Avoiding diffraction grid effect in ultrasonic fields of 1-3 PZT polymer piezocomposite transducers

Improvement of sensitivity in ultrasonic fields of piezocomposite transducers is limited because of diffraction effects arising from the periodic structure. We present a theoretical and experimental study of ultrasonic fields of 1-3 PZT polymer piezocomposite transducers. The relation between the composite grid periodicity and the wavelength is critical in order to obtain a far field similar to that of homogeneous transducers. If diffraction grid effect is present, it results in an important energy loss in the higher diffraction orders. These higher orders perturb the central field of the transducer because of multipath contributions to the main lobe caused by reflections from the boundaries of the test sample.