Analysis of characteristics of grating lobes generated with Gaussian pulse excitation by ultrasonic 2-D array transducer

Characteristics of ultrasonic beams generated by two-dimensional periodic array transducers have been analyzed through simulations based on the Rayleigh–Sommerfeld model. An excitation waveform is treated as a Gaussian pulse in the simulations with an enhanced model for a continuous wave. Acoustical fields for focal beams, waveforms and spectra are calculated and compared among Gaussian pulses with various pulse lengths. Theoretical generation conditions for propagation directions of grating lobes with the center frequency of the excitation waveform are derived from the first order term of the delay law for an angled focal beam. The theoretical results show good agreement with the simulations. Furthermore, the theoretical condition expressions are extended for high-frequency grating lobes as a specific phenomenon for short pulse excitation.