Bioinspired US sensor for broadband applications

Ultrasonic Transducers Shaped in Archimedean and Fibonacci Spiral: A Comparison

“…No center frequency was, therefore, observed in the spectrum; so, not a single value of Q factor could be determined for the proposed transducers, but many Q factors can be associated to each resonant frequency. A similar situation was found for the logarithmic spiral geometry, even if its spectrum appeared broader and less selective [17]. What is important to emphasize about Figure 8 is the presence of multiple resonances that would represent multiple semi cylindrical resonators, each of which is ruled by the classical theory of curved, clamped film.…”

“…PVDF is a semi crystalline fluoropolymer, characterized by excellent piezoelectric and pyroelectric properties, chemical resistance, and mechanical strength [31]. Recently, a logarithmic spiral-like US transducer, which was inspired by the shape of the mammalian cochlea, demonstrated significant improvements in terms of bandwidth and omnidirectional directivity [16,17]. The shape of the cochlea has been also associated with the Archimedean and Fibonacci spirals [19,20], and this prompted us to design transducers folded according to these geometries for in-air transmission and reception at low-frequency (20-80 kHz) US.…”

“…The Fibonacci geometry had better performances at low frequency (20 kHz), especially as a receiver. Comparing the SPL and S values related to the Archimedean, Fibonacci, and logarithmic [17,18] spiral shaped transducers, it was clear that the logarithmic spiral resulted as the best electromechanical device to emit and detect ultrasonic signals. The frequency response of a piezoelectric US transducer usually has a band-pass shape, which determines the range of frequencies over which the transducer itself can operate with the highest efficiency in terms of energy conversion.…”

A Recursive Algorithm for Indoor Positioning Using Pulse-Echo Ultrasonic Signals

“…The transmitter was characterized by a sound pressure level (SPL) of 105 dB, considering a reference pressure of 20 µPa (0 dB) at 0.3 m. The receiver, instead, had a sensitivity of −80 dB, considering a reference sensitivity of 10 V/Pa (0 dB). Both unimodal transducers had a bandwidth of 5 kHz [ 25 , 43 , 44 ]. The acoustic beam was generated by driving the PVDF transmitter with a pulse of 10 sinusoidal cycles at 60 kHz, with a peak-to-peak voltage of 2V (Tektronix AFG3102), amplified by 36.5 dB through a power amplifier stage.…”

“…Conversely, in-air ultrasounds, which usually range from 30 to 120 kHz, are poorly suitable in the case of long distances and for the most sophisticated fine-grained local positioning systems (LPSs), because of the signal wavelength, and the wide lobe of irradiation of the available transducers [ 14 , 20 ]. Recent literature reports different attempts to overcome the limitation of commercially available transducers in terms of bandwidth, sensitivity and directivity, by introducing novel geometries and by the optimization of acoustic wave propagation [ 7 , 21 , 22 , 23 , 24 , 25 , 26 ]. LPSs are usually realized with a combination of multiple transmitters/receivers, properly positioned around the target area.…”