A metamaterial-integrated shared-aperture planar antenna with microwave electrically small property and millimeter-wave electrically large property

This paper designs a metamaterial-integrated shared-aperture planar antenna exhibiting both electrically large and small properties. Through the electromagnetic properties of the metamaterial’s anisotropic medium, the theory derives the boundary condition equations, revealing the universal conditions for achieving electrically large property (ELP) and electrically small property (ESP). Theoretical analysis shows that by adjusting the components of the equivalent permittivity and permeability to satisfy − 1 < μ_effε_eff<0 (ELP) and μ_effε_eff<−1 (ESP), respectively, and frequency band control can be achieved under fixed physical dimensions. To validate the correctness and practicality of the theory, a dual-band microstrip patch antenna element and array are designed and fabricated. The antenna element achieves dual-band resonance at 7.2 GHz and 29.7 GHz, with electrically small dimensions of 0.24λ₁×0.24λ₁×0.08λ₁ (λ₁ is the free-space wavelength at low frequency) and electrically large dimensions of 0.99λ₂×0.99λ₂×0.25λ₂ (λ₂ is the free-space wavelength at high frequency). The measured gains of the 1 × 2 antenna array is 6.6 dBi and 12.0 dBi, showing effective broadside radiation in both frequency bands.