A Pakistani scientist, working at the Institute of Space Technology, has invented the world's lowest profile omni-directional antenna with dual polarisation that does not require a ground plane.
The scientist, Dr Muhammad Amin, listed in biographical directory published by Marquis 'Who's Who in the World' of the year 2008, said that in mobile communications it is 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."
The antenna, he said, has a helical shape and has 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, he said, because of the scattering environment, a part of vertical electric field generated at the transmitter can turn into horizontal and vice versa.
Amin said that an antenna capable of receiving, or generating, equal amplitudes of electric fields both in horizontal and vertical directions would improve reception by providing diversity. He said that the simplest form of such an antenna is a crossed dipole which consists 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 that many applications, such as in mobile handsets and aerodynamic surfaces at jet speeds, the antenna has to be of 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.