Towards the Integration of Barium Ferrite Sputtered Films for Coplanar Isolators and Circulators in the Millimeter Wave
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0969-W06-06
Towards the Integration of Barium Ferrite Sputtered Films for Coplanar Isolators and Circulators in the Millimeter Wave Range A.-S. Dehlinger1,2, M. Le Berre1, J.-P. Chatelon3, E. Benevent3, D. Vincent3, D. Givord4, V. Larrey2, and J..J. Rousseau3 1 LPM, INSA Lyon, 20 Avenue Einstein, Batiment Blaise Pascal, Villeurbanne, 69621, France 2 Radiall, 81 Boulevard Denfert Rochereau, Voiron, 38509, France 3 DIOM, UJM, 23 rue du Dr. Michelon, Saint-Etienne, 42023, France 4 LLN, 25 Avenue des martyrs, BP 166, Grenoble, 38042, France
ABSTRACT Signal processing in communication, instrumentation and radar detection requires low-cost microwave and millimeter wave devices. The integration of millimeter wave passive components like isolators and circulators is thus a major issue. In these components, the nonreciprocal nature of wave propagation in ferrites plays an essential role. Hexagonal ferrites, such as barium ferrite (BaFe12O19 or BaM), which has a large resistivity and high permeability at high frequency, are of great interest for such applications. The present work deals with the characterization of barium hexaferrite sputtered films and with the device integration for the development of coplanar isolators and circulators working at frequencies above 40 GHz. The BaM films (in the thickness range of 10µm) were deposited on alumina substrate by RF magnetron sputtering at room temperature and were then crystallized using a 800°C thermal annealing. Structural properties were evaluated by X-ray diffraction and the magnetostatic properties of the film were determined using a Vibrating Sample Magnetometer (VSM) leading to assess a range of deposition conditions appropriate for device integration. Both coplanar isolators and circulators were implemented using standard lift-off technique. Coplanar circulators were designed by analytical calculation and 3D electromagnetic simulation (HFSS) supposing a saturated material and no losses. The microwave range characterization was performed using a network analyzer and a probing system with a prior OSTL calibration. The coplanar isolators were characterized both at the remanence and under a polarizing field. At the remanence, the gyroresonance occurred at 50 GHz and the nonreciprocal effect - difference between the transmission coefficient in the forward direction and in the reverse direction - was evaluated. When applying a polarizing field, the tunability of the isolator was verified experimentally. Finally first measurements on integrated coplanar circulators are currently under progress. INTRODUCTION Hexagonal ferrites are playing an important role in microwave and millimeter wave applications. Because of their strong internal anisotropy field (HA), microwave and millimeter wave devices that use hexagonal ferrites will require minimum external magnetic biasing fields compared to devices based on spinel or garnet ferrites. Another advantage of the hexaferrites is the tunability of their magnetic properties by substituting the Fe cations. Among microwave magnetic devices
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