Half-power point

The half-power point is the point at which the output power has dropped to half of its peak value; that is, at a level of approximately -3 dB.

In filters, optical filters, and electronic amplifiers, the half-power point is also known as half-power bandwidth and is a commonly used definition for the cutoff frequency.

In the characterization of antennas the half-power point is also known as half-power beamwidth and relates to measurement position as an angle and describes directionality.