Radio frequency ambient level energy harvesting
Résumé
This paper presents a study of Schottky diode rectenna (rectifying antenna) for RF energy
harvesting systems. These rectennas are suitable for wireless sensors with the rechargeable
battery technology especially at low power densities. A rectifying circuit is proposed with
single high responsivity Schottky diode for RF-DC conversion. A matching circuit is optimised
to improve not only the power transfer between the antenna and the diode but also to reject
harmonic signals. The radiating part is a monopole antenna, with a large bandwidth in the
frequency domain and an omni-directional radiation pattern in the azimuthal plane. We show
that antenna frequency response takes part in the improvement of the efficiency. The rectifier
is integrated with the antenna on a printed circuit board, leading to 30% of size reduction with
the same performance. The aim is to reach the highest efficiency with a single tone signal and
a compact rectenna. This rectenna was simulated using both Agilent ADS and Ansoft HFSS
software. An output DC voltage of 210 mV was measured inside an anechoic chamber with a
received a single tone signal of 2 μW/cm2power density. The highest efficiency of 34 % was
obtained at a power density of 1.3 μW/cm2.