Narrowband and Wideband Metamaterial Antennas Based on Degenerate Band Edge and Magnetic Photonic Crystals

Historically, antennas and microwave devices relied on isotropic media. This provided for limited degrees of freedom (one for dielectric and another for magnetic) in the design process. In contrast, anisotropic media introduce several more degrees of freedom (at least three more for dielectrics and three additional ones for magnetic) opening a new direction in designing radio-frequency (RF) communication devices and wireless systems. A focus of the paper is the introduction of anisotropic media parameters emulated using simple printed, but highly coupled, transmission lines (TRLs). The paper begins by introducing the equivalence between in-plane anisotropy and coupled TRLs to realize degenerate band edge (DBE) and magnetic photonic crystal (MPC) modes. This is followed by the design of miniature antenna elements via dispersion engineering, demonstrating their performance on small finite substrates. The second part of the paper is focused on concatenating DBE and MPC antenna elements to realize smaller size wideband arrays. Such arrays exploit the current sheet antenna (CSA) concept to achieve the coveted goal of small wideband metamaterial arrays. For example, by constructing an array of antenna elements ~ λ/10×λ/10 in size, highly conformal (very thin) apertures delivering 5 : 1 bandwidth are demonstrated while avoiding grating lobes. In contrast to transitional approaches, the proposed method exploits (rather than suppressing) the metallic ground plane inductance. Instead, the capacitance of the tightly coupled antenna elements is used to cancel the inductance over wide bandwidths. By further employing small size array elements, large bandwidths can be achieved using a smaller footprint.