Fig. 3: PMUT design basics which can be divided into two classes based on PMUT structure and function.

a Snapshot of a vibrating PMUT idealized by a modified parabolic shape. b Important structural layers of a PMUT – the device layer and the active piezoelectric layer. c Schematic of the working mechanism of an equivalent flexural rigidity dominated plate type PMUT. d Schematic of the working mechanism of a tension dominated membrane type PMUT. e Dependence of frequency parameter on kappa squared clearly showing three different working regimes³². f Dependence of a PMUT’s central deflection on the radius which also depicts three different working regimes. g Basic equations governing the vibration of a PMUT. h Lumped parameter model of a PMUT transmitter. i Lumped parameter model of a PMUT receiver. j A PMUT as a transmitter in the size-tension subspace³². k A PMUT as a transmitter in the stack thickness subspace³². l A PMUT as a receiver in the size-tension subspace³². m A PMUT as a receiver in the stack thickness subspace³². n A PMUT as a transceiver in the stack thickness subspace³². All pictures have been adapted with permission