A modular system of rectifiers for energy harvesting with wide dynamic input-range

The article proposes a novel RF-to-dc rectification system at 2.45 GHz with a 41-dB dynamic range. The system consists of a combination of three rectifiers, each one firstly designed separately for a specific range of input power (Prx). The array uses an adaptive distribution to convey the Prx in the most suitable path for maximum RF-to-dc conversion efficiency over the entire power range. The nonlinear behavior of the rectifiers is exploited in such a way that their RF input impedances are strongly dependent on the power level, thus enabling their alternate operations: the first rectifier is designed for operating in the range from -20 to about 0 dBm, the second one from 0 to 9 dBm, and the third one from 9 to 20 dBm, for an overall dynamic range of 41 dB. In the RF path of the second and third rectifiers, enhancement-mode HEMT (High Electron Mobility Transistor), exploiting self-biasing, are used as passive switches, that are seamlessly turned on and off, depending on the incoming power. In this way, the system achieves an almost complete decoupling of the three branches and only one rectification path is active for a specific input power level. When the input is below 0 dBm, the power is directed to the low-power rectifier, while if Prx increases a small amount of power flows through the HEMTs, each one connected to the proper rectifier, and, by means of a suitable dc switching network, the dc outputs of the other rectifiers are shorted.