In wireless antenna applications it is desirable to receive and transmit signals from a wide variety of possible angles, yet standard antenna elements rarely offer this type of performance and are never completely omnidirectional.Researchers at Stellenbosch University have developed a new antenna design that achieves near hemispherical coverage with reduced power gain variation and improved polarisation discrimination capabilities when compared to conventional dual-polarised dipole antennas.
The proposed antenna element can function as a radiating element for antenna arrays in applications where a physically fixed system must electronically scan the whole of space above the horizon for signals. Alternatively, such an antenna can be mounted with arbitrary physical orientation, as determined by available surfaces, and have the gain maximized in any required direction. In a MIMO configuration, the ability of the antenna to receive signals from antennas scattered geographically extends beyond that of standard antenna elements. The antenna can be integrated into micro Base Transceiver Stations (BTS) for wireless communication networks or as a 4-port Multiple-In-Multiple-Out (MIMO) antenna, both in Line-of-Sight (LOS) and Rich Isotropic Multipath (RIMP) environments.
The invention combines co-located monopole and crossed dipole antennas to enable transmission to any direction within a full hemisphere. By utilizing weighted combinations of four different modes of excitation, a radiation pattern is obtained which contains no nulls, and only a small variation of gain within a hemisphere extending down to the horizon.
Extensive laboratory testing of the antenna was performed.
The antenna is patent protected by the following patents:
D.S.V. Prinsloo, PhD student at Stellenbosch University
Prof P. Meyer, Professor of Electric and Electronic Engineering at Stellenbosch University
Prof R. Maaskant, Assistant Professor at Chalmers University of Technology (Gothenburg, Sweden)
Prof M.V. Ivashina, Associate Professor at Chalmers University of Technology (Gothenburg, Sweden)