Nov_Dec_AMP_Digital

A D V A N C E D M A T E R I A L S & P R O C E S S E S | N O V E M B E R / D E C E M B E R 2 0 2 0 1 9 thickness(78µm=2×1500m/s÷37.6MHz), the appearance of four wave fronts, which is the equivalent of 2 wave cy- cles, was reasonable. Figure 7c shows that the acoustic waves continued to be launched, propagated through the water, and reached the top of the water load. Figure 8 displays the pulse-echo and spectral responses of the 32×32 array model from this simulation. The center frequency of the 2D ar- ray was 37.8 MHz and -6 dB frequen- cy points were found at 32.4 MHz and 43.8 MHz, giving 30% bandwidth, as shown in Fig. 8. This array bandwidth well preserved the 32.3% bandwidth of the PMUT single cell model. In the time-domain, the pulse-echo response gave a clearer signal than those report- ed by Kim et al. [8] . This was attribut- ed to a greater area of the 32×32 array being covered by PZT thin films, which are stiffer (26.5 to 115.4 GPa) than PI (8.5 GPa) [13] . Consequently, the PZT stiff- ness compensated for the compliance of the PI substrate, giving a clearer sig- nal with less oscillation decay time while preserving the bandwidth. Crosstalk profiling discovers un- wanted cell to cell interference, which may degrade the performance of an ar- ray transducer. To determine cross-talk Fig. 8 — Pulse-echo and normalized spectral responses of the 32×32 array model. (a) (b) Fig. 9 — Two driving cases of the array model for crosstalk profiling, (a) single diaphragm and (b) single cell driven. Fig. 10 — Crosstalk profiles of the array in two driving cases – (a) single diaphragm, and (b) single cell driven. (a) (b)