Synthetic aperture radar and target image production method

• US 5,805,099 A
• Filed: 12/23/1996
• Issued: 09/08/1998
• Est. Priority Date: 12/26/1995
• Status: Expired due to Term

• Current Assignee: NEC Corporation
• Original Assignee: NEC Corporation
• Inventors: Nagata, Hidefumi
• Primary Examiner(s): Sotomayor, John B.
• Application Number:
  US08/771,905
• Time in Patent Office: 624 Days
• Field of Search: 342/25, 342/190, 342/194, 342/195, 342/197
• US Class Current: 342/25.00B
• CPC Class Codes: G01S 13/9029 specially adapted for moving target detection within a single SAR image or within multiple SAR images taken at the same time

Abstract

A synthetic aperture radar apparatus which analyzes Doppler frequency displacements arising from a range direction motion component of a target and motion components of a flying body to produce a motion target image wherein only azimuth direction motion components of the target are converted into Doppler components. An SAR apparatus wherein SAR reproduction processing is performed based on target information obtained from a reflected wave received from a target and flying information of a flying body includes a recording and reproduction unit for recording the target information and reproducing the data in a designated range, and a moving target processor for analyzing Doppler frequency displacements arising from a range direction motion component of the target and motion components of the flying body from the reproduced data and producing a moving target image wherein only azimuth direction motion components of the target are converted into Doppler components.

Claims

1. A synthetic aperture radar (SAR) apparatus comprising:

an antenna block provided on a flying body for radiating a radio wave toward a target and receiving a reflected wave of the radio wave to acquire information regarding the target;

flying information detection means for detecting flying information of the flying body;

SAR reproduction processing means for effecting SAR reproduction processing based on the target information acquired by said antenna block and the flying information detected by said flying information detector means;

displaying and recording means for displaying and recording a result of the SAR reproduction processing of said SAR reproduction processing means,;

recording and reproduction means for recording the target information acquired by said antenna block and reproducing the data in a designated range from the recorded information; and

moving target processing means for analyzing Doppler frequency displacements arising from a range direction motion component of the target and motion components of the flying body from the data reproduced by said recording and reproduction means and producing a moving target image wherein only azimuth direction motion components of the target are converted into Doppler components;

said displaying and recording means outputting a predetermined range designated from within the display of said SAR reproduction processing means and including the target as a designated range to said recording and reproduction means so as to effect display and recording of the motion target image produced by said moving target processing means.

2. A synthetic aperture radar apparatus as claimed in claim 1, wherein said moving target processing means includes:

range compression processing means for effecting compression in the range direction of the data reproduced by said recording and reproduction means;

correction means for analyzing Doppler frequency displacements arising from motion components of the flying body from the range compression data compression processed by said range compression processing means to effect phase correction of the range compression data;

image production means for converting azimuth direction motion components of the range compression data corrected by said correction means into Doppler components to produce motion target images at a plurality of successive times; and

selection means for analyzing the Doppler frequency displacements arising from the range direction motion components from the moving target images at the successive times produced by said image production means to select a moving target image which exhibits a minimum one of the displacements.

3. A synthetic aperture radar (SAR) apparatus which includes an antenna block provided on a flying body for radiating a radio wave toward a target and receiving a reflected wave of the radio wave to acquire information regarding the target, flying information detection mean for detecting flying information of the flying body, SAR reproduction processing means for effecting SAR reproduction processing based on the target information acquired by said antenna block and the flying information detected by said flying information detector means, and displaying and recording means for displaying and recording a result of the SAR reproduction processing of said SAR reproduction processing means, comprising:

recording and reproduction means for recording the target information acquired by said antenna block and reproducing the data in a designated range from the recorded information; and

moving target processing means for analyzing Doppler frequency displacements arising from a range direction motion component of the target and motion components of the flying body from the data reproduced by said recording and reproduction means and producing a moving target image wherein only azimuth direction motion components of the target are converted into Doppler components;

said displaying and recording means outputting a predetermined range designated from within the display of said SAR reproduction processing means and including the target as a designated range to said recording and reproduction means so as to effect display and recording of the motion target image produced by said moving target processing means;

wherein said moving target processing means includes;

range compression processing means for effecting compression in the range direction of the data reproduced by said recording and reproduction means;

correction means for analyzing Doppler frequency displacements arising from motion components of the flying body from the range compression data compression processed by said range compression processing means to effect phase correction of the range compression data;

image production means for converting azimuth direction motion components of the range compression data corrected by said correction means into Doppler components to produce motion target images at a plurality of successive times; and

selection means for analyzing the Doppler frequency displacements arising from the range direction motion components from the moving target images at the successive times produced by said image production means to select a moving target image which exhibits a minimum one of the displacements; and

wherein said correction means includes;

compression result recording and reproduction means for recording results of the compression processing of said range compression processing means in a time series and reproducing the recorded data in response to a reproduction control signal;

first switching means for switching a destination of outputting of said compression result recording and reproduction means in response to a switching control signal;

Doppler frequency analysis means for analyzing the Doppler frequency displacements arising from the motion components of the flying body based on the range compression data reproduced by said compression result recording and reproduction means; and

phase correction means for effecting phase correction of the range compression data reproduced by said compression result recording and reproduction means based on results of the Doppler frequency analysis effected by said Doppler frequency analysis means; and

wherein said selection means includes;

image recording and reproduction means for recording the moving target images at the different times produced by said image production means in a time sent'"'"'s and reproducing the recorded moving target images in response to a reproduction control signal;

second switching means for switching a destination of outputting of said image recording and reproduction means in response to a switching control signal;

range direction rotational motion analysis means for analyzing Doppler frequency displacements arising from the range direction motion components from the moving target images reproduced by said image recording and reproduction means and outputting a time of an intermediate displacement in a displacement section which is defined by a maximum value and a minimum value of the displacements; and

image selection means for selecting an image at the time outputted from said range direction rotational motion analysis means from among the moving target images reproduced by said image recording and reproduction means;

said Doppler frequency analysis means outputting, when a recorded amount of said compression result recording and reproduction means reaches a predetermined amount, a reproduction control signal to said compression result recording and reproduction means to effect reproduction of the recorded data and further outputting a switching control signal to said first switching means to switch the destination of outputting of said compression result recording and reproduction means to said Doppler frequency analysis means, but outputting, when the Doppler frequency analysis is performed, a switching control signal to said first switching means to switch the destination of outputting of ;

aid compression result recording and reproduction means to said phase correction means and further outputting a reproduction control signal to said compression result recording and reproduction means to effect re-reproduction of the recorded data;

said range direction rotational motion analysis means outputting, when the recorded amount of said image recording and reproduction means reaches the predetermined amount, a reproduction control signal to said image recording and reproduction means to effect reproduction of the recorded data and further outputting a switching control signal to said second switching means to switch the destination of outputting of said image recording and reproduction means to said range direction rotational motion analysis means, but outputting, when the range direction rotational motion analysis is effected, outputting a switching control signal to said second switching means to switch the destination of outputting of said image recording and reproduction means to said selection means and further outputting a reproduction control means to said image recording and reproduction means to effect re-reproduction of the recorded.

4. A target image reproduction method comprising the steps of:

radiating a radio wave from a flying body toward a target;

receiving a reflected wave of the radio wave to acquire information regarding the target; and

producing a target image from the acquired target information and flying information regarding the flying body, wherein Doppler frequency displacements arising from a range direction motion component of the target and motion components of the flying body are analyzed to produce a target image wherein only azimuth direction motion components of the target are converted into Doppler components.

5. A target image reproduction method wherein a radio wave is radiated from a flying body toward a target and a reflected wave of the radio wave is received to acquire information regarding the target, and a target image is produced from the acquired target information and flying information regarding the flying body, comprising:

the first step of recording the target information;

the second step of effecting SAR reproduction processing based on the target information and the flying information;

the third step of designating a target range from an image SAR reproduced in the second step;

the fourth step of reproducing, from the target information stored in the first step, data corresponding to the target range designated in the third step; and

the fifth step of analyzing Doppler frequency displacements arising from range direction motion components of the target and motion components of the flying body from the data reproduced in the fourth step to produce a motion target image wherein only azimuth direction motion components of the target are converted into Doppler components.

6. A target image reproduction method wherein a radio wave is radiated from a flying body toward a target and a reflected wave of the radio wave is received to acquire information regarding the target, and a target image is produced from the acquired target information and flying information regarding the flying body, comprising:

the first step of recording the target information;

the second step of effecting SAR reproduction processing based on the target information and the flying information;

the third step of designating a target range from an image SAR reproduced in the second step;

the fourth step of reproducing, from the target information stored in the first step, data corresponding to the target range designated in the third step; and

the fifth step of effecting compression in a range direction of the data reproduced in the fourth step and analyzing Doppler frequency displacements arising from the motion components of the flying body from the compression processed range compression data to effect phase correction of the range compression data;

the sixth step of converting the azimuth direction motion components of the range conversion data phase corrected in the fifth step into Doppler components to produce motion target images at a plurality of successive times; and

the seventh step of analyzing the Doppler frequency displacements arising from the range direction motion components of the motion target images at the different times produced in the sixth step to select a motion target image which exhibits a minimum one of the displacements.

7. A target image production method as claimed in claim 6, wherein the selection of a motion target image in the seventh step is performed by selecting an image of an intermediate displacement in a displacement section which is defined by a minimum one and a maximum one of the Doppler frequency displacements arising from the range direction motion component.