INVERSION OF SYNTHETIC APERTUR,E R,ADAR (SAR) - MSpace ...
INVERSION OF SYNTHETIC APERTUR,E R,ADAR (SAR) - MSpace ...
INVERSION OF SYNTHETIC APERTUR,E R,ADAR (SAR) - MSpace ...
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olbital <strong>SAR</strong> is given by<br />
Ion = -'#{t<br />
-rä<br />
2<br />
++þ-sin2xsil'?ry')<br />
(cosiy'{sino sin¡ tanø sinry')<br />
Ø"' '<br />
. a! ,l<br />
f :i sin ¡ siu ry' tan a (cos ry' sirr o<br />
- sin þ cos X cos a) j<br />
Q.44)<br />
(Raney [91]). It is noted that the Doppler frequency late clepends only on<br />
the lelative location of a scatterer with respect to the sensor.<br />
3,2.3 Conventional Digital <strong>SAR</strong>, Processors<br />
Ear'ly works on cligital <strong>SAR</strong> processing tecliniclues can be founcl in Blorvn<br />
et aL ll3l,I(iLk [55], ancl Maltinson [74].<br />
These authors did not yet provicle<br />
a full-scale processing scheme for cligital <strong>SAR</strong> irnage reconstruction, Mole<br />
cletailecl and complete digital <strong>SAR</strong> processing schenes wele discussed by Wu<br />
[109], van de Lindt [60], ancl Bennett and Cumming [6] [7]. The plincipal<br />
stlategy of tliese algorithms is such that the <strong>SAR</strong> irnagely can be leconstlucted<br />
by two sequential corlelations of tlle leturn signal with the range refelence<br />
function fir'st ancl then by the azimuth reference function second, thlough<br />
fast correlation approach using the one-dirnensional fast Fourier tlansfolrn<br />
(FFT). The florv chart for the algolithrn is shorvn in Figu::e 3.9.<br />
The mathematical moclel of tìre <strong>SAR</strong> letuln signal may help the algolithrn<br />
to be better undelstood. A <strong>SAR</strong> system generally transmits ancl I'eceives<br />
signal using the same antenna. Duling the tlansnission over a pulse cluration<br />
?, the fi'ecluency is linearly moclulated or "chirped", rvhile the frequency<br />
56