Abstract. Concaved semi-transparent
screen forming a sharp drop (cut-off) of the source radiation pattern when
crossing the border shadow area is discussed.
The problem is of interest for
problems of the antennas back lobes suppression, including antenna arrays. It
is connected with the improving of the electromagnetic compatibility and the
reduction of the multipath errors. The review is made in comparison with the problem
of forming a cut-off pattern in the case of a flat semi-transparent screen. Approach
for the synthesis of impedance in the geometrical optics approximation is
developed; the distribution of the impedance becomes purely resistive.
Numerical evaluation of the limits of applicability of the proposed approach is
carried out. Beyond the applicability of the approximation of geometrical
optics, the synthesis optimization procedure is developed; the impedance becomes
complex with nonnegative real part. Numerical estimates, including the impact
of the frequency dependence of the impedance distribution on the cutoff value are
discussed. It is shown that the main constraint
factor for achieving the cut-off pattern is the screen size.
Key words: diffraction by the
semi-transparent screen, shadow domain, cut-off pattern.
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