Extended hemispherical lens
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 on a cylinder of length, with the same radius.When a feed element is placed a distance off the central axis, then the main beam will be steered an angle off-axis. The relation between and can be determined from geometrical optics:
This relation is used when designing focal plane arrays to be used with the extended hemispherical lens.
