Quasi-static and the frequency-dependent hybrid-mode analyses are presented for the general structure of coupled cylindrical striplines. Stationary expressions are derived for all elements of capacitance and inductance matrices which describe the quasi-static characteristics of the dominant C- and <0;-modes of asymmetric coupled cylindrical striplines. The hybrid-mode analysis is also developed to afford the frequency dependency of the phase constants as well as characteristic impedances. The characteristic impedances of asymmetric coupled striplines are evaluated first by using the appropriate definition based on the variational scheme. A very accurate numerical method is presented in incorporating the tight coupling between strip conductors and the edge singularities of the fields near the conductor edge properly. The frequency-dependent characteristics ensure consistency with the corresponding quasi-static solutions in lower frequencies, and the numerical results reveal the notable characteristics of the asymmetric coupled cylindrical striplines for the tight-coupling as well as the extremely weak-coupling cases.
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