Planar Ferrite Materials for Millimeter-Wave Applications

ABSTRACTTransferred-film technology provides a path to the integration of self-biased hexaferrite film devices into MMIC circuits. While progress is being made on the growth of thick oriented films of barium hexaferrite doped with aluminum and scandium by pulsed laser deposition or liquidphase epitaxy, we have demonstrated prototype devices using available yttrium-iron-garnet films and thinned bulk hexaferrites. Insertion losses less than 2dB and isolation greater than 20dB have been demonstrated, and theoretical modeling indicates that insertion losses less than 0.5 dB are accessible with optimized materials and through matching the active circuit components to the ferrite device. The prospects of accessing ferrite non-reciprocal, non-linear, and tunable functions at frequencies up to and exceeding 100 GHz through devices integrated onto microwave IC substrates without the use of DC biasing magnets are the driving force of this research.