Sifting through the airwaves: Efficient and scalable multiband RF harvesting

Harvesting ambient RF power is attractive as a means to operate microelectronics without wires, batteries, or even a dedicated RFID reader. However, most previous ambient RF harvesters have been narrowband, making mobile sensing scenarios infeasible: an RF harvester tuned to work in one city will not generally work in another, as the spectral environments tend to differ. This paper presents a novel approach to multiband harvesting. A single wideband antenna is followed by several narrowband rectifier chains. Each rectifier chain consists of a bandpass filter, a tuned impedance matching network, and a rectifier. The outputs of the rectifiers are combined via a novel diode summation network that enables good performance even when only a subset of the narrowband harvesters is excited. These techniques make ambient RF harvesting feasible for mobile applications. The techniques can potentially enable applications such as ambient RF-powered data logging sensors that upload data to RFID readers when in range.