The Research And Design Of The Radio Frequency Energy Harvesting System

With the rapid development of modern wireless communication technology,mobile communication base stations and wireless local area network(WLAN)is becoming more and more popular in our daily life.Hence the energy level of the electromagnetic in the ambient space is increasing significantly.Recycling those widespread energy has arouse our common consideration.Hence the concept of RF energy harvesting cames into being.The concept of RF energy harvesting can trace back to wireless energy transmission(WPT),which is a technology for wireless transmission of electromagnetic energy with high power density.However the RF energy harvesting technology is a technique to absorb and recycle the ambient electromagnetic energy in the surrounding area with relative low power density.Even though above two techniques adopt the rectenna(rectifying antenna)as their solution,there are some major differences in detail between the rectenna design process.The RF energy harvesting just has stepped out its infancy,there are much works to be solved such as making the system compact and integrate,improving the rectifying efficiency in the low power density area,and broadening the bandwidth of the entire system.This article focus on the research and design of RF energy harvesting system.Firstly,a dual-band RF energy harvesting system was proposed.Based on the first design,a triple-band system was designed by improving the receiving antenna and rectifying circuit respectively.The mainly content of this article is as follow:1.A dual-band RF energy harvesting system is proposed.This system adopt a planar broadband yagi antenna as the receiving antenna part,the working frequency band of this receiving antenna is 1.54-2.34 GHz.The impedance bandwidth can completely cover the GSM1800 and UMTS2100 mobile communication frequency bands.Antenna has steady directional radiation pattern in working frequency range,with an average gain of 5.5d Bi.The rectifying part of this system is designed as a dual-band rectifying circuit working on 1.8GHz and 2.1GHz frequency.The proposed circuit can achieve about 20%-45% efficiency in the low input power range from-20 d Bm to-5d Bm.The entire system can achieve about 250~350 millivolt DC power on the resistor in the outdoor ambient environment test.2.Based on the above dual-band system,we proposed a triple-band RF energy harvesting system.A broadband circular polarization antenna has been chosen as the receiving antenna of the system to better receiving the incoming various polarized electromagnetic wave.The impedance bandwidth and 3-d B axial ratio bandwidth of this antenna can both cover 1.6-2.45 GHz,which is include GSM1800/1900,UMTS2100 and 2.4GHz WLAN frequency bands,with average gain about 3d Bic.The rectifying part of the triple-band system is designed based on the former dual-band one,and add a third frequency at 2.4GHz by paralleling a circuit branch.The proposed rectifying circuit can achieve about 40% rectification efficiency at about-5d Bm input power in the real tests.The whole triple-band system can achieve about 200~400 millivolt DC power on the resistor load in the outdoor ambient environment test.The research and design of these RF energy harvesting systems may lay a foundation for the wide applications in the future.