The development of future telecommunication systems requires the miniaturization of circulators. Apart from using planar technologies, removing magnets appears as one of the main solutions to improve the integration of circulators. This technological step requires the use of oriented hexaferrites in their remanent state. Thus, the unusual properties of these materials were used to design and realize a millimeter-wave self-biased circulator in rectangular waveguide. Without magnets, insertion losses of 1.79 dB and an isolation level of 28.1 dB were measured at 41.4 GHz. These results demonstrate the strong potential of these materials for the design of self-biased circulators.

The TLM (Transmission Line Matrix) method, in time domain, is extended to account for the presence of dispersive and anisotropic media in electromagnetic structures or devices. The model is thoroughly constructed by using Maxwell's equations that make it a unified general TLM formulation. Preliminary results are compared with a commercial simulator in the case of dielectric dispersive and anisotropic media and saturated ferrites, hence, validating the model. The objective is to insert a generalized permeability tensor model in the new TLM algorithm to allow the simulation of ferrite-based microwave structures such as non-reciprocal devices: circulators, isolators, phase-shifters, etc.

A generalized TLM modeling method has been developed and applied for the design of patch antennas which substrate is a saturated ferrite. The model is rigorously constructed by using Maxwell’s equations that make it a unified general TLM formulation. The permeability tensor of the saturated ferrite is derived from the Polder formulations. Results, compared with a commercial simulator, give good agreement for the studied structures. Our aim is to insert a new permeability tensor model for non-saturated ferrite materials in the TLM algorithm to allow the simulation of microwave structures integrating ferrites whatever their magnetization state. Index Terms — TLM, dispersive and anisotropic media, ferrite, microstrip, patch antenna, permeability tensor.

The TLM (Transmission Line Matrix) method, in time domain, is extended to account for the presence of dispersive and anisotropic media in electromagnetic structures or devices. The model is thoroughly constructed by using Maxwell's equations that make it a unified general TLM formulation. The theoretical derivation was revisited, starting with Maxwell's equations, without invoking circuit analogy. The procedure is general and can be applied to derive the algorithm for new extended TLM nodes. The case of anisotropic ferrite-based structures is studied.