Comments, with reply, on "Formulas useful for the synthesis and optimization of general, uniform contradirectional couplers" by F. Sellberg

The commenter addresses the case of the ideal, asymmetric, inhomogeneous coupled-line coupler, which is perfectly matched and isolated at all frequencies (if dispersion can be neglected) and which was not treated in the above-titled paper (ibid., vol.38, pp.1000-1010, Aug. 1990). He refutes the authors' statement that perfect isolation for all frequencies can be achieved on in the case of homogeneous coupler. The author agrees that the statement was incorrect and amends it to say that the coupler is better described as compensated in a distributed and therefore frequency-insensitive manner. He also shows how the treatment in his paper could have stressed the general applicability of his results more.<
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