Friday, November 25, 2011

The Future Satellite Antenna - Luneburg Lens Antenna


  Fig: Luneburg Lens Satellite Antenna manufactured by Farragsat,
a company based in Egypt, 
 in front of traditional dish antennas.


Ever wondered what the future satellite reception antennas will look like? 
Check the above pic.

It is basically a Luneburg Lens antenna. If we read through the history, we will find that Luneburg Lens was invented by RK Luneburg in the year 1944. It has taken several years for the modern Luneburg Lens antenna to evolve and take its present shape. This is because in the earlier days, the manufacturing technology was not so advanced to produce a spherically symmetric Luneburg Lens. Hence, earlier Luneburg lenses were 2 dimensional slices through the centre of the sphere. The recent technological advancements have made the construction of a spherically symmetric Lens Antenna possible, using materials such as expaneded polystyrene foam(EPS), foamed glass, etc. 

Basically, a Lens antenna has variable refraction index from its surface to the centre of the sphere, and the refractive index varies according to the equation, n=[2-(r/a)2]1/2. Hence, in an ideal luneburg lens, the refractive index gradually changes from the surface to the centre of the sphere as shown by the graph. But, in practical, they can be realised as shown in the figure.

The Luneburg Lenses are usually used in Microwave frequencies. The electromagnetic waves entreing the sphere are refracted and focussed on the opposite side of the antenna as shown in the figure below. In case of the hemispherical antenna, the point of convergence depens on the angle of reflection of the incident electromagnetic waves as shown in the figure. Because of its features, it is more reliable than a traditional dish antenna.
Fig: Lens Antenna working

These Lunegurg Lens antennas have lot of advantages because of its unique features. The major advantage is that data from multiple satellites can be captured using a single antenna. This can be done my using multiple feeder lines. Hence, in the future, we can have a single antenna which can be used together for simultaneous reception of telephony, television and internet.

This can also be used in areas badly covered by network, on vehicle roofs, and in steep or sparsely populated areas. The commercial production of these Lunebug Antennas have begun, and several companies have come up with different products with varied capabilities for different applications. Hence, these antennas are bound to replace the traditional dish antennas in the future.

References:
1) Antennas and Wave Propagation: Fourth Edition - by John D Kraus, Ronald J Marhefka, Ahmad S Khan
2) Antenna And Wave Propagation - by U.A.Bakshi, A.V.Bakshi
3) Donald G. Bodnar - MI Technologies
4) Farragsat- Designer of Smallest Satellite Lens Antennas
5) Lun Tech- Luneburg Technologies

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