Machined waveguide twist

A solution to the problem of obtaining a 90° twist in a machined-aluminium block waveguide is presented. At the waveguide input, half the waveguide wide-dimension is machined into one aluminum block the mirror image being machined into a second block. The technique involves gradually reducing the width of the input waveguide in one block, and simultaneously increasing the depth of the waveguide in the opposite block until the output waveguide depth is equal to the input waveguide width. Care must be taken to maintain a constant waveguide cutoff frequency through the length of the twisted section so that a good match is obtained. Two twists made using this technique in WR-22 waveguide are shown to give satisfactory results