Search results
Results from the WOW.Com Content Network
Omnidirectional radiation patterns are produced by the simplest practical antennas, monopole and dipole antennas, consisting of one or two straight rod conductors on a common axis. Antenna gain (G) is defined as antenna efficiency (e) multiplied by antenna directivity (D) which is expressed mathematically as: G = e D {\displaystyle G=eD} .
The top shows the directive pattern of a horn antenna, the bottom shows the omnidirectional pattern of a simple vertical dipole antenna. In the field of antenna design the term radiation pattern (or antenna pattern or far-field pattern) refers to the directional (angular) dependence of the strength of the radio waves from the antenna or other ...
A halo antenna is a half-wave dipole bent into a circle for a nearly uniform radiation pattern in the plane of the circle. When the halo's circle is horizontal, it produces horizontally polarized radiation in a nearly omnidirectional pattern with only a little power wasted toward the zenith, compared to a straight horizontal dipole.
Due to their omnidirectional radiation pattern, vertical monopole antennas are commonly used in terrestrial radio communication systems in which the direction to the transmitter or receiver is unknown or constantly changing, [7] such as broadcasting, mobile two-way radios, and wireless devices like cellphones and Wi-fi networks, [8] [4] because they radiate equal radio power in all horizontal ...
Although it could be categorized as a bent dipole, it has the omnidirectional radiation pattern very nearly the same as a small loop. The halo is more efficient than a small loop, since it is a larger antenna at 1 / 2 wave in circumference with its disproportionately larger radiation resistance.
The approximately-omnidirectional pattern of halos resembles small loops; their radiation efficiency lies between the extreme high efficiency of large loops and the generally poor efficiency of small loops. Halos are self-resonant like full-wave loops, but have no practical higher harmonics.
High gain omnidirectional radiation pattern with wide bandwidth. Circularly-disposed antenna array (CDAA) - An antenna array with the elements arranged in a large circle. CDAAs are used for direction-finding and triangulation of errant radio signals, such as for airspace monitoring and broadcasting enforcement.
Halos are most often oriented with the plane of the loop aligned horizontally, parallel to the ground, in order to effect an approximately omnidirectional radiation pattern in the horizontal plane and minimize wasteful vertical radiation. Small loops, on the other hand, are often oriented vertically, to take advantage of the small loop's "null ...