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.

The topic of the paper is analysis of feasibility of surface acoustic wave vibration sensors for linear electronic warning systems. In linear warning systems localisation of the object is realised by pointing out the sensors which detect vibrations caused by the object. The information sent out by the detector enables identification of the sensor and its state. The sensor contains surface acoustic wave delay line in four-terminal network. The delay line is formed at the surface of piezoelectric plate. The vibrations of the plate are caused by vibrations of the medium surrounding the sensor. The frequency of the input signal is equal to the working frequency of delay line. The phase of the output signal is shifted in comparison with the input signal. The frequency of the phase shift would be equal to the resonance frequency of the sensor plate. The change of the output signal amplitude would be proportional to the amplitude of plate vibrations. The measured amplitude and frequency of the output signal would be registered by simple electronic devices. The measurements give us knowledge which sensor vibrates and the intensity of these vibrations. Such sensors enable construction of the electronic warning system.

In the paper feasibility analysis of the surface acoustic wave based electronic warning system was presented. As a transducer in the system the surface acoustic wave delay line was proposed. It is fabricated in standard single mask process as a pair of interdigital transducers placed on the top of piezoelectric crystal substrate. Transducer is a plate with rectangular cross-section and it converts all environmental vibration to electric signal. From electronic point of view it was considered as a two-port network. Necessary condition for proper sensor operation is that the input signal frequency from external generator should be close to central frequency of delay line. Principle of operation of the sensor is that the measured phase shift of high frequency signal has frequency equal resonant frequency of vibrating plate and its amplitude is proportional to vibration amplitude of transducer. The environmental vibrations are defined by amplitude of the output signal and the threat location is pointed by resonant frequency of excited transducer. The described above principles of sensor operation allow us designing electronic warning system consisting of many sensors with different resonant frequencies of transducers. Output signals from precisely located sensors contain all necessary information about the whole warning system. This information is easy to transmit and detect by simple electronic circuits based on phase detector and proper data acquisition system, for which necessary conditions are presented.

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The paper presents surface acoustic wave vibration sensor electronic system. The system cooperates with surface acoustic wave delay line. The sensor has been designed for electronic warning systems. The sensor is a four-terminal network. In the system, there is a cascade connection of sensors by means of coaxial cable. Test signal and constant supply voltage are jointly sent between sensors. Separating the signals, their summation and amplification of test signal as well as matching the line to impedance 50 Ω are performed by surface acoustic wave vibration sensor electronic system. The electronic system devices and the making of them are discussed. System development of such a sensor is presented and its design is analysed. Experimental examination results of surface acoustic wave vibration sensor are presented. Parasitic effects occurring in vibration sensor electronic system operation connected with electromagnetic coupling and ground current coupling are discussed.

The paper is concerned with compound series of unitary groups, of rotation groups and point groups for classification of various tensor components i n crystals, which have various components in relation to a rotation group and a permutation group. For this purpose the following series Ulvly 1 R[,ly 3 ... 3 G is being introduced, where y represents a vector (a pseudovector); then the number of various branches which end with a unit group G determines the number of various tensor components, which have obvious properties for reduction symmetry. When classifying in this way, a new interpretation of selection principles for phase transitions in crystals can be introduced.Fur verbundene Serien von unitiiren Gruppen, Rotationsgruppen und Punktgruppen werden verschiedene Tensorkomponenten in Kristallen klassifiziert, die verschiedene Komponenteii bezuglich einer Rotationsgruppe und einer Permutationsgruppe besitzen. Dazu werden die folgenden Serien U [ y l y 3 Rl,,lv 3 ... 3 G eingefiihrt, wobei y einen Vektor (einen Pseudovektor) darstellt; dann bestimmt die Zahl der verschiedenen Zweige, die mit einer Einheitsgruppe G enden, die Zahl der verschiedenen Tensorkomponenten, die deutlich Eigenschaften der Reduktionssymmetrie besitzen. Durch eine derartige Klassifizierung kann eine neue Interpretation von Aaswahlprinzipien fiir Phasenubergange in Kristallen eingefuhrt werden.

This work presents results of experimental tests of surface acoustic wave vibration sensor. Measurements of the static sensitivity, resonance frequency, frequency amplitude characteristics and linearity were carried out. Measurements were carried out with the help of the acceleration of gravity and a digital oscilloscope.

The analysis of vibrations excitation in surface acoustic wave vibrations sensors is the aim of our work. The sensors are parts of electronic warning system which is intended to be mounted at fences of guarded object. The vibration excitation with expected acceleration is needed during experiments. Elements of fences are replaced by tense strings for experimental purposes and the surface acoustic wave vibration sensors are fastened to these strings. Analysis of the assembly string-sensor takes into account not only the mass of sensor but its moment of inertia, too. Free vibrations of string-sensor assembly are considered. The standard excitation by pulling off string in chosen point causes vibrations. The normal vibrations of assembly (frequencies, orthogonal set of normal functions) are calculated and used for calculations of free vibrations. The spectrum of the standard free vibrations is calculated. The results will be used in the experimental stand. The calculations enable excitation of vibrations with expected spectrum. The stand enables tests of the whole warning system. The thresholds of detection and reaction at concurrent intruder alarm will be investigated at this laboratory stand.