Ultrasonic Transmitters Far Field Beam Pattern Altering with Boundary Conditions Design

In this study, we focus on analyzing the influences of different boundary conditions on a pot-like ultrasonic transmitter upon its corresponding far field beam pattern as well as the source level. Metal pot-like ultrasonic transmitters with a PZT piezoelectric actuating element sticking on the vibrating plate are usually used on generating ultrasonic source in proximity sensor on the application of distance measurement. In general, the vibration behaviors of a vibrating system are highly depending on the boundary conditions. The rigidity of the supporting frame to the vibrating plate manipulates the far field beam pattern as well as the source level on the design of an ultrasound transmitter. By combination of fixed, free, and partially stress-released boundary, the mode shape of the vibrating plate could be altered so as to modify the far filed beam pattern for specific application needs. In addition, for the sake of driving efficiency, the PZT actuating element placement is adjusted according to the strain distribution to have highest driving efficiency. Accordingly, the 2D Fourier transform of the source aperture is exactly the beam pattern profile in far field, and an be used as a tool to predict the far field beam pattern of different design of vibrating plate shape and boundary conditions for rapid concept proof. The finite element simulation program, ANSYS, is then used to simulate the further details of the beam pattern and source level for specific design. Experimental measurements are finally adopted to verify the theoretical analysis and simulation results. This paper illustrates the complete process from theoretical to experiment verification.