Beam profile measurement and optimization in the high-frequency annular array transducer

Annular array transducers are multi-elements and arrayed in annular. By providing a delay line for each element, we can vary the focal length, so beam width is narrower, and the SNR is better than the conventional single element transducers. The annular array utilized in these studies consisted of four elements, had a geometric focus of 18 mm, and a center frequency of 30 MHz. We measured the voltage of received signal and the delay time of the case with a wire phantom in the case of 16 types, and practiced the synthetic focusing. The voltage of received signal was maximal at 18 mm as expected. For the delay time, the measured values with the theoretical values were consistent with the overall trend, but the error occurred between the both values. When we practiced the synthetic focusing by shifting the amount of the delay time, depth of field became approximately twice.