Abstract: A transition device achieves transformation of the signal carrier mode of a continuous wave guide, into the hybrid mode, the corresponding mode for carrying signals in corrugated structures, by employing a tapered waveguide transition of circular cross-section having dual-depth circumferential slots in the interior boundary surface thereof. The transition device utilizes a mutual resonance property of the slots at the port which connects to a continuous waveguide to achieve satisfactory operation in two frequency bands. At the port which is connected to a corrugated horn, the quarter wavelength self resonance of the individual slots provides the desired hybrid mode under balanced hybrid condition in these two bands. A gradual transition of the electrical characteristics is achieved along the length of the transition device through an adjustment of slot dimensions.