The extended hemispherical lens is a commonly used

lens A lens is a transmissive optical device that focuses or disperses a light beam by means of refraction. A simple lens consists of a single piece of transparent material, while a compound lens consists of several simple lenses (''elements'') ...

for millimeter-wave electromagnetic radiation. Such lenses are typically fabricated from dielectric materials such as

Teflon Polytetrafluoroethylene (PTFE) is a synthetic fluoropolymer of tetrafluoroethylene, and has numerous applications because it is chemically inert. The commonly known brand name of PTFE-based composition is Teflon by Chemours, a spin-off from ...

silicon Silicon is a chemical element; it has symbol Si and atomic number 14. It is a hard, brittle crystalline solid with a blue-grey metallic lustre, and is a tetravalent metalloid (sometimes considered a non-metal) and semiconductor. It is a membe ...

. The geometry consists of a

hemisphere Hemisphere may refer to: In geometry * Hemisphere (geometry), a half of a sphere As half of Earth or any spherical astronomical object * A hemisphere of Earth ** Northern Hemisphere ** Southern Hemisphere ** Eastern Hemisphere ** Western Hemi ...

of radius on a cylinder of length , with the same radius.

Scanning performance

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 Geometrical optics, or ray optics, is a model of optics that describes light Wave propagation, propagation in terms of ''ray (optics), rays''. The ray in geometrical optics is an abstract object, abstraction useful for approximating the paths along ...

: :

\frac = \tan \gamma.

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

References

{{reflist Geometrical optics Lenses Antennas (radio)

Scanning performance

See also

References