Partially reflecting sheet arrays

Multiple reflections of electromagnetic waves between two planes are studied, and the increase in directivity that results by placing a partially reflecting sheet in front of an antenna with a reflecting screen is investigated at a wavelength of 3.2 cm. The construction and performance of various models of such arrays is discussed. Thus, for example, a "reflex-cavity antenna" with an outer diameter of
1.88 \lambda
and an over-all length of only
0.65 \lambda
is described which has half-power beamwidths of
34\deg
and
41\deg
in the
E
and
H
planes, respectively, and a gain of approximately 14 db. It is shown that larger systems produce considerably greater directivity but that their efficiency is poor.