An electrically tunable low frequency electromagnetic energy harvester

This paper reports the design, fabrication and experimental results of a low frequency electromagnetic energy harvester on FR4. The resonant frequency of the device is tuned electrically by using a generalized load (a capacitance in parallel with a resistance) instead of conventional resistive load. The device produces a maximum load power of 57 μW across 3310 Ω resistive load at 37.5 Hz of untuned resonant frequency under 0.1g input acceleration. Later, the resonant frequency of the device is experimentally tuned up to 37 Hz successfully by changing the load capacitance from 0 to 10 μF. Though, this tuning comes with reduction in output power. It is observed that only 8.5% of the untuned maximum load power is obtained at the limit of the tuned range.