A Compact Thévenin Model for a Rectenna and Its Application to an RF Harvester with MPPT

This paper proposes a compact Thévenin model for a rectenna. This model is then applied to design a high-efficiency radio frequency harvester with a maximum power point tracker (MPPT). The rectenna under study consists of an L-matching network and a half-wave rectifier. The derived model is simpler and more compact than those suggested so far in the literature and includes explicit expressions of the Thévenin voltage (V_oc) and resistance and of the power efficiency related with the parameters of the rectenna. The rectenna was implemented and characterized from -30 to -10 dBm at 808 MHz. Experimental results agree with the proposed model, showing a linear current⁻voltage relationship as well as a maximum efficiency at V_oc/2, in particular 60% at -10 dBm, which is a remarkable value. An MPPT was also used at the rectenna output in order to automatically work at the maximum efficiency point, with an overall efficiency near 50% at -10 dBm. Further tests were performed using a nearby transmitting antenna for powering a sensor node with a power consumption of 4.2 µW.