An Idea for Electromagnetic "Feedforward-Feedbackward" Media

In this paper, an idea for a new class of complex media that we name feedforward–feedbackward (FFFB) media is presented and some of the results of our theoretical work in analyzing plane wave propagation in the axial direction through these media are described. The concept of FFFB media, as introduced here, was inspired by the theoretical research of Saadoun and Engheta on a variation of artificial chiral media. Like chiral media, to our knowledge there are no naturally occurring FFFB media for the microwave frequency band; for this reason we introduce an idea for artificial FFFB media. The focus of this paper is on one conceptualization of such media, namely dipole–dipole FFFB media. First, we present the calculation of the necessary constitutive parameters for studying axial plane wave propagation. Then we solve the macroscopic Maxwell equations in the k domain for axial plane wave propagation in an unbounded source-free crossed-dipole FFFB medium. Finally, we present the dispersion equation for this medium in this case, discuss some of the physical properties of its roots and certain features of the polarization eigenstates, and briefly speculate some of the potential applications of this medium.