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.

The realization and performance is demonstrated of a conformal bow-tie antenna printed on a multi-scale triangular element mushroom structure high-impedance ground-plane (HIGP). The two-scale HIGP was designed to exhibit a large frequency band-gap to cover the relatively broad operational frequency bandwidth of the bow-tie antenna. HIGP elements were chosen to be triangular to form a natural commensurate blending of the bow-tie into the structure. The experimental performance is characterized of the bow-tie-HIGP combination from 2-10 GHz, and it is demonstrated that the negative effects of a perfect electric conductor ground-plane may be mitigated by using a HIGP.

Two low-profile bow-tie antenna designs are presented, printed conformally on high-impedance ground planes (HIGPs). The HIGPs were constructed using two different scale triangular patch mushroom elements which allow for a suitable platform for the active bow-tie antenna. The multiscale nature of the HIGP was utilized to further increase the frequency band-gap of the surface waves, and to enhance the properties of the low-profile bow-tie. The bandwidth of the bow-tie on the HIGP is evaluated and compared with perfect-electric-conductor (PEC) and perfect-magnetic-conductor (PMC) ground planes.