An approximate variational solution to the step discontinuity in finline

The variational method is applied to a step discontinuity in unilateral finline on the basis of a simplified description of the finite modes, as modes of a symmetrical finned waveguide. A prudent choice of the trial field in the electric and the magnetic formulations allows the derivation of economical simple equivalent circuits with frequency-independent elements over a full waveguide band for a broad range of practical step ratios.<
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