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

684 IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, VOL. 52, NO. 3, MARCH 2004 ?1w{lz(P  
New Approximate Formulations for EM Scattering iMjoatt  
by Dielectric Objects (+uM |a  
Tie Jun Cui, Senior Member, IEEE, Weng Cho Chew, Fellow, IEEE, and Wei Hong, Member, IEEE XuS3#L/3p  
Abstract—The extended Born approximation (ExBorn) has 1Xzgm0OS;  
been shown an efficient formulation in the electromagnetic (EM) *U>"_h T0  
scattering by dielectric objects in both free-space and air-earth mv] .  
half-space problems. In most cases, ExBorn is much more accurate 4PK/8^@7)>  
than the conventional Born approximation at low frequencies. ,2oFt\`.r  
When the frequency is high or the contrast of dielectric objects is Voy
1  
large, however, the ExBorn approximation becomes inaccurate.
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In this paper, new approximations are proposed for the EM ~&HP}Q$#f  
scattering by dielectric objects buried in a lossy earth, which are kZ<0|b  
also suitable for the case of free space. It has been shown that the "o_s=^U  
zeroth-order form of new approximations is completely equivalent QiH>!Ssw  
to ExBorn. Hence, high-order approximations can be regarded 'F2g2W`  
as high-order ExBorn. Closed-form formulations are derived idsBw!DB  
for the new approximations. Using the fast Fourier transform qlSI|@CO  
(FFT), these formulations can be implemented efficiently at a Z5/*iun  
cost of log , where is the number of unknowns and I;1W6uD=  
is a small number. Numerical simulations show that high-order Ig&H0S  
ExBorn approximations are much more accurate than the ExBorn 3bYPi^  
approximation. 7[=\bL  
Index Terms—Born approximation, buried dielectric obj .. q)j b9e   
&3gC&b^i  

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