Compact Circular Slot Antenna Array Devoted to Direction Finding

We present a circular array of diversely polarized slot elements devoted to a portable direction-finding system in the UHF 868 MHz band. The detailed structure is presented as a combination of two printed circuits boards (PCBs) (FR4 substrate) holding the radiating slots and strip feeds located inside a metallic box housing. Experimental validations in terms of scattering parameters and embedded element patterns are presented. A numerical experiment is performed regarding DoA estimation, while including all the effects of mutual coupling. The performance of the proposed array is compared with that of a patch array. Good resolution is observed despite the small size of the array.