Low-power Wireless Sensor Network Node Design Research

Wireless Sensor Networks(WSNs) is a new research subject in the field ofcommunication and information， which includes sensor techniques， wirelesscommunication techniques， signal processing techniques and so on. WSNs technologytransforms the physical signals in the real world into the logic signals in the informationworld， which increasingly promotes the reform of interactive mode between mankindand nature. WSNs are widely used in people’s life and the industrial production areas.Therefore， it has become a hot subject in technology research all over the world.However， WSNs is far different from the traditional wireless networks. Since WSNsare usually supplied with batteries， the limit of battery energy becomes the theapplications “bottle-neck” for WSNs. In most conditions， the performance of the entirewireless sensor networks will degraded singnificantly， when the battery is out of use..Therefore，reducing the power consumption of WSNs nodes and extending the workingtime of WSNs nodes have been received much attention in the design of WSNs.In order to achieve low-power-consumption design for WSNs， we carry out theresearch work from three aspects in this thesis. First， for the transmission modeselection of WSNs nodes， OOFSK and FSK transmission methods are compared intwo aspects， the bit error rate performance and energy consumption performance. Thegeneral performance of these two aspects is also provided. According to the theoreticalanalysis and simulations， we can draw the conclusions that the OOFSK has advantagesover the FSK in condition of low SNR， low modulation duty cycles. Secondly， weapply the the highly efficient Class-E power amplifier to the design of WSNs nodes. Weprovide the basic principles and performance of the Class-E power amplifier. Accordingto the jointed simulation of ADS and MATLAB， we get bit error rate influences ofClasse E power amplifier for OOFSK and FSK. The simulation results show that， theClass E power amplifier has little influence on constant envelop signals， The BERperformance loss of FSK and OOFSK are0.2dB and1dB, respectively, when theClass E power amplifier is adopted. Finally， this thesis gives a brief introduction for battery recovery effect and confirms the battery recovery effect with the batterydischarging experiments. The experiment results show that the nomorlizedcontinue-working-time of battery will become longer as the battery discharging dutycycle is smaller. The significant threshold of battery recovery gain is50%. When thebattery discharge duty cycle is below this threshold， there is no significant gain fromthe reduction of battery discharging duty cycle，. This result is very useful whendesigning the mode of the battery usage in the low-power-consumption WSNs node.