## Antenna power pattern, solid angles, associated efficiencies

The power pattern, ( ,), is a measure of the response of the antenna to radiation as a function of the angles and . It is a normalized (maximum value unity), dimensionless quantity. It can depend on the frequency of observation.

The beam area or beam solid angle (or pattern solid angle) is

| (84)

where

| [ ] | beam area,
| [ ] | normalized power pattern of antenna,
| [ ] | infinitesimal solid angle of sky .

The forward beam and main beam solid angles are the integral of the power pattern over and the main lobe, respectively, i.e.,

| (85)

The forward and beam efficiencies are then defined as

| (86)