Just when you thought antenna design couldn't get more complicated, you can now add holographic antennas to the units made from metamaterials and custom antennas for vorticity modulation.
Holographic antennas have been around for 40 years, but are getting more attention as researchers look for ways to make antennas smaller and more efficient. A release from an EU funded FP-7-PEOPLE program, Novel holographic designs and uses describes some of the results of the ALOHA (Analysis of Low-cost Original Holographic Antenna) Project.
The purpose of the project is to investigate prototype holographic antennas with electromagnetic waves at microwave frequencies. The release describes the principle behind the HA:
“Holograms are virtual images resulting from the interference of two electromagnetic (EM) waves. Holographic antennas (HAs) are antennas where the reflecting surface (aperture) is formed by a conductive metallic pattern on a grounded multi-layer dielectric substrate. In order to exploit this interference, surface waves can propagate along the substrate and the hologram is then produced by interference at the air-substrate interface.”
Researchers developed unit cells using a width-modulated microstrip line inside each cell and created a cylindrical geometry that consists of multiple repeats of cells along different directions.
The MacQuarie University Website, Analysis of Low-cost Original Holographic Antennas notes the antennas have various advantages, including polarization purity of the radiated field and higher gain due the lack of a feed at the front of the antenna. The microstrip design also allows reduced dimensions and the possibility of using it in conformal configurations.
A 2009 paper from Bollettino della Comunità Scientifica in Australasia, A window on Information Communication Technology by Edoardo Calia provides more technical detail on how holographic antennas work
The project is scheduled to end this month, so we will see if this technology makes it into antennas for terrestrial and satellite communication.
Doug Lung is one of America's foremost authorities on broadcast RF technology. He has been with NBC since 1985 and is currently vice president of broadcast technology for NBC/Telemundo stations.
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