Design Of High-sensitivity Broadband RF Energy Harvesting System

Traditional wireless sensor networks usually use the battery to power these wireless sensor nodes,but the operating cost of this way is much higher and it is not convenient to replace the battery in dangerous and remote place.The radio frequency(RF)energy harvesting technology can overcome the weakness of traditional method,by collecting the ambient RF energy which can be concerted to DC energy,and supplying power to the wireless sensor nodes.The existing RF energy harvesting systems almost have a limit of bandwidth and sensitivity,and can't obtain more DC energy.This paper focuses on bandwidth and high sensitivity,a high-sensitivity wideband rectifier is designed and a broadband omnidirectional antenna is realized to perform system test.The major works are as follows:(1)In order to increase the rectifying efficiency at low input power,a improved parallel half-wave rectifying structure is presented,designing a high-sensitivity rectifying topological structure,and making fundamental analysis for it.So as to verify the validity of the highsensitivity rectifying circuit,the voltage doubling rectifying circuit and improved rectifying are simulated,and the simulation result shows that the improved rectifying circuit has much higher rectifying efficiency.Basing on the high-sensitivity rectifying circuit,the parameter sweep for load is done and analyzing the influence of load value on sensitivity and matching bandwidth.(2)In order to collect the energy of more bands,using step impedance to design the wideband impedance matching circuit with closed solution.Combining with the proposed highsensitivity rectifying structure,high-sensitivity wideband rectifier is designed.Firstly,on account of the improved dual-frequency matching technology,designing a high-sensitivity wideband rectifier operating at 1.9 GHz-2.5 GHz,when the input power is-15 d Bm,the rectifying efficiency is better than 43%;when the input power is-20 d Bm,the rectifying efficiency is better than 32%;when the input power is-25 d Bm,the rectifying efficiency is nearly 20%.Then,a high-sensitivity dual-band rectifier operating at 900 MHz and 1800 MHz is presented.Finally,combining with the above two rectifiers,a second-order parallel highsensitivity broadband rectifier is designed which can cover four bands of GSM 900 MHz?GSM1800 MHz?UMTS 2100 MHz?WLAN 2400 MHz when the input power is-25 d Bm.(3)A wideband omnidirectional antenna is designed and combining with the highsensitivity broadband rectifier,the module testing and system testing are proceeded respectively.At the same time,making a error analysis for the measurement results.