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The delay line with a surface acoustic wave for an oscillator of electric signals in some sensors DOI:10.15199/48.2018.03.38

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As selective elements of oscillators of harmonic vibration besides the band-pass filters are also used delay lines (DL) and resonators as a perspective a coustic-electric components based on surface acoustic waves (SAW). From the stability point of view we can classify these oscillators among the ones with volume acoustic waves and LC oscillators. In the article, the DL with SAW for single - mode oscillators. The oscillator with delay line The basic principle of function of oscillator with delay line is represented on the next figure (Fig. 1). The delay line (4) with SAW plugged in the feedback of amplifier (2) is a basic element. Circuits (1, 3) serve to match impedance of the abovementioned to the impedance of the electronic circuitry. Fig.1. Bloc diagram of oscillator. Because the previous signal from the input to the output of DL is delayed, examined oscillators are ones with delayed feedback. The theory of these oscillators is well known in the literature [1]. Different situation is in the case of DL with SAW, where DL themselves have narrow transmission band and their parameters differ fundamentally in this range. Physical distinctiveness of functioning of listed components which are related with phenomena of excitation, extension and reflection of SAW cause that in addition to delay, the DL´s have specific frequency dependencies of input and output admittances. Their replacement with the lumped elements RLC circuit or broad - band DL with outer selective LC is mentioned only very general. The oscillator with mismatched delay line The used delay line with SAW as a selective element of oscillator can be symmetrical or non-symmetrical. Symmetrical DL is characterized by the same input and output IDT while non-symmetrical DL has the input IDT with small number of electrodes (broadband) and output IDT with big number of electrodes (narrowband). In the contribution we will only deal with the symmetrical DL. For simpl[...]

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