A feed network may include a cylindrical common waveguide terminating in a common port and an orthomode transducer having a first port for coupling a first linearly polarized mode to the cylindrical common waveguide and a second port for coupling a second linearly polarized mode to the cylindrical common waveguide, the second linearly polarized mode orthogonal to the first linearly polarized mode. A filter-polarizer element may be disposed within the cylindrical common waveguide. The filter-polarizer element may be rotatable about an axis of the cylindrical common waveguide. The filter-polarizer element may be configured to cause a predetermined relative phase shift between a first signal and a second signal propagating in the cylindrical common waveguide. The filter-polarizer element may be further configured to suppress propagation of at least one undesired mode in the cylindrical common waveguide.