linear to circular polarization

Does anyone out there have dimensions for a linear to circular polarization converter in waveguide. I need to go from linear to RHCP on one unit, and LHCP to linear on the other unit. I remember seeing a simple metal plate attached to a wall in a circular waveguide that would retard one component of the electric field to do this, but have been searching around and can not find any good papers showing the structure. Don't remember if the metal plate is λ/4, or λ/2 long or what. 5.8 GHz, but I can scale from other frequencies.

Thanks, Rich.

http://www.ve1alq.com/W2IMU-K1RQG/Te...%20of%2020.pdf

Thanks. That is exactly what I needed!