A folded, cavity-backed crossed-slot antenna is proposed for antenna miniaturization. The cavity dimensions of a conventional cavity-backed crossed-slot antenna are about a half-guided-wavelength along each side, which is unsuitable in many applications like a handheld device or body area network(BAN). To reduce the size of the cavity, a folded cavity is proposed in this letter.
The center plate that divides the cavity into the upper cavity and the lower cavity increases the effective length inside the cavity. Compared to the conventional cavity-backed crossed-slot antenna, a 72.8% size reduction can be achieved using the proposed structure. The proposed antenna also has circular polarization and wideband characteristics, which are the main advantages of a cavity-backed crossed-slot antenna. The proposed technique is especially useful for reducing the lateral dimensions of the cavity.