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计算一定孔径的辐射声场，通常是根据惠更斯原理。应用菲涅耳近似或夫琅和弗近似可以简化计算。但是，大多数医用超声成象设备的检测区不能满足这些近似条件。本文以角谱法为主进行计算。这种方法物理意义明确，一般不必作任何近似就能进行数值计算，又便于采用ＦＦＴ算法，从而大大节约了计算工作量。文中结合计算实例对采样间隔、采样点数的选取进行了讨论。计算结果为研究线阵横向分辨力及拟定分段动态聚焦方案提供了依据。
Calculating a certain aperture radiation field, usually based on the Huygens principle. Using Fresnel approximation or Fraunhofer approximation simplifies the calculation. However, the detection area of most medical ultrasound imaging devices can not satisfy these approximate conditions. This article is based on the angle spectrum method to calculate. The physical meaning of this method is clear, generally do not need to make any approximation to the numerical calculation, but also easy to use FFT algorithm, which greatly saves the computational workload. In this paper, the sampling interval and the selection of sampling points are discussed with the calculation examples. The results provide the basis for the study of horizontal resolution of linear array and the development of sub-dynamic focusing scheme.