Design And Implementation Of FM Backscatter Communication System Powered By Microwave Energy

Recently,the rapid development of large-scale Io T(Internet of Things)technology has led to a dramatic increase in Io T devices.However,with the increase in the number of Io T nodes,there are new challenges in the complex application scenarios and power consumption control of devices.On the one hand,device power is often reduced to meet the requirements of low power,but this limits communication distance.On the other hand,more complex application environments place higher requirements on equipment maintenance and battery replacement.At present,backscatter communication technology can greatly reduce power consumption.However,the communication distance of traditional passive backscattering tags is very limited,and traditional active backscatter tags achieve long-distance communication with high power consumption and expensive illumination equipment.Therefore,in view of the above problems,the low-power long-distance backscatter communication of tags and microwave power supply methods are researched.First,in order to increase the communication distance,tunnel diode is used in the tag as a reflection amplifier in this paper.The reflection amplifier made by tunnel diode has a power consumption of only 90μW and a reflection gain of up to 23 dB,which can cover the entire FM frequency band.In order to further reduce the power consumption,the traditional irradiation source is no longer used in this paper,but the ambient signal is used as the irradiation source.In this paper,the FM broadcast signal with wide coverage,high strength and free publicity is used as the irradiation source.By re-modulating the FM signal and using the software radio platform to receive and demodulate the reflected signal,the information transmission has been successfully achieved,and the communication distance of 20 meters is achieved at the transmission rate of 1kb/s.Compared with the traditional tag,it has the ability to increase the communication distance by 4～5 times.Therefore,an implementation method of FM backscatter tag with low power consumption and long distance is provided in this paper.Second,in order to expand the communication scenario,the traditional battery power supply method is changed and the method of collecting microwave energy is adopted to supply power.A rectifier for the FM frequency band is designed,which can convert the electromagnetic wave energy in the FM frequency band to DC,and the conversion efficiency can reach up to 64.42%.The rectifier has high conversion efficiency under the strength of irradiation power above-20 dBm.Furthermore,the optimum load value and maximum power transmission conditions of the rectifier are obtained through simulation and experiment.Then,combining this rectifier with boost and energy management,the tag can be powered by microwave energy.And the energy harvesting module can still supply energy to the backend equipment normally under the power supply as low as-19 dBm.Therefore,an efficient method for harvesting microwave energy in low-power FM band is provided in this paper.Then,through the control of the single-chip microcomputer,the tag realizes the time-sharing transmission of digital and voice information.The system power consumption is 153μW during digital transmission,and digital information can be transmitted by collecting microwave energy.By further improving the information transmission rate,the maximum digital information transmission rate of 100 Kbps can be achieved,which expands the usage scenarios of tags.The voice information adopts the analog modulation method,and the voice can be received through the software radio platforms or the mobile devices that c an demodulate the FM.Therefore,an implementation method of long-distance backscatter communication using microwave energy is provided in this paper.Finally,the problems in the process of design and testing are summarized,and the direction of future optimization and modification is pointed out.