Artificial composite materials consisting of nonlinearly loaded electrically small antennas: operational-amplifier-b ased circuits with applications to smart skins

Several new artificial nonlinear composite materials are introduced in this paper. They consist of electric molecules constructed with nonlinearly loaded electrically small dipole antennas. Their behaviors are studied with an augmented finitedifference time-domain (FDTD) simulator. The loads are based upon the use of multiple diodes and ideal operational amplifiers. The resulting composite materials are shown to have nonlinear electromagnetic properties including the ability to create any desired set of harmonics and subharmonics from an input wave having a single fixed frequency. Curve shaping circuits are introduced, simulated, and used to design materials that produce output signals of specified forms. Because the operating points of these curve shapers are adjustable, they could be modified in real time. The resulting smart materials could be designed in the microwave region to produce any specified response to a recognized input signal.