Antenna Design And Circuit Optimization Of RF Energy Harvesting System

Harvesting energy from the environment for powering sensor nodes have been increasing in popularity as the rapid growth of wireless sensor networks.Compares to vibration and solar energy extraction,radio frequency(RF)energy has several advantages such as the limitless of time and weather,it is a very clean energy form at the same time.The large amount of communication devices and cellular base stations provide electromagnetic wave energy constantly.In this paper,exploration and researches have been made to antenna design and circuit of the energy harvesting system.Through theoretical analysis,software simulation and experimental validation,this paper designed a energy harvesting system and made effectiveness evaluation.More specifically,this thesis covers:1.We introduced the antenna theory and designed three different types of antenna for RF energy harvesting,one of those antennas worked in dual-band.For 4G communication band,we designed a new Z-shape coplanar wavaguide antenna worked on 2.1GHz,the return loss on the resonant frequency is-22.58 dB and the-10 dB bandwidth is 340 MHz.For cellular communication network band,we designed and fabricated a new type dual-band planar monopole antenna resonant in 900 MHz and 1.8GHz,the return loss achieved of each band is-23.8dB and-20.4dB respectively,and the-10 dB bandwidth of each band is 100 MHz and 260 MHz respectively.A 2×2 microstrip antenna array was also designed for the wifi band.Antenna pattern measurements of the antenna have been performed in the microwave anechoic chamber.2.For the purpose of rectify circuit optimization,modeling analysis of RF energy harvesting system was made to deduce DC characteristic equation and calculation model with the input impedance of the diode voltage multiplier circuit,impedance matching of the two types of models are also analyzed.The rectifier circuit and voltage boost circuit are designed by using ADS simulation software,and the frequency is well matched with the frequency of the antenna.A 9 order Villard voltage multiplier circuit was fabricated and the measurement results illustrated a good boost effect,the DC output voltage of the circuit could reach 25 V with a 20 dBm input RF power.Linear Technology's LTC3459 chip was used as a voltage stabilizer circuit.3.Finally,the overall harvesting system tested in a lab environment,extracting energy 0.5m away from the source,The G-shape antenna worked on 900 MHz achieved more than 10 V DC empty-load output voltage,7.7V with a 33kΩ load,Energy harvesting efficiency of the collection system and the antenna circuit reaches 64%.The output voltage with a load for 1.8GHz is 3.8V and efficiency is 34%.For Z-shape antenna worked on 2.1GHz,output voltage with a load is 4.99 V and efficiency of the system is 30.8%.