A general model for junction circulators; choice of magnetization and bias field

The properties of nonreciprocal ferrite devices depend strongly on the ferrite properties. The dependence of several device specifications, such as insertion loss, power capability, etc., on, for instance, linewidth, dielectric loss tangent, critical field, etc., is similar for the three different groups of nonreciprocal devices. The dependence of bandwidth and insertion loss on ferrite magnetization and polarization field is specific for a special group. To investigate the latter dependence for junction circulators, a general model for that group of devices is introduced and discussed. Junction circulators consist of a number of identical resonators. These resonators, mutually coupled by means of the ferrite, are connected to the ports. The lumped element circulator is discussed qualitatively and the stripline circulator quantitatively. For the latter, ranges of magnetization and bias field are determined for operation both above and below resonance. Obtainable bandwidths are estimated.