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

is constant cluling the receiving periocl.
desclibed by
Ðach transr:ritted pulse can be
s(o,l) : cos (ust ¡ p*) (3.45)
rvhere Lus is a can'ier fi'equency, ancl the FM slope p. Li Eq.(3.45), the pulse
elvelope was not included. A cletailed folrnula for the pulse envelope can be
found ir van de Lindt [60].
Tlre signal returned frorn a scatteler located at R(r, r¡) has time-clelayecl
fi'orn tlansmission by 2,8(r,7)/c, and is given by
s(t:,t;r¡): cos
(3.46)
wlìere 4 is slant range at the closest approach of an antenna as shown in Figure
3.10. Aftel quach'ature clemodulation at the r.eceiver, the signal retulnecl
frotn a point scatterer cau be written as
{¿.,0 Q -?rO,A) + uft -;ot",rll"}
s(z,r;7) : ",0{,u l, -îoø.?)]'} *p
{-;)no,r} ß.47)
t
: h1þ:,t;n)hr(Ì.,t;n)
wlrele the wavelength À : 2ncløo. The first terrn lz1 (r, l; 4) accounts for the
range chirp ancl lange rniglation. The second tenn li2(ø,ú; 4) is the Dopplel
phase shift cliscussed in the plevious section. ln conventional apploaches
(Figure 3.9), the range compression is carriecl out first through the fast FFT
couelation. The Foulier tlansform of h1(t.,t;q) with lespect to f is given by
h1(a,a; r¡): *, {-r#i
.,p {-á?
aç*,,t¡.\ . (3.48)
Tlre larrge matched filtering is achievecl by rnultiplying fu(r,ø;q) by a cornplex
conjugate function of exp{-iu2 l4¡r,}. The inverse Fourier tr.ansfomr
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