From radiator to Signal Processing Antenna

This paper is dedicated to a discussion on the concept of the antenna and its evolution since its introduction as a specific device at the end of 19^th century. For many decades, antennas were mainly used as transmitting and/or receiving devices. However many additional characteristics of the antenna can be considered in wireless applications. Energy harvesting, environment sensing, backscattering are among the most interesting properties that are more and more exploited in practice. Potentially antennas can evolve from simple radiators to more sophisticated devices that can be used to build battery-less, ubiquitous and cognitive systems. New models and more complete description are currently needed for better design of wireless applications and systems. The concept of Signal Processing Antenna (SPA) is going to be a reality for many designers.