Full-printed inductors on flexible plastic foils for electromagnetic energy harvesting: Fabrication, characterization, modeling

The fabrication, characterization and modeling of fully-printed inductors on flexible plastic foils are presented. An appropriate equivalent circuit is proposed to model the frequency behavior of a screen-printed spiral inductor on PEN (polyethylene naphthalate) substrate. A cascade open-short-thru de-embedding method for microwave on-wafer characterization is applied. The paper is focused on high-value inductors and the results are compared from 40 MHz to 10 GHz. Five turns inductors present a 90 nH and 105 nH inductances with a self-resonance frequency equal to 1.3 GHz. These inductances are sufficient to be used for electromagnetic energy harvesting in UHF (ultra-high frequency) RFID (radio-frequency identification) passive tags if their quality factors are improved.