Beamwidth

Beamwidth is a measure of how concentrated an antenna's radiation pattern is in a given direction. It describes the angular width over which the radiated power is effectively directed, typically focusing on the main lobe of the pattern. Beamwidth is a key parameter for directional antennas used in communications, radar, and sensing, and it helps define coverage and resolution.

The most common definitions are the half-power beamwidth and the first-null beamwidth. The half-power beamwidth (HPBW) is the angular separation between the points in the main lobe where the gain falls to half its maximum value (a drop of 3 dB). Some patterns are described by the first-null beamwidth, which is the angle between the first nulls in the radiation pattern. In practice, beamwidth is often specified in horizontal and vertical planes, yielding azimuth and elevation beamwidths. In three-dimensional patterns, the main lobe’s solid angle can be used to describe the beam’s extent.

Beamwidth is influenced by frequency, wavelength, aperture size, and antenna type. For a given aperture, increasing frequency (reducing wavelength) generally narrows the beamwidth and increases directivity and gain. Conversely, smaller apertures produce wider beams. Phased arrays and shaped-beam antennas can engineer beamwidths to meet coverage requirements, including multiple beams or scanable patterns.

Measurement of beamwidth requires far-field radiation pattern data, typically in anechoic or outdoor test ranges. It is a fundamental specification for link budgets, radar resolution, and satellite communications, where precise control of energy direction is essential.