JP2015099097A - Synthetic aperture radar device and image processing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a synthetic aperture radar device configured to reliably detect a moving target even if image shift occurs in the moving target.SOLUTION: In acquiring an image while electronically scanning-controlling a beam direction as a moving body moves, an image signal is acquired by performing synthetic aperture processing at a receiving cycle according to a moving axis of the moving body. From the image signal acquired according to the moving axis, reference signals are generated on the basis of N (N is a natural number) types of speeds and accelerations, within a range of a moving speed and acceleration of an observation target. The image signal is corrected by use of the reference signal. In the corrected image signal, a local maximum value exceeding a predetermined amplitude threshold is extracted. A reference signal of the N reference signals having the maximum amplitude of the local maximum value is searched. At least one of a value of a target range-cross range with respect to the searched reference signal, the amplitude of the reference signal, speed, and acceleration is output as an observation value of a moving target.

Description

  The present embodiment relates to a synthetic aperture radar apparatus that is mounted on a moving body and images a moving target and an image processing method thereof, and particularly in an environment where a fixed target and a moving target are mixed, a fixed target using synthetic aperture processing. And technology for identifying and outputting moving targets.

  In a conventional synthetic aperture radar apparatus, in the case of a fixed target, in a SAR (Synthetic Aperture Radar) process, the position is fixed within the synthetic aperture time. Can be combined so that the maximum vector is obtained, and imaging can be performed at the correct position (see Non-Patent Documents 1, 2, and 3).

  On the other hand, in the case of a moving target, since the position changes within the synthetic aperture time, the phase changes and a wavefront shift of the large aperture array occurs, and an image is generated at a position shifted from the correct position. This is a phenomenon called image shift. When a moving target is superimposed on a fixed target, there is a problem that a large error occurs in the relative positional relationship between the fixed target and the moving target (see Non-Patent Document 4). In addition, when there are a plurality of moving targets, in the correlation process with the previous wake, the correspondence between the wake and the observed value may be wrong, and tracking may be lost.

SAR method (range compression): Ouchi, “Basics of Synthetic Aperture Radar for Remote Sensing”, Tokyo Denki University Press, pp.131-149 (2003) SAR method (Az compression): Ouchi, “Basics of Synthetic Aperture Radar for Remote Sensing”, Tokyo Denki University Press, pp.171-178 (2003) SAR method (large aperture array synthesis, spotlight SAR): Yoshida, 'Revised radar technology', IEICE, pp.280-283 (1996) SAR method (moving object image shift): Ouchi, “Basics of Synthetic Aperture Radar for Remote Sensing”, Tokyo Denki University Press, pp.218-223 (2003) SAR processing method (polar format conversion reconstruction processing): MEHRDAD SOUMEKH, “Synthetic Aperture Radar Signal Processing”, JOHN WILEY & SONS, INC., Pp.319-325 (1999) Tracking filter (αβ, etc.): Yoshida, 'Revised radar technology', IEICE, pp.264-267 (1996) Tracking filters (αβ filter, αβγ filter): Samuel S. Blackman, “Multiple-Target Tracking with Radar Applications”, ARTECH HOUSE, pp. 21-23 (1986) Tracking filter (Kalman filter): K.V.Ramachandra, “Kalman filtering Techniques for Radar Tracking”, Marcel Dekker, Inc., pp.19-25 (2000)

  As described above, the conventional synthetic aperture radar apparatus has a problem that a large error occurs in the relative positional relationship between the fixed target and the moving target when the moving target is superimposed on the fixed target. In addition, when there are a plurality of moving targets, in the correlation process with the previous wake, the correspondence between the wake and the observed value may be wrong, and tracking may be lost.

  The present embodiment has been made in view of the above problems, and a synthetic aperture radar device capable of displaying a correct position even when there is a moving target and performing correlation tracking with high accuracy even when there are a plurality of moving targets, and its An object is to provide an image processing method.

  In order to solve the above-described problem, the synthetic aperture radar apparatus and the image processing method thereof according to the present embodiment have N patterns within the range of the moving speed and acceleration of the observation target with respect to the input signal acquired according to the flight axis. A reference signal is generated based on the speed and acceleration of the input signal, the input signal is corrected using the reference signal, a maximum value exceeding a predetermined amplitude threshold is extracted from each synthesis processing result, and the target range-cross The range value and at least one of the amplitude, speed, and acceleration of the reference signal are output as the observed value.

The block diagram which shows the structure of the synthetic aperture radar apparatus which concerns on 1st Embodiment. The flowchart which shows the flow of a process of the signal processing part of the apparatus shown in FIG. The conceptual diagram which shows the positional relationship of the body flight axis (flight path | route) and imaging range for demonstrating the synthetic | combination opening process of the apparatus shown in FIG. The conceptual diagram which shows the component of the velocity vector with respect to the radial direction which goes to the moving target's speed vector and moving target in the apparatus shown in FIG. The figure which shows the SAR image formed for every reference signal in the apparatus shown in FIG. The figure for demonstrating the correction | amendment process when a movement target is extracted by the XY coordinate system in flight at the speed V in the apparatus shown in FIG. FIG. 7 is a diagram showing a comparison between a case where image shift correction is not performed and a case where correction is performed in the XY coordinate system shown in FIG. 6. The block diagram which shows the structure of the synthetic aperture radar apparatus which concerns on 2nd Embodiment. The flowchart which shows the flow of a process of the signal processing part of the apparatus shown in FIG. The block diagram which shows the structure of the synthetic aperture radar apparatus which concerns on 3rd Embodiment. 11 is a flowchart showing a flow of processing of a signal processing unit of the apparatus shown in FIG. The figure which shows the mode of the observed value of each reference signal in each receiving cycle in the apparatus shown in FIG. The figure for demonstrating the correlation tracking process with respect to the observation result shown in FIG. 12 in the apparatus shown in FIG. The block diagram which shows the structure of the synthetic aperture radar apparatus which concerns on 4th Embodiment. The flowchart which shows the flow of a process of the signal processing part of the apparatus shown in FIG.

  Hereinafter, embodiments will be described with reference to the drawings.

(First embodiment)
With reference to FIG. 1 thru | or FIG. 7, the synthetic aperture radar apparatus mounted in the aircraft which concerns on 1st Embodiment is demonstrated.

  FIG. 1 is a block diagram showing the system configuration. In FIG. 1, an antenna 1 is a phased array antenna in which a plurality of antenna elements are arranged to form a large aperture array, and a transmission pulse signal (hereinafter referred to as “transmission pulse signal”) having a specific frequency repeatedly supplied from a transmission / reception unit 21 of the transceiver 2. A PRF (Pulse Repetition Frequency) signal) is transmitted in a designated direction and the reflected wave is received. The transmission / reception unit 21 performs phase control on the signals received by the plurality of antenna elements of the antenna 1 according to instructions from the beam control unit 22 and combines them to form a reception beam in a range to be imaged. A reception signal obtained by the reception beam is sent to the signal processor 3.

  The signal processor 3 includes an AD (Analog-Digital) conversion unit 31, a reference signal correction unit 32, a range compression unit 33, an Az compression unit 34, a maximum value extraction unit 35, an observation value calculation unit 36, and a movement target output unit 38. Is provided.

  The AD conversion unit 31 converts the PRF received signal supplied from the transceiver 2 into a digital signal, and the conversion result is sent to the SAR processing unit by the reference signal correction unit 32, the range compression unit 33, and the Az compression unit 34. Sent.

  In the SAR processing unit, the reference signal correction unit 32 generates N reference signals based on the assumed target speed, the speed within the range of acceleration, and the acceleration, and corrects the input signal based on each reference signal. The range compressor 33 pulse-compresses the digitized aperture array PRF received signal in the range (distance) direction for each synthetic aperture reception cycle. The Az compression unit 34 performs pulse compression in the azimuth angle direction. Thereby, the resolution in the range direction and the resolution in the cross range direction are improved.

  The maximum value extraction unit 35 extracts the maximum value of the reception intensity for each reception cycle from the SAR processing output. The observation value calculation unit 36 selects an image of the reference signal that is the maximum value from the maximum values obtained by the maximum value extraction unit 35, and sets the position of the maximum value as an observation value. This observation value includes the speed and acceleration of the reference signal in addition to the position, and these are included and output as observation values. The moving target output unit 37 compares the observation value calculation result with a threshold, and determines that it is a fixed target if it is less than the threshold, suppresses it, and if it exceeds the threshold, determines that it is a moving target, and moves target information. Output as.

  FIG. 2 is a flowchart showing a specific processing flow of the signal processor 3 in the radar apparatus having the above-described configuration. First, the PRF reception signal of the aperture array is received by PRF transmission / reception of the transmitter / receiver 2 (step S1), and converted into a digital signal by the AD converter 31 (step S2). Here, the reference signal correction unit 32 generates N reference signals based on the assumed target speed, the speed within the range of acceleration, and the acceleration, and corrects the input signal by each reference signal (step) S3). Subsequently, SAR processing is performed by performing range compression and Az compression by the range compression unit 33 and the Az compression unit 34 (steps S4 and S5).

  Thereafter, the local maximum extraction unit 35 extracts cells having the local maximum value for each SAR reception cycle and fills the surroundings with 0 (step S6), and compares the local maximum values to extract the cell having the maximum value. (Step S7). Here, it is determined whether or not the maximum value exceeds the amplitude threshold (step S8), and if not (NO), the processing of steps S6 to S8 is repeated. If the maximum value exceeds the amplitude threshold in step S8 (YES), the image of the reference signal from which the maximum value is obtained is selected, and the position, speed, and acceleration of the maximum value are acquired as observed values. Is saved as a target (step S9).

  Here, it is determined whether or not the processing has been completed for the speeds and accelerations of all N reference signals. If there is an unprocessed reference signal (NO), the process returns to step S3 and the above processing is repeated (step S10). ). When processing is completed for all N reference signals, after selecting the reference signal and calculating the observed value (step S11), the target whose speed exceeds the speed threshold is moved from the stored targets for each speed. The target is extracted (step S12), and the process proceeds to the next cycle.

  The configuration and processing contents will be described more specifically.

  First, SAR processing in the above-described synthetic aperture radar apparatus mounted on an aircraft will be described. In the case of the spotlight SAR (see Non-Patent Document 3), as shown in FIG. 3, in the aircraft on the flight path, the on-board radar device always irradiates the real aperture beam toward the imaging range, and the synthetic aperture time ( In one cycle), data is acquired in units of range cells in the PRI for each pulse transmitted at the PRI interval. SAR processing is performed using the acquired data to obtain a SAR image. FIG. 3 is a diagram in the case of a spotlight SAR, but other methods such as a strip map SAR for observing the side may be used as long as a SAR image can be obtained.

In the system of the radar apparatus shown in FIG. 1, in the transmission / reception signal by the antenna 1, the beam control unit 22 directs the beam to a range to be imaged, and the received signal is converted to a digital signal by the AD conversion unit 31, Input to the reference signal correction unit 32. The reference signal correction unit 32 generates N reference signals based on the assumed target speed, the speed within the range of acceleration, and the acceleration, and corrects the input signal by each reference signal. As the N reference signals, the speed and acceleration ranges may be set at equal intervals or may be set at unequal intervals by weighting. The reference signal equation is shown below.

If the input signal is Sin, the corrected input signal can be expressed by the following equation.

  FIG. 4A shows the definition of the coordinate system. FIG. 4B shows the velocity vector component of the moving target and the velocity vector component in the radial direction from the radar toward the moving target. When a velocity vector is handled as a reference signal, the distance change with respect to the component in the radial direction expressed as a phase change corresponds to equation (1), and the input signal is multiplied by the inverse component (negative sign) of this phase component. Then, the corrected input signal of equation (2) is obtained.

  For each of the N reference signals, the SAR process is performed using the corrected input signal. The SAR processing is performed by a range compression unit 33 (see Non-Patent Document 1) that increases the range resolution by pulse compression or the like and an Az compression unit 34 (see Non-Patent Document 2) that increases the resolution in the cross range direction by synthesizing a large aperture array. There are various methods for simplifying and speeding up the basic processing, and typical processing includes polar format conversion reconstruction processing (see Non-Patent Document 5). Since details of the processing method are described in the literature, they are omitted in this description.

  N SAR images are arrays of amplitude intensities and are expressed as I (n) (x, y). Here, x is a range and y is a cross range. The appearance of the images formed by the reference signals 1 (V1, A1), 2 (V2, A2), and 3 (V3, A3) is as shown in FIGS. 5A, 5B, and 5C, for example. become. As described above, the amplitude of the target having the velocity and acceleration with which the reference signal is matched increases for each reference signal.

  Next, a maximum value is extracted by the maximum value extraction unit 35 from I (n) (x, y). As this method, for example, the following procedure is used.

(1) With the intensity of the I (n) (x, y) image as Iamp (n) (x, y), the maximum value of Iamp (n) is calculated, and the maximum value x, y is extracted.
(2) The intensity of a predetermined range around x and y is set to zero.
Thereafter, (1) and (2) are repeated until the maximum value becomes equal to or smaller than the predetermined amplitude, and Iamp (n) (x, y) that becomes the maximum value is extracted.

  In this process, as shown in FIG. 2, the local maximum values for the N reference signals are obtained, the image of the reference signal having the maximum value is selected, and the position of the local maximum value is set as the observed value. In addition to the position, this observation value includes the speed and acceleration of the reference signal, and these are output as observation values.

  In this processing, the input signal is corrected using the reference signal and the SAR processing is performed, which is equivalent to correcting the phase plane deviation in the case of the moving target using the reference signal. If there is no correction by the reference signal, an image shift occurs. However, since the phase plane deviation is corrected by using the reference signal, an image without image shift is selected for a target that is matched with the reference signal. Can be output. Moreover, an observed value can be extracted by the above-described maximum value processing using this image.

  The processing content of the image shift correction will be described with reference to FIGS.

  FIG. 6 shows a moving target having a predetermined velocity vector in the beam pointing direction (squint angle) of the observation beam in the range X-cross range Y coordinate system in a synthetic aperture radar apparatus mounted on an aircraft flying at a velocity V. The correction process in the case of being performed is shown. Assuming that a moving target having a predetermined velocity vector is extracted as shown in FIG. 6A, the observed image is affected by the phase plane shift due to the velocity vector as shown in FIG. 6B. An image shift occurs. Therefore, image shift correction of the observed image is performed in consideration of the fact that the observation phase is determined based on the relationship between the phase plane when the target is fixed and the phase plane shift caused by the target velocity vector.

  FIG. 7 shows a comparison between the cases (a1) and (a2) in which image shift correction is not performed and the cases (b1) and (b2) in which correction is performed in the XY coordinate system shown in FIG. First, when correction is not performed, as shown in FIG. 7 (a1), when the phase plane (1) when the target is fixed and the phase plane deviation (2) due to the target velocity vector are taken into account, the observed phase is (1) + (2), and the synthetic aperture radar beam shifts as shown in FIG. 7 (a2). Therefore, as shown in FIG. 7 (b1), the phase correction of the phase plane deviation caused by the target velocity vector is performed. Thereby, according to this embodiment, the synthetic aperture beam can be shift-corrected in the original direction as shown in FIG.

  In FIG. 7, the target observation phase is described by a curve. However, when performing SAR image processing, a reference signal having a characteristic opposite to that of this curve (target position and phase curve due to aircraft flight) is used. And Az compression processing is performed.

  Before correction, the wavefront of the large aperture array is shifted due to the velocity vector of the moving target and a shift occurs in the SAR beam pointing direction. Therefore, if the shift amount is calculated, an image of the moving target can be generated at the normal position.

  In this embodiment, range compression and Az compression are included. However, in the case of a general pulse radar, this embodiment corrects an input signal using a reference signal even when there is no range compression or Az compression. Needless to say, this method can be applied.

(Second Embodiment)
With reference to FIGS. 8 to 9, an airborne synthetic aperture radar apparatus according to the second embodiment will be described.

  In the first embodiment, the correction method using the N reference signals has been described. However, when the target speed and acceleration ranges are wide, the value of N increases and the processing scale increases. Therefore, the second embodiment aims to reduce the processing scale in order to avoid this.

  FIG. 8 is a block diagram showing a system configuration of the second embodiment, and FIG. 9 is a flowchart showing a processing flow of the signal processor 3 shown in FIG. 8 and 9, the same parts as those in FIGS. 1 and 2 are denoted by the same reference numerals, and different parts will be described here.

  In the second embodiment, the difference from the first embodiment is that, as shown in FIG. 8, a reference signal selection unit 38 is provided, and the reference is made based on the observation value of the previous cycle obtained by the observation value calculation unit 36. This is to select a reference signal in the current cycle of the signal correction unit 32. Specifically, in the second embodiment, the processing within the synthetic aperture length of 1 CPI (Coherent Pulse Interval) is set as one cycle, and the target signal is extracted in the processing of the previous cycle (p-1) as Nprv reference signals. Is used as a reference, and ± ΔN reference signals as a set of speed ± ΔV and acceleration ± ΔA are selected around the speed V0 and acceleration A0 of the standard reference signal (step S13 in FIG. 9), and the current cycle (p) Perform the process.

  As described above, according to the present embodiment, by performing narrowing down with reference signals in the previous cycle with respect to the original N reference signals, processing with fewer reference signals is performed, so the processing scale is reduced. be able to.

(Third embodiment)
With reference to FIG. 10 thru | or FIG. 13, the synthetic aperture radar apparatus mounted on the aircraft which concerns on 3rd Embodiment is demonstrated.

  FIG. 10 is a block diagram showing a system configuration of the third embodiment, and FIG. 11 is a flowchart showing a processing flow of the signal processor 3 shown in FIG. 10 and 11, the same parts as those in FIGS. 1 and 2 are denoted by the same reference numerals, and different parts will be described here.

  In the present embodiment, in order to improve the position, speed, and acceleration accuracy of the target observation value of the first embodiment or the second embodiment, correlation tracking is performed using the observation value between cycles.

  That is, in FIG. 10, the maximum value extraction unit 35 takes a local maximum value (xi, yi) (i) for a SAR image of a certain cycle k obtained by the compression processing of the range compression unit 33 and the Az compression unit 34. = 1 to Q) is extracted, the correlation tracking unit 39 performs a cycle tracking process for each observation point (xi, yi) calculated by the observed value calculation unit 36, and the movement target output unit 37 To determine the moving target.

  In FIG. 11, when a reference signal is selected in step S11 and an observed value is calculated, grouping (Gr) is performed for each reference signal (step S14), and correlation tracking processing is performed for each grouped reference signal. (Step S15), the process proceeds to the movement target output process of Step S12.

  As the correlation tracking method, various combinations are conceivable as correlation processing and tracking processing (αβ filter, Kalman filter, etc.). Here, in order to simplify the explanation, the correlation processing is NN (Nearest Neighbor) processing, tracking processing. Adopt an αβ filter (see Non-Patent Document 6).

  FIG. 12 shows the state of the observed value of each reference signal in each reception cycle, and FIG. 13 shows the explanation of correlation tracking. Correlation tracking is performed for each reference signal in FIG. In FIG. 12, (a), (b), and (c) are observation results of reference signals 1, 2, and 3 in cycle K, respectively, and (d), (e), and (f) are reference signal 1 in cycle K + 1, respectively. , 2 and 3 are shown.

The coordinates for correlation tracking are expressed in one dimension (X-axis or Y-axis only) for simplicity, but it is easy to expand to two dimensions. Further, for the sake of simplicity, the case of two states of position and velocity will be described, and the case of three states of position, velocity, and acceleration is described in Non-Patent Document 7 and the like, and thus description thereof will be omitted.

Then, it can be expressed by the following formula.

Next, the correlation tracking process will be described with reference to FIG.
First, the initial value (smooth value of the previous prediction cycle)

And In the next cycle predicted by this initial value, when there are a large number of detection targets (observed values: determined by the center of gravity by velocity grouping) (j is plural), the target having a high S / N (Signal to Noise ratio) Are sequentially subject to correlation tracking. Among these, when the NN process is adopted for the correlation, the NN observation value is selected using the prediction value of the previous cycle, the smooth value is obtained from the prediction value and the NN observation value, and further using the smooth value, the next value is obtained. Calculate the cycle prediction value. Thereafter, the correlation tracking of the detection target is realized by repeatedly executing this process.

  By the above correlation tracking process, a wake of position, velocity, acceleration smooth value, and predicted value can be output as a result of correlation tracking for each group of reference signals. When the S / N value of the observed value is low and the accuracy of the observed value is low, the accuracy can be improved by using a smooth value or a predicted value of the wake. In addition, since this correlation tracking process is performed for each reference signal, it is possible to suppress cross-correlation and erroneous tracking compared to the case where observation values are not grouped by speed and acceleration.

(Fourth embodiment)
With reference to FIG.14 and FIG.15, the synthetic aperture radar apparatus mounted on the aircraft which concerns on 4th Embodiment is demonstrated.

  FIG. 14 is a block diagram showing a system configuration of the fourth embodiment, and FIG. 15 is a flowchart showing a processing flow of the signal processor 3 shown in FIG. 14 and 15, the same parts as those in FIGS. 1 and 2, 8 and 9, 10 and 11 are denoted by the same reference numerals, and different parts will be described here.

  First, in the third embodiment, a wake calculation method using correlation tracking has been described. For the wake, velocity and acceleration can be calculated by using an α-β-γ filter (see Non-Patent Document 7) and a Kalman filter (see Non-Patent Document 8) of three states (position, velocity, acceleration). it can. Therefore, in the present embodiment, as shown in FIG. 14, in the reference signal selection unit 40, based on the processing result of the correlation tracking unit 39, the reference signal of the reference reference signal is based on Nprv reference signals of the speed and acceleration. Centering on the speed V0 and the acceleration A0, ± ΔN reference signals that are a set of the speed ± ΔV and the acceleration ± ΔA are selected (step S16 in FIG. 15), and the processing of the current cycle (p) is performed. .

  According to the present embodiment, by performing narrowing down with reference signals in the previous cycle with respect to the original N reference signals, processing with fewer N reference signals results in a reduction in processing scale. .

  In the above-described embodiment, the polar format converted image reconstruction process (see Non-Patent Document 5) is adopted as the synthetic aperture processing method. However, other synthetic aperture processing methods can be similarly implemented.

  In the above embodiment, the case of the spotlight SAR has been described. However, the present invention can also be applied to a case of a strip map SAR for side monitoring (same as side-looking mapping, see Non-Patent Document 3).

  In the above embodiment, the case of the synthetic aperture radar apparatus has been described. However, in a radar that performs coherent processing such as FFT in the CPI using a large number of pulses, the target at various speeds from fixed to high speed is discriminated. Even in this case, the present method is effective because it is a method of extracting the most consistent speed and acceleration targets by a search method of multiplication of the input signal and a plurality of reference signals.

  Moreover, although the case where velocity and acceleration are mainly used as the reference signal has been described, at least one of velocity and acceleration may be used.

  In addition, although the observation value or the wake value is output, a symbol or the like can be superimposed on the position of the observation value or the wake value on the fixed terrain SAR image corresponding to the speed 0, and the symbol can be displayed as necessary. Speed, acceleration, etc. can be displayed.

  As described above, the present embodiment is not limited to the above-described embodiment as it is, and can be embodied by modifying the components without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

  DESCRIPTION OF SYMBOLS 1 ... Antenna, 2 ... Transmitter / receiver, 21 ... Transmitter / receiver, 22 ... Beam control part, 3 ... Signal processor, 31 ... AD (Analog-Digital) converter, 32 ... Reference signal correction part, 33 ... Range compression part, 34 ... Az compressor, 35 ... maximum value extractor, 36 ... observed value calculator, 37 ... moving target extractor, 38 ... reference signal selector, 39 ... correlation tracking processor, 40 ... reference signal selector.

Claims (8)

In a synthetic aperture radar apparatus that performs synthetic aperture processing while electronically scanning the beam direction as the mounted mobile body moves,
An acquisition means for acquiring an image signal by performing the synthetic aperture processing in a reception cycle according to a movement axis of the mounted mobile body;
Generating means for generating a reference signal based on N (N is a natural number) speeds and accelerations within the range of the moving speed and acceleration of the observation target from the image signal acquired according to the moving axis by the acquiring means;
Correction means for correcting the image signal using the reference signal;
Extraction means for extracting a maximum value exceeding a predetermined amplitude threshold in the corrected image signal;
Search means for searching for a reference signal that maximizes the amplitude of the local maximum value among the N ways,
A synthetic aperture radar apparatus comprising: a target range-cross range value for the retrieved reference signal; and output means for outputting at least one of the amplitude, velocity, and acceleration of the reference signal as an observed value of the moving target.   The synthetic aperture radar apparatus according to claim 1, wherein the acquisition unit performs processing using a reference signal of velocity and acceleration within a predetermined range around the reference signal from which the target is extracted in the reception cycle.   Further, grouping is performed for each reference signal of at least one of the speed and acceleration, and correlation tracking is performed using a target output for each grouping, and at least one of position, speed, and acceleration is output as a wake value together with the observed value of the target. The synthetic aperture radar apparatus according to claim 1, further comprising a correlation tracking unit.   The correlation tracking means outputs a target observation value and a wake value by using at least one reference signal of a speed and an acceleration within a predetermined range around the speed and acceleration of the wake by the correlation tracking up to the cycle. The synthetic aperture radar device according to claim 3. In an image processing method of a synthetic aperture radar apparatus for performing synthetic aperture processing while electronically scanning a beam direction as the mounted mobile body moves,
The synthetic aperture processing in the reception cycle according to the movement axis of the mounted moving body to obtain an image signal,
From the image signal acquired according to the moving axis, a reference signal is generated based on N (N is a natural number) speeds and accelerations within the range of the moving speed and acceleration of the observation target,
Correcting the image signal using the reference signal;
In the corrected image signal, a maximum value exceeding a predetermined amplitude threshold is extracted,
Searching for a reference signal that maximizes the amplitude of the maximum value among the N ways,
An image processing method of a synthetic aperture radar apparatus that outputs at least one of a target range-cross range value with respect to the retrieved reference signal and an amplitude, velocity, and acceleration of the reference signal as an observed value of the moving target.   6. The image processing method of a synthetic aperture radar apparatus according to claim 5, wherein processing is performed using a reference signal of velocity and acceleration within a predetermined range around the reference signal from which the target is extracted in the reception cycle.   Further, grouping is performed for each reference signal of at least one of the speed and acceleration, and correlation tracking is performed using a target output for each grouping, and at least one of position, speed, and acceleration is output as a wake value together with the observed value of the target. The image processing method of a synthetic aperture radar device according to claim 5 or 6.   The correlation tracking outputs a target observation value and a wake value using at least one reference signal of a speed and an acceleration within a predetermined range centering on a wake speed and an acceleration obtained by correlation tracking up to a cycle. 7. An image processing method of the synthetic aperture radar apparatus according to 7.

Images