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

vith silc-function type lacliatiol patteln. For- a rectangulal antenna witlr
climension /1 ancl /2, the approximate expression fol half-porver bearnrviclth
ale giveu by
Ér, - 0.88], /J," - o.ssl
- 11 -
Lz
(3.2)
rvlrere B¡, aÌd Pr2 ate hal{-powel bearnwidth in ladians colresponcling to /1
and /2, respectiveìy (Ulaby ef ø/, [103], p.125).
In an irnaging laclar, the azámuth beamwid,th and eleuation beamwid,tl¿ a,-e
defined by the half-power l¡earnwiclth of the antenna patteln in along-track
(ol aziuuth) ditnensior ancl cross-track (or slant range) dirnensiorì) Ìespectively
(Moore [80], pp.a19). Fol both real and synthetic aperture radar systerns,
fine resolution in the cross-track direction is achievecl through signal
plocessilg (Cook antl Bernfelcl [19]). The funclamental differences between
the two systems are the technique used to achieve the azirruth resolution.
The azirnuth lesolutiol of leal apelture irnaging radal is dilectly determined
by the antenna bearn covelage on the grouncL. The clistance across the antenna
beam fol given anterura physical aperture d and radar lange -B is as
shown in Figule 3.1
L=pR-:R (3.3)
rvhele -L is the clistalce across the antenna beam (also a azirnuth resolution in
the real aperture raclar case). Therefore, the finer azimuth lesolution of leal
apelture laclar is obtailecl by rnakilg ,L smaller, r,r'hich requires to enlalge
the antenna size l. The size of an irnaging ladar is horvever limited if it is to
be calried on a spacecraft or aircraft.