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Updated: Mar 9, 2026
A Multimodal Wide-Field Fourier-Transform Raman Microscope
Published on: December 30, 2025
A C-band broadband ortho-mode transducer for radioastronomy polarimetry
Ivan S Ferreira1, Camilo Tello2, Miguel Bergano3
1Laboratório de Cosmologia e Astrofísica, Instituto de Física, Universidade de Brasília, Campus Universitário Darcy Ribeiro, Asa Norte, Brasília, 70919-970 Brazil.
Background:
We describe the design, the construction and performance of a narrow band ortho-mode transducer, currently used in the 5 GHz polarimetric receiver of the Galactic Emission Mapping project.
Results:
The ortho-mode transducer was designed to achieve a high degree of transmission within the 400 MHz of the GEM band around the 5 GHz (4.8-5.2 GHz). It is composed of a circular-to-square waveguide transition, a septum polarizer, a thin waveguide coupler and a smooth square-to-rectangular waveguide transition with custom waveguide bends to the output ports.
Conclusion:
Our simulations and measurements show a very low level of cross-polarization of about -60 dB and a good impedance match for all three ports (S11; S22; S33 < -30 dB) with only 0:25 dB of insertion loss offset across the 400 MHz (4.8-5.2 GHz) of the reception bandwidth.
