Creating and sharing knowledge for telecommunications

A C-band broadband ortho-mode transducer for radioastronomy polarimetry

Ferreira, I. S. V. ; Tello, C. T. ; Bergano , MB ; Villela, T. V. ; Barbosa , D. ; Smoot, G. F. S.

SpringerPlus Vol. 5, Nº 2069, pp. 1 - 6, November, 2016.

ISSN (print): 2193-1801
ISSN (online): 2193-1801

Journal Impact Factor: 0,982 (in 2016)

Digital Object Identifier: 10.1186/s40064-016-3761-5

Download Full text PDF ( 1 MB)

Abstract
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.