Modeling and Optimization of CMUTs Arrays for Improved Transmission and Reception Performance in Immersion

Capacitive micromechanical ultrasonic transducers (CMUTs) have widespread applications in ultrasonic imaging, therapeutic treatment, and underwater applications. Reasonable design of their array structures essentially determines the performance in aforementioned applications. However, there is a lack of a systematic investigation on the design strategies and effects of structure parameters of CMUTs arrays, significantly impeding their performance improvement. This article constructs explicit and accurate analytical expressions for the main performances of CMUTs arrays in immersion by introducing the accurate distributed membrane deflection. Based on these theories, the influence laws of the aforementioned structure parameters on the CMUTs array performances are analyzed and summarized in detail, including the transmitting power, receiving sensitivity, focal length, beamwidth, and so on. These theories and array performance variation rules are well validated by finite element method (FEM) simulations and experiment results of our fabricated CMUTs chips. It is demonstrated by the FEM simulation that, under specific array structural parameters, the fill factor has a significant improvement effect on CMUTs bandwidth (up to 173%). The multiarm spiral array and ring-shape array reduce the sidelobe level (62% less than that of conventional square arrays) and improve the transmitting power and receiving sensitivity (35% and 33% larger than those of conventional circular arrays), respectively. Based on these, CMUTs array design and optimization strategies are provided for typical ultrasonic applications. This study provides a theoretical basis for the design and application of CMUTs arrays in immersion, which will accelerate the development of CMUTs devices.