Interrogator antennas are designed to be linearly or circularly polarized. Linearly
polarized antennas can be installed in a horizontal or vertical polarization
position. Circularly polarized antennas can have right-hand or left-hand circular
polarization. For a linearly polarized antenna, orientation of its polarization
must match with the orientation of the tag.A tag in a horizontal position therefore
cannot be read by a vertically polarized antenna and vice versa. The circularly
polarized antenna can read a tag in any orientation but at the expense of
the amount of power received by the tag. A circularly polarized antenna splits
transmitted power into two planes, one perpendicular to the other. A tag therefore
receives only half the power relative to what it would receive froma similar
linearly polarized antenna, which in turn reduces the tag read range. You gain
tag orientation insensitivity but you lose some read range.