Transmission characteristics of a left-handed (LH) ferrite microstrip line are significantly affected by the nonuniform DC bias magnetic field in the ferrite substrate (internal magnetic field Hin) caused by the inhomogeneous demagnetizing effect because the strip conductors of these devices must be mounted at the edge of the ferrite substrate. Three dimensional analyses on the LH ferrite microstrip line are performed taking into account the nonuniform internal magnetic field Hin. The analytical results show that the nonuniform internal magnetic field under the strip conductor near the edge of the ferrite substrate is useful for spreading the frequency band of negative permeability and nonreciprocal operation, and for improvement of both the insertion and return losses of the LH ferrite microstrip line. Measured results of more than 20 dB isolation with 2.2 dB insertion loss and 1.33 GHz bandwidth are corresponding well to the analytical results.

This paper treats transmission characteristics of periodic structure of ferrite gyrator circuit with both theory and experiment, which is loaded into usual distributed constant line with and without lumped capacitor. Following three types of periodic structure of gyrator circuit are proposed: basic structure of periodic gyrator circuit, quasi-LH gyrator circuit with series capacitance loading, and quasi-LH gyrator circuit with parallel capacitance loading. Moreover, replacing the parallel capacitance with a resistance, a periodic structure of isolator circuit is proposed. Scattering parameters of gyrator circuit are derived with help of equivalent circuit model. Left handed transmission behavior of backward wave is discussed from dispersion curves. Experiments were undertaken using periodic structure of dielectric microstrip line and gyrator circuit fabricated on the ferrite substrate. Experimental results having wide band nonreciprocal characteristics are discussed with theory.

A nonreciprocal left-handed transmission line is proposed and investigated, which is composed of a normally magnetized ferrite microstrip line periodically loaded with inductive stubs but without capacitive loading. The circuit configuration becomes simpler than that of a nonreciprocal left-handed transmission line with both shunt inductive and series capacitive loadings. In the proposed structure, ferrite medium is employed as the substrate not only for the nonreciprocal characteristics but also for negative effective permeability that is essential to establish the left-handedness. After calculations of dispersion curves using equivalent circuit model, scattering parameters along with field patterns are estimated numerically with the help of electromagnetic simulation, and the experiments are also carried out. It is found that the band width of the proposed left-handed transmission line is relatively narrow but the structure still has the high isolation ratio of more than 30 dB.