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INVERSION OF SYNTHETIC APERTUR,E R,ADAR (SAR) - MSpace ...

INVERSION OF SYNTHETIC APERTUR,E R,ADAR (SAR) - MSpace ...

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Tivo-dimelsional invelse FFT ancl arnplitude adjustrnelt steps then follow<br />

the phase shift step.<br />

The cornputational efficiency of the <strong>SAR</strong> processing algor.ithm being pr.oposecl<br />

hele can be conpalecl lvith the conver'ìtional rauge-Doppler. <strong>SAR</strong> plocessols<br />

(for exauple, Wu [t09]). When input clata of a.V by 1/ data allay<br />

are to be processecl using a conventional apploach, the range correlation has<br />

to be pelfolrred first through FFT. Since each corr.elation of Iy' data lequiÌes<br />

¡ú log2 1ú butter'fly computations (BF) for forrvard and irrverse FFT<br />

and Iy' complex urultiplications (CM), the total ralge correlations lequile<br />

.n{ x {(11log, ¡/) . BF +lú.CM} operations. The sa¡re nunìber of opelations<br />

ale âlso Ìequirecl for the aziù1uth col'relation, and consequerìtl)' the lange alid<br />

azirnutlr correlation requires a total of 2 x N x {(1/log, ¡/) . BF +¡ú.CM}<br />

operations. The invelsion algorithn being ploposed in this thesis r.equir.es<br />

2-D FFT ald lV x ly' conplex multiplications, rvhich acld up to 1ú x {2 x<br />

(tú log, 1ú) . BF +1ù.CMÌ operations. Thus the conventional cor.relation algorithm<br />

lequi::es 1{ x 1ú mol'e cornplex multiplications than the inverse algoritlim<br />

for the range ancl azilnutlt cornpr.ession.<br />

89

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