Surface Acoustic Wave (SAW) Vibration Sensors

Abstract

In the paper a feasibility study on the use of surface acoustic wave (SAW) vibration sensors for electronic warning systems is presented. The system is assembled from concatenated SAW vibration sensors based on a SAW delay line manufactured on a surface of a piezoelectric plate. Vibrations of the plate are transformed into electric signals that allow identification of the sensor and localization of a threat. The theoretical study of sensor vibrations leads us to the simple isotropic model with one degree of freedom. This model allowed an explicit description of the sensor plate movement and identification of the vibrating sensor. Analysis of frequency response of the ST-cut quartz sensor plate and a damping speed of its impulse response has been conducted. The analysis above was the basis to determine the ranges of parameters for vibrating plates to be useful in electronic warning systems. Generally, operation of electronic warning systems with SAW vibration sensors is based on the analysis of signal phase changes at the working frequency of delay line after being transmitted via two circuits of concatenated four-terminal networks. Frequencies of phase changes are equal to resonance frequencies of vibrating plates of sensors. The amplitude of these phase changes is proportional to the amplitude of vibrations of a sensor plate. Both pieces of information may be sent and recorded jointly by a simple electrical unit.

Seismic Vibration Sensor with Acoustic Surface Wave

“…In available bibliography they are not knowen or utilised. The above considerations are presented in the work [21]. For a full description of the SAW-comprising vibaration sensor designing process in Section 2 we present a modelling process of its mechanical system.…”

“…Relations between ω0 and ωr are as in identity (18). In both components of the solution (22) appears the following function:…”

“…The answer is accessible on the basis of the described model and the length of available plates. The resonance frequency of sensor plate is described by the relation (21). It depends on plate length (l) and on quantity of a concentrated mass (r) attached to the free end of sensor plate.…”

“…How great is the part depends on the unit (normal vibrations, ωn, w(x) ) and depends on activation. In the paper [18][19] [27][28] a simplified model with one degree of freedom was presented and it is shown in Figure 5. It has been used to describe the dynamics of sensor plate movement.…”

“…These SAW-based sensors are used to measure a number of physical quantities: gas concentration [5][6][7][8], temperature, pressure [9][10][11][12][13], and mechanical quantities: torque of a rotating shaft [14], stress [15][16][17], acceleration [18][19] and vibrations [20][21]. All these SAW-based sensors work on the basis of measuring changes in the delay of a surface wave due to the impact of a physical quantity being measured on its speed and the propagation path.…”