Metal metamaterials: The core of electrically-fed antenna multi-performance optimization

Metamaterials, engineered materials with exceptional electromagnetic properties not found in nature, have emerged as a revolutionary technology for enhancing conventional electrically-fed antenna performance across multiple critical parameters. This paper comprehensively reviews the application of metal-based metamaterials as the core enabling technology for optimizing electrically-fed antenna characteristics. Key performance improvements demonstrated include: (i) Gain enhancement using zero-index, epsilon-near-zero (ENZ), mu-near-zero metamaterials, or metamaterial lenses/superstrates, achieving gains up to 22.4 dBi and directivity improvements; (ii) Bandwidth expansion overcoming the inherent narrow bandwidth limitations of traditional patch antennas, with techniques yielding bandwidths exceeding 64% and operational ranges covering 4−9.1 GHz; (iii) Isolation improvement in multiple input multiple output (MIMO) systems crucial for 5G/6G, utilizing metamaterial walls or decoupling structures to achieve isolation >28 dB and mutual coupling suppression exceeding 36 dB; (iv) Antenna miniaturization leveraging complementary double-negative metamaterials, capacitive loading, or slow-wave structures to achieve up to 60.7% size reduction while maintaining or enhancing performance; and (v) Radiation efficiency Improvement, particularly addressing challenges like losses in graphene plasmonic antennas using engineered ENZ metamaterial substrates. The paper details innovative designs such as Fabry−Pérot resonator antennas with chessboard metamaterial superstrates, hybrid metasurface arrays, and pattern-reconfigurable zeroth-order resonance metasurface antennas. Future prospects highlight the integration of metamaterials and electrically-fed antennas with 6G, terahertz technology, AI-driven adaptive beamforming, and conformal applications in stealth and autonomous systems, despite ongoing challenges in cost-effective manufacturing and electromagnetic control complexity. Metamaterials are conclusively positioned as a pivotal technology for next-generation high-performance, multifunctional, and miniaturized antenna systems.