Eight-channel directional coupler of orthogonal H21 modes in circular waveguide for X-band quasi-monopulse antenna systems

F. F. Dubrovka; S. I. Piltyay; Yu. A. Ovsyanik; R. R. Dubrovka

doi:10.3103/S0735272720120043

Authors

F. F. Dubrovka Igor Sikorsky Kyiv Polytechnic Institute, Ukraine https://orcid.org/0000-0002-3485-6822
S. I. Piltyay Igor Sikorsky Kyiv Polytechnic Institute, Ukraine https://orcid.org/0000-0002-6927-8663
Yu. A. Ovsyanik Igor Sikorsky Kyiv Polytechnic Institute, Ukraine https://orcid.org/0000-0001-8931-5612
R. R. Dubrovka Igor Sikorsky Kyiv Polytechnic Institute, Ukraine https://orcid.org/0000-0003-0051-4784

DOI:

https://doi.org/10.3103/S0735272720120043

Keywords:

directional coupler, waveguide H21-mode coupler, higher-order modes, quasi-monopulse antenna system, tracking system

Abstract

The paper presents results of the development and performance optimization of 8-channel directional coupler (DC) of orthogonal type H₂₁ modes in a circular multimode waveguide. This DC is designed for a high precision autotracking quasi-monopulse system of low-orbiting satellites for Earth remote probing. The design and testing of a prototype operating in the X-band 8–8.5 GHz were developed. The proposed simple and reliable DC design simultaneously performs an almost ideal power division of H₂₁ mode into four equal parts. We obtain the coupling ratio –6.04…–6.2 dB, good matching (VSWR < 1.12), high isolation (I > 31 dB), and directivity (D > 25 dB). Transformation ratios of the working H21 mode into other types of modes in a circular DC waveguide are less than –70 dB. A manufactured prototype of the developed 8-channel DC is tested in the extended X-band of 7.7–8.5 GHz. The measured VSWR values do not exceed 1.25 for H₁₁ modes with orthogonal circular polarizations. The measured isolation ratio of rectangular waveguide channels of tracking signal with respect to information signal in circular waveguide exceeds 32 dB.

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