  We propose in detail Antennas for generating Non-Diffracting Beams of
Microwaves, for instance with frequencies of the order of 10 GHz, obtaining
fair results even when having recourse to realistic apertures endowed with
reasonable diameters. Our first proposal refers mainly to sets of suitable
annular slits, having in mind various possible applications, including remote
sensing. Our second proposal --which constitutes one of the main aims of this
paper-- refers to the alternative, rather simple, use of a Parabolic Reflector,
illuminated by a spherical wave source located on the paraboloid axis but
slightly displaced with respect to the Focus of the Paraboloid. Such a
parabolic reflector yields "extended focus" (non-diffracting) beams. [OCIS
codes: 999.9999; 070.7545; 050.1120; 280.0280; 050.1755; 070.0070; 200.0200.
Keywords: Non-Diffracting Waves; Microwaves; Remote sensing; Annular Arrays;
Bessel beams; Extended focus; Reflecting paraboloids; Parabolic reflectors;
Parabolic antennas].
