Shear Wave Frequency-Steered Beams from Electrode Arrays

Mortley (1962) has invented the interdigital transducer (IDT) to launch frequency-dependent, beam-steered bulk waves. The involved concept was recently applied to surface skimming bulk waves (SSBW's). The present investigation is concerned with the influence of the charge distribution on the relative diffraction loss of power between transducers, a factor not usually accounted for in phased array transducer design models. An isotropic wide angle Green's function approach was selected. Calculations of element factor directivity were found to indicate that double electrodes are more directive, and vary more with frequency than single electrodes. The conducted analysis shows that the relative power loss will be controlled primarily by the array factors.