| 摘要 |
<p>A structure (40) with switchable magnetic properties comprises: an array of capacitive elements (44) in which each capacitive element (44) includes a low resistance conducting path and is such that a magnetic component (H) of electromagnetic radiation (12) lying within a predetermined frequency band induces an electrical current (j) to flow around said path and through said associated element (44). The size of the elements (44) and their spacing (a) apart are selected such as to provide a predetermined permeability (ν) in response to said received electromagnetic radiation (12). Each capacitive element (44) comprises a plurality of stacked planar sections (42) each of which comprises at least two concentric spiral conducting members or tracks (46, 48) which are electrically insulated from each other. A switchable permittivity material, such as Barium Strontium Titanate (BST) is provided between the tracks. The magnetic properties of the structure are switched by applying a dc electrical potential between the conducting tracks.</p> |
