Broadband characterization of bulk and thin magnetic composites using stripline structures

We present two broadband characterization techniques to extract the RF (50 MHz4.5 GHz) permeability of bulk and thin magnetic composite materials. Both techniques are based on broadband stripline structures with the permeability determined from S-parameter measurements. For bulk samples, a tapered stripline fixture, supporting transverse electromagnetic (TEM) waves, is employed. As this approach is not suitable for thin material samples (thickness t< 1 mm, a microstrip line fixture is proposed along with a new permeability de-embedding technique. Compared with conventional microstrip line methods, this approach is found to be accurate for thin samples with small surface areas (less than 1 cm × 1 cm). The validity of the techniques is demonstrated by measuring a bulk ferrite slab and a thin patterned ferrite composite with in-plane anisotropy.