Method of image generation by means of two-dimensional data processing in connection with a radar with synthetic aperture
First Claim
1. A method for image generation by means of two-dimensional data processing in connection with a radar with synthetic aperture SAR, characterized in that, for the insertion of a motion compensation and for processing at a large drift angle, received SAR data (s(τ
- , t;
ro)),wherein the time in a range direction is identified by τ
, the time in the azimuth direction by t and the shortest range between the target subject and the radar system by ro,are multiplied by a phase correction;
space="preserve" listing-type="equation">H.sub.mc (τ
, t;
r.sub.ref)=exp [j·
φ
.sub.mc (τ
, t;
r.sub.ref)]where j describes a complex part and φ
mc is a line-of-sight phase formation compensation for a reference range (rref) in a first multiplication unit;
an additional cubic phase term is inserted via a second multiplication unit following the performance of azimuth FFTs for compensating a range migration by means of a function;
##EQU12## wherein fa is the azimuth frequency, k is a modulation rate as a function of the range and azimuth frequency, a'"'"' is a linear scaling factor, R'"'"' the range migration, kr the modulation rate of a transmitted chirp signal, λ
the wave length, c the speed of light and β
2 and β
3 are respectively a square and a cube of a parameter β
defined as ##EQU13## wherein v is a platform speed;
following a performance of range FFTs after compensation of the range migration by means of the function H1, the range migration is entirely eliminated by means of an additional linear frequency displacement (fr) in a function ##EQU14## by multiplication in a third multiplication unit;
subsequently the SAR data are transformed back into a two-dimensional range-Doppler domain having coordinates of range time and azimuth frequency, by means of range IFFTs;
a remaining phase flow created by a chirp scaling function is corrected by multiplication in a fourth multiplication unit by a function;
##EQU15## subsequently the SAR data are transformed back into a time domain by means of azimuth IFFTs;
then a range-dependent phase correction
space="preserve" listing-type="equation">H.sub.mc (τ
, t;
r.sub.o)=exp[j·
(φ
.sub.mc (τ
, t;
r.sub.o)-φ
.sub.mc (τ
, t;
r.sub.ref))]is performed by multiplication in a fifth multiplication unit for the exact motion compensation in the time domain;
then, after performing further azimuth FFTs for azimuth compression, a one-dimensional reference function in the frequency domain ##EQU16## is performed by multiplication in a sixth multiplication unit, and following the performance of azimuth IFFTs, two-dimensional SAR data (corresponding to a function f(τ
, t)) are obtained.
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Abstract
In connection with a method for image generation by means of two-dimensional data processing, received SAR data are multiplied by a phase correction (Hmc) for a reference range (rref) for the insertion of a motion compensation and for processing at a high drift angle, and an additional cubic phase term is inserted for compensating a range migration. The entire range migration is then eliminated by means of an additional linear frequency displacement; subsequently the SAR data are transformed back into the "range-Doppler" domain. A remaining phase error, created by a "chirp scaling" correction, is corrected, the SAR data are transformed back into the time domain and a phase correction as a function of the range is performed by multiplication for the exact motion compensation in the time domain. The one-dimensional reference function is performed in the frequency domain for azimuth compression, by means of which two-dimensional SAR data are obtained.
-
Citations
4 Claims
-
1. A method for image generation by means of two-dimensional data processing in connection with a radar with synthetic aperture SAR, characterized in that, for the insertion of a motion compensation and for processing at a large drift angle, received SAR data (s(τ
- , t;
ro)),wherein the time in a range direction is identified by τ
, the time in the azimuth direction by t and the shortest range between the target subject and the radar system by ro,are multiplied by a phase correction;
space="preserve" listing-type="equation">H.sub.mc (τ
, t;
r.sub.ref)=exp [j·
φ
.sub.mc (τ
, t;
r.sub.ref)]where j describes a complex part and φ
mc is a line-of-sight phase formation compensation for a reference range (rref) in a first multiplication unit;an additional cubic phase term is inserted via a second multiplication unit following the performance of azimuth FFTs for compensating a range migration by means of a function;
##EQU12## wherein fa is the azimuth frequency, k is a modulation rate as a function of the range and azimuth frequency, a'"'"' is a linear scaling factor, R'"'"' the range migration, kr the modulation rate of a transmitted chirp signal, λ
the wave length, c the speed of light and β
2 and β
3 are respectively a square and a cube of a parameter β
defined as ##EQU13## wherein v is a platform speed;
following a performance of range FFTs after compensation of the range migration by means of the function H1, the range migration is entirely eliminated by means of an additional linear frequency displacement (fr) in a function ##EQU14## by multiplication in a third multiplication unit;
subsequently the SAR data are transformed back into a two-dimensional range-Doppler domain having coordinates of range time and azimuth frequency, by means of range IFFTs;a remaining phase flow created by a chirp scaling function is corrected by multiplication in a fourth multiplication unit by a function;
##EQU15## subsequently the SAR data are transformed back into a time domain by means of azimuth IFFTs;then a range-dependent phase correction
space="preserve" listing-type="equation">H.sub.mc (τ
, t;
r.sub.o)=exp[j·
(φ
.sub.mc (τ
, t;
r.sub.o)-φ
.sub.mc (τ
, t;
r.sub.ref))]is performed by multiplication in a fifth multiplication unit for the exact motion compensation in the time domain; then, after performing further azimuth FFTs for azimuth compression, a one-dimensional reference function in the frequency domain ##EQU16## is performed by multiplication in a sixth multiplication unit, and following the performance of azimuth IFFTs, two-dimensional SAR data (corresponding to a function f(τ
, t)) are obtained. - View Dependent Claims (2, 3, 4)
- , t;
Specification