Epsilon-Near-Zero-inspired Antennas: Fundamentals, Design Approaches, Applications and Opportunities

Antennas are fundamental components in wireless communication systems, enabling the transfer of signals between the transmitter and receiver. Cutting-edge wireless technologies (e.g., IoT and fifth-and sixth-generation (5/6G) mobile networks) enable various applications with different antenna requirements. Antennas are engineered based on physics research, with performance influenced by the material’s constitutive parameters: permittivity (ε) and permeability (μ). Epsilon-near-zero (ENZ) materials (ε≈0) have garnered significant interest in antenna design for their ability to decouple spatial and temporal field variations. This property leads to diverging phase velocities, wavelength expansion, low wavenumber propagation, and enhanced electric fields. ENZ media can be realized through metamaterials and rectangular waveguide dispersion, enhancing antenna performance and enabling novel designs. ENZ-based metamaterials improve antenna gain, size, isolation, bandwidth, and radiation patterns. These benefits arise from the interactions of electromagnetic wavefronts with ENZ media. On the other hand, ENZ-based rectangular waveguide radiators exhibit plasmonic behavior below their fundamental mode’s cutoff frequency due to waveguide dispersion, enabling the design of geometry-independent 1D and 2D antennas and lenses. This review examines ENZ materials in antenna design, synthesizing current research, highlighting recent advancements, and evaluating the benefits and challenges of implementing ENZ-inspired antennas.