The design of wireless transmission systems able to deliver power over long distances in practical applications represent an challenging task because of the specific requirements in terms of end-to-end efficiency, robustness, and reliability. As a consequence, ad-hoc design procedures have been developed in the literature. In this framework, innovative methodologies are currently proposed to design transmitting antennas able to focus the radiated power towards the receiver while also guaranteeing simple and light architectures. The aim of this work is to discuss some of the most recent advances in this field, also envisaging the future research trends within this area.