ORTHOMODE TRANSDUCER (OMT)

Model

The geometry of the Orthomode Transducer (OMT) shown in the first figure is selected to illustrate the capabilities of the SEMCAD X Mode-Matching solver for multi-port and multi-mode configurations. The square waveguide constitutes the common port, where fields with perpendicular polarization coexist at the working frequency (degenerated modes). Each polarization is separated into the fundamental modes of the vertical and horizontal ports. The structure has been designed as a Ku-band OMT for dual-polarization communication systems to fulfill different requirements for vertical and horizontal polarizations [Ref]. A double septum allows a shorter device as well as a better matching for the horizontal polarization.

Simulation

The structure was simulated using the SEMCAD X Mode-Matching solver to obtain return loss response and E-field distributions at different frequencies.

Results

The matching of both the vertical and horizontal ports are presented in the figures showing good agreement between the computed and measured results. Furthermore, the E-field distribution at different cross-sections of the structure is also computed at different frequencies as shown in the last figures.

Ref. J.A. Ruiz-Cruz, J. Montejo-Garai, J. Rebollar, C. Montesano, and M. Martın, “Very compact ortho-mode transducers with double septum configuration” Microwave and Optical Technology Letters, John Wiley and Sons Ltd., 2006, 48, 765-767.