High-frequency micromachined ultrasonic annular arrays

This paper presents the development of high-frequency ultrasonic annular arrays. A high-frequency six-ring annular array was successfully fabricated with the DRIE dry-etching. The array has a total aperture of 1.3 mm and six equal area (0.25 mm
²
) rings separated by 16-¿m kerfs. The simulations prove its capability of dynamic focusing and its improved lateral resolution. The measured results of the array shows a center frequency of 105 MHz, a bandwidth (-6 dB) of 40% and an insertion loss of -20 dB at the center frequency.