The work in this study develops the framework for placement and actuation of novel reconfigurable dual-offset contour beam reflector antennas (DCBRA). Toward that end, the methodology for the antennas' design is defined. In addition, two separate optimization problems are stated and solved: actuator position optimization and actuation value optimization. For the former, a method termed as greatest error suppression method is proposed where the position of each actuator is decided one by one after each evaluation of the error between the desired subreflector shape and the actual subreflector shape. For the second problem, a mathematical analysis shows that there exists only one optimal configuration. Two optimization techniques are used for the second problem: the simulated annealing algorithm and a simple univariate optimization technique. The univariate technique always generates the same optimal configuration for different initial configurations and it gives the low bound in the evaluation of the error. The simulated annealing algorithm is a stochastic technique used to search for global optimum point. Finally, as an example the results of the proposed optimization techniques are presented for the generation of a subreflector shape corresponding to the geographical outline of Brazil.Index Terms-Active antennas, piezoelectric devices, reconfigurable antennas.
Recently, aperture antennas that have the ability to change their reflector shape through the use of piezoelectric actuators have been studied. The results show that those antennas can exhibit beam steering and beam shaping in the far field. However, many of the previous studies have been confined to cylindrical shape antennas. This study examines the use of "doubly curved" antenna structures to achieve better performance in controlling an antenna's coverage area. The spherical antenna is modeled as a shallow spherical shell with a small hole at the apex for mounting. Following Reissner's approach, a stress function is introduced and two governing equations are derived in terms of the stress function and the axial deflection. Next, the surface deflections are evaluated from the calculated stress function and the axial deflection. As actuators, four lead-zirconate-titanate (PZT) thunder actuators are attached along the meridians separated by 90 , respectively. The forces developed by the actuators are expanded in a Fourier series and fed into the governing equations as boundary conditions at the outer edge. Finally, the deflection versus applied voltage is calculated analytically and its effect on the far-field radiation is given.Index Terms-Aperture antennas, mechanically adaptive antennas.
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