An interrogator with an antenna that allows information exchanges with
multiple transponders in a shorter distance of communication, by securing
an intensified and uniform electromagnetic energy concentrated on areas
near antenna elements. The interrogator is furnished with a sleeve
antenna that includes a monopole conductor of 1/4 wavelength (free space
wavelength) continuously connected to a core wire of a coaxial cable on
one end thereof, and a feed point on the other end, in which the sleeve
antenna is grounded at the feed point. The interrogator has a plurality
of the transponders arrayed near the antenna, and a plurality of the
antennas selected by RF signal selectors. The interrogator antenna allows
movable body identification such as in a goods management system for
identifying multiply arrayed goods.