Abstract: Using the eonformal transformation, the TEM wave distribution in an unscreened slab line of a plate with a cylindrical bulge is given. The field structrue of cross section is drawn to show the variation relationship and data of plate＇ field strength and the included angle α,which is between the positive direction of the x-axis and the tangent of the cylindrical cross-section at the origin. We conclude that the maximum transmission power of the transmission line decreases because of the presence of the cylindrical bulge on the plate.

Key words: unscreened slab line of a plate with a cylindrical bulge, conformal transformation, TEM wave, electromagnetic field structure, characteristic impedance