**Pakistani scientist wins laurels
**ISLAMABAD, Jan 1: **A Pakistani scientist working at the Institute of Space Technology (IST) has invented the world’s lowest profile omni-directional antenna with dual polarisation that does not require a ground plane.
** Dr Mohammad Amin, who is listed in the biographical directory Who’s Who in the World of 2008 published by Marquis, said in mobile communications, it was important not only to have adequate signal strength, but the direction of the electric field should also be parallel with the antenna.
He said: “I have developed the world’s lowest profile antenna that can generate equal vertical and horizontal electric field components.” Mr Amin said the antenna had a helical shape and had a feed at the centre of the helical section of one side. Furthermore, the antenna, known as side-fed bifilar helix antenna, does not require a ground plane.
However, the scientist said that because of the scattering environment, a part of vertical electric field generated at the transmitter could turn into horizontal and vice versa.
According to Dr Amin, an antenna capable of receiving or generating equal amplitudes of electric fields both in horizontal and vertical directions will improve reception by providing diversity.
He said the simplest form of such an antenna was a crossed dipole, which consisted of two dipoles orientated at 90 degrees to each other. The crossed dipole provides equal vertical and horizontal electric field over narrow regions and its height would be approximately half wavelength, he added.
Dr Amin said many applications such as in mobile handsets and aerodynamic surfaces at jet speeds the antenna had to be low profile either to appeal the aesthetics or to reduce air resistance.
In addition, equal amplitude of electric field both in vertical and horizontal directions is required in all directions for reliable communication, he added.
Source: Dawn
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