The objective of this proposed research is to design and evaluate the pilot beam for guiding retrodirective microwave power-beaming systems to maximize net energy harvested and to enable secure, long-range wireless power transfer. Retrodirective arrays are promising for Wireless Power Transfer (WPT) systems due to their rapid, simple beamforming capabilities. However, they rely on pilot beams to be transmitted from the WPT target, introducing power overhead that decreases the net harvested power, and are susceptible to interference, which can degrade beamforming accuracy. The proposed research will investigate the design and optimization of a pilot beam array integrated with the targeted rectenna array to minimize pilot beam power consumption over long distances. Furthermore, a physical-layer security approach for the pilot beam waveform, based on a novel spread spectrum technique, will be investigated to enable secure phase detection, and therefore, improve collection efficiency in the presence of interference.