JP2000187074A - Radar signal processor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a radar signal processor detecting the revolution speed of a target by calculating the Doppler frequency from the Doppler history of the target for analyzing the revolution of the target and calculating optimum synthesized open time. SOLUTION: For calculating the spread of a Doppler frequency from the Doppler history of the target detected with a Doppler tracking processor 13, a Doppler frequency calculator 20 is attached. For calculating an optimum synthesized open time based on the Doppler frequency, a synthesized open time calculator 21 is attached.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radar signal processor capable of acquiring the shape of a target as image data.

[0002]

2. Description of the Related Art FIG. 15 shows a radar apparatus in which a conventional radar signal processor is incorporated as a part of components.
In the figure, 1 is a transmitter for generating a transmission pulse signal subjected to frequency modulation at a constant pulse repetition cycle, 2 is a transmission / reception switch for switching a transmission / reception circuit, 3 is a transmission pulse signal directed to a target and radiated. A transmitting / receiving antenna for receiving a reflected signal from an object, a receiver for obtaining a video signal by amplifying and phase-detecting a received signal input via a transmission / reception switch by referring to a reference signal output from a transmitter; Reference numeral 5 denotes a conventional radar signal processor, and reference numeral 6 denotes a display for displaying image data output from the radar signal processor 5. Further, in the radar signal processor 5, 7 is a range compressor for pulse-compressing the video signal using phase information subjected to frequency modulation by the transmitter 1, and 8 is a two-dimensional video signal in a pulse hit direction × range direction. , A distance tracking processor for estimating speed data of the target, and a distance calculator for calculating the distance of the target for each pulse hit in order to estimate the speed data of the target.
1 is an RMG speed calculator that performs a smoothing process for smoothing a change in the distance of the target and estimates the speed of the target.
12 is a range migration correction processor that corrects a change in the distance of movement with the movement of the target, 13 is a Doppler tracking processor that estimates velocity data of the target, and 14 is a Doppler frequency generated by the movement of the target. A phase compensation processor 15 for compensating the offset component and the primary component, and a cross-range compressor 15 for compressing the target in the cross-range direction.

Next, the operation will be described. The transmitter 1
A transmission pulse signal that has been subjected to frequency modulation at a constant pulse repetition cycle is generated, and transmitted through the transmission / reception switch 2 to the antenna 3
Output to Further, the transmitter 1 outputs a reference signal used for phase detection and timing adjustment performed by the receiver 4 to the receiver 4. The transmission / reception antenna 3 radiates the input transmission pulse signal to the target and inputs it again as a reflected signal.
The receiver 4 inputs the reflected signal via the transmission / reception switch 2, performs amplification and phase detection using the reference signal output from the transmitter 1, converts the amplified signal into a video signal, and converts the amplified signal into a video signal. Output to

[0006] The radar signal processor 5 receives the video signal and obtains image data based on the principle of inverse synthetic aperture radar. Here, the basic principle of the inverse synthetic aperture radar will be described. The image data is represented by a two-dimensional image of the target in the range direction and the cross range direction.The target is compressed in the range direction using pulse compression technology, and attention is paid to the difference in Doppler signal generated by the movement of the target. Compressed in the cross range direction. However, since the inverse synthetic aperture radar uses the motion of the target, it is necessary to correct an error factor that causes the video signal to move to a different range bin. Furthermore, it is necessary to remove the offset component and the primary component of the frequency which cause image degradation from the generated Doppler frequency. Therefore, in order to obtain a good target image, the distance tracking processor 9 and the range migration correction processor 12 correct the movement of the range bin with respect to these error factors, and the Doppler tracking processor 13 and the The phase compensation processor 14 removes the frequency offset component and the primary component. Hereinafter, these correction processes performed by the signal processor will be mainly described.

[0005] The video signal output from the excitation receiver 4 is input to the range compressor 7 and is generally used in the field of radar signal processing by referring to phase information subjected to frequency modulation by the transmitter 1. Pulse compression is performed by a matched filter method or the like. Next, the pulse-compressed video signal is temporarily stored in the two-dimensional memory 8 in the pulse hit direction × range direction, and is expanded to a plurality of range bins by the high resolution of the range compressor 7. here,
This video signal moves to a different range bin due to the movement of the target as shown in FIG. 12A, and it is necessary to correct the video signal so that it exists in the same range bin (FIG. 1).
3 (b)). Therefore, the range migration corrector 12 calculates a change in the target distance for each pulse (hereinafter, referred to as a range migration correction amount) based on the information on the speed data detected by the distance tracking processor 9 and moves the range bin. ing.

The distance tracking processor 9 estimates speed data to be output to the range migration correction processor 12 as follows. First, the distance calculator 10 detects a range bin having the largest reflected power from video signals spread over a plurality of range bins, and calculates the distance (see FIG. 2). By performing this process for each pulse hit, a change in the distance to the target is acquired and output to the RMG speed calculator 11. This distance information does not change stably due to scattering of a plurality of reflection points as shown in FIG. Therefore, R
The MG speed calculator 11 estimates the speed by performing smoothing using a process such as a least squares method or a Kalman filter.

Next, a method of removing the offset component and the primary component of the Doppler frequency which causes the deterioration of the performance of the image data will be described with reference to FIG. First, the Doppler tracking processor 13 detects the maximum amplitude point detector 1 from the video signal output from the range migration correction processor 12.
The video signal of the range bin which is the maximum point of the reflected power obtained at 0 is cut out (see FIG. 3A). Then, the video signal is Fourier-transformed at certain time intervals, and the Doppler frequency is calculated (see FIG. 3B). By performing this processing while shifting in the time direction, the Doppler history of the target is calculated, and the speed data for each pulse hit of the target is estimated.

Next, the phase compensation processor 14 calculates the amount of phase compensation for each pulse hit using the speed data, and performs complex multiplication with the video signal output from the range migration correction processor 12 to calculate the phase compensation amount. Perform compensation processing. Then, the cross-range compressor 15 receives the video signal and performs frequency analysis in the pulse hit direction to compress the video signal in the cross-range direction. From the principle of inverse synthetic aperture radar, the resolution of this cross range compression is
Can be represented by Here, Δr is the cross-range resolution, θ is the data acquisition time, the target total rotation angle in the so-called synthetic aperture time, and λ is the transmission frequency.

[0009]

(Equation 1)

From equation (1), the cross-range resolution is proportional to the total rotation angle of the target within the synthetic aperture time. If the target rotation angle is large within a certain synthetic aperture time, the cross-range resolution increases, and the rotation angle decreases. If it is small, the cross range resolution will be degraded. When the target rotates by a rotation angle required for the desired cross-range resolution, a high rotation speed requires a short synthetic aperture time, but a low rotation speed requires a long synthetic aperture time. For example, λ = 0.0
3 cm, target rotation speed = 0.015 rad / s,
When it is desired to obtain a cross range resolution of 1 m, the synthetic aperture time of 1 second is sufficient, but the target rotation speed = 0.001 ra
At d / s, a synthetic aperture time of 15 seconds is required.

As described above, the conventional radar signal processor compresses a target object in the range direction by the range compressor 7 and compresses the target object in the cross range direction by the cross range compressor 15, thereby producing two-dimensional image data. Obtainable. Further, the displacement of the range bin causing the image deterioration is determined by the distance tracking processor 9 and the range migration correction processor 12.
, And the offset component and the primary component of the Doppler frequency are removed by the Doppler tracking processor 13 and the movement compensation processor 14, so that good image data can be obtained.

[0012]

In the conventional radar signal processor as described above, the cross range compression is performed by focusing on the Doppler frequency generated by the target motion. However, in the principle of the inverse synthetic aperture radar, When the target speed is low, there is a problem that a sufficient cross-range resolution cannot be obtained unless the synthetic aperture time is long.

A radar signal processor according to a first aspect of the present invention has been made in order to solve such a problem, and calculates a Doppler frequency from a Doppler history of a target in order to analyze a rotational motion of the target. It is an object of the present invention to obtain a radar signal processor that detects a rotation speed and calculates an optimum synthetic aperture time.

Further, the radar signal processor according to the second aspect of the present invention obtains a radar signal processor which statistically processes Doppler history in order to cope with a complicatedly changing movement of a target and calculates an optimum synthetic aperture time. With the goal.

Further, in addition to the above object, the radar signal processor according to the third invention, when estimating the Doppler history of a target, cuts out an optimum range bin signal to improve Doppler tracking accuracy. The purpose is to obtain a vessel.

Further, in addition to the above object, the radar signal processor according to the fourth aspect of the present invention provides a video signal extracted by a reference point detector instead of a phase compensation speed calculator for calculating the speed of a target from Doppler history. It is an object of the present invention to obtain a radar signal processor that obtains a phase of a signal and estimates velocity data of a target from the phase.

Further, in addition to the above object, the radar signal processor according to the fifth aspect of the present invention uses a Doppler tracking process instead of the speed data estimated in the distance tracking process for the speed data input to the range migration correction processor. It is an object of the present invention to obtain a radar signal processor that improves imaging performance by using estimated velocity data.

[0018]

A radar signal processor according to a first aspect of the present invention calculates an average value of Doppler history output from a Doppler history detector, calculates a difference from a Doppler frequency at each time, and calculates the difference. Is attached with a Doppler frequency calculator for obtaining the maximum value of.

The radar signal processor according to the second aspect of the present invention calculates the standard deviation of the Doppler frequency in order to cope with a target that varies in a complex manner in the above-mentioned one, thereby calculating the standard deviation statistically handling the Doppler history. A vessel was attached.

Further, in the radar apparatus according to the third aspect of the present invention, the reference point detection for adding the signal after the range migration correction processing in the pulse hit direction for all the range bins and cutting out the signal of the range bin having the maximum value is performed. A vessel was attached.

Further, in the radar apparatus according to the fourth aspect of the invention, instead of calculating the phase compensation velocity data from the Doppler history in the above-described apparatus, the radar apparatus calculates the phase from the video signal cut out by the reference point detector, and calculates the phase from the phase. It is provided with an isolated point phase calculator for calculating phase compensation speed data.

Further, the radar apparatus according to the fifth invention uses the velocity data estimated by the Doppler tracking processor in the above-described apparatus to calculate a range migration correction amount for removing a change in distance due to movement of a target. A second method of calculating for each pulse and correcting a distance change for each pulse
Is attached.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 FIG. 1 is a configuration diagram showing Embodiment 1 of the present invention. Note that the same components as those in the related art are denoted by the same reference numerals, and description thereof will be omitted. In the figure, reference numeral 16 denotes a segmented FFT calculator for performing FFT on the video signal output from the range migration compensator 12 while shifting the time, and 17 denotes a segmented FF.
A Doppler history detector that detects a reference point that is the maximum amplitude point from the spectrum output from the T calculator 16 and calculates Doppler history, and 18 is a phase compensation speed calculator that estimates a phase compensation speed from the Doppler history , 1
Reference numeral 9 denotes a motion analysis processor constituted by a Doppler frequency calculator 20, which will be described later. Reference numeral 20 denotes a Doppler frequency calculator which obtains an average value from the Doppler history and obtains a maximum difference between the value and the Doppler frequency at each time. Is the motion analysis processor 1
9 is a synthetic aperture time calculator that calculates the optimal synthetic aperture time for the movement of the target based on the Doppler frequency output from. Hereinafter, the Doppler tracking processor 13 and the motion analysis processor 1
9 and the synthetic aperture time 21 will be described.

First, the Doppler tracking processor 13 will be described. Doppler tracking processor 13 is a segmented FFT calculator 1
6, a Doppler history detector 17 and a phase compensation speed calculator 18. The segmented FFT calculator 16 inputs a video signal from the range migration correction processor 12, and this video signal is obtained by cutting out the range bin detected as the maximum amplitude value by the distance calculator 10. FIG. 3 is a conceptual diagram of the processing of the segmented FFT, in which a time-changed spectrum is calculated by performing FFT on a video signal cut out from the figure while shifting the time. These spectral data are output to the Doppler history detector 17. After inputting the spectrum data, the Doppler detector 17 detects the Doppler history by detecting the maximum amplitude at each time and extracting the Doppler frequency.
The phase-compensating speed calculator 18 calculates the speed from this Doppler history according to equation (2). This speed is output to the phase compensation processor 18.

[0025]

(Equation 2)

Next, the motion analysis processor 19 will be described. The motion analysis processor 19 includes a Doppler frequency calculator 20, and analyzes the motion of the target based on the Doppler history output from the Doppler history detector 17. As shown in FIG. 4, the motion of the target is divided into a motion of a translation component and a motion of a rotation component. Since the motion of the translation component is the acceleration motion of the target, the speed changes temporarily. If the radar is mounted on a moving platform, such as an airplane, the radar captures the speed of the target as a relative speed, and that speed is added to the speed of the translation component. In any case, the Doppler frequency generated by the speed of the translation component is proportional to the speed,
The change is as shown in FIG. Further, the motion of the rotation component is mainly governed by the pitch motion and the roll motion of the target, and becomes a sine wave motion. Therefore, the Doppler frequency of the rotation component changes as shown in FIG. The Doppler frequency obtained by combining these motions is shown in FIG.
As shown in (c), a drift component having a long period is added to the sinusoidal motion.

The Doppler frequency calculator 20 analyzes the motion of the target from the Doppler history output from the Doppler history detector 17. First, a change in the drift component is calculated to extract the motion of the translation component. In order to simplify the processing, the acceleration component is regarded as 0, and the average value of the Doppler frequency is obtained. Then, by calculating the difference between the Doppler frequency at each time and the average value, the amplitude value of the Doppler history (maximum value of spread) that changes sinusoidally can be obtained (see FIG. 6A). if,
If there is no sinusoidal motion, the Doppler history is
6B, the difference between the average value and the frequency at each time is calculated, and the maximum value of the difference shown in FIG. 6B is obtained. The maximum value of the difference between these Doppler frequencies is output to the synthetic aperture time calculator 21.

Next, the synthetic aperture time calculator 21 will be described. Inverse synthetic aperture radar focuses on the Doppler frequency generated by the movement of a target object to achieve higher resolution. To improve cross-range resolution, it is necessary to set the optimal synthetic aperture time for changes in Doppler frequency. .
The frequency bin width is expressed by Expression 3 using the synthetic aperture time. Here, Δf is the frequency bin width, and T is the synthetic aperture time.

[0029]

(Equation 3)

On the other hand, when the spread of the Doppler frequency is ΔF, if the number of pixels of the target in the case of forming an image is to be set to N, the frequency bin width is expressed by the following equation (4). Thus, the synthetic aperture time is shown as in Equation 5.

[0031]

(Equation 4)

[0032]

(Equation 5)

As described above, the synthetic aperture time calculator 21 calculates the synthetic aperture time from the spread of the Doppler frequency output from the Doppler frequency calculator 20 and the desired number of pixels of the target object according to the equation (5). , And a video signal corresponding to that time is cut out to perform processing by the inverse synthetic aperture radar, so that an image of a target having a desired number of pixels can be obtained. FIG. 7 shows a conceptual diagram of the above processing. Also, as an example, when the target is rotating and the Doppler spread is 10 Hz, if the desired number of pixels is required to be 20 pixels, the synthetic aperture time of 2 seconds is optimal. In the case where only the translational motion is performed without the rotational motion and the Doppler spread is 1 Hz, the synthetic aperture time requires 20 seconds.

Embodiment 2 FIG. 8 is a configuration diagram showing a second embodiment of the present invention. Note that the same components as those in the related art are denoted by the same reference numerals, and description thereof will be omitted. In the figure, reference numeral 22 denotes a standard deviation calculator for statistically processing the Doppler history and calculating the spread of the Doppler frequency.

Next, the operation will be described. Embodiment 1
The motion of the target is a composite of the translational motion and the rotational motion, and the translational motion is the acceleration motion that considers the target as a mass point, or the acceleration motion of the mobile when the radar is mounted on the mobile. It was supposed to be an exercise with the addition of However, when the state of the sea surface is very poor, the target on the sea surface moves while riding over the waves, and thus moves in such a manner that the acceleration changes sinusoidally. Therefore, simply calculating the difference between the Doppler frequency and the average value and calculating the maximum value increases the error (see FIG. 9A). Therefore, the standard deviation calculator 22 includes the Doppler frequency calculator 2
The difference from the average value of the Doppler frequency obtained at 0 is output for each time, and the standard deviation is obtained, thereby statistically processing the change of the Doppler frequency (see FIG. 9B). Then, the Doppler frequency is output to the synthetic aperture time calculator 21.

Embodiment 3 FIG. 10 is a configuration diagram showing a third embodiment of the present invention. Note that the same components as those in the related art are denoted by the same reference numerals, and description thereof will be omitted. In the figure, reference numeral 27 denotes a reference point detector that optimally cuts out data used for processing when the Doppler tracking processor 13 estimates the Doppler history of a target.

Next, the operation will be described. When the Doppler tracking processor 13 estimates the target Doppler history, the processing is performed by cutting out the video data after range migration at any one of the plurality of isolated reflection points shown in FIG. Conventionally, among isolated points detected by the distance calculator 10, attention is paid to an isolated point having the largest amplitude detected in the first pulse hit, and video data after range migration of the isolated point is cut out to perform Doppler tracking processing. (D in FIG. 11). In this case, if the isolated point is stable for the first pulse hit as shown in FIG. 11 and the amplitude value is low thereafter, accurate Doppler tracking cannot be performed. Therefore, as shown in FIG. 12, the reference point detector 19 adds the amplitude of the video signal after the range migration correction processing for all the range bins in the pulse hit direction, and detects the isolated reflection point having the largest amplitude value in the pulse hit direction. The video signal is cut out and output to the Doppler tracking processor 13. By performing the above processing, the Doppler tracking process using the most stable isolated reflection point can be performed by selecting the isolated reflection point having the maximum amplitude value from among the plurality of isolated reflection points.

Embodiment 4 FIG. FIG. 13 is a configuration diagram showing a fourth embodiment of the present invention. Note that the same components as those in the related art are denoted by the same reference numerals, and description thereof will be omitted. In the figure, reference numeral 24 denotes an isolated point phase calculator 24 for calculating a phase from a video signal cut out by the reference point detector 23 and estimating a speed.

Next, the operation will be described. The phase of the video signal cut out by the reference point detector 23 is related to the distance between the radar and the reference point, and is shown as in Equation 6. Where φb (t) is the phase, Rb (t) is the distance between the radar and the reference point, λ is the transmission wavelength, and t is time.

[0040]

(Equation 6)

If the video signal is phase-compensated using this phase as a phase compensation amount, the reference point becomes a DC component signal having a Doppler frequency of 0, and it is as if the reference point is the center of rotation of the target. In addition, since a nearby point rotates around the reference point, the phase between the radar and the nearby point is expressed by Equation 7. Here, Δφ and ΔR are the phase and distance changed by the rotational movement.

[0042]

(Equation 7)

When the video signal having this phase is phase-compensated with the above-mentioned phase compensation amount φ (t), a video signal remaining by Δφ (t) is obtained, and the change of this phase becomes different from the reference point. This difference in phase change appears as a difference in Doppler frequency, and a reference point and a nearby point can be separated by frequency discrimination (FFT). Therefore, the phase of the video signal at the reference point is the amount of phase compensation.

As described above, the isolated point phase calculator 24 obtains the velocity data according to the equation (8) and outputs the velocity data to the phase compensation processor 14, thereby performing the cross range compression. However,
S (n) is the signal at the reference point, PRI is the pulse repetition period, and V is the speed of the target.

[0045]

(Equation 8)

Embodiment 5 FIG. FIG. 14 is a configuration diagram showing a fifth embodiment of the present invention. Note that the same components as those in the related art are denoted by the same reference numerals, and description thereof will be omitted. In the figure, reference numeral 25 denotes a second range migration correction processor that inputs the speed data of the target estimated by the Doppler tracking processor 13 and performs a range migration correction process.

Next, the operation will be described. The second range migration correction processor 25 is the same as the range migration correction processor 12, but differs from the fourth embodiment in that velocity data calculated from the distance tracking processor 9 is used. Instead, the velocity data calculated from the Doppler tracking processor 13 is used. In the present invention, considering the processing flow, the system is mainly divided into a system for calculating image data and a system for calculating speed data for correcting movement of a target. Conventional technology and Embodiment 1
In the process of calculating the image data, the speed data is calculated in parallel in the steps 4 to 4. In the fifth embodiment, the speed data is first calculated by the Doppler tracking processor 13, and then the speed data is used. Then, a range migration correction process and a phase compensation process are performed to calculate image data. The reason for performing the above processing is that the speed data calculated by the Doppler tracking processor 13 has higher accuracy than the speed data calculated by the distance tracking processor 9, and it is better to perform correction processing using the speed data. This is because clear image data can be obtained. Assuming a normal inverse synthetic aperture radar, when estimating the speed with the distance tracking processor 9,
Since the range bin width is about 1m and the data collection time is 1s,
Although the speed error is about 1 m / s, the Doppler tracking processor 1
When estimating the speed at 3, the frequency resolution is 4 Hz,
Since the velocity is 03 m, the velocity error is about 0.06 m / s, and the velocity selected by the Doppler tracking processor has higher accuracy. Therefore, the velocity data calculated by the Doppler tracking processor 13 is converted to the second range migration correction processor 20.
By inputting and correcting the image data, clearer image data can be obtained.

[0048]

According to the first aspect of the invention, the Doppler frequency calculator is attached to analyze the motion of the target from the Doppler history of the target, calculate the spread of the Doppler frequency, and calculate the synthetic aperture time calculator. The effect of this is that the optimum synthetic aperture time can be calculated from the Doppler frequency.

According to the second aspect of the present invention, in addition to the above effects, when the movement of the target is complicated, the difference between the average Doppler frequency and the average value of the Doppler frequency obtained by the Doppler frequency calculator 20 as shown in FIG. Since the error is large at the maximum value, there is an effect that an optimal synthetic aperture time can be calculated by performing a statistical process by attaching a standard deviation calculator.

According to the third aspect of the present invention, in addition to the above effects, in order to estimate the Doppler history by the Doppler tracking processor, the signals after the range migration correction processing are added in the pulse hit direction for all range bins. By attaching a reference point detector that cuts out the signal of the range bin having the maximum value, there is an effect that Doppler tracking accuracy can be improved.

According to the fourth aspect of the invention, in addition to the above-described effects, the Doppler history 17 performs smoothing by smoothing the changing Doppler frequency. Therefore, there is an effect that such a problem can be solved by using the phase of the signal cut out by the reference point detector 23 as the phase compensation amount as it is.

According to the fifth aspect of the present invention, in addition to the above-described effects, a range migration correction amount for removing a change in distance due to the movement of a target using the velocity data estimated by the Doppler tracking processor. By installing a second range migration correction processor that calculates each pulse and corrects the distance change for each pulse, highly accurate range migration correction processing can be performed, and clearer image data is calculated. There is an effect that can be.

[Brief description of the drawings]

FIG. 1 is a diagram showing a first embodiment of a radar signal processor according to the present invention;

FIG. 2 is a diagram for explaining a range-compressed video signal and a distance tracking processor in the radar signal processor according to the first embodiment of the present invention.

FIG. 3 is a diagram for explaining a partitioned FFT process in the first embodiment of the radar signal processor according to the present invention;

FIG. 4 is a diagram for explaining a motion component of a target in the radar signal processor according to the first embodiment of the present invention;

FIG. 5 is a diagram for explaining Doppler history in the first embodiment of the radar signal processor according to the present invention;

FIG. 6 is a diagram for explaining a calculation method of motion analysis processing in the first embodiment of the radar signal processor according to the present invention.

FIG. 7 is a diagram for explaining a method of calculating a synthetic aperture time in the first embodiment of the radar signal processor according to the present invention;

FIG. 8 is a diagram showing a second embodiment of the radar signal processor according to the present invention;

FIG. 9 is a diagram illustrating a standard deviation calculator according to a second embodiment of the radar signal processor according to the present invention;

FIG. 10 is a diagram showing a third embodiment of the radar signal processor according to the present invention;

FIG. 11 is a diagram for explaining the purpose of a reference point detector in a radar signal processor according to a third embodiment of the present invention.

FIG. 12 is a diagram for explaining a processing method of a reference point detector in a radar signal processor according to Embodiment 3 of the present invention;

FIG. 13 is a diagram showing a fourth embodiment of the radar signal processor according to the present invention;

FIG. 14 is a diagram showing a fifth embodiment of the radar signal processor according to the present invention;

FIG. 15 is a diagram showing a conventional radar device.

[Explanation of symbols]

1 transmitter, 2 transmission / reception switch, 3 transmission / reception antenna, 4
Receiver, 5 signal processor, 6 display, 7 range compressor, 8 two-dimensional memory, 9 distance tracking processor, 10
Distance calculator, 11 RMG speed calculator, 12 range migration correction processor, 13 Doppler tracking processor, 14 phase compensation processor, 15 cross-range compressor, 16-section FFT calculator, 17 Doppler history detector, 18 phase Compensation speed calculator, 19 motion analysis processor, 20 Doppler frequency calculator, 21 synthetic aperture time calculator, 22 standard deviation calculator, 23 reference point detector, 24 isolated point phase calculator, 25 second range migration Correction processing.

Claims (5)

[Claims] 1. An inverse synthetic aperture radar for imaging the shape of a target using Doppler frequency generated by the movement of the target, using a transmission signal (chirp signal) subjected to frequency modulation by a transmitter. A range compressor that performs pulse compression processing on a video signal output from a receiver, and stores the video signal after the range compression in a two-dimensional memory in a range direction × pulse hit direction to obtain an optimal combination according to a target motion. A two-dimensional memory that cuts out video signals based on the aperture time, and the maximum point of reflected power of the target is detected for each pulse hit to estimate the speed in the range direction (radial speed), and the distance between the maximum points is calculated. A speed calculator for calculating the speed data of the target by estimating the speed data of the target by smoothing the distance of the maximum point; A range migration correction processor for calculating a range migration correction amount for removing a distance change for each pulse from the speed data, and correcting a video signal output from the two-dimensional memory based on the range migration correction amount; A segmented FFT calculator that cuts out a video signal of the maximum point of the reflected power detected by the distance calculator from the video signal after the range migration correction processing and performs Fourier transform while shifting the time, and outputs from the segmented FFT calculator. Detect a reference point that has the maximum amplitude value from the spectrum signal,
A Doppler history detector for calculating Doppler history, a phase calculator for estimating speed information of a target by smoothing the Doppler history, and an offset component and a primary component of a Doppler frequency caused by motion of the target. Phase compensator for calculating a phase compensation amount from the speed data output from the phase compensation speed calculator and compensating the video signal after the range migration correction, and an output from the phase compensation processor. A frequency analysis is performed by FFT of the video signal to be performed in the pulse hit direction, a cross range compressor for compressing the target in the cross range direction, and an average value of the Doppler frequency from the above Doppler history is calculated. Doppler frequency calculation to find the difference from the frequency and calculate their maximum value Vessels and radar signal processor, characterized in that it comprises a synthetic aperture time calculator for calculating an optimal synthetic aperture time than the maximum value of the Doppler frequency difference. 2. The Doppler frequency calculator calculates the average of Doppler history and the maximum value of the Doppler frequency difference at each time. In addition, the Doppler history calculator calculates a Doppler history statistic in order to cope with a complexly changing Doppler history. 2. The radar signal processor according to claim 1, further comprising a standard deviation calculator for calculating. 3. A reference point detector for adding a signal after the range migration correction processing in the pulse hit direction for all range bins and estimating a signal of a range bin having a maximum value when estimating Doppler history. The radar signal processor according to claim 2, wherein: 4. A phase of a video signal cut out by the reference point detector is obtained instead of a phase compensation speed calculator for estimating speed data of a target from the Doppler history,
4. The radar signal processor according to claim 3, further comprising an isolated point phase detector for estimating velocity data of the target from the phase. 5. In the speed data input to the range migration correction processor, speed data output from an isolated point phase calculator is input instead of the speed data output from the RMG speed calculator, and While calculating the range migration correction amount for removing the distance change due to the movement for each pulse from the speed data,
5. The radar signal processor according to claim 4, further comprising a second range migration correction processor for correcting a video signal output from the two-dimensional memory based on the range migration correction amount.