Printed inverted-F antennas over lossy magneto-dielectric materials: theoretical approach and validations

Closed-form formulas for radiation efficiency and bandwidth predictions, suitable for printed inverted-F antennas (PIFAs) over lossy magneto-dielectric materials, are proposed. The formulation uses the field expressions inside the cavity for the first resonant-mode (fundamental mode) based on the cavity model. It includes the substrate effective permittivity (ε_re) and permeability (μ_re) in addition to the radiation from both the shorting-pad and the slot. The derived expressions for efficiency and bandwidth are validated with measurements and full-wave CST simulations based on the finite integration technique. Various sizes and types of magneto-dielectric materials are considered. It is noticed that magneto-dielectric materials having √(ε_reμ_re) > ε_r or simply with μ_r > ε_r are advantageous for both radiation efficiency and bandwidth enhancement.