式中，aa，bb，cc和dd是上行波和下行波的幅值系数，可由电磁波在界

In the formula, aa, bb, cc and dd are the amplitude coefficients of upgoing waves and downgoing waves. The equation can be established based on the continuity conditions of electromagnetic waves at the interface, using the known conditions that the first layer only has downgoing waves and the bottom layer only has upgoing waves. , is obtained through the recursion relationship of each hierarchical interface [19].

In the equation, aa, bb, cc, and dd are the amplitude coefficients of the upward and downward waves. The equation can be established based on the continuity conditions of the electromagnetic wave at the interface, and the known conditions of only downward waves in the first layer and only upward waves in the lowest layer can be used to calculate the recurrence relationship of each layered interface [19].

Where aa, bb, cc and dd are the amplitude coefficients of upward wave and downward wave, the equation can be established from the continuous condition of electromagnetic wave at the interface, and it can be obtained by using the known condition that the first layer only has downward wave and the lowest layer only has upward wave through the recursive relationship of each layered interface [19].