Artemiy D. Drize¹, Konstantin N. Klimov²

1, 2 Moscow Aviation Institute (National Research University) (Moscow, Russia) 

This article presents the results of numerical electromagnetic simulation of elements of an antenna-feed waveguide microwave path: a broadband orthomode transducer (OMT), an OMT, designed only for uplink frequencies, and a divider (a combiner). The feed is supposed to be used with a dish antenna as a satellite communications ground station operating in the downlink band of 11.7–12.75 GHz and in the uplink band of 17.3–18.4 GHz at circular polarization. As part of the design process, a topological synthesis of the geometry of the devices has been carried out. The broadband OMT is made on the basis of a square waveguide with four outputs tuned only to the downlink frequencies and matched by resonant irises, and a separate output in the form of a square waveguide of a smaller cross section to ensure the evanescence of low frequencies and their attenuation. The OMT, configured only for use at high frequencies, is made in the form of a transition from a square to a rectangular section with a pyramidal side output. The divider (combiner) is a tee in the E-plane. Numerical electromagnetic simulation has been carried out in the CST Studio Suite program, and the results have been checked in ANSYS HFSS with a Delta S convergence parameter of 0.01. As a result of the simulation, the frequency characteristics of the feed elements have been obtained. The 6-port OMT provides a polarization isolation of 20 dB at the uplink frequencies and more than 50 dB at the downlink frequencies. The level of VSWR does not exceed 1.25. The OMT has been developed to use both polarizations of high frequencies. The polarization isolation of this OMT is above 60 dB, its VSWR is below 1.3. Using these elements makes it possible to build a microwave feed without using a frequency diplexer. The divider (combiner) has an VSWR value below 1.06 in both bands and can be used in both versions of the microwave path construction.

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