Ad-hoc WPT Exploiting Multi-sine Excitation of Linear Frequency Diverse Arrays

In this work an effective solution for real-time focusing of frequency diverse arrays (FDAs) is proposed, to be exploited for intentional far-field wireless power transfer (WPT) applications. With respect to the literature where improved focusing capabilities of the traditional linear (1-D) FDAs are achieved at the expense of frequency distributions following non-linear rules (e.g., logarithmic) or complex 2-D arrangements of the transmitting architecture (e.g., concentric circular distribution), the proposed solution provides the best performance with a simpler transmitting layout. In fact, this technique proposes a multi-sine excitation for each radiating element: in this way the performance in terms of dimension of the radiated beam are improved, avoiding the well-known and critical 'S-shape' of the beampattern (BP) that is useful for radar and localization application, but not for precise and ad-hoc smart WPT. The mathematical model able to fully describe the radiation properties of the multi-sine frequency diverse array (MSFDA) is presented and the unprecedented capabilities, in terms of power focusing and ease of design, are demonstrated. MSFDA is thus proposed as an excellent solution for far-field precise WPT able to avoid sensible targets when powering: this is obtained by moving the complexity from the antenna design to the signal generation block, where advanced and sophisticated systems as software defined radio (SDR) are envisaged.