Pencil Beam
In radio technology, very strongly bundled electromagnetic waves are referred to as pencil beam (literally for "pencil beam") . This clearly describes a transmission beam that is "thin as a pencil".
Antennas with a bundled radio beam therefore have a very narrow opening angle and thus a very large antenna gain . Pencil beam antennas are used, for example, as fire control radar . Real 3D radar devices used in air defense also emit bundled radio waves .