An Ultra-Low-Cross-Polarization Horizontally Polarized Omnidirectional Antenna Using Strip-Line-Fed Structure

A horizontally polarized omnidirectional (HPO) antenna with ultra-low cross-polarization level (XPL) is presented for 2.4-GHz wireless local area network (WLAN) application. The proposed antenna is a double-layer strip-line-fed rotating dipole array, which consists of two layers of radiating element and one layer of feeding element. The radiating element is composed of four rotating dipoles and the feeding element is composed of four rotating baluns. The two radiating layers are symmetrically arranged with respect to the feeding layer. With the help of strip-line-fed structure, the HPO antenna achieves the ultra-low XPL property. A prototype of the proposed antenna is fabricated and measured. The antenna shows superior performance in HPO radiation and the measured XPL is lower than -54.8dB in E-plane and -55 dB in H-plane at 2.45 GHz. The measured -10 dB impedance bandwidth covers the 2400-2496 MHz. The proposed HPO antenna with ultra-low XPL is promising for WLAN communications, particularly in short-ranged point-to-point communication in high-security scenario.