RADIO PHYSICS AND RADIO ASTRONOMY

Purpose. Diff raction problem of the H_1n and E_1n waves of circular waveguide by the finite and semi-infinite system of similar discontinuities is considered. Four types of discontinuities are considered: iris, disk, ring, annular slot. The distance between irregularities is the same. Th e waveguide is filled by the dielectric with losses.

Design/methodology/approach. To solve the problem we chose the operator method. While so-called key problem, the diffraction problem by a single discontinuity, is solved by the method of moments. The field in the domain of the obstacle is represented as a series in terms of eigenwaves of infinite waveguide which cross section coincides with the cross section of discontinuity, with unknown amplitudes. To find the amplitudes we obtain the infinite system of equations, which is solved by the reduction. As a result, the transmission and reflection operators of a key-problem are obtained. The properties of finite sequence are determined from the operator equations relatively amplitudes of the scattered field. To write these equations the iterative procedure is used. The properties of the structure, which consists of N discontinuities are obtained under assumption that the properties of the structure, which consists of N – 1 discontinuity are known. The reflection operator of the semi-infinite system is obtained from known non-linear operator equation of the second kind.
Findings. The systems of equations for every single discontinuity are obtained. The operator equations relatively amplitudes of the scattered fields for finite system are presented. With the help of the created model the dependences of the transmission, reflection coefficients of the H11 wave as well as transformation coefficients of the H₁₁ to E₁₁ wave of the circular waveguide on the wavenumber, geometrical and material parameters for finite and semi-infinite structures are studied. The comparison of the results obtained by presented method with the results obtained in HFSS is made.
Conclusions. With the use of the operator method the scattering model of the H_1n and E_1n eigenwaves by the system of annular discontinuities of zero thickness in a circular waveguide is built. The study of the scattering characteristics on the parameters is made.
The coincidence of the behavior of the curves obtained by the presented method with those obtained in HFSS allows us to draw a conclusion about the correctness of the results. The results can be used during creation of a series of the microwaves and optic devices.

Keywords: circular waveguide, circular iris, disc, ring, slot, operator method

Manuscript submitted 15.12.2021

Radio phys. radio astron. 2022, 27(1): 005-016

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