[天线]New approximate formulations for EM scattering by dielectric objects

684 IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, VOL. 52, NO. 3, MARCH 2004 2'Kh>c2  
New Approximate Formulations for EM Scattering )`gxaT>&l  
by Dielectric Objects v9f%IE4fX  
Tie Jun Cui, Senior Member, IEEE, Weng Cho Chew, Fellow, IEEE, and Wei Hong, Member, IEEE `m"K_\w=/  
Abstract—The extended Born approximation (ExBorn) has Gtv
bm  
been shown an efficient formulation in the electromagnetic (EM) 8W7ET@`  
scattering by dielectric objects in both free-space and air-earth YETGq-  
half-space problems. In most cases, ExBorn is much more accurate ExL7 ]3r  
than the conventional Born approximation at low frequencies.  N PqO b  
When the frequency is high or the contrast of dielectric objects is v=
&xiwz}  
large, however, the ExBorn approximation becomes inaccurate. }y(cv}8
Y  
In this paper, new approximations are proposed for the EM {`>pigo  
scattering by dielectric objects buried in a lossy earth, which are r9D 68*H  
also suitable for the case of free space. It has been shown that the Ia{t/IX\[  
zeroth-order form of new approximations is completely equivalent )lUocm  
to ExBorn. Hence, high-order approximations can be regarded hX-^h2
eV  
as high-order ExBorn. Closed-form formulations are derived o62GEl25  
for the new approximations. Using the fast Fourier transform #W_-S0>&  
(FFT), these formulations can be implemented efficiently at a 889^P`Q5  
cost of log , where is the number of unknowns and "s`#`'  
is a small number. Numerical simulations show that high-order $t5>1G1j7  
ExBorn approximations are much more accurate than the ExBorn ds{)p<LpT  
approximation. *8u<?~9F  
Index Terms—Born approximation, buried dielectric obj .. W55kR.X6M  
~0Zy$L/D  

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