A Dual-Loop Antenna in a Cage Structure for Horizontally Polarized Omnidirectional Pattern

In this letter, we have presented a horizontally polarized antenna with a cage-like structure for omnidirectional coverage in the azimuthal plane, which can be used in the occasion that it is close to the metal box. The proposed antenna consists of dual crossed loops and a 90° hybrid coupler feeding. The dual crossed loops are arranged in a cage structure, which shows the merits of simple construction and easy fabrication with compact volume. The overall volume of the proposed antenna is only 52 × 19 × 19 mm³, with a gain variation less than 1.1 dB in the azimuthal plane. The size of the cross section is small. A prototype of the proposed antenna is built at 2.4-GHz wireless local area network (WLAN) band. The measured results show that the 10-dB reflection coefficient bandwidths cover the desired WLAN band of 2.4-2.48 GHz, with a constant gain better than 2.7 dBi.