low signal-to-noise ratio, the phase differences Φ ₁₂ (η) and Φ ₂₃ (η) do not become zero even for a stationary target.

However, this phase difference is a random value generated by phase noise, and even when 2d ₁ = d ₂ , the phase differences Φ ₁₂ (η) and Φ ₂₃ (η) are the same as the movement target 300 moves. Unlike the phase difference caused by this, it does not become the same value. Also, Φ ₁₃ (η) / 2 = Φ ₂₃ (η) = Φ ₁₂ (η) does not hold.

It is possible to extract a movement target by making the following determination using the above properties.

The above is the principle of moving target detection by the moving target detection device according to the first embodiment.
In the first embodiment, the description is given in the form of using three antenna openings. However, the moving target detection method using the moving target detection apparatus according to the first embodiment has four or more antenna openings. However, it can be easily expanded.

Next, the movement target detection process by the signal processing unit 20 will be described.
The SAR image generation unit 21 generates SAR images using the received signals received by the respective reception antennas and the platform speed information measured by the motion measurement unit 30. Here, it is assumed that the generated SAR images are x ₁ (mΔτ, nΔη), x ₂ (mΔτ, nΔη), and x ₃ (mΔτ, nΔη). For the SAR image generation processing, for example, the methods described in Non-Patent Document 1 and the like can be used. However, these methods are publicly known, and thus the description thereof is omitted here.

ただし、ｃは光速である。Here, τ [seconds] represents the range direction axis of the SAR image in terms of time, and is called “Fast time”. η [seconds] is the observation time as described above, and represents the azimuth direction axis of the SAR image by time, and is called Slow time. The distance r [m] in the range direction, the distance a [m] in the azimuth direction, τ, and η each satisfy the following relationship.

Where c is the speed of light.

The SAR image generated in the SAR image generation unit 21 is discretized, but x ₁ (mΔτ, nΔη), x ₂ (mΔτ, nΔη), and x ₃ (mΔτ, nΔη) are in the range direction, azimuth. It is an expression that is sampled and discretized at intervals of Δτ and Δη, respectively. In addition, m and n are pixel numbers in the range direction and the azimuth direction, respectively, and take values m = 1, 2,..., M, n = 1, 2,. M and N are the numbers of pixels in the range direction and the azimuth direction, respectively.

The registration unit 22 performs resampling so as to compensate for the shift amounts Δη ₁ and Δη ₂ in the azimuth direction expressed by the equation (6), and as shown by the following equation, the SAR image z ₁ ( mΔτ, nΔη), z ₂ (mΔτ, nΔη), and z ₃ (mΔτ, nΔη) are obtained.

z ₁ (mΔτ, nΔη), z ₂ (mΔτ, nΔη), and z ₃ (mΔτ, nΔη) may have a bias error added to the amplitude and phase due to the difference in gain of the receiver. Therefore, the signal calibration unit 23 estimates and compensates for each phase and amplitude bias error from the ratio between the SAR images after alignment. _{z 2 (mΔτ, nΔη) z} 1 (mΔτ, nΔη) for the average value of the ratio _{of, z 3 (mΔτ, nΔη)} z 1 (mΔτ, nΔη) for respectively ∈ ₁₂ the average value of the ratio of ∈ ₁₃ Then, ∈ ₁₂ and ∈ ₁₃ are defined by the following equations.

The signal calibrating unit 23 corrects the amplitude and phase imbalance between the SAR images by the following equation using the correction coefficient represented by the equation (12).

If the values of ε ₁₂ and ε ₁₃ are measured in advance as correction coefficients and can be stored in the storage device 207, it is not necessary to estimate these values using equation (12). However, in the channel imbalance correction process, when the terrain phase due to a minute difference in antenna height cannot be ignored, it is necessary to correct using, for example, the method described in Japanese Patent Application Laid-Open No. 2010-175330. In equation (13), ∈ ₁₂ and ∈ ₁₃ are described in the form of constants. However, when compensation is made including the topographic phase, ∈ ₁₂ and ∈ ₁₃ are not necessarily constant for each pixel. It is a function of the pixel number. Hereinafter, in this specification, description will be made assuming that the topographic phase is also corrected.

The movement target detection unit 24 calculates the phase difference by causing the signals of each SAR image to interfere with each other as in the following equation.

If 2d ₁ = d ₂ , then Δη ₂ = 2Δη ₁ and if the moving target 300 is moving at a constant speed v _g0 , the phase difference Φ ₁₂ (mΔτ, nΔη) and Φ ₂₃ Since (mΔτ, nΔη) has the same value, a pixel satisfying the following expression is detected as a movement target.

Φ_ｔｈは移動目標を検出するための閾値であり、制御器２０２から入力する。また、記憶装置２０７に保持するようにしても良い。In the determination according to the equation (15), the phase change of Φ ₁₂ (mΔτ, nΔη) and Φ ₂₃ (mΔτ, nΔη) due to the phase noise cannot be allowed. Therefore, the tolerance to the phase noise is improved by the threshold as in the following equation. .

Φ _th is a threshold value for detecting the moving target, and is input from the controller 202. Further, it may be held in the storage device 207.

もちろん、式（１６）のように速度の推定誤差を考慮するように拡張することも容易に可能である。The speed in the line-of-sight direction of each pixel of the SAR image calculated from the phase difference between the SAR images calculated by the above equation (17) is an estimated speed if the moving target 300 is a constant speed moving target. By performing the determination as in the following equation, the moving target can be detected even when 2d ₁ = d ₂ is not satisfied.

Of course, it is also possible to easily expand to consider the speed estimation error as shown in equation (16).

  As described above, according to the moving target detection apparatus of the first embodiment, the radar apparatus that obtains each reception signal obtained by receiving the pulse signal irradiated to the observation range with three or more antennas, and each SAR of each reception signal. Each SAR image generated by the SAR image generation unit using the SAR image generation unit that generates the image, the motion measurement unit that measures the speed of the platform on which the antenna is mounted, and the platform speed information measured by the motion measurement unit The SAR image registered in the registration unit is compared with the SAR image aligned in the registration unit, and the signal calibrating unit corrects the amplitude and phase imbalance of each SAR image, and is corrected in the signal calibrating unit. Because it includes a moving target detector that calculates a phase difference between each SAR image and detects a moving target by comparing the calculated phase difference. Without detecting a stationary target that has been erroneously detected as the movement target by the phase noise as in the prior art as the movement target, it is possible to improve the moving target detection performance.

  Further, according to the moving target detection apparatus of the first embodiment, the moving target detection unit calculates the standard deviation of the calculated phase difference, and detects the moving target by thresholding the standard deviation. The moving target detection process can be performed easily and reliably.

  Further, according to the moving target detection apparatus of the first embodiment, the moving target detection unit detects the moving target by calculating the speed in the range direction from the calculated phase difference and comparing the calculated speed values. Since it did in this way, the detection process of a movement target can be performed easily and reliably.

  Further, according to the moving target detection apparatus of the first embodiment, the moving target detection unit calculates the speed in the range direction from the calculated phase difference, calculates the standard deviation of the calculated speed, and performs threshold processing on the standard deviation. Thus, the moving target is detected, so that the moving target detection process can be performed easily and reliably.

Embodiment 2. FIG.
FIG. 4 is a hardware configuration diagram of the movement target detection apparatus according to the second embodiment.
The moving target detection apparatus shown in FIG. 4 includes a radar apparatus 10a and a signal processing unit 20a. The radar apparatus 10 a includes an excitation unit 101, an amplification unit 102, a reception unit 103, a data recording unit 104, a transmission / reception switch 105, a transmission / reception antenna 106, a reception antenna 107, and a motion measurement unit 30. The difference from the radar apparatus 10 of the first embodiment shown in FIG. 2 is that there is only one receiving antenna 107, that is, the second embodiment has two antennas having a receiving function. Since other configurations are the same as those of the first embodiment, the corresponding parts are denoted by the same reference numerals and description thereof is omitted. Note that although two antennas having a reception function are described in the second embodiment, the number is not limited as long as the number is two or more. The receiving unit 103 and the data recording unit 104 have a function of simultaneously receiving and recording data for the number of reception channels.

The configuration of the signal processing unit 20a on the drawing is the same as that of the first embodiment shown in FIG.
FIG. 5 is a functional block diagram showing a configuration for realizing the movement target detection process in the signal processing unit 20a. The signal processing unit 20a according to the second embodiment includes a sub-aperture divided type movement target detection unit 25 in place of the movement target detection unit 24 of the first embodiment. The other configuration is the same as the configuration shown in FIG. 1, and accordingly, the same reference numerals are given to the corresponding portions and the description thereof is omitted.

The sub-aperture split type movement target detection unit 25 is a processing unit configured to detect a movement target based on the phase difference for each sub-aperture, and FIG. 6 shows an internal configuration.
In FIG. 6, the sub-aperture division type moving target detection unit 25 includes an azimuth decompression unit 251, a sub-aperture division unit 252, a sub-aperture compression unit 253, a sub-aperture phase difference calculation unit 254, and a sub-aperture movement target detection unit 255. Prepare. The azimuth decompression unit 251 is a processing unit that performs azimuth decompression processing on the SAR image corrected by the signal calibration unit 23. The sub-aperture dividing unit 252 is a processing unit that divides the data that has been subjected to azimuth compression by the azimuth decompressing unit 251 into sub-apertures. The sub-aperture compression unit 253 is a processing unit that azimuth-compresses the data of each sub-aperture divided by the sub-aperture division unit 252 again. The sub-aperture phase difference calculation unit 254 is a processing unit that calculates the phase difference between the SAR images of each sub-aperture compressed by the sub-aperture compression unit 253. The sub-aperture movement target detection unit 255 is a processing unit that detects the movement target by comparing the phase differences for each sub-aperture calculated by the sub-aperture phase difference calculation unit 254.

Next, the movement target detection process of Embodiment 2 is demonstrated.
The azimuth decompression unit 251 returns the azimuth-compressed SAR image to the state before the azimuth compression by convolving the complex conjugate of the azimuth reference function used for the azimuth compression of the SAR image generation by the SAR image generation unit 21. Note that details of the azimuth compression processing and the azimuth reference function are known as described in Non-Patent Document 1, Non-Patent Document 2, and the like, and thus description thereof is omitted here.

Here, the signal after azimuth decompression output from the azimuth decompression unit 251 is expressed by the following equation.

  The sub-aperture dividing unit 252 sets a hit number corresponding to the sub-aperture to be processed in the next sub-aperture compression unit 253 for the signal of the azimuth line before azimuth compression obtained by the azimuth decompression unit 251. The hit data is extracted.

  FIG. 7 shows the relationship between the slow time hit number divided by the sub-aperture dividing unit 252 and the sub-aperture number. In FIG. 7, reference numeral 701 denotes one of SAR data obtained by solving the azimuth compression in the azimuth decompression unit 251. The horizontal axis η [seconds] is a time (slow time) representing the axis in the azimuth direction. In the sub-aperture compression unit 253, a signal in a range surrounded by a broken line is cut out from the SAR data after azimuth decompression, and azimuth compression processing is performed again. Here, the range surrounded by the broken line that is cut out is called a sub-aperture. As shown in FIG. 7, the sub-aperture compression unit 253 applies azimuth compression processing to each extracted signal while moving the sub-aperture in the azimuth time axis direction (slow time) direction.

なお、Ｎ_ｓｕｂは各サブアパーチャのアジマス方向の点数、Ｎ_ｓｐはサブアパーチャ数である。As described above, the sub-aperture compression unit 253 again performs azimuth compression on the data divided by the sub-aperture division unit 252 in units of sub-apertures. An output signal obtained by azimuth compression by the sub-aperture compression unit 253 is expressed by the following equation.

Note that N _sub is the number of points in the azimuth direction of each sub-aperture, and N _sp is the number of sub-apertures.

なお、ｔｈ_ｓｕｂは移動目標を算出するための閾値であり、制御器２０２による入力や、記憶装置２０７に予め保持させた値などで設定するものであり、その手段は問わない。

Note that th _sub is a threshold value for calculating the movement target, and is set by an input from the controller 202 or a value stored in the storage device 207 in advance, and any means can be used.

  In the second embodiment, two or more SAR antennas are described. However, as described above, the same processing is possible even with three or more reception antennas, and the extension is easy.

  As described above, according to the moving target detection apparatus of the second embodiment, the radar apparatus that obtains each received signal obtained by receiving the pulse signal irradiated to the observation range with two or more antennas, and each SAR of each received signal. Each SAR image generated by the SAR image generation unit using the SAR image generation unit that generates the image, the motion measurement unit that measures the speed of the platform on which the antenna is mounted, and the platform speed information measured by the motion measurement unit The SAR image registered in the registration unit is compared with the SAR image aligned in the registration unit, and the signal calibrating unit corrects the amplitude and phase imbalance of each SAR image, and is corrected in the signal calibrating unit. The azimuth decompression unit that performs azimuth decompression processing on the SAR image, and the azimuth decompression data that has been decompressed by the azimuth decompression unit Phase difference between the SAR images of the sub-aperture dividing unit, the sub-aperture compressing unit that again azimuth-compresses the data of each sub-aperture divided by the sub-aperture dividing unit, and the SAR image of each sub-aperture compressed by the sub-aperture compressing unit Since the sub-aperture phase difference calculation unit for calculating the phase difference for each sub-aperture calculated by the sub-aperture phase difference calculation unit is provided, the sub-aperture movement target detection unit for detecting the movement target is provided. A stationary target that has been erroneously detected as a moving target due to phase noise as in the prior art is not detected as a moving target, and the moving target detection performance can be improved. In addition, it is possible to detect a moving target by providing at least two receiving antennas, and it is possible to simplify the system and reduce the cost. Furthermore, by increasing the number of sub-apertures to be divided by the sub-aperture dividing unit, it is possible to increase the number of phase difference samples used for moving target detection without increasing the receiving antenna, and the resistance to phase noise is increased. The detection performance of the moving target can be improved.

  Further, according to the moving target detection device of the second embodiment, the sub-aperture moving target detection unit calculates the speed in the range direction from the phase difference between the sub-apertures, and compares the calculated speed values. Thus, the moving target is detected, so that the moving target can be detected easily and reliably.

  Further, according to the moving target detection apparatus of the second embodiment, the in-sub-aperture moving target detection unit calculates the speed in the range direction from the phase difference between the sub-apertures, and calculates the standard deviation value of the calculated speed. Since the moving target is detected by the threshold processing, the moving target detection process can be performed easily and reliably.

Embodiment 3 FIG.
FIG. 9 is a functional block diagram illustrating a configuration for realizing the movement target detection process in the movement target detection apparatus according to the third embodiment. Here, the hardware configuration of the moving target detection apparatus in the third embodiment is the same as that in the second embodiment shown in FIG. That is, the configuration shown in FIG. 9 shows functional blocks realized by the processor 201 shown in FIG.
The moving target detection apparatus according to the third embodiment includes a difference image sub-aperture divided moving target detector 27 instead of the sub-aperture divided moving target detector 25 of the second embodiment. Further, a difference image calculation unit 26 for providing a difference image to the difference image sub-aperture divided movement target detection unit 27 is provided. The difference image calculation unit 26 is configured to perform a clutter suppression process on each SAR image corrected by the signal calibration unit 23 to calculate a difference image of the SAR image. Since the SAR image generation unit 21, the registration unit 22, and the signal calibration unit 23 are the same as those in the first and second embodiments, description thereof is omitted here.

  FIG. 10 is a configuration diagram of the difference image sub-aperture division type moving target detection unit 27. The difference image sub-aperture division type movement target detection unit 27 includes a difference image decompression unit 271, a sub-aperture division unit 252, a difference image sub-aperture compression unit 272, a difference image sub-aperture phase difference calculation unit 273, and movement within the difference image sub-aperture. A target detection unit 274 is provided. The difference image decompressing unit 271 is a processing unit that performs azimuth decompression processing on the difference image calculated by the difference image calculating unit 26. The sub-aperture dividing unit 252 is a processing unit that divides the difference image that has been subjected to azimuth compression by the difference image decompressing unit 271 into sub-apertures, and is similar to the sub-aperture dividing unit 252 of the second embodiment. The difference image sub-aperture compression unit 272 is a processing unit that azimuth-compresses the difference image of each sub-aperture divided by the sub-aperture division unit 252 again. The difference image sub-aperture phase difference calculation unit 273 is a processing unit that calculates the phase difference between the difference images of the sub-apertures that have been azimuth-compressed by the difference image sub-aperture compression unit 272. The difference image sub-aperture movement target detection unit 274 is a processing unit that detects the movement target by comparing the phase differences of the sub-apertures calculated by the difference image sub-aperture phase difference calculation unit 273.

本処理は、ＳＡＲ−ＤＰＣＡ（Ｄｉｓｐｌａｃｅｄ Ｐｈａｓｅ Ｃｅｎｔｅｒ Ａｎｔｅｎｎａ）処理として、例えば非特許文献２に記載されているように公知であるため、ここでの説明は省略する。Next, the movement target detection process of Embodiment 3 is demonstrated.

Since this processing is known as SAR-DPCA (Displaced Phase Center Antenna) processing, as described in Non-Patent Document 2, for example, description thereof is omitted here.

  The difference image Δz (mΔτ, nΔη) obtained by the difference image calculation unit 26 is suppressed because a signal having a high signal-to-noise ratio is not easily influenced by phase noise. On the other hand, the target signal having a low signal-to-noise ratio affected by the moving target and the phase noise remains without being suppressed.

The difference image decompression unit 271 compresses the difference image Δz (mΔτ, nΔη) obtained by the difference image calculation unit 26 by the SAR image generation unit 21 in the same manner as the azimuth decompression unit 251 in the second embodiment. Uncompress azimuth compression and return to the state before azimuth compression.
Here, the signal after azimuth decompression output from the differential image decompression unit 271 is expressed by the following equation.

  Similar to the sub-aperture dividing unit 252 of the second embodiment, the sub-aperture dividing unit 252 uses the hit corresponding to the sub-aperture from the signal Δs (mΔτ, nΔη) that has been decompressed in the azimuth direction by the differential image decompressing unit 271. Extract number data.

Similar to the sub-aperture compression unit 253 in the second embodiment, the difference image sub-aperture compression unit 272 applies azimuth compression processing again to the signal for each sub-aperture decompressed in the azimuth direction, and compresses the signal in the azimuth direction. . The signal after azimuth compression of the difference image for each sub-aperture is expressed by the following equation.

さらに、実施の形態２におけるサブアパーチャ内位相差算出部２５４と同様に位相のアンラップを解く。

Further, similarly to the in-sub-aperture phase difference calculation unit 254 in the second embodiment, the phase unwrapping is solved.

  Next, the phase difference data of each sub-aperture obtained by the difference image sub-aperture phase difference calculation unit 273 is output to the difference image sub-aperture movement target detection unit 274. Then, the difference image sub-aperture moving target detection unit 274 can detect the moving target by extracting the pixel where the moving target exists from the phase difference for each sub-aperture.

  In the third embodiment, two or more SAR antennas have been described. However, as described above, the same processing is possible even with three or more reception antennas, and the extension is easy.

  As described above, according to the moving target detection apparatus of the third embodiment, the radar apparatus that obtains each received signal obtained by receiving the pulse signal irradiated to the observation range with two or more antennas, and each SAR of each received signal. Each SAR image generated by the SAR image generation unit using the SAR image generation unit that generates the image, the motion measurement unit that measures the speed of the platform on which the antenna is mounted, and the platform speed information measured by the motion measurement unit The SAR image registered in the registration unit is compared with the SAR image aligned in the registration unit, and the signal calibrating unit corrects the amplitude and phase imbalance of each SAR image, and is corrected in the signal calibrating unit. A difference image calculation unit that performs a clutter suppression process on each SAR image to calculate a difference image of the SAR image, and a difference image calculation unit The difference image decompression unit that performs azimuth decompression processing on the difference image, the sub-aperture division unit that divides the difference image that has been subjected to azimuth compression by the difference image decompression unit into sub-apertures, and each sub-aperture divided by the sub-aperture division unit A difference image sub-aperture compression unit that azimuth-compresses the difference image again, a phase difference calculation unit within the difference image sub-aperture that calculates a phase difference between the difference images of the sub-apertures compressed by the difference image sub-aperture compression unit, and a difference It is equipped with a differential image sub-aperture moving target detection unit that detects the moving target by comparing the phase difference for each sub-aperture calculated by the image sub-aperture phase difference calculation unit. Moving target detection performance without detecting a stationary target that was erroneously detected as a target as a moving target It is possible to above. In addition, during the azimuth decompression process, a moving target signal or a stationary target signal with a low signal-to-noise ratio is buried in a stationary target signal with a high signal-to-noise ratio, and detection accuracy is reduced. Therefore, the detection accuracy of the moving target can be improved.

Embodiment 4 FIG.
FIG. 11 is a functional block diagram illustrating a configuration for realizing the movement target detection process in the movement target detection device according to the fourth embodiment. Here, the hardware configuration of the moving target detection apparatus in the fourth embodiment is the same as that of the second embodiment shown in FIG. That is, the configuration shown in FIG. 11 shows functional blocks realized by the processor 201 shown in FIG.
In addition to the configuration of the third embodiment illustrated in FIG. 9, the moving target detection device according to the fourth embodiment moves between the difference image calculation unit 26 and the difference image sub-aperture divided type movement target detection unit 27. A target rough detection unit 28 and a moving target peripheral region extraction unit 29 are provided. The moving target rough detection unit 28 is a processing unit that extracts moving target candidates. The movement target peripheral region extraction unit 29 is a processing unit that cuts out the signal periphery detected by the movement target rough detection unit 28. The other configuration is the same as the configuration shown in FIG.

上式（３０）に示した出力電力Ｐ（ｍΔτ，ｎΔη）は、静止目標信号を抑圧した結果の出力信号である。主な消え残り成分は、移動目標３００または信号対雑音比が低い位相雑音により位相差が生じた静止目標である。このため、この出力電力Ｐ（ｍΔτ，ｎΔη）に対して、広く知られているＣＦＡＲ（Ｃｏｎｓｔａｎｔ Ｆａｌｓｅ Ａｌａｒｍ Ｒａｔｅ）処理または閾値処理などの検出処理を適用し、移動目標信号と思われる候補の画素を検出することが可能である。なお、移動目標粗検出部２８における移動目標検出方法は、上記の方法に限る必要はなく、移動目標の候補となる画素が抽出できる手段であればその方法は問わない。The movement target rough detection unit 28 calculates the output power from the two difference images represented by the equation (26) calculated by the difference image calculation unit 26 as in the following equation.

The output power P (mΔτ, nΔη) shown in the above equation (30) is an output signal as a result of suppressing the stationary target signal. The main residual component is a moving target 300 or a stationary target in which a phase difference is caused by phase noise having a low signal-to-noise ratio. For this reason, detection processing such as CFAR (Constant False Alarm Rate) processing or threshold processing is applied to the output power P (mΔτ, nΔη), and candidate pixels that are considered to be moving target signals are applied. It is possible to detect. Note that the movement target detection method in the movement target rough detection unit 28 is not limited to the above method, and any method can be used as long as it can extract pixels that are candidates for the movement target.

なお、Ｌは切り出す範囲である。
また、これ以外の動作は実施の形態３と同様であるため、ここでの説明は省略する。The movement target peripheral area extraction unit 29 cuts out the signal of the surrounding pixels extracted as the movement target signal in the movement target rough detection unit 28. The pixel number extracted by the movement target rough detection unit 28 is assumed to be (m _t , n _t ). At this time, the movement target peripheral area extraction unit 29 cuts out pixels around the movement target as in the following equation.

Note that L is a range to be cut out.
Other operations are the same as those in the third embodiment, and a description thereof is omitted here.

  As described above, according to the moving target detection apparatus of the fourth embodiment, the moving target rough detection unit that extracts moving target candidates is provided, and the differential image decompression unit uses the signal detected by the moving target rough detection unit. Since processing is performed only for the third embodiment, in addition to the effect of the third embodiment, there is an effect that the processing speed can be increased.

  In addition, according to the moving target detection device of the fourth embodiment, the moving target peripheral region extraction unit that extracts the periphery of the signal detected by the moving target rough detection unit is provided, and the differential image decompression unit is a moving target peripheral region extraction unit. Since the processing is performed only on the extracted signal, the moving target detection processing can be speeded up.

  In the present invention, within the scope of the invention, any combination of the embodiments, or any modification of any component in each embodiment, or omission of any component in each embodiment is possible. .

  As described above, the moving target detection device according to the present invention relates to a configuration for detecting a moving target signal from signals received by a plurality of antenna apertures, and is suitable for detecting a moving target in a synthetic aperture radar. Yes.

  10, 10a Radar device, 20, 20a Signal processing unit, 21 SAR image generation unit, 22 Registration unit, 23 Signal calibration unit, 24 Moving target detection unit, 25 Sub-aperture division type moving target detection unit, 26 Difference image calculation unit , 27 Difference image sub-aperture division type moving target detection unit, 28 moving target rough detection unit, 29 moving target peripheral region extraction unit, 30 motion measurement unit, 251 azimuth decompression unit, 252 sub-aperture division unit, 253 sub-aperture compression unit, 254 Sub-aperture phase difference calculation unit, 255 Sub-aperture movement target detection unit, 271 Difference image decompression unit, 272 Difference image sub-aperture compression unit, 273 Difference image sub-aperture phase difference calculation unit, 274 Movement within difference image sub-aperture Target detection unit.

Claims (7)

A radar device for obtaining each received signal obtained by receiving the pulse signal irradiated to the observation range with three or more antennas;
A SAR image generation unit that generates each SAR (Synthetic Aperture Radar) image of each received signal;
A motion measurement unit for measuring the speed of the platform on which the antenna is mounted;
A registration unit for aligning each SAR image generated by the SAR image generation unit using the velocity information of the platform measured by the motion measurement unit;
A signal calibration unit that compares the SAR images aligned in the registration unit and corrects the amplitude and phase imbalance of the SAR images;
Moving target detection for calculating a phase difference between SAR images corrected by the signal calibrating unit, calculating a standard deviation of the calculated phase difference , and detecting a moving target by performing threshold processing on the standard deviation And a moving target detecting device. A radar device for obtaining each received signal obtained by receiving the pulse signal irradiated to the observation range with three or more antennas;
A SAR image generation unit that generates each SAR (Synthetic Aperture Radar) image of each received signal;
A motion measurement unit for measuring the speed of the platform on which the antenna is mounted;
A registration unit for aligning each SAR image generated by the SAR image generation unit using the velocity information of the platform measured by the motion measurement unit;
A signal calibration unit that compares the SAR images aligned in the registration unit and corrects the amplitude and phase imbalance of the SAR images;
A movement for detecting a moving target by calculating a phase difference between the SAR images corrected by the signal calibrating unit, calculating a speed in a range direction from the calculated phase difference, and comparing the calculated speed values. A moving target detection apparatus comprising: a target detection unit. 3. The moving target detection apparatus according to claim 2, wherein the moving target detection unit detects a moving target by calculating a standard deviation of the calculated speed in the range direction and performing threshold processing on the standard deviation. A radar device for obtaining each received signal obtained by receiving two or more antennas with a pulse signal irradiated to the observation range;
A SAR image generation unit that generates each SAR image of each received signal;
A motion measurement unit for measuring the speed of the platform on which the antenna is mounted;
A registration unit for aligning each SAR image generated by the SAR image generation unit using the velocity information of the platform measured by the motion measurement unit;
A signal calibration unit that compares the SAR images aligned in the registration unit and corrects the amplitude and phase imbalance of the SAR images;
An azimuth decompression unit that performs azimuth decompression processing on the SAR image corrected by the signal calibration unit;
A sub-aperture dividing unit that divides the azimuth compressed data in the azimuth decompression unit into sub-apertures;
A sub-aperture compression unit that azimuth-compresses again the data of each sub-aperture divided by the sub-aperture division unit;
A sub-aperture phase difference calculation unit that calculates a phase difference between SAR images of each sub-aperture compressed by the sub-aperture compression unit;
A sub-aperture moving target detector that calculates a speed in the range direction from the phase difference between the sub-apertures calculated by the sub-aperture phase difference calculator, and detects a moving target by comparing the calculated speed values. A moving target detection apparatus comprising: 5. The moving target detection device according to claim 4, wherein the sub-aperture moving target detection unit detects a moving target by performing threshold processing on the calculated standard deviation value of the speed in the range direction . A radar device for obtaining each received signal obtained by receiving two or more antennas with a pulse signal irradiated to the observation range;
A SAR image generation unit that generates each SAR image of each received signal;
A motion measurement unit for measuring the speed of the platform on which the antenna is mounted;
A registration unit for aligning each SAR image generated by the SAR image generation unit using the velocity information of the platform measured by the motion measurement unit;
A signal calibration unit that compares the SAR images aligned in the registration unit and corrects the amplitude and phase imbalance of the SAR images;
A difference image calculation unit that performs a clutter suppression process on each SAR image corrected by the signal calibration unit to calculate a difference image of the SAR image;
A moving target rough detection unit that extracts moving target candidates from the difference image calculated by the difference image calculation unit;
A differential image decompression unit that performs azimuth decompression processing on the differential image calculated by the differential image calculation unit only for the signal detected by the moving target coarse detection unit ;
A sub-aperture dividing unit that divides the difference image obtained by solving the azimuth compression in the difference image decompression unit into sub-apertures;
A difference image sub-aperture compressor that azimuth-compresses the difference image of each sub-aperture divided by the sub-aperture divider;
A difference image sub-aperture phase difference calculation unit for calculating a phase difference between the difference images of the sub-apertures compressed by the difference image sub-aperture compression unit;
A moving target detection comprising: a difference image sub-aperture moving target detection unit that detects a moving target by comparing the phase difference of each sub-aperture calculated by the difference image sub-aperture phase difference calculating unit. apparatus. A moving target peripheral region extraction unit that cuts out the periphery of the signal detected by the moving target rough detection unit;
The moving target detection apparatus according to claim 6, wherein the difference image decompressing unit performs processing only on the signal cut out by the moving target peripheral region extracting unit.

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