Magnetless Nonreciprocal Metamaterial (MNM) Technology: Application to Microwave Components

A magnetless nonreciprocal metamaterial (MNM), consisting of traveling-wave resonant ring particles loaded by transistor and exhibiting the gyromagnetic properties as ferrites, without their size, weight, cost, and monolithic microwave integrated circuit incompatibility drawbacks, was recently introduced in 2011 by Kodera et al. This paper presents the first extensive investigation of the applicability of MNM technology to nonreciprocal microwave components. It recalls the key principle of the MNM, provides basic MNM design guidelines, explains coupling mechanism between a microstrip line and MNM rings, and demonstrates two nonreciprocal MNM components based on a microstrip-ring configuration, an isolator, and a circulator. Although these components have not been fully optimized, they already exhibit attractive performance and provide a proof-of-concept that MNM technology has a potential for microwave nonreciprocal microwave components with substantial benefits compared to their ferrite and active-circuit counterparts.