This work proposes a small pattern and polarization diversity multi-sector annular antenna with electrical size and profile of ka=1.2 and 0.018lambda, respectively. The antenna is planar and comprises annular sectors that are fed using different ports to enable digital beamforming techniques, with  efficiency and gain of up to 78\% and 4.62 dBi, respectively. The cavity mode analysis is used to describe the design concept and the antenna diversity. The proposed method can produce different polarization states (e.g. linearly and circularly polarized patterns), and pattern diversity characteristics covering the elevation plane. Owing to its small electrical size, low-profile and diversity properties, the solution shows good promise to enable advanced radio applications like wireless physical layer security in many emerging and size-constrained Internet of Things (IoT) devices.