BROAD BAND MODE CONVERTER

PURPOSE:To attain ease of manufacture with high quality and to obtain an excellent frequency characteristic in the operation at an octave band by using a ridge waveguide for a rectangular waveguide used for the conversion from a circular mode into a rectangular mode in converting a TE01 mode into a TE11 mode. CONSTITUTION:A rectangular TE10 mode converter converting a TE01 mode circular waveguide 31 into a TE10 mode rectangular waveguide has an excellent characteristic also with a broad band width, and in order to bring the characteristic into a further broader band, a ridge waveguide is applied to the TE10 mode converter, and as an example of the application, a ridge waveguide 32 having a ridge 33 is used. In an example of the execution of this invention, the construction is adopted, where a taper waveguide 34 at the inside of which a conductor 35 whose cross section is changed in taper is provided between the circular waveguide 31 and the ridge waveguide 32. When a millimeter wave of the TE01 mode is transmitted to the TE01 mode waveguide 31, the millimeter wave is changed gradually as the wave passes through the taper waveguide 34 and the ridge waveguide 32 and outputted as the TE10 mode from the waveguide 32.