circular to rectangular waveguide transitions

Hi,

do you know, what the best design for circular-to-rectangular waveguide transition? - circular diameter: 18 mm, rectangular: R120 - 19.05x9.525 - 10.7 - 11.7 GHz. I can do transition with S11 < -20 dB, but I need about -30 dB

Can you help me ?

Thank

Hi mauloftin, I have done some circular to rectangular waveguide transitions. The usual way to go about it is to make some intermediate sections that have the shape of a hexangon. Usually three sections should do the trick, maybe even two. Then vary the lengths of each section and the length of the hexagon sides. Don't use a symmetric hexagon because this will limit the degrees of freedom you have to vary your design. Basically just take a cube and miter the edges, then vary the lengths of the miter and sides of the cube(or rectangle).

good luck

Thanks, I will try it.