Optimization and analysis of WLAN RF energy harvesting system architecture

This paper presents the design, analysis and optimization of RF energy harvesting system for WLAN source operating at 2.4 GHz and 5.8 GHz. The system architecture comprises of RF WLAN source, wireless channel, an efficient dual band microstrip patch antenna, an impedance matching network, 4-stage voltage rectifier and a storing circuit. Matching network ensures the maximum power transfer from source to load. HSMS-2850 Schottky diodes are used in rectifier design, which provide low forward voltage and low substrate leakage. The proposed system design is used to analyze the effect of distance on RF power obtained at receiving side. The size of storage capacitor is chosen carefully such that it can store sufficient amount of charge and takes reasonable charging time. Moreover, the circuit parameters are varied to optimize the designed circuit that provides the maximum efficiency of 45% and 22% at 2.4 GHz and 5.8 GHz respectively, at a distance of 1 meter from source. Simulated results show that for received RF power of 5 dBm the system can provide 1.3 mW power across 10 kΩ load, which can be enough to energize the low power devices. The voltage supplied by the harvesting system can be increased further by increasing the number of stages in voltage rectifier according to the application but at the cost of parasitic loss.