Study Of Conformal Rectenna For RF Energy Harvesting System

By adopting the Ratio Frequency(RF)energy collection technology,the RF energy around the environment can be collected and be converted to DC voltage,which can be used in some small electronic devices instead of traditional batteries.The most central part of the RF energy harvesting system is the rectenna.At present,the technology of rectenna is not mature,and there are still many problems to be solved in improving the conformability with it's host carrier,miniaturization,broadband,reducing the working collection power and improving the working efficiency of rectenna.In this paper,the conformal rectenna with low input power in single band and wide band are studied.The details are as follows:1)A conformal circularly polarized rectenna working at 2.45 GHz is presented.Firstly,a conformal circularly polarized ring-slot antenna with harmonic suppression function is designed.The antenna has good circularly polarized radiation with the gain more than 4d Bi in the 2.4GHz-2.5GHz band.Then,a rectifier circuit based on a T matching network is designed.When the input power of the rectifier circuit is-5d Bm,-10 d Bm and-20 d Bm at 2.45 GHz,the measured energy conversion efficiency is 54%,47%and 23% respectively.Finally,the rectifier circuit is integrated with the receiving antenna on the same dielectric substrate,the output DC voltage of 312 m V can be measured at 2.45 GHz with the input power of-10 d Bm.The rectenna can work well when it is conformal on any surfaces of cylindrical carriers with the radius of more than 30 mm.2)A conformal wideband circularly polarized rectenna is designed.First,a wideband conformal circularly polarized C-slot antenna is designed.Moreover,the left edge of C-slot is optimized into a second-order stepped structure,which greatly expanded the axial ratio bandwidth of the antenna.The measured impedance bandwidth and axial ratio bandwidth of the antenna are 52.6%(1.75-3 GHz)and 62.5%(1.65-3.15 GHz),respectively.Then,a broadband rectifier circuit with low input power is designed.The impedance matching circuit of rectifier circuit consists of four parts: LC band-pass circuit,L-type low-pass circuit,compensation inductance and resonant inductance.The measured energy conversion efficiencies of rectifier are more than 35% in the 1.75-2.5GHzfrequency band at the input power of-10 d Bm.Finally,the rectifier circuit is integrated with the receiving antenna on the same dielectric substrate.The output DC voltage of315 m V,376 m V ? 295 m V can be measured at 1.8GHz,2.1GHz and 2.45 GHz at the input power of-10 d Bm.The rectenna can work well when it is conformal on any surfaces of cylindrical carriers with the radius of more than 30 mm,used to collect radio frequency energy in the 1.75-2.5GHz.