Wearable Coplanar-Fed 2.45 GHz-Rectenna on a Flexible 3D-Printable Low-Cost Substrate

In this work we demonstrate how, by 3D printing techniques, it is possible to adopt low-cost materials, generally not suitable for the construction of RF circuits and antennas, to realize a completely flexible and wearable 2.45 GHz rectenna with a good conversion efficiency. In particular, the Flexible 80A material has been considered: first, it has been characterized from the electromagnetic point of view and subsequently etched in order to realize a wearable coplanar-fed patch antenna connected to a voltage-doubler rectifier. Based on the electromagnetic field distribution, etching techniques as well as antenna stack-ups have been studied and evaluated, with the aim of minimizing the impact of the substrate losses. Moreover, a conjugate matching between the antenna and the rectifier has been adopted to avoid a lossy matching network to be realized with distributed components on the same material. Results show a very good agreement between simulated and measured performance, with an antenna gain of 3.8 dBi and a radiation efficiency of 57%. Finally, the rectifier performance has also been evaluated, showing an RF-to-dc power conversion efficiency of 50% at 0 dBm of input power.