The extended hemispherical lens is a commonly used lens for millimeter-wave electromagnetic radiation. Such lenses are typically fabricated from dielectric materials such as Teflon or silicon. The geometry consists of a hemisphere of radius R on a cylinder of length L, with the same radius.

Scanning performance

When a feed element is placed a distance d off the central axis, then the main beam will be steered an angle γ off-axis. The relation between d and γ can be determined from geometrical optics:

d L = tan ⁡ γ . {\displaystyle {\frac {d}{L}}=\tan \gamma .}

This relation is used when designing focal plane arrays to be used with the extended hemispherical lens.

See also