A High-Efficiency Low-Cost Multi-Antenna Energy Harvesting System With Leakage Suppression

This article presents a multi-antenna RF energy harvester (MARFEH) with leakage suppression to achieve high output power and avoid the effects of interference and blind spots in the room, and all the RF rectifiers share only one buffering capacitor to achieve low cost. The proposed leakage-suppressed rectifier utilizing adaptive <tex-math notation="LaTeX">VTH</tex-math> compensation (AVC) and an RF switch can achieve self-turned-off operation to prevent power leakage due to power imbalance among all the parallel-connected rectifiers. The RF harvester also exhibits maximum power point tracking (MPPT) and a 1.8-V regulated output through a boost dc–dc converter. The MPPT is realized by an optimized on-chip perturb and observe (P&O) controller and achieves sub- <tex-math notation="LaTeX">μ</tex-math> W system control power consumption. Meanwhile, MPPT is used to estimate the RF input power to drive the AVC circuit to improve rectifier efficiency and assist in leakage suppression. The chip prototype was designed in a 180-nm CMOS process and occupies an area of 0.89 mm <tex-math notation="LaTeX">²</tex-math> . Using a single antenna with AVC and MPPT enabled, the proposed harvester achieves a power conversion efficiency (PCE) of about 37% and 38% at an input power of <tex-math notation="LaTeX">$-$</tex-math> 10 and <tex-math notation="LaTeX">$+$</tex-math> 4 dBm, respectively. The measured peak PCE is 44% at <tex-math notation="LaTeX">$-$</tex-math> 0.3 dBm. Wireless tests show that the peak output power at different test conditions is significantly improved when the number of antennas increases from 1 to 2 and to 3. Furthermore, an accurate rectifier model is presented to significantly shorten the system simulation time of the rectifier-dc–dc two-stage topology.