ISO/TC 211 Multi-Lingual Glossary of Terms (MLGT)

Note 1 to entry: ${\displaystyle {\eta }_{\text{M}}}$ is calculated using the following formula: ${\displaystyle {\eta }_{\text{M}}=\frac{\int {\int }_Y^{}{F}_n(\theta ,\varphi )d\Omega }{\int {\int }_{4\pi }^{}{F}_n(\theta ,\varphi )d\Omega }}$ where ${\displaystyle F_n}$ is the antenna pattern; ${\displaystyle \theta }$ is the elevation angle; ${\displaystyle \varphi }$ is the azimuth angle; ${\displaystyle d\Omega }$ is the differential solid angle; ${\displaystyle Y}$ is the main lobe value.

Note 2 to entry: Main beam is also referred as main lobe.