Analog Signal Processing And Data Acquisition For Wireless Sensor Networks

Wireless sensor network (WSN) is becoming the hotspot for study and developmentin academe with the growing concern about environment, safety and health. Study onsensor node is still in cradle, without systematic analysis and design up to now. Thisessay will classify sensor node generally at first, then introduce schemes and circuitstructures separately for two kinds of sensor nodes and specify author'sconsiderations for circuit design. Finally examples will be given.Firstly, wireless sensor network will be introduced. The basic concept and applicationenvironment for WSN will be discussed and functions of three sub-systems whichconstitute WSN will be presented.Secondly, detailed analysis will be made for sensor nodes in WSN. FOM will bepresented as merit of feature for circuit structure. According to different applicationenvironment, sensor nodes will be classified into power-priority type andprecision-priority type, respectively, and circuit schemes will be presented as well.Thirdly, based on design and circuit set above, temperature sensor frontend errormodel, as one of power-priority type examples, will be analyzed, and differencemeasure method will be presented; design and choice of low-pass A/D convertor willbe discussed. Based on summary of theory, building process, power, noise and othernon-ideal factors for Sigma-Delta A/D convertors, a power-optimized design processfor Sigma-Delta modulators will be presented, which can achieve highest index forSigma-Delta A/D convertors at present. With the aid of the process, a 10-bit 2nd-orderSigma-Delta A/D convertor is realized.At the same time, based on design and circuit set above, bio-medical sensor node, asone of precision-priority type examples, will be introduced. Feature of its frontendoutput signal will be presented and conditioner circuit will be analyzed. The designprocessing scheme of modulating delicate biology-medical sensor signal to highfrequency has been realized, in which effect the 1/f noise of the circuit has beenovercome successfully and extremely high precision design method applied. Zerooptimization of the noise transfer function and circuit durability of Sigma-Deltamodulator will be analyzed with the power-optimized design process for Sigma-Delta modulator being applied. Zero optimization method will be added to realize 4th-orderband-pass Sigma-Delta modulator with dynamic range achieving 81 dB.Finally, the tape-out chip and related testing for temperature sensor node has beenmade. Compared with results in literature, the effectiveness of design method forpower-priority type sensor node is proved. Measured results for bio-medical sensornode are implemented. Compared with results in literature, the effectiveness of designmethod for precision-priority type sensor node is proved.