A.N. Yakimov1, A.R. Bestugin2, I.A. Kirshina3

1-3 Saint-Petersburg State University of Aerospace Instrumentation (Saint-Petersburg, Russia)

By the method of mathematical modeling, the problem of researching the influence of the electromagnetic interaction of the horn irradiator of a parabolic antenna with its reflector (mirror) on the characteristics of this irradiator is solved. It is shown that to assess the effect of the mirror on the characteristics of the irradiator of a parabolic antenna, it is advisable to describe the matching of the horn with the free space using its «waveguide equivalent scheme». This allows us to imagine the shape of the horn irradiator and the mechanism of its radiation in the form of a transmission line consisting of three equivalent transmission lines: replacing the supply waveguide; replacing the horn between the neck and the aperture; replacing the radiation space between the aperture of the horn and the reflector. In the first approximation, the reflection from the horn aperture is considered as a reflection from the open end of a rectangular waveguide with the size of the horn aperture, while the propagation of electromagnetic waves in the horn radiator is considered taking into account the influence of the reaction of the reflecting mirror in accordance with its «waveguide equivalent scheme». When constructing a mathematical model, the following assumptions are made: the transition elements between the equivalent circuit lines are free from losses and are reversible (the reciprocity principle is valid); the requirement of constancy of the tangential components of the field at the junction is fulfilled, while the waves in the line are expressed in terms of the coordinates of the horn to fulfill the continuity conditions, and the corresponding components are equated; the fields on both sides of the junction between the power line and the mouth of the horn behave as fields of the only main type of wave in the line; subsequent multiple reflections of the wave are excluded from consideration. The obtained formulas allow us to calculate the reflection coefficient of the horn irradiator, taking into account its geometric dimensions, the length of the electromagnetic wave used and the spatial position of the horn relative to the surface from the reflecting mirror. The presented results of the model study show that the change in the reflection coefficient of the horn, depending on the distance of its aperture to the reflecting mirror, is periodic, which must be taken into account when designing. The proposed approach to modeling the influence of the mirror on the characteristics of the irradiator allows us to reduce a complex electrodynamic problem to a geometric one in many respects and to estimate the field returning to the irradiator and changing the conditions for its matching. Given that the mirror affects the characteristics of both the irradiator and the entire antenna, it becomes possible to optimize its design in order to minimize this influence. The obtained results can be recommended for further practical use in the design of mirror parabolic antennas.

Yakimov A.N., Bestugin A.R., Kirshina I.A. Modeling of electromagnetic interaction of irradiator and reflector in a mirror antenna. Electromagnetic waves and electronic systems. 2021. V. 26. № 5. P. 23−29. DOI: https://doi.org/10.18127/j15604128-202105-03 (in Russian)

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