Piezoelectric Sensors and Actuators by Stefan Johann Rupitsch

Author:Stefan Johann Rupitsch
Language: eng
Format: epub, pdf
ISBN: 9783662575345
Publisher: Springer Berlin Heidelberg

7.3.1 Transducer Excitation and Resulting Output

Owing to the fact that it is impossible to emit sound waves and analyze reflected sound waves simultaneously through a single transducer, we have to use several transducers or alternative electrical inputs instead of a pure sinusoidal excitation. For instance, short pulses as well as a finite number of sine periods represent such alternative electrical excitation signals for a single transducer. In contrast to a pure sinusoidal signal consisting of only one frequency, those alternative excitation signals feature a certain bandwidth in the frequency domain because of their limited signal duration . The bandwidth of a band-limited time signal corresponds prevalently to the frequency range between lower and upper cutoff frequency, in which the signal’s spectral magnitude3 stays above (), whereby stands for the maximum signal’s spectral magnitude (see Fig. 7.22). Regarding signal energy, also indicates the frequency range, in which the signal’s spectral energy is more than half of its maximum. Generally speaking, a signal of short duration (e.g., short pulse) offers a large bandwidth. Against that, the bandwidth equals zero for a pure sine wave since it is of infinite duration.

Fig. 7.22Spectral magnitude (amplitude response; frequency response) of time signal ; maximum spectral magnitude ; lower cutoff frequency and upper cutoff frequency ; bandwidth ; center frequency does not necessarily coincide with frequency

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