Modeling and Experimental Verification of Time-Varying Ferrite-Based Microstrip Line

We analytically investigate a model and experimentally confirm a ferrite based microstrip line subjected to a time modulated magnetic bias field. When the ferrite substrate, saturated by a permanent magnet created DC bias field, is exposed to an additional continuous wave magnetic field at angular frequency Ω, the temporal modulation produces sideband spectral components to a propagating microwave signal at ω₀ + nΩ, where n is an integer. An adiabatically generalized transmission coefficient model is presented, taking into account the intrinsic ferrite stopband, resulting in frequency dependent insertion loss and relative attenuation of sideband amplitudes. The model is experimentally verified with excellent agreement. Sideband levels up to -34 dBc are observed despite a modulation field about 330 times weaker than the DC bias. These results enable ferrite based frequency converters, harmonic generators, and nonreciprocal devices.