Db. Wright et Ac. Cangellaris, FINITE-ELEMENT GRID TRUNCATION SCHEMES BASED ON THE MEASURED EQUATIONOF INVARIANCE, Radio science, 29(4), 1994, pp. 907-921
A new local method for finite difference/finite element (FD/FE) mesh t
runcation in the frequency domain is investigated. The method is based
on the measured equation of invariance (MEI) concept recently propose
d for the numerical solution of electromagnetic wave scattering by per
fectly conducting targets in unbounded regions. An MEI is a numericall
y derived discrete, linear equation which relates the field at a given
boundary node to the field values at neighboring nodes. The extension
of the MEI-based mesh truncation method to treat the case of penetrab
le scatterers is discussed. A new approach that employs distributions
of multipoles to expedite the generation of the MEIs is proposed. This
new approach is compared to an earlier one based on the direct applic
ation of Huygen's principle. Numerical results are presented for time
harmonic scattering by various two-dimensional targets. Since the deri
vation of the MEI is not based on any far-field assumptions, the mesh
truncation condition can be applied just a few cells away from the sca
tterer's boundary, and a computationally efficient and accurate FD/FE
grid truncation can be achieved.