热疗用环形平面换能器声场特性的研究

引入负声源，导出了环形平面换能器声场的简洁表示式，计算了单个圆环、多个同心圆环同时激励及环阵相控聚焦声源产生的声场，分析了环的宽度、环数及聚焦点位置等因素对声场特征的影响。提出根据各阵元在声场中某点产生的声压的相位来确定各阵元电激励信号的延时，此方法较根据各阵元到该点的平均声程确定各阵元电激励信号的延时，能更难确地在该点实现聚焦。

Study of sound field generated by annular transducer for hyperthermia

A brief expression of sound field induced by an annular transducer is derived by introducing a negative sound source, and the sound fields generated by single piezoelectric ceramic ring, annular arrays excited at the same time and phased annular arrays are calculated. The influences of various factors such as the width of the ring, the number of elements and the site of focus on the characteristics of sound fields are analyzed. It is proposed that the delayed time of the electric signal to excite individual element should be determined by the phase of the acoustic pressure generated by this element at the desired focus, with the result that better focusing effect can be obtained than determining the delayed time of the electric signal by the average sound distance from the element to the desired focus.