Characteristics of Oversize Circular Waveguides and Transitions at 3-mm Wavelengths (Correspondence)

The physical and electrical characteristics of a 0.995-in-diameter oversize circular waveguide and its associated transitions operating in the 92- to 96-GHz band are described. Both linear and nonlinear taper transitions were employed in converting from the WR-10 dominant-mode rectangular waveguide (0.100 by 0.050 in ID) to a 0.995-in-diameter circular waveguide. The results of the present investigations indicate that the nonlinear taper transitions yield considerably less multimoding effects. The measured attenuation for a 0.995-in-diameter oversize copper circular waveguide is 0.028 dB/ft as compared to a theoretical value of 0.02 dB/ft.