investigation on the increase of single antenna gain for the improvement of frequency-diverse arrays performance

This thesis aims to analyze a far-field WPT link at microwave frequency proposing a solution for increasing the radiating performance of frequency diverse arrays (FDAs). FDAs are powerful radiating systems with interesting features for wireless powering purposes. However, in real environments the signal strength attenuation due to the distance between source and destination is a critical challenge for the feasibility of far-field WPT systems. Even though the path loss effect cannot be avoided, significant efforts are needed in order to design innovative transmitting systems with enhanced radiating performance. In this work, an extensive analysis has been carried out to increase the gain of the single antenna element, to be successively embedded within a FDA architecture. By starting from a multi-layer patch antenna working a 2.45 GHz, three main techniques have been studied and implemented to pursue a gain maximization. The first and second methodologies are based on a superstrate layer placed on top of the original patch. A high density superstrate (Taconic CER=10) has been used for the first case, whereas a holey superstrate (Rogers RT5880) for the second one. The third technique is based on the presence of a parasitic antenna element on top of the main patch antenna. This last approach has provided the highest gain improvement of almost 3 dB with respect to the initial patch design. Successively, the results of that investigation have been exploited for simulating the behavior of a linear FDA of 8 antennas operating at 2.45 GHz, in which each element operates as a high gain patch antenna. The obtained results show a great improvement of the FDA beam pattern in terms of power transfer capability when high gain radiators are involved. This solution increases the robustness of FDAs when their application in real environments is envisaged, and it represents an important contribution for the feasibility of far-field WPT technology.