Figure 3.

Directive Complex Sensor (DCS) designed to priviledge the [0°–90°] angular sector (a). The geometry of the piezopatches is generated by a quaternary phase quantization and a subsequent binary amplitude quantization of the continuously modulated shape functions illustrated in Figure 2. (b) 2D-FT of the complex quantized shape function: due to quantization procedure, it is not perfectly matched to the desired one depicted in Figure 2b but it is clearly asymmetrical.