G. F. Zargano, V. V. Zemlyakov, R. V. Peletskiy
Waveguides of complex cross-section, for example single- and double ridge waveguides, could be used for directional coupler design because of better directivity, broadband and dimensions characteristics. One of the most popular types of directional couplers is couplers with the system of small coupling apertures, which are usually analyzed by the Bethe’s quasi-static theory.
The problem of analysis and synthesis of directional couplers on single- and double-ridged waveguides coupled with the system of small crossline apertures is solved. Electromagnetic fields and cutoff wave numbers are calculated by method of partial regions including field singularities at the edge. For multielement directional couplers the theory of multipole concatenation is used.
The broadband directional couplers with coupling loss 20 dB are calculated; the dependencies of directivity and coupling loss from normalized wave number are shown. The comparison of calculation results with the results of computer simulation by numerical techniques confirms the efficiency of developed algorithms.