Tunable energy harvesting on UHF bands especially for GSM frequencies

Abstract

Metamaterial-based energy harvesting structures operating at GSM 900 and GSM 1800 frequency bands have been proposed. The basic structure is composed of four nested U-shaped elements on the front and back side of the dielectric substrate, with a 180° relationship between the front and back resonators. As energy harvesting capability is directly related to the quality of absorption, with the aim being perfect absorption, there is an air gap to allow tuning of the resonance frequency, and copper plate follows the air gap to facilitate the perfect absorption of electromagnetic waves, which is verified by means of simulation and experimental tests. A set of simulations and experimental study were further carried out to demonstrate incident and polarization angle dependency, the effects of Schottky diodes, and the optimal orientation of the U-shapes. Spectrum analysis and DC voltage measurements across the HSMS 2860 Schottky diode are also presented to test the energy harvesting capability: the spectrum analyzer shows a 40 dBm difference, while 81.7 mV maximum DC voltage is observed at 900 MHz. The simulation and experimental study results, while displaying several differences, do suggest that the proposed design can be used for running low-energy consumption devices such as sensors and switches.