Technical memorandum. Nonreciprocal coupling in dielectric image lines

Preliminary experimental results are presented on novel nonreciprocal coupling between two identical dielectric image lines. This is produced by loading the coupling region with a longitudinally magnetised ferrite. Measurements in the frequency range 26.5¿¿40 GHz show a differential insertion loss of greater than 15 dB, over a bandwidth of approximately 1.5 GHz between 30 GHz and 35 GHz, produced by reversing the bias field. The minimum insertion loss was approximately 5 dB over this bandwidth, and the return loss was better than 13 dB. These results can be improved and this effect can be used to develop four-port circulators for millimetric wavelengths.