Fig. 1. Schematic of TM FET.

Fig. 2. Field distribution of the FET when t = 0: (a) E_z on the y = 0 plane; (b) E_ρ on the y = 0 plane; (c) H_θ on the y = 0 plane; (d) E_z on the z = 0 plane; (e) E_ρ on the z = – q₁ plane; (f) H_θ on the z = – q₁ plane.

Fig. 3. Field distribution along z direction when t = 0: (a) on the line ρ = 0; (b) on the line (x = 4.5q₁, y = 0) of cylindrical surface ρ = 4.5q₁.

Fig. 4. Evolution of the field distribution of FET: (a) Longitudinal electric field E_z; (b) transverse electric field E_ρ, the black line indicates the position of maximum transverse electric field when the FET propagates to different positions.

Fig. 5. Position of maximum transverse electric field when the FET propagates to different positions: (a) z < q₂; (b) z > q₂.

Fig. 6. Normalized spectrum distribution when the FET propagates through the z = 0 plane: (a) Longitudinal electric field E_z; (b) transverse electric field E_ρ.

Fig. 7. Position curves of maximum value of each frequency of the transverse electric field E_ρ.