DRAFT Recommended Practice for Measurements and ...

1/29/98 20 C95.3-1991 Revision — 2 nd Draft
10/98 Draft
2. Definitions
anechoic chamber. A room or enclosure in which reflections of EM waves from the
boundary surfaces have relatively small values.
antenna. A device designed for radiating (or receiving) electromagnetic energy.
antenna array. A system of antennas coupled together for the purpose of enhancing
radiation in one or more directions and reducing radiation in other directions.
antenna directivity. The ratio of the transmitted RF radiation intensity in a specified
direction to the radiation intensity averaged over all directions.
NOTE: The average radiation intensity is equal to the power radiated by the antenna divided by 4π.
antenna effective aperture or effective area. In a given direction, the ratio of the
power available at the terminals of a receiving antenna to the power density of a plane
wave incident on the antenna from that direction; the wave being polarization-matched to
the antenna.
NOTES: (1) A plane wave of given power density and from a given direction is polarization-matched
to an antenna if its polarization is that which results in maximum power at the antenna
terminals.
(2 The (total) effective aperture of an antenna may be decomposed into the sum of two
partial effective apertures referred to two specified, orthogonal polarizations, respectively.
(3) For a lossless and perfectly matched antenna, effective area in a given direction is
equal to the square of the operating wavelength, times the gain in that direction, divided
by 4π.
antenna field regions. Classification of the important spatial subdivisions of an
antenna's electromagnetic field. The subdivisions, at non-uniquely defined distances from
the antenna, include the reactive near-field region adjacent to the antenna, the radiating
near-field region (for large antennas commonly referred to as the Fresnel region), a
Copyright © 1998 IEEE. All rights reserved. This is an unapproved IEEE Standards Draft,
subject to change.