Abstract.
Several issues concerning
diffraction from pyramidal radio absorber that covers walls of a compact range
are considered in this paper. In particular, differences in convergence and
localization of higher order diffraction fields are demonstrated in comparison
with those scattered on the back wall. In the case of the diffraction from the
back wall, the incidence is almost normal to the wall, thus zero-order field is
significantly lower than higher-order reflected harmonics (-70 dB compared to -30
dB). In the case of the back wall, the angle of incidence can be very close to
even 90 degrees, thus zero-order harmonic’s amplitude becomes higher than
amplitudes of high diffraction orders (-20 dB compared to -35 dB). However, the
distribution of these fields in compact range’s space is different: there are regions
in which amplitudes of high diffraction orders are bigger than the amplitude of
zero-order diffraction. In this paper we develop a method of calculating zero
order and higher order diffraction from the side walls of a compact range.
Convergence of the algorithm is studied; recommendations on parameters of the
calculation, such as size of the grid are given. Higher order harmonic’s
amplitude distribution is calculated and studied. We show that the values of
the higher orders can reach -35 dB and even higher. Considering the fact that
single-periodic radio-absorbers, for example wedge-shaped absorbers scatter significantly
less higher orders, one can use algorithms from this study for more accurate
compact range design and choice of absorber in particular.
Key words: 3D RCWA, radio-absorbing material, anechoic
chamber, compact range.
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