Metamaterial-Based Low-Profile Broadband Mushroom Antenna

A metamaterial-based broadband low-profile mushroom antenna is presented. The proposed antenna is formed using an array of mushroom cells and a ground plane, and fed by a microstrip line through a slot cut onto the ground plane. With the feeding slot right underneath the center gap between the mushroom cells, the dual resonance modes are excited simultaneously for the radiation at boresight. A transmission-line model integrated with the dispersion relation of a composite right/left-handed mushroom structure is applied to analyze the modes. The proposed dielectric-filled (ε_r=3.38) mushroom antenna with a low profile of 0.06λ₀ ( λ₀ is the operating wavelength in free space) and a ground plane of 1.10λ₀×1.10λ₀ attains 25% measured bandwidth with(|S₁₁| <; - 10dB) 9.9-dBi average gain at 5-GHz band. Across the bandwidth, the antenna efficiency is greater than 76%, and cross-polarization levels are less than -20 dB.