An Antenna Co-Design Dual Band RF Energy Harvester

RF energy is widely available in urban areas and thus presents a promising ambient energy harvesting source. In this paper, a CMOS harvester circuit is modeled and analyzed in detail at low environmental power levels. Based on the circuit analysis, a design procedure is given for a narrowband energy harvester. The antenna and harvester co-design methodology is discussed to improve RF to DC energy conversion efficiency. We demonstrate that it is difficult to harvest RF energy over a wide frequency band if the ambient RF energy sources are weak, owing to the voltage requirements. Since most ambient RF energy lies in a few narrow bands, a dual/multi-band energy harvester architecture should be able to harvest much of the available RF energy. A dual-band CMOS energy harvester is designed and fabricated using an IBM 0.13 μm process. The simulated and measured results demonstrate a dual-band energy harvester that obtains over 9% efficiency for two different bands (around 900 MHz and around 1900 MHz) at an input power as low as -19.3 dBm. The DC output voltage of this harvester is over 1 V, which can be used to recharge the battery to form an inexhaustibly powered communication system.