초록 ▼

Automatic focusing of radar or sonar imaging systems, for example, synthetic aperture radar (SAR) or synthetic aperture sonar (SAS) systems, is accomplished by using high order measurements, such as the quadruple product of the range compressed signal g(x). The phase error is estimated by a recursiv

Automatic focusing of radar or sonar imaging systems, for example, synthetic aperture radar (SAR) or synthetic aperture sonar (SAS) systems, is accomplished by using high order measurements, such as the quadruple product of the range compressed signal g(x). The phase error is estimated by a recursive or non-recursive algorithm from the phase of the quadruple product. The estimated phase error is applied to the range-compressed SAR or SAS image data which is then azimuth compressed to obtain the focused image data.

대표청구항 ▼

[ What is claimed is:] [21.] A method for correcting the phase errors of a wavefront received at an array of multiple sensors, the steps of the method comprising:receiving wavefront data g(x) at said multiple sensors where x is sensor location;generating a quadruple product of the received data g(x)

[ What is claimed is:] [21.] A method for correcting the phase errors of a wavefront received at an array of multiple sensors, the steps of the method comprising:receiving wavefront data g(x) at said multiple sensors where x is sensor location;generating a quadruple product of the received data g(x) at four different sensor locations according to the relationshipEQU g.sub.4( x.sub.1, x.sub.2, 0, x.sub.1 +x.sub.2)=g(x.sub.1)g(x.sub.2)g*(0)g*(x.sub.1 +x.sub.2)where g*(x) is the complex conjugate of g(x);obtaining the phase .upsilon./.sub.4 of the quadruple product g.sub.4 (x.sub.1,x.sub.2,0,x.sub.1 +x.sub.2) byEQU .psi.4(x.sub.1,x.sub.2,0,x.sub.1 +x.sub.2)=.phi..sub.e (x.sub.1)+.phi..sub.e (x.sub.2)-.phi..sub.e (0)-.phi..sub.e (x.sub.1 +x.sub.2);EQU .upsilon./.sub.4 (x.sub.1,x.sub.2,0,x.sub.1 +x.sub.2)=.phi..sub.e (x.sub.1)+.phi..sub.e (x.sub.2)-.phi..sub.e (0)-.phi..sub.e (x.sub.1 +x.sub.2);where .phi..sub.e is the estimated phase error;recursively estimating the phase error by the relationship.phi..sub.e (i)=.phi..sub.e (j)+.phi..sub.e (i-j)-.upsilon./.sub.4 (j,i-j,0,i); andapplying a phase correction to the data received at each sensor element, except for one reference element.