Editing Beam diameter (section)

===Full width at half maximum===
{{details|Full width at half maximum|Half-power point#Antennas}}
The simplest way to define the width of a beam is to choose two diametrically opposite points at which the [[irradiance]] is a specified fraction of the beam's peak irradiance, and take the distance between them as a measure of the beam's width. An obvious choice for this fraction is {{sfrac|1|2}} (−3 [[Decibel|dB]]), in which case the diameter obtained is the full width of the beam at half its maximum intensity (FWHM). This is also called the ''half-power beam width'' (HPBW).