Summary: Beam-forming by mutual coupling effects of parasitic elements in antenna arrays
*Rubaiyat Islam, University of Toronto, Toronto, ON, Canada
Raviraj Adve, University of Toronto, Toronto, ON, Canada
An innovative way of beam-forming is described using mutual coupling effects of
parasitic elements in an antenna array. It is shown that null and mainbeam
placement can be achieved by varying the reactances at the center of the dipoles.
Traditional beam-forming is achieved by varying the complex gain of an antenna-array
. The electromagnetic waves radiated from different segments of the array combine in-
phase (and out of phase) to form the major lobes (and nulls) at desired directions.
Controlling the complex gain is expensive, as it requires sophisticated RF circuitry for
each element. As a result such antennas are available only for specialized applications
such as in the military. A cost-effective solution for mobile communication is to exploit
the electromagnetic mutual coupling between elements to achieve beam-forming .
This paper outlines the design of a five-element wire dipole antenna array. The center
element is fed by a source and the remaining four elements are placed equidistant to each
other on a circle centered around it. Variable impedances on the four parasitic elements
are controlled to place nulls and main beams at desired locations in the far-field radiation