Research On The Key Technologies Of Wireless Powered Low Power Consumption Sensoring Tag And System

Wireless sensor network is the basis for building the Io T perception layer,through the mass sensing nodes(also known as the sensing tag)it realizes the perception,collection,fusion processing and transmission of information such as dynamic and static parameters,location,and identity of various target objects.It has been widely used in military and civilian fields such as battlefield situational awareness,vital sign monitoring,and power grid security detection.However,the existing sensing nodes are usually powered by batteries,and their effective working time is limited by battery capacity;sensing nodes used in scenarios such as virgin forest fire prevention and monitoring of human body signs often lead to failure of wireless sensor networks due to the difficulty of replacing batteries in time.Therefore,the research and development of electromagnetic,thermal,vibration and other environmental energy collection self-powered sensing nodes and their network technologies have important scientific significance and wide application requirements.In passive wireless identification system composed of radio frequency identification tag and reader(also called collector)based on backscattering communication mechanism,a portion of radio frequency signal received by tag is converted into DC energy to realize self-powered communication function.This simultaneous wireless information and power transfer technology has been widely used.The wireless power sensing tag and system,which integrates identification and sensing technologies,has the advantages of low power consumption,long life and free maintenance,etc.,and its key technologies have become a research hotspot in the academic and industrial circles.However,the existing wireless power sensing system still has some problems,such as short communication distance,low sensing sensitivity,low data throughput,poor access fairness and low efficiency,which restrict its wide application.Based on the in-depth analysis of backscatter communication,wireless sensing,large-capacity access and other mechanisms,this dissertation adopts a combination of theoretical analysis,numerical simulation,and experimental research methods to conduct wireless power sensing tags and system.A systematic in-depth study of key technologies such as information sensing,collection,communication,and access has been carried out to improve the communication distance,data throughput,sensing sensitivity,access fairness and efficiency of the sensing system,enhance its practicability,and promote its wide application.The main research contents and innovative contributions of this thesis are as follows:1.In order to deal with the problem of unselected tag in a multi-tag system that has to continuously process the received command,consuming more energy than a single tag,and consequently requiring long charging time and resulting in low system throughput,a low power signal processing method was proposed to dynamically adjust the clock frequency and deep sleep time of MCU in the tag,which reduces the average power consumption of the tag.A tag charging time prediction model based on non-linear charging and discharging behavior is proposed,which combines the wireless charging efficiency of the tag(which varies with the distance between the tag and the collector),the energy consumed by the tag,and the number of tags in order to predict the longest supplementary charging time required by the tags of the system,reducing significantly the charging time of each tag,shortening the tag data collection time interval,and improving the data throughput of the system.A passive wireless hydrogen concentration sensing tag and system based on palladium alloy was developed.Test results show that the average power consumption of each tag is 0.43 m W,which is 20%lower than that of the similar sensing tag in the Wireless Identification Sensor Platform(WISP).When 50 tags are 4 meters away from the collector,the maximum charging time predicted by the model is 49 seconds,which is in good agreement with the measured 47 seconds,and the data throughput of the system increases by 90%.The wireless hydrogen concentration sensing tag with built-in negative resistance reflection amplifier is developed.The measured reflection gain of the tag receiving-60 d Bm@919MHz signal reaches 44 d B,and the communication distance between the tag and the collector receiving sensitivity of-84 d Bm reaches 96 meters.2.Aiming at the low sensitivity of the single-resonance magnetic field strength sensor and the high power consumption of the wireless sensing tag,a detection circuit based on the differential signal generated by the output of the dual-resonance magnetic field strength sensor and XOR gate processing is proposed.The frequency variation range of the signal is significantly higher than the output of the single-resonance sensor,which improves the sensitivity of the magnetic field strength;the square wave signal output is used to directly modulate the RF port impedance of the tag to realize backscatter communication,which effectively reduces the tag power consumption.A passive wireless sensing tag and system based on dual resonant magnetic field intensity sensor was developed.The measured magnetic field strength sensing sensitivity reached58.7 Hz/m T,which was 80.6% higher than that of a single sensor,and the power consumption is only 0.27 m W.In order to deal with the problem of low data throughput of polling passive wireless magnetic field strength sensing system,a sensing data collection method based on group measurements and cyclic sequence verification is proposed,which can reduce the sensing data collection time and improve the data throughput of the system(thanks to the group measurement method),as well as the reliability of data collection(by means of the cyclic sequence verification).A passive wireless impedance magnetic field strength sensing tag and system was designed,which takes 2.2 seconds to collect the magnetic field data of 10 tags,which is only 25.9% of the polling data collection time,and the magnetic field strength sensing performance does not change with the tag-collector distance.3.In order to deal with the problem of existing true random number generators which have complex circuit and are difficult to apply to low power sensing tag,a true random number generation method based on ADC conversion error and chaotic mapping is proposed.It adopts the ADC output data to address the stored random number in order to generate time-varying high/low threshold and time parameters,to make the ADC input voltage change continuously between the dynamic high and low threshold value,and randomly delaying the ADC sampling time.ADC conversion error and circuit thermal noise effect make the ADC output data unpredictable,and the randomness of data is further enhanced by the circuit real-time updating and cyclic iteration.The simulation and test data are verified by NIST statistical verification,indicating that this method enables the sensor tag with built-in ADC to generate true random numbers and improves the fairness of tag access in the wireless sensing system.4.Aiming at the problem of low access efficiency due to signal collision when multi-sensing tags are connected to the collector,an anti-collision algorithm based on dynamic M-ary query tree is proposed,which generates time-varying query prefixes and determines its collision position according to the total number of collision bits.The tag matched by the instruction returns the bit corresponding to the query prefix according to the mapping rule,and the tag is identified in an orderly manner after parsing the bit feature,eliminating the idle time slot and reducing the collision time slot.This method does not need to estimate the number of tags,which improves the identification efficiency and system throughput.Theoretical analysis and simulation results show that the system throughput rate reaches 89.2% when there are 2000 tags,which is 4.69%higher than that of the Bit Query M-ary Tree(BQMT)algorithm;the average access time of each tag is 1.29 ms,which is 16.9% shorter than that of the BQMT algorithm.This dissertation researches and develops wireless power supply low-power sensing tags and system design methods such as hydrogen concentration and magnetic field strength,true random number generation methods,and multi-tag anti-collision algorithms.These research results can be used in military and civilian fields such as battlefield situational awareness and power grid security detection.It has broad application prospects and is beneficial to promoting the development of the wide-area passive Io T technology industry.