采用口径场法对聚焦条件下具有高斯波束的矩形口径天线近场进行了分析，得到了聚焦条件下的近场场强分布与近场增益解析式，并对不同的聚焦位置进行了仿真。结果表明：在近场区，聚焦位置离轴向越近，其场强越强，且增益越大,聚焦位置沿轴向时其场强与增益皆为最大；反之，聚焦位置离轴向越远，其近场场强与近场增益越小。因此，通过聚焦可以显著提高天线口径面场的近场场强与增益指标，从而提高天线系统的有效作用距离。

The paper discusses the near field of rectangular aperture antenna under focusing of Gaussian beam by using aperture field method, and obtains the analytic expressions of the near field intensity and gain. Corresponding simulations are conducted under different focusing conditions. The results show that in near field, the nearer the focusing position is from the axis, the bigger the field intensity and gain are, and the field intensity and gain reach their maxima when the focusing position is on the axis. Therefore, the effective range of antenna can be improved by focusing due to its ability to enhance near field intensity and gain of antenna aperture.