A measure of the concentration of power in a radar beam. The beamwidth in a given plane is the angle subtended at the antenna and containing the main lobe within which the intensity in the far field of the transmitted radiation is not less than a specified fraction of the intensity in the direction of the axis of the main lobe. Ordinarily, beamwidth is defined as the angle within which the intensity is not less than one- half the intensity on the beam axis (the 3-dB beamwidth). Sometimes beamwidth may refer to the linear extent of the beam in the cross-beam direction at some specified range. See antenna pattern.