Slim dual‐polarised antenna with omnidirectional patterns for WLAN applications

Abstract

A slim dual-polarised antenna with omnidirectional patterns is proposed for wireless local area network (WLAN) applications. The antenna is a composition of a modified J-type antenna for vertical polarisation and two crossed-loop antennas for horizontal polarisation. For improving the isolation between the two polarisations, a rectangular loop is partially added in the middle of one of the loop antenna, connecting the end of the J-type antenna. The rectangular loop also acts as tuning the impedance of the antenna. For achieving omnidirectional patterns of the horizontal polarisation, a series circular feeding network is designed to excite the loop antennas. The antenna is fabricated by copper and the circular network is printed on a substrate. Measurement results show the 10 dB return losses of the two ports are covering the whole 2.4 GHz WLAN band, with the isolation better than 20 dB. The gains vary <2.2 dB in the horizontal plane for both the polarisations. With the advantages of slim structure, lightweight, and easy fabrication, the proposed antenna is convenient to use in the WLAN routers.