Suppression of mode coupling in conductor-backed asymmetric coplanar strips using slow-wave electrodes

Shorted-ground conductor-backed asymmetric coplanar strips support unwanted noncoplanar modes that adversely affect the performance of such transmission lines at higher frequencies. It is shown that coupling from the desired coplanar mode into the noncoplanar modes can be suppressed using slow-wave electrodes. This suppression scheme is verified by measuring the S-parameters of both conventional and slow-wave transmission lines of this type in the 0.05-50 GHz range.