利用二维有限差分法对单脊波导TM模进行计算。通过调整网格数目观察计算结果的精度，可以设定出最优的网格数目，然后改变波导中脊的尺寸，观察最低两个TM模对应的截止频率的变化规律，最后给出对应的横截面电场、磁场分布图-The two-dimensional finite difference method to calculate the single-ridge waveguide TM mode. The optimal number of grid can be set by the accuracy of the adjustment of the calculation result of the grid number observed, and then change the size of the waveguide ridge observed the lowest two corresponding to the TM mode of the cutoff frequency of the variation, and finally to give the corresponding cross cross-section of the electric field, magnetic field maps