A Frequency Reconfigurable Magnetic Dipole Based Electrically Small Quasi-Isotropic Antenna

This work presents a novel frequency reconfigurable electrically small antenna (ESA) with a quasi-isotropic radiation pattern for ISM band applications within the 2.4 GHz band. The key contribution of this work is that a split ring resonator (SRR) is used parasitically with the electric dipole to realize a magnetic dipole-type radiation pattern. In addition, the proposed configuration is further configured with two p-i-n diodes to facilitate frequency reconfigurability to the antenna within the 2.4 GHz band. The SRR is arranged orthogonally with an electric curved dipole to achieve a uniform or quasi-isotropic radiation pattern in 3D spatial coverage. The overall size of the fabricated prototype is $0.13 \lambda \times 0.13 \lambda \mathrm{~mm}^{2}$; here, λ is the free space wavelength that corresponds to operating frequencies. The proposed antenna offers 40MHz bandwidth centered at 2.44GHz when the diodes (D1 & D2) are ON and a 30MHz bandwidth centered at 2.47GHz when the diodes (D1 & D2) are OFF. In both states, the antenna exhibits a quasi-isotropic radiation pattern with over 60% efficiency.