Pattern and Polarization Reconfigurable Antennas for Gain Enhancement

Since the rapid proliferation of the wireless communication systems, the effective use of the
allocated spectrum has become vital. The desire for generating equipment that can adopt
their characteristics for different and challenging environments where excessive interference
and mobile traffic is present has been increased. Pattern reconfigurable antennas have
been an ideal candidate with conformal radiating characteristics, low cost and low power
consumption features. A pattern reconfigurable dipole antenna placed over a ground plane
with parasitic reflectors for continuous beam control has been considered as a starting point
of the project where the well known Fabry Pérot resonance modes were utilized. The
model was designed to be operating within 1.8GHz frequency band of current wireless
communication systems. The continuous beam steering over the azimuth plane has been
achieved by manipulating the surface currents along the parasitic strips by varying the
capacitance between the conducting strips of the elements. Furthermore, a partially reflecting
surface formed of periodic dipoles, was allocated on top of a metallic ground and the
radiating structure formed of a half wavelength dipole and two parasitic strips for further
gain enhancement and pattern reconfigurability. PIN diodes have been biased to switch
between "ON" and "OFF" states and achieve beam switching from a high gain boresight
direction to endfire radiation along the azimuth. Latterly the dual polarised version of
the model was evaluated for an extra step of freedom where the operating frequency has
been increased up to 3.6GHz which will be within the predicted frequency bands of next
generation communication systems. Two orthogonally positioned dipole antennas with single
parasitic elements have been used as the radiating structure. A total of four PIN diodes have
been initialized for achieving pattern reconfiguration in both polarizations where the beam
is switched from boresight to endfire directions. The evaluation process of three different
models supported with, current curves and polar plots have been extensively studied in the
thesis. Prototypes have been generated for each model and tested in a fully anechoic chamber
for the proof and validation of the theory and simulation results.