Modeling and Simulation of Wireless Passive Sensors Based on Surface Acoustic Wave Delay Lines
ABSTRACT The coupling-of-mode (COM) model of the interdigital transducer (IDT) is modeled by deriving and solving the COM equations which considered the voltage and resistance of the IDT finger electrodes. In addition, zero input and zero state solutions are added as the solution of the COM matrix equations. According to the IDT model and the reflectance of the reflector, the surface acoustic wave (SAW) delay line is modeled, and the wireless passive sensor based on SAW delay lines is modeled and simulated. The COM model of the wireless passive sensor can simulate the delay phase variation with the pressure well, and it can be used as an effective tool for designing and analyzing the sensors based on SAW delay lines.
Full-textDOI: · Available from: Xiangwen Zhang, Feb 01, 2015
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ABSTRACT: In this paper, we present the passive wireless sensor network based on the surface acoustic wave(SAW) resonators. The sensor node consists of the SAW sensor that is small, light, reliable, stable, sensitive, wireless and passive, so the battery is needless and its life-span is infinite. The sink node gathers data from the sensor nodes, processes the data with intelligent algorithms and transmits the needed data to the exterior network timely. The basic structure and the realization of the passive wireless sensor network are elaborated. The five main characteristics of the passive wireless sensor network, that is passive sensor nodes, simple and small sensor nodes, organized sensor nodes, intelligent sink nodes, high security, good extendibility, are explained concretely. Specially, the key techniques in our research, such as coding and decoding techniques of the sensor node, signal frequency measurement techniques of the sensor node, intelligent signal processing techniques, measurement error compensation techniques and network security techniques, are discussed exhaustively. In the end, we point out the problems at present and forecast the application prospect and research direction in the future.Networking, Sensing and Control, 2008. ICNSC 2008. IEEE International Conference on; 05/2008
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ABSTRACT: When detecting the strain with passive wireless SAW (Surface Acoustic Wave) resonator sensor, the response signal is of narrow band, high frequency, low SNR and transient attenuation. The response signal is produced only in the case that the interrogation covers the operational frequency band of the SAW resonator. Burst of sinusoidal is used in the experiment to excite the resonator, and analysis of the sensing signal reveals that the response signal is an exponential decay signal of single frequency, changes of strain lead to a shift of the resonance frequency. Torque applied to the shaft can be acquired from changes of the center frequency of the resonator. The frequency resolution of traditional FFT spectrum analysis method is limited by sampling length, which can't meet the accuracy. Parameter estimation methods, such as MLE (Maximum Likelihood Estimate) or LSE (Least Square Estimate) can be applied, but it is time-consuming to satisfy a real-time demand. In this paper, a new method of Hilbert envelope-demodulation is employed to estimate the center frequency, by which response signal can be converted to constant amplitude sinusoid. This can simplify the waveform greatly, and make it easy to determine the center frequency of the sensor. A problem of frequency detuning in envelope-demodulation is solved in this paper. For the demodulated single frequency sine wave, the resonance frequency can be got directly in time domain by finding the extreme of the waveform. The results show that this method can estimate the frequency more accurately and faster.