An alternative rectenna design approach for wirelessly powered energy autonomous systems

In this paper, we propose a new perspective for the rectenna design aiming to provide the start-up conditions, for the power management unit (PMU), even if the available RF power is very low. By theoretical and numerical results we demonstrate that energy autonomy of state-of-the-art PMU can be supported by RF received power levels as low as 20 μW. To ensure the best system efficiency for the PMU regime a two-rectifier switched-topology is introduced to operate alternatively in the start-up and in the regime phases of the PMU. This design is carried out by a CAD procedure based on the concurrent use of EM simulation, harmonic balance (HB) and time domain techniques. This way the actual nonlinear behavior of the rectenna in the time-domain design of the PMU is rigorously accounted for.