Low-Profile Electrically Small Antenna with Pattern and Polarization Diversity

A low-profile Electrically Small Antenna (ESA) capable of pattern and polarization diversity is presented in this paper. The cavity model analysis is used to describe the antenna design concept, where a step-by-step surface current distribution-based approach is applied to discuss the antenna diversity characteristics. Rectangular and V-like shaped slits are used for isolation enhancement and antenna miniaturization, respectively. It is demonstrated that the antenna can generate multiple patterns to enable good coverage across the elevation plane, with linear and circular polarization. Moreover, an omni-directional pattern is produced with horizontal polarization. The design is planar and operates at 3.75 GHz, with $0.35\lambda$ diameter and $0.016\lambda$ profile. The -10 dB impedance bandwidth covers 20 MHz, and the peak realized gain is 2.94 dBi.