Improved Harvested RF Energy for Cyber-Physical Energy Systems

Cyber-physical systems need to harvest renewable energy sources to work properly. Energy harvesting comes from sources such as solar radiation, ambient RF, wind, rain, or vibrations. RF energy can be harvested in the dark, or when no solar energy is available. RF is readily available, consistent, and reliable compared with energy harvesting from other sources. One major disadvantage of RF energy harvesting is the relatively low density of ambient RF energy in most locations. The goal of this work was to enhance the RF harvested power level by introducing a simple design and a small size. The proposed system included two circuits. Each circuit consisted of an RF power source, L matching element, and a single- stage voltage multiplier. The two circuits were connected in parallel via the filter and the resistor load. The ADS simulation tool was utilized to simulate the proposed design for the applied low input power range of -50dBm to 5dBm at 900 MHz. The load values were varied between 1K and 12K to determine the suitable load which achieved the optimum performance. Results showed that 3.11 mW as the top harvested power for the input power of 5dBm and output voltage of 3.5 V at the optimum load of 4 K . The maximum efficiency accomplished by the proposed system was 57%.