04 April 2012

BEIRUT: The cedar – national symbol of Lebanon since it was first incorporated into the French Mandate (1918-43) flag – has gone wireless.

“We wanted to do something for Lebanon,” says Karim Kabalan, professor and chairman of the Department of Electrical and Computer Engineering (ECE) at the American University of Beirut.

“The cedar design was the most successful of the designs we experimented with, due both to it’s symbolism and particular shape.”

After two years of searching for an antenna design suitable for 3G wireless communications and wireless Internet that would be simple, inexpensive to fabricate and innovative – deviating away from the standard rectangular and circular shapes – a small team composed of two professors and four Ph.D students found their solution by mimicking Lebanon’s national tree.

This may seem like a belated April fools day attempt to lure in the gullible but, in fact, it is nothing of the sort.

In recent years the design of antennas that are inspired by forms found in nature have become increasingly prevalent in the antenna research community worldwide – mirroring developments in other scientific disciplines such as the observation of bird flight in improving airplane aerodynamics. Other researchers have worked on insect-inspired antennas.

“In research you have to innovate and think outside the box; otherwise, you won’t create anything new,” explains Kabalan.

The efficacy of the particularly Lebanese design developed at AUB lies in the geometry of the cedar, explains Mohammed Husseini, a member of the Electromagnetics and Radio Frequency Group at the ECE who recently gained his Ph.D following participation in the project:

“The fractal shape of the cedar design with the triangular motif repeated over a number of scale sizes enables the antenna to function at many different frequencies simultaneously, making it suitable for wireless devices like mobile phones.”

The design process was not without its complications.

Since there were no equations to rely on during the testing of the innovative cedar design, those involved had to rely on a painstaking process of trial and error before the final design was fabricated at the ECE labs:

“I have gone through an arduous job in getting the antenna functional,” explains Mervat Madi, a Ph.D candidate in Electrical and Computer Engineering, in the AUB press release about the project. “At one point we thought we’d reached a working design, but it turned out the antenna gain was negative [meaning the antenna was not a good conductor of signals]. At that point, I had to make substantial changes to the design, which ultimately solved the problems.”

Kabalan hopes that the development of the cedar antenna will additionally encourage the Lebanese government to support ECE projects. He says that current government investment is “next to nothing” with the majority of funding coming from the university itself and philanthropic donations from former pupils.

While the current design is not suitable for TV transmission, plans are under way to develop a cedar design on a grander scale to support the heightened power of broadcast television signals. The development of other forms of antenna, serving different purposes, is also under way.

Lise Safatly, a Ph.D candidate and member of the research team, is currently developing a “narrow band antenna” – operating at one specific frequency in contrast to the cedar design – named the “Vivaldi” due to the shape of the design which mirrors that of musical notes.

Before the cedar design can be used in real-life applications a circuit must be developed to control the frequency-switching components on the antenna. Husseini estimates that the design of such a circuit will probably take a further semester, although responsibility for such an endeavor may be handed over to a telecommunications company with previous experience and greater financial resources.

Despite their integral role in the creation of the cedar antenna, those involved in the design process do not stand to benefit financially if the antenna is used in real wireless applications. One of the requirements for Ph.D programs is to have work published. Once this work is published it cannot be patented. “The moment we publish, it becomes an open source and anyone can take it,” explains Kabalan.

Copyright The Daily Star 2012.