A Nonreciprocal, TEM-Mode Structure for Wide-Band Gyrator and Isolator Applications

The theoretical and experimental operation of a novel form of TEM transmission-line network capable of operation over octave bandwidths is described. This network consists, basically, of a parallel arrangement of two conductors and a ferrite rod within a grounded outer shield. The conductors maybe connected in a two-port configuration which provides, in the absence of the ferrite rod, complete isolation from zero frequency to the cut-off frequency of the first higher mode. With an unmagnetized ferrite rod properly inserted, the broad-band isolation is virtually unaffected. When the rod is magnetized by an axial magnetic field, coupling occurs between the two ports by a process analogous to Faraday rotation. The device may be used as a broad-band gyrator, switch, or modulator, and with the addition of a resistance load, as an isolator. The bandwidth of these components is inherently limited only by the bandwidth capability of the ferrite material itself.