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 Template:Mvar on a cylinder of length Template:Mvar, with the same radius.

Scanning performance

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

$\frac{d}{L}=\tan \gamma .$

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

See also

• Luneburg lens
• Fresnel lens
• Lens antenna