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.