A low power design for radio frequency energy harvesting applications

A new design for a radio frequency (RF) energy harvesting circuit, which enables capturing energy from an electromagnetic far field, is presented in this paper. First, we present the state of the art of common energy harvesting systems. Second, we introduce some important preconsiderations concerning near and far field propagation and how to calculate the expected power at the input of the system. Third, we describe the design of a RF energy harvesting system. The system consists of a quarter-wave monopole antenna, a matching circuit, an energy conversion module, an energy storage capacitor, a low-power comparator and a DC-to-DC converter. The RF energy harvester operates at a frequency band of 868 MHz and creates a pulsed output voltage of about 1.8 V at an input power of at least -6 dBm. The system can be used to power a wireless low-power sensor node. With this approach, a battery-less sensor network is made possible.