Compact Septum Waveguide Polarizer for X-band Satellite Communication Systems

A new compact structure of waveguide septum polarizer for antenna systems is developed and simulated in the paper. Suggested design is based on a waveguide of square cross-section with two-step conducting septum. The distinguished feature of developed device is the utilization of a septum with variable thickness of sections, that allowed to introduce and optimize two additional sizes. In order to provide efficient matching and polarization performance we carried out optimization of the parametrically defined structure. The device was developed for the operating satellite X-band 7.7-8.1 GHz. Obtained optimal configuration of a compact septum polarizer ensures VSWR better than 1.2 for all waveguide ports simultaneously. Optimized crosspolar isolation is higher than 27 dB. Obtained difference of phase shifts between orthogonally polarized electromagnetic waves falls within the range of $90^{\circ}\pm 5^{\circ}$ in the whole operating frequency band. Simulated ellipticity factor of developed polarization converter is less than 0.8 dB. Two rectangular waveguide ports are discriminated to each other by more than 27 dB. Therefore, developed design of waveguide septum polarization duplexer provides simultaneous benefits of compactness with good polarization purity characteristics and allows its combination with waveguide antennas and devices. Waveguide X-band septum polarization transformer can be implemented in novel dual-polarization systems for satellite telecommunications and radiolocation.