|
| Central Symmetry Lens | ||
| WAVEFRONTIER makes polystyrene chips have the property of a Central Symmetry Lens known as Luneburg Lens, to function as a Multi-Beam Lens Antenna. The Luneburg lens shown in Fig.1 is a spherically symmetric delay-type lens formed of dielectric. The lens has the property that an incident plane wave is brought to a focus on the opposite side of the sphere, as suggested for wave 2 in Fig. 1 for waves 1 and 3. Thus, signals can be received simultaneously with a Luneburg lens from as many directions as there is space available on the sphere to place feed horns or other receiving devices. For steering a single beam the receiver (or transmitter) can be switched to different feed horns, or a single movable feed horn can be used. The variable index required can be obtained with an artificial dielectric material or with concentric shells of dielectric of different indices of refraction. | ||
| Fig.1 | ||
|
|
||
| If a Luneburg sphere is cut in half and a reflecting sheet placed on the flat side, an incoming ray traverses the lens twice and is brought to a focus at F in Fig. 2. The reflector lens is approximately half the thickness and half the weight of a simple dielectric lens and is an alternative to a parabolic reflector. Beam squinting by horizontal displacements of the feed would allow observations of a region near the zenith. Only the thickness of the lens is critical since the flatness of reflecting surface is maintained automatically, thanks to gravity. The lens need not be in contact with the flat surface. | ||
| Fig.2 | ||
 Figure.
2 Reflector-lens
antenna con sisting of a plano-convex dielectric lens on a flat reflecting sheet. |
||
| TOROIDAL dual reflector | |||||||||||||||||
|
Sub-reflectors offer flexibility of design for reflecting telescopes.
The classical arrangement introduced by N. Cassegrain of France uses
a sub-reflector of hyperbolic shape which surrounds the prime focus of
the main parabolic reflector. There are some variations and Gregorian reflector has an ellipsoid as a sub-reflector. |
|||||||||||||||||
|
|||||||||||||||||
| Table 1. Double Reflector Antennas (P:Parabola, H:Hyperboloid, E:Ellipsoid) | |||||||||||||||||
| WAVEFRONTIER's TOROIDAL dual reflector antenna is similar to Gregorian reflector in shape, but the basic formula differs from it. The sub-reflector of TOROIDAL antenna is from a virtual toroid, but the main reflector is analogous to an ellipsoid. There is no parabolic formula. This system has a convex - concave sub-refletor. This sub-reflector is convex in one plane and concave in orthogonal plane. The complete shape of them are obtained through elaborate mathematical and physical calculation. You can say it's a NEW TOROIDAL multi-sat antenna. | |||||||||||||||||
 |
|||||||||||||||||
| Fig.1 TOROIDAL Antenna (T:Toroid, E:Ellipsoid) | |||||||||||||||||
Figure.
1 Luneburg
lens. A plane
