On the Bandwidth of a Microparticle-Based Component Responsive to Magnetostatic Fields

A novel magnetostatic responsive structure (MRS) that does not require a direct connection to biasing circuitry for microwave applications is presented. This allows the placement of the MRSs in locations that may not be accessible with traditional printed traces. The MRS measures 3.0 mm × 3.0 mm × 0.508 mm in the x-, y-, and z-directions, respectively, with a 0.9 mm diameter cylindrical cavity. The axis of this cavity is along the z-axis and is partially filled with microparticles (diameter ~10-40 μm) composed of a magnetite core with a silver coating. A copper foil is placed on the top and bottom to enclose the particles in the cavity. When a static magnetic field is introduced, the magnetic particles stack and align in columns in the direction of the field lines, connecting the foil layers. Conversely, when the magnetic field is removed, the columns collapse and disconnect the layers. A microstrip transmission line is used to extract the equivalent circuit of the MRS, and compare to full-wave simulations and measurements for both states. Agreement was shown up to 3.0 GHz. Finally, the MRS was embedded into a host material to explore the bandwidth, signal integrity, benefits of remote biasing, and the field-strength/scalability relationship.