Design and Full Characterization of Planar Active Magnetic RF Metamaterials

Applications of metamaterials have been limited by parasitic resistive losses. We present the design and measurement of split ring resonators with embedded active field effect transistor circuits comprising a magnetic metamaterial. We show that the imaginary part of the effective permeability changes sign within the bandwidth of the negative differential resistance region, creating a stable gain medium. We present experimental reflection and transmission measurements showing a sign change in the permeability loss term and two applications of such a metamaterial. use as a mu-negative near field parasitic element for small magnetic antennas and as an amplifying material in free space. We show the active metamaterial can provide property enhancement compared with related passive structures in both applications, providing a path to overcoming parasitic loss in previously demonstrated metamaterial structures.