Textile-Based Rectennas

International audienceThe proliferation of portable devices, their growing integration into human lives and the surrounding environment, and the necessity to keep them powered have led to the increasing interest in radio frequency (RF) energy harvesting and its use in wireless mobile devices charging. The appealing features of flexible and wearable electronics, such as light weight, ease and low cost of fabrication, and the growing attention given to them, have made them a strong candidate for designing circuits like rectennas (rectifying antennas) to scavenge the ambient RF energy emitted by a large number of radio transmitters around us. The obvious advantage of harvesting this type of energy is that it is free and green. This chapter focuses on the design of wearable, and in a more general term, textile-based rectennas. It starts by discussing the electrical characterization of textiles and the methods used to estimate their relative permittivity and loss tangent. It then reviews the most recent wearable antenna designs and their applications, and examines the design and analysis of rectifying circuits used in RF energy scavenging, with focus on their sensitivity and conversion efficiency. The latest rectenna designs are also surveyed