decibels relative to isotropic radiatorThe expression dBi is used to define the gain of an antenna system relative to an isotropic radiator at radio frequencies . The symbol is an abbreviation for "decibels relative to isotropic." The dBi specification is based on the decibel , a logarithm ic measure of relative power . Suppose an antenna A produces an electromagnetic field of intensity I A microwatts per square meter ( I A µW/m 2 ) in its favored direction at a point located some distance away. Also, suppose an isotropic antenna Q produces an electromagnetic field of intensity I Q µW/m 2 at the same distance. Then the gain G of antenna A , in dBi, is: G = 10 log 10 ( I A / I Q ) A dipole antenna has a gain of 2.15 dBi. An isotropic radiator has a gain of 0 dBi.
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| Last updated on:
Apr 05, 2005 |
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